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Various predictive models for the seismically-induced displacement (D) of flexible slopes during shallow crustal earthquakes are available in the literature, but the model-to-model difference of predictions remains unclear. This paper conducts a comprehensive comparative study of ten representative D models based on scenario- and probabilistic-based displacement analyses. Explicit expressions are provided to implement the probabilistic displacement hazard approach, in which copula theory is utilized for deriving the joint occurrence probability of ground-motion parameters. A total of 6048 displacement hazard analyses are performed considering different earthquake and slope scenarios. It is found that the model-to-model difference generally becomes larger with increasing the natural period (T s) of a sliding mass, whereas the within-type difference among different coupled models is notably smaller than that of the decoupled models. The coupled-type models generally result in smaller total variability of D as compared to the decoupled-type models. Meanwhile, the coupled models tend to, on average, yield larger (or smaller) hazard-consistent D than the decoupled models for T s larger (or smaller) than an intersection period T s,inter , though the difference between the two model types diminishes as T s approaches zero. The effects of ground-motion model selection and ground-motion parameter correlation are also discussed. This study could hopefully provide insights into the displacement model selection for the seismic slope performance assessment and regional landslide hazard mapping. • Comparative studies of ten slope displacement models are conducted. • Copula-assisted probabilistic displacement hazard procedures are presented. • Models yielding lower- and upper-bound displacement hazards are identified. • Relative difference between decoupled and coupled predictions is closely related to T s. • Within-type difference among coupled models is smaller compared to decoupled models. [ABSTRACT FROM AUTHOR]

Seismic fragility analysis is one probabilistic method that represents the conditional probabilities of exceeding different predetermined damage states for various given earthquake hazard levels, which is the essential part of probabilistic seismic risk assessment. It has gained much popularity recently because much more comprehensive and richer results than traditional probabilistic methods can be provided. The classical seismic fragility analysis of slopes is always performed through analytical approaches. In the present study, a novel seismic fragility analysis framework combined with shaking table model test results is proposed for probabilistic seismic performance and risk assessment of slopes. The shaking table model tests of a rock slope reinforced by pile-anchor structures were firstly performed subjected to a suite of real earthquake records with different intensity levels. Subsequently, the seismic responses from shaking table model tests were then gathered for the optimal analysis to determine the optimal engineering demand parameter (EDP) and earthquake intensity measure (IM) for seismic fragility analysis of slopes. At last, the identified most appropriate IM and EDP were selected to construct the scalar-valued fragility curves, vector-valued fragility surfaces and fragility surfaces considering acceleration elevation amplification effect by the proposed framework. The results indicate that using single IM to construct scalar-valued fragility functions may result in different failure probabilities depending on the chosen earthquake IM. The vector-valued fragility surfaces provide more information than ordinary fragility curves, and lead to more proper and realistic evaluations of seismic hazard of slopes. The methods and results presented in this paper also provide the basis for the probabilistic seismic risk and loss assessment of earthquake-induced slope geological disaster. • A novel seismic fragility analysis framework of slopes combined with the data from shaking table model tests is proposed. • The optimal EDP and earthquake IM for scalar- and vector-valued fragility analysis of slopes are identified. • The fragility surfaces of a slope considering acceleration elevation amplification effect are constructed. [ABSTRACT FROM AUTHOR]

In this study, an enhanced numerical manifold method (NMM) simulator is developed to determine the combined impacts of reinforcement range and grouting timing on the effectiveness of grouting reinforcement for preventing the large deformation geo-hazard during the tunnel excavation through a fault rupture zone. To accomplish this objective, the limitations of the current two-dimensional simulation method, which lacks connection to the actual tunnel excavation process, are overcome by proposing a novel softening path function. Using this novel softening path function, each simulation step is given a specific physical meaning, establishing a connection to the actual tunnel excavation process. This improvement enables more accurate and analyzable simulation outcomes. To verify the accuracy of the proposed softening path function, a series of simulations of tunnel excavation are conducted using this softening path function. These results align closely with the results obtained by other reliable numerical methods and previous studies. After validation, several sets of numerical cases are conducted, considering 6 different geo-stress conditions, 10 different grouting reinforcement ranges, and 7 different grouting timings. Based on these simulation results, a critical value for reinforcement range, which equals to the diameter of tunnel face, is identified, and it is founded that delaying the grouting timing can increase the slurry migration range up to 94.6%. Furthermore, delaying the grouting timing can also reduce the convergence displacement of reinforced surrounding rocks after excavation up to 18.2% within a geo-stress range of 10 to 20 MPa. • A novel softening path function with clear physical meanings for tunnel excavation simulations is proposed. • A critical value of the grouting reinforcement range is identified. • Influences of grouting timing on the slurry migration range are revealed. • Influences of grouting timing on the convergence displacement of tunnels are revealed. [ABSTRACT FROM AUTHOR]

The low frequency of large destructive earthquakes in the Eastern Betics (SE Iberian Peninsula), not recorded in the instrumental seismic catalog, complicate the estimation of the maximum ground motion that could be reached. Knowing the characteristics and behavior of these large seismic ruptures is crucial for the study of seismic hazard. In this work, we have used a physics-based earthquake simulator to generate a 100 kyr catalog of seismic ruptures associated with seismogenic faults bordering the quaternary Guadalentin and Bajo Segura basins. From these ruptures, we have selected maximum earthquake scenarios, and those associated with certain probabilities of exceeding a severe magnitude from the synthetic catalog. The estimation of maximum peak accelerations (PGA) by means of ground motion prediction equations include a possible site amplification that we have calculated from a detailed geotechnical classification of soils. According to the simulations, the modeled faults have the capacity to generate maximum earthquakes with magnitudes ranging M W 6.7–7.4. Densely populated urban areas located along the Guadalentin valley, such as Lorca, could be subject to site-dependent PGA values close to 0.6 g on the Alhama de Murcia fault trace. Similar ground motion would affect the coastline of SE Alicante province when evaluating the maximum simulated event in the Bajo Segura offshore fault. But already from magnitudes around M W ∼ 6, PGA estimations exceed critical values of 0.5 g at the south side of the Bajo Segura basin and the city of Murcia, highly dependent of ground-motion amplification induced by thick deposits of very soft and saturated soils. Our scenarios reflect that other factors such as fault geometry, kinematics and the capability observed in the simulations to generate multi-fault ruptures also affect the spatial distribution of maximum ground motion in this region. We expect that this evaluation could contribute as an improvement guideline for future strong motion prediction studies prior to the settlement of new urban infrastructures in the Eastern Betics. • Physics-based simulations for a long-term catalog of large complex seismic ruptures. • Deterministic analysis of ground motion scenarios at the Eastern Betics. • Geotechnical classification of soils to include site amplification in hazard analysis. • Big earthquakes and soft soils may rise seismic threat in populated zones of SE Spain. [ABSTRACT FROM AUTHOR]

Numerous interbedded rock (IR) slopes fail during the Wenchuan earthquake in the mountainous region of western China. Landslides are also triggered in IR slopes with a 60° layer inclination, which are generally stable in gravity-dominant environments. This study examines the effect of seismic motion on the response characteristics and failure patterns of IR slopes with steep layers to develop a landslide hazard assessment tool for earthquake-prone regions. First, we use a centrifuge shaking table test to model the failure process and acceleration responses of two IR slope models with stratigraphic dips of 60° and 80°, respectively, under different seismic intensities. Next, we adopt the Particle Flow Code to examine the crack propagation features and peak ground acceleration amplification effects for the IR slopes. We find that the seismic failure pattern of IR slopes depends largely on rock layer inclination: buckling failure is triggered when rock layers are parallel or nearly parallel to the slope surface, while toppling failure is triggered when the rock layer inclination is significantly higher than that of the slope surface. Following seismic excitation, the damage is mainly observed in the weak rock layers, creating lateral stress on adjacent strong rocks, which undergoes deformation and ultimate macroscopic failure. Further, displacement of the IR slope is negatively correlated to rock layer inclination. Rock layer thickness has a major influence on the damaged area inside the slope mass, while rock layer stiffness mainly affects the deformation distribution near the slope shoulder. • Interbedded slopes with steep layers under earthquake exhibit buckling or toppling. • Using centrifugal shaking table test to reproduce interbedded rock slope failures. • Non-uniform deformation is highly developed in interbedded slopes. • Rock layer inclination is a significant factor on failure type in interbedded slopes. [ABSTRACT FROM AUTHOR]

This paper presents the development of a shear-wave velocity (V S) model of reference site conditions in South Carolina for site response analysis and seismic hazard mapping. Model development involves creating contour maps of two geologic surfaces in the Coastal Plain with high contrasts in V S and combining the results with median V S profiles that extend to hard rock (V S ≥ 3000 m/s). Uncertainties associated with the contour maps of depth are captured in maps of the standard prediction error. Values of time-averaged V S in the top 30 m (V S,30) ranging from 1183 to 1538 m/s and 354 to 385 m/s characterize the reference site conditions in the Blue Ridge and Piedmont regions and the Coastal Plain region, respectively. The model is divided into 14 zones to facilitate site response analysis and to avoid over-smoothing resonances due to the impedance contrasts. This study is part of a larger effort to develop statewide probabilistic seismic hazard maps for the South Carolina Department of Transportation. • A geology-based, shear-wave velocity (V S) model of reference site conditions in South Carolina is developed. • Two depth contour maps are created: 1) Top of the Jurassic and older basement; and 2) Bottom of the Santee Limestone. • V S30 for reference outcrop site conditions are between 354 m/s and 385 m/s in Coastal Plain of South Carolina. • In the South Carolina Blue Ridge and Piedmont, V S30 for reference outcrop site conditions range from 1183 to 1518 m/s. • South Carolina is divided into 14 zones for the purposes of site response analysis. [ABSTRACT FROM AUTHOR]

Abstract The 2008 Wenchuan earthquake in Sichuan, China, dramatically changed the terrain surface by inducing large numbers of landslides. Due to the lack of adequate pre- and post-earthquake Digital Elevation Models, the landslide volume estimation was done either using empirical area-volume relationships over large areas or by field surveys in a few catchments with debris flow threats. The trend of the change of volume of loose materials in the earthquake affected area over the decade since the earthquake remains largely unknown. In this study we were able to address this issue using nine DEMs taken at different years and from different sensors to study the change in loose material volume caused by co-seismic and post-seismic landslides over a period of 9 years. The area around the towns of Yingxiu and Longchi, for which also multi-temporal landslide inventories were available, was selected for this study. Methods to register the DEMs and minimize their vertically bias were applied. The quality of the DEMs was assessed through GCPs and terrain representation. As could be expected, high resolution DEMs showed more realistic volume estimates than the low resolution ones. The analysis showed that the frequency and magnitude of the landslide volume dynamics decreases significantly after the early post-seismic period, and in the last years human activities became a more dominate factor than mass movements. The post-seismic material loss from 2008 to 2014 was close to the gained volume of the co-seismic landslides, and the depletion of the materials was mostly at the toes of the co-seismic landslides. The analysis was done based on gain and loss calculated from the DEMs, and actual volumes could not be calculated due to unknown failure surface depths of the landslides. Highlights • This research shows the potential and problems of multi-temporal DEM analysis in a post-earthquake environment. • Methods to register DEMs were presented. • The analysis showed that the landslide volume decreased significantly in the first 6 years after the earthquake. • In the early post-seismic stage the elevation changes were majorly caused by mass movement while in the later years human activity became a dominate factor [ABSTRACT FROM AUTHOR]

Abstract Grid-based approach is typically adopted to estimate the Newmark-type displacement for regional seismic landslide hazard assessment. However, the approach is limited to the assumption of infinite slope and rigid block movement, which may be different from the actual behavior of slope under seismic loading. In this study, a slope unit-based approach is proposed to quickly estimate earthquake-induced displacements for finite slopes in regional scale. Hence, regional seismic landslide hazard can be assessed by the estimated displacements. The approach is advantageous as it considers slope geometry, determines the failure mode automatically, and considers the interaction of incident wave and slope. The implementation of the approach is demonstrated by considering two areas that experience severe landslides during the Chi-Chi and Northridge earthquakes. Results show that the prediction rate of the proposed method is up to 73% compared with the landslide inventory given the estimated displacements. Highlights • A slope unit-based approach is proposed to assess regional seismic landslide hazard. • Slope geometry, failure mode, and interaction of incident wave and slope are considered. • The approach is demonstrated by two areas that experience severe landslides during the Chi-Chi and Northridge earthquakes. • The prediction rate of the proposed method is up to 73% compared with the landslide inventory. [ABSTRACT FROM AUTHOR]

Abstract The 2016 Kumamoto earthquake, which occurred in the central Kyushu region of Southwest Japan, caused numerous landslides. Mass movements from the events damaged many structures in the Minami-aso village residential areas. We conducted geological and geophysical surveys and monitoring of landslides in one of these residential areas. It was found that the landslide occurred directly adjacent to the earthquake's main surface fault-ruptures. While the landslide slip surface formed within a layer of hydrothermally altered rhyolite at about 15 m depth for the downslope side, the slip surface for the upslope side formed within intact tephra layers due to the shallow dip of the rhyolite layer. Geophysical survey results show that fault ruptures in the tephra layers along with the tectonic faulting induce a decrease in soil strength. It was inferred that the landslide head scarp and upper slip surface formed inside this weak soil. Long-term monitoring of the landslide demonstrated that deformation continued for at least four months after the main slide. Although the initial and the major slide was activated by the earthquake, the landslide did not immediately stabilize and continued to pose risks after the main event. Toward the mitigation for earthquake-induced landslides, post seismic monitoring as well as the relationship between surface fault traces and landslide blocks should be taken into consideration. Highlights • An earthquake-induced landslide was surveyed using geological and geophysical methods. • The landslide occurred adjacent to surface rupture with tectonic displacements. • Part of the slip surface formed in hydrothermally altered rhyolite. • The landslide remained in an unstable state for several months after the main slide. [ABSTRACT FROM AUTHOR]

Abstract Through a review of selected published case study data from around the world, in situ conditions that contribute to rockburst events have been identified. This review was carried out to assist research associated with developing numerical modelling techniques to reproduce rockbursting within a large-scale (mine models) for predictive purposes. Contributing factors identified through the case study review include unfavourable stress states, excavation geometry (size and orientation in relation to the principal stresses) and rate and direction of advance. Factors also incorporated unfavourable rock mass characteristics that included mineralogy, contrasts in geomechanical properties, and geological intensifiers (dykes, faults, etc.). Highlights Key contributing factors to rockburst events are: • Loading Associated: ○High and/or adversely re-oriented stresses by structures ○Excavation geometry ○Excavation rate and direction • Property Associated: ○Mineralogical properties ○Contrasting geomechanical properties ○Geological intensifiers affecting fracturing behaviour. [ABSTRACT FROM AUTHOR]

During the last years, several crustal seismic sources have been proposed in El Salvador; however, the actual destructive potential of these proposals has not been revealed yet. Here we present several seismic scenarios related with the main crustal faults in the country. We have characterized the corresponding hazard scenarios in a deterministic way, estimating the peak ground accelerations (PGA) including local site effects. In addition, we present a list of 29 sources that can be considered potentially dangerous with their main features when they are available and four seismic scenarios that we consider to be more probable. We have resorted to the February 13th 2001 Mw 6.6 destructive earthquake, the only earthquake occurred in a known crustal source in El Salvador and recorded by the strong motion network, in order to test the methodological approach and the reliability of the PGA results predicted by two available Ground Motion Prediction Equations (GMPEs) including the site effect. The consistence between the values given by the models and the ones recorded during the event provides reliability to our results. This approach allowed us to conclude that faults within the volcanic arc can produce accelerations up to 1 g in the most conservator case (Mw = 7.0), while accelerations up to 0.6 g are usual results related with specific faults within the Salvadoran Volcanic Arc. Besides, the reported damage distribution of the 8th June 1917 earthquakes and its similarity with one of the proposed scenarios allowed us to infer the possible source of this event, the Guaycume Fault. [ABSTRACT FROM AUTHOR]

Seismic hazard maps for Alborz region (north of Iran) and adjacent areas are prepared using the neo-deterministic seismic hazard assessment (NDSHA) based on the computation of synthetic seismograms at the regional scale. The study area is zoned according to different geophysical structural models delimited at the surface by polygons, used to define the mechanical properties of the source-site paths. We have refined the velocity structures of Iran, as obtained from surface waves tomography, to obtain the velocity structure of Alborz region by applying the joint inversion of the P-wave receiver functions (PRF) and surface wave's dispersion. The input data set consists of attenuation-velocity structural models (representing bedrock conditions), seismogenic zones, focal mechanisms and the catalog of past seismicity. The seismic hazard, expressed in terms of maximum displacement (PGD), maximum velocity (PGV) and design ground acceleration (DGA), is extracted from the synthetic seismograms and mapped on a regular grid of 0.2° × 0.2° over the entire region. The results of this first order NDSHA zoning indicate a high seismic hazard in the Alborz region and may represent an important knowledge basis towards detailed and comprehensive seismic microzonation studies. [ABSTRACT FROM AUTHOR]

The 28th September 2018 Sulawesi Supershear earthquake (M W 7.5) was one of the deadliest earthquakes in the recent history of Indonesia causing ∼4000 causalities. The earthquake caused a ∼ 177 km long surface rupture along the Palu-Karo fault. Apart from surface rupture, the earthquake caused extensive earthquake environmental effects (EEEs) around the Palu-Donggala area of Central Sulawesi, Indonesia, which includes tsunami, coastal landslide, liquefaction, ground cracks and more than 7300 landslides in hilly areas. Initial post-event analysis and reports assigned a Modified Mercalli Intensity (MMI) of VII to VIII in Palu City and the surrounding area. Building damage and ground effects caused by the earthquake suggested that seismic intensity was understated. Here we applied the EEEs information from field survey data, published reports, and remote sensing tools to determine macroseismic intensity using the Environmental Seismic Intensity (ESI-07) Scale. The ESI-07 intensity derived from the ground effects suggests the maximum intensity of X-XI, which is 3–4° higher than the traditional intensity estimated by the United States Geological Survey (USGS) and the Indonesian Agency for Meteorology, Climatology, and Geophysics (BMKG). ShakeMaps were generated considering the ESI-07 values. The ShakeMap was compared with the instrumentally derived ShakeMap for the Palu earthquake, which proves that the ShakeMap prepared from the instrumental data or structural damage data is underrated. We argue that proper documentation of the EEEs is necessary for such damaging earthquakes for future earthquake hazard mapping and planning in the study area and other earthquakes in Indonesia. In addition, this will help in defining the on-fault and off-fault damage zone towards reducing the seismic risk of the Palu Donggala area. • Detailed Earthquake Environmental Effects (EEEs) caused by the 28/09/2018 Sulawesi earthquake (M w 7.5) were collected. • The epicentral ESI-07 intensity as well as the site specific intensity were estimated. • The ESI-07 intensity were compared with Skala Intensitas Gempabhumi (SIG), BMKG. • ESI-07 ShakeMap were generated using the Surface Rupture data and ESI-07 values. • The maps can be used to guide efficient and strategic seismic hazard assessment and land use planning. [ABSTRACT FROM AUTHOR]

Accurate V S30 estimates are increasingly important in seismically active areas due to their efficacy in site effect analysis for seismic hazard assessment as well as microzonation evaluation and shake maps development. A comparison between different approaches for the time-averaged shear-wave velocity (V S ) in the upper 30 m (V S30 ) is presented. In this study of V S30 a site-to-site or averaged zonation value technique comparison is assessed for proxy-based and measured or assigned values, respectively. Three urban areas of Edessa, Grevena and Xanthi in Northern Greece were selected for this study. The merit of this selection was based on the historical seismicity, geology and geomorphology of these areas. This paper highlights the strong correlation between the proxy-based approach and the assigned average values in zones of common geophysical and geotechnical characteristics within the frame of EC8 site characterization. In addition, on site-by-site comparison proxy-based V S30 values, agree with the ones derived from measured geophysical data. With the exception of areas where shear wave velocity has a high rate increase with depth, as well as, in shallow bedrock above 30 m the proxy tends to underestimate the V S30 value. Higher disagreements are reported when stiffer formations are denoted through geotechnical mapping that are not clarified in the geological map. [ABSTRACT FROM AUTHOR]

The paper reports on the results of 1D and 2D site response analyses carried out in the Kathmandu Valley, Nepal, in order to investigate how site effects influenced the seismic response during the 2015 Mw 7.8 Gorkha earthquake sequence. The mainshock and a Mw 6.6 aftershock, for which recordings at both rock and soil sites are available, were considered. First, 1D analyses were carried out for the Pulchowk soft soil site, where a borehole was drilled. The shear wave velocity profile was defined using several 2D seismic array surveys carried out in the valley and constrained by noise measurements at Pulchowk site; the nonlinear soil behavior was characterized by means of cyclic simple shear tests carried out on undisturbed soil samples. Both equivalent and nonlinear approaches were adopted in the 1D analyses. Overall, the 1D model was capable to capture some relevant features shown by mainshock recordings such as the de-amplification of medium-to-high frequencies. On the contrary, the unusual high spectral amplification at long periods (3–6 s) recorded during the mainshock was better captured by the 2D finite element analyses carried out on a 20 km-large cross section of the entire valley, thus supporting the hypothesis of the occurrence of basin effects. The paper contributes to the understanding of site effects in Kathmandu Valley for the implementation of seismic risk mitigation strategies in the area. [ABSTRACT FROM AUTHOR]

The Xinmo landslide slope in Sichuan, China, was stable during the intensive Wenchuan Earthquake in 2008 but failed on June 24, 2017. Landslide debris buried Xinmo Village and blocked the Songpinggou River at the slope toe. This study aims to clarify the post-failure behavior of the landslide using two-dimensional discontinuous deformation analysis (2D DDA). The simulation results provide comprehensive information on the initiation and the evolution of the landslide. The failure process determined by the DDA correlates well with the seismic signal analysis results. In addition, the location of the calculated rock deposit is similar to that shown by the topographic map after the landslide. The maximum rock velocity in the landslide is 65.4 m/s. Therefore, the impacts of the high-velocity blocks and the buildings in Xinmo Village must be considered to simulate the burial of Xinmo Village by rocks and the transport of additional rocks across the Songpinggou River. This Xinmo landslide study demonstrates that the DDA accurately simulates the post-failure behavior and determines the impact area of a landslide with complicated failure processes and topography. [ABSTRACT FROM AUTHOR]

The Newmark sliding block model is widely used in the evaluation of seismic slope stability. When using this model, the horizontal acceleration is usually considered to act parallel to the slope (downslope), and the vertical component of ground motions is commonly ignored. This study investigates the effect of vertical accelerations on the results of sliding displacement, and quantitatively compares the difference of the displacement D N calculated from the original Newmark's approach with the displacement D HV calculated from a more realistic case (horizontal and vertical accelerations properly considered). For this purpose, 4136 ground motion recordings are selected from the NGA-West2 database, and >2000 hypothetic slopes are simulated with critical accelerations a c ranging from 0 to 0.8 g. Comparison of D HV and D H shows that the incorporation of vertical accelerations only slightly increases the displacement. Besides, the calculated D HV / D N ratios are generally in the range of 1 to 5, indicating that D N significantly underestimates the slope displacement due to the simplification of seismic excitations. The D HV / D N ratios generally increase as a c increases. Simple predictive models are proposed to quantify the correction factor K D ( K D  =  D HV / D N ). They can be easily used in seismic landslide hazard assessment to improve the performance of the original Newmark's approach. [ABSTRACT FROM AUTHOR]

In recent years public concern about earthquakes induced by gas production has increased in the Netherlands. This has mainly been caused by numerous seismic events related to gas depletion in the Groningen gas field, the largest gas field in Western Europe. Induced seismicity has also been observed in 31 smaller gas fields located on land (onshore) or in the area close to the Dutch coast. Earthquakes with magnitudes as high as M L  = 3.5 have occurred in Roswinkel and Bergermeer causing damage to buildings. In 2016 State Supervision of Mines (SSM), with input from the geological survey of the Netherlands (TNO) and the onshore operators, proposed a guideline for a qualitative seismic risk analysis for depletion induced seismicity arising from gas production in the small fields in the Netherlands. The guideline follows international practices for risk assessment using a risk matrix approach. This paper elaborates the seismic risk guideline and reports on the application of the guideline to the gas fields in the Netherlands. Risk is a combination of hazard and consequences. The result of the seismic risk analysis is qualitative and gives a relative scoring of the producing gas fields in the Netherlands in terms of risk. In order to obtain more information on the quantitative assessment of the risk, more detailed studies are needed. The Groningen gas field clearly poses a much larger seismic risk than that obtained for the other, smaller gas fields, most of which fall into the lowest risk category. Because of the large difference in risk between the Groningen field and the other smaller gas fields, the guideline of SodM deems it sufficient to carry out a qualitative risk analysis for the other gas fields in the Netherlands, as performed in this paper. Based on the combination of the hazards and consequences, the risk can be further interpreted and, if necessary, appropriate measures can be implemented. [ABSTRACT FROM AUTHOR]

Regional active tectonics and historical earthquake records indicate the importance of the triggering effects of historical strong earthquakes on groups of large-scale landslide occurrences in the Wei River midstream section. In this study, a method to assess the triggering effects of historical earthquakes on regional large-scale landslides is presented. The greatest epicentral distances of seismically induced landslides were calculated. The triggering effects of four key historical strong earthquakes with epicenters within 300 km of the Wei River midstream section were analyzed; these are the M s 7.0 Qishan earthquake of 780 BCE, the M s 8.0 Tianshui earthquake of 1654 CE, the M s 8.25 Huaxian earthquake of 1556 CE, and the M s 8.5 Haiyuan earthquake of 1920 CE. Taking the Qishan earthquake as an example, a seismically induced landslide displacement and hazard assessment method based on the Newmark displacement model was developed. The degree of spatial matching of the results for historical-earthquake-triggered landslides and the distribution of actual large-scale landslide deposits were compared quantitatively using the success rate curve method. The results show that of the four historical earthquakes, the Tianshui earthquake had the strongest effect of inducing large-scale landslides regionally along the Wei River midstream section. [ABSTRACT FROM AUTHOR]

The paper discusses the field investigations, geotechnical characterization and time evolution of horizontal displacements in a wide landslide. The latter, triggered by an earthquake occurring in September 2002, is located in Sicily and involves a thick body of stiff and highly fissured clays belonging to a Varicoloured Clay formation. In order to characterise the reactivation of landslide mechanisms induced by rainfall, a three-year monitoring programme (2008–2011) was implemented to measure rain, pore water pressures, and deep and superficial displacements. The monitoring data made it possible to recognize three distinct landslides, which evolve at variable rates in different directions, within the overall landslide area. The landslides were reactivated by the increase in pore water pressures in the period autumn 2009–spring 2010. The data clearly show the mechanical role of pore water pressures in the stability of the slope and point out the dependence of the time evolution of the horizontal displacement on the pore water pressure variation induced by rainfall. Back-analysis carried out on the single landslides confirmed that they are reactivated ones since the residual shear strength is mobilised on the pre-existing sliding surfaces. The pore water pressure variation and the landslide body displacement rates can be effectively related to 5-month cumulative rainfall by simple models, characterised by three parameters. These models, calibrated on the period October 2009–September 2010, made it possible to predict the horizontal displacement rates in the ensuing time period. The displacements forecasted by the model in the period September 2010–May 2011 agree very well with the measured ones. [ABSTRACT FROM AUTHOR]

On 17 November 2016, an unexpected slope failure occurred in an undisclosed copper open-pit mine. The nature of the event urged for a thorough back-analysis of slope monitoring data in order to assess its size and temporal evolution, and to determine whether precursors potentially able to anticipate the failure were present. To this aim, satellite InSAR data spanning over the final 9 months before the event were, in retrospect, acquired and coupled with measurements from a ground-based radar that was in use at the time of the failure. Although progressive deformation was detected by the ground-based radar in correspondence of the two uppermost benches in the pit, the satellite InSAR data revealed that the vast majority of the instability actually involved a large part of natural slope above the mine crest. This sector was not visible by the ground-based radar. Thanks to the short revisit time of the Sentinel-1 mission, clear slope accelerating creep was observed for the first time in satellite InSAR measurements over an open-pit mine. The delimitation of the area featuring accelerating creep behavior matched remarkably the source area of the failure as mapped in the field after the event. Considerations on the volume of the instability and on the development of the failure process (both in space and time) were consequently derived. The results provided a clear example of the value of jointly using ground-based and satellite interferometry to reduce the uncertainties inherent to the identification and characterization of impending catastrophic slope failures. [ABSTRACT FROM AUTHOR]

Landslide characterization and hazard assessments require multidisciplinary approaches that connect geologic processes with geotechnical parameters. Preexisting landslide activity, geology and geomorphology, soil strength, and hydrologic conditions are complex factors that affect landslide behavior. Often, the connections among these factors are not made for hazard assessments, forecasting, or slope stability modeling. Therefore, geophysical and geotechnical techniques for landslide investigations are typically assessed independently. This study aims to bring together different techniques to develop a methodology that connects electrical measurements and shear strength. A framework has been developed for using electrical resistivity measurements that will support and facilitate the prediction of shear strength within a slope. In-situ volumetric water content, soil-water potential (suction), and electrical conductivity were measured from two shallow colluvial landslides in Kentucky. Repeated surface electrical resistivity survey measurements were used to characterize the failure zone and lithology, and to compare with the in-situ hydrologic measurements. The data show that subsurface moisture conditions over time can be reflected in the inversions of repeated ER surveys, thus allowing electrical measurements and geotechnical parameters to be correlated. This study demonstrates that electrical resistivity can be used as a tool for landslide monitoring and to assess shear strength. These parameters are pertinent to investigating the stability of landslides that are often triggered or reactivated by rainfall. [ABSTRACT FROM AUTHOR]

Alpine glaciers and permafrost are sensitive to climate change, and their degradation due to annual temperature increasing has already induced many mass movements such as debris flows. On September 4 of 2007, July 25–31 and September 5–8 of 2010, three large debris flows took place in Tianmo gully, a left-bank tributary of Parlung River, southeast Tibetan Plateau. The debris flows blocked the river, and a section of highway 450 m long including a bridge 76 m long were destroyed by the subsequent outburst flood. This paper, based on post-event investigations, witness accounts, news reports and satellite image interpretation, systematically analyses the geo-environments, climate conditions and sources of these debris flow events. Their differences in flow process, surge numbers and velocity suggest that they resulted from different geohazard processes, cascades and initiation mechanisms. The 2007 debris flow originated from a bare rock/moraine collapse next to the cirque due to strong alternation of wet and dry conditions. The mass moved down the gully with velocity of 30–40 m/s estimated by back-calculation using superelevation and run-up. It entrained moraine, avalanched snow-ice and water from the channel, and transformed into high-speed debris flow, crossing the Parlung River and finally depositing onto the highway. The other two events in July and September of 2010 initiated from two channel-bank landslides triggered by melt-water and concentrated rainfall, which dammed the channel. The subsequent landslide dam failure generated debris flows over several days, with velocities of 12–14 m/s, that temporally blocked Parlung River. The initiation mechanisms of most large debris flows recorded in Parlung region are similar to the events in Tianmo gully, originating either from rock/moraine avalanches or from the collapse of a landslide dam. This implies that the periglacial degradation of bedrock and moraine is the key process to be monitored and assessed under climate warming. The paper applies the geohazard mechanisms and cascade to hazard monitoring in order to protect the existing Sichuan-Tibet highway and the forthcoming railway. [ABSTRACT FROM AUTHOR]

The Mejillones Peninsula, located in northern Chile, represents a site of interest for seismic hazards assessment due to ~ 100-year seismic gap, the potentially large site effects, and the presence of the most important port in the region. In addition, the western edge of the Pampa Mejillones is limited by the Mejillones Fault, which controls the development of the Mejillones Basin to the east. In this research, we created a dynamic characterization of the northern portion of the basin using an integrated modeling of geophysics observations. These observations were: gravimetric method, magneto-telluric method (MT) and multichannel analysis of surface waves. The results of the geophysical campaign show soil thicknesses up to 750 m on the deeper zone with steeper slopes to the west and lower slopes to the east, in agreement with the normal-fault half-graben basin geometry. The sedimentary stratum is characterized by shear velocities between 300 and 700 m/s, extremely low electrical resistivities (below 1 Ω-m) and densities from 1.4 to 1.8 g/cm 3 . The integrated interpretation allowed us to generate a spatial and petrophysical model of the Mejillones Basin, from which we studied the seismic behavior of the zone. Preliminary results of the dynamic site amplification (using the Spectral Element Method) show peak ground accelerations (PGA) of almost 100% higher than the solicitation and stronger basin-edge effects. In this work, we demonstrate that the presented methodology (integrated geophysical characterization and numerical simulation) can be applied to characterize any deep forearc basin to quantify their seismic response in order to assess their seismic hazard. [ABSTRACT FROM AUTHOR]

Mining seismicity is routinely observed to cluster in space and time due to the spatially distinct rock mass failure processes associated with the temporally dependent process of mining. Assessment of clustered seismicity is important to develop an understanding of and to quantify seismic hazard that is associated with mining. This article presents a density-based clustering method that is applicable to the assessment of 3D spatial distributions of short-term seismicity. The methodology presented in this article is developed from existing approaches that address the general limitations of density-based clustering algorithms. Synthetically generated seismicity allows for the assessment of the methodology with respect to external and internal performance measures. The clustering of a dataset with known attributes allows for confidence to be developed in the capability of the clustering method. Additionally, this internal performance evaluation can represent the relative accuracy of outcomes without prior information concerning dataset attributes. The clustering method is applied to two case studies of mining seismicity. These cases illustrate the general applicability of the clustering method along with the value of evaluating internal performance measures when optimising the selection of parameters and understanding the sensitivity of clustering outcomes to these choices. [ABSTRACT FROM AUTHOR]

Earthquake-induced soil liquefaction can cause enormous life and economic losses. The joint distribution of the peak ground surface acceleration ( a max ) and the moment magnitude of an earthquake ( M w ) is crucial to the estimation of soil liquefaction-related hazards. In this paper, a new method is suggested to estimate the joint distribution of a max and M w . Compared with the existing method, the suggested method is easier to implement, and depends on fewer assumptions. The derived joint distribution is then used to assess the damage state of a building caused by soil liquefaction during a given exposure time. The method is illustrated with an example in which a reinforced concrete frame building is assumed to be at different locations and is subjected to different exposure time. It is found that, as the exposure time increases, the chance of higher degree of damage also increases. When the exposure time is the same, the damage state of the building may also be different when it is at different locations. The method suggested in this paper can be used to quantify the effect of ground condition as well as the seismic effects at a site on the damage state of a building, thus providing a more transparent understanding of the risk associated with the soil liquefaction hazard on structural damage. [ABSTRACT FROM AUTHOR]

In recent years, many have mapped the liquefaction potential index (LPI) to describe the liquefaction hazard at regional scale. Several investigators have calibrated the LPI to field observations of liquefaction-induced ground failure after a number of major earthquakes; the significance of LPI values and their correlation with the severity of liquefaction-induced ground failure can vary greatly depending on the calibration. In this study, the LPI was computed at more than 1200 cone penetration test soundings across the Christchurch area, New Zealand, using peak ground accelerations from the 2011 Christchurch Earthquake. Based on detailed field observations of liquefaction-induced ground failure after the earthquake, it was shown that the LPI has potential for discriminating between areas with no liquefaction-induced ground failure hazard and areas that may experience liquefaction-induced ground oscillations and settlement; however, the LPI performed poorly at sites where severe ground failures occurred, especially at sites that experienced lateral spreading. As many researchers have found a positive correlation between lateral spreading and the proximity and depth of a nearby free-face (i.e., a steep topographic depression, river channel, etc.), a new LPI framework was proposed that includes a parameter named the free-face ratio ( FFR ). FFR was shown to have a significant correlation with field observations of lateral spreading in Christchurch. It was shown that by incorporating FFR into the LPI framework, modified LPI values are positively correlated with the severity of field observations of liquefaction-induced ground failure in Christchurch. It was also shown that maps can be produced based on LPI and FFR , and such maps rarely underpredict the liquefaction-induced ground failure hazard, unlike maps based on the unmodified LPI. [ABSTRACT FROM AUTHOR]

The aim of this study is to associate the expected ground motions from Neo-Deterministic Seismic Hazard Assessment (NDSHA) to robust estimates of their long-term average occurrence rates. NDSHA means scenario-based methods for seismic hazard analysis, where realistic and duly validated synthetic time series, accounting for source, propagation, and site effects, are used to construct ground motion scenarios. NDSHA, in its standard form, defines the hazard as the envelope ground shaking at the site, namely the maximum estimate computed from a large set of possible scenario earthquakes. Thus, the standard NDSHA maps provide rather robust and conservative hazard estimates, which do not require any assumption about the probabilistic model of earthquakes occurrence. Some specific applications, however, may benefit from temporal information about the computed ground shaking, including a gross estimate of its average recurrence time. For this purpose, the definition of the Frequency-Magnitude (FM) relation for earthquakes in the Italian region is performed according to the multi-scale seismicity model and an occurrence rate estimate is associated to each of the modeled sources. The introduction of occurrence rate estimates in NDSHA also allows for the generation of ground shaking maps for specified time intervals (often improperly referred as “return periods”) that permit a straightforward comparison between the NDSHA and the PSHA maps. [ABSTRACT FROM AUTHOR]

Seismic landslide hazard assessment is typically based on deterministic analysis to calculate slope displacements during an earthquake. However, deterministic analysis is unable to account for various uncertainties in the analysis process. This study focuses on utilizing the established results from probabilistic seismic hazard analysis (PSHA) and extending probabilistic seismic landslide hazard analysis (PSLHA) to account for the uncertainties of ground motions and soil strengths. Two simplified methods, being flexible and fast, are proposed and evaluated by comparing with the fully but complex probabilistic method. One of the methods that yields a better performance is applied to evaluate the probabilistic seismic landslide hazard in the Tsao-Ling area of Taiwan using information regarding the seismic hazard curve and it's deaggregation results. Lastly, seismic landslide hazard maps are constructed for different return periods and compared with the deterministic map for the 1999 Chi-Chi earthquake. • Simple method for probabilistic seismic landslide hazard analysis is proposed. • The method incorporates uncertainty of ground motions and strength parameters. • The method only requires a probabilistic seismic hazard curve and its deaggregation. • The method is validated with the full but complex probabilistic method. • The method is demonstrated by applying it to the Tsao-Ling area of Taiwan. [ABSTRACT FROM AUTHOR]

In this paper we present the ground response analyses (GRA) of a site where an industrial facility is planned. Due to its location on an active normal fault system known as a relevant seismic gap, the Mt. Morrone Fault system (MMF), and at the edge of a basin filled with slow velocity continental deposits, a inter-disciplinary and non-standard approach has been applied to assess the seismic input of the dynamic numerical analyses. It includes geological, seismological, geotechnical and engineering contributions. Two fault scenarios, MMF1 and MMF2, were considered and scenario-based (SSHA) and probabilistic (time-dependent, TD, and time-independent, TI) seismic hazard (PSHA) analyses were implemented. Comparison among the spectra corresponding to the 90th percentile of the SSHA statistical distribution and the PSHA average ones shows that the SSHA MMF2 has values similar to the PSHA TD model. The SSHA 90th percentile distribution was selected as target spectra to retrieve the seismic input for GRA. Nonlinear numerical simulations of seismic wave propagation were implemented to derive surface ground motion parameters. GRA acceleration response spectra and their PGA are notably higher, and thus on the side of safety, than those obtained following the Italian code approach for seismic resistant buildings. These results confirm that a scenario-based methodology can better capture the shaking effect in near-field conditions, avoiding possibly unconservative underestimations of the seismic actions and in view of a more robust performance-based approach used by engineers for either new design and/or assessment/retrofit purposes of the built environment. • A site-specific surface ground motion analyses of a near-fault industrial site using a interdisciplinary methodology. • Similarity of response spectra for deterministic scenario-based and probabilistic time dependent seismic hazard analyses at the bedrock. • The seismic input at the bedrock from the fault scenarios, is more severe than the values predicted by the seismic resistant code for a rock site. • A fully nonlinear modeling is more appropriate than an equivalent linear one due to the high strain level induced by the scenario seismic input. [ABSTRACT FROM AUTHOR]

An updated probabilistic seismic hazard analysis in terms of peak ground acceleration and spectral acceleration values, for B, B/C, and C NEHRP site classes, for a 5% and 10% probability of exceedance in 50 years, has been conducted for Western Mexico. To achieve this assessment, a unified and updated declustered earthquake catalog (1787–2019), as well as an updated focal mechanism database (1963–2016), was compiled, prepared, and processed specifically for this work. Two alternative source models (area sources and a spatially smoothed seismicity model) were considered in the assessment, within a logic tree scheme. A characteristic earthquake model has been also implemented for some of the defined sources. The designed logic tree has additionally included other parameters: the possible uncertainty related to the Gutenberg-Richter b -value way of estimation, the maximum expected magnitude value, as well as two-alternative GMPEs selected for the subduction seismic sources. The obtained ground-motion results have been presented as seismic hazard isoacceleration maps, as well as uniform hazard spectra and hazard curves for 15 selected cities, for the three considered site conditions. A comparison between the obtained hazard values and the current seismic design regulations, as well as previous studies, has been also performed, and a new design response spectrum has been proposed. Finally, some regression fitting relationships between the obtained ground-motion values have been achieved. Concerning the most significant results, it is worth noting that the southwestern coast (in the perimeter of the Middle America Trench of the Mexican Subduction Zone) presents the highest hazard values. For instance, the cities of Apatzingán, Autlán, Colima, Lázaro Cárdenas, and Manzanillo exhibit the largest observed PGA values among all the studied cities. Our approach and results are supported by the fact that the recent September 19, 2022, Mw 7.6 earthquake has been located in this highest seismic hazard area. • This work provides an updated seismic hazard assessment for Western Mexico. • Seismic hazard was computed for three different site conditions (B, B/C, and C NEHRP classes). • Two alternative source models, including a spatially smoothed model, in a designed logic-tree framework, were used. • Isoacceleration maps, hazard curves, and uniform hazard spectra have been computed for the most important cities. • Recent 2022-09-19, Mw 7.6, and 2022-09-22, Mw 6.8, SSW of Aguililla, earthquakes, occurred where higher hazard values have been computed. [ABSTRACT FROM AUTHOR]

In some geological settings, such as thick sedimentary basins, the deeper layers may also significantly contribute to the amplification of the ground motion during an earthquake, particularly at low frequencies. To properly quantify the influence of the deeper geology on the seismic ground motion at the surface, the use of indirect geophysical exploration techniques is particularly suitable, as it can produce realistic representations of the subsoil structure over a large range of depths. This paper focuses on the acquisition and processing of combined shear- (S) and compressional-wave (P) seismic reflection data to obtain an accurate geological/geophysical model with reliable seismic velocities for local-scale seismic site response studies, as needed for hazard assessment and calculation of earthquake scenarios. As an application case, we focus on a microzonation study performed for the Cavezzo municipality in Northern Italy. The investigated site is located in the epicentral area of the 2012 Emilia earthquake in the Po Valley, which is a typical deep sediment-filled basin. Specifically, in this study we were able to: (1) confirm the advantages of reflection seismic prospecting for soft-sediment basin characterization; (2) evaluate the resolution of S- and P-wave signals and their depth of penetration; (3) improve the knowledge on the geological structure of the Cavezzo area by measuring S- and P-wave interval velocities in Plio-Quaternary formations. • S- and P-wave signal resolution and penetration capabilities have been assessed. • Seismic reflection data were processed to directly evaluate the local seismic response. • An improved S- and P-wave interval velocities model for the Plio-Quaternary formations of the Po Plain are presented. [ABSTRACT FROM AUTHOR]

The seismic hazard studies for Egypt have been initiated a long time ago aiming to predict the ground motion parameters at different geographical scales; their review process had been routinely performed due to the increase of available instrumental observations rather than from methodological advances. For the comprehensive understanding of the development of seismic hazard assessment (SHA) studies in Egypt, we properly collect and test the existing SHA maps, computed at different geographic scales, against the available observations, data quality, physical assumptions and adopted methodology. Most of these SHA studies are probabilistic and the mapped ground motion acceleration values have been often largely exceeded by the observed values due to earthquakes occurred after their publication. For each study, we discuss and evaluate the input data, methodology and the results obtained in order to understand the reasons behind the bad performance of the available seismic hazard maps and to avoid such shortcomings in future seismic hazard assessment. Finally, we formulate suggestions that could be considered before new seismic hazard maps are released and then adopted, for the real benefit of society. [ABSTRACT FROM AUTHOR]

The main goal of this work is to provide an update on the seismic hazard maps available for Egypt that incorporates the results of recent studies, i.e. revised historical earthquake catalogs, morphostructural zonation data (MZ), revised focal mechanism solutions and mechanical models of the lithospheric structure. This is done within the framework of the neo-deterministic seismic hazard assessment (NDSHA) procedure that may effectively accommodate any reliable new information to adequately compute the earthquake ground motion maps (i.e. PGA, PGV and PGD). Furthermore, with the set of relevant scenario earthquakes, this work provides a large dataset of synthetic seismograms, particularly important for the areas that suffer from the endemic lack of useful strong motion time histories such as Egypt, setting the base toward detailed and comprehensive seismic microzonation studies. NDSHA aims to supply an envelope value, in other words a value that should not be exceeded, therefore it is immediately falsifiable and verifiable. A sensitivity analysis based on the different ground motion maps, computed adopting different (a) models for the earthquake source process, (b) mechanical models of the crust and (c) mapmaker's preconceptions (e.g. different seismotectonic models), is provided. The maps of difference and ratio between various ground motion maps computed for different variants are shown and discussed in order to explore the influence of using various input models. The results provide the potential users with an adequate spectrum of choices and reliably assess and clearly communicate the possible uncertainties. The availability of a wide spectrum of hazard maps is a prerequisite to supply valuable information for the significant improvement of a seismic code. [ABSTRACT FROM AUTHOR]

The seismic hazard assessment of Tehran, the capital of Iran with a population of over 10 million, is necessary in the decision-making process for risk reduction. The main objective of this paper is to present a procedure for obtaining maximum hazard maps in seismically active regions such as Tehran with a history of destructive earthquakes, but where the number of the instrumentally recorded large magnitude events is small. The deterministic and probabilistic seismic hazard methods are two quantitative approaches with some practical limitations. To overcome their limitations, the Bayesian statistics are used to estimate maximum earthquake magnitude by combining prior seismological information with the available limited data. The Bayesian approach is used to estimate maximum earthquakes corresponding to different individual ground-motion scenarios at a specific hazard level. The maximum hazard maps are obtained by merging different individual worst-case ground-motion scenarios at a specific hazard level. The hazard analyses under different scenarios are conducted by the finite-fault procedure which uses geological and seismological parameters for each seismic source. The obtained results are in agreement with the observed intensities of historical earthquakes. Moreover, the conventional approach of probabilistic seismic hazard analysis is presented to show the difference between the two procedures. The findings provide information about the seismic design or retrofit of structures and infrastructures. [ABSTRACT FROM AUTHOR]

Seismic microzonation is an important step in seismic risk and loss studies for densely populated urban regions. Ambient noise studies using H/V measurements to determine the fundamental site period (FSP) can be an inexpensive and efficient method to map site effects for a microzonation study. Ambient noise studies are particularly effective in high impedance contrast environments like Boston, Massachusetts, where the soil depth ranges from 1 to 80 m and the soil (shear-wave velocity, V s = 200 m/s) overlays hard glacial till or bedrock (V s = 2000–3000 m/s). In this study, ambient noise data were collected from 570 locations in the greater Boston area. Nakamura's technique, taking the ratio of the Fast Fourier Transform (FFT) of horizontal components to vertical components, is applied to determine the FSP. The FSP data are mapped across the region and show a consistent pattern with the local geologic and geomorphologic conditions. The FSP data are then paired with depth to bedrock and V s30 drawn from 2403 boring logs and 25 V s profiles (V s30 is defined as the time-weighted average of the V s in the upper 30 m of the soil profile). The depth to bedrock and FSP are correlated, as are FSP and V s30 measurements. FSP/depth to bedrock and FSP/V s30 correlations are reported with 95% confidence bounds for use in regional planning. The resulting FSP/V s30 correlation is comparable with similar studies from high impedance contrast regions in Canada and Japan and show lower V s30 for sites with FSP > 0.2 s (where the FSP predicts depth to bedrock > 18 m) than previously reported for the NGA-West2 database. The accuracy of single station ambient noise results is also confirmed with single-station and vertical-array earthquake spectral ratios. An FSP (~ 0.74 s) was calculated from ambient noise data at the Northeastern University (NEU) Vertical Array site in the Back Bay of Boston. At this site the sediment thickness is 51 m and is consistent with the FSP (~ 0.73 s) calculated for the site using earthquake records from the 2011 Mw 5.8 Mineral, Virginia earthquake. Overall, the outcomes of this study demonstrate that ambient noise studies can be used in high impedance contrast environments to reliably and consistently estimate the FSP. When the FSP estimates are paired with additional data such as depth to bedrock, V s30 estimates, and recorded ground-motion data, the spatial distribution of regional site effects can be characterized. [ABSTRACT FROM AUTHOR]

The source of the 1886 Charleston, South Carolina earthquake influences the computed seismic hazard of the Southeastern U.S. and thus impacts public policy and engineering practice. However, because the 1886 rupture predated seismic instruments, its source is highly uncertain. This study presents probabilistic seismic-source inversions of the Charleston earthquake from liquefaction evidence and historical intensity reports. Using the latest predictive models and a novel inversion approach, we seek to constrain the magnitude, location, and orientation of the 1886 rupture. Probability distributions of rupture magnitude are conditioned on both the "Woodstock Fault" – a commonly inferred source of the 1886 event – and on an unknown source, wherein the uncertainties of fault location and orientation are considered. These distributions are compared to the M w 6.7-M w 7.5 distribution adopted by the U.S. National Seismic Hazard Model Project (NSHMP). Collectively, the results do not provide strong support for the hypothesized Woodstock Fault. This is not to say the Woodstock Fault does not exist or could not have caused the 1886 rupture, but rather, that the position of the 1886 source model cannot be constrained by the data and models studied herein, given the large uncertainties inherent to each. While this is at odds with the underlying assumption of prior studies, the results nonetheless generally uphold the magnitude distribution adopted by the NSHMP. The largest uncertainties inherent to this distribution are identified and could be diminished in the future. Finally, we note that the inversion methodology used here is not specific to any region, or to certain types of evidence, but can be applied to any seismic zone and to any co-seismic response. This methodology allows for uncertainty to be accounted for in a more complete and transparent manner when inverting seismic source parameters from macroseismic data. Of course, any limitations, biases, or unmodeled uncertainties inherent to these data must be understood, and their implications acknowledged, as further discussed herein. • The source of the 1886 Charleston earthquake influences the computed seismic hazard of the region but is highly uncertain. • The earthquake's source is probabilistically inverted from liquefaction evidence and felt intensity reports. • The results do not provide strong support for the Woodstock Fault – an often inferred source – which is not to say it does not exist. • While this is at odds with the assumption of many prior studies, the results generally support the magnitude distribution adopted by the National Seismic Hazard Modeling Project. • Our approach allows for more complete accounting of uncertainties when inverting seismic sources from macroseismic data. [ABSTRACT FROM AUTHOR]

this study presents the development of a region- and -site specific ground motion model (GMM) based on ground motion data obtained from the I-lan alluvial basin in northeastern Taiwan. The development was performed by calibrating the ergodic Phung et al. (2020) (Ph20) GMM developed for Taiwan. The source of strong ground motion data includes events from shallow crustal and subduction zones with magnitudes (M W) from 4.0 to 7.6, records from distances shorter than 200 km, and focal depths up to 150 km. The resulting regional model accounts for peculiarities that are not captured by the ergodic Ph20 GMMs, such as (1) the difference in source type effects, (2) V S30 -scaling from the local site effects, and (3) enhancement of long period spectral ordinates due to the deep sedimentary basins. The standard deviations of the local model are much lower than those of the ergodic model, particularly the component of the standard deviation that corresponds to the site-to-site variability (ϕ S 2 S), indicating that better site characterization can significantly reduce the overall uncertainty in ground motion estimation. • The bilinear- Vs30 scaling is better represented by the regional data rather than the linear Vs30 -scaling of the ergodic GMM. • Regional characteristics are significantly characterized by the source-type effects and site effects. • Two way random effects model should be considered when performing a site – specific probabilisitic seismic hazard analysis. [ABSTRACT FROM AUTHOR]

This paper presents a probabilistic approach for seismic stability analysis of a slope at a given site in a specified exposure time. For a probabilistic seismic stability analysis, the ground motion parameter, in terms of the peak ground acceleration (PGA), at a given site in a specified exposure time of interest (say, 30 years) is treated as a random variable, and the PGA distribution at the given site is derived based on the USGS National Seismic Hazard Maps data. Further, the spatial variability of the soil property is simulated herein by a random field, and the fluctuation of the groundwater level is simulated by a random variable. Within the probabilistic framework, a deterministic model for evaluating the slope stability is required; here, a pseudo-static analysis is adopted and implemented through 2D finite difference program FLAC version 7.0. In the face of the uncertainties in the input parameters, the performance or safety of the slope is expressed as a failure probability; within the proposed probabilistic analysis framework, a recently developed sampling method is adopted for the uncertainties propagation through the deterministic solution model. This probabilistic analysis framework is demonstrated with an illustrative example of a two-layer earth slope. Finally, a parametric study is undertaken to investigate how the failure probability of the slope (at a given site in a specified exposure time) is affected by the uncertain factors such as the earthquake-induced ground motion and the spatial variability of soil property. The study results demonstrate the versatility and effectiveness of the proposed framework for probabilistic seismic stability analysis of slope at a given site in a specified exposure time. [ABSTRACT FROM AUTHOR]

In historical earthquakes, fault ruptures have caused significant ground deformation and infrastructure damage. Because the occurrences of earthquakes are hard to predict, it is critical to assess the area influenced by fault propagation for disaster resistance. Based on trench excavations in active fault zones, earthquake faults propagated through the composite strata with gravel deposits are common. However, the stratigraphy change of the overburden strata and the non-spherical granular particles of the gravel deposit are rarely considered in most case studies. This study proposes a procedure that utilizes digital image analysis and discrete element modeling to estimate the composite strata deformation induced by thrust faulting. The procedure is demonstrated through a series of small-scale sandbox modeling and a case study of the Chushan excavation site in Taiwan. The gravel fabric, including gravel volumetric content, aspect ratio and initial long-axis orientation, are considered in the parametric study as well as the configuration of the strata composition. Simulations show that fault propagation restricts in the overburden because the faulting-induced kinematic energy is mostly dissipated by clast rotation, resulting in a lower fault extended distance and a wider tri-shear zone. The rotation of the gravels shows good agreement with the range of the tri-shear zone, indicating that the long-axis orientations of gravels can be an indicator to interpret the faulting history. Overall, it is feasible to construct a reasonable numerical model for assessing fault rupture-composite strata interaction (FR-CSI) once the outcrop photo data are available. The proposed procedure is useful for efficient and reliable scenario modeling regarding earthquake hazard mitigation. • In-situ gravel fabric is characterized by digital orthogonal imagery analysis. • The characterized gravel fabric is implemented into 3D DEM model to study the ground deformation under thrust faulting. • Influences of gravel volumetric content, aspect ratio, initial long-axis orientation, and strata composition are evaluated. • Trench modeling shows the evolution of transitional structural geometries within composite strata in seismic history. [ABSTRACT FROM AUTHOR]

• Slope reconstruction of a pre-historic landslide with 3D geomodelling. • Three-dimensional back-analysis with distinct element code. • Flysch landslide with anti-dip slope bedding of Carpathian Mountains. • Simulation of internal degradation/fracturing of rock mass during landsliding. • Outlook to future seismic hazard analyses of the Vrancea-Buzau region (Romania). Ancient landslides of unknown origin can be found in large numbers in mountainous regions; some represent valid markers of (pre-)historic natural regimes referring to either long-term evolution or short-term peak events of climatic and seismotectonic nature. An example is represented by the Balta rockslide in the Romanian Carpathian Mountains. Its location in the seismically active Vrancea-Buzau region, as well as its morphological features, deep-seated rupture surface and large debris volume, raise the question of its failure history with regard to a possible co-seismic triggering. A 3D volume based reconstruction of the slope morphology together with field measurements of elasto-plastic in-situ rock properties allow to estimate pre-failure conditions of the slope, with special regards to the geological, i.e. flysch bedrock of poor to fair rock quality, and structural settings, i.e. anti-dip slope bedding crossed by the main joint family. The reconstructed slope behaviour was tested under static and dynamic forces with the 3D distinct element code 3DEC, subsequently used to simulate a failure scenario with a 120 s long real earthquake record that leads to the realistic post-failure morphology of Balta. For the latter, we observe a principally joint-controlled failure combined with internal fracturing of the undamaged rock mass. After 230 s of simulated time, the landslide debris reaches the valley bottom with maximum displacements of 1350 m and is marked by a lateral expansion to a broader extent than the source zone width, as observed in the field. Extension of this work to other pre-historic slope failures in the valleys of Vrancea-Buzau yield valuable new information for future seismic hazard estimations of the region. [ABSTRACT FROM AUTHOR]

Seismic site amplification and seismic hazard maps are crucial inputs for decision making and risk evaluation in places where seismicity imposes a significant risk to human life and infrastructure. In this work, we propose a novel machine learning (ML) based methodology to integrate qualitative and quantitative data to map the degree of seismic amplification in an area of Chile, one of the most seismically active countries on Earth. Our method uses measurements of surface shear wave velocities (V s30) and predominant frequencies (f 0) combined with gravity anomaly maps to update the geographic extension of seismic amplification classes. Additionally, we trained the predictive models to interpolate and extrapolate V s30 and f 0 to the unsampled sites. Applying this method to the Santiago basin resulted in (i) a refined seismic amplification map, and (ii) maps of V s30 and f 0 estimated with improved accuracy. The best predictions, obtained by ML techniques and validated through cross-validation, are possibly due to the inclusion of spatial covariates for algorithm training, enhancing the ability of the model to capture the spatial correlations of geological, geophysical and geotechnical data. The estimation of predominant frequencies (f 0) is improved considerably by including gravity as a covariant. The accuracy of the f 0 predictions apparently depends more on the choice of covariates than on the algorithm used, while the V s30 predictions are more sensitive to the chosen algorithm. These results illustrate the great potential of machine learning predictive algorithms in digital soil mapping, which surpass traditional geostatistical techniques. The major contribution of this work is to introduce a novel methodology, based on artificial intelligence models, to extend local measurements of site-specific dynamic properties. This information can be used to quantitatively estimate seismic hazard over a regional scale. • We propose a methodology for integrating data to map dynamic site characterization using machine learning. • Our method uses measurements of Vs30 and f0 combined with gravity anomaly and geology. • We trained predictive models to interpolate Vs30 and f0 in the Santiago de Chile basin. • The best predictions were obtained thanks the inclusion of spatial covariates for algorithm training. • The estimation of f0 is considerably improved by including gravity as a covariant. [ABSTRACT FROM AUTHOR]

The Sichuan-Tibet Railway in eastern Tibet runs across numerous seismogenic faults with high seismic risks. The Lancangjiang fault (LCJF), one of the essential strike-slip faults within the Qiangtang block, traverses the railway. However, the geometry and late Quaternary activities of the LCJF remain unclear, limiting the assessment of seismic hazards on the Sichuan-Tibet Railway and the understanding of kinematic patterns in eastern Tibet. Based on the interpretation of high-resolution satellite imagery, field observations, and shallow geophysical exploration, we first mapped the detailed geometry of the northern LCJF. It consists of two branches: Yangda-Yaxu fault (YYF) and Baqing-Leiwuqi fault (BLF), which merge eastwards onto the main LCJF. Displaced landforms and multiple numerical dating techniques reveal that the YYF is a mainly sinistral fault with a late Quaternary slip rate of ~2.2 + 0.6/−0.5 mm/yr and a minor vertical component (~0.1 mm/yr). The BLF undergoes an oblique motion with a left-lateral slip rate of ~1.2 + 0.5/−0.3 mm/yr and a northeast-vergent reverse rate of ~1.2 + 0.4/−0.2 mm/yr in the Holocene. Vector analysis of slip rates suggests that the LCJF has a sinistral rate of ~3.5 + 1.1/−0.8 mm/yr with a reverse component of ~1.6 + 0.4/−0.3 mm/yr, displaying an essential role in strain partitioning of eastern Tibet. Together with slip rates of other intra-block faults, the kinematic pattern of eastern Tibet probably applies to the sub-block model. Offset geologic units yield a total displacement of ~10–11 km for the YYF. Using the slip rate of the YYF, the LCJF was initiated at ~5.9–3.9 Ma, probably related to the establishment of the present-day strain pattern and the onset of crustal thickening in eastern Tibet during the late Miocene. In addition, the active YYF and BLF across the Sichuan-Tibet Railway have a seismic potential of Mw ~7.2–7.3 that will produce a ~ 1.8–2.0 m sinistral slip on the YYF, and a ~ 2.0 m horizontal, and ~ 1.1–1.3 m reverse motion on the BLF. They will pose a high seismic hazard potential on the railway. This study provides quantitative data for regional seismic hazard analysis and shows insights into the deformation mechanism of the plateau. • The geometry of the northern LCJF is first mapped. • The northern LCJF has a late Quaternary ~3.5 mm/yr sinistral and ~ 1.6 mm/yr reverse rate. • The seismic potential of the northern LCJF on the Sichuan-Tibet Railway is estimated. • The LCJF takes an important role in strain partitioning in eastern Tibet. • The initiation of the LCJF is related to the late-Miocene tectonic event in eastern Tibet. [ABSTRACT FROM AUTHOR]

In this paper we present a new methodological approach which integrates geological and geophysical data into a 3D modelling process to be mainly employed in seismic hazard assessment studies of earthquake-prone areas around the world, as well as in applications for land use and urban planning. As a case study, the reconstruction of a geology-based 3D velocity model of the uppermost hundreds of metres of the Amatrice high-seismic-hazard area is described. The model was constructed using geological (e.g., maps, cross-sections and core-wells) and geophysical (e.g., down-hole, MASW, refraction, and seismic noise measurements) data, which were georeferenced and uploaded into 3D geological modelling software, where faults, stratigraphic boundaries, and geophysical attributes were digitised, checked, hierarchised, and modelled. The performed 3D geological model was parameterised with V s and V p velocities and, finally, the environmental noise (i.e., horizontal-to-vertical spectral ratio analysis, HVSR) recorded at some seismic stations was compared with the seismic responses modelled at some nearby control points. In the study area, the proposed geology-based 3D velocity model represents both a new potential geophysical prediction tool for areas devoid of geophysical measurements (i.e. HVSR curves) and a potential input-model for future ground-motion and seismic-wave-propagation simulations aimed at a more precise local seismic response assessment and, consequently, at the development of more realistic seismic hazard scenarios. The model here presented constitutes a first version of the 3D geological-geophysical model for the studied area, which will be improved with new data and more advanced algorithms available in the future. [Display omitted] • A new methodological approach for the 3D geophysical model reconstructing is proposed. • The first 3D geology-based velocity model of the Amatrice area was reconstructed. • The model integrates and completes the earlier studies on the Amatrice Basin. • The performed model represents a new geophysical prediction tool for the Amatrice area. [ABSTRACT FROM AUTHOR]

The parameters of rock mass structures, strength and seismic effect are critical factors for the seismic stability analysis of rock slopes. This paper demonstrates the use of a new form of a chart-based slope stability method that satisfies the Hoek-Brown (HB) criterion. The limit equivalent method is used to assess the stability of rock slopes subjected to seismic inertial force. First, stability charts for calculating the factors of safety (FoS) with a slope angle of β = 30° in static and pseudo-static states were proposed by using Slide 6.0 software. Next, scaling factors of the horizontal seismic acceleration coefficient ( f Kh ) and slope angle ( f β ) were established to illustrate the influence of the horizontal seismic load and slope angle on the stability of rock slopes, respectively. Using regression analyses of f Kh and f β , a fast calculation model was proposed to solve the slope safety factors based on the stability charts. Finally, the stability charts analysis method (SCAM) was verified against the numerical solutions; the results showed that 70.63% of the data had discrepancies of less than ± 10%, and the data with discrepancies greater than ± 10% were associated with high values of geological strength index ( GSI ) and horizontal seismic acceleration coefficient ( K h ). The proposed model calculating the FoS of rock slopes is simple and straightforward to use for seismic rock slope design and stability evaluation. [ABSTRACT FROM AUTHOR]

To quantitatively map regional lateral spread hazard considering a complete portfolio of possible earthquakes is fundamental for a seismic risk assessment over large spatial coverage. This paper presents a probabilistic model of liquefaction-induced lateral spread considering seismic randomness and uncertainty of soil properties. This model enables quantitative maps of lateral spread displacement at any exceedance probability in a specified time period, or exceedance probability of any pre-defined displacement threshold. Two mapping procedures are illustrated through a case study by generating hazard maps of lateral spread based on available cone penetration test data. These maps highlight the hotspots susceptible to serious lateral spread displacements, providing useful information on need of project-specific in-depth geotechnical investigation. The mapping procedure is based on either geostatistical interpolation or stochastic simulation. The geostatistical interpolation method has the merit to be less computationally expensive, while the stochastic simulation method seems more rational as it explicitly model the uncertainty of soil parameters and their spatial structure. [ABSTRACT FROM AUTHOR]

The accurate assessment of the stability of slopes during earthquakes has become a critical issue in seismically active areas. To readily evaluate seismic slope hazards in a region, we developed an empirical model for estimating seismic slope displacements for both shallow and deep types of failures (i.e., rigid and flexible sliding mass, respectively). The prediction model is simply a function of peak ground acceleration (PGA) and mean period of ground motions (T m ). For predicting displacement of shallow failure, the PGA and T m of incident motion can be directly used in the model. For predicting the displacement of deep failure, however, the dynamic response of flexible sliding block interacts with the incident motion. The changed PGA and T m , defined as k max and T m,k for the seismic loading of flexible sliding mass, respectively, is estimated depending on the natural period of sliding mass (T s ). Therefore, the predicting displacement of flexible mass is achieved using k max and T m,k in lieu of PGA and T m in the developed rigid model. This general model provides a consistent approach for predicting the sliding displacement of shallow (rigid) and deep (flexible) slope failures. [ABSTRACT FROM AUTHOR]

The uncertainty assessment for the development of the new seismic hazard maps of Spain is explained in this work. A detailed description of how uncertainties are considered in the different phases followed for the probabilistic seismic hazard assessment study is presented. Special emphasis is given to the characterization of the uncertainty of earthquake size parameters contained in the catalog, and their propagation to subsequent phases of the analysis such as catalog homogenization, completeness and declustering. Aleatory and epistemic uncertainties are examined and assessed using Monte Carlo simulations and a logic tree, respectively. The final impact of uncertainty in hazard estimates is evaluated through coefficient of variation maps, showing the areas where larger and lower variability is obtained. The hazard maps developed in this work are intended to be the basis for the future revision of the Spanish seismic code. [ABSTRACT FROM AUTHOR]

Although drapery systems are commonly used to control rock fall hazard on steep slopes, some elements of their design such as the interface friction between the mesh and ground surface are still difficult to quantify in practice. This technical note presents a new test procedure designed to study the mechanism of rock–mesh interaction in the laboratory. A series of tilt tests and tests with increasing loads were performed to study the effects that number and type of rock–mesh contacts, slope angle, and mesh characteristics had on mesh–rock interaction. The obtained data indicated that the process of interlocking between the mesh and rocks could increase the mesh's resistance to failure as well as decrease the force acting on the anchors during accumulation of rock debris or snow. Some changes to the current guidelines regarding the selection of interface friction angle are also suggested. [ABSTRACT FROM AUTHOR]