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Given the recent developments in machine-learning technology, its application has rapidly progressed in various fields of earthquake seismology, achieving great success. Here, we review the recent advances, focusing on catalog development, seismicity analysis, ground-motion prediction, and crustal deformation analysis. First, we explore studies on the development of earthquake catalogs, including their elemental processes such as event detection/classification, arrival time picking, similar waveform searching, focal mechanism analysis, and paleoseismic record analysis. We then introduce studies related to earthquake risk evaluation and seismicity analysis. Additionally, we review studies on ground-motion prediction, which are categorized into four groups depending on whether the output is ground-motion intensity or ground-motion time series and the input is features (individual measurable properties) or time series. We discuss the effect of imbalanced ground-motion data on machine-learning models and the approaches taken to address the problem. Finally, we summarize the analysis of geodetic data related to crustal deformation, focusing on clustering analysis and detection of geodetic signals caused by seismic/aseismic phenomena. [ABSTRACT FROM AUTHOR]

Türkiye poses a complex crustal structure and tectonic settings owing to the northward convergence of the Arabian and African plates with respect to the Anatolian and Eurasian plates. A reliable 3-D crustal structure of the unruptured segment of the North Anatolian Fault Zone (NAFZ) in the Sea of Marmara is thus of utmost importance for seismic hazard assessments considering that the megacity Istanbul—with more than 15 million habitants—is close to this seismic gap. This study provides high-resolution shear wave velocity images of northwestern Türkiye, including the NAFZ, revealed from ambient seismic noise tomography. We extract over 20 000 Green's functions from seismic ambient noise cross-correlations and then construct group velocity perturbation maps from the measured group delays with a transdimensional Bayesian tomographic method. We further perform an S -wave velocity inversion to image depth-varying velocity structures. Our high-resolution data allowed us to image S -wave velocities down to 15 km depth and reveal weak crustal zones along the NAFZ, as indicated by low shear wave velocities. We find a low-velocity zone along the Main Marmara Fault, linked with aseismic slip and a deep creep mode. Furthermore, we identify a high-velocity anomaly associated with the unruptured section that defines the boundaries of the locked zone in the crust, which can potentially trigger a destructive earthquake in the future. [ABSTRACT FROM AUTHOR]

This document is a compilation of various research papers and abstracts related to seismic activity and earthquake research in Croatia and Hungary. The papers cover topics such as seismic site amplification, site response analysis, local site effects, lithosphere structure, gravity anomaly models, and seismic performance assessment of buildings. The research provides valuable insights into earthquake risk and mitigation strategies in the region. The document also includes links to additional information and resources for further exploration. [Extracted from the article]

On January 12, 2010, Haiti was hit by one of the largest seismic disasters known to date. At the time, the culture and perception of seismic risk was low among the population and--because of the lack of seismic sensors in Haiti--so was seismological knowledge. In a citizen seismology approach, the S2RHAI project used low-cost seismic sensors (Raspberry Shake) to (1) complement the national seismic network and (2) to improve risk perception, preparedness, and scientific knowledge of the population. Through these objectives, we introduce a paradigm shift in which seismic networks are not only composed of sensors, but also of citizens who gather around these tools and the information they produce. We present here the results of a qualitative survey of 15 Raspberry Shake (RS) seismometer hosts in Haiti. Semi-structured interviews were conducted to learn about users' experience to assess their motivations, difficulties, and expectations in this citizen seismology process. We found that RS hosts expressed pride and interest in being part of the RS network and actively contributing to risk reduction in their community. Some of them reported a form of empowerment in that they could compensate for the deficiency of the state, which they generally distrust. However, the RS hosts also expressed the need for more technical and scientific support from scientists. Also, few of them engaged in mediation activities or discussions with their community members, partly because they feared that this would awaken the trauma caused by the earthquake of 12 January, 2010. This allowed us to list concrete actions to (1) improve the seismic information system, (2) better integrate the volunteers into the network, (3) enrich the collaboration between citizens and seismologists, and (4) accompany them in their role as ambassadors to their community. We conclude that understanding the motivations, obstacles, and expectations of volunteers is essential to increase the chances of sustainability of this citizen seismology project. [ABSTRACT FROM AUTHOR]

Studies on earthquakes that occurred in the early instrumental period of seismology are of importance for the seismic hazard assessment and are still under investigation since new data are being increasingly revealed. We study the case of a moderate-to-strong earthquake that occurred on 15 July 1909 in NW Peloponnese, Greece. Although the earthquake event was quite destructive, it remains little-known so far in the seismological tradition. We compiled a variety of documentary sources and showed that the earthquake caused extensive building destruction in Chavari and in many other villages with an estimated maximum intensity IX (in EMS-98 scale) and a death toll as high as 55. We also assigned macroseismic intensities in several observation points and drew isoseismal lines by applying the nearest-neighbor technique. From empirical relationships between magnitude and intensities, we estimated the macroseismic magnitude of proxy Ms5.9. Our examination also revealed a variety of earthquake associated phenomena including several types of precursors and abundant co-seismic hydrological changes and ground failures, such as soil liquefaction, surface ruptures, and rock falls. Since no surface fault-trace was reported, the determination of the causative blind fault remains an open issue for future investigation. [ABSTRACT FROM AUTHOR]

In the last hundred years alone, there have occurred more than 2000 earthquakes larger than 4 in the northern and northwestern parts of Iran. Because Iran is placed in the heart of the Alpine-Himalayan collision zone, which is one of the world's greatest seismic locations, massive earthquakes have regularly struck the country. Seismic hazard assessment is a realistic and helpful method for engineering seismology to prevent motions in a location in order to forecast the occurrence of earthquakes. For parameter estimation in seismic hazard assessments, the Bayesian probability theory provides a practical and accurate technique. As a result, Bayesian techniques for analysis are based on an older method. Furthermore, they have the unique capacity to account for the variability of characteristics in probabilistic relationships. In this assessment, we used the Bayesian earthquake risk estimation program developed by Lyubushin. Our research is in the sequence of applications of this program to assess the risk of earthquakes in various parts of the universe. In this method, the basic assumption is that earthquakes follow the characteristic of being Poisson. Its zoning map is drawn in the north and northwest regions of Iran. The highest value was obtained for the city of Tabriz with 0.29 galls, and the lowest value was obtained for the city of Zanjan with the value of 0.06 galls. [ABSTRACT FROM AUTHOR]

Performance and possible causes of seismic activity in the southern of Santiago de Cuba province were evaluated, based on the geological and tectonic information available and records of the earthquakes occurred in this region in January 17, 2016 at 08:17 UTC. The analysis of the space-time-energy parameters of the earthquakes showed the coherence between the results of three of the networks monitoring the region, namely, the Cuban National Seismological Service (SSNC), the United States Geological Service (USGS) and the German Center for Geo-scientific Research (GEOFON)). For three of the earthquakes, the seismic moment tensors were calculated by reversing the corresponding waveforms. Comparing the results of two of them with those obtained by other agencies that monitor the area was totally consistent with fault planes oriented N-S with compressive focal mechanisms. The third earthquake, which occurred a week later in the east of the province, also had a compressive mechanism, although with a NW SE orientation on the fault plane. The seismic activity that initially performed like a swarm of earthquakes, performed differently later; similar to aftershocks registered after a higher-energy earthquake, following Omori's Law, that is, the type of premonitorymain earthquake event-aftershocks. [ABSTRACT FROM AUTHOR]

Earthquakes of 1 to 3 magnitudes eventually reaching up to 8, take place in Cuba and adjacent areas. Although those with a magnitude greater than 3 are generally perceptible, the ones usually causing damage are those with a magnitude greater than 5; however, its negative impact largely depends on the state of the built infrastructure and the hypocenter. This essay is a contribution to risk perception in Cuban population and it introduces the concept of cities in seismic alert, which is based on the principle that where destructive seismic events occurred in the past it is very likely they will be repeated in the future, unless the infrastructure be substantially improved. A set of recommendations is also proposed for Cuban cities defined in seismic alert. [ABSTRACT FROM AUTHOR]

The 2020 Mw 6.8 Elazığ earthquake was the largest along the East Anatolian Fault (EAF) in over a century, providing valuable insights into its rupture behavior. We use satellite geodesy and seismology to detail the mainshock rupture, postseismic deformation, and aftershocks. The mainshock propagated mostly westward at ∼2 km/s from a nucleation point on an abrupt ∼10° fault bend. Only one end of the rupture corresponds to an established EAF segment boundary, and the earthquake may have propagated into the slip zone of the 1874 M ∼ 7.1 Gölcuk Gölu earthquake. It exhibits a pronounced (∼80%) shallow slip deficit, only a small proportion of which is recovered by early aseismic afterslip. The slow rupture velocity, shallow slip deficit, and minimal afterslip are characteristic of earthquakes hosted by faults of low‐to‐intermediate structural maturity, indicating that faults continue to evolve in important ways even as they accrue cumulative offsets of tens of kilometers. Plain Language Summary: We investigate the 2020 Mw 6.8 Elazığ (Turkey) earthquake, the largest along the East Anatolian Fault (EAF) in over a century. Anatolian faults are emblematic within the earthquake science community, but most attention has focused on the North Anatolian fault which ruptured repeatedly during the twentieth century, and relatively little is known about the EAF. We use satellite geodesy and seismology to map fault motions during the earthquake, after the earthquake, and in its aftershock sequence. Documenting relations between this earthquake, previous earthquakes, and early postseismic deformation is pivotal to gain a better understanding in what drives rupture behavior. Our results show that previous structural models of the EAF were only partially successful in predicting the end points of the 2020 rupture and that many aspects of this earthquake are characteristic of structurally immature faults. These results are important for seismic hazard assessment in this region. Key Points: The mainshock propagated mostly westward from a nucleation point on an abrupt ∼10° fault bendOnly one rupture termination corresponds to an established EAF segment boundary, and the rupture may partially overlap with an 1874 earthquakeThe mainshock exhibits a pronounced shallow slip deficit that is not fully recovered through early shallow afterslip [ABSTRACT FROM AUTHOR]

The increasing number of damaging earthquakes, induced by underground injection of fluids, demonstrates the need of a structured methodology for critical thinking about and clear communication of induced seismic risk. Using the Pohang, South Korea, geothermal project and the damaging (US$75M) local magnitude ML 5.35 induced earthquake in 2017, we present a straightforward methodology that summarizes induced seismic risk in a single time‐dependent number, the Value at Induced Risk (VaIR). VaIR quantifies the amount of economic losses that will not be exceeded at a given confidence level. Our method reveals that the Pohang project was exposed to a 2% chance of causing economic losses of US$140M or more (1% of US$3.2B or more). The high risk could have been identified during the sequence of reservoir stimulation, lasting almost 2 years. VaIR opens new ways to assess and communicate risk to all stakeholders for informed risk management decision making. Plain Language Summary: High‐pressure injection at a geothermal reservoir close to the city of Pohang, South Korea, triggered a damaging (US$75M) ML 5.35 earthquake in November 2017. We present a straightforward methodology for seismic risk assessment, communication, and management for underground injection of fluids. Our method, Value at Induced Risk (VaIR), combines preoperation loss scenario modeling and magnitude‐frequency statistics of the evolving induced seismicity catalog to monitor the evolution of induced seismic risk in real time. Retrospectively, we apply VaIR to the Pohang case. Operators, regulators, and nonexpert stakeholders could have been well‐informed about the elevating risk caused by underground injection in real time. Application of VaIR to future underground injection projects will help to exclude unacceptable losses with high confidence. Key Points: Value at Induced Risk (VaIR) is a straightforward method to communicate and manage seismic risk caused by underground injection of fluidsVaIR combines preoperation loss scenario modeling and magnitude statistics of the evolving induced seismicity catalog to monitor riskVaIR helps to exclude unacceptable losses with high confidence and to inform operators, regulators and nonexpert stakeholders at risk [ABSTRACT FROM AUTHOR]

The increasing number of damaging earthquakes, induced by underground injection of fluids, demonstrates the need of a structured methodology for critical thinking about and clear communication of induced seismic risk. Using the Pohang, South Korea, geothermal project and the damaging (US$75M) local magnitude ML 5.35 induced earthquake in 2017, we present a straightforward methodology that summarizes induced seismic risk in a single time‐dependent number, the Value at Induced Risk (VaIR). VaIR quantifies the amount of economic losses that will not be exceeded at a given confidence level. Our method reveals that the Pohang project was exposed to a 2% chance of causing economic losses of US$140M or more (1% of US$3.2B or more). The high risk could have been identified during the sequence of reservoir stimulation, lasting almost 2 years. VaIR opens new ways to assess and communicate risk to all stakeholders for informed risk management decision making. Plain Language Summary: High‐pressure injection at a geothermal reservoir close to the city of Pohang, South Korea, triggered a damaging (US$75M) ML 5.35 earthquake in November 2017. We present a straightforward methodology for seismic risk assessment, communication, and management for underground injection of fluids. Our method, Value at Induced Risk (VaIR), combines preoperation loss scenario modeling and magnitude‐frequency statistics of the evolving induced seismicity catalog to monitor the evolution of induced seismic risk in real time. Retrospectively, we apply VaIR to the Pohang case. Operators, regulators, and nonexpert stakeholders could have been well‐informed about the elevating risk caused by underground injection in real time. Application of VaIR to future underground injection projects will help to exclude unacceptable losses with high confidence. Key Points: Value at Induced Risk (VaIR) is a straightforward method to communicate and manage seismic risk caused by underground injection of fluidsVaIR combines preoperation loss scenario modeling and magnitude statistics of the evolving induced seismicity catalog to monitor riskVaIR helps to exclude unacceptable losses with high confidence and to inform operators, regulators and nonexpert stakeholders at risk [ABSTRACT FROM AUTHOR]

The magnitude of postseismic slip is useful for constraining physical models of fault slip. Here we examine the postseismic slip following intermediate‐magnitude (M 4 to 5) earthquakes by systematically analyzing data from borehole strainmeters in central and northern California. We assess the noise in the data and identify 11 earthquakes that generated interpretable strain records. We estimate the earthquakes' postseismic to coseismic moment ratios by comparing the coseismic strain changes with strain changes induced by afterslip in the following 1.5 days. The median estimated postseismic moment is 0.45 times the coseismic moment, with a 90% confidence interval between 0.25 and 0.60. This postseismic moment is slightly larger than typically observed following large (M > 6) earthquakes but smaller than observed following small (M2 to 4) earthquakes. The intermediate‐magnitude postseismic slip suggests a size dependence in the dynamics of earthquakes or in the properties of fault areas that surround earthquakes. Key Points: We examine postseismic slip following M4‐5 earthquakes using borehole strain dataThe median estimated postseismic moment is between 0.25 and 0.6 times the coseismic momentThe postseismic moment ratio is intermediate between estimates for small and large earthquakes [ABSTRACT FROM AUTHOR]

The records from 59 identical broadband seismic stations located in different regions of the world, made before and after the strong earthquake off Sumatra Island on December 26, 2004, with magnitude M = 9.1, are studied. Oscillations with periods of 40 to 360 s are analyzed. Stations located several hundred kilometers away from each other demonstrate different pulses of seismic noise with periods of 40–80, 80–160, and 160–320 s, which indicates that this effect is connected to local sources in the atmosphere. The exponential growth of the spectral amplitude of noise with elongation of the periods of oscillations corresponds to the theory by A.N. Kolmogorov about local isotropic turbulence in the atmosphere. The level of seismic noise increased twice after the Sumatra earthquake at stations located both in the seismoactive subduction zones and within the platforms. [ABSTRACT FROM AUTHOR]

A seismic array observation across the central focal area of the 2015 Gorkha earthquake was conducted to investigate aftershock distribution and crustal structure. Most aftershocks near Kathmandu were located above the Main Himalayan Thrust (MHT). Earthquake reflection imaging revealed the geometry of the MHT, which lies at ~10‐km depth at 75 km away from the Main Frontal Thrust. We found three areas of seismic velocity variability around the MHT above 15 km depth: (1) a high‐Vp zone where the MHT changes its dip angle from 5° to 13°, coinciding with a local maximum in coseismic slip, (2) a low‐Vp zone showing less coseismic slip, and (3) a high‐Vp zone where coseismic slip decreased further but afterslip occurred. These differences in slip behavior may indicate changes in frictional properties on the fault, which are reflected in the heterogeneity of the velocity structure. Plain Language Summary: On 25 April 2015, the Gorkha earthquake (Mw 7.8) struck central Nepal and resulted in nearly 9,000 fatalities. Destructive earthquakes have occurred repeatedly in the Himalayan region. The Himalayan seismogenic zone is located in the India‐Eurasia plate collision zone where the Indian plate underthrusts the Eurasian plate along the Main Himalayan Thrust. Revealing the crustal structure of the India‐Eurasia plate collision zone is important to constraining the process of earthquake occurrence and the orogenic process. Seismic array observation is an effective tool to investigate the crustal structure. Here, we present the results of seismic array observation across the central focal area of the 2015 Gorkha earthquake, which shows the geometry of the Main Himalayan Thrust and seismic velocity variability along its length. We find a high‐Vp zone which coincides with a large coseismic slip zone (>6 m). A low‐Vp zone shows less coseismic slip. Another high‐Vp zone located in the southern side of the low‐Vp zone corresponds to an area of afterslip. These results connect heterogeneous crustal structure with fault slip behavior and suggest that variability in the seismic properties of the crustal structure around the plate boundary may affect fault slip behavior. Key Points: Source fault geometry of the 2015 Gorkha earthquake can be imaged by using an earthquake reflection imaging methodA high‐Vp zone where the dip angle of the Main Himalayan Thrust changes coincides with the area of maximum coseismic slipHeterogeneous crustal structure around the Main Himalayan Thrust reflects changes in the frictional properties of the fault [ABSTRACT FROM AUTHOR]

We investigate dynamic source parameters of the Mw7.1 Puebla‐Morelos intermediate‐depth earthquake (h = 57 km) of 19 September 2017, which devastated Mexico City. Our simple, elliptical source model, coupled with a new Particle Swarm Optimization algorithm, revealed rupture propagation within the subducted Cocos plate, featuring a high stress drop (Δτ = 14.9±5.6 MPa) and a remarkably low radiation efficiency (ηr = 0.16 ± 0.09). Fracture energy was large (G = (1.04 ± 0.3) × 1016 J), producing a slow dissipative rupture (Vr/Vs = 0.34 ± 0.04) with scaling‐consistent radiated energy (Er = (1.8 ± 0.9)·1015 J) and energy‐moment ratio (Er/M0 = 3.2 × 10−5). About 84% of the available potential energy for the dynamic rupture was dissipated in the focal region, likely producing friction‐induced melts in the fault core of 0.2–1.2 cm width due to heat production (700–1200 °C temperature rise). Such source features seem to be a universal signature of intermediate‐depth earthquakes. Plain Language Summary: Devastation in central Mexico produced by the intermediate‐depth (magnitude 7.1) Puebla‐Morelos earthquake of 19 September 2017 has raised important questions about the seismic hazard in Mexico City, where more than 20 million people live. Probabilistic hazard in the city from intermediate‐depth and shallower subduction events (i.e., as the 1985 quake that killed 15,000 people in the capital) is about the same despite that the first type of earthquakes is much less frequent. Understanding the source process of intermediate‐depth earthquakes has been a major research topic since decades ago because they occur at depths where mechanical considerations for shallow earthquakes are no longer valid. Recent research has led to unexpected conclusions for this kind of events that were thought to be the consequence of fast and energetically efficient rupture processes. Through a novel technique, we investigate the Puebla‐Morelos earthquake to better understand the generating physics of the strong ground motions. We show that the event was extraordinarily slow and inefficient and that this does not contradict the large ground accelerations. More than 84% of the earthquake energy was dissipated in the source region likely producing rock melting in the geological fault hosting the rupture process. Key Points: We performed the dynamic source inversion of the 19 September (Mw7.1) 2017 intermediate-depth Mexican earthquake with a Particle Swarm Optimization algorithmThe event was highly dissipative with a slow rupture propagation and scaling-consistent radiated energyThe temperature rise associated with the specific fracture energy likely produced friction‐induced melts in the fault core [ABSTRACT FROM AUTHOR]

Deployment of cabled stations on the ocean bottom enhances the effectiveness of early warning systems for suboceanic earthquakes in terms of early signal detection and improved accuracy of hypocentre analyses. We investigated strong-motion data at cabled ocean-bottom stations deployed in the source area of the 2011 Tohoku earthquake (M w 9.0) in northeastern Japan. We found a significantly large change in the direct current component in accelerations due to the roll and pitch motions of the cabled stations that are proportional to strong motions. We further found that the roll angle is affected more by the strong motions than the pitch angle owing to the cylindrical shape of the station housing in a long cable. The observed large roll motions caused anomalous displacement waveforms with significantly large amplitudes, which have contributed to the overestimation of magnitude in the two components perpendicular to the cable direction. Applying the scheme to three-component data to estimate real-time magnitude for early warnings in Japan resulted in high-magnitude estimates of M 9.10–9.76 for the 2011 Tohoku earthquake, which are higher than the magnitude saturation and moment magnitude M w 9.0 of the earthquake. Such an overestimation was suppressed when the single-component data along the cable axis direction were used instead, with the resulting magnitude of M 8.47–8.63 almost coinciding with the catalogue magnitude of M JMA 8.4. For other event data that are not affected by the roll and pitch motions, no large systematic difference was found between the magnitudes estimated using the single- and three-component data. We therefore suggest that the use of single-component data could be an effective approach for stable magnitude estimation at cabled ocean-bottom stations for early warnings. [ABSTRACT FROM AUTHOR]

We apply a matched‐filter‐technique to augment the detected events in the time window between the two mainshocks of the 2012 Emilia seismic sequence (Italy), 20 (Mw 6.1) and 29 (Mw 6.0) May. Using well‐located templates, we increase the number of detections from 1,727 to 7,616. This greater detail allows evidencing migrations of seismic events from the nucleation point of the first shock to the second. Repeating earthquakes are also found between the two mainshocks. The seismicity pattern suggests a transient slip acting immediately after the shallow first event, weakening and loading the volume around the deep nucleation point of the 29 May Mw 6.0 earthquake. We interpret migrations and repeaters as the fingerprint of an early afterslip triggered by the first mainshock. By taking into account the earliest repeater we estimate a cumulative slip of approximately 27 cm (Mw 5.7). This value could represent the lower bound of the total released afterslip. Plain Language Summary: To improve our understanding of interactions between subsequent mainshocks, we investigated the spatiotemporal evolution of the seismicity for the 2012 Emilia seismic sequence (Italy) in the time window from 20 to 29 May 2012. We use a technique based on waveform matching to augment the detected earthquakes. From the new catalog, we observe along‐strike and at depth seismic migrations consistent with a phase of rapid postseismic slip concentrated near the base of the seismogenic zone immediately after the first main shock. We suggest that the afterslip contributed to loading the fault rupture area of the 29 May Mw 6.0 earthquake. Key Points: Newly detected early aftershocks suggest a fast migration at depth moving from the 20 May hypocenter to the 29 May nucleation pointRepeating earthquakes have been identified between the two mainshocksMigration and repeaters suggest an afterslip that could have contributed to loading the 29 May focal volume [ABSTRACT FROM AUTHOR]

Over the past 20 years, analyzing the abundance of the isotope chlorine-36 (36Cl) has emerged as a popular tool for geologic dating. In particular, it has been observed that 36Cl measurements along a fault plane can be used to study the timings of past ground displacements during earthquakes, which in turn can be used to improve existing seismic hazard assessment. This approach requires accurate simulations of 36Cl accumulation for a set of fault-scarp rock samples, which are progressively exhumed during earthquakes, in order to infer displacement histories from 36Cl measurements. While the physical models underlying such simulations have continuously been improved, the inverse problem of recovering displacement histories from 36Cl measurements is still mostly solved on an ad hoc basis. The current work resolves this situation by providing a MATLAB implementation of a fast, automatic, and flexible Bayesian Markov-chain Monte Carlo algorithm for the inverse problem, and provides a validation of the 36Cl approach to inference of earthquakes from the demise of the Last Glacial Maximum until present. To demonstrate its performance, we apply our algorithm to a synthetic case to verify identifiability, and to the Fiamignano and Frattura faults in the Italian Apennines in order to infer their earthquake displacement histories and to provide seismic hazard assessments. The results suggest high variability in slip rates for both faults, and large displacements on the Fiamignano fault at times when the Colosseum and other ancient buildings in Rome were damaged. [ABSTRACT FROM AUTHOR]

The Iranian plateau is one of the seismically active areas of the world and frequently suffers destructive and catastrophic earthquakes. A precise and consistent local earthquake catalogue is a prerequisite not only for traditional seismic hazard assessment but also in the understanding of correlation of seismicity with the lithosphere structure and its tectonics. The two national observatories IRSC and BIN, complemented by few local observatories, operate seismic networks and each separately produces a seismic catalogue. Due to differences in the network geometry and in data processing, the two catalogues exhibit significant differences in the event location solutions and, surprisingly, in the number of events, also for strong earthquakes that occurred in recent years. High-quality and consistent seismic catalogues are best established by solving the coupled hypocentre-velocity problem, a fundamental task inherent to seismic tomography. In this work, we present the products of and the procedures for merging routine catalogues and for a consistent semi-automated re-picking of P -wave arrival times from local to regional scale. The final data set consists of more than 25 000 high-quality first P -wave arrivals from 1648 events used to derive a regional minimum 1-D model for northern Iran and four subregional 1-D models in four selected areas. We then used the regional minimum 1-D model with corresponding station delays for all stations operated in northern Iran to establish a combined high-quality local earthquake catalogue with uniformly consistent location and associated uncertainties. Thus the two main products of this study are the regional reference velocity model well suited for routine high-precision hypocentre location and the combined high-quality ReKiNIRAN-17 local earthquake catalogue for the period 2005–2017. [ABSTRACT FROM AUTHOR]

Past seismic events have shown that industrial facilities may suffer greatly from earthquake-induced actions, which can cause simultaneous damages to different key apparatus, initiating major/multiple accidental chains. Therefore, the evaluation of seismic demand acting upon structural systems and equipment is of utmost importance when assessing or designing a complex industrial plant, which will be inevitably exposed to seismic hazards during its lifetime. Furthermore, it is noteworthy that, if modern seismic design procedures are able to successfully limit damage to the main structural elements, the evaluation of secondary structural and non-structural components may imply less trivial considerations because of the important role played by them (e.g. storage of chemical/hazardous substances) and the lack of accurate code-compliant approaches applicable to each specific case. As such, this paper is chiefly concerned with the derivation of floor acceleration spectra for a special concentrically braced frame supporting a cylindrical storage tank, the latter being a basic strategic component widely used in several industrial applications and the former one being one of the most common forms of lateral-force resisting systems for plant structures. Firstly, a fibre-based finite element model of the supporting frame itself was developed within an open source platform and then nonlinear time history analyses were performed assuming a set of 47 natural ground motions scaled to 8 seismic intensities. These results, used to assess the tank as an uncoupled system, were additionally compared with those obtained by a second analysis run, in which the interaction between the supporting structure and the tank was explicitly accounted for by modelling them together. A well-known analytical model, consisting of two uncoupled single degree of freedom systems for the impulsive and convective components of motion, was considered in this case to reproduce the response of the tank. The floor spectra resulting from these two approaches were compared together so as to quantify trends and differences in the observed estimates. Sensitivity to the viscous damping was examined as well. A comparison was finally derived between the nonlinear dynamic analyses of both coupled and uncoupled systems and the analytical methods of current Codes (ASCE 7-10, EC8) and recent research proposals. [ABSTRACT FROM AUTHOR]

The article offers information on the ‘International Virtual Workshop on Global Seismology and Tectonics' was organized to bring national and international experts together and boost the morale of the students and researchers during the COVID- 19 pandemic. Topic include providing opportunities to interact with eminent scientists in the domain of seismology and tectonics.

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]

We demonstrate how effects of induced stress may be incorporated in seismic modelling and inversion. Our approach is motivated by the accommodation of pre-stress in global seismology. Induced stress modifies both the equation of motion and the constitutive relationship. The theory predicts that induced pressure linearly affects the unstressed isotropic moduli with a slope determined by their adiabatic pressure derivatives. The induced deviatoric stress produces anisotropic compressional and shear wave speeds; the latter result in shear wave splitting. For forward modelling purposes, we determine the weak form of the equation of motion under induced stress. In the context of the inverse problem, we determine induced stress sensitivity kernels, which may be used for adjoint tomography. The theory is illustrated by considering 2-D propagation of SH waves and related Fréchet derivatives based on a spectral-element method. [ABSTRACT FROM AUTHOR]

Quantifying the near-surface attenuation of seismic waves at a given location can be important for seismic hazard analysis of high-frequency ground motion. This study calculates the site attenuation parameter, κ0, at 41 seismograph locations in New Zealand. Combined with results of a previous study, a total of 46 κ0 values are available across New Zealand. The results compare well with previous t* studies, revealing high attenuation in the volcanic arc and forearc ranges, and low attenuation in the South Island. However, for site-specific seismic hazard analyses, there is a need to calculate κ0 at locations away from a seismograph location. For these situations, it is common to infer κ0 from weak correlations with the shear wave velocity in the top 30 m, VS30, or to adopt an indicative regional value. This study attempts to improve on this practice. Geostatistical models of the station-specific κ0 data are developed, and continuous maps are derived using ordinary kriging. The obtained κ0 maps can provide a median κ0 and its uncertainty for any location in New Zealand, which may be useful for future site-specific seismic hazard analyses. [ABSTRACT FROM AUTHOR]

We present a seismological technique for determining the down-dip shape of seismogenic normal faults. Synthetic models of non-planar source geometries reveal the important signals in teleseismic P and SH waveforms that are diagnostic of down-dip curvature. In particular, along-strike SH waveforms are the most sensitive to variations in source geometry, and have significantly more complex and larger-amplitudewaveforms for curved source geometries than planar ones. We present the results of our forward-modelling technique for 13 earthquakes. Most continental normal-faulting earthquakes that rupture through the full seismogenic layer are planar and have dips of 30°-60°. There is evidence for faults with a listric shape from some of the earthquakes occurring in two regions; Tibet and East Africa. These ruptures occurred on antithetic faults, or minor faults within the hanging walls of the rifts affected, which may suggest a reason for the down-dip curvature. For these earthquakes, the change in dip across the seismogenic part of the fault plane is ≤30°. [ABSTRACT FROM AUTHOR]

The Bulletin of the International Seismological Centre (ISC) contains information on earthquake mechanisms collected from many different sources including national and global agencies, resulting in a satisfactory coverage over a widemagnitude range (M~2-9). Nevertheless, there are still a vast number of earthquakes with no reported source mechanisms especially for magnitudes up to 5. This study investigates the possibility of calculating earthquake focal mechanisms in a routine and systematic way based on P-wave first motion polarities. Any available parametric data in the ISC database is being used, as well as auto-picked polarities from waveform data up to teleseismic epicentral distances (90°) for stations that are not reported to the ISC. The determination of the earthquake mechanisms is carried out with a modified version of the HASH algorithm that is compatible with a wide range of epicentral distances and takes into account the ellipsoids defined by the ISC location errors, and the Earth's structure uncertainties. Initially, benchmark tests for a set of ISC reviewed earthquakes (mb > 4.5) are carried out and the HASH mechanism classification scheme is used to define the mechanism quality. Focal mechanisms of quality A, B and C with an azimuthal gap up to 90° compare well to the benchmark mechanisms. Nevertheless, the majority of the obtained mechanisms fall into class D as a result of limited polarity data from stations in local/regional epicentral distances. Specifically, the computation of the minimum rotation angle between the obtained mechanisms and the benchmarks, reveals that 41 per cent of the examined earthquakes show rotation angles up to 35°. Finally, the current technique is applied to a small set of earthquakes from the reviewed ISC bulletin where 62 earthquakes, with no previously reported source mechanisms, are successfully obtained. [ABSTRACT FROM AUTHOR]

Local seismic networks are usually designed so that earthquakes are located inside them (primary azimuthal gap <<180°) and close to the seismic stations (0-100 km). With these local or near-regional networks (0°-5°), many seismological observatories still routinely locate earthquakes using 1-D velocity models. Moving towards 3-D location algorithms requires robust 3-D velocity models. This work takes advantage of seismic monitoring spanning more than 30 yr in the Pyrenean region. We investigate the influence of a well-designed 3-D model with station corrections including basins structure and the geometry of the Mohorovicic discontinuity on earthquake locations. In the most favourable cases (GAP < 180° and distance to the first station lower than 15 km), results using 1-D velocity models are very similar to 3-D results. The horizontal accuracy in the 1-D case can be higher than in the 3-D case if lateral variations in the structure are not properly resolved. Depth is systematically better resolved in the 3-D model even on the boundaries of the seismic network (GAP > 180° and distance to the first station higher than 15 km). Errors on velocity models and accuracy of absolute earthquake locations are assessed based on a reference data set made of active seismic, quarry blasts and passive temporary experiments. Solutions and uncertainties are estimated using the probabilistic approach of the NonLinLoc (NLLoc) software based on Equal Differential Time. Some updates have been added to NLLoc to better focus on the final solution (outlier exclusion, multiscale grid search, S-phases weighting). Errors in the probabilistic approach are defined to take into account errors on velocity models and on arrival times. The seismicity in the final 3-D catalogue is located with a horizontal uncertainty of about 2.0 ± 1.9 km and a vertical uncertainty of about 3.0 ± 2.0 km. [ABSTRACT FROM AUTHOR]

This paper proposes a nonmodel-based framework for estimating story-based engineering demand parameters (EDPs) in instrumented steel frame buildings with steel moment-resisting frames (MRFs). The proposed framework utilizes a wavelet-based damage-sensitive feature and basic building geometric information to infer the building damage state at a given seismic intensity. The story-based EDPs are predicted with a reasonable accuracy compared to those predicted from rigorous nonlinear response history analyses that typically require the explicit use of a nonlinear building model. The efficiency of the proposed framework is demonstrated through a number of illustrative examples including actual instrumented steel frame buildings that experienced the 1994 Northridge earthquake in Los Angeles. It is shown that if the building content is known the proposed framework can facilitate building-specific seismic risk and loss assessment within minutes after an earthquake provided that the recorded floor absolute acceleration histories at discrete locations along the height of the building are accessible. The nonmodel-based framework is also extended at the city-scale through the development of generalized earthquake-induced damage and loss maps for the same earthquake event. The same framework can facilitate the decision-making for effective pre-disaster measures for earthquake disaster risk management of building assets. [ABSTRACT FROM AUTHOR]

The seismic activities and hazards in People's Democratic Republic Laos were analyzed using the most up-to-date seismicity data. Both the a- and b-values of the frequency-magnitude distribution model, including the return period of earthquake magnitude in the range of 5.0 - 6.0 Mw, were evaluated spatially in a region that extends 300 km from Laos. Six seismic source zones with different seismic activities were found. Based on these seismic source zones and a suitable attenuation model, seismic hazards were then analyzed in both deterministic and probabilistic scenarios. The deterministic map showed a possible maximum ground shaking up to 0.4 g in Northern Laos, whereas the ground shaking calculated from the probabilistic approach was < 0.32 g for 2% probability of exceedance in the next 50 yr. The probability of exceedance of an earthquake with a Modified Mercalli intensity scale of level IV - V, VI and VII in Laos in the next 50 yr was > 90, 70 - 90, and 20 - 40%, respectively, and was higher in the northern part. From these seismic activities and hazard analyses, Laos can be clearly separated into the three hazard zones of northwestern, northeastern and southern Laos with a high, medium and low earthquake hazard, respectively. Therefore, effective mitigation plans to reduce the impact of seismic hazards should be formulated and in particular for a number of major provinces located in the northern part of Laos. [ABSTRACT FROM AUTHOR]

We utilize L-band interferometric synthetic aperture radar (InSAR) data in this study to retrieve a ground velocity map for the near field of the Ganos section of the north Anatolian fault (NAF) zone. The segmentation and creep distribution of this section, which last ruptured in 1912 to generate a moment magnitude (Mw)7.3 earthquake, remains incompletely understood. Because InSAR processing removes the mean orbital plane, we do not investigate large scale displacements due to regional tectonics in this study as these can be determined using global positioning system (GPS) data, instead concentrating on the close-to-the-fault displacement field. Our aim is to determine whether, or not, it is possible to retrieve robust near field velocity maps from stacking L-band interferograms, combining both single and dual polarization SAR data. In addition, we discuss whether a crustal velocity map can be used to complement GPS observations in an attempt to discriminate the present-day surface displacement of the Ganos fault (GF) across multiple segments. Finally, we characterize the spatial distribution of creep on shallow patches along multiple along-strike segments at shallow depths. Our results suggest the presence of fault segmentation along strike as well as creep on the shallow part of the fault (i.e. the existence of a shallow creeping patch) or the presence of a smoother section on the fault plane. Data imply a heterogeneous fault plane with more complex mechanics than previously thought. Because this study improves our knowledge of the mechanisms underlying the GF, our results have implications for local seismic hazard assessment. [ABSTRACT FROM AUTHOR]

A topic of seismic hazard analysis (SHA) is briefly elaborated. A probabilistic seismic hazard analysis (PSHA) is commonly used to assess the ground motion level expected with different likelihood at a rock site during a future seismic event. The Incorporating Monte Carlo method into PSHA in an intraplate region (i.e. Adelaide region) is an interesting topic to explore. The result of the analysis using this method is able to characterize the likelihood of seismicity in a targeted region. Furthermore, the results clearly display the seismic ground motions in term of peak ground acceleration and peak ground velocity in Adelaide region. The de-aggregation of the analysis suggests two expected severe events for the Adelaide City. The first expected event is an earthquake M5.2 from a distance of 15 km and 25 km from the city. The second expected one corresponds to an earthquake M6.6 occurring 85 km away from the Adelaide City. However, the results of this analysis must be treated carefully due to dubious seismic data catalogue for a relatively large seismic event in Adelaide region. [ABSTRACT FROM AUTHOR]

The Himalayan collision zone experiences many seismic activities with large earthquakes occurring at certain time intervals. The damming of the proto-Bagmati River as a result of rapid mountain-building processes created a lake in the Kathmandu Valley that eventually dried out, leaving thick unconsolidated lacustrine deposits. Previous studies have shown that the sediments are ~600 m thick in the center. A location in a seismically active region, and the possible amplification of seismic waves due to thick sediments, have made Kathmandu Valley seismically vulnerable. It has suffered devastation due to earthquakes several times in the past. The development of the Kathmandu Valley into the largest urban agglomerate in Nepal has exposed a large population to seismic hazards. This vulnerability was apparent during the Gorkha Earthquake (Mw7.8) on April 25, 2015, when the main shock and ensuing aftershocks claimed more than 1700 lives and nearly 13% of buildings inside the valley were completely damaged. Preparing safe and up-to-date building codes to reduce seismic risk requires a thorough study of ground motion amplification. Characterizing subsurface velocity structure is a step toward achieving that goal. We used the records from an array of strong-motion accelerometers installed by Hokkaido University and Tribhuvan University to construct 1-D velocity models of station sites by forward modeling of low-frequency S-waves. Filtered records (0.1-0.5 Hz) from one of the accelerometers installed at a rock site during a moderate-sized (mb4.9) earthquake on August 30, 2013, and three moderate-sized (Mw5.1, Mw5.1, and Mw5.5) aftershocks of the 2015 Gorkha Earthquake were used as input motion for modeling of low-frequency S-waves. We consulted available geological maps, cross-sections, and borehole data as the basis for initial models for the sediment sites. This study shows that the basin has an undulating topography and sediment sites have deposits of varying thicknesses, from 155 to 440 m. These models also show high velocity contrast at the bedrock depth which results in significant wave amplification. [ABSTRACT FROM AUTHOR]

In countries where best-practice probabilistic hazard studies and seismic monitoring networks are available, there is increasing interest in direct validation of hazard maps. It usually means trying to quantitatively understand whether probabilities estimated via hazard analysis are consistent with observed frequencies of exceedance of ground motion intensity thresholds. Because the exceedance events of interest are typically rare with respect to the time span covered by data from seismic networks, a common approach underlying these studies is to pool observations from different sites. The main reason for this is to collect a sample large enough to convincingly performa statistical analysis. However, this requires accounting for the dependence among the stochastic processes counting exceedances of ground motion intensity measures thresholds at different sites. Neglecting this dependence may lead to potentially fallacious conclusions about inadequateness of probabilistic seismic hazard. This study addresses this issue revisiting a hazard validation exercise for Italy, showing that accounting for this kind of spatial dependence can change the results of formal testing. [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]

Preliminary work on the creation of a method for monitoring of seismic activity, on the basis of discrete mathematical analysis for further seismic hazard assessment of a territory, is presented. The method developed is tested for the territory of California and adjacent areas of the United States. The results obtained are analyzed for the period of 1980-2015. The nonrandomness of the results is shown by means of an error chart. [ABSTRACT FROM AUTHOR]

The catastrophic Wulong landslide occurred at 14:51 (Beijing time, UTC+8) on 5 June 2009, in Wulong Prefecture, Southwest China. This rockslide occurred in a complex topographic environment. Seismic signals generated by this event were recorded by the seismic network deployed in the surrounding area, and long-period signals were extracted from 8 broadband seismic stations within 250 km to obtain source time functions by inversion. The location of this event was simultaneously acquired using a stepwise refined grid search approach, with an error of ~2.2 km. The estimated source time functions reveal that, according to the movement parameters, this landslide could be divided into three stages with different movement directions, velocities, and increasing inertial forces. The sliding mass moved northward, northeastward and northward in the three stages, with average velocities of 6.5, 20.3, and 13.8 m/s, respectively. The maximum movement velocity of the mass reached 35 m/s before the end of the second stage. The basal friction coefficients were relatively small in the first stage and gradually increasing; large in the second stage, accompanied by the largest variability; and oscillating and gradually decreasing to a stable value, in the third stage. Analysis shows that the movement characteristics of these three stages are consistent with the topography of the sliding zone, corresponding to the northward initiation, eastward sliding after being stopped by the west wall, and northward debris flowing after collision with the east slope of the Tiejianggou valley. The maximum movement velocity of the sliding mass results from the largest height difference of the west slope of the Tiejianggou valley. The basal friction coefficients of the three stages represent the thin weak layer in the source zone, the dramatically varying topography of the west slope of the Tiejianggou valley, and characteristics of the debris flow along the Tiejianggou valley. Based on the above results, it is recognized that the inverted source time functions are consistent with the topography of the sliding zone. Special geological and topographic conditions can have a focusing effect on landslides and are key factors in inducing the major disasters, which may follow from them. This landslide was of an unusual nature, and it will be worthwhile to pursue research into its dynamic characteristics more deeply. [ABSTRACT FROM AUTHOR]

This paper presents an application of a methodology for the seismic vulnerability reduction of masonry towers by reversible prestressing. The approach is applied on a medieval tower located in San Gimignano , Italy, which is considered as a world heritage site. The 3D FE models are calibrated with experimental data and assessed by nonlinear static analyses including the seismic demand of the site and an accurate validated masonry model. The vertical prestressing is applied at key points identified in the seismic vulnerability assessment. This technique is in compliance with the demand for architectural conservation because it may be fully reversible. The seismic performance is enhanced by increasing force, displacement and internal confinement. It is observed at ultimate limit conditions an upgrading of 14.3% of displacement with the medium prestressing level and 9.5% with the high level. The results are analyzed and discussed in terms of earthquake energy dissipation and failure mechanisms. [ABSTRACT FROM AUTHOR]

The objective of the investigation is to evaluate the engineering and geological conditions of the soils in Caimanera, province of Guantanamo in order to identify the areas of higher seismic probabilities and soil susceptibility to liquefaction. The probability was analyzed to amplify the seismic waves taking into account the effect of the area depending on the physical and mechanical properties in the area of study. The sectors having favorable and unfavorable conditions for the construction of engineering works were characterized. The applied indicator system includes engineering and geological parameters and the calculation of the safety factor for liquefaction. It was concluded that the soils having a greater potential to liquefy are located to the center of the city with the largest population settlement and where the existing fill material behaves as clayey sand type soils and sandy clay soils with gravel. [ABSTRACT FROM AUTHOR]

Spatio-temporal variations of seismicity within 300 km of the main Nepal earthquake of 25 April 2015 showed seismic quiescence since 2007. Decadal changes inb-value using the Gutenberg–Richter relation showed a well-marked decrease during the period January 2005–April 2015 preceding the main earthquake. Stress drop of this earthquake in the inter plate region was found to be 3.4 MPa which is much lower than the intra plate Bhuj earthquake, 2001. The un-ruptured portion of the seismic gap in western Nepal lies between longitude 82.5°E and 84.5°E, whose 200 km length (if assumed to rupture entirely in one earthquake) coupled with locked zone of about 100 km from GPS data, may generate an earthquake of magnitude about 8 although no historical data for a major earthquake is as yet available. [ABSTRACT FROM AUTHOR]

The creation of a magnitude-homogenized catalogue is often one of the most fundamental steps in seismic hazard analysis. The process of homogenizing multiple catalogues of earthquakes into a single unified catalogue typically requires careful appraisal of available bulletins, identification of common events within multiple bulletins and the development and application of empirical models to convert from each catalogue's native scale into the required target. The database of the International Seismological Center (ISC) provides the most exhaustive compilation of records from local bulletins, in addition to its reviewed global bulletin. New open-source tools are developed that can utilize this, or any other compiled database, to explore the relations between earthquake solutions provided by different recording networks, and to build and apply empirical models in order to harmonize magnitude scales for the purpose of creating magnitude-homogeneous earthquake catalogues. These tools are described and their application illustrated in two different contexts. The first is a simple application in the Sub-Saharan Africa region where the spatial coverage and magnitude scales for different local recording networks are compared, and their relation to global magnitude scales explored. In the second application the tools are used on a global scale for the purpose of creating an extended magnitude-homogeneous global earthquake catalogue. Several existing high-quality earthquake databases, such as the ISC-GEM and the ISC Reviewed Bulletins, are harmonized into moment magnitude to form a catalogue of more than 562 840 events. This extended catalogue, while not an appropriate substitute for a locally calibrated analysis, can help in studying global patterns in seismicity and hazard, and is therefore released with the accompanying software. [ABSTRACT FROM AUTHOR]

Recent improvement to Advanced Differential Interferometric SAR (A-DInSAR) time series quality enhances the knowledge of various geohazards. Ground motion studies need an appropriate methodology to exploit the great potential contained in the A-DInSAR time series. Here, we propose a methodology to analyze multi-sensors and multi-temporal A-DInSAR data for the geological interpretation of areas affected by land subsidence/uplift and seasonal movements. The methodology was applied in the plain area of the Oltrepo Pavese (Po Plain, Italy) using ERS-1/2 and Radarsat data, processed using the SqueeSAR™algorithm, and covering time spans, respectively, from 1992 to 2000 and from 2003 to 2010. The test area is a representative site of the Po Plain, affected by various geohazards and characterized by moderate rates of motion, ranging from ??10 to 4 mm/yr. Different components of motion were recognized: linear, non-linear, and seasonal deformational behaviors. Natural and man-induced processes were identified such as swelling/shrinkage of clayey soils, land subsidence due to load of new buildings, moderate tectonic uplift, and seasonal ground motion due to seasonal groundwater level variations. [ABSTRACT FROM AUTHOR]

Recent advances in computing have brought a new and challenging way to tackle the earthquake hazard and disaster problems: integration of the seismic actions in the form of numerical models. For this purpose, integrated earthquake simulation (IES) has been developed in Japan, and now a new version is being developed in Turkey which targets Istanbul. This version of IES is being built in MATLAB and includes site response analysis and structural analysis of existing buildings with data obtained via GIS databases. In this study, we present an initial application in Zeytinburnu district of Istanbul where the results are expressed in the form of spatial distributions of ground motion and building responses. At the end of the analysis, it is seen that most of the buildings make small displacements and the displacement values are directly proportional to the total height of the structures. Since the obtained ground motion distribution and peak values are not very high, structural damage has not been observed under the current simulation. The effect of bedrock depth and soil parameters on strong ground motion distribution has been observed. The most effective ground motion locations in the selected area have been determined, and the critical buildings that have maximum displacement during the earthquake motion are detected. Currently, the IES on MATLAB does not include the source to bedrock wave propagation mechanism and the resulting ground motions at each grid point. In future studies, alternative models for this purpose along with input model parameters for Istanbul will be applied. Once the source-to-structure integrated model is complete, past earthquakes as well as potential scenario events in Istanbul will be modeled in the final form of IES on MATLAB. Results will be valuable for a variety of purposes ranging from disaster mitigation to emergency management. In future part of this study, site vibration tests will also be made for buildings that do not comply with seismic design codes and constitute the largest portion of the seismic risk. New models will be developed for these buildings and adopted into the IES system. [ABSTRACT FROM AUTHOR]

The Taiwan Earthquake Model (TEM) was established to assess the seismic hazard and risk for Taiwan by considering the social and economic impacts of various components from geology, seismology, and engineering. This paper gives the first version of TEM probabilistic seismic hazard analysis for Taiwan in these aspects. We named it TEM PSHA2015. The model adopts the source parameters of 38 seismogenic structures identified by TEM geologists. In addition to specific fault source-based categorization, seismic activities are categorized as shallow, subduction intraplate, and subduction interplate events. To evaluate the potential ground-shaking resulting from each seismic source, the corresponding ground-motion prediction equations for crustal and subduction earthquakes are adopted. The highest hazard probability is evaluated to be in Southwestern Taiwan and the Longitudinal Valley of Eastern Taiwan. Among the special municipalities in the highly populated Western Taiwan region, Taichung, Tainan, and New Taipei City are evaluated to have the highest hazard. Tainan has the highest seismic hazard for peak ground acceleration in the model based on TEM fault parameters. In terms of pseudo-spectral acceleration, Tainan has higher hazard over short spectral periods, whereas Taichung has higher hazard over long spectral periods. The analysis indicates the importance of earthquake-resistant designs for low-rise buildings in Tainan and high-rise buildings in Taichung. [ABSTRACT FROM AUTHOR]

Empirical magnitude conversion relationships are one of the important parameters for not only seismological studies but also seismic hazard analysis and development of the attenuation relationships. Particularly, for seismic hazard analysis, conversion of various types of magnitudes to moment magnitude, which is the most reliable and common magnitude scale, is a key requirement. Within this scope, different magnitude conversion equations have been derived by various researchers in the literature. In this study, new empirical magnitude conversion formulas for conversion from mb, ML, Md, and MS to Mw were derived by using a recently established earthquake catalogue. The most important feature of the new relationships is the use of the maximum data with respect to the literature. It is a well-known fact that having a greater number of data increases the sensitivity of the equations derived. Both orthogonal regression (OR) and ordinary least squares (OLS) were used to derive conversion equations, and the results obtained from these two methods were compared. In the derivation, 489 events with magnitudes in Mw scale taken from the Harvard GCMT Catalogue were used. Residual graphs created for both methods showed that the OR method gives better results than OLS for conversion from MS to Mw. On the other hand, the OLS method showed preferable performance for conversions from mb, ML, and Md to Mw. The equations proposed in this study were also compared with other empirical relations in the literature. [ABSTRACT FROM AUTHOR]

This study aims the relations between seismicity data and strain analysis based on geodetic space techniques in order to define the seismicity hazard of the southwest Anatolian region of Turkey. This region has complex tectonic formations and requires sophisticated techniques and approaches to investigate seismic activities. In this study, global navigation satellite system (GNSS) observations were used to determine the velocity field of the region. The strain rates of the region were obtained from the evaluation of this velocity field. In addition, seismicity b parameters of the region were calculated from the analysis of seismicity data. Furthermore, the seismicity data and the geodetic strain rates obtained from the GNSS observations were combined to show the statistical correlation. This correlation was interpreted to define the seismicity. According to the results derived from the correlation analysis, the geodetic strain analysis and seismicity data were highly and inversely correlated (r = −0.96). After the determination of the correlation, the seismic hazard data of the region was added to the analysis. This process shows that seismic hazards are highly and negatively correlated to seismicity data (r = −0.90), even though they are highly but positively correlated to geodetic strain analysis (r = 0.88). [ABSTRACT FROM AUTHOR]

Large earthquakes sometimes trigger local seismicity that is distal to their rupture zones. Various mechanisms for this triggered seismicity have been proposed, based on either the static stress change or ground shaking from seismic waves, but local geological structure is rarely studied to discern why this seismicity is remotely induced. We present the results of a joint three-dimensional resistivity and isotopic analysis of the groundwater system surrounding Mount Fuji, Japan, where increased seismicity was observed following the A.D. 2011 Tohoku- Oki megathrust earthquake. An electrically conductive zone and high concentrations of magmatic gases (He and CO2) correspond to the zone of triggered seismicity. In contrast, a contribution of magmatic water is not suggested from ²H (deuterium, D) and 18O isotope ratios. These results suggest that the earthquakes were triggered within a fractured zone through which magmatic gases preferentially migrated. We hypothesize that the upwelling of gas-rich hydrous fluids and/or gas bubbles occurred along this fracture pathway, causing an increase in the pore pressure and triggering the resultant earthquake sequence. [ABSTRACT FROM AUTHOR]

Seismic hazard evaluations require an estimate of the expected ground motion at the site of interest usually by using attenuation relationships. The mean shear-wave velocity over the top 30 m (Vs30) is incorporated in the ground motion attenuation relationships in this study. By comparing the standard deviations of the residuals between the observed and predicted values before and after incorporating the site effect term Vs30, the reduction in standard deviation for the peak ground velocity (PGV) is significantly reduced by about 11%. Clearly, the refined attenuation relationships will be more useful for engineering purposes. Analyzing the site effect term using the amplification factor (relative to a site with Vs30 = 760 m s-1), has revealed that the Changhua Plain, Chianan Plain, Pingtung Valley, Ilan Plain, and Taipei Basin have high values, implying large ground motion amplification. Following a disastrous earthquake, quick assessment and timely peak ground acceleration (PGA) and PGV map reporting will be critical for effective emergency response operations. After an earthquake we can combine the simple attenuation relationships, as determined from Model 1, to provide near real-time estimation and reporting of the PGA and PGV values for the Taiwan area. We can also use the relations between the intra-event site residual and the Vs30 to estimate the Vs30 for stations that have recorded strong motions, but do not yet have Vs30 information. Our approach including sites with estimated Vs30 has resulted in a refined Vs30 contour map that can be used for more realistic seismic hazard assessment for Taiwan. This approach is especially applicable to the foothill and mountain areas. [ABSTRACT FROM AUTHOR]

We map the complete surface deformation of 2015 Mw 7.8 Gorkha Nepal earthquake and its Mw 7.3 aftershock with two parallel ALOS2 descending ScanSAR paths' and two ascending Stripmap paths' images. The coseismic fault-slip model from a combined inversion of InSAR and GPS data reveals that this event is a reverse fault motion, with a slight right-lateral strikeslip component. The maximum thrust-slip and right-lateral strike-slip values are 5.7 and 1.2 m, respectively, located at a depth of 7-15 km, southeast to the epicentre. The total seismic moment 7.55 × 1020 Nm, corresponding to a moment magnitude Mw 7.89, is similar to the seismological estimates. Fault slips of both the main shock and the largest aftershock are absent from the upper thrust shallower than 7 km, indicating that there is a locking lower edge of Himalayan Main Frontal Thrust and future seismic disaster is not unexpected in this area. We also find that the energy released in this earthquake is much less than the accumulated moment deficit over the past seven centuries estimated in previous studies, so the region surrounding Kathmandu is still under the threaten of seismic hazards. [ABSTRACT FROM AUTHOR]

Recent earthquakes that have struck Italian territory have emphasized the necessity to assess the seismic safety of the existing built heritage, comprising, for a substantial part, Reinforced Concrete (RC) buildings designed between the 50 s and 80 s. Those buildings were designed in accordance with regulations that, although showing a growing seismic awareness, were certainly inadequate to design buildings capable to withstand the design earthquakes prescribed by the more recent Italian Technical Standards for Constructions (NTC 2008). At the same time, the recent proposal made by the technical community to equip each existing building with a seismic suitability certificate encourages the development of a rapid method for seismic safety assessment. This paper presents a method to carry out a simplified and fast non-linear static seismic assessment of an existing RC building. This method is based on: (a) the selection of the RC elements that, based on engineering judgment, are expected to be the most vulnerable ones, and on (b) the subsequent evaluation of the structure displacement capacity corresponding to their failure. Simple and conservative plane structural models are proposed to carry out such evaluations. With the aim to appraise its potentialities, the proposed procedure is also applied to some RC buildings whose experimental and numerical results were published in the latest scientific literature. Strengths, weaknesses and possible further developments are highlighted. [ABSTRACT FROM AUTHOR]