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The primary goal of this paper is to discuss an integrated approach to efficiently obtaining earthquake damage information. We developed a framework to rapidly obtain earthquake damage information using post-earthquake airborne optical images. The framework is a standard process that includes data selection, preprocessing, damage factor identification, damage factor evaluation and the development of an earthquake damage information map. We can obtain damage information on severely affected regions using this framework, which will aid in planning rescue and rehabilitation efforts following disasters. We used the integrated approach to obtain damage information using the Lushan earthquake (magnitude 7.0, 20 April 2013) as a case study. The result were as follows: (1) 644 collapsed buildings and 4599 damaged buildings accounted for 13.90% and 96.24%, respectively, of the total number of buildings in the study area; (2) 334 landslides (total area of 691,674.5 m2) were detected and were found at greater probabilities at elevations of 1400–1500 m and higher slope; (3) no secondary disasters, such as barrier lakes, were detected; (4) 15 damaged sections (total of 306 m) were detected in the lifelines, and road sections that are at a high risk of damage (total of 2.4 km) were identified; and (5) key structures, including Yuxi River Dam and three bridges, were intact. Integrating the earthquake damage factor information generated a comprehensive Lushan earthquake damage information map. The integrated approach was proven to be effective using the Lushan earthquake as a case study and can be applied to assess earthquake damage to facilitate efficient rescue efforts. [ABSTRACT FROM AUTHOR]

The 3 August 2014 Ludian earthquake with a moment magnitude scale (Mw) of 6.1 induced widespread landslides in the Ludian County and its vicinity. This paper presents a preliminary analysis of the distribution patterns and characteristics of these co-seismic landslides. In total, 1826 landslides with a total area of 19.12 km² triggered by the 3 August 2014 Ludian earthquake were visually interpreted using high-resolution aerial photos and Landsat-8 images. The sizes of the landslides were, in general, much smaller than those triggered by the 2008Wenchuan earthquake. The main types of landslides were rock falls and shallow, disrupted landslides from steep slopes. These landslides were unevenly distributed within the study area and concentrated within an elliptical area with a 25-km NW-SE striking long axis and a 15-km NW-SE striking short axis. Three indexes including landslides number (LN), landslide area ratio (LAR), and landslide density (LD) were employed to analyze the relation between the landslide distribution and several factors, including lithology, elevation, slope, aspect, distance to epicenter and distance to the active fault. The results show that slopes consisting of deeply weathered and fractured sandstones and mudstones were the more susceptible to co-seismic landslides. The elevation range of high landslide susceptibility was between 900-1300 m and 1800-2000 m. There was a generally positive correlation between co-seismic landslides and slope angle, until a maximum for the slope class 40°-50°. The co-seismic landslides occurred preferably on Southeast (SE), South (S) and Southwest (SW) oriented slopes. Results also show that the landslide concentration tends to decrease with distance from the surface projection of the epicenter rather than the seismogenic fault, and the highest landslide concentration is located within a 5-6 km distance of the seismogenic fault. Regarding the epicenter, the largest landslide clusters were found on the SE, northeast by east (NEE) and nearlyWest (W) of the epicenter. In addition, we also suggest that statistical results of slope gradients of landslides might imply a threshold topography of the study area within a tectonically active background. By analogy with other events, the statistical results of landslides aspects also imply the seismogenic fault of the Ludian earthquake might have been the Northwest (NW)-trending fault, which is consistent with other studies. [ABSTRACT FROM AUTHOR]

The shifting correlation method (SCM) is proposed for statistical analysis of the correlation between earthquake sequences and electromagnetic signal sequences. In this method, the two different sequences were treated in units of 1 day. With the earthquake sequences fixed, the electromagnetic sequences were continuously shifted on the time axis, and the linear correlation coefficients between the two were calculated. In this way, the frequency and temporal distribution characteristics of potential seismic electromagnetic signals in the pre, co, and post-seismic stages were analyzed. In the work discussed in this paper, we first verified the effectiveness of the SCM and found it could accurately identify indistinct related signals by use of sufficient samples of synthetic data. Then, as a case study, the method was used for analysis of electromagnetic monitoring data from the Minxian-Zhangxian M 6.5 ( M 6.1) earthquake. The results showed: (1) there seems to be a strong correlation between earthquakes and electromagnetic signals at different frequency in the pre, co, and post-seismic stages, with correlation coefficients in the range 0.4-0.7. The correlation was positive and negative before and after the earthquakes, respectively. (2) The electromagnetic signals related to the earthquakes might appear 23 days before and last for 10 days after the shocks. (3) To some extent, the occurrence time and frequency band of seismic electromagnetic signals are different at different stations. We inferred that the differences were related to resistivity, active tectonics, and seismogenic structure. [ABSTRACT FROM AUTHOR]

The paper presents the framework and outcomes of a Joint Research Project between NIRD URBAN-INCERC, Bucharest, Romania and IEM Harbin, P. R. of China with the topic "Evaluation and Investigation of Seismic Risk Reduction Solutions for Buildings, Before and After Earthquakes". The Project "RISKSOLVE" aimed at an exchange of information between experts from Romania and P.R. of China on legal framework for seismic design of buildings, seismic risk reduction and disaster prevention in each country. The study of sites with seismic risk, processing and evaluating the strong motion recordings was associated with the study of earthquake resistance and behaviour of building systems, correlation of damaged buildings patterns, properties and characteristics of materials and seismic site conditions. On the other hand, the design code solutions, as well as adequate retrofitting methods and construction details were evaluated, based on dynamic - seismic and static experimental tests on chosen solutions. The counterparts obtained promising results and information, useful to earthquake engineering researchers, in view of achievement of top scientific and technological results and future cooperation Romania - China. [ABSTRACT FROM AUTHOR]

This paper examines seismo-ionospheric anomalies (SIAs) observed by the French satellite DEMETER (Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions) during the 12 May 2008 M8.0 Wenchuan earthquake. Both daytime and nighttime electron density (Ne), electron temperature (Te), ion density (Ni) and ion temperature (Ti) are investigated. A statistical analysis of the box-and-whisker method is utilized to see if the four DEMETER datasets 1–6 days before and after the earthquake are significantly different. The analysis is employed to investigate the epicenter and three reference areas along the same magnetic latitude discriminating the SIAs from global effects. Results show that the nighttime Ne and Ni (daytime Ti) over the epicenter significantly decrease (increase) 1–6 days before the earthquake. The intersections of the global distribution of the significant differences (or anomalous changes) in the nighttime Ne, the nighttime Ni, and the daytime Ti 1–6 days before and after the earthquake specifically appear over the epicenter, which strongly suggests that DEMETER observes SIAs of the 2008 M8.0 Wenchuan earthquake. [ABSTRACT FROM AUTHOR]

This paper is the second part of a new geohazards analysis applied to a large part of the Tien Shan, Central Asia, focused on landslide susceptibility computations that are based on recently compiled geographic, geological and geomorphological data. The core data are a digital elevation model, an updated earthquake catalogue, an active fault map as well as a new landslide inventory. The most recently added digital data are a new simplified geological map, an annual precipitation map, as well as river and road network maps that were produced for the Kyrgyz and Tajik parts of the Tien Shan. On the basis of these records we determine landslide densities with respect to morphological (M), geological (G), river distance (R), precipitation (P), earthquake (E) and fault (F) distance factors. Correlations were also established between scarp locations and the slope angle, distance to rivers, curvature. These correlations show that scarps tend to be located on steeper slopes, farther from rivers and on more convex terrain than the entire landslides. On the basis of the landslide density values computed for each class of the aforementioned factors, two landslide susceptibility maps are created according to the Landslide Factor analysis: the first one considers correlations between the landslide occurrences and the first four factors (MGRP); the second one is based on the first map (MGRP) combined with the seismo-tectonic influence (+ E + F) on landslide distributions. From the comparison of these two maps with actual landslide distributions we infer that the distances to rivers as well as to faults and past earthquakes most strongly constrain the susceptibility of slopes to landslides. We highlight several zones where the landslide susceptibilities computed for the MGRP + E + F factors fit better the observed concentration of landslides than those computed for the MGRP factors alone. For a few zones, both maps produce high landslide susceptibilities that do not well reflect the observed low sub-regional landslide activity; for some cases, we consider that some influencing factors must not have been well taken into consideration, for others we show that we simply had missed landslide detections. At the scale of the mountain range, the computed landslide susceptibility maps fit the observed landslide distributions relatively well, but these maps only represent the spatial component of landslide hazards. Temporal aspects are not considered by this analysis. [ABSTRACT FROM AUTHOR]

Due to the fact that escape panics are unexpected and dangerous, which excludes real-life experiments because of technical difficulties and ethical reasons, the evacuation simulations in real-life disasters are still rare. In this paper, the escape panics of classroom evacuation in real-life 2013 Ya’an earthquake in China are simulated and reproduced using the social force model. Firstly, a robust differential evolution (DE) is employed to calibrate and optimize the parameters of social force model to achieve a desired nonlinear evacuation speed which is consistent with real-life video data. It is demonstrated the DE-calibrated social force model can reproduce the characteristics of pedestrian flow in the real-life earthquake evacuation including the nonlinear evacuation speed curve and the pedestrian position distributions at different time. Moreover, the trained evacuation leader has remarkable impact on the evacuation process which can be beneficial to maintain the calm and order of crowd, decrease the desired velocity of crowd, and thus avoid fatal accident to the most degree. Finally, different layouts of classroom have similar evacuation efficiency because different internal layouts can only change partial flow of pedestrians in the left and right corridors, and total flow aggregating in the exit of classroom is still unchanged. However, total evacuation time can be sharply reduced to 17 s from above 36 s, and evacuation efficiency has almost doubled when the back door is open, which means we should try to keep all the emergency exits open in order to provide the crowd with more chances to escape when disasters occur. [ABSTRACT FROM AUTHOR]

An enormous earthquake hit Wenchuan County in Sichuan province of China on May 12, 2008. Since that time, we have worked together with the local community, implementing an alternative model of community development. This is an action research project that devoted to post-disaster community rebuilding, which not only restores local livelihoods but also creates sustainable economic development. This paper examines our role in disaster intervention, the theoretical background of new model, and the process of the intervention itself. [ABSTRACT FROM AUTHOR]

The Da’an-Dedu Fault Zone is a major tectonic feature cutting through the Songliao Basin from south to north in NE China. Five earthquakes with magnitudes over 5 that occurred during the past 30 years suggest the fault zone is a seismogenic structure with future seismic potential. The structural pattern, tectonic history, Quaternary activity and seismic potential have previously been unknown due to the Quaternary sedimentary coverage and lack of large historic earthquakes ( M > 7). In this paper, we use seismic reflection profiles and drilling from petroleum explorations and shallow-depth seismic reflections to study those problems. The total length of the Da’an-Dedu Fault Zone is more than 400 km; modern seismicity delineates it into 4 segments each with a length of 90–100 km. In cross-section view, the folds and associated faults form a complex structural belt with a width of more than 10 km. Shallow-level seismic reflection across the Da’an-Dedu Fault Zone reveals that the Late Quaternary sediments were folded and faulted, indicating its present tectonic activity. The Da’an-Dedu Fault Zone and Songliao Basin have been subjected to three stages of tectonic evolution: a rifting stage characterized by normal faulting and extension (∼145–112 Ma), a prolonged stage of thermal subsidence (∼112–65 Ma), and a tectonic reversal that has been taking place since ∼65 Ma. Our shallow-level reflection profiles show that the folding and reverse faulting have influenced the Late Quaternary sediments. The seismicity and moderate earthquakes suggest that the tectonic activity persists today. The deformation rate across the Da’an-Dedu Fault Zone, however, is measured to be very slow. In conjunction with the inference that most deformation in NE China may be taken up by the Yilan-Yitong Fault Zone bounding the Songliao Basin to the east, we suggest moderate earthquake potential and thus moderate seismic hazards along the Da’an-Dedu Fault Zone. The geological structures, which include anticlines and reverse faults, imply that the Da’an-Dedu Fault Zone has been a contractive structure since ∼65 Ma, and this type of contraction dominates the tectonic deformation in the Songliao Basin and the entire NE China, although the reasons for these conditions need to be further studied. [ABSTRACT FROM AUTHOR]

On April 20, 2013, a Mw 6.6 earthquake struck Lushan County of Sichuan Province, China, about 80 km southwest of the epicenter of the 12 May 2008 Wenchuan Mw 7.9 event. It triggered a large number of landslides in a broad area, causing causality and injuries and damages to roads, drains, dwellings, and infrastructures. Field investigations of coseismic landslides provide a basis for better understanding and illustrating the spatial distributions and hazards related to the Lushan earthquake-triggered landslides. Therefore, this paper presents results of field investigations of the Lushan earthquake-triggered landslides, which can be classified into two main categories of disrupted landslides and coherent landslides, and constitutes seven types. The disrupted landslides include five types: rock falls, rock slides, rock avalanches, soil falls, and soil slides; and the coherent landslides have two types: soil slumps and slow earth flows. All of the seven types of landslides can be observed in many field photos, aerial photographs, and/or satellite images. Among them, seven typical large-scale landslides, distributed in a northeast trending line consistent with the Shuangshi-Dachuan fault, which is presumably related with the earthquake, are described in detail. We prepared an original, emergency-based coseismic landslide inventory map based on visual interpretation of available post-earthquake aerial photographs and pre-earthquake satellite images, combined with results from emergency-based field investigations. The original inventory map registered 3884 landslides. Later, 11,761 more landslides were identified by much more careful and time-consuming visual interpretation based on the same aerial photographs and satellite images. Subsequently, all the 15,645 coseismic landslides were correlated with six common landslide impact factors, including elevation, slope angle, slope aspect, topographic position, stratum/lithology, and peak ground accumulation (PGA). These observational and compiled coseismic landslide data allow us to make subsequent compiling of a detailed and completed landslide inventory by visual interpretation of remote sensing images as well as further studies of landslides induced by the Lushan earthquake. [ABSTRACT FROM AUTHOR]

The 20 April 2013 Lushan earthquake with a magnitude of M s 7.0 induced widespread landsliding along the southern segment of the Longmen Shan fault zone. This paper presents a preliminary analysis of the characteristics of these co-seismic landslides triggered in an area of 13,323 km 2 . A total of 3810 individual landslide points were identified through an intensive field investigation and from digital aerial photographs taken after the Lushan earthquake. To facilitate the more detailed analysis on the areal frequency of co-seismic landslides as polygons, we selected an area of 732 km 2 around the epicenter that had the highest density of co-seismic landslides. The sizes of the landslides are, in general, much smaller than those that were triggered by the 2008 Wenchuan earthquake. The most common types of landslides in the study area were rock falls and shallow, disrupted landslides from steep slopes, which typically involved the top few meters of weathered bedrock and colluvium. In this study, the relation between the landslide distribution and five main factors was analyzed: fault proximity, epicenter proximity, peak ground acceleration (PGA), slope angle, and lithology. Our study results show that the landslide concentration tends to decrease with distance from the seismogenic fault, and the highest landslide concentration is located within a distance of 5 km. Regarding the distance to the epicenter, the largest landslide density is found at a distance between 5 and 10 km. The landslide concentration also increases with increasing slope angle until a maximum for the slope class 45°–55°. In addition, results show that slopes consisting of deeply weathered and fractured sandstones and mudstones were the most susceptible to co-seismic landslides. In this study, we found that the location of the hanging wall and the footwall of the fault did not seem to have an important effect on the landslide distribution. This is in contradiction to what has been reported in other earthquake areas such as the Wenchuan area. [ABSTRACT FROM AUTHOR]

We present the current status of seismic noise interferometry to reconstruct the seismic velocity and discuss the four phases from single-station data preparation to quality control of data processing procedures. Each phase of the processing procedure has been discussed in detail with salient examples using seismic data acquired in Changbaishan volcano region. In the end, we use continuous recordings in Jilin, China to track the temporal change of the seismic velocity variations with the method promoted in this paper. We filter the data between the frequency band 0.02 and 0.1 Hz, which the Rayleigh waves are most sensitive to the shear wave velocities in the crust and uppermost mantle. The long-term seismic variations present strong seasonal influence which may be caused by precipitation. We find clear evidence that the seismic velocity drops by up to ∼0.8% which may be caused by the dilatation of the volcanic edifice before the Mar. 11 2011 Japan earthquake. [ABSTRACT FROM AUTHOR]

The alternating electromagnetic (EM) field is one of the most sensitive physical fields related to earthquakes. There have been a number of publications reporting EM anomalies associated with earthquakes. With increasing applications and research of artificial-source extremely low frequency EM and satellite EM technologies in earthquake studies, the amount of observed data from the alternating EM method increases rapidly and exponentially, so it is imperative to develop suitable and effective methods for processing and analyzing the influx of big data. This paper presents research on the self-adaptive filter and wavelet techniques and their applications to analyzing EM data obtained from ground measurements and satellite observations, respectively. Analysis results show that the self-adaptive filter method can identify both natural- and artificial-source EM signals, and enhance the ratio between signal and noise of EM field spectra, apparent resistivity, and others. The wavelet analysis is capable of detecting possible correlation between EM anomalies and seismic events. These techniques are effective in processing and analyzing massive data obtained from EM observations. [ABSTRACT FROM AUTHOR]

On July 22, 2013, an earthquake of Ms. 6.6 occurred at the junction area of Minxian and Zhangxian counties, Gansu Province, China. This earthquake triggered many landslides of various types, dominated by small-scale soil falls, slides, and topples on loess scarps. There were also a few deep-seated landslides, large-scale soil avalanches, and fissure-developing slopes. In this paper, an inventory of landslides triggered by this event is prepared based on field investigations and visual interpretation of high-resolution satellite images. The spatial distribution of the landslides is then analyzed. The inventory indicates that at least 2330 landslides were triggered by the earthquake. A correlation statistics of the landslides with topographic, geologic, and earthquake factors is performed based on the GIS platform. The results show that the largest number of landslides and the highest landslide density are at 2400m-2600m of absolute elevation, and 200m-300m of relative elevation, respectively. The landslide density does not always increase with slope gradient as previously suggested. The slopes most prone to landslides are in S, SW, W, and NW directions. Concave slopes register higher landslide density and larger number of landslides than convex slopes. The largest number of landslides occurs on topographic position with middle slopes, whereas the highest landslide density corresponds to valleys and lower slopes. The underlying bedrocks consisting of conglomerate and sandstone of Lower Paleogene (Eb) register both the largest number and area of landslides and the highest landslide number and area density values. Correlations of landslide number and landslide density with perpendicular- and along-strike distance from the epicenter show an obvious spatial intensifying character of the co-seismic landslides. The spatial pattern of the co-seismic landslides is strongly controlled by a branch of the Lintan-Dangchang fault, which indicates the effect of seismogenic fault on co-seismic landslides. In addition, the area affected by landslides related to the earthquake is compared to the relationship of "area affected by landslides vs. earthquake magnitude" constructed based on earthquakes worldwide, and it is shown that the area affected by landslides triggered by the Minxian-Zhangxian earthquake is larger than that of almost all other events with similar magnitudes. [ABSTRACT FROM AUTHOR]

In this paper, variations of shear wave splitting in the 2013 Lushan Ms7.0 earthquake sequence were studied. By analyzing shear wave particle motion of local events in the shear wave window, the fast polarization directions and the delay time between fast and slow shear waves were derived from seismic recordings at eight stations on the southern segment of the Longmenshan fault zone. In the study region, the fast polarization directions show partition characteristics from south to north. And the systematic changes of the time delays between two split shear waves were also observed. As for spatial distribution, the NE fast polarization directions are consistent with the Longmenshan fault strike in the south of focal region, whereas the NW fast direction is parallel to the direction of regional principal compressive stress in the north of focal region. Stations BAX and TQU are respectively located on the Central and Front-range faults, and because of the direct influence of these faults, the fast directions at both stations show particularity. In time domain, after the main shock, the delay times at stations increased rapidly, and decreased after a period of time. Shear-wave splitting was caused mostly by stress-aligned microcracks in rock below the stations. The results demonstrate changes of local stress field during the main shock and the aftershocks. The stress on the Lushan Ms7.0 earthquake region increased after the main shock, with the stress release caused by the aftershocks and the stress reduced in the late stage. [ABSTRACT FROM AUTHOR]

Earthquake relic is a unique geoheritage. At present, the research on earthquake relic geoparks or national parks is less domestic and overseas, while the protection, development and exploration are in its infancy. This paper, taking ‘Qingchuan Earthquake Relic Geopark’ (QERG) as an example, analyses the characteristics of the geopark, and explores the development model, in order to provide reference for the earthquake relic geopark and national park development domestic and overseas. [ABSTRACT FROM AUTHOR]

The 12 May 2008 Wenchuan earthquake in China triggered numerous landslides. Loose landslide materials can easily evolve into deadly debris flows during wet seasons. During the period from 2008 to 2011, three separate large-scale debris flows occurred in the Pubugou Ravine near the epicentre of the earthquake that were among the largest repeated debris flows ever reported. Approximately 1.76 × 106 m3 of sediment was deposited during these three events. This paper aims to ( i) analyze the movements of solid materials during the repeated debris flows, ( ii) discuss the evolution of the initiation mechanisms of these debris flows, and ( iii) evaluate the changing depositional morphology of the debris flow fans and examine the particle sizes of the debris flow materials. To achieve the above research objectives, timely field investigations were undertaken in the past 5 years after each of these debris flow events. Satellite images were used to delineate the boundaries of the initiation areas, the transportation channels, and the deposition zones of these debris flows. With the occurrence of the repeated debris flows, the hill slope deposits gradually evolved into channel deposits and the solid materials in the channels moved toward the gully mouth. Hence, channelized flows gradually became dominant. The debris fan materials of the repeated debris flows became coarser and coarser over time. The three debris flows were all characterized by coarse boulder fronts. [ABSTRACT FROM AUTHOR]

With the rapid development of nuclear industry in China, an increasing number of nuclear power plants (NPPs) are unavoidable to be constructed upon non-lithological foundations. Therefore, it is essential to optimize the current evaluation methods for non-lithological foundation reinforcement plans. By using the Octree discretization method combining with the scaled boundary polyhedron finite element method (SBFEM), a refined calculation model of a Generation III+ NPP is constructed. Due to the highly nonlinear dynamic characteristics of the system involved, this paper adopts a generalized plasticity model for the soil, a plastic damage model for the piles, and a nonlinear overburden layer-based seismic input method. Subsequently, large scale plastic damage analysis in detail to the NPPs under beyond-design basis earthquake inputs is performed. The results show that the pile foundation damage characteristics and distribution acquired from simulations agree well with the data from actual earthquake disasters. The most severe damage to the pile foundation occurred at the interface between the end of the pile and the base mat. The inclusion of plastic damage showed that the floor response spectra of the nuclear island experiences significant changes in three dimensions. Therefore, the effect of pile damage to the dynamic response of the power plants should be considered for strong earthquake excitation. The computational and analysis methods proposed in this paper can effectively reflect the dynamic nonlinear response of the nuclear power plants pile foundation-soil interaction. • The AP1000 three-dimensional refined model with internal structure and pile foundation is constructed. • The Nuclear Island-pile-soil interaction response law under beyond-design basis earthquake motion is studied. • Plastic damage evolution of pile foundation of nuclear power plants is simulated. [ABSTRACT FROM AUTHOR]

Abstract: The main objective of early impact analysis after a disaster is to produce georeferenced data about the affected areas, in support of humanitarian action. Crucial information is the identification of the disaster areas and the estimation of the number of people involved. Satellite imageries are mainly used as input data for early impact analysis in medium and large scale map. Analyses aimed at defining the damages of infrastructure and/or to facilities require suitable data, such as high resolution satellite images. Unfortunately, satellite images are not always available in a few days after the event. Therefore in situ surveys are preferred. Innovations in Unmanned Aircraft System (UAS) have allowed them to become valuable tools in capturing and assessing the extents and amount of damages. Flexibility, safety, ease of operation, and relatively low-cost of ownership and operation facilitate UAS implementation in disaster situations. In this paper, an example of UAS was developed for rapidly obtaining disaster information. Data acquisition at specified scales was successfully performed with the chosen fixed-wing UAS. For the image analysis, a photogrammetric workflow was applied to cope with the very high resolution of the images acquired without ground control points. Tests showed that the system plays an important role in the work of investigating and gathering information about disaster in epicentral areas of the earthquake, such as road detection, secondary disaster investigation, and rapid disaster evaluation. It can effectively provide earthquake information to salvation headquarters for swiftly developing the relief measures and improving the efficiency of emergency rescue. [Copyright &y& Elsevier]

Abstract: Numerous landslides were triggered by the 12 May 2008 Wenchuan earthquake in China, particularly near the epicenter. During the rainy season in 2010 after the earthquake, much of the landslide debris was reactivated, causing a large number of fatalities. The earthquake has a significant impact on the subsequent rain-induced landslides. Based on interpretation of satellite images taken in 2008 and 2010, combined with yearly field investigations, this paper attempts to (1) map the earthquake-induced landslides near the epicenter; (2) present the distribution of the landslides occurring during a subsequent extreme storm in the same area; and (3) compare the distribution characteristics of the earthquake-induced landslides and the rain-induced landslides. Through this study, the following findings were obtained: (1) the internal relief of the landslides in the study area is much higher than that in other affected regions of the Wenchuan earthquake zone; (2) the landslide area in hard rocks (i.e. the granite and diorite zones) is much larger than that in alluvium; (3) the volume of hill-slope loose deposits decreased while the volume of channel deposits increased during the process of mass transportation caused by rainfall after the earthquake; (4) during the rainy seasons after the earthquake, the density of landslides increased while the area of landslides decreased significantly and the type of landslides transformed from debris slides to debris flows; and (5) the rain-induced landslides are less steeper than the earthquake-induced landslides. [Copyright &y& Elsevier]

Abstract: During the 1920 Haiyuan earthquake, numerous catastrophic landslides were triggered in the loess area in Northwest China. We investigated in detail a large example of these landslides, referred to as Dangjiacha landslide in this paper. This landslide originated from a slope of about 20°, and the displaced soil mass traveled about 3200m, damming a valley. We performed a field survey and found that standing water existed in the landslide area and the loess had high porosity. We infer that it was the liquefaction of the water-saturated loess layer rather than the suspension of silt in the pore-air in the loess that caused the great mobility of this landslide. To test this inference, we performed undrained triaxial compression and ring shear tests on loess samples to examine the shear behavior of loess saturated by either air or water. The test results showed that the water-saturated loess soil was highly susceptible to flow liquefaction failure. Fast shear tests on naturally air-dried loess samples revealed that the generated pore-air pressure was small under the “undrained condition” and no significant reduction in the shear resistance was observed, implying that air entrapped in the loess was unlikely to be the main contributor to the high mobility of this large-scale landslide. [Copyright &y& Elsevier]

Underground displacement monitoring is an effective method to explore deep into rock and soil masses for execution of subsurface displacement measurements. It is not only an important means of geological hazards prediction and forecasting, but also a forefront, hot and sophisticated subject in current geological disaster monitoring. In previous research, the authors had designed a novel electromagnetic underground horizontal displacement sensor (called the H-type sensor) by combining basic electromagnetic induction principles with modern sensing techniques and established a mutual voltage measurement theoretical model called the Equation-based Equivalent Loop Approach (EELA). Based on that work, this paper presents an underground displacement inversion approach named "EELA forward modeling-approximate inversion method". Combining the EELA forward simulation approach with the approximate optimization inversion theory, it can deduce the underground horizontal displacement through parameter inversion of the H-type sensor. Comprehensive and comparative studies have been conducted between the experimentally measured and theoretically inversed values of horizontal displacement under counterpart conditions. The results show when the measured horizontal displacements are in the 0-100 mm range, the horizontal displacement inversion discrepancy is generally tested to be less than 3 mm under varied tilt angles and initial axial distances conditions, which indicates that our proposed parameter inversion method can predict underground horizontal displacement measurements effectively and robustly for the H-type sensor and the technique is applicable for practical geo-engineering applications. [ABSTRACT FROM AUTHOR]

Recent large earthquakes in China (e.g., Wenchuan earthquake and Yushu earthquake) resulted in enormous damage to school buildings and took many students' lives. Recognizing the seismic vulnerability of existing school buildings, the Chinese government started a nationwide mission in 2009, aiming at increasing the seismic capacity of school buildings through inspection and retrofit activities. This paper presents the experiences of the authors in the retrofits of school buildings in which seismic isolation by using rubber and/or sliding bearings was adopted as a new and efficient retrofit technique, as compared with conventional ones. The retrofitted school buildings include masonry buildings, RC frame buildings, and a mixture of both. Design methods and the corresponding requirements in the modified seismic design code are presented, and typical construction procedures of the seismic retrofit are summarized from an engineer's point of view. Procedures regarding the contract and review of the retrofit projects are also introduced. To this end, a case study is made to demonstrate the proposed design and construction methods. The presented work provides references to the seismic retrofit of existing buildings. [ABSTRACT FROM AUTHOR]

Abstract: One of various mechanisms of pre-earthquake lithosphere–atmosphere–ionosphere coupling as possible explanation of the seismo-ionospheric effects is connected with the release of latent heat. Abnormal variations of ionospheric electromagnetic parameters possibly related to the 2007 Ms 6.4 Pu’er earthquake in China were reported. This paper attempts to examine whether there were abnormal changes of surface latent heat flux (SLHF) linked with this pre-earthquake ionospheric disturbances. The spatio-temporal statistical analyzes of multi-years SLHF data from USA NCEP/NCAR Reanalysis Project reveal that local SLHF enhancements appeared 11, 10 and 7days before the Pu’er earthquake, respectively. As contrasted to the formerly reported local ionospheric Ne enhancement 9days before the shock observed by DEMETER satellite, it is discovered that the SLHF and Ne anomalies are quasi-synchronous and have good spatial correspondence with the epicentre and the local active faults. This is valuable for understanding the seismogenic coupling processes and for recognizing earthquake anomaly with multiple parameters from integrated Earth observation system. [Copyright &y& Elsevier]

Abstract: The Longmen-Shan fault zone, at the eastern margin of the Tibetan Plateau, is one of the most extensively studied areas in the world, yet the deformation model and earthquake-generating mechanism remain subjects of vigorous debate. This paper presents a new three-dimensional (3-D) velocity model determined using a large volume of seismic data and two-dimensional (2-D) magnetotelluric (MT) profiles from previous studies, to investigate the mechanisms of crustal deformation and earthquake generation along the reverse-thrust and strike-slip fault zone. It has been observed that low-velocity, and low-resistivity anomalies related to the Sichuan foreland basin, is in sharp contrast to high-velocity and high-resistivity anomalies in the Songpan-Ganze block in the upper crust. The tomographic model presented here reveals two crustal bodies with low-velocity and high-conductivity anomalies underneath the Longmen-Shan fault zone, separated into three contrasting segments by the two crustal bodies. The two low-velocity and low-resistivity bodies have been interpreted as being associated with extrusion of either fluids or products of partial melting from the lower crust and/or the upper mantle. This suggests strong variations in the rheological strength of the rock along the fault zone. This finding implies that coupling between these presumably fluid-bearing bodies and earthquake generation could be extremely complex and that there is dramatic variation from the southwestern area to the northeastern segment along the fault belt. It is suggested here that this complex and variable deformation system along the fault zone played a principal role in controlling seismic generation and rupturing during the 2008 Wenchuan earthquake (Ms 8.0) and that it will do so again during possible future earthquakes in the region. [Copyright &y& Elsevier]

Earthquake emergency response is one of the three earthquake disaster mitigation work systems in China, already achieving good results in some earthquake disaster mitigation situations. Earthquake emergency plans and emergency command systems are among the most important research and operations components of emergency response. These components commonly come with challenges, such as the pertinence of emergency commands and the operability of the countermeasures to be improved. The promise for solving this problem resides with applying knowledge that aids intelligence creation for decision-making. In this paper, we put forward a conceptual model of knowledge for earthquake disaster emergency response (EDER); compositions of EDER knowledge are introduced within architecture. A modeling method incorporating geo-ontology is used to build basic modeling primitives. Geo-ontology serves to represent geospatial characteristics of the EDER knowledge and addresses a need for semantic interoperability in the modeling process. A decision problem framework and a case study have been used as theoretical framework and an application test, respectively, to evaluate the EDER knowledge architecture and models. The EDER knowledge model provides a foundation for intelligent emergency response that helps solve knowledge problems to improve earthquake disaster response. [ABSTRACT FROM PUBLISHER]

According to the 'jacking-up' theory, which relates the cause of earthquakes to outer core convection ascension bodies, the crust will gradually recover after an earthquake. In such cases, the crust is stretched, the underground temperature is reduced, precipitation decreases, and drought occurs. In this paper, precipitation is compared with ground temperature and seismic data to determine the spatial and temporal relationship between earthquakes and subsequent droughts. Our objective is to develop a new method of drought prediction. With a few exceptions in location, the analysis of the first drought to occur after the Ms ≥ 7 earthquakes in mainland China and the adjacent areas since 1950 shows that droughts tended to occur in regions near earthquake epicenters and in the eastern regions of the epicenters at the same latitude within six months after the earthquakes. In addition, and the differences between the starting time of the earthquakes and the droughts nearly share the same probability of 0 to 6 months. After careful analysis of 34 Ms ≥ 6.5 earthquakes occurring in western China from 1980 to 2011, we determined that a second drought tends to occur approximately six months following the first drought, indicating a quasi-half-year period. Moreover, the duration of the quasi-half-year fluctuation increases with the magnitude of earthquake, at approximately 2.5 years for Ms 6.5 earthquake and approximately 5 years for Ms 8 earthquake [ABSTRACT FROM AUTHOR]

Box concrete-encased, concrete-filled steel tube (CFST) piers have been used in bridges in high-earthquake-intensity regions in China in recent years. They are expected to have higher strength and better ductility than normal box reinforced concrete members owing to the contribution of CFSTs in the corners of the composite box section. However, studies on this type of composite piers are limited. This paper presents an experimental study on the behaviour of box concrete-encased CFST columns under eccentric compression. A total of 14 specimens, including 12 box concrete-encased CFST specimens and two reference box reinforced concrete specimens are tested. The main parameters in the test are height-to-width ratio and load eccentricity. A simplified method is proposed to predict the load capacity of the box concrete-encased CFST columns. [ABSTRACT FROM AUTHOR]

Severe damage to steel space structures is rarely reported when compared to other structural systems damaged during past major earthquakes around the world. Two gymnasiums of steel space structures in downtown Lushan County that were damaged during the 2013 M7.0 Lushan earthquake in China were investigated and the observations are summarized in this paper. Typical damage to these two steel space structures ranges from moderate to severe. Moderate damage includes global buckling and dislocation of bolted connections of truss members, and inelastic elongation of anchor bolts and sliding of pedestal plates of supports. Severe damage includes member fracture caused by local buckling, and fracture failure of anchor bolts and welds. The distribution of structural damage to these two structures is described in detail and future research opportunities are suggested. [ABSTRACT FROM AUTHOR]

Seismic landslides are the most common and highly destructive earthquake-triggered geological hazards. They are large in scale and occur simultaneously in many places. Therefore, obtaining landslide information quickly after an earthquake is the key to disaster mitigation and relief. The survey results show that most of the landslide-information extraction methods involve too much manual participation, resulting in a low degree of automation and the inability to provide effective information for earthquake rescue in time. In order to solve the abovementioned problems and improve the efficiency of landslide identification, this paper proposes an automatic landslide identification method named improved U-Net model. The intelligent extraction of post-earthquake landslide information is realized through the automatic extraction of hierarchical features. The main innovations of this paper include the following: (1) On the basis of the three RGB bands, three new bands, DSM, slope, and aspect, with spatial information are added, and the number of feature parameters of the training samples is increased. (2) The U-Net model structure is rebuilt by adding residual learning units during the up-sampling and down-sampling processes, to solve the problem that the traditional U-Net model cannot fully extract the characteristics of the six-channel landslide for its shallow structure. At the end of the paper, the new method is used in Jiuzhaigou County, Sichuan Province, China. The results show that the accuracy of the new method is 91.3%, which is 13.8% higher than the traditional U-Net model. It is proved that the new method is effective and feasible for the automatic extraction of post-earthquake landslides. [ABSTRACT FROM AUTHOR]

Understanding the spatial distribution regularity of coseismic landslides is important for mitigation in future earthquakes. Unveiling the controlling factors of the distribution of coseismic landslides is a long-standing unsolved problem. On 3 August 2014, a Mw 6.1 earthquake occurred in Ludian County, Yunnan Province, China, and resulted in a great number of landslides and substantial losses. The coseismic landslide distribution in this earthquake, which was triggered by an unmapped fault, shows a different pattern. This paper conducted a spatial analysis to reveal the controlling factors in the Ludian earthquake. A spatial database of landslides has been built by interpreting the ZY-3 pre-earthquake, unmanned aerial vehicle (UAV), GeoEye-1 and GF-1 post-earthquake. A total of 1414 landslides were identified after a combination of image interpretation and field investigation in an area of 704.7 km2. The geological setting of the study area, including the tectonics and lithology, has been mapped in detail. The digital elevation model (DEM) of the study area with a resolution of 30 m × 30 m was presented to address the topographic characteristics. A geographic information system (GIS) was used to analyse the spatial characterization of the landslides. Correlations between the occurrences of landslides and factors, i.e., slope gradient, elevation, slope aspect, intensity, distance to coseismic fault, distance to the epicentre, lithology, distance to non-coseismic faults, distance to rivers and distance to road, were characterized with a spatial analysis in GIS. It can be concluded that the slope gradient and the distance to the coseismic fault are the two most important factors for determining the spatial distribution of coseismic disasters. Some other factors play a role by influencing the slope gradient to a certain extent, and the movement of the coseismic fault is the prone direction of coseismic landslides. Slope cutting fractures the rock mass, increases the slope gradient, and significantly increases the occurrence of coseismic landslides. A statistics analysis indicates that the landslide concentration (LC) generally has an obvious exponential decrease with an increasing distance to the coseismic fault, while it has a good Weibull cumulative distribution with the slope gradient. • A complete coseismic landslide inventory were documented in 2004 Mw 6.1 Ludian struck area of 704.7 km2. • Correlations between landslide occurrences and nine factors including geographical and geological setting were investigated. • The relationships among factors influencing the spatial distribution of coseismic landslides are disclosed. • Slope gradient and the distance to the coseismic fault or epicentre are the two determinants for LC of coseismic landslides. [ABSTRACT FROM AUTHOR]

Abstract: Earthquake Early Warning System (EEWS) is one of the effective ways to mitigate earthquake damage and can provide few seconds to tens of seconds of advanced warning time of impending ground motions, allowing for mitigation measures to be taken in the short term. In the present paper, we develop an integrated onsite EEWS called EDAS-MAS, which is based on the physical characteristics of the P-wave velocity greater than S-wave velocity. The instrument is a single device which includes a 3-channel MEMS accelerometer, a data acquisition unit, seismological processing, and three types of alarms. Two types of magnitudes are computed by using -Pd values and the estimated hypocentral distance. It can directly raise the warning to the public when the magnitudes exceed the predefined thresholds, providing longer effective warning time and reducing the “blind zone” range. Although a majority of the reported events were small earthquakes and a relative high false alarms rate existed in the test, the results have shown the capabilities of the prototype EDAS-MAS for EEWS and are of practical importance for the design and optimization of the system. [Copyright &y& Elsevier]

Abstract: The reports from the International Atomic Energy Agency (IAEA) and the Japanese Nuclear and Industrial Safety Agency (NISA) have confirmed that the Fukushima Daiichi nuclear power plant (NPP) survived the initial earthquake impacts, but fell victim to the following tsunami. The 14-m tsunami well exceeded the maximum safety design of 5.7m. It damaged the pumps, cut off the external power supplies to cool the reactors and spent fuel pool, and directly contributed to the three core meltdowns at the Fukushima Daiichi NPP. These official reports, academic papers, and breaking news also show that five warnings of tsunamis at the Fukushima Daiichi NPP had been ignored by the nuclear operator and regulators since 2000. This article argues that not the natural disaster, but the regulatory failures contributed to the worst nuclear accident since Chernobyl. It explains how the cozy relationship between the government, regulators and nuclear operators, the combined role of NISA as an industry promoter and regulator, and the revolving door between bureaucrats and industries had long undermined the capacity of NISA as a watchdog for nuclear safety. It concludes that upgrading and strengthening a nuclear regulatory system is not optional but imperative to prevent the next core meltdown. Three key recommendations are offered for upgrading nuclear safety regulation. [Copyright &y& Elsevier]

Abstract: The 2008 Ms 8.0 Wenchuan earthquake of China ruptured two large faults along the Beichuan-Yingxiu thrust belt and the Pengguan thrust belt at the Longmen Shan Orogenic belt, eastern margin of the Tibetan Plateau. Our study focused on the structural geometry at the Pengguan thrust belt located at the frontal zone of the Central Longmen Shan. In this paper, in order to identify the co-seismic fault at the Pengguan thrust belt many 2-D/3-D seismic reflection profiles have been interpreted by integrating with the geological maps, drilling data, DEM data and the surface ruptures. The results show that there were three major faults and other branch faults at the Pengguan thrust belt. The major faults have formed as imbricates and associated minor duplexes within the shallow strata. The Pengguan fault has a steep dip at the shallow surface and a gentle dip at depth. Both the Beichuan-Yingxiu fault and the Pengguan fault were developed on the shallow detachment in the central segment of Longmen Shan. The third (No. ③) Pengguan fault is coincident with the co-seismic surface ruptures. It was a pre-existing fault and re-activated during the Wenchuan earthquake. Three-dimensional geometries show that the No. ③ fault is heterogeneous and it has controlled the slip of co-seismic ruptures. Based on the regional geology, the 3-D fault geometry and the surface ruptures, the frontal zone of the Central Longmen Shan has been divided into the Bailu segment and the Hanwang segment. Our studies suggest that the Pengguan fault has been active since the Cenozoic. The frontal zone of the Central Longmen Shan thrust belt has potential for future earthquakes. [Copyright &y& Elsevier]

The power spectrum density (PSD) of magnetic field in the ELF/VLF band recorded by the experiment IMSC onboard the DEMETER satellite were used to study the Ms7.1 Yushu earthquake taking place on April 13, 2010 in China. The results indicate that possible ionospheric electromagnetic perturbations occurring 4 days before the earthquake in the frequency range [370-897 Hz]. Along the orbit 30880_up, which passed over the epicenter area on 9 April, enhanced PSD value of magnetic field at 410 Hz was detected both over the epicentral area and its conjugate point in the southern hemisphere. While on revisited orbits during other days (before and after the earthquake) the magnetic field spectra remained at a relatively low level. In order to be sure that the electromagnetic disturbances were induced by this Yushu earthquake, relative variations of the magnetic field in the ELF/VLF range [370-897 Hz] were calculated and compared with the normal background during 3 years (2007, 2008 and 2009) in the time interval from Jan. 1st to Apr. 30 and in the area [23°N-43°N, 86°E-106°E]. The results show that the normal level of magnetic field in this area is relatively low (~10 nT/Hz), but a large increase occurred from Apr. 1st to Apr. 14 which exceeds 5σ. After the earthquake, the magnetic field in the ELF/VLF range gradually decreased. In order to exclude the influence of geomagnetic field activity, we selected only the data recorded during magnetically quiet local night-times. In addition, artificial noises were also removed from the dataset used in the present paper. Therefore the observed perturbations were independent of geomagnetic field disturbances, and might be attributed to seismic activity. [ABSTRACT FROM AUTHOR]

Abstract: The large oblique reverse slip shock of the 2008 Mw=7.9 Wenchuan earthquake, China, produced one of the longest and most complicated surface ruptures ever known. The complexity is particularly evident in the Xiaoyudong area, where three special phenomena occurred: the 7km long Xiaoyudong rupture perpendicular to the Beichuan-Yingxiu fault; the occurrence of two parallel faults rupturing simultaneously, and apparent discontinuity of the Beichuan-Yingxiu rupture. This paper systematically documents these co-seismic rupture phenomena for the Xiaoyudong area. The discussion and results are based on field investigations and analyses of faulting mechanisms and prevalent stress conditions. The results show that the Beichuan-Yingxiu fault formed a 3.5km wide restraining stepover at the Xiaoyudong area. The Xiaoyudong fault is not a tear fault suggested by previous researches, but a frontal reverse fault induced by the oblique compression at this stepover; it well accommodates the ‘deformation gap’ of the Beichuan-Yingxiu fault in the Xiaoyudong area. Further, stress along the Peng-Guan fault plane doubles due to a change in dip angle of the Beichuan-Yingxiu fault across the Xiaoyudong restraining stepover. This resulted in two faults rupturing the ground’s surface simultaneously, to the north of the Xiaoyudong area. These results are helpful in deepening our understanding of the dynamic processes that produced surface ruptures during the Wenchuan earthquake. Furthermore, the results suggest more attention be focused on the influence of dextral slip component, the change of the control fault’s attitude, and property differences in rocks on either side of faults when discussing the formation mechanism of surface ruptures. [Copyright &y& Elsevier]

Abstract: In the Wenchuan area in SW China, an abundance of loose co-seismic landslide debris was present on the slopes after the Wenchuan earthquake, which in later years served as source material for rainfall-induced debris flows or shallow landslides. Slopes composed of Cambrian sandstones and siltstones intercalated with slates appeared to be most susceptible to co-seismic landsliding. A total of 20 debris flows are described in this paper; all were triggered by heavy rainfall on 13th of August 2010. Field reconnaissance and measurements, supported by aerial photo interpretation, were conducted to identify the locations and morphological characteristics of the debris flow gullies in order to obtain information about surface area and volume of landslides and the debris flows. The debris flows in the study area were initiated by two processes: a) run-off erosion on co-seismic landslide material, and concentrated erosion of landslide debris in steep channels; b) new landslides that transform into debris flows. The volume of debris flow deposits on individual fans varies by many orders of magnitude. The smallest deposit has a volume of from 5760 to 3.1millionm3. A comparison of the measured volumes, deposited on the fan with the volumes of debris stored in the catchment shows the huge potential for future debris flow activity. Whilst there is a weakly significant positive correlation between these two volumes, no significant statistical correlation could be established between volumes of debris flow deposits and other morphometric parameters of the catchment. A catastrophic debris flow catchment (the Wenjia catchment) was selected as an extreme case to show in detail the mechanism of debris flow formation as a result of intensive erosion in loose material, which was deposited by a rock avalanche during the 2008 Earthquake event. Analyses of the meteorological conditions that triggered these debris flows show one day antecedent precipitation varying between 67.7 and 137.6mm, with a mean rainfall intensity of about 7.3 to 22.5mm/h. A rainfall event with peak intensity of 38.7mm/h triggered the largest debris flow event. Rainfall data related to five debris flow events in the Wenjia torrent was used to establish a primary rainfall intensity–duration relationship for the triggering of debris flows, which was compared to other rainfall duration thresholds from other parts of the world. In the discussion emphasis is laid on the need to unravel the process mechanisms which initiated the debris flows for a better understanding and assessment of meteorological thresholds. [Copyright &y& Elsevier]

Composite borehole profiling combined with trenching is an effective way to acquire evidence of past ruptures of buried active faults. In this study, three composite borehole profiles and a large-scale trench excavation were carried out across the surface rupture zone of the 1976 M7.8 Tangshan earthquake. The following three major conclusions have been reached. (1) The surface rupture zone of the 1976 earthquake extends more than 47 km long to the south of Tangshan city, passing to the west of Sunjialou, to Daodi town in Fengnan County, to Xihe in Fengnan County. (2) The surface rupture zone is divided into south and north branches. The north branch has mainly right-lateral strike-slip motion, and the vertical displacement of the surface is up on the west and down on the east. On the other hand, the vertical displacement of the south branch is up on the east and down on the west, accompanied by some right-lateral slip. Such a faulting style cannot be explained by the movement of a single normal or reverse fault, but is consistent with the vertical displacement field induced by the right-lateral strike-slip of the fault belt. The drilling and trenching data from this study verify that such activity continued through the Late Quaternary on the Tangshan Fault. (3) The fault planes exhumed by trenching and the dislocations of strata revealed by the boreholes indicate that multiple faulting events occurred on the Tangshan Fault in the Late Quaternary. The timing of three ruptures prior to the 1976 earthquake was 7.61-8.13, >14.57, and 24.21-26.57 ka BP. Counting the earthquake of 1976, the recurrence interval of the four strong events is about 6.7 to 10.8 ka. On one of the three borehole profiles, the Niumaku profile, nine faulting events were detected since 75.18 ka BP with an average interval of 8.4 ka. In addition, this paper also discusses the difference between the Late Quaternary sedimentary environments to the north and south of Tangshan city based on stratum dating. [ABSTRACT FROM AUTHOR]

The N-S trending Xiaojiang fault zone and the NW-SE trending Qujiang-Shiping fault zone are adjacent active fault systems and seismogenic zones associated with strong and major earthquakes in Yunnan, China. To understand the interaction of the two fault systems, and its probable influence on earthquake occurrences, this paper conducts a synthetic study based on data of active tectonics, historical earthquakes, relocated small earthquakes, GPS station velocities and focal mechanism resolutions. The study makes several conclusions. (1) The active southward motion of the western side of the Xiaojiang fault zone (i.e. the side of the Sichuan-Yunnan block) has a persistent and intensive effect on the Qujiang-Shiping fault zone. The later fault zone has absorbed and transformed the southward motion of the western side of the former fault zone through dextral strike-slip/shearing as well as transverse shortening/thrusting. (2) Along the Xiaojiang fault zone, the present sinistral strike-slip/shearing rate decreases from 10 and 8 mm/a on the northern, central and central-southern segments to 4 mm/a on the southern segment. The decreased rate has been adjusted in the area along and surrounding the Qujiang-Shiping fault zone through reverse-dextral faulting and distributed shearing and shortening. (3) The tectonic-dynamic relation between the Xiaojiang fault zone and the Qujiang-Shiping fault zone is also manifested by a close correlation of earthquake occurrences on the two fault zones. From 1500 to 1850 a sequence of strong and major earthquakes occurred along the Xiaojiang fault zone and its northern neighbor, the Zemuhe fault zone, which was characterized by gradually accelerating strain release, gradually shortening intervals between M⩾7 events, and major releases occurring in the mid to later stages of the sequence. As a response to this sequence, after an 88-year delay, another sequence of 383 years (from 1588 to 1970) of strong and major earthquakes occurred on the Qujiang-Shiping fault zone, and had the same features in accelerating strain release and its temporal course. (4) Since there has been no M⩾7 event for 177 years on the Xiaojiang fault zone, the potential risk of a strong or major earthquake occurring on this fault zone in the future should be noticed and studied further. [ABSTRACT FROM AUTHOR]

Abstract: This paper reports that three earthquake sequence occurred in 1996 (m b 5.9), 1998 (m b 5.8) and 2004–2005 (m b 6.2, 6.3) were observed preceding the anomalous seismic activity. The nature of anomalous seismicity associated with these earthquakes have been investigated considering earthquakes with m b ⩾4.1 (cut off magnitude for this region) in four seismic episodes (NAGM): normal/background (N); anomalous/swarm (A); precursory gap (G) and mainshock sequence (M), respectively. It is established here that the anomalous seismicity/swarm patterns follow episodes of relatively very low seismic activity and it is an important finding to visualize that an area might be preparing for the occurrence of a forthcoming mainshock. Such anomalous seismic patterns were observed prior to medium size mainshocks that occurred from 1963 to 2006 in South Central Tibet (SCT) region to the north of Central Himalaya. From these observations it may be inferred here that the patterns of anomalous seismicity/earthquake swarms may be considered as an important parameter (precursor) for the forecasting of long-range earthquake hazards in the SCT region. In consideration of spatial and the temporal clustering of swarm events that are prominent and confined in a vertical column of 10–45km, enabled to locate potential area enclosed by 29.6–30.1°N and 87.8–88.1°E where future earthquake of magnitude 6.0 and above in the depth range 25±15km may be seated. In view of this multi-parameter short term precursory signals monitoring is suggested for the delineated preparatory area to make earthquake prediction/forecasting programs more meaningful. [Copyright &y& Elsevier]

Abstract: In this paper, 240 abnormal infrasound signals observed at Beijing (39.87°N, 116.48°E) and 92 M ≧7.0 worldwide earthquakes during 2002–2008 are investigated. It is found that about 85% the earthquakes are preceded the signals by 1–30days and the greater M ≧7.6 earthquakes are most likely leaded by 1–10days. The maximum amplitude of the abnormal infrasound signal generally exceeds 8Pa in sound pressure. The statistical analyses further indicate that the amplitude of the abnormal signals is proportional to the magnitude the associated forthcoming earthquake but inversely to the distance from that earthquake to the observation station. [Copyright &y& Elsevier]

Tectonic activity offshore China during the Late Miocene and Quaternary ('neotectonism') generated unconformities, resulted in depocentre migration, created new faults and initiated earthquake activity. This episode of structural disturbance, which occurred during post-rift thermal subsidence, modified pre-existing hydrocarbon accumulations and formed new pools. Constructive effects of neotectonism occurred in the Bozhong Depression, Zhu #2 Depression and the Yinggehai Basin. These effects included the formation of new structural traps, migration routes and source kitchens. Destructive effects occurred in the Xihu Depression where oil/gas fields were partially breached by post-trap peneplanation and faulting. There are pools with active gas leakage through neotectonic faults and this seems to suggest a dynamic balance between outboard leakage of gas and inboard migration of hydrocarbons. This paper summarizes understanding of the past 15 years of offshore exploration in China which has primarily focused on Neogene reservoirs. Data used for this report include extensive coverage of conventional P-wave and multi-component 2D and 3D seismic data, drilling results and extensive geochemical and geological analyses. [ABSTRACT FROM AUTHOR]

Due to limited financial resources and challenging geographical conditions, the number of seismic observation networks in China is still very small and they are not widely distributed. Therefore, the available earthquake records obtained after an earthquake have been limited. In this paper, auto-generation methods to obtain strong motion isolines under different conditions are proposed. To verify the accuracy of these methods, some examples, including application to the 2008 Wenchuan earthquake, are given. [ABSTRACT FROM AUTHOR]

This paper documents the emergency breaching of an approximately 110-m-high landslide dam that was created at Tangjiashan during the 2008 Wenchuan earthquake of China's Southwest Sichuan Province. As an emergency measure, a 13-m-deep channel was excavated to reduce the volume and head of the released water during the dam breaching and to create a controlled flood that was intended to prevent catastrophic consequence for 1.2 million people downstream. From detailed monitoring and survey works carried out during and after the dam break it was found that (1) the breaching initiated at a pool water level of 742.1 m with an estimated flow velocity of 2.4 m/s, and virtually terminated at a pool water level of 720.3 m with an estimated velocity of 2.5 m/s, which can be regarded as the incipient velocity that initiated erosions for the soils at this particular site; (2) a controlled flood released 167×106-m3 reservoir water with a peak flow rate of 6,500 m3/s, during which a maximum velocity of about 5.0 m/s was measured; (3) in 12 h, the channel bed was eroded 30 m down and the sidewall was enlarged 145 m wide at an elevation of 719 m, which was expanded to 200-350 m at the top of the channel due to subsequent landslips of the temporary slopes; and (4) the measured data indicated an incipient velocity that initiated soil erosions, which is found to be conceptually in general agreement with the existing approaches of this threshold value. [ABSTRACT FROM AUTHOR]

A large earthquake struck Wenchuan County, China on 12 May 2008 and is one of the most severe natural disasters of recent decades that has changed the entire landscape of Wenchuan County. This paper presents a satellite image analysis of the landslide following the Wenchuan earthquake and its consequences, and demonstrates how remote sensing techniques can be used for civilian crisis-management purpose and disaster relief. Real-time high resolution 2-dimensional and 3-dimensional information on structural deformation of land areas, directional changes of rivers, creation of new lakes, and the water levels of rivers and lakes in the earthquake affected area have been provided using the FORMOSAT-2 and Satellite pour l'Observation de la Terre (SPOT)-5 satellite images. Satellite images taken before and after the 12 May 2008 Wenchuan Earthquake have been used for landslide investigation. Possible flooding and rupture of natural dams during the post-earthquake period have been indicated through the analysis of 3-dimensional images of FORMOSAT-2. Some rescue methods have been suggested for immediate recovery of the bereaved persons and to locate the corresponding area accurately using remote sensing techniques. Some precautionary measures have also been suggested to avoid further destruction. Comparisons of panchromatic and multispectral images of FORMOSAT-2 for a particular region have been made to quantify the location accuracy. Our results show that the real-time high-spatial resolution FORMOSAT-2 satellite images could be an efficient and useful resource for decision-makers to prepare rescue and post-event recovery operation plans, especially for some isolated earthquake areas where damage distribution is often very uneven and hard to reach in time. [ABSTRACT FROM AUTHOR]

This paper analyzes the seismicity in Bohai Sea, introducing a shape factor K to characterize the seismic risk distribution in sub-regions of the sea. Based on the seismic design ground motions for 46 platforms located in the Bohai Sea, a statistical analysis was performed for different peak ground acceleration (PGA) ratios at two different probability levels. In accordance with the two-stage design method, a scheme of two seismic design levels is proposed, and two seismic design objectives are established respectively for the strength level earthquake and the ductility level earthquake. By analogy with and comparison to the Chinese seismic design code for buildings, it is proposed that the probability level for the strength level earthquake and ductility level earthquake have a return period of 200 and 1000–2500 years, respectively. The validity of these proposed values is discussed. Finally, the PGAs corresponding to these two probability levels are calculated for different sub-regions of the Bohai Sea. [ABSTRACT FROM AUTHOR]

The dynamic equations of motion of asymmetric offshore platforms under three different environmental conditions: seismic action, wave action and their combination are established in this paper. In establishing these motion equations, three typical eccentricity types including mass eccentricity, rigidity eccentricity and their combination were considered, as are eccentricities that occur uni-directionally and bi-directionally. The effects of the eccentricity type, the dynamic characteristics and the environmental conditions on the torsional coupling response of platforms are investigated and compared. An effort has also been made to analyze the influence of accidental eccentricity on asymmetric platforms with different eccentricity in two horizontally orthogonal directions. The results are given in terms of non-dimensional parameters, accounting for the uncoupled torsional to lateral frequency ratio. Numerical results reveal that the eccentricity type has a great influence on the torsionally coupled response under different environmental conditions. Therefore, it is necessary to consider the combination of earthquake and wave action in the seismic response analysis of some offshore platforms. [ABSTRACT FROM AUTHOR]

Abstract: The beautiful Longmenshan area is one of the main tourist attractions in Sichuan Province, China. The epicenter of a catastrophic earthquake measured at 8.0Ms (China Seismological Bureau), occurred within this area at Wenchuan (31°01′16″N, 103°22′01″E) at 14:28 May 12, 2008 (Beijing time). The earthquake triggered numerous types of landslide transport and hazards, including soil and debris avalanches, rockfalls, slumps, debris flows, creation of barrier lakes and slope flattenings. This paper examines the landslide hazards in the Longmenshan area caused by the earthquake using remotely sensed images, mainly Beijing-1 Microsatellite data before and after the earthquake, compared to digital elevation maps and slope gradient maps, land use and vegetation cover maps. Areas of erosion and loss of vegetation were compared from pre- and post-earthquake data, from which were calculated changes in vegetated areas, bare slopes, and mass movement during the earthquake. These events occurred over altitudes from 1000 to 4000m and on slope angles between 25 and 55°. The results show that the total area of erosion and land movement due to the earthquake increased by 86.3km2 (19.2% of the study area). Compared with pre-earthquake, the areas of very low intensity soil erosion and moderate intensity soil erosion were respectively reduced by 3.6km2, 24.3km2 and 30.9km2. On the other hand, the areas of severe and very severe intensity soil erosion were substantially increased by 45.8km2 and 99.2km2. In the post-earthquake stage, the bare areas (vegetation cover <15%) have increased by 65.8km2. Without vegetation, the denuded earthquake damaged slopes and other high risk sites have become severe erosion problems. Thus, it is essential to continue long-term monitoring of mass wasting in the denuded areas and evaluate potential risk sites for future landslides and debris flows. We anticipate that these results will be helpful in decision making and policy planning for recovery and reconstruction in the earthquake-affected area. [Copyright &y& Elsevier]

Abstract: This paper presents a quantitative analysis of the number and area of the landslides triggered by the Wenchuan Ms 8.0 earthquake from Anxian to Beichuan. In this study the controlling factors of landslides are obtained from geological maps, relief amplitude, slope, and topographic roughness calculated from DEM data in ArcGis 9.2. A total of 4134 landslides are identified from digital aero-image of 1m resolution, covering 19.7km2 that accounts for 6.4% of the study area. The number of landslides with areas less than 5000m2 is up to 85.22%. The smallest landslide is 6m2 and the largest 1515,000m2. The number of landslides which have occurred is 1.6 times more prevalent at hanging walls as opposed to foot walls. Also the relationship between the numbers of landslides and the distances to an earthquake rupture at a hanging wall is linear but exponential at a footwall. These results prove that landslide activity is more severe at hanging walls than at foot walls. The outcrop area of geologic unit is proportional to the number of landslides except the Jurassic, Triassic and Quaternary units (R 2 =0.952) in the study area, and landslide density is 19. Meanwhile the area of a landslide is linearly proportional to outcrop area of geologic unit except Jurassic, Lower Cambrian and Quaternary unit (R 2 =0.8279) in the study area and appear to indicate that the lithology does not play an important role in landslides in the study area. Earthquake-triggered landslides tend to be concentrated in specific zones associated with the event-controlling parameters such as reliefs, slopes and topographic roughness. The landslides occurred particularly in the range of 600–1293m relief amplitudes, and the number in this range amounts to 90% of total slides in the studied region. Moreover, landslides easily occurred in the curvature 1–15 with slope between 5° and 55°. In addition, landslides also usually occurred in the range of 1–1.5 topographic roughness. Therefore these correlations provide a way to assess regional landslide hazards and are of great significance to regional geohazard planning and prediction. [Copyright &y& Elsevier]

Abstract  The paper analyzes the characteristics and stability of the Jishixia landslide on the Yellow River in Qinghai Province, China, based on field investigations and various exploratory data. The current stability of the landslide was calculated and the future potential stability was assessed assuming a peak ground acceleration of 0.11g due to an earthquake, and the moisture created by flood discharge from the hydropower station. The results indicate that at present the overall landslide is stable, but further movement could be triggered by an earthquake event and/or significant wetting. [ABSTRACT FROM AUTHOR]