vertical seismic profile inversion with genetic algorithms summary we describe a new genetic algorithm ga inversion technique and apply it to a vertical seismic profile vsp inversion problem where the goal is to recover slowness and impedance profiles our algorithm consists of one long 300 generations and a series of short 50 generations ga runs after each run the problem is reparametrized using the matrix of partial second derivatives in a neighbourhood of the best model found in that run the new unknown parameters are more nearly independent than the old ones thus successive ga runs find better models faster in accordance with the principle of meaningful building blocks for the vsp problem we use a fitness function that is the weighted sum of the cross correlation between the measured and synthetic total wavefields and the cross correlation between the measured and synthetic upgoing wavefields the measured upgoing wavefield is obtained from the measured total wavefield by f k

using ambient noise to characterise seismic slope response the case of qiaozhuang peri urban hillslopes sichuan china abstract the mw 7 9 wenchuan earthquake of may 12th 2008 shattered and induced failures on hillslopes surrounding the centre of the town of qiaozhuang located 250 km ne of the mainshock epicentre this motivated investigations on the possible occurrence of site amplification phenomena the initial efforts involved a temporary accelerometer monitoring carried out between april and october 2009 on weigan hill and mount dong located sw and ne of the qiaozhuang centre respectively the monitoring results revealed that the local geological setting characterised by silurian phyllites with sub vertical schistosity at weigan and by fractured precambrian limestones at dong exert major influence on the slopes resonance phenomena with a secondary contribution due to the topographic setting to extend the investigation on local slope response a series of ambient noise recordings were conducted at several sites of the two hills as well as at mount shizi located nw of the town centre which is topographically and geologically similar to mount dong the focus was on the sites monitored by accelerometer stations whose seismic records provided the opportunity to validate the outcomes of ambient noise analysis noise data were analysed using two approaches the standard nakamura s method and a new technique based on analysis of instantaneous polarization properties aimed at estimating ellipticity of rayleigh waves data interpretation was hampered by a contingent factor i e environmental conditions characterised by a strong persistent e w polarized noise at low frequencies below 1 hz and by the complex of geologic and geomorphic conditions the latter particularly in the case of weigan hill appear responsible for a considerable amplification of vertical ground motions the repeated recordings and the comparison of the outcomes of the two techniques of noise analysis with the accelerometer data showed that the new technique provides more stable and consistent results furthermore the new technique was able to reveal site resonance properties that nakamura s method fails to recognise because of transient overlapping of different type waves overall the ambient noise analysis provided evidence of i low frequency resonance 1 hz acting at the scale of the entire relief on weigan hill ii directional amplifications at intermediate frequencies 4 hz affecting ridge crests made of fractured limestone on mounts dong and shizi and iii higher frequency resonances 7 20 hz which vary at a very local scale this information is relevant for inferring the susceptibility of local slopes to earthquake induced failures and hence for the collateral seismic hazard assessment in the qiaozhuan peri urban areas

spatial distribution of landslides triggered by the 2008 ms 8 0 wenchuan earthquake china abstract the ms 8 0 wenchuan earthquake of may 12 2008 is one of the most disastrous earthquakes in china the earthquake triggered tens of thousands of landslides over a broad area including shallow disrupted landslides rock falls deep seated landslides and rock avalanches some of which buried large sections of some towns and dammed the rivers the purpose of this study is to investigate correlations between the occurrence of landslides with geologic and geomorphologic conditions and seismic parameters over 56 000 earthquake triggered landslides with a total area of 811 km 2 are interpreted using aerial photographs and remote sensing images taken following the earthquake the spatial distribution of these landslides is analyzed statistically using both landslide point density lpd defined as the number of landslides per square kilometer and landslide area density lad the percentage of the area affected by landslides to determine how the occurrence of landslides correlates with distance from the epicenter distance from the major surface rupture seismic intensity and peak ground acceleration pga slope angle slope aspect elevation and lithology it is found that both lad and lpd have strong positive correlations with slope steepness distance from the major surface rupture and seismic intensity and that pre sinian schist and cambrian sandstone and siltstone intercalated with slate have the most concentrated landslide activities followed by the permian limestone intercalated with shale and devonian limestone statistical analyses also indicate that the major surface rupture has influence on the spatial distribution of landslides because lad and lpd are relatively higher on the hanging wall than on the footwall however the correlation between the occurrence of landslides with distance from the epicenter of the earthquake is complicated rather than a relatively simple negative correlation as found from other reported cases of earthquakes this is possibly due to complicated rupture processes of the earthquake

the tr method the use of slip preference to separate heterogeneous fault slip data in compressional stress regimes the surface rupture of the 1999 chi chi taiwan earthquake as a case study abstract synthetic contractional fault slip data have been considered in order to examine the validity of widely applied criteria such as the slip preference slip tendency kinematic p and t axes transport orientation and strain compatibility in different andersonian compressional stress regimes radial compression rc radial pure compression rc pc pure compression pc pure compression transpression pc trp and transpression trp are examined with the aid of the win tensor stress inversion software furthermore the validity of the recently proposed graphical tr method which uses the concept of slip preference for the separation of heterogeneous fault slip data is also examined for compressional stress regimes in these regimes only contractional faults can be activated and their slip preferences imply the distinction between real i e rc rc pc and pc and hybrid i e pc trp and trp stress regimes for slip tendency values larger than 0 6 the activated faults dip at angles from 10 to 50 but in the hybrid regimes faults can dip with even higher angles the application of the tr method is here refined by introducing two controlling parameters the coefficient of determination r2 of the final tensor ratio line ftrl and the normal or inverse distribution of the faults plotted within the final tensor ratio belt ftrb the application of the tr method on fault slip data of the 1999 chi chi earthquake taiwan allowed the meaningful separation of complex heterogeneous contractional fault slip data into homogeneous groups in turn this allowed the identification of different compressional stress regimes and the determination of local stress perturbations of the regional or far stress field generated by the 1999 chi chi earthquake this includes clear examples of stress permutation and stress partitioning caused by pre existing fault structures such as the n s trending chelungpu thrust and the ne sw trending shihkang shangchi fault zone

structure of the crust beneath the southeastern tibetan plateau from teleseismic receiver functions abstract southeastern tibet marks the site of presumed clockwise rotation of the crust due to the india eurasian collision and abutment against the stable sichuan basin and south china block knowing the structure of the crust is a key to better understanding of crustal deformation and seismicity in this region here we analyze recordings of teleseismic earthquakes from 25 temporary broadband seismic stations and one permanent station using the receiver function method we find that the crustal thickness decreases gradually from the tibetan plateau proper to the sichuan basin and yangtze platform but that significant intra crustal heterogeneity exists on shorter lateral scales 0 30 are detected beneath the southeastern margin of tibet but in the sichuan basin and southeastern yangtze platform the values are close to the global average combined with high regional heat flow and independent evidence for mid crustal layers of high electric conductivity the large intra crustal s wave velocity reduction 12 19 and the intermediate to high average crustal poisson s ratios are consistent with partial melt in the crust beneath parts of southeastern tibet these results could be used in support of deformation models involving intra crustal flow with the caveat that significant lateral variation in location and strength of this flow may occur

distribution pattern of earthquake induced landslides triggered by the 12 may 2008 wenchuan earthquake abstract this paper presents the preliminary results of an extensive study of the mapping the distribution of landslides triggered by the wenchuan earthquake in sichuan province china on 12 may 2008 an extensive landslide interpretation was carried out using a large set of optical high resolution satellite images e g aster alos cartosat 1 spot 5 and ikonos as well as air photos for both the pre and post earthquake situation landslide scarps were mapped as points using multi temporal visual image interpretation taking into account shape tone texture pattern elevation and ridge and valley orientation nearly 60 000 individual landslide scarps were mapped the landslide distribution map was compared with the inventory map that was prepared directly after the earthquake which contains about 11 000 individual landslide points through the calculation of normalized landslide isopleths maps remarkable differences were observed as the earlier inventory mapping did not consider the pre earthquake situation and did not consider all individual landslides as part of the landslide inventory landslides were identified that had blocked the drainage and had formed landslide dams the landslide distribution was compared with a number of aspects such as the seismic parameters distance to epicenter distance to fault rupture co seismic fault geometry and co seismic slip distribution and geology the most remarkable correlation found was with the co seismic slip distribution and the fault geometry landslide distribution in the section of the fault that had mainly a thrust component with low angle fault plane was found to be much higher than the sections that had steeper fault angles and a major strike slip component

landslides induced by the wenchuan earthquake and the subsequent strong rainfall event a case study in the beichuan area of china abstract the wenchuan earthquake on may 12 2008 triggered massive landslides and a subsequent strong rainfall prompted the development of new landslides as well as the reactivation of some pre existing landslides the highest seismic intensity zone of the wenchuan earthquake in beichuan china was selected as a case study to analyze the influence of the earthquake and the subsequent heavy rains on landslide evolution we selected this study area 414 km 2 since it was close to the coseismic surface rupture and because it suffered strong ground motion based on the interpretation of high resolution aerial photographs and remote sensing imagery combined with field investigation 40 pre earthquake landslides and 2221 coseismic landslides were identified with total landslide areas of 2 68 km 2 and 30 81 km 2 respectively there were 134 large over 50 000 m 2 co seismic landslides that covered a surface area of 15 54 km 2 and represented approximately 50 4 of the total area of the co seismic landslides the coseismic landslides were mainly located on the hanging wall of the causative fault and on the steep valley sides of the jian river and its tributaries a strong rainfall event occurred four months after the wenchuan earthquake and induced 969 new landslides which covered a 6 90 km 2 area and enlarged 169 existing landslides 2 48 km 2 the landslides were identified in spot5 images ultimately we found that earthquake tremors and the subsequent rainstorm severely disturbed the surface strata resulting in a large number of landslides

a review of prokaryotic populations and processes in sub seafloor sediments including biosphere geosphere interactions article i nfo sub seafloor biosphere marine microbiology prokaryotic diversity dark energy biosphere geosphere interactions a general review of the sub seafloor biosphere is presented this includes an update and assessment of prokary otic cell distributions within marine sediments current deepest 1922 m and the impact of this on global sub seafloor biomass estimates these global estimates appear relatively robust to different calculation approaches and our updated estimate is 5 39 10 29 cells taking into consideration new data from very low organic matter south pacific gyre sediments this is higher than other recent estimates which is justified as several sediments such as gas hydrate deposits and oil reservoirs can have elevated cell concentrations the proposed relationship between elevated cell concentrations and milankovitch cycles in sequential diatom rich layers at some sites demonstratesnotonlyadynamicdeepbiosphere butalsothatthedeepbiosphereisanintegralpartofearthsys tem processes over geological time scales cell depth distributions vary in different oceanographic provinces and this is also reflected in contrasting biodiversity despite this there are some clear common sub seafloor prokary otes for bacteria these are the phyla chloroflexi gammaproteobacteria planctomycetes and the candidate phylum js1 and for archaea uncultivated lineages within the phylum crenarchaeota miscellaneous crenarchaeotal group and marine benthic group b euryarchaeota sagmeg marine benthic group d thermoplasmatales associated groups and thaumarchaeota marine group i in addition spores viruses and fungi have been detected but their importance is not yet clear consistent with the direct demonstration of active prokaryotic cells prokaryotes have been enriched and isolated from deep sediments and these reflect a subset of the total diversity including spore formers that are rarely detected in dna analyses activities are generally low in deep marine sediments 10 000 times lower than in near surface sediments however depth integrated activity calculations demonstrate that sub surface sediments can be responsible for the majority of sediment activity up to 90 and hence are biogeochemically important unlike near surface sediments competitive metabolisms can occur together and metabolism per cell can be 1000 times lower than

temporal spatial rupture process of the 1999 chi chi earthquake from iris and geoscope long period waveform data using aftershocks as empirical green s functions a large earthquake m w 7 6 occurred near chi chi taiwan on 20 september 1999 utc and was followed by many moderate size aftershocks in the following days the two largest aftershocks with magnitudes m w 6 1 and 6 2 respectively were used as empirical green s functions egfs to retrieve the source time functions stfs and further image the temporal spatial rupture process of the mainshock for each station two types of stfs were retrieved one from p phases and another from s phases a total of 178 stf individuals were retrieved for source process analysis of the event from the stfs retrieved firstly similarities appeared on the stfs from most stations except that several stfs in special azimuths looked different or odd because of the focal mechanism difference between the mainshock and the egf aftershocks and secondly systematic shape variation with azimuth appeared the analysis of the stfs indicated that this event consisted of two subevents on the average the second event was about 7 sec later than the first one and the first event was about 15 larger than the second one in the moment release rate the total duration time of earthquake rupture process was about 26 sec from the image of the static slip distribution there were two slip concentrated areas on the fault plane and their centers were about 45 km away from each other the maximum slip of about 6 5 m appeared on the northern one the rupture area with the slip greater than 0 5 m was about 80 km long and 60 km wide the maximum stress drop was about 25 mpa 250 bar and the average stress drop on the entire fault was 9 2 mpa 92 bar from the snapshots of the temporal spatial variation of slip and slip rate the rupture initiated at the southern end and stopped at the northern end of the fault which suggested an overall unilateral rupture at a rupture velocity of about 2 5 km sec the depth of the initiation locus was about 20 km the rupture duration times on the subfaults were estimated a good correlation was noticed between the rupture duration time and slip amplitude of the subfaults the larger the slip amplitude the longer the rupture duration time of the subfault the maximum duration time for the subfaults was 16 sec which was about two thirds the total duration time of the earthquake rupture process in the beginning and near the end of the source process the rupture propagated like a self healing pulse of slip manuscript received 21 may 2001

impact of natural oil and higher hydrocarbons on microbial diversity distribution and activity in gulf of mexico cold seep sediments gulf of mexico cold seeps characterized by variable compositions and magnitudes of hydrocarbon seepage were sampled in order to investigate the effects of natural oils methane and non methane hydrocarbons on microbial activity diversity and distribution in seafloor sediments though some sediments were characterized by relatively high quantities of oil which may be toxic to some microorganisms high rates of sulfate reduction sr 27 9714 7 mmol m

mass movements along a rapidly uplifting river valley an example from the upper jinsha river southeast margin of the tibetan plateau because of the rapid uplift of the tibetan plateau since the middle and late pleistocene the surrounding mountainous areas of the tibetan plateau also show a rapid uplift trend the study area is located in the upper reaches of the jinsha river southeastern tibetan plateau tectonically the study area is located in the eastern segment of the jinshajiang suture zone which is the weak belt of the lithosphere affected by the rapid uplift steep slopes are formed by the rapid vertical down cutting of rivers in the studied reach under the sustained action of the gravitational field the deformation and failure of slopes readily occur to better formulate development and risk mitigation plans a mass movement inventory map at the scale of 1 50 000 was prepared for the 100 km long reach a total of 247 mass movements of different types sizes and relative ages were mapped via image interpretation and detailed field survey the statistical analysis of their spatial distributions was performed using two relative concentration indexes the correlations between the spatial distribution and six common factors were analyzed elevation slope angle slope aspect lithology active fault and river system the geomorphological survey shows that the mass movements locally play an important role in the present day landscape evolution in addition the geomorphic features indicate that the mapped giant landslides can be classified as very old landslides and they very likely occurred under a different morphoclimatic environment than that of the present

spatial distribution analysis of landslides triggered by 2008 5 12 wenchuan earthquake china abstract the 2008 5 12 wenchuan earthquake seismic magnitude mw 7 9 according to the usgs triggered a great number of landslides a spatial database of landslides is built by interpreting the remote sensing rs data which covers 11 counties severely damaged by the earthquake with area of about 31 686 12 km2 the geological settings of the study area are detailed mapped including geologic structure and lithology the digital elevation model dem of the study area with resolution of 30 m 30 m is presented to address the topographic characteristics correlations between the occurrence of landslides with geological settings i e active faults the coseismic surface ruptures geological unit slope gradient slope elevation as well as slope aspect are analyzed using spatial modeling in gis with the aids of field investigations it can be concluded that the distance to the causative faults and slope gradient are much more important than other factors landslides are clustered distributed along the causative faults of f2 and f3 and landslides incidence are dramatically decreasing with the increasing of the distance to the causative faults the landslides incidence has an obvious increase near the active faults i e f1 landslide concentration lc landslides km2 has an obvious exponent increase with slope gradient however lc has no obvious relationship with geological unit and slope elevation the difference of lc value in each geological unit each slope elevation category maybe have been the result affected by slope gradient for each geological unit each slope elevation category and distance of each geological unit each slope elevation category to causative fault zone isoseismal map reflects the incidence of landslides in some degree and lc increases dramatically with intensity increasing almost all landslides occurred in the region above vi degree statistics result also indicates that in the near field of causative faults landslides tend to have the initial sliding direction similar to the movement of the causative faults and preliminary study shows that landslides incidence varies in different slopes with different structure and consequent slopes and obsequent slopes have a higher landslides incidence than other layered slopes

microbial community structures of methane hydrate bearing sediments in the ulleung basin east sea of korea microbial communities of a methane hydrate bearing deep sediment cores collect from site ubgh2 10 from the ulleung basin east sea of korea were characterized by phylogenetic analysis on the basis of 16s rrna gene cloning quantification of key functional genes related to sulfate reduction dsra and methanogenesis mcra and that of bacteria and archaea were conducted using molecular approaches on the basis of geochemical data four subsections were selected to compare the microbial diversity relative to the presence of methane hydrate marine benthic group b mbgb and candidate division js1 js1 were the dominant taxa in the archaeal and bacterial libraries respectively throughout the core except in the deep layer interestingly anme 1b members and mcra were detected only in sulfate methane transition zone smtz however the proportions of sulfate reducing deltaproteobacteria clones and dsra copy numbers differed i e a very low proportion of clones but a sufficiently high dsra copy number relative to bacteria these results suggests that anaerobic oxidation of methane may occur mainly in smtz of ulleung basin sediment where it is performed by anme 1b via an unidentified oxidization process

qualitative and quantitative analysis on landslide influential factors during wenchuan earthquake a case study in wenchuan county abstract the 2008 wenchuan earthquake with a surface wave magnitude of 8 0 triggered numerous landslides along the longmenshan thrust fault belt in sichuan province of china the authors investigated various influential factors on the slope stability of 119 landslides in wenchuan county such as the horizontal peak ground acceleration slope angle slope height rock type and geological structure we separately developed acceleration attenuation laws for both the hanging wall and footwall side from 183 seismic stations these formulae confirmed the hanging foot wall effect had notable influence on landslide distribution density and occurrence probability further we explored the qualitative tendency of landslide distribution and occurrence probability related with each influential factor the results from the quantitative analysis by a multivariable method demonstrated that slope height horizontal peak ground acceleration and geological structure had a stronger effect on the sliding area and volume than slope angle and rock type

topographic changes and their driving factors after 2008 wenchuan earthquake abstract the 2008 wenchuan earthquake caused topographic change in the stricken areas because of the occurrence of numerous coseismic landslides the emergence of new landslides and debris flows and movement of loose materials under the driving force of high rainfall could further shape the local topography currently little attention has been paid to continuously monitoring and assessing topographic changes after the major earthquake in this research we obtained an elevation dataset 2002 2010 2013 and 2015 based on digital elevation model dem data and a dem extracted from zy 3 stereo paired images with validation by field measurement we quantitatively assessed elevation changes in different years and qualitatively analyzed spatiotemporal variation of the terrain and mass movement across the study area the results show that the earthquake affected area experienced substantial elevation changes caused by seismic forces and subsequent rainfalls high rainfall after the earthquake have become the biggest driver of elevation reduction which overwhelmed elevation increase caused by the major earthquake increased post earthquake erosion intensity has caused large amounts of loose materials to accumulate in river channels and gullies and on upper middle mountain slopes which increases the risk of flooding and geo hazards in the area

contribution of thermogenic organic matter to the formation of biogenic gas hydrate evidence from geochemical and microbial characteristics of hydrate containing sediments in the taixinan basin south china sea abstract high saturation 40 100 microbial gas hydrates have been acquired by expedition gmgs2 from the taixinan basin in this study geochemical and microbial features of hydrate containing sediments from the drilling cores gmgs2 09 and gmgs2 16 were characterized to explore their relationships with gas hydrate formation results showed that the average toc content of gmgs2 09 and gmgs2 16 were 0 45 and 0 63 respectively they could meet the threshold for in situ gas hydrate formation but were not available for the formation of high saturation gas hydrates the dominant members of bacteria at the class taxonomic level were alphaproteobacteria bacilli bacteroidia epsilonproteobacteria and gammaproteobacteria and those in archaea were marine benthic group b mbgb miscellaneous crenarchaeotic group mcg group c3 methanomicrobia and methanobacteria indicators of microbes associated with thermogenic organic matter were measured these include 1 most of the dominant microbes had been found dominant in other gas hydrates bearing sediments mud volcanos as well as oil coal deposits 2 hydrogenotrophic methanogens and an oilfield origin thermophilic methylotrophic methanogen were found dominant the methanogen community 3 hydrocarbon assimilating bacteria and other hyperthermophiles were frequently detected therefore thermogenic signatures were inferred existed in the sediments this deduction is consistent with the interpretation from the seismic reflection profiles owing to the inconsistency between low toc content and gas hydrates with high saturation secondary microbial methane generated from the bioconversion of thermogenic organic matters oil or coal was speculated to serve as enhanced gas flux for the formation of high saturation gas hydrates a preliminary formation model of high saturation biogenic gas hydrates was proposed in which diagenesis processes tectonic movements and microbial activities were all emphasized regarding to their contribution to gas hydrates formation in short this research helps explain how microbial act and what kind of organic matter they use in forming biogenic gas hydrates with high saturations

kinematic and dynamic fault slip analyses implications from the surface rupture of the 1999 chi chi taiwan earthquake the 1999 chi chi earthquake created a 100 km long surface rupture on the chelungpu thrust fault in taiwan due to convergence between the phillipine sea and eurasian plates fault slip measurements were made by several researchers from the entire length of the rupture directly following the earthquake and can thus be attributed to a single tectonic event conventional fault slip analyses are applied to these data and the results are compared with independent seismological and kinematic observations unlike many fault slip analyses complications due to multiple deformations can be categorically excluded and the results can be evaluated from the seismological and plate movement data kinematic analyses of fault slip data that are weighted by displacement show sub horizontal nw se shortening that is parallel to the plate convergence vector a single fault plane solution satisfies almost all the data right dihedra and trihedra solutions also satisfy almost all the surface rupture measurements and give 1 in a nw se orientation that is similar to the results of stress inversion and to inversion from earthquakes in the chi chi earthquake sequence despite criticisms of fault slip analysis methods these results show that fault slip analyses from data collected along major faults which have not witnessed multiple deformation events can be valid homogeneous strain and stress states exist in the sense that kinematic and dynamic solutions can be found that fit essentially all the data and these solutions have tectonic significance

logarithmic model joint inversion method for coseismic and postseismic slip application to the 2017 mw 7 3 sarpol zahāb earthquake iran

database and spatial distribution of landslides triggered by the lushan china mw 6 6 earthquake of 20 april 2013 abstract on 20 april 2013 an earthquake with mw 6 6 ms 7 0 hit lushan county sichuan province of china 30 3 n 103 e only 85 km southwest of the 2008 wenchuan mw 7 9 event the lushan shock triggered a large number of landslides with various types including highly disrupted shallow slides and rock falls deep seated landslides and large scale rock avalanches post earthquake high resolution aerial photographs and satellite images as well as a series of pre earthquake high resolution satellite images were collected to construct a detailed accurate objective and complete coseismic landslide database inventory which was validated by field investigation in selected areas based on the aerial photographs 0 2 or 0 6 m resolution that partly cover the affected area and pre earthquake satellite images 14 580 coseismic landslides were recognized and mapped in those areas without post earthquake aerial photographs coverage we mapped 7 948 more coseismic landslides based on post earthquake satellite images rapideye images with 5 m resolution and zy 3 images including panchromatic images with 2 1 m resolution and multi spectral images with 5 8 m resolution and pre earthquake satellite images the 22 528 coseismic landslides with a horizontal projection area of 18 88 km 2 and an estimated total volume of 41 56 10 6 m 3 were distributed in a nearly elliptic area of about 5 400 km 2 correlations between coseismic landslide abundances and topographic geologic and seismic factors were analyzed on 15 546 landslides of area 100 m 2 scatter plots between regional slope angle and landslide abundances in generalized homogeneous lithology combinations show no obvious relationship is present between them which challenges the conclusions of previous studies combining the lushan earthquake triggered landslides with other events on reverse and or thrust faults such as the 1999 chi chi and 2008 wenchuan shocks we found that coseismic landslides tend to occur in areas enveloped by two or more imbricated reverse and or thrust faults rather than only along the seismogenic fault the lushan event shows a higher ability of triggering landslides compared with other earthquakes of similar magnitudes which is likely due to the steep and rugged topography and fractured and densely jointed lithology resulted from long term tectonic activity the blind reverse seismogenic fault is likely also another significant factor based on detailed coseismic landslide inventory maps and databases of several recent major earthquakes such as the 2008 wenchuan 2010 haiti 2010 yushu and 2013 lushan temblors we suggest that the empirical correlations between earthquake magnitude and coseismic landslides need to be updated

neotectonics of the min shan china implications for mechanisms driving quaternary deformation along the eastern margin of the tibetan plateau the min shan region located along the eastern margin of the tibetan plateau north of the sichuan basin provides an important natural laboratory in which to study the rates and patterns of deformation and their relationship to mountain building at the margin of the plateau the topographic margin of the plateau is coincident with a north trending mountain range the min shan that stands nearly 2 km above the mean elevation of the plateau 3500 m in this region we exploit the preservation of a series of variably deformed quaternary sediments along the western flank of the range to investigate the pleistocene holocene deformation field within the min shan region mapping and field observations of remnant alluvial fans of late pleistocene age indicate that deformation within the min shan involved substantial 10 rapid down to the northwest tilting the geometry of the deposits and the partial preservation of an erosion surface beneath the basin suggest that much of the modern relief of the min shan relative to the tibetan plateau is a consequence of this late pleistocene tilting rates of tilting inferred from luminescence dating of interbedded loess have been remarkably rapid 10 8 rad yr similarly rapid rates of holocene differential rock uplift are inferred from tilted lacustrine sediments in the southwestern part of the range the range is bounded on the west by the min jiang fault zone an east vergent reverse fault however holocene alluvial terraces in headwaters of the min river are preserved across the fault in several places indicating that displacement rates on the min jiang fault are 1 mm yr active faulting only occurs along the eastern foot of the range huya fault for a short distance 60 km despite 3 km of relief on the eastern range front the relationship between these structures and the tilting observed in the min jiang basin is enigmatic the faults do not appear to exert a strong control on the rates and pattern of deformation within the basin a simple flexural model demonstrates that rates of tilting on the western flank of the min shan are too high to be simply attributed to an isostatic response to surficial loading and unloading of the lithosphere present day horizontal shortening across the min shan is geodetically determined to be less than 2 3 mm yr suggesting that only a small part of the observed tilting can be attributed to horizontal shortening thus tilting and concomitant differential rock uplift in the min shan appear to require an additional driving component we suggest that quaternary deformation along the western min shan may reflect the surface response to thickening of a weak lower crust at the margin of the tibetan plateau

mapping the deep lithospheric structure beneath the eastern margin of the tibetan plateau from gravity anomalies 1 various authors have investigated the mechanism of lateral support of the lithosphere in maintaining the uplift of the tibetan plateau based on gravity data and elastic flexural modeling in the south of the plateau across the himalayas and in the north and the northwest across the altyn tagh and west kunlun shan however the degree of the regional compensation and lateral support to the east of the tibetan plateau has remained unknown in this paper we present a lithospheric flexure model by interpreting gravity and topography to understand the first order problem of lateral support of the lithosphere at the eastern margins of the tibetan plateau the flexural modeling constrains the geometry and strength variation of the lithosphere from the eastern margin of tibet past the longmen shan ranges on to the sichuan basin a lithosphere of intermediate strength te 45 km beneath the sichuan basin is weakened te 36 km by the thrusting underneath the eastern margin of the tibetan plateau the strength variations indicate that about 10 km of the crustal material of the lithosphere has been ripped off and integrated into the thickened upper crust of the tibetan plateau which however has no appreciable strength the stiffness of the lithosphere keeps the tibetan plateau relatively stable at its eastern margin and enables the weight of the plateau to be supported in the east by the sichuan lithospheric deformation in the southern longmen shan area is more pronounced than in the northern region

evaluation of landslide mechanisms characterized by high speed mass ejection and long run out based on events following the wenchuan earthquake abstract in the 2008 wenchuan earthquake the mass ejection type of high speed and long run out landslide was an unusual hazard characterized by its dramatic phenomenon of a huge slope mass launching into the air and becoming airborne for a long distance quantitative and qualitative combined techniques were applied to reveal the formation mechanism of this type of landslide four prerequisites critical to form mass ejection are identified high position of the toe of the surface of rupture critical height and critical inclination of slope sufficient open space in the movement direction and adequate take off speed of ski jump like mass ejection these four area specific prerequisites provide a promising approach for screening and targeting the potential landslides subsequently a dynamic reliability analysis method that considers the feature of energy time distribution is proposed this site specific method provides a more credible evaluation by emphasizing the most significant period within the whole earthquake duration finally an aerodynamic inverse method combined with an energy conservation based method is applied in the quantitative evaluation to calculate take off speed of mass ejection this paper provides a viable solution for regional screening and site assessment for new potential targets of this type of landslide

imaging the ramp decollement geometry of the chelungpu fault using coseismic gps displacements from the 1999 chi chi taiwan earthquake abstract we use coseismic gps data from the 1999 chi chi taiwan earthquake to estimate the subsurface shape of the chelungpu fault that ruptured during the earthquake studies prior to the earthquake suggest a ramp decollement geometry for the chelungpu fault yet many finite source inversions using gps and seismic data assume slip occurred on the down dip extension of the chelungpu ramp rather than on a sub horizontal decollement we test whether slip occurred on the decollement or the down dip extension of the ramp using well established methods of inverting gps data for geometry and slip on faults represented as elastic dislocations we find that a significant portion of the coseismic slip did indeed occur on a sub horizontal decollement located at 8 km depth the slip on the decollement contributes 21 of the total modeled moment release we estimate the fault geometry assuming several different models for the distribution of elastic properties in the earth homogeneous layered and layered with lateral material contrast across the fault it is shown however that heterogeneity has little influence on our estimated fault geometry we also investigate several competing interpretations of deformation within the e w trending rupture zone at the northern end of the 1999 ground ruptures we demonstrate that the gps data require a 22 to 35 km long lateral ramp at the northern end contradicting other investigations that propose deformation is concentrated within 10 km of the chelungpu fault lastly we propose a simple tectonic model for the development of the lateral ramp

seismic images of crust and upper mantle beneath tibet evidence for eurasian plate subduction seismic data from central tibet have been combined to image the subsurface structure and understand the evolution of the collision of india and eurasia the 410 and 660 kilometer mantle discontinuities are sharply defined implying a lack of a subducting slab beneath the plateau the discontinuities appear slightly deeper beneath northern tibet implying that the average temperature of the mantle above the transition zone is about 300 c hotter in the north than in the south there is a prominent south dipping converter in the uppermost mantle beneath northern tibet that might represent the top of the eurasian mantle lithosphere underthrusting the northern margin of the plateau

response of seismicity to coulomb stress triggers and shadows of the 1999 mw 7 6 chi chi taiwan earthquake 1 the correlation between static coulomb stress increases and aftershocks has thus far provided the strongest evidence that stress changes promote seismicity a correlation that the chi chi earthquake well exhibits several studies have deepened the argument by resolving stress changes on aftershock focal mechanisms which removes the assumption that the aftershocks are optimally oriented for failure here one compares the percentage of planes on which failure is promoted after the main shock relative to the percentage beforehand for chi chi we find a 28 increase for thrust and an 18 increase for strike slip mechanisms commensurate with increases reported for other large main shocks however perhaps the chief criticism of static stress triggering is the difficulty in observing predicted seismicity rate decreases in the stress shadows or sites of coulomb stress decrease detection of sustained drops in seismicity rate demands a long catalog with a low magnitude of completeness and a high seismicity rate conditions that are met at chi chi we find four lobes with statistically significant seismicity rate declines of 40 90 for 50 months and they coincide with the stress shadows calculated for strike slip faults the dominant faulting mechanism the rate drops are evident in uniform cell calculations 100 month time series and by visual inspection of the m 3 seismicity an additional reason why detection of such declines has proven so rare emerges from this study there is a widespread increase in seismicity rate during the first 3 months after chi chi and perhaps many other main shocks that might be associated with a different mechanism

evaluation of factors controlling earthquake induced landslides caused by chi chi earthquake and comparison with the northridge and loma prieta events over 10 000 landslides were triggered by the september 21 1999 chi chi earthquake a large number of these landslides have been mapped from spot images and a smaller number were described in a detailed field investigation geographic information systems gis was used to conduct a spatial characterization of the slope failures including distribution of type size slope angle bedrock geology ground motion and distance from earthquake source the most abundant landslides were shallow disaggregated rock and soil slides landslides occurred primarily in tertiary sedimentary rocks which are well known for their susceptibility to landsliding in many parts of the world landslide concentration values diminish beyond epicentral distances of 40 and 70 km from the epicenter and the surface projection of the fault plane respectively ground motion was found to be the most significant factor in triggering the shallow landslides in the chi chi earthquake overall 74 of all slope failures occurred in regions with vertical ground motions greater than 0 2g and 81 of all slope failures occurred in the region with mean horizontal peak ground accelerations pga greater than 0 15g these factors were used to compare landslides generated by the chi chi earthquake to the landslides triggered by the 1989 loma prieta earthquake and the 1994 northridge earthquake the major difference in distribution of landslides between the chi chi earthquake and the two california earthquakes was the distribution of slope angles in the chi chi earthquake 90 of the failures occurred on slopes steeper than 45 while more than 80 of failures occurred on slopes less than 50 in california apparently reflecting much steeper and tectonically more active geologic setting in taiwan

a multiple time window rupture model for the 1999 chi chi earthquake from a combined inversion of teleseismic surface wave strong motion and gps data 1 we present the results of a comprehensive analysis of the rupture process of the 1999 chi chi taiwan earthquake using a broad array of seismic as well as geodetic data spanning a very wide frequency band our results indicate that the rupture was quite smooth with the slip concentrated in a wide arcuate region north of the epicenter with very little slip to the east or south we found a moment of 3 3 1027 dyn cm which is consistent with the long period determinations for this earthquake the rupture velocity is approximately 2 25 km s and is quite uniform across the fault we have tested both a single fault plane model as well as a composite fault model with a second e w striking plane to the north of the rupture to improve the fit of the geodetic data overall the differences in slip distribution between the two models are negligible but the fit to the gps data is significantly better for the composite model which is thus our preferred solution this model is similar to other rupture models as far as the large scale features are concerned but differs for the smaller asperities that are present in other models but not as much in ours these are usually poorly constrained and with the use of the geodetic data we believe that there is little evidence for a significant amount of slip away from our main slip concentration

meso and microstructural analysis of coseismic shear zone of the 1999 mw 7 6 chi chi earthquake taiwan the surface rupture of the 1999 m w 7 6 chi chi taiwan earthquake was controlled primarily by the pre existing chelungpu fault zone which is distributed in a wide zone of up to 60 m although the main coseismic slip is localized in a narrow shear zone of 0 3 cm the chelungpu fault zone is composed of cataclasite fault breccia and gouge zones that are well observed in both the fault outcrops and the drill cores taken throughout the fault zone the foliations developed in the cataclasite and fault breccia zones are oriented parallel to that of the fault gouge zone where the main coseismic slip occurred the structural analyses of the shear zone and fault rocks show that the chelungpu fault zone has slipped as a thrust fault with a significant left lateral slip component since its formation in the pleistocene this oblique thrust motion is caused by the southeast northwest oblique convergence between the philippine sea plate and the eurasian plate

coseismic and initial postseismic deformation from the 2004 parkfield california earthquake observed by global positioning system electronic distance meter creepmeters and borehole strainmeters global positioning system gps electronic distance meter creepmeter and strainmeter measurements spanning the m 6 0 parkfield california earthquake are examined using these data from 100 sec through 9 months following the mainshock the omori s law with rate inversely related to time 1 t p and p ranging between 0 7 and 1 3 characterizes the time dependent deformation during the postseismic period these results are consistent with creep models for elastic solids with an accurate function of postseismic response the coseismic displacements can be estimated from the high rate 1 min sampling gps and the coseismic displacements are approximately 75 of those estimated from the daily solutions consequently fault slip models using daily solutions overestimate coseismic slip in addition at 2 months and at 8 months following the mainshock postseismic displacements are modeled as slip on the san andreas fault with a lower bound on the moment exceeding that of the coseismic moment online material data description and supplementary figures tables and data used in models and time series analysis

crustal earthquake instability in relation to the depth variation of frictional slip properties recent stability studies using constitutive relations of the type found by dieterich ruina and others to describe frictional slip of rocks in the laboratory have provided a new explanation of the depth cutoff of shallow crustal earthquakes the class of friction laws discussed has the property that the sliding stress depends on normal stress temperature slip rate and slip history for sliding at a fixed slip rate v and fixed environment e g normal stress temperature etc the shear strength evolves toward a steady state value ss v stability analysis show that for d ss v dv 0 velocity strengthening implies stable steady state sliding at least for a broad class of constitutive laws more fully described in the paper experiments by dieterich and by tullis and weeks on westerly granite with mature sliding surfaces indicate that d ss v dv is negative at room temperature whereas higher temperature experiments by stesky show that d ss v dv becomes positive above approximately 300 c therefore in the case of the earth where temperature increases with depth the above observations seem to suggest that the depth cutoff of crustal earthquake activity can be understood in terms of the variation of the frictional response with depth from a regime with d ss v dv 0 this is not inconsistent with but rather refines the suggestion by sibson and others that the depth cutoff is due to a transition from brittle friction to ductile flow further our results show definitively that the shallow depth confinement of seismicity is compatible with a model in which deformation is localized to a fault zone extending well below the seismogenic depth the depth confinement does not require a model showing transition to a zone of broadly distributed creep flow beneath the seismogenic zone following mavko a two dimensional quasi static strike slip fault model is analyzed but using different numerical procedures and a depth variation of frictional properties based on the laboratory data mentioned above and the lachenbruch sass depth variation of temperature for the san andreas fault the resulting predictions of such features as the confinement of crustal earthquakes to shallow depths the development of locked patches the recurrence time for the seismic cycle the seismic stress drop and displacement etc are generally in agreement with the observed characteristics of large scale strike slip earthquakes along the san andreas fault calculations based on the laboratory data predict for example that stick slip nucleates around 5 7 km that large seismic motion occurs around the nucleation depth and above but diminishes gradually to zero at 13 15 km depths that rapid postseismic creep occurs over another 3 4 km depth and that at greater depths steady slip consistent with the average plate velocity is only modestly perturbed by the earthquakes occurring above the most uncertain parameter is the slip weakening distance l for evolution of fault surface state we illustrate how features of the predicted earthquake cycles vary with l over the range for which calculations are feasible

velocity field of gps stations in the taiwan area abstract the 131 stations of the taiwan gps network were surveyed 4 6 times from 1990 to 1995 with dual frequency geodetic receivers the standard deviation of an observed baseline length with its linear trend removed is in the range of 6 10 mm for a 3 120 km long baseline the average rates of length change for all baselines of the network and those from nine continuously monitoring permanent stations are used in a least squares adjustment to estimate the velocities of the gps stations relative to paisha penghu situated at the chinese continental margin to the south of fengping in the northern coastal range the velocity vectors of stations in lanhsu lutao and the coastal range trend in the directions of 306 322 with rates of 56 82 mm yr in contrast there is a dramatic decrease in the rates to the north of fengping this may be caused by the motion along the ne sw trending thrusts which obliquely cut the northern coastal range a discontinuity of about 30 mm yr in the rates along with a remarkable change in the directions of station velocity is observed across the longitudinal valley then the moving directions gradually shift to the west for the stations in the western foothills in the kaohsiung pingtung coastal area the station velocities are even directed toward the southwest to the north of the peikang high the velocity vectors of the stations change direction from the west gradually to the north and finally to the east and southeast significant nw se extensional deformation is found in the ilan plain and northern taiwan in general the pattern of the velocity field for gps stations in the taiwan area is quite consistent with the directions of present day tectonic stress

effects of active fault types on earthquake induced deep seated landslides a study of historical cases in japan abstract we investigated the relationship between the distribution of deep seated landslides dsls landslide volume 10 5 m 3 induced by inland earthquakes as well as the distribution of corresponding active faults by compiling preexisting documents on historical dsl occurrence records the following points are found 1 the dsls induced by reverse fault earthquakes tend to occur equally within a wide range of about 20 km from the faults whilst 80 of dsls induced by strike slip fault earthquakes are concentrated within a small range of about 5 km from the faults 2 most of the dsls are distributed on the hanging wall side of the active faults 3 the distribution of some historical dsls may reflect the directivity of the seismic waves of the historical earthquakes the minimum peak ground velocity pgv and peak ground acceleration pga during earthquakes that can induce dsls are estimated to be 15 20 cm s 1 and 300 400 cm s 2 although most of the dsls examined were induced by strike slip fault earthquakes with pgv 60 cm s 1 and pga 900 cm s 2 this discrepancy may be attributed to a possible limitation of the proposed equation which was established mainly for cases of reverse fault earthquakes it is implied that the type of fault the side of the epicenter location hanging wall footwall side and the directivity of seismic waves should be considered for assessing the distribution of ground motion in terms of dsl occurrence and that these factors may reflect the level of risk for earthquake induced landslides around active faults

3d velocity structure around the source area of the 1999 chi chi taiwan earthquake before and after the mainshock 3d v p and v p v s models for the source area before and after the chi chi earthquake are derived from a tomographic inversion of seismic travel time data from the taiwan central weather bureau seismic network cwbsn resulting 3d velocity models reveal a strong lateral variation in the crust particularly at a depth range of 5 to 25 km along the trend of the dipping chelungpu thrust in general low v p and high v p v s anomalies are found in and around the source volume of the chi chi earthquake a volume centered around the entire 100 km 40 km chelungpu rupture surface we pay special attention to the crustal properties and their changes due to the chi chi event and the association of the crustal anomalies with seismicity combining the results with those of other geological and geophysical surveys the crustal anomalies are interpreted as images of a highly fractured and fluid filled chi chi source region fluid overpressure is known to reduce the strength of the fault zone and in this case may have initiated the nucleation of the chi chi earthquake the v p models obtained before and after the chi chi event show some interesting heterogeneities regions of low v p anomaly appear to have further expanded with the occurrence of the chi chi earthquake the v p v s model shows high anomalies near the source rupture especially near where the rupture is believed to have nucleated after the chi chi event the v p v s model shows a substantial change that may reflect an outward shift of the fluid filled fractured source region this shift is shown by a general expansion in v p v s anomalies to a broader region e g where two intensive aftershock clusters occurred and a significant v p v s reduction to more normal values near the chelungpu rupture we attribute these changes in v p and v p v s anomalies as well as the expansion and shift of the anomalous regions to be a response to the localized stress change caused by the slip of the chi chi rupture the location of the seismic events is correlated with that of the crustal v p and v p v s anomalies large events appear to occur in the transition zones of both v p and v p v s anomalies this finding may be of use in the identification of weakened crustal regions in a seismic zone thus suggesting where impending large earthquakes are likely to occur all input data and initial and final models of this article are given as electronic files in the cd attached to the end of this issue

co seismic displacements of the 1994 northridge california earthquake the 17 january 1994 northridge california earthquake significantly deformed the earth s crust in the epicentral region displacements of 66 survey stations determined from global positioning system gps observations collected before and after the earthquake show that individual stations were uplifted by up to 417 5 mm and displaced horizontally by up to 216 3 mm using these displacements we estimate parameters of a uniform slip model fault geometry and slip are estimated independent of seismological information using monte carlo optimization techniques that minimize the model residuals the plane that best fits the geodetic data lies 1 to 2 km above the plane indicated by aftershock seismicity modeling for distributed slip on a coplanar yet larger model fault indicates that a high slip patch occurred up dip and northwest of the mainshock hypocenter and that less than 1 m of slip occurred in the uppermost 5 km of the crust this finding is consistent with the lack of clear surface rupture and with the notion that the intersection with the fault that ruptured in 1971 formed the up dip terminus of slip in the northridge earthquake displacements predicted by either of these simple models explain most of the variance in the data within 50 km of the epicenter on average however the scatter of the residuals is twice the data uncertainties and in some areas there is significant systematic misfit to either model the co seismic contributions of aftershocks are insufficient to explain this mismatch indicating that the source geometry is more complicated than a single rectangular plane

seismically induced mass movements and volumetric fluxes resulting from the 2010 mw 7 2 earthquake in the sierra cucapah mexico the observation that sediment flux from mountain ranges struck by high magnitude earthquakes can be strongly influenced by coseismic mass movements brings into question the nature of coseismic deformation as a net contributor to mountain building to better constrain the role of high magnitude earthquakes in orogenesis high resolution data of earthquake induced mass wasting is required for areas of differing tectonic morphological and climatic settings here we compare the erosional flux to the tectonic flux associated with the 2010 mw 7 2 sierra el mayor earthquake in mexico and examine the landslide patterning of coseismic mass movements associated with this event the ruptured fault system has a significant strike slip component with subsidence along the eastern flank and uplift on the western flank of the range peak ground acceleration was highest along the steepest sections of the range such that the frequency of landslide occurrence was strongly correlated to slope gradient both vertical and horizontal coseismic displacement demonstrated a strong control over landslide initiation this result suggests that strike slip systems experience very different landslide patterning to thrust faults during earthquakes based on interferometric analysis of synthetic aperture radar images the earthquake resulted in a total uplifted volume of 41 6 106 m3 and a loss of 95 2 106 m3 due to subsidence this suggests a net tectonic volumetric flux of 53 6 106 m3 sediment mobilisation by coseismic landslides is estimated at 2 7 106 m3 derived from a manually mapped inventory using spot 5 multispectral imagery thus the net volume loss through coseismic subsidence of the mountain range generated a strongly negative mass flux which was only marginally enhanced by mass wasting

the effect of the wenchuan earthquake on the fluvial morphology in the longmen shan eastern tibetan plateau discussion and speculation abstract although large earthquakes can have significant impacts on the geomorphology of mountain rivers the consequences of such impacts remain poorly understood the ms 8 0 wenchuan earthquake of 12 may 2008 created knickpoints waterfalls in the river systems of the longmen shan eastern tibet plateau in addition to numerous landslides along rivers in this study we use high resolution remote sensing images and field surveys to examine how the baisha and jianjiang river channels responded to the wenchuan earthquake the morphological response along the baisha river was a knickpoint with a height of 4 5 m which was studied from 2008 to 2012 however the river did not show rapid incision via knickpoint migration during the post earthquake period in fact post seismic flooding destroyed the face of the co seismic knickpoint the rapid removal of the knickpoint suggests that the abrupt vertical displacement associated with the earthquake did not exceed the adjustment threshold of the fluvial dynamic equilibrium and so was unable to drive rapid morphological change at the local scale along the jianjiang river the average meander migration rate of the beichuan reach was 2 8 m yr between 2001 and 2008 but increased to 51 1 m yr during the five years following the 2008 wenchuan earthquake this rapid increase in the meander migration rate is attributed to excess sediment supplied to the river as a consequence of the earthquake these two case studies indicate that the wenchuan earthquake caused channel aggradation rather than a significant increase in river incision by locally generating relief across the river

fault slip inverted from surface displacements during the 1999 chi chi taiwan earthquake we use coseismic surface displacement data to determine the slip distribution on the chelungpu fault during the 1999 chi chi taiwan earthquake the surface displacements were obtained from both gps surveys and integrations of near field strong ground motions the fault rupture is taken as a series of dislocations along the chelungpu fault in a homogeneous elastic half space using this assumption we are able to find both a least squares solution and optimal solutions from genetic algorithm inversion with a step wise rake constraint our results show that with the rake constraint the resulting rupture features are more reasonable and more consistent with geologic observations than with the least squares solution we also evaluate the influence of fault geometry by calculating slip distributions on a simplified 2d fault plane and a more sophisticated 3d fault surface noting that the 3d rupture model can greatly reduce model misfit when compared with the 2d rupture model both models do show however that slip dramatically increases from the hypocenter toward the northern end of the chelungpu fault and that right lateral slip is found at a large asperity near the southern end of the chelungpu fault at depths below 10 km our models predict a much larger average slip than others derived from body wave inversions we interpret this inconsistency to be a result of partitioning of aseismic sliding due to mineral composition state of stress and or frictional heat

resolution of fault slip along the 470 km long rupture of the great 1906 san francisco earthquake and its implications data from all available triangulation networks affected by the 1906 earthquake have been combined to assess the trade off between slip resolution and its uncertainty and to construct a conservative image of coseismic slip along the rupture because of varying network aperture and station density slip resolution is very uneven although slip is determined within uncertainties of 1 0 m along 60 of the fault constraints are poor on the remaining mostly offshore portions of the rupture slip decreases from maxima of 8 6 and 7 5 m at shelter cove and tomales bay to 4 5 m near mount tamalpais and 2 7 m at loma prieta the geodetically derived slip distribution is in poor agreement with estimates based on analysis of s wave seismograms probably because these waves register only 20 30 of the total seismic moment obtained from longer period surface waves consideration of a range of fault geometries for 1906 slip near loma prieta indicates right lateral motions lie between 2 3 and 3 1 m these values are considerably greater than the 1 5 m of measured surface slip on which several assessments of high earthquake hazard for this fault segment were based this factor along with the absence of 1989 slippage where 1906 surface slip was used to make the forecasts casts doubt on some claims of success in predicting the 1989 m 6 9 loma prieta earthquake

coseismic reverse and oblique slip surface faulting generated by the 2008 mw 7 9 wenchuan earthquake china the mw 7 9 wenchuan china earthquake ruptured two large thrust faults along the long menshan thrust belt at the eastern margin of the tibetan plateau this earthquake generated a 240 km long surface rupture zone along the beichuan fault and an additional 72 km long surface rupture zone along the pengguan fault maximum vertical and horizontal offsets of 6 5 m and 4 9 m respectively were measured along the beichuan fault a maximum vertical offset of 3 5 m was measured along the pengguan fault coseismic surface ruptures integrated with aftershocks and industry seismic profiles show that two imbricate structures have ruptured simultaneously resulting in the largest continental thrust event ever documented large oblique thrusting observed during this earthquake indicates that crustal shortening is an important process responsible for the high topography in the region as everywhere along the edge of tibetan plateau

coseismic displacements of the footwall of the chelungpu fault caused by the 1999 taiwan chi chi earthquake from insar and gps data abstract the differential sar interferometry technique interferometric synthetic aperture radar insar is applied on the chelungpu fault surface rupture zone of the september 20 1999 taiwan chi chi earthquake using six ers 2 images covering the period from february 1999 to january 2000 as compared with available geodetic data insar measurements result in more extensive analysis because of high spatial sampling and centimetric accuracy however coseismic displacements can be evaluated only on the footwall of the fault the analysis of interferograms shows the existence of a linear trend in phase difference mainly caused by orbital errors which we removed from interferograms using gps data the corrected interferograms provide a precise map of the insar component of the coseismic displacement showing a continuous decrease over the footwall from a maximum of 36 7 cm at the fault east of taichung city to a value of about 5 cm at the coastline 30 km further west the map analysis reveals that the changhua fault whose surface trace is located about 20 km west of the chelungpu one and the tuntzuchio fault influence the displacement field we interpret this in terms of minor reactivation of these faults triggered by the earthquake a 1 7 cm uncertainty estimated from the gps data is proposed to quantify the precision of the map beyond this single value we highlight the interest of having several coseismic interferograms to evaluate the reliability of the map in a more comprehensive way comparisons with displacements inferred from models of slip distribution inverted without insar data highlight the advantage of carrying out a joint inversion including our results as new constraints

continuous deformation of the tibetan plateau from global positioning system data global positioning system velocities from 553 control points within the tibetan plateau and on its margins show that the present day tectonics in the plateau is best described as deformation of a continuous medium at least when averaged over distances of 100 km deformation occurs throughout the plateau interior by ese wnw extension and slightly slower nne ssw shortening relative to eurasia material within the plateau interior moves roughly eastward with speeds that increase toward the east and then flows southward around the eastern end of the himalaya crustal thickening on the northeast ern and eastern margins of the plateau occurs over a zone 400 km wide and cannot be the result of elastic strain on a single major thrust fault shortening there accommodates much of india s penetration into eurasia a description in terms of movements of rigid blocks with elastic strain associated with slip on faults between them cannot match the velocity field

paleoseismological events in the seismic gap between the 2008 wenchuan and the 2013 lushan earthquakes and implications for future seismic potential abstract the aftershocks of the 2008 wenchuan and 2013 lushan earthquakes delineated a prominent 60 km long seismic gap the uncertainty regarding the near future seismic potential of this seismic gap has become of increasing importance to both the scientific community and the public using paleoseismology this study investigated the occurrence of the last major event in the seismic gap and then considered the future seismic potential based on image interpretation trench excavation radiocarbon and optically stimulated luminescence dating and comparisons with historical earthquake rupture lengths the most recent paleoearthquake estimated magnitude m6 5 7 0 along the shuangshi dachuan fault sdf which is the southern segment of the longmen shan fault was constrained to 640 1330 ce very possibly 876 ce according to the most recent geological and geophysical findings we suggest that the seismic gap i e the sdf could be capable of generating m6 0 7 0 earthquakes but that the likelihood of such an occurrence in the near future is not very high

subduction of the indian lithosphere beneath the tibetan plateau and burma abstract subduction of the indian lithosphere under eurasia plays an important role in the tectonic evolution of the tibetan plateau and surrounding regions to improve our knowledge of pertinent mantle structures through tomographic imaging we combine p wave arrival time data from temporary arrays in tibet and stations of the chinese seismograph network with reprocessed data from the international seismological centre the new images reveal considerable spatial variations in mantle structure along the collision zone and the horizontal distance over which presumed continental indian lithosphere slides northward beneath the plateau decreases from west where it underlies the himalayas and the entire plateau to east where no indication is found for present day underthrusting beyond the himalayan block and indus tsangpo suture p wavespeed appears low in the shallow mantle beneath much of central and eastern tibet these observations suggest that indian lithosphere underlies only the southwestern part of the plateau and that the central and northeastern part is underlain by lithosphere of asian origin the continental parts of the indian plate that currently underthrust or subduct below the plateau appear generally detached from the oceanic slab fragments that subducted longer ago and that have been detected deeper in the mantle except perhaps in the central part of the collision zone 80 90 e this suggests that ongoing india eurasia collision must increasingly be driven by other forces such as subduction of the indian plate further west and east e g beneath indochina our images reveal structures associated with eastward subduction along the burmese arc southeast of the eastern himalayan syntaxis the tengchong volcanic complex in southwest china is marked by slow wave propagation to 150 km depth suggesting a causal link to subduction along the burmese arc the low velocities beneath the red river fault region extend to greater depth and may be related to upper mantle processes further southeast

seismic response of the lengzhuguan slope caused by topographic and geological effects abstract earthquake induced slope failure often results in a large loss of life and property and thus understanding how a slope responds to seismic shaking can reveal the mechanism and movement of this kind of phenomenon after the 2008 wenchuan earthquake a dense array of strong earthquake seismographs were deployed along the lengzhuguan slope luding county sichuan province southwest china to study the seismic response of the slope three main shocks were recorded in 2014 and 2015 with epicenter distances between 34 km and 70 km observation data show that the ground motion was polarized in the direction perpendicular to the elongation direction of the ridge near 50 azimuth from north with an amplification coefficient 10 and a ground motion amplification frequency band between 1 5 and 2 5 hz the results of a series of numerical simulation experiments conducted using the finite difference method indicate that the observed seismic response characteristics of the lengzhuguan slope can be reproduced only by a heterogeneous model containing a loose deposit layer with a thickness of 30 m it was found that geological and topographic conditions resulted in complex slope seismic response characteristics that were coupled in both time and frequency and the geological conditions dominated the seismic response of the slope in terms of co seismic landslide hazard more attention should be given to subsurface lithology and rock mass structure

dynamic response of rock slopes to oblique incident sv waves abstract most dynamic response analyses of rock slopes only consider the vertical incidence of seismic waves however obliquely incident waves dominate in near field seismic areas this paper presents a new seismic input method that considers near field oblique incidence based on mechanisms of artificial viscous boundaries and the influence of incident angle on the dynamic response of rock slopes three numerical model slopes with different slope angles of 30 45 and 60 are excited with the el centro earthquake record assuming varying incident angles from 0 to 90 the results show that the incident angle significantly affects the dynamic response of the slopes the most damaging incident directions are approximately perpendicular to the slope surface rather than in the vertical direction the dynamic response of the slopes will be underestimated if only the vertical incidence is considered the incident angle affects the reflection wave field in the slope and the areas affected by the reflection waves decrease with increasing slope angle however the predominant period of the response spectrum of the rock slopes is not sensitive to the incident angle and location this study unveils the dynamic mechanism of earthquake induced rock slides which is of significance for earthquake hazard prevention

stochastic finite fault modeling of ground motions from the 1999 chi chi taiwan earthquake application to rock and soil sites with implications for nonlinear site response the stochastic method for simulating strong ground motions from finite faults is applied to the records of the 1999 chi chi taiwan earthquake the method involves discretization of the fault plane into smaller subfaults each of which is assigned an x 2 spectrum the contributions from all subfaults are empirically atten uated to the observation site and summed to produce the synthetic acceleration time history the method is initially calibrated against the data recorded at 24 rock sites located within 7 120 km from the mainshock hypocenter and providing a broad azimuthal coverage of the fault plane the accuracy of the simulations is quantified through the model bias defined as the logarithm of the ratio of the observed to simulated spectrum averaged over all stations the calibrated model for the chi chi event has a near zero average bias in reproducing the ground motions at rock sites in the frequency range from 0 1 to 20 hz an unusually low value is found for the radiation strength factor s controlling the high frequency radiation level and directly related to the maximum slip velocity on the fault compared with the mean value found for north american earthquakes this result reflects the observed low peak ground ac celerations of the chi chi mainshock and physically its lower than usual slip ve locities the calibrated model is then used to simulate soil site site class d records using the linear response assumption the simulated soil site input motions are amplified by the weak motion amplification functions estimated by the spectral ratio technique from available aftershock records this analysis reveals an average reduction in strong motion amplification to about 0 5 0 6 of that in weak motions with an ac celeration threshold for detectable nonlinearity near 200 300 cm sec 2 however the derivation of soil site specific weak motion amplification was limited by the amount of aftershock data available further improvement in the quantification of nonlinear soil response during the chi chi earthquake may be possible with the release of additional aftershock datasets

inversion of source parameters and site effects from strong ground motion records using genetic algorithms the low frequency flat levels and corner frequencies of the aftershocks of the kobe earthquake together with the site effects of the recording stations are inverted by using genetic algorithms all records were corrected by the quality factor q of propagation path and for each aftershock a different omega squared model was assumed such that the low frequency flat levels and corner frequencies would minimize the standard deviation of the site effects at all stations it was observed that site effects for rock sites showed significant amplification at high frequencies this amplification was found to correlate with spectral ratios of records located at 70 m depth and at the surface for one of the stations after estimating the seismic moment and the stress drop it was observed that the relation of the seismic moment m0 versus the corner frequency fo followed the scaling law m0 fo 3 large values of stress drop were found around asperities on the fault zone and at depth

surface wave array tomography in se tibet from ambient seismic noise and two station analysis ii crustal and upper mantle structure summary we determine the 3 d shear wave speed variations in the crust and upper mantle in the southeastern borderland of the tibetan plateau sw china with data from 25 temporary broad band stations and one permanent station interstation rayleigh wave phase velocity dispersion curves were obtained at periods from 10 to 50 s from empirical green s function egf derived from ambient noise interferometry and from 20 to 150 s from traditional two station ts analysis here we use these measurements to construct phase velocity maps from 10 to 150 s using the average interstation dispersion from the egf and ts methods between 20 and 50 s and estimate from them with the neighbourhood algorithm the 3 d wave speed variations and their uncertainty the crust structure parametrized in three layers can be well resolved with a horizontal resolution about of 100 km or less because of the possible effect of mechanically weak layers on regional deformation of particular interest is the existence and geometry of low shear velocity layers lvls in some regions prominent lvls occur in the middle crust in others they may appear in the lower crust in some cases the lateral transition of shear wave speed coincides with major fault zones the spatial variation in strength and depth of crustal lvls suggests that the 3 d geometry of weak layers is complex and that unhindered crustal flow over large regions may not occur consideration of such complexity may be the key to a better understanding of relative block motion and patterns of seismicity

comment on spatial distribution analysis of landslides triggered by 2008 5 12 wenchuan earthquake china by shengwen qi qiang xu hengxing lan bing zhang jianyou liu engineering geology 116 2010 95 108

frictional strength of fault gouge in taiwan chelungpu fault obtained from tcdp hole b abstract three fault zones fzb1136 fzb1194 and fzb1243 are found in core samples in hole b borehole penetrating through the chelungpu fault central taiwan that activated at the 1999 taiwan chi chi earthquake each fault zone is composed of a black gouge zone bgz and a gray gouge zone ggz surrounded by a fault breccia zone bz and or fracture damaged zone fz we conducted tri axial friction experiments on samples collected from subzones of the above three fault zones under the 1 km depth ambient condition with axial shortening rates of 0 1 to 10 m s to investigate frictional strength and its velocity dependence we found that the coefficient of friction is 0 3 for the bgz at fzb1136 1136bgz which is lower than those at other fault zones this result indicates that fault slip at the chi chi earthquake occurred at the 1136bgz the estimated frictional strength profile across fzb1136 was that the frictional strength was the lowest the coefficient of friction was 0 3 for the bgz and increased up to 0 5 for undeformed host rock with increasing distance from the bgz presence of the intermediate frictional strength zone consisting of the ggz and the bz suggests a development of off fault damage zone where deformation occurred not only in the bgz but also in the intermediate zone this feature should be important to estimate total fracture energy released during earthquakes we also suggest that coefficients of friction and the velocity dependences of the samples are closely related to localization of shear deformation and clay content respectively

static stress transferred by the 1999 chi chi taiwan earthquake effects on the stability of the surrounding fault systems and aftershock triggering with a 3d fault slip model we investigated the effect of changes in static stress caused by the 1999 m l 7 3 chi chi earthquake on the surrounding fault systems in taiwan we examined this problem from two perspectives first we applied a statistical test for the hypothesis of static stress triggering by comparing the distributions of the coulomb failure stress changes on the focal mechanism nodal planes both before and after the mainshock since preshocks could obviously not have been affected by the mainshock the deviation of these distributions determined the significance of static stress triggering second we calculated the coulomb failure stress changes on the chukou and meishan faults in specified slip directions to evaluate the stability of these two active faults after the chi chi earthquake the static stress changes were obtained by applying the theory of dislocation in an elastic half space to a 3d rupture model derived from the surface displacements associated with the chi chi earthquake our results showed that the distributions of the coulomb failure stress changes for events preceding and following the chi chi earthquake were significantly different yet consistent with the hypothesis of static stress triggering we also found that both the chukou and the meishan faults were in stress shadows at depths shallower than 10 km however because a number of aftershocks fell in these stress shadows it is possible that other mechanisms such as dynamic stress were responsible for triggering these events manuscript received 6 november 2000

a large landslide triggered by the 2008 wenchuan m8 0 earthquake in donghekou area phenomena and mechanisms abstract during the 2008 wenchuan earthquake more than 60 000 landslides were triggered resulting in about 20 000 casualties among these landslides a catastrophic one occurred in donghekou area of qingchuan county donghekou landslide had a volume of about 1 107 m3 traveled fast for approximately 2 km killing about 780 people the source area consisted of unstable sedimentary strata and the runout path was made of colluvial deposits during the earthquake the colluvial deposits started to move first before the arrival of the displaced landslide debris from the main source area we performed undrained cyclic ring shear tests on samples taken from the runout path and concluded that liquefaction of the runout path material enhanced the mobility of the debris material a fumarole was identified on the upper part of the runout path 6 months later we analyzed the gas and water venting out and concluded that the fumarole was not the result of fault movement it resulted instead from the weathering of slate from the source area the long travel landslide materials blocked two rivers forming two landslide dams that breached with the occurrence of overtopping to better understand the internal structure of the landslide deposits and then provide evidence for a rational plan of countermeasures to stabilize the landslide dams we measured the shear wave velocity of the landslide deposits by a surface wave technique called multichannel analysis of surface waves masw the results revealed that the landslide dams consisted of loosely deposited debris suggesting that the landslide dams were mechanically weak and prone to erosion by overtopping

fault scarp features and cascading rupture model for the mw 7 9 wenchuan earthquake eastern tibetan plateau china on 12 may 2008 the m w 7 9 wenchuan earthquake ruptured two northeast striking imbricated reverse faults and one northwest striking reverse fault along the middle longmen shan thrust belt at the eastern margin of the tibetan plateau the morphology of the coseismic scarp varies drastically along strike we distinguish eight different categories 1 simple thrust scarp 2 hanging wall collapse scarp 3 simple pressure ridge 4 dextral pressure ridge 5 fault related fold scarp 6 backthrust pressure ridge 7 local normal fault scarp and 8 pavement suprathrust scarp the coseismic surface ruptures confirm that the wenchuan earthquake is dominated by reverse faulting with some right lateral component that varies from site to site the surface rupture can be divided into two parts the yingxiu segment and the beichuan segment when the earthquake is split into two subevents accordingly they correspond to an m w 7 8 event and an m w 7 6 event respectively these two segments can in turn be divided into four second order subsegments which are equivalent to four subevents of m w 7 5 m w 7 7 m w 7 0 and m w 7 5 respectively the segmentation of the rupture is consistent with a cascading rupture pattern responsible for the total 110 s of the earthquake rupture in addition to surface ruptures the focal mechanisms determined for the aftershocks recorded by the local seismic network are used to constrain the fault geometry of the subsegments they show that the dip of the fault responsible for the earthquake varies along strike and the fault tends to flatten at depth in addition the fault plane gets steeper northward enabling the fault to accommodate a larger strike slip component along a lateral ramp this major earthquake confirms that crustal shortening could be the main driving force for the growth of high topography along the eastern margin of the tibetan plateau and that lower crustal flow is not required

preliminary analysis of some characteristics of coseismic landslides induced by the hokkaido iburi tobu earthquake september 5 2018 japan abstract at 18 07 on september 5 2018 utc a mw 6 6 earthquake struck the iburi tobu area of hokkaido japan the hokkaido iburi tobu hit earthquake is a reverse slip earthquake with a focal depth of 33 4 km at 42 69 n and 142 07 e according to the detailed landslide interpretations there were approximately 7059 landslides induced by this earthquake concentrated in an area of 466 km2 the landslides induced by the hit earthquake are mostly shallow landslides whose sources are mainly an air fall pumice layer from the tarumai volcano and these landslides exhibit an obvious characteristic of a low affected area large landslide area the landslide area follows an exponential distribution and many landslides are composed of multiple subsource areas there are at least 8778 source areas in the whole landslide area the landslides present high mobility and the landslide deposits not only accumulate on the foot but also flow down along the gullies similar to debris flows despite the gullies being gentle

microbial diversity in fracture and pore filling gas hydrate bearing sediments at site gmgs2 16 in the pearl river mouth basin the south china sea abstract gas hydrate systems are unique habitats for microorganisms in deep marine sediments and gas hydrate reservoirs can be divided into focused high flux and distributed low flux gas hydrate systems little is known about the microbial distribution patterns in these systems especially in the south china sea scs in this study a macroscopic fracture filling gas hydrate zone ghz and a microscopic pore filling ghz used as analogs to focused high flux gas hydrate systems and distributed low flux gas hydrate systems were sampled and microbial diversity was investigated at site gmgs2 16 in the northern scs during the gmgs2 gas hydrate expedition based on high throughput 16s rrna gene sequencing compared to previous studies of the gas hydrate bearing sites high microbial diversity was observed in the sulfate methane transition zone smtz at site gmgs2 16 and anme 1b a clade of anaerobic methanotrophic archaea anme may mainly perform anaerobic oxidation of methane aom in partnership with desulfarculaceae and desulfobacteraceae for the ghz fracture fill ghz and pore fill ghz and non ghz smtz and other other refers to the depth of 31 0 179 5mbsf the bacterial richness indices shannon and inverse simpson revealed higher diversity in the ghz than in the non ghz while the archaeal richness indices showed a contrary pattern non metric multidimensional scaling ordination revealed no significant differences in archaeal communities between the ghz and non ghz while differences between these zones were discovered in bacterial communities p

quantification of hanging wall effects on ground motion some insights from the 1999 chi chi earthquake accelerometric records of the chi chi earthquake from sites on the hanging wall exhibit larger acceleration than those from the footwall based on ground accelerations recorded at 79 near field stations 10 hanging wall stations and 69 footwall stations respectively and precise mapping of fault rupture traces the hanging wall footwall effects of the chi chi earthquake have been fully studied we show that the hanging wall effects cannot be simply accounted for by a proper choice of distance metric the closest distance to the rupture plane d rup is then selected to develop an empirical ground motion model by using the data collected during the mainshock of the chi chi earthquake that struck taiwan with the exception of some sites immediately next to the rupture traces d rup 5 km the acceleration residuals between this empirical model and the recorded data at the footwall stations are close to zero for stations in the distance range from 5 to 50 km on the other hand the average acceleration amplification on the hanging wall is equal to the natural logarithmic values of 0 64 0 4 for all hanging wall sites within 20 km of d rup the hanging wall footwall effects have also been evaluated for several response spectral periods it is observed that both the horizontal and vertical components of spectral acceleration are apparently amplified for sites on the hanging wall at a distance from 5 to 20 km for spectral periods 0 02 to 0 5 sec whereas the vertical component has less amplification than the horizontal in all the spectral periods considered the horizontal component of spectral acceleration at the hanging wall sites also shows a larger value for the long period motion relative to the footwall for periods larger than 1 0 sec the hanging wall effects are relatively constant at low frequencies as the distance extends to about 20 km this observation cannot be explained by the simplified empirical model rather it suggests that waves trapped in the hanging wall wedge may have been involved

the geological evolution of the tibetan plateau the geological evolution of the tibetan plateau is best viewed in a context broader than the india eurasia collision zone after collision about 50 million years ago crust was shortened in western and central tibet while large fragments of lithosphere moved from the collision zone toward areas of trench rollback in the western pacific and indonesia cessation of rapid pacific trench migration 15 to 20 million years ago coincided with a slowing of fragment extrusion beyond the plateau and probably contributed to the onset of rapid surface uplift and crustal thickening in eastern tibet the latter appear to result from rapid eastward flow of the deep crust probably within crustal channels imaged seismically beneath eastern tibet these events mark a transition to the modern structural system that currently accommodates deformation within tibet

landslides induced by the 2008 wenchuan earthquake sichuan china the 2008 wenchuan earthquake with a magnitude of mw 7 9 induced numerous slope movements on the hanging walls of fault surface ruptures and on steep inner valleys along the minjiang river landslide moving directions showed preferred orientations normal to the fault ruptures indicating the effect of the directivity of the seismic wave the most common landslides were of carbonate rocks which are easily dissolved and decrease the contact surfaces the largest non volcanic landslide in history was induced in bedded dolomite by the earthquake and was preceded by gravitational deformation with ridge top depressions valley fill materials were mobilized at 36 locations probably by pore water pressure build up

dynamic simulation of the 1999 chi chi taiwan earthquake 1 we apply a modified three dimensional finite difference method to investigate the dynamics of the 1999 chi chi earthquake we determine the dynamic source rupture process and simulate the strong ground motions over a frequency range of 0 05 0 5 hz our dynamic source model reveals that the rupture process of the chi chi earthquake is much more complex than that described in the classical propagation rupture models the chi chi earthquake rupture process includes the jumping phenomenon the northern parts on the fault plane have a longer slip duration than the southern parts the motions on the hanging wall are larger than those on the footwall side which is a consequence of the asymmetry of the fault with respect to the free surface in general the synthetics calculated by the dynamic source model agree well with the observed data our dynamic source model reproduces distinctive velocity pulses at stations located in the forward rupture direction and at stations close to the fault surface breaks the apparent rupture directivity propagating from south to north then produces noticeably larger peak ground velocity to the north these results demonstrate that the dynamic rupture model reproduces the main features of long period ground motions these results may lead to improved understanding of rupture processes accompanying large earthquakes the dynamic modeling scheme may produce more reasonable and reliable strong ground motion predictions for assessment of seismic hazard

source characteristics of long runout rock avalanches triggered by the 2008 wenchuan earthquake china the may 12 2008 wenchuan china earthquake which measured m w 8 3 according to chinese earthquake administration cea m w 7 9 according to the usgs directly triggered many landslides which caused about 20 000 deaths a quarter of the total rock avalanches were among the most destructive landslides triggered by this seismic event and have killed more people than any other type of landslide in this earthquake the donghekou rock avalanche one example of a catastrophic avalanche triggered by the wenchuan earthquake occurred in qingchuan and buried one primary school and 184 houses resulting in more than 780 deaths and in addition caused the formation of two landslide dams which formed barrier lakes combining aerial images resolution of 0 5 m with field investigations this paper lists some parameters of 66 cases in one table and details source characteristics of six typical cases it has been found that most of the long runout rock avalanches have source areas with high relief and steep inclination causing the debris in the travel courses to accelerate there was also a large amount of saturated holocene age loose deposits formed by a river or gully that existed in the travel courses comparison studies indicate that saturated holocene loose deposits in the travel courses could be the most important factor for the causes of the long runout characteristic of the rock avalanches especially when they traveled over gentle or even flat ground surfaces furthermore the relationships among the relief slope gradient runout and covered area are investigated and a threshold line for predicting the maximum horizontal runout distance under certain change in elevation is presented c 2010 elsevier ltd all rights reserved

the slip history of the 1994 northridge california earthquake determined from strong motion teleseismic gps and leveling data we present a rupture model of the northridge earthquake determined from the joint inversion of near source strong ground motion recordings p and sh teleseismic body waves global positioning system gps displacement vectors and permanent uplift measured along leveling lines the fault is defined to strike 122 and dip 40 to the south southwest the average rake vector is determined to be 101 and average slip is 1 3 m the peak slip reaches about 3 m our estimate of the seismic moment is 1 3 0 2 10 26 dyne cm potency of 0 4 km3 the rupture area is small relative to the overall aftershock dimensions and is approximately 15 km along strike nearly 20 km in the dip direction and there is no indication of slip shallower than about 5 to 6 km the up dip strong motion velocity waveforms are dominated by large s wave pulses attributed to source directivity and are comprised of at least 2 to 3 distinct arrivals a few seconds apart stations at southern azimuths indicate two main s wave arrivals separated longer in time about 4 to 5 sec these observations are best modeled with a complex distribution of subevents the initial s wave arrival comes from an asperity that begins at the hypocenter and extends up dip and to the north where a second larger subevent is centered about 12 km away the secondary s arrivals at southern azimuths are best fit with additional energy radiation from another high slip region at a depth of 19 km 8 km west of the hypocenter the resolving power of the individual data sets is examined by predicting the geodetic gps and leveling displacements with the dislocation model determined from the waveform data and vice versa and also by analyzing how well the teleseismic solution predicts the recorded strong motions the general features of the geodetic displacements are not well predicted from the model determined independently from the strong motion data likewise the slip model determined from geodetic data does not adequately reproduce the strong motion characteristics whereas a particularly smooth slip pattern is sufficient to satisfy the geodetic data the strong motion and teleseismic data require a more heterogeneous slip distribution in order to reproduce the velocity amplitudes and frequency content although the teleseismic model can adequately reproduce the overall amplitude and frequency content of the strong motion velocity recordings it does a poor job of predicting the geodetic data consequently a robust representation of the slip history and heterogeneity requires a combined analysis of these data sets

crustal thickening versus lateral expulsion in the indian asian continental collision since the beginning of the continental collision between india and asia there has been about 2500 km of convergence and the northward movement of india has been accommodated by major internal deformation of the asian lithosphere the crustal thickening in and around the tibetan plateau is clearly a direct consequence of this collision but there is considerable debate as to whether a large fraction of the indentation has been accommodated by eastward motion of the lithospheric blocks of southeastern asia and southern china numerical experiments described here test this hypothesis for a range of indentation geometries and rheological models of the lithosphere we employ a thin viscous sheet model of the lithosphere with a depth averaged nonlinear viscous rheology described by a stress strain rate exponent n and including gravitational buoyancy forces scaled by the dimensionless argand number ar the eastern boundary for the collision region is described as a lithostatic boundary the precollision normal stress is determined by static balance and that constant stress is applied throughout the collision the experiments show that during collision the eastern boundary is smoothly displaced to the east at a rate about 1 4 of the indentation rate with only minor variation due to geometry or rheology crustal thickening rates in the region of the plateau are reduced by between 10 and 25 of the corresponding rates determined for similar experiments with a rigid eastern boundary to generalize from the results of these experiments the total north south shortening strain produced by the collision is partitioned between crustal thickening and eastward displacement in the ratio of at least 3 1 and more probably 4 1

estimation of nonlinear soil behavior during the 1999 chi chi taiwan earthquake the 1999 chi chi taiwan earthquake mw 7 6 was one of the strongest earthquakes in recent years recorded by a large number of strong motion devices though only surface records are available the obtained strong motion database indicates the variety of ground responses in the near fault zones in this study accelerograms of the chi chi earthquake were simulated at rock and soil sites and models of soil behavior were constructed at seven soil sites tcu065 tcu072 tcu138 chy026 chy104 chy074 and chy015 for which parameters of the soil profiles are known down to depths of at least 70 m and at 24 other soil sites for which parameters of the soil profiles are known down to 30 40 m all the sites were located within 50 km from the fault for reconstructing stresses and strains in the soil layers we used a method similar to that developed for the estimation of soil behavior based on vertical array records as input for the soil layers acceleration time histories simulated by stochastic finite fault modelling with a prescribed slip distribution over the fault plane were taken in spite of the largeness of the earthquake s magnitude and the proximity of the studied soil sites to the fault plane the soil behavior at these sites was relatively simple i e a fairly good agreement between the spectra of the observed and simulated accelerograms and between their waveforms was obtained even in cases where a single stress strain relation was used to describe the behavior of whole soil thickness down to 70 80 m during strong motion obviously this is due to homogeneity in the characteristics of soil layers in depth at all the studied sites resonant phenomena in soil layers down to 40 60 m and nonlinearity of soil response were the main factors defining soil behavior at tcu065 tcu110 tcu115 chy101 chy036 and chy039 liquefaction phenomena occurred in the upper soil layers estimated strains achieved 0 6 0 8 at other stations maximum strains in the soil layers were as high as 0 1 0 4 according to our estimates thus valuable data on the in situ soil behavior during the chi chi earthquake was obtained similarity in the behavior of similar soils during the 1995 kobe 2000 tottori japan and chi chi taiwan earthquakes was found indicating the possibility of forecasting soil behavior in future earthquakes in the near fault zones of the three earthquakes hard type soil behavior and resonant phenomena in the upper surface layers prevail both leading to high acceleration amplitudes on the surface

comparing characteristics of rainfall and earthquake triggered landslides in the upper minjiang catchment china abstract the upper minjiang catchment is located at the eastern margin of the tibetan plateau and is frequently affected by landslides the two main triggering factors in the region are rainfall and high magnitude seismic shocks such as the 2008 wenchuan earthquake in this paper we present a comparison study of pre conditioning factors that drive the spatial occurrence of landslides in this high elevation region we used a multi temporal landslide inventory that differentiates between rainfall and earthquake triggers based on the analyses of satellite imagery aerial photos and field investigations our investigation revealed that the strongest influences on landslides are lithology and topographic factors the difference between these two triggering factors can also be observed with respect to the relative slope positions rainfall triggered landslides are more frequently found at lower slopes while seismic induced landslides are more evenly distributed on very steep slope sections in particular the steep and deeply incised river terraces in this region are prone to landslides due to their rapid formation this study presents the first analysis that differentiates two main triggering factors in order to understand the influence of rainfall and earthquakes on landslide occurrences in this region our results can also aid in the sustainable management of performance based slope engineering and landslide risk reduction by reporting the differences regarding the spatial distribution of rainfall and seismic triggered slope failures consequently these results can be used by local and regional decision makers for risk management and spatial planning

statistical analysis of an earthquake induced landslide distribution the 1989 loma prieta california event the 1989 loma prieta california earthquake moment magnitude m 6 9 generated landslides throughout an area of about 15 000 km2 in central california most of these landslides occurred in an area of about 2000 km2 in the mountainous terrain around the epicenter where they were mapped during field investigations immediately following the earthquake the distribution of these landslides is investigated statistically using regression and one way analysis of variance anova techniques to determine how the occurrence of landslides correlates with distance from the earthquake source slope steepness and rock type the landslide concentration defined as the number of landslide sources per unit area has a strong inverse correlation with distance from the earthquake source and a strong positive correlation with slope steepness the landslide concentration differs substantially among the various geologic units in the area the differences correlate to some degree with differences in lithology and degree of induration but this correlation is less clear suggesting a more complex relationship between landslide occurrence and rock properties

slope creep behavior observations and simulations rock slopes undergoing long term effects of weathering and gravity may gradually deform or creep downslope leading to geological structures such as bending bucking fracturing or even progressive failure this study uses geomechanics based numerical modeling to qualitatively explain the cause and evolution of slope creep behavior constitutive models used include the creep mohr coulomb and anisotropic models the last two models are used with the strength reduction in calculation first the results of field investigation around a landslide site occurring in slate are present the causes and modes of creep structures observed on slopes and underground are studied second the study investigates the influences of slope topography and anisotropy orientations on slope creep behavior finally progressive failure of slopes with different shapes is examined the simulated results show that the bending type of structures develops near slope surfaces and the buckling type of structures is associated with the deformation or slides of a slope the creep pattern varies with the orientation and position of an original planar structure the shear zone involves a joint or fracture along which displacement has taken place moreover creep behavior is more significant on slopes with greater height and inclination as well as on steeper portions whether on concave or convex slopes in addition with the same topographic conditions consequent slopes with coinciding cleavage and obsequent slopes with steep cleavage result in greater creep behavior without the effects of anisotropic cleavage concave and straight slopes develop failure surfaces from the crowns downwards whereas convex slopes develop failure surfaces from the toes upwards

inversion of strong ground motion and teleseismic waveform data for the fault rupture history of the 1979 imperial valley california earthquake a least squares point by point inversion of strong ground motion and teleseismic body waves is used to infer the fault rupture history of the 1979 imperial valley california earthquake the imperial fault is represented by a plane embedded in a half space where the elastic properties vary with depth the inversion yields both the spatial and temporal variations in dislocation on the fault plane for both right lateral strike slip and normal dip slip components of motion inversions are run for different fault dips and for both constant and variable rupture velocity models effects of different data sets are also investigated inversions are compared which use the strong ground motions alone the teleseismic body waves alone and simultaneously the strong ground motion and teleseismic records the inversions are stabilized by adding both smoothing and positivity constraints the moment is estimated to be 5 0 10 25 dyne cm and the fault dip 90 5 dislocation in the hypocentral region south of the united states mexican border is relatively small and almost dies out near the border dislocation then increases sharply north of the border to a maximum of about 2 m under interstate 8 dipslip motion is minor compared to strike slip motion and is concentrated in the sediments the best fitting constant rupture velocity is 80 per cent of the local shear wave velocity however there is a suggestion that the rupture front accelerated from the hypocenter northward the 1979 imperial valley earthquake can be characterized as a magnitude 5 earthquake at the hypocenter which then grew into or triggered a magnitude 6 earthquake north of the border

different landslide sampling strategies in a grid based bi variate statistical susceptibility model abstract this study had three aims the first was to assess the performance of the weights of evidence wofe landslide susceptibility model in areas that are very different in terms of size geoenvironmental settings and landslide types the second was to test the appropriate strategies to sample the mapped landslide polygon the final aim was to evaluate the performance of the method to changes in the landslide sample size used to train the model the method was applied to two areas the fella river basin eastern italian alps containing debris flows and buzau county romanian carpathians with shallow landslides the three landslide sampling strategies used were 1 the landslide scarp centroid 2 points populating the scarp on a 50 m grid and 3 the entire scarp polygon the highest success rates were obtained when sampling shallow landslides as 50 m grid points and debris flow scarps as polygons prediction rates were highest when using the entire scarp polygon method for both landslide types the sample size test using the landslide centroids showed that a sample of 104 debris flow scarps was sufficient to predict the remaining 941 debris flows in the fella river basin while 161 shallow landslides was the minimum required number to predict the remaining 1451 scarps in buzau county below these landslide sample thresholds model performance was too low however using more landslides than the threshold produced a plateau effect with little to no increase in the model performance rates

northridge earthquake rupture models based on the global positioning system measurements abstract we use global positioning system gps data to study the rupture mechanism of the 1994 northridge earthquake in southern california we include data from 62 observation sites of which two palos verdes and jet propulsion lab are permanent gps geodetic array pgga sites we use a grid search scheme to study the range of single and dual plane uniform and varied slip models consistent with the data we find that in order to fit the geodetic data with a fault model whose primary fault patch is confined to a plane through the aftershocks a secondary fault plane is required above the primary fault plane the moment release of the secondary fault can be as large as 1 9 10 18 n m 14 of the moment release of the primary fault this result implies significant deformation in the shallow crust associated with the mainshock our preferred model has a 14 14 array of dislocation patches on a plane through the main aftershock cluster and a 5 6 array of patches in the hanging wall west of the epicenter we estimate the displacements on the patches by linear inversion with a first order smoothness constraint the estimated displacements on the main fault for this model are confined to a simple region between depths of 5 and 18 km in the interior of the modeled fault surface the mainshock lies at the bottom of the aftershock zone near which about 1 m slip is shown on our modeled fault surface the maximum slip on the fault surface is about 2 2 m located at 34 28 n 118 55 w and 12 4 km at depth the seismic moment release estimate of 1 34 0 15 10 19 n m on the main fault at the 95 confidence is consistent with the estimate from strong motion studies

studying postseismic deformation of the 2010 2011 rigan earthquake sequence in se iran using geodetic data abstract in this paper we study the spatial distribution and temporal evolution of the postseismic deformation of the 2010 2011 rigan earthquake sequence which occurred at the southern termination of the east lut fault system southeast iran one year gps measurements after the rigan earthquake sequence reveals right lateral postseismic displacement along the east chahqanbar fault and left lateral postseismic displacement along the south chahqanbar fault to investigate the deformation variations in time and space insar time series of cosmo skymed images is applied using the small baseline subset algorithm the results confirm a clear cumulative postseismic signal increasing to 8 mm during the first five months following the first mainshock in the direction of the coseismic displacement the cumulative postseismic displacements are well correlated with the cumulative number of the aftershocks and their associated moment release considering this correlation and the observation of a sharp discontinuity along the coseismic fault in the displacement map it is concluded that the after slip mechanism is responsible for the observed postseismic deformation in the study region this study is the first observation of a short term postseismic motion in eastern iran through geodetic data in contrast with long lasting postseismic displacements following the earthquakes that occurred around lut block modeling of the postseismic displacement results in a distributed slip pattern with a maximum slip of 0 8 m on the fault plane responsible for the 2010 rigan coseismic deformation this indicates that the postseismic deformation on barriers remained unbroken during the mainshock

dda validation of the mobility of earthquake induced landslides abstract this paper studies the run out of earthquake induced landslides there are more than 20 mechanical models to explain long run out of rapid landslides including some earthquake induced landslides however notably few of them considered the effect of seismic loading on the run out of landslides in a previous study we have proposed a model which is called the multiplex acceleration model mam to interpret the long run out mechanism and a shaking table test has been performed to verify the mam because the previous mam is a conceptual model and only a single stone has been examined under sine waves by the shaking table test the mam needs to be extended and further verified in this paper the mam was extended by introducing the movement change that was induced by the so called trampoline effect of earthquake loading and the latest practical numerical simulation program discontinuous deformation analysis dda was used to verify the mobility of earthquake induced landslides after a conceptual landslide model was used to verify the effect of seismic loading on the mobility the donghekou landslide which was a typical long run out landslide that was induced by the 2008 wenchuan earthquake was analyzed the results show that the seismic loading could be one of the factors that could eventually help increase the run out of landslides

the november 17th 2015 lefkada greece strike slip earthquake field mapping of generated failures and assessment of macroseismic intensity esi 07 abstract on november 17 2015 a strong shallow earthquake mw 6 5 occurred on the island of lefkada along a n20 5 e east dipping strike slip fault with right lateral sense of slip the event triggered environmental effects that were mainly mapped at the western part of the island while moving towards the eastern part the severity of the earthquake induced failures decreased the most characteristic geological effects that were triggered by the earthquake were slope failures including rock falls rock slides and landslides the spatial density of the failures follows an exponential increase with slope angle and decreases for values larger than 55 small size liquefaction phenomena such as sand craters and ejection of fine grained sand through ground cracks were documented at the coastal area of vassiliki the epicentral intensity was assessed based on the definitions of environment seismic intensity scale as viii esi 07 and the macroseismic epicenter viii up to ix was located at the coastal area of egremnoi west of athani village south lefkada in addition comparing the severity of earthquake induced failures on the main road network triggered by the 2003 and 2015 events it is concluded that the behavior of the protection measures such as fences and walls could be generally characterized as satisfactory on the contrary the similarity of the structural failures triggered by the 2003 event with the ones triggered by the 2015 earthquake documented at the port of vassiliki indicates that the post 2003 constructed port facilities failed to guarantee the functionality of the port of vassiliki