quaternary transfer faulting in the taiwan foothills evidence from a multisource approach abstract the major structures of the western foothills of taiwan mainly consist of nne ssw trending folds and imbricated west vergent thrust systems the additional occurrence of n140 e striking oblique structures was revealed through a multisource approach involving a digital elevation model dem a study of drainage network anomalies aerial photographs side looking airborne radar slar images and spot p and landsat images these structures are described from north to south based on new field analyses including stratigraphy and tectonics studies they are also compared to seismic data and geodetic reconstruction in order to evaluate their present day activity these n140 e major morphostructures are interpreted as left lateral transfer fault zones either inherited from the eurasian passive margin and or newly formed in the cover in response to the presence of basement highs within the foreland basin peikang and kuanyin highs the sanyi and the chishan transfer fault zones display a high seismic activity the distribution of earthquakes and the related focal mechanisms confirm the left lateral movement along n140 e directions the chiayi chishan and fengshan fault zones act presently as transfer fault zones as indicated by gps data the associated n70 e to n100 e trending faults result from the reactivation of normal faults of the eurasian passive margin as right lateral strike slip faults in the foothills during the plio quaternary collision in taiwan we conclude that multisource and multiscale geomorphic studies combined with tectonic analysis in the field yield a significant contribution to the understanding of the structural and kinematic development of the western foothills at the front of the taiwan collision belt

vegetation history in western uganda during the last 1200 years a sedimentbased reconstruction from two crater lakes pollen plant macrofossil and charcoal records from two neighbouring crater lakes lake wandakara and lake kasenda in lower montane altitude 1200m western uganda 0 5dn 30 reveal major changes in local and regional vegetation over the last 1200 years which can be related to regional variations in climate especially effective precipitation and human impact the biological signals are supplemented by evidence from physical sedimentary analyses magnetic susceptibility loss on ignition dry mass accumulation rate for major catchment changes in a wider regional context from ad 750 to 900 medium altitude moist forest existed around lake kasenda which was largely replaced by grassland by ad 1000 coincident e with evidence for increased catchment erosion and fire events linked to human impact during a brief arid phase despite wetter conditions from ad 1000 to 1200 and in the 1400s grassland prevailed around both sites until c ad 1700 1750 with increased catchment disturbance from ad 1600 t

formation and widening of a north sea tunnel valley the impact of slope processes on valley morphology abstract over the past two decades seismic data from the hydrocarbon industry have become a popular tool for investigating shallow quaternary formations in the north sea basin revealing multiple buried tunnel valleys and other features of glacial origin in this study we incorporate 3d seismic analysis with 2d high resolution seismic data to describe a tunnel valley system in the southern part of the danish north sea basin we document pervasive slumping as the main driver for valley widening in the southern part of the system the slumping and the lateral distribution of slump scars were seemingly controlled by valley steepness and the shape of the valley profile which is partly controlled by the infill rate the system evolved through multiple erosional and depositional phases in the subglacial environment with continued deposition after deglaciation the study provides further evidence of large scale channelized subglacial drainage under past ice sheets and documents a strong impact of valley slope processes in the shaping of the morphology of the upper slopes and shoulders of tunnel valleys

revealing coseismic displacement and displacement partitioning at the northern end of the 1999 chi chi earthquake central taiwan using digital cadastral data abstract the 1999 chi chi taiwan earthquake m w 7 6 was the largest earthquake to strike taiwan in the twentieth century its surface rupture extends more than 100 km in a north south trend however the northern end of this surface deformation abruptly terminates at an area between the tachia river and the taan river where a broad pop up structure with east to northeast strike quite different from the north south striking main thrust is found this pop up structure is composed of several regions of parallel thrusts and back thrusts and total shortening reaches about 9 m in order to reveal the displacement field in the pop up structure and slip vectors of branch faults we use a digital cadastral system with about 17 000 control points to calculate coseismic displacement around the shihkang area the digital cadastral system was originally conceived to survey land and building boundaries the cadastral system affords high density control points that reach about 2800 points km 2 and the accuracy is to within 11 cm outside of the pop up structure the horizontal displacements vectors are 8 9 m in about 330 340 changing as they pass through the surface rupture the azimuth of horizontal displacement shows large variation with the azimuth from 360 to 315 and displacement amounts from about 4 8 m inside the pop up structure in addition according to these cadastral data we found surface ruptures that had not been observed in previous studies that could be of importance to future disaster assessment

the chi chi earthquake sequence active out of sequence thrust faulting in taiwan we combined precise focal depths and fault plane solutions of more than 40 events from the 20 september 1999 chi chi earthquake sequence with a synthesis of subsurface geology to show that the dominant structure for generating earthquakes in central taiwan is a moderately dipping 20 to 30 thrust fault away from the deformation front a second subparallel seismic zone lies about 15 kilometers below the main thrust these seismic zones differ from previous models indicating that both the basal decollement and relic normal faults are aseismic

radar interferometry and its application to changes in the earth s surface geophysical applications of radar interferometry to measure changes in the earth s surface have exploded in the early 1990s this new geodetic technique calculates the interference pattern caused by the difference in phase between two images acquired by a spaceborne synthetic aperture radar at two distinct times the resulting interferogram is a contour map of the change in distance between the ground and the radar instrument these maps provide an unsurpassed spatial sampling density 100 pixels km 2 a competitive precision 1 cm and a useful observation cadence 1 pass month 1 they record movements in the crust perturbations in the atmosphere dielectric modifications in the soil and relief in the topography they are also sensitive to technical effects such as relative variations in the radar s trajectory or variations in its frequency standard we describe how all these phenomena contribute to an interferogram then a practical summary explains the techniques for calculating and manipulating interferograms from various radar instruments including the four satellites currently in orbit ers 1 ers 2 jers 1 and radarsat the next chapter suggests some guidelines for interpreting an interferogram as a geophysical measurement respecting the limits of the technique assessing its uncertainty recognizing artifacts and discriminating different types of signal we then review the geophysical applications published to date most of which study deformation related to earthquakes volcanoes and glaciers using ers 1 data we also show examples of monitoring natural hazards and environmental alterations related to landslides subsidence and agriculture in addition we consider subtler geophysical signals such as postseismic relaxation tidal loading of coastal areas and interseismic strain accumulation we conclude with our perspectives on the future of radar interferometry the objective of the review is for the reader to develop the physical understanding necessary to calculate an interferogram and the geophysical intuition necessary to interpret it

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

deformation during the 12 november 1999 duzce turkey earthquake from gps and insar data only 87 days after the mw 7 5 17 august 1999 izmit earthquake the duzce earthquake ruptured a ca 40 km long adjoining strand of the north anatolian fault naf system to the east we used displacements of 50 global positioning system gps sites together with interferometric synthetic aperture radar insar range change data spanning the event to estimate the geometry and slip distribution of the coseismic rupture postseismic deformation transients from the duzce earth quake and the preceding i zmit event that are included in some of the measurements are corrected for using dislocation models fit to gps data spanning the various time periods nonlinear inversions for fault geometry indicate that the rupture occurred on a ca 54 north dipping oblique normal right lateral fault distributed slip inver sions indicate maximum strike slip near the center of the duzce fault close to the earthquake hypocenter slip magnitude and depth of faulting decrease to the west and east of the hypocenter both gps and insar data suggest that normal slip is restricted to the shallow portion of the rupture the duzce earthquake had the highest slip to rupture length ratio of any historic earthquake along the naf

surface rupture of 1999 chi chi earthquake yields insights on active tectonics of central taiwan the 1999 chi chi earthquake was caused by rupture of the chelungpu fault one of the most prominent active thrust faults of taiwan this largest of taiwan s historical fault ruptures broke the surface for over 90 km at the western base of the rugged mountain range a short right lateral tear extended southwestward from the southern end of the chelungpu fault and a complex assemblage of shallow folds and faults ran northeastward from the northern end vertical offsets averaged about 2 m along the southern half of the chelungpu fault and about 4 m along the northern half and offsets of 5 to 7 m were typical along the northern part of the major thrust the sinuous nature of the surface trace is consistent with seismographic data that indicate a dip of about 30 the 1999 rupture draws attention to the fact that this active fault system is highly segmented and that this segmentation influences the characteristics of seismic ruptures active faults to the south north and west of the chelungpu fault have distinctly different characteristics faults to the south and north broke the surface during earthquakes in 1906 and 1935 the active changhua fault to the west a blind thrust similar in length to the chelungpu has not ruptured in the historical period and should be considered a prime candidate for generating a future earthquake manuscript received 4 october 2000

a vertical exposure of the 1999 surface rupture of the chelungpu fault at wufeng western taiwan structural and paleoseismic implications for an active thrust fault we mapped and analyzed two vertical exposures exposed on the walls of a 3 to 5 m deep 70 m long excavation and a smaller 3 m deep 10 m long excavation across the 1999 rupture of the chelungpu fault the primary exposure revealed a broad anticlinal fold with a 2 5 m high west facing principal thrust scarp contained in fluvial cobbly gravel beds and overlying fine grained overbank deposits sequential restoration of the principal rupture requires initial failure on the basal east dipping thrust plane followed by wedge thrusting and pop up of an overlying symmetrical anticline between two opposing secondary thrust faults net vertical offset is about 2 2 m across the principal fault zone from line length changes we estimate about 3 3 m of horizontal shortening normal to fault strike the ratio of these values yields a total slip of 4 0 m and an estimate of about 34 for the dip of the fault plane below the excavation this value is nearly the same as the 35 average dip of the fault plane from the surface to the hypocenter restoration of the exposed gravelly strata and adjacent overbank sediments deposited prior to the 1999 event around the principal rupture suggests the possible existence of a prior event a buried 30 m wide anticlinal warp beneath the uplifted crest of the 1999 event is associated with three buried reverse faults that we interpret as evidence for an earlier episode of folding and faulting in the site the prior event is also recorded in the smaller excavation which is located 40 m south and is oriented parallel to the larger excavation radiocarbon dating of samples within the exposed section did not place tight constraints on the date of the previous event available data are interpreted as indicating that the previous event occurred before the deposition of the less than 200 14 c yr b p overbank sands and after the deposition of the much older fluvial gravels we interpret the previous event as the penultimate event relative to the 1999 chi chi earthquake we estimated the long term slip rate of the chelungpu fault to be 10 15 mm yr during the last 1 ma based on previously published retrodeformable cross sections this rate is however significantly higher than geodetic rates of shortening across the chelungpu thrust where two pairs of permanent global positioning system stations suggest 7 10 mm yr of shortening across the fault given the 4 m of average slip the long term slip rate yields an interseismic interval of between 267 and 400 yr for the chelungpu fault

synthetic aperture radar interferometry to measure earth s surface topography and its deformation synthetic aperture radar interferometry insar from earth orbiting spacecraft provides a new tool to map global topography and deformation of the earth s surface radar images taken from slightly different viewing directions allow the construction of digital elevation models of meter scale accuracy these data sets aid in the analysis and interpretation of tectonic and volcanic landscapes if the earth s surface deformed between two radar image acquisitions a map of the surface dis placement with tens of meters resolution and subcentimeter accuracy can be con structed this review gives a basic overview of insar for earth scientists and presents a selection of geologic applications that demonstrate the unique capabilities of insar for mapping the topography and deformation of the earth

a synthesis of the geologic evolution of taiwan abstract the island arc of taiwan is composed of cenozoic geosynclinal sediments more than 10 000 m thick lying on a pre tertiary metamorphic basement pleistocene to miocene andesitic islands surround the main island and are related mostly to arc magmatism the penghu island group in the taiwan strait is covered with pleistocene flood basalt neogene shallow marine clastic sediments are exposed mainly in the western foothills with pleistocene andesitic extrusives at the northern tip and the northeastern offshore islands a thick sequence of paleogene to miocene argillitic to slaty metaclastic rocks underlies the western central range and forms the immediate sedimentary cover on the pre tertiary metamorphic complex to the east which represents an older mesozoic arc trench system the coastal range in eastern taiwan is a neogene andesitic magmatic arc including also a large variety of volcaniclastic and turbiditic sediments cenozoic taiwan is the site of arc continent collision where the luzon arc on the philippine sea plate overrides the chinese continental margin on the eurasian plate east and northeast of taiwan the polarity of subduction changes whereby the oceanic philippine sea plate is subducting beneath the ryukyu arc system on the eurasian plate continent arc collision in taiwan island is anomalous and may occur in a broad belt of deformation rather than along a well defined plate boundary or subduction zone

active deformation of tainan tableland of southwestern taiwan based on geodetic measurements and sar interferometry the d insar technique is applied to detect the active fault related folding structure of the tainan tableland near the deformation front in sw taiwan by using ers sar images during 1996 2000 the tainan tableland is located in between a blind fault in the west and the houchiali fault in the east thus the tainan tableland is interpreted as a pop up structure in a fold thrust belt at active tectonic margin interferometric processing of six sar images reveals the average slant range deformation srd as 12 5 mm yr the uplift rate is higher in eastern tainan tableland than that in western tainan tableland and it increases from west edge of tainan tableland and decreases across the houchiali fault the campaign mode gps data set from 1999 to 2003 indicate an average horizontal movement of 12 4 mm yr in the direction of n44 w for the tainan tableland with respect to western coastline furthermore 5 precise leveling surveys across tainan tableland over a period of 2 years show an uplift rate of 14 mm yr for the benchmarks on the tableland based on the 2 d analytical solution with the constraint of he inferred fault geometry the slip rate along the inferred tainan fault is 16 mm yr 10 mm yr along the houchiali fault and 25 mm yr along the inferred chungchou fault consequently we propose that active deformation of the tainan tableland is likely resulted from the freely slipping of the tainan fault and the houchiali fault the locking depth should be located on the deeper part of decollement eastern of the chungchou fault in addition the combination of d insar gps data and the precise leveling data reveals that the short term deformation rate is larger than long term deformation rate which implies that a destructive seismic event could occur in the eastern tainan area

surface deformation from persistent scatterers sar interferometry and fusion with leveling data a case study over the choushui river alluvial fan taiwan abstract the choushui river alluvial fan craf one of the most important agricultural areas in taiwan suffers severe subsidence caused by groundwater withdrawal we use 20 envisat images from 2006 to 2008 to derive vertical deformation over craf by persistent scatterer interferometry psi which effectively reduces errors affecting conventional dinsar techniques the pixel density over craf is 107 6 pixels km 2 compared to 0 19 points km 2 of the leveling benchmarks psi yields vertical displacements matching the leveling result to 0 6 cm year rms and provides a higher spatial resolution of subsidence than the latter we also develop a data fusion method that considers the high precision low point density leveling result as a smoothed correction to the psi result the combined field is more representative of overall deformation characteristics than the psi only or leveling only field and it is better suited for the assessment of the impact of subsidence over craf

fifteen years of surface deformation in western taiwan insight from sar interferometry abstract geodetically measured surface displacements are produced by a combination of underlying deformation processes acting at different spatial and temporal scales a complete history of surface measurements in an area can help discriminate contributions from tectonic hydrologic and anthropogenic processes in this study we use synthetic aperture radar sar images of the active mountain front and adjacent coastal plain of southwestern taiwan to generate time series of surface deformation from 1995 to 2001 and from 2005 to 2008 based on the insar small baseline method the insar measurements agree well with los motions estimated from continuous gps measurements of 3d displacements between 2006 and 2008 a significant range increase in line of sight los is dominated by land subsidence in the coastal area of western and southwestern taiwan subsidence rates vary with annual periods and are highly correlated with seasonal precipitation which are likely associated with groundwater recharge and withdrawal the long term deformation is dominated by long term tectonic loading in sw taiwan during the interseismic period of the earthquake cycle including elastic strain along or continuous creep on the active faults our results show the ability of insar to reveal spatiotemporal crustal deformation in western taiwan with high spatial resolution and accuracy which is potentially important for evaluating seismic hazards

satellite interferometric observations of displacements associated with seasonal groundwater in the los angeles basin 1 the newport inglewood fault zone nifz displays interferometric synthetic aperture radar sar phase features along most of its length having amplitudes of up to 60 mm however interpretation in terms of right lateral shallow slip along the fault fails to match the range of geologic estimates of slip recently bawden et al 2001 proposed that these phase features as well as a broader deformation pattern in the los angeles basin are due to vertical motion related to annual variations in the elevation of the water table we confirm this hypothesis through the analysis of a longer span of data consisting of 26 sar images collected by the ers 1 and ers 2 spacecraft between june 1992 and june 2000 moreover we use continuous gps measurements from 1995 to the present to establish the amplitude and phase of the vertical deformation the los angeles basin becomes most inflated one quarter of the way through the year which is consistent with water table measurements as well as with the end of the rainy season when the aquifer should be at a maximum the spatial pattern of the amplitude of the annual signal derived from continuous gps measurements is consistent with the shape of the interferometric fringes gps sites both near the nifz and in a 20 by 40 km zone within the basin also show significant n s annual variations that may be related to the differential expansion across the fault since these horizontal signals have peak to trough amplitudes of 6 mm they mask the smaller tectonic signals and need to be taken into account when interpreting gps time series of site position moreover since the groundwater signal appears to have a long term vertical trend which varies in sign depending on location it will be difficult to distinguish interseismic tectonic slip along the nifz and within the affected areas in the basin

estimating slip distribution for the izmit mainshock from coseismic gps ers 1 radarsat and spot measurements we use four geodetic satellite systems global positioning system gps european remote sensing ers radarsat and satellite pour l9observation de la terre spot to measure the permanent deformation field produced by the izmit earthquake of 17 august 1999 we emphasize measurements from interferometric analysis of synthetic aperture radar sar images acquired by ers and radarsat and their geodetic uncertainties the primary seismological use of these data is to determine earthquake source parameters such as the distribution of slip and the fault geometry after accounting for one month9s postseismic deformation tropospheric delay and orbital gradients we use these data to estimate the distribution of slip at the time of the izmit mainshock the different data sets resolve different aspects of the distribution of slip at depth although these estimates agree to first order with those derived from surface faulting teleseismic recordings and strong motion careful comparison reveals differences of 40 in seismic moment we assume smooth parameterization for the fault geometry and a standard elastic dislocation model the root mean square residual scatter is 25 mm and 11 mm for the ers and radarsat range changes respectively our estimate of the moment from a joint inversion of the four geodetic data sets is m 0 1 84 10 20 n m a moment magnitude of m w 7 50 these values are lower than other estimates using more realistic layered earth models given the differences between the various models we conclude that the real errors in the estimated slip distributions are at the level of 1 m the prudent geophysical conclusion is that coseismic slip during the izmit earthquake tapers gradually from approximately 2 m under the hersek delta to 1 m at a point 10 km west of it we infer that the yalova segment west of the hersek delta may remain capable of significant slip in a future earthquake

combined gps and insar models of postseismic deformation from the northridge earthquake models of combined global positioning system gps and interferometric synthetic aperture radar insar data collected in the region of the northridge earthquake indicate that significant afterslip on the main fault occurred following the earthquake additional shallow deformation occurred to the west of the main rupture plane both data sets are consistent with logarithmic time dependent behavior following the earthquake indicative of afterslip rather than postseismic relaxation aftershocks account for only about 10 of the postseismic motion the two data sets are complimentary in determining the postseismic processes fault afterslip and shallow deformation dominate the deformation field in the two years following the earthquake lower crustal deformation may play an important role later in the earthquake cycle

on the derivation of coseismic displacement fields using differential radar interferometry the landers earthquake we present a map of the coseismic displacement field resulting from the landers california june 28 1992 earthquake derived using data acquired from an orbiting high resolution radar system we achieve results more accurate than previous space studies and similar in accuracy to those obtained by conventional field survey techniques data from the ers 1 synthetic aperture radar instrument acquired in april july and august 1992 are used to generate a high resolution wide area map of the displacements the data represent the motion in the direction of the radar line of sight to centimeter level precision of each 30 m resolution element in a 113 km by 90 km image our coseismic displacement contour map gives a lobed pattern consistent with theoretical models of the displacement field from the earthquake fine structure observed as displacement tiling in regions several kilometers from the fault appears to be the result of local surface fracturing comparison of these data with global positioning system and electronic distance measurement survey data yield a correlation of 0 96 thus the radar measurements are a means to extend the point measurements acquired by traditional techniques to an area map format the technique we use is 1 more automatic 2 more precise and 3 better validated than previous similar applications of differential radar interferometry since we require only remotely sensed satellite data with no additional requirements for ancillary information the technique is well suited for global seismic monitoring and analysis

revealing coseismic displacements and the deformation zones of the 1999 chi chi earthquake in the tsaotung area central taiwan using digital cadastral data 1 the 1999 chi chi taiwan earthquake mw 7 6 was the largest earthquake to strike taiwan in the twentieth century this earthquake is associated with a 100 km long surface rupture in order to reveal the details of displacement near the surface rupture we use a digital cadastral system to calculate coseismic displacement around the tsaotung area central taiwan the digital cadastral system was originally conceived to survey land and building boundaries in the tsaotung area taiwan authorities have taken digital cadastral measurements before and after the chi chi earthquake the cadastral system affords high density control points that reach 1421 points km2 a system denser than that of the gps accuracy is to within 11 cm a level that is higher than spot imaging and one that allows us to study surface deformation in detail coseismic displacement is 4 3 4 6 m at distance from the surface rupture and decreases to 3 4 m near the surface rupture the azimuth of horizontal displacements is 310 315 and rotates to 280 305 near the surface rupture this produced a compression left lateral deformation zone with 10 3 compression strain near the surface rupture coseismic displacement of the footwall is 1 1 2 m in 110 which is similar to that from using gps data in the tsaotung thrust slice we observed that the azimuth of horizontal displacement rotates from a nw trend to a south trend as a result of slip partitioning and gravity slide effect

joint inversion of insar gps teleseismic and strong motion data for the spatial and temporal distribution of earthquake slip application to the 1999 izmit mainshock the space time distribution of slip of the 17 august 1999 izmit earthquake is investigated by inverting synthetic aperture radar sar interferometry and global positioning system gps data together with teleseismic broadband and near field strong motion records surface offsets are used as an added constraint special emphasis is given to analysis of the resolution of the different data sets we use a four segment finite fault model and a nonlinear inversion scheme allowing slip to vary in amplitude direction and duration as well as variable rupture velocity from the inversion of synthetic data we find that the best spatial resolution can be expected in the upper half of the fault model above 12 km where coverage of the interferometric sar data is good western half of the rupture and near the gps and strong motion stations teleseismic data are found to have a lower resolution that is more evenly distributed over the fault model the joint inversion of all the data sets has an increased resolving power compared with the separate inversions and gives a more robust description of the space and time distribution of slip our study shows the importance of resolution tests in evaluating the reliability of earthquake kinematic models and it confirms that an excellent fit of a single kind of data does not necessarily imply a good retrieval of the kinematic properties of an earthquake the izmit rupture which is almost pure right lateral strike slip faulting is dominated by the bilateral breaking of a central asperity located between 29 7 e about 10 km west of the city of golcuk and 30 4 e eastern margin of sapanka lake with slip reaching 6 8 m in the depth range 6 12 km the western termination of the rupture is found near the city of yalova but large slip ends around 29 7 e about 10 km east of hersek delta a second area of large slip is required by all the data sets further east toward the city of duzce between 30 7 e and 31 1 e karadere and duzce faults this eastern slip zone which is separated from the main central asperity by an area of greatly reduced slip is less well constrained by the data however a strong motion station near the city of duzce helps to locate a high slip patch near 31 1 e in the depth range 6 12 km the total seismic moment resulting from the joint inversion is 2 4 1027 dyne cm most of the energy release occurred in a short time less than 15 sec corresponding to the bilateral breaking of the central asperity rupture propagation is relatively uniform and fast toward the west with a rupture velocity close to 3 5 km sec propagation of large slip toward the east is initially slower but it accelerates during a short time interval about 10 sec after rupture nucleation eastward progression then slows down to less than 2 km sec after 15 sec and rupture almost vanishes in amplitude ca 20 sec after initiation rupture propagation then proceeds on the easternmost karadere and duzce fault segments east of 30 7 e from 22 to ca 50 sec supershear rupture propagation is not required for modeling the waveforms considered in this study the hypocenter of the duzce earthquake which occurred 3 months later 12 november 1999 m w 7 2 is located in the immediate vicinity of the easternmost slip patch of the izmit earthquake manuscript received 28 july 2000

application of sar interferometry to a large thrust deformation the 1999 mw 7 6 chichi earthquake in central taiwan summary application of the interferometric method to four ers2 sar images acquired before and after the 1999 chichi earthquake has allowed determination of the coseismic surface displacement in the footwall area of the chelungpu fault the interferometric results revealed a relative shortening in the round trip distance between the radar antenna and the ground of the footwall side of chelungpu fault during the earthquake this shortening progressively increased from the west to the east and reaches the maximum amount of approximately 26 cm near the central segment of the chelungpu fault our interferometric results have been precisely examined using a dense gps network in the investigated area we mapped the gps coseismic measurements into the radar line of sight and implemented a forward simulation of sar interferogram from this synthesized result to control our unwrapping performance in this study these two observations are compared with a 3 d dislocation model of the fault finally a deformation analysis based on our interferometric result has indicated that a segment with irregular deformation behaviour can be distinguished in the footwall area of the chelungpu fault this segment may result from either the influence of inherited basement faults or the presence of a structural terrace that provide local opportunities for superficial deformation

spatial slip distribution of the september 20 1999 chi chi taiwan earthquake mw7 6 inverted from teleseismic data the teleseismic waveforms of the mw7 6 september 20 1999 chi chi earthquake were examined to obtain the quick information on the fault rupture process the deconvolution results show the fault ruptured from south to the north and revealed the west movement of the hanging wall to the footwall on the eastern dipping plane the spatial slip distribution shows that the earthquake was mainly composed by a large asperity with a dimension of about 45km 15km the maximum slip was about 8 m located at about 45 km to the north of the epicenter the slip distributions obtained in this study have a good agreement with the observed surface breaks the comparable static and the dynamic stress drops of about 11 mpa in the large slip region indicate that the melting fluid pressurization might have taken place in this earthquake it reduces the dynamic friction and results in the large slip observed

present day surface deformation and tectonic insights of the extensional ilan plain ne taiwan abstract taiwan s mountain belt is an ideal location to address major questions regarding mechanisms of lithospheric deformation in convergent settings mountain building processes from oceanic subduction to continental subduction and post orogenic extension in the northeast of this belt the ilan plain is a triangular deltaic plain characterized by a flat topography close to the sea level and surrounded by the high mountains of the hsuehshan range to the northwest and the central range to the southeast its eastern coast faces the western tip of the okinawa trough the back arc basin of the ryukyu subduction zone in this study we analyzed the present day surface deformation of the ilan plain aiming at deciphering its relationships with basement faults and the regional geodynamic setting our approach is mainly based on surface vertical displacements revealed by persistent scatterer interferometry synthetic aperture radar psi which indicate that there is an area of active subsidence 18 mm yr located in the southern part of the plain in probable connection with active basement faults and in agreement with previous geodetic measurements and existing geophysical data our psi results also suggest that the subsidence occurring in the ilan plain has moved from north to south during quaternary in relation with extrusion of the belt due to the westward propagation of the okinawa trough through the taiwan mountains

co seismic displacements of the 1992 landers earthquake sequence we present co seismic displacement vectors derived from global positioning system gps measurements of 92 stations in southern california these gps results are combined with five well determined gps displacement vectors from continuously tracking stations of the permanent gps geodetic array as well as line length changes from usgs geodolite and two color laser trilateration observations to determine a self consistent set of geodetic data for the earthquake these combined displacements are modeled by an elastic dislocation representation of the primary fault rupture planes on average the model residuals are about twice the estimated measurement errors

the 1996 mw 6 6 lijiang earthquake application of jers 1 sar interferometry on a typical normal faulting event in the northwestern yunnan rift zone sw china abstract the northwestern yunnan rift zone in the yunnan province of china is a seismically active region located along the western boundary of the sichuan yunnan block on the eastern margin of the qinghai tibetan plateau an earthquake with a magnitude of 6 6 mw occurred in this region on february 3 1996 the lijiang earthquake was the largest normal faulting event to occur along the western boundary of the sichuan yunnan block in the last 40 years in this study we used l band jers 1 japanese earth resources satellite 1 sar data sets from two descending orbits to detect surface deformation signals surrounding the epicentral region in order to estimate the source parameters through an inversion of the displacement fields the results indicated that the earthquake can be explained by slip along two segments of the n s trending listric normal fault named the lijiang daju fault coseismic deformation patterns and slip distributions revealed that the earthquake consisted of two sub events which were also suggested by seismological results based on an analysis of the static coulomb stress change the second sub event was likely triggered by the first sub event the central segment of the lijiang daju fault which has an eastward convex geometry did not rupture during the earthquake this phenomenon was probably related to a geometrical discontinuity at the fault bend area of the lijiang daju fault

source parameters of the 1 october 1995 dinar turkey earthquake from sar interferometry and seismic bodywave modelling abstract the 1 october 1995 m s 6 1 dinar earthquake ruptured a 10 km section of the nw se dinar civril fault there are discrepancies between the published source parameters from seismic data with seismic moments in disagreement by over a factor of two we use both sar interferometry and seismic bodywave modelling to determine earthquake source parameters an interferogram generated from ers 1 2 sar imagery spanning the event and separated by 5 months is used to derive source parameters by a downhill simplex inversion with multiple monte carlo restarts we model the displacements in the satellite line of sight initially using uniform slip on a rectangular dislocation in an elastic half space the resultant model fault plane agrees in strike and location with the observed surface break but systematic residuals exist in the line of sight deformation field resulting in a r m s residual of 20 mm in the interferogram the residuals are reduced if the depth distribution of slip is allowed to vary spatially in four segments along a continuous fault plane our best fitting solution with a r m s misfit of 8 mm reveals two distinct areas of slip on the fault plane strike 145 dip 49 rake 270 a main rupture slipping by 1 44 m between depths of 1 and 8 km becoming deeper to the se and matching the observed surface rupture and an along strike continuation to the nw of the same fault plane but between depths of 8 and 13 km and not associated with a surface break the total geodetic moment 4 5 0 1 10 18 nm is more than twice as large as published seismic moments based on the inversion of p waveforms alone but close to the harvard cmt moment 4 7 10 18 nm we use sh waveforms in addition to the p waves used previously to determine an alternative seismic source mechanism sh waves constrain the depth to be shallower than solutions based on p waves alone agreeing with the depths from the interferometric inversion and resulting in a larger moment 3 1 0 4 10 18 nm than the previous bodywave estimates 2 2 1 10 18 nm the cmt moment reduces in magnitude to a similar size 3 3 10 18 nm if the centroid depth and fault dip are constrained to the values determined from bodywave modelling and interferometry thus the geodetic moment is 40 bigger than the moment determined from seismology

preseismic deformation and coseismic displacements associated with the 1999 chi chi taiwan earthquake the destructive 1999 chi chi taiwan earthquake m w 7 5 produced an approximately 100 km long surface rupture mostly along the previously recognized north south trending chelungpu fault preseismic deformation in central taiwan is realized from annually repeated global positioning system gps data acquired during the 1992 1999 period the total wnw ese shortening rate in the vicinity of the epicentral region that is from the west coast to the western boundary of the central range is up to 25 mm yr the crustal deformation before the chi chi earthquake was essentially a uniaxial compressional strain of 0 36 strain yr in the direction of 114 the gps measurements taken 0 2 2 7 yr before and within 3 months after the mainshock were utilized to estimate the coseismic displacements horizontal movements of 1 1 9 1 m in the nw nnw directions are observed on the hanging wall eastern side of the fault there is a northward increasing trend in the magnitude of the displacement vectors and a dramatic change in the direction of about 50 toward the east along the fault strike in contrast much smaller se see movements of 0 1 1 5 m are found on the footwall western side of the fault the gps data show 2 4 10 1 m of total horizontal offsets across the chelungpu fault vertical offsets of 1 2 4 4 m with the eastern side up are also observed along the surface rupture the uplift on the hanging wall decreases rapidly toward the east it becomes subsidence at sun moon lake and in the puli wushe area the stations on the footwall show subsidence of 0 02 0 26 m the width of the uplift zone increases from about 10 km in the south to approximately 30 km in the north manuscript received 13 october 2000

landscape evolution and deduction of surface deformation in the soan dun nw himalaya india abstract the consequence of strain accumulation along various himalayan thrusts is manifested in shaping the topography and present day lanscape features of the himalaya consequently the strain accomodation is attributed to the occurrence of various devastating earthquakes in the himalayan domain including 1905 kangra earthquake mw 7 8 which occurred along the kangra valley fault in the present study we analyzed and estimatedsss fault related parameters gradient length anomaly gla analysis together with interferometric synthetic aperture radar in sar measurements to understand the landscape evolution and deformation pattern within the soan dun piggy back basin in the northwest himalayan front we combined the results of geodetic geological geomorphology and insar to constrain the uplift and subsidence between himalayan frontal thrust hft and main boundary thrust mbt zones the estimated results of fault parameters reveal that the horizontal shortening of northwest himalaya is higher than the vertical uplift the computed values of gla magnitude analysis for the uplifted region vary from 9 21 to 0 77 whereas these range from 5 48 to 26 60 for the subsided region the depicted range of vertical deformation observed from the insar measurements ranges from 3 13 to 3 14 mm y where the positive and negative value of phases are correlated with the ground uplift and subsidence the rate of deformation observed from persistent scatterer interferometry psi phase velocity and gla magnitude is positively supported by the chronologically constrained uplift rates as 3 4 0 3 mm y the geomorphic evidences such as folded tilted and truncated alluvial fan surfaces offsetting of channels fault scarps and displaced sedimentary sequences indicate active nature of the soan dun the study would be eventually useful for seismic hazard assessment and future infrastructure development in the seismotectonically active regions like soan dun of nw himalayan front

data files from the dry ships recordings of the chi chi earthquake seattle washington dry ships was a seismic refraction study of the seattle basin washington involving 29 chemical explosions recorded by 1008 seismographs conducted in september 1999 the e w trending dry ships line ran eastward from the olympic peninsula through the seattle basin to the foothills of the cascade mountains twenty eight refteks das model 07g 24 bit deployed along the dry ships line at 4 km intervals were programmed to record data continuously from three component sensors these 28 stations recorded the mainshock and several aftershocks of the m w 7 6 chi chi earthquake shin et al 2000 brocher et al 2000a the recordings were

surface deformation in the himalaya and adjoining piedmont zone of the ganga plain uttarakhand india determined by different radar interferometric techniques abstract the himalaya and adjoining ganga also called gangetic plain are traversed by a number of neotectonically active longitudinal and transverse faults however the pattern and extent of present day slip rate along these faults is not yet well known we herein present the results of our investigations directed in this direction surface deformations induced by active faults during a period of three years from august 2008 to august 2010 in the southern part of uttarakhand state india have been monitored multidate envisat radar images of the area have been analyzed by applying the latest interferometric synthetic aperture radar insar remote sensing techniques of persistent scatterer interferometry psi and atmospheric correction insar aci using the modis data both the psi and aci techniques were found capable of extracting valuable surface information despite the natural challenges of vegetal cover and mountainous terrain the study revealed some conspicuous surface deformation patterns which are related to active movements along some of the major faults thrusts of the area e g the himalayan frontal thrust hft and the transverse garampani kathgodam fault g kf the g kf acts as a segment boundary fault dividing the study area into two distinct parts with relative subsidence in the east and uplift in the west based on our presumption about the g kf a general tectonic model of the study area has been created the study has provided a better understanding of the active tectonics of the area

seismotectonics of taiwan abstract high quality seismicity data and focal mechanism solutions obtained during 1973 1983 by the permanent taiwan telemetered seismographic network and several temporary local seismographic networks are used for a detailed study of the seismotectonics of the taiwan area seismicity distribution in southern taiwan clearly reveals an east dipping benioff zone which has a thickness of about 30 km and begins to deepen along 121 e at a dip angle of 55 60 the leading edge of this benioff zone reaches a depth of about 180 km between 21 n and 22 n but tapers off to a shallower depth of about 100 km from 22 n to 23 n the presence of this seismic zone implies that subduction of the south china sea plate under the philippine sea plate extends from luzon northward to about 23 n the position of the northern boundary of the south china sea plate as tentatively defined according to the seismicity distribution passes through southern taiwan from the offshore area in the taiwan strait west of kaohsiung in an east northeast direction to the taitung area where a triple junction probably lies seismicity is found to disappear abruptly below a certain depth in many parts of taiwan this phenomenon may be attributed to the frictional to quasiplastic transition in the crust or upper mantle comparison of shallow seismicity with surface faults and fractures shows that all areas of active shallow seismicity are marked by densely developed faults and fractures however the converse is not necessarily true this may be partly due to the relatively short duration of seismicity data and partly due to excessive weakening of some of the severely faulted and fractured areas finally focal mechanism solutions for west central taiwan and the kuangfu fuli area in eastern taiwan predominantly show a maximum horizontal compression in the se nw direction which can be related to collision between the eurasian and philippine sea plates however focal mechanism solutions for both the hualien area in eastern taiwan and the tainan area in southwestern taiwan show remarkable irregularities which may result from local tectonic complexities

abruzzo italy earthquakes of april 2009 heterogeneous fault slip models and stress transfer from accurate inversion of envisat insar data abstract the seismic sequence that occurred in the abruzzo apennines near l aquila italy in april 2009 caused extensive damage and a large number of casualties more than 300 the earthquake struck an area in the italian apennines chain where several faults belonging to adjacent seismotectonic domains create a complex tectonic regime resulting from the interaction among regional stress buildup local stress changes caused by individual earthquakes and viscous elastic stress relaxation understanding such complex interaction in the apennines can lead to a large step forward in the seismic risk mitigation in italy the abruzzo earthquake has been very well recorded by interferometric synthetic aperture radar insar data much better than the first italian earthquake ever recorded by satellites namely the 1997 umbria marche earthquake envisat environmental satellite data for the abruzzo earthquake are in fact very clear and allow an accurate reconstruction of the faulting mechanism we present here an accurate inversion of vertical deformation data obtained by envisat images aimed to give a detailed reconstruction of the fault geometry and slip distribution the resulting fault models are then used to compute by a suitable theoretical model based on the elastic dislocation theory the stress changes induced on the neighboring faults the correlation of the subsequent mainshocks and aftershocks of the abruzzo sequence with the volumes undergoing increasing coulomb stress clearly evidence the triggering effect of coseismic stress changes on further seismicity moreover this analysis put in evidence which seismotectonic domains have been more heavily charged by stress released by the abruzzo mainshocks the most important faults significantly charged by the abruzzo sequence belong to the sulmona and avezzano tectonic domains taking into account the average regional stress buildup in the area the positive coulomb stress changes caused by this earthquake can be seen as anticipating the next earthquakes in the neighboring domains of 15 20 yr