western hellenic subduction and cephalonia transform local earthquakes and plate transport and strain abstract focal parameters of local earthquakes in the region of the ionian islands of western greece are constrained with a temporary dense array of three component seismographs operated jointly offshore and onshore seismic deformation is documented to be confined to the east of the n20 e striking steep continental slope west of cephalonia island the right lateral cephalonia transform fault ctf inferred from large earthquakes the pre apulian continental material appears to be only deforming east of the transform fault where it is in upper plate position to the hellenic subduction east of the transform fault the transmission velocity tomography from local earthquakes compared in depth section with a previous marine reflection profile provides evidence in support of a shallow landward dipping boundary around 12 km deep under the ionian islands along which they may override the lower plate on either side of this interface local earthquakes occur with different focal mechanisms in support with its interpretation as the interplate under cephalonia island reverse faulting deforms the upper plate along nw se structures which may also be affected by left lateral bookshelf faulting small earthquakes show normal faulting along the western coast of cephalonia and its extension 20 km ssw the trace of the ctf as inferred from the occurrence of the large strike slip earthquakes another group of normal fault earthquakes locates in the lower plate from under cephalonia to zante just outboard of a possible change of interplate dip suggested from reflection seismics landward under the islands these normal fault earthquakes appear to coincide in position with that of the load imposed by the upper plate transported over them rather than occurring in an outer rise outboard the plate boundary and trench as observed in other subductions and attributed to the control by the flexural bending of the lower plate under the pull of the sinking slab interpretation has to consider several peculiar features of plate interaction in western greece with respect to a steady state model for major subduction zones in particular a fast deformation of the upper plate in front of an orogenically overthickened crust and of the southwestward push of extruding anatolia its transport which is the cause of the migration of the plate boundary rather than the roll back of a slab which has been proposed to be detached possibly a flat and ramp shape of the interplate the geometrical complexity of the shear limit across the ctf between subduction and collision and the nearby variation of the nature of the foreland crust

the 1976 friuli ne italy thrust faulting earthquake a reappraisal 23 years later we revisit the 1976 friuli earthquake sequence by combining hypocenters relocation long period surface wave inversion field geology and strong motion modelling we show that fault related folding is the main active deformation by which the seismic energy was released during the main shock ms 6 5 and that some of the surface effects reported in 1976 correspond to widespread bedding planes displacements induced by flexural slip folding the fault evolved from blind to semi blind along strike showing the control of the inherited structural geology on the fault surface break and rupture arrest our fault model produces waveforms that fit the accelerograms recorded in the area

crustal stress and seismic activity in the ionian archipelago as inferred by satellite and ground based observations kefallinia greece different observational techniques are compared in order to investigate possible correlations in seismic activity the study site is the island of kefallinia greece where measure ments available included 1 dinsar dgps and dem data 2 soil exhalation measured by monitoring radon rn well content and 3 acoustic emissions ae at high and low frequency point like records with high temporal resolution ae records provide 1 relative time variation of the applied stress intensity and 2 the state of fatigue of stressed rock volumes the ae source our results indicate that the large spatial scale poor time resolution may be considered quite sat isfactory whereas fractal analysis of the ae time series displayed some discrepancies when com pared to analogous investigations in the italian peninsula therefore some refinement is needed in order to reach more precise interpretations of the relevant information available with this kind of data however both sets of observations appear in agreement with each other although more exhaustive investigations would require a suitable array of point like ae and rn or other measuring sites as well as longer data series the latter are particulary helpful for detailed interpretations of the different occurrences within tectonically complex settings where crustal stress crises are marked by various types of geological phenomena

redistribution of dynamic stress during coseismic ruptures evidence for fault interaction and earthquake triggering we investigate the spatiotemporal evolution of dynamic stress outside a rupturing extended fault the dynamic stress variations caused by a coseismic rupture in a half space are computed by using the discrete wavenumber and reflectivity methods after a transient phase the stress time history evolves to the final static stress value we compare the static stress changes resulting from this model with those computed from a static dislocation model we have applied this method to study the interactions between the first two normal faults which ruptured during the 1980 ms 6 9 irpinia earthquake these two subevents are separated in time by nearly 20 s while the third and last subevent occurred 40 s after the rupture onset we compute the dynamic stress changes caused by the rupture of the first subevent our modeling results show that the dynamic stress peak on the second subevent fault plane is reached between 7 s and 8 s after the rupture initiation on the main fault on the average the static stress level on the second subevent 20 s fault plane is reached nearly after 14 s the dynamic rupture did not jump from a rupturing segment to the adjacent one immediately but the triggering of the 20 s subevent is delayed by roughly 10 s with respect to the instant of occurrence of the dynamic stress peak induced by the 0 s event the dynamic stress pulse propagates along the strike direction of the second subevent fault plane at an average velocity of nearly 3 4 km s the delayed triggering of the second subevent can be interpreted in terms of the frictional properties of the faults in particular rate and state dependent frictional law can explain a delayed instability after a sudden change in stress using the estimated values of the subevent triggering delay and the shear stress change we attempt to constrain the parameter a on the 20 s fault the values here inferred agree well with those resulting from previous studies

kinematic links between subduction along the hellenic trench and extension in the gulf of corinth greece a multidisciplinary analysis abstract rapid northeast vergent subduction along the hellenic trench at 35 mm yr exists in concert with widespread extensional and strike slip faulting within the upper plate lithosphere of western greece integration of regional geomorphic geologic seismic gps remote sensing and field data demonstrates that young and active deformation in the area extending from the hellenic subduction boundary near kephalonia to the gulf of corinth consists of an interconnected network containing highly localized zones of deformation these bound a series of crustal fragments with relatively little internal deformation these deformation zones merge to form triple junction like features at the western end of the gulf of corinth and in the amvrakikos gulf at the western end of the corinth gulf most of its 14 2 mm yr of extension is relayed to the northwest along a prominent zone of left slip and extension through lake trichonis and the amphilochia fault zone 11 2 mm yr the remaining displacement across the western gulf of corinth is relayed into 7 2 mm yr of right slip on the southwest striking achaia fault zone which traverses the northwestern margin of the peloponnesus a second triple junction like feature occurs in the amvrakikos basin where the left slip amphilochia fault zone the right slip kephalonia transform fault 15 2 mm yr and the convergent thrust front of northern hellenides 4 2 mm yr are joined thus the extensional deformation in the gulf of corinth can be shown to be connected to convergence and subduction along the hellenic trench through a series of discrete deformation zones that are not dissimilar from those observed in the global plate tectonic system

broadband time domain modeling of earthquakes from friuli italy short period sp and long period lp seismograms written by the main shock and two principal aftershocks of the 1976 friuli italy earthquake sequence are modeled in the time domain using synthetic seismograms the main shock occurred on 6 may 1976 20h 00m m s 6 5 and both aftershocks on 15 september 1976 03h 15m m s 6 0 and 09h 21m m s 5 9 source models were determined initially by trial and error and then refined using a waveform inversion program two point sources of radiation are required to adequately model the aftershock short period records for the 09h 21m aftershock the model derived from short period records also produces good fits to the long period data the seismic moment of this earthquake is found to be 0 8 to 1 0 10 25 dyne cm the sp model for the 03h 15m aftershock on the other hand predicts long period synthetics which do not agree with the observations in particular the sp moment 0 37 10 25 dyne cm is about formula times smaller than the lp moment 1 10 25 dyne cm adding a long period component to the sp model considerably improves lp waveform and moment agreement in the case of the main shock a reasonable fit to the observed sp data is obtained using three point sources of radiation however lp synthetics computed using this model do not agree with the observations and the sp moment 0 65 10 25 dyne cm is a small fraction of the lp moment 3 to 5 10 25 dyne cm time function durations indicate that the individual events inferred from the sp records are radiated from patches of the fault having radii of 2 to 4 km and stress drops in the range 35 to 276 bars in comparison stress drops estimated from lp data are found to be 12 bars main shock and 24 bars 09h 21m aftershock these observations suggest that the short period instruments are sensitive to the high frequency radiation emitted from small high stress drop areas on the fault plane whereas the long period instruments record the overall motion during the earthquake

dry cave deposits and their palaeoenvironmental significance during the last 115 ka sodmein cave red sea mountains egypt the sodmein cliff foot cave is the present day remnant of an ancient cavity probably of karstic origin physical breakdown of the limestone bedrock rather than solution has governed its subsequent evolution long before 115 ka bp an estimated 8000 m 3 of debris came off the weathered roof and mixed with contemporaneous cliff rockfall over 4 m of sediments have since accumulated wet conditions outside the cave during isotopic stage 5e are documented by sedimentary properties of the j complex and by its detailed botanical and faunal content these wet conditions were of regional significance shortly after 115 ka bp further subsidence of the roof of the ancient cave led to the present day cave form the cave interior has remained dry up to the present but the deposits indicate an increase of animal passage and plant growth around 25 ka bp and during the holocene interglacial the latter period was rather arid in absolute terms receiving less precipitation under a less regular pluvial regime compared with the interglacial during isotopic stage 5e r 2002 elsevier science ltd all rights reserved

the 1998 and 2004 bovec krn slovenia seismic sequences aftershock pattern focal mechanisms and static stress changes summary we investigate the main seismotectonic aspects of the bovec krn sequences northwestern slovenia caused by the 1998 april 12 md 5 6 and the 12 july 2004 md 5 1 earthquakes the seismicity occurred along an extended right lateral strike slip fault zone trending nw se the analysis involves the aftershock pattern the focal mechanism of the largest events and the stress changes induced by the 1998 main shock the study is performed with high quality earthquake locations obtained with tomographic techniques that provided also velocity images of the fault zone related to the mechanical properties of the medium and to the geometry of the fault the tomographic model shows in the fault zone sharp lateral p wave velocity contrasts and marked lateral vp vs variations and images an extended high rigidity body along the fault where the 1998 and 2004 main shocks are located the aftershock activity is intense along highly heterogeneous zones characterized by sharp variation of vp and vp vs values the spatial distribution of the 1998 aftershocks defines sharp vertical planar features consistent with the orientation of the main strike slip fault while the 2004 aftershock pattern is quite diffuse the tomographic images and the spatial distribution of the aftershocks indicate a fault zone characterized by branches the fault plane solutions of the 1998 and 2004 main shocks show evidence of dextral strike slip motion concordant with the kinematics of the bovec krn fault the largest aftershocks of both sequences are characterized by different types of focal mechanisms and variable plane orientation the different focal mechanisms in the fault zone suggest that the mode of fracture of the largest aftershocks can be influenced by the fault strength heterogeneities imaged by the tomographic inversion the coulomb stress changes caused by the 1998 main shock was calculated to explore the stress transfer mechanism and the earthquake interactions a positive correlation of the coulomb stress increase is found with the largest aftershock md 4 6 and with a part of the aftershocks our modelling shows also that the coulomb stress changes caused by the 1998 main shock and its largest aftershock were not sufficient to trigger the 2004 main shock the locations of the 1998 and 2004 sequences correlate well with areas of increased coulomb stress changes when the regional tectonic loading is considered

single quartz grain electron spin resonance esr dating of a contemporary desert surface deposit eastern desert egypt abstract signal resetting by sunlight prior to burial is a crucial assumption in electron spin resonance esr dating of sediments this resetting process is expected to be completed to a greater extent in arid than in fluvial environments the present paper investigates the natural and artificially irradiated signal intensity of ti related centres in single quartz grains collected from the desert surface eastern desert egypt in order to test this hypothesis the results suggest that in most grains both the ti li and ti h signal are completely reset to zero additive dose curves based on the sum of both ti centres show an anomaly in the low dose region possible causes for this behaviour are briefly discussed three fitting procedures are conducted and each of them shows a different palaeodose distribution with a rather large spread in d e values it is concluded that similar fossil deposits would be datable by single grain esr using q band measurements of the ti li or ti h signals in quartz

changes in failure stress and stress transfer during the 1976 77 friuli earthquake sequence summary coulomb stress changes related to the sequence of strong earthquakes that affected the friuli area northeastern italy during the period 1976 77 have been investigated to explore the possibility of fault interaction and stress transfer mechanisms the seismic sequence that followed the mw 6 4 mainshock of 1976 may 6 consists of 5 events of mw between 5 2 and 6 0 during the same year and one event of mw 5 3 that occurred in 1977 september all characterized by thrust focal mechanisms the area is affected by a regional compressive stress which tends to activate n dipping thrust planes the goal of this study is to analyse and verify the relationship between the stress changes induced by the mainshock and the occurrence of subsequent events our results show that the mainshock induced a variation in the stress field in the area where most of the seismic events occurred our modelling shows a positive correlation between the areas of increased coulomb stress induced by the mainshock and the distribution of seismicity that followed this evidence suggests stress interaction and the possibility that the mainshock promoted the rupture of those faults associated with the event of 1976 may 9 mw 5 1 and the events of 1976 september 11 mw 5 2 and 5 6 1976 september 15 mw 6 0 and 1977 september 16 mw 5 3 the coulomb stress caused by co seismic dislocations decreased in the zone where an mw 5 9 earthquake occurred on september 15 at 03 15 when we included the contribution of the regional tectonic loading in the calculation of coulomb stress changes we found a positive correlation between the hypocentral area of the september 15 03 15 event and the area of coulomb stress increase aftershocks that occurred after the mainshock but before the september 15 03 15 event are also located in the area of coulomb stress increase

stress transfer by the 1988 1989 m 5 3 and 5 4 lake elsman foreshocks to the loma prieta fault unclamping at the site of peak mainshock slip we study the stress transferred by the june 27 1988 m 5 3 and august 8 1989 m 5 4 lake elsman earthquakes the largest events to strike within 15 km of the future loma prieta rupture zone during 74 years before the 1989 m 6 9 loma prieta earthquake we find that the first lake elsman event brought the rupture plane of the second event 0 3 1 6 bars 0 03 0 16 mpa closer to coulomb failure but that the lake elsman events did not bring the future loma prieta hypocentral zone closer to failure instead the lake elsman earthquakes are calculated to have reduced the normal stress on or undamped the loma prieta rupture surface by 0 5 1 0 bar 0 05 0 10 mpa at the site where the greatest slip subsequently occurred in the loma prieta earthquake this association between the sites of peak unclamping and slip suggests that the lake elsman events did indeed influence the loma prieta rupture process unclamping the fault would have locally lowered the resistance to sliding such an effect could have been enhanced if the lowered normal stress permitted fluid infusion into the undamped part of the fault although less well recorded the ml 5 0 1964 and ml 5 3 1967 corralitos events struck within 10 km of the southwest end of the future loma prieta rupture no similar relationship between the normal stress change and subsequent loma prieta slip is observed although the high slip patch southwest of the loma prieta epicenter corresponds roughly to the site of calculated coulomb stress increase for a low coefficient of friction the lake elsman loma prieta result is similar to that for the 1987 m 6 2 elmore ranch and m 6 7 superstition hills earthquakes suggesting that foreshocks might influence the distribution of mainshock slip rather than the site of mainshock nucleation

iterative deconvolution of regional waveforms and a double event interpretation of the 2003 lefkada earthquake greece the moment tensor inversion for multiple point sources based on kikuchi and kanamori 1991 was extended to full waveform data at regional or local distances the new code proved to be efficient for retrieving major source contributions of the 2003 lefkada greece earthquake the source model was derived from five three component regional stations epicentral distances 140 km at periods 10 20 s two main events dominated the rupture process one at the lefkada island comprising three subevents of total moment 0 9 1018 n m and the other at the cephalonia island comprising one subevent of 0 5 1018 n m their spatial and temporal separation is 40 km and 14 s respectively they can be understood as two earthquakes the uncertainty estimate based on reduced data sets repeatedly excluding a station shows that the cephalonia subevent and the major lefkada subevent are very well resolved regarding their position time and focal mechanism the source model explains well the aftershock distribution characterized by two clusters at the lefkada and cephalonia islands respectively the focal mechanisms of the two main subevents are predominantly right lateral strike slip of south southwest north northeast orientation the cephalonia subevent occurred on a less steeply dipping fault with a small thrust component large deviations from pure double couple were found but interpreted as artifacts the new software developed in this article fortran code and matlab graphic user interface is freely available online material color graphics and 3d visualization of the 2003 lefkada earthquake sequence

late cenozoic deformation of the hellenide foreland western greece the late cenozoic structural evolution of western greece involved the shortening of mesozoic passive continental margin and cenozoic foreland basin sequences in a foreland propagating fold and thrust system and superimposed neotectonic deformation related to the development of an active island arc although the pre apulian zone has been regarded as the undeformed western foreland to the thrust belt three dimensional exposures in the ionian islands of kephalonia and zakinthos afford evidence of significant late neogene and quaternary shortening including thrusting on reactivated normal faults time relations and fault kinematics show that these structures are compatible with the westward migration of the locus of hellenide thrusting beyond its previously recognized limit and outer arc compression related to active subduction the presence of the pre apulian zone in the west contrasts with other aegean foreland areas where no such intermediate block lay between the thrust pile and old mesozoic oceanic crust consequently the pre apulian block took up continued hellenide shortening in the late miocene while oceanic crust was being overridden subducted in southern parts of the arc to the east the pre apulian zone subsequently overrode the ocean floored ionian sea during the late neogene the confusion in determining driving mechanisms for late cenozoic deformation in western greece and the apparent conflict between evidence for the age of initial subduction in different parts of the arc are explained by this model which is consistent with regional considerations including structuration in adjacent areas and important paleomagnetic rotations in the arc

european mediterranean regional centroid moment tensors 1997 2000 the mediterranean region is seismically very active and undergoing rapid deformation earthquakes as strong as m 6 are present but relatively rare on the other hand moderate magnitude seismicity 4 5 m 5 5 is widespread and often damaging an improved knowedge of moderate magnitude earthquakes can contribute significantly to a better understanding of active tectonics in the region harvard centroid moment tensors cmt today represent the most widely used reference for reliable source mechanisms but modelling seismic sources with the cmt technique for earthquakes with magnitude less than m 5 5 5 is quite difficult since 1997 we are using an extension of the standard cmt algorithm to compute regional centroid moment tensors rcmt for moderate magnitude earthquakes mw as low as 4 0 analyzing intermediate period surface waves from regional and teleseismic seismograms we routinely apply the algorithm to european mediterranean seismicity to produce a catalog of seismic moment tensors for events with magnitude between 4 5 and 5 5 which generally are not included in the harvard cmt catalog in this paper we show the results for earthquakes that occurred between 1997 and 2000 consisting of 252 solutions and we discuss the characteristics of the catalog and the areas where these new data are most relevant

changes in static stress on southern california faults after the 1992 landers earthquake the magnitude 7 5 landers earthquake of 28 june 1992 was the largest earthquake to strike california in 40 years the slip that occurs in such an earthquake would be expected to induce large changes in the static stress on neighbouring faults these changes in stress should in turn affect the likelihood of future earthquakes stress changes that load faults towards failure have been cited as the cause of small1 5 moderate6 and large7 earthquakes conversely those that relax neighbouring faults have been related to a decrease in seismicity5 here we use an elastic half space model8 to estimate the stress changes produced by the landers earthquake on selected southern california faults including the san andreas we find that the estimated stress changes are consistent with the triggering of four out of the five aftershocks with magnitude greater than 4 5 and that the largest changes 1 10 bar occurring on part of the san bernardino segment of the san andreas fault may have decreased the time to the next magnitude 8 earthquake by about 14 years

calibration of the hglp seismograph network and centroid moment tensor analysis of significant earthquakes of 1976 abstract a methodology is developed for determining accurate instrument response functions for seismographs of the high gain long period hglp network recordings of daily transient calibration pulses provide a detailed history of the time varying responses of the hglp stations when the instrument displacement transfer function is available knowledge of the seismometer mass calibration coil constant and calibration current allows for the prediction of the shape and amplitude of the calibration signal by simple integration of the transfer function in theory the inverse of this statement is also true but in practice noise in the recordings contaminates the instrument response function recovered through direct differentiation of the calibration pulse the unknown transfer function of the seismograph system is instead first described by the product of the nominal responses of its mechanical and electromagnetic components specific values of the characteristic parameters for each seismograph component are subsequently determined by iterative least squares minimization of the misfit between observed and model transient calibration pulses by application of this method to daily calibration pulses recorded on the ten stations of the hglp network refined instrument response functions for 1976 and part of 1975 are determined the results agree well with single frequency amplitude calibration data recovered from station maintenance records and produce synthetic waveforms which are consistent with data from other well calibrated stations we use the recalibrated hglp data together with long period data from early international deployment of accelerometers ida and seismic research observatory sro digital stations to determine 108 centroid moment tensor cmt solutions for moderate and large earthquakes of 1976 the new cmt results for several major earthquakes including the tangshan guatemala and friuli events are compared with those of previous studies

stress field of italy mean stress orientation at different depths and wave length of the stress pattern we have studied the stress pattern of italy using a dataset with 590 data records from the world stress map database release 2008 and 106 new data records to test the hypothesis the mean orientation of maximum horizontal stress sh is different at different depth sections for this we split the dataset into a shallow 0 6 km and a deep 6 40 km depth section for the data analysis we used a new statistical tool that calculates the mean sh orientation on a 0 2 grid the tool takes into account the distance to each grid point number and quality of the data records within the search radius and the radial distribution the result is a smoothed italian stress map that displays both the mean sh orientation and the wave length of the stress pattern the stress pattern does not vary in depth except for two areas sardinia and southern apulia therefore stress data from different depths can be used to estimate the mean sh orientation and the wave length of the stress pattern in italy furthermore the smoothed italian stress map reveals that most of italy has short wave length stress patterns 150 km this indicates that the stress field is not controlled by first order stress sources of plate tectonics i e the convergence of africa with respect to eurasia but that second order stress sources such as topography density strength contrasts and major faults systems are of great importance in four regions western part of the alps northern tuscany northern adriatic sea calabria and eastern part of sicily the wave length is 100 km high values of the circular variance of the mean sh orientation observed here are driven by third order local stress sources such as basins or local neotectonic structures

palaeohydrology and its impact on groundwater in arid environments gebel duwi and its vicinities eastern desert egypt abstract from ancient times access to water in arid and hyper arid regions has been crucial for life increased knowledge about groundwater conditions is therefore extremely important for the future development of desert areas gebel duwi a limestone ridge sited in the today hyper arid eastern desert of egypt was chosen for testing current hypotheses concerning the interdependence of palaeohydrologic features and geologic settings for groundwater investigations two sub basins are identified in affecting gebel duwi wadi nakheil and wadi sodmein both have extraordinary high stream order indicating the reality of a very old drainage system several additional palaeohydrologic features such as wadi terraces alluvial fans and playa deposits are also recorded in these sub basins these features as well as finds from an important archaeological site sodmein cave provide information about palaeoenvironmental changes and wetter climatic periods in the younger geologic past mainly in the late pleistocene and holocene which have affected the occurrence of present day groundwater this study combines new results of geological and geomorphological field studies examinations of digital elevation models as well as of rock and water analyses in an integrated approach resulting maps comprise landforms lithology elevation drainage lines slope structural lineaments and flow directions the hydrogeologic condition indicates suitable locations for groundwater recharge and accumulation the research presented is interdisciplinary in approach and is recommended for future studies with regard to groundwater exploration sustainable groundwater use and the protection of archaeological sites in arid lands

eoalpine and mesoalpine tectonics in the southern alps according to structural and stratigraphic data eoalpine and mesoalpine tectonics can be clearly recognized in the southern alps and distinguished from the better known neoalpine deformation

quantification of everest region glacier velocities between 1992 and 2002 using satellite radar interferometry and feature tracking quincey d j luckman a benn d 2009 quantification of everest region glacier velocities between 1992 and 2002 using satellite radar interferometry and feature tracking journal of glaciology 55 192 596 606 sponsorship knowledge transfer project no 3742

strain accumulation in southern california 1973 1980 frequent surveys of seven trilateration networks in southern california over the interval 1973 1980 suggest that a regional increment in strain may have occurred in 1978 1979 prior to 1978 and after late 1979 the strain accumulation has been predominantly a uniaxial north south compression this secular trend was interrupted sometime in 1978 1979 by an increment in both north south and east west extension in five of the seven networks the onset of this change appears to have occurred first in the networks farthest south the changes occurred without any unusual seismicity within the networks but the overall seismicity in southern california was unusually low prior to and has been unusually high since the occurrence the average principal strain rates for the seven networks in the 1973 1980 interval are 0 17 mu strain yr north south contraction and 0 08 mu strain yr east west extension although the observed increment in strain could be related to unidentifed systematic error in the measuring system a careful review of the measurements and comparison with three other measuring systems reveal no appreciable cumulative systematic error

influence of static stress changes on earthquake locations in southern california earthquakes induce changes in static stress on neighbouring faults that may delay hasten or even trigger subsequent earthquakes1 10 the length of time over which such effects persist has a bearing on the potential contribution of stress analyses to earthquake hazard assessment but is presently unknown here we use an elastic half space model11 to estimate the static stress changes generated by damaging magnitude m 5 earthquakes in southern california over the past 26 years and to investigate the influence of these changes on subsequent earthquake activity we find that in the 1 5 year period following a m 5 earthquake any subsequent nearby m 5 earthquake almost always ruptures a fault that is loaded towards failure by the first earthquake after this period damaging earthquakes are equally likely to rupture loaded and relaxed faults our results suggest that there is a short period of time following a damaging earthquake in southern california in which simple coulomb failure stress models could be used to identify regions of increased seismic hazard

early detection and in depth analysis of deformation phenomena by radar interferometry the spaceborne differential interferometric sar dinsar technique may play an important role in the measurement of land deformation phenomena especially in urban suburban and industrial areas in order to fully exploit its capabilities and increase its operational use this paper proposes two complementary levels of analysis the first one is a comprehensive low cost screening in order to detect unknown subsidence phenomena over large areas this analysis which provides a first estimation of deformations has to be performed using a limited set of sar images the second level includes an in depth quantitative analysis based on large image stacks which requires more image acquisition and data processing resources this type of analysis can be typically used to study deformation phenomena of special relevance where an effective support to the decision makers requires a fully quantitative estimation of deformations the two levels of analysis were proved over a test area of about 2100 km2 located in catalonia spain without any a priori information seven deformation phenomena were detected using a reduced set of interferograms furthermore the quantitative analysis of a subsidence of small spatial extent which was based on ascending and descending datasets confirmed the capability of dinsar to quantitatively assess deformation phenomena

stress field in friuli ne italy from fault plane solutions of activity following the 1976 main shock abstract fault plane solutions of 78 earthquakes with magnitude larger than 3 2 which occurred in friuli between may 1976 and august 1979 have been used to estimate the orientations of the principal stress axes by an inversion technique the analysis of the confidence limits and the average angular misfit of the solution found when inverting the entire data set revealed that faulting was not produced by a uniform stress distribution subdivision of the study area into smaller volumes did not lead to significant improvements in terms of stress uniformity whereas temporal subdivision of the sample reduced significantly misfit and confidence areas of the solution for some data sets therefore we conclude that the stress directions changed as a function of time a nearly uniform stress direction compatible with tectonic models proposed for the study area ca n s convergence of the adriatic and south alpine units was found between the main event of 6 may 1976 m l 6 4 and the strong aftershocks of mid september 1976 5 1 m l 6 1 the analysis of the individual misfit cumulative pattern reveals that some degree of stress heterogeneity appeared in july 1976 which is explained here in terms of heterogeneous local responses of the stress field to the seismic activity superimposed to the regional compressive factor the degree of perturbation of the principal stress directions by local effects increased with time and showed in particular a clear variation after the strong earthquakes of mid september 1976 the perturbations appear to be reflected by low magnitude quakes whereas the faulting in strong events is compatible with the regional stress field

finite fault parameters of the september 1976 m 5 aftershocks in friuli ne italy abstract on september 1976 four strong aftershocks with m 5 occurred in the friuli area ne italy causing more damage with respect to that caused by the m6 4 mainshock that occurred on may 6 1976 although many studies have been published on the 1976 friuli seismic sequence only recently have finite fault models based on geological considerations galadini et al 2005 burrato et al 2008 been proposed for these aftershocks the aim of our study is to model the september 1976 seismic sources as finite faults by computing finite fault synthetic seismograms for several possible proposed fault models and nucleation locations the seismicity distribution following each of the four events gives us some further information about the areal extent of the related fault and its rupture propagation about 9000 synthetic seismograms are computed for all the tested fault models adopting the reflectivity technique for an upper cutoff frequency of 1 hz a trial and error procedure is used to find the best fit between the recorded and computed peak ground acceleration derived from signals filtered at 1 hz that identifies the final models these are selected also on the basis of the existing knowledge of fault traces in the area the four best fit models seem to be well related to the main barcis staro selo fault system their spatial temporal sequence evidencing an overall progressive east to west migration of the seismic activity related to the 1976 sequence

near field response of a 1d structure alluvial site abstract we present a case history of the complicated strong motion responses at a site with an almost 1d structure buia in the near field of four m w 5 2 6 0 earthquakes in the friuli plain of italy in one case 15 september 1976 09 21 utc m w 6 0 the 47 m alluvial cover of buia experienced spectral amplitudes lower than its reference site on rock due to the different back azimuths from the source the largest peaks at buia occurred during an m w 5 6 event for practical purposes we tested 1 subjectivity when preparing the 1d models using a blind test with three experts 2 1d linear linear equivalent or nonlinear modeling in common practice and 3 the current seismic regulations we also used noise recordings and the weak motion velocities recorded for local events with digital triplets on the top and the bottom of the alluvial cover buia s response to weak events was more stable than its response to strong ones a simple 1d model five layer under linear conditions with good knowledge of the propagation velocities was able to reproduce the frequencies of the two relative strong motion maxima with an average amplitude underestimation of 1 5 the nonlinear approach simulated the two recorded maxima with slight shifts in frequency because the disaggregation of the seismic hazard showed that the four destructive shocks studied represent the magnitude and distance ranges that dominate the hazard of buia we can conclude that the response spectra of the new italian and european rules were sufficiently preventive notwithstanding the aforementioned complications in the near field

phase gradient approach to stacking interferograms the phase gradient approach is used to construct averages and differences of interferograms without phase unwrapping our objectives for change detection are to increase fringe clarity and decrease errors due to tropospheric and ionospheric delay by averaging many interferograms the standard approach requires phase unwrapping scaling the phase according to the ratio of the perpendicular baseline and finally forming the average or difference however unique phase unwrapping is usually not possible since the phase gradient due to topography is proportional to the perpendicular baseline phase unwrapping is unnecessary prior to averaging or differencing phase unwrapping may be needed to interpret the results but it is delayed until all of the largest topographic signals are removed we demonstrate the method by averaging and differencing six interferograms having a suite of perpendicular baselines ranging from 18 to 406 m cross spectral analysis of the difference between two tandem interferograms provides estimates of spatial resolution which are used to design prestack filters a wide range of perpendicular baselines provides the best topographic recovery in terms of accuracy and coverage outside of mountainous areas the topography has a relative accuracy of better than 2 m residual interferograms single interferogram minus stack have tilts across the unwrapped phase that are typically 50 mm in both range and azimuth reflecting both orbit error and atmospheric delay smaller scale waves with amplitudes of 15 mm are interpreted as atmospheric lee waves a few global positioning system gps control points within a frame could increase the precision to 20 mm for a single interferogram further improvements may be achieved by stacking residual interferograms

geomorphology and quaternary geology of the dakhla oasis region egypt abstract dakhla oasis 25 5 n 29 e occupies a structurally localized depression at 90 140 m above sea level 1200 km 2 in area below a 300 m escarpment bordering the libyan plateau western desert of egypt semi arid intervals of the quaternary period generated eight sedimentary formations separated by erosion during hyper arid intervals sediments comprise three generations of colluvial fluvial fanglomerates two generations of tabular spring laid clastic and chemical sediments two generations of mound springs and basinal sediments of fluvio lacustrine evaporitic pluvio aeolian and aeolian origins discussion of these sediments is organized according to geomorphic region from north to south plateau scarp and piedmont lowland and cuesta plain chronological evidence is restricted to many radiocarbon dates of holocene cultural material associated with playa sediments 9 4 5 ka a th u isochron age of 62 0 7 6 ka for basinal evaporites and two th u ages of 176 and 170 ka for a boulder of derived travertine the regional quaternary sequence is reconstructed from stratigraphic and geomorphic relationships of the sediments and erosion surfaces it is broadly similar to sequences earlier reconstructed in the topographically similar kharga oasis region 150 km to the east and kurkur oasis 400 km to the south southeast speculations on chronology and driving mechanism are offered in conclusion

source parameters and stress release of seismic sequences occurred in the friuli venezia giulia region northeastern italy and in western slovenia abstract the source parameters of the major events of a swarm and of two seismic sequences occurred in the friuli area northeastern italy and in western slovenia were estimated the claut swarm c96 occurred since the end of january to june 1996 with a md 4 3 major shock and it appears composed of three sub sequences the two sequences are the kobarid sequence k98 started on april 12 1998 with a md 5 6 mainshock and the m te sernio s02 sequence caused by the february 14 2002 earthquake md 4 9 acceleration and velocity data recorded by the local seismic network of the istituto nazionale di oceanografia e di geofisica sperimenale ogs and corrected for attenuation were employed to estimate seismic moments and radiated energies source dimensions were inferred from the computed corner frequencies and the stress release was estimated from the brune stress drop the apparent stress and the rms stress drop on the whole seismic moments range from 1 7 1012 to 1 1 1017 n m and radiated energies are in the range 106 1013 j brune stress drops are scattered and do not show any evidence of a self similarity breakdown for sources down to 130 m radius the radiated seismic energy scales as a function of seismic moment with a slope of the scaling relation that decreases for increasing seismic moments the mechanism of stress release was analyzed by computing the parameter of zuniga zuniga r 1993 frictional overshoot and partial stress drop which one bull seismol soc am 83 939 944 the k98 and s02 sequences are characterized by a wide range of the parameter with stress drop mechanism varying from partial locking to overshoot cases the values of the c96 swarm are more homogeneous and close to the orowan s condition the radiated seismic energy and the ratio of stress drop between mainshock and aftershocks appear different among the analyzed cases we therefore investigated the relationship between the stress parameters of the main shock and the energy radiated by the aftershock sequences for this purpose we also estimated the source parameters of two other sequences occurred in the area with mainshocks of md 4 1 and 5 1 respectively we found a positive correlation between the brune stress drop of the mainshock and the ratio between the radiated energy of the mainshock and the summation of the energies radiated by the aftershocks

seismic b value anomalies in the sumatran region seismotectonic implications abstract the spatial variations in the seismic b value seismic moment bouguer gravity change and fault plane solution are estimated in the sumatran region based on homogeneous seismicity data from june 2005 to march 2012 to investigate the seismotectonic characteristics and tectonic activity between the 2004 sumatran earthquake and the 2012 east indian ocean earthquakes based on changes in the seismicity rate this time period is divided into five intervals with different earthquake distributions and faulting styles the seismic b values faulting mechanisms and seismic moment release values are mapped throughout the sumatran region and the gravity change every two years between the 2004 event and the 2012 events are determined from satellite grace gravity data the b values vary from 0 45 to 1 59 and an inverse correlation is observed between the b values and convergence rates low b values are located at depths between 20 km and 40 km in the subduction zone and between 20 km and 35 km in the oceanic plate the lowest b values are located at a depth of approximately 28 km in both regions which indicates a homogeneous fault system between them the areas with low b values are associated with megathrust and strike slip mechanisms while the area with the lowest b values is dominated by a megathrust mechanism seismically active regions have low b values associated with a high stress accumulation and high seismic moment release low b value areas are located mainly along the andaman sunda trench and andaman nicobar sumatra forearc temporal variations in the seismicity distribution and faulting style are recognized with temporal variations in the b values in each period relationships exist between the epicenter of the 2004 event and the location of the maximum bouguer gravity change in 2012 and between the epicenters of the 2012 events and the location of the maximum bouguer gravity change in 2004 furthermore a zone of continuous 2 year positive gravity change is located near the nicobar islands the 2004 event boost the 2012 events and intraplate seismicity via stress transfer the seismicity distributions in individual periods within the studied timeframe highlight the active and locked portions of the fault systems

ice velocity determined using conventional and multiple aperture insar abstract we combine conventional interferometric synthetic aperture radar insar and multiple aperture insar mai to determine the ice surface velocity on the langjokull and hofsjokull ice caps in iceland in 1994 this approach allows the velocity of the 20 principal ice cap outlet glaciers to be fully resolved we show that mai leads to displacement estimates of finer resolution 15 versus 150 m and superior precision 5 versus 15 cm to those afforded by the alternative technique of speckle tracking using sar data acquired in ascending and descending orbits we show that ice flows within 15 of the direction of maximum surface slope across 66 of the ice caps it is therefore possible to determine ice displacement over the majority of the ice caps using a single sar image pair thereby reducing errors associated with temporal fluctuations in ice flow

holocene environmental changes in the gebel umm hammad eastern desert egypt abstract gebel umm hammad in the red sea mountains east of quseir egypt today enjoys small but irregular amounts of winter rain enabling the widening of joint controlled openings in the thebes limestone cavities are especially affected by flaking while rock fragmentation is more active on the outside the sedimentological and botanical study of fan deposits at the outlet of a karstic shaft in the tree shelter showed the local holocene environmental evolution three periods of different degree of aridity can be considered i before 8120 45 bp utc 5389 bedload aggradation points to rare but occasionally heavy rains lasting for several hours attaining intensities of more than 76 mm h and covering some 20 km2 wadi flash floods occasionally attained bankfull stage ii since 8120 45 bp utc 5389 such heavy rains have not occurred in the egyptian red sea mountains instead a more moderate but maybe wetter precipitation regime was established the karstic shafts were active and there was water and life in the desert two humid pulses can be distinguished within this period the first occurs at 8000 bp the second between 6630 45 grn 22560 and 6770 60 bp grn 22562 iii after the last wet culmination there was a gradual shift to drier conditions shortly after 5000 bp modern climatic conditions are believed to have been attained today the occasional rain storms are less heavy than before 8000 bp bankfull stage river floods do not occur instead secondary channels are eroded in the wadi beds the general arid character during the whole period and the inherent local and temporal variations in precipitation patterns might explain apparent aberrations between the palaeoenvironmental evolution of the tree shelter site and other remote study areas in egypt and sudan

depth determination of north italian earthquakes using grafenberg data surface reflections such as pp and sp have long been used to determine the source depth of teleseismic events due to difficulties in identifying these phases at single narrow band stations they have rarely been used for regional events correlation over an array of stations and the possibility of applying different filters to broadband data allows such phases to be identified we describe a method to determine the source depth which uses such depth phases at regional distances complete theoretical seismograms are an important aid for the interpretation of these depth phases the method is demonstrated using small events from the lombardia region and large events from friuli northern italy good agreement is achieved with depth determinations by other authors for the friuli events relative source depths are determined very accurately since only time differences need to be compared

the cephalonia transform fault and its extension to western lefkada island greece the central area of the ionian islands is dominated by the existence of a major tectonic structure called the cephalonia transform fault ctf its main part cephalonia segment has been identified by previous work based on the spatial distribution of earthquake foci fault plane solutions of strong earthquakes active tectonics structural studies and geodetic measurements this part cephalonia segment which exhibits strike slip motion with a thrust component strikes in a northeast direction dips to the southeast and has a length of 90 km in the present paper information concerning new fault plane solutions orientation of isoseismals sea bottom topography and recent gps results are used to further check the properties of this southern part of the ctf and to explore its northeastward prolongation to lefkada island it is shown that the ctf is extended to the western coast of lefkada this northern branch lefkada segment of the ctf which is also characterized by strike slip motion with a thrust component strikes in a north northeast direction dips to the east southeast and has a length of 40 km these two segments of the ctf form a major kinematic boundary where the slip rate is 2 3 cm yr

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

new constraints on the rapid crustal motion of the aegean region recent results inferred from gps measurements 1993 1998 across the west hellenic arc greece abstract in this paper we present the most recent observations of crustal motion across the entire west hellenic arc wha these are based on repeated gps measurements carried out in the period from 1993 to 1998 the results are presented in terms of trajectories and rates relative to eurasia within these five years southwestern greece has moved to the southwest by an average rate of 30 mm a increasing from 10 mm a at the island of lefkada in the center of the ionian islands to nearly 40 mm a along the southwest part of the peloponnesus and to 35 mm a on the islands of crete and gavdhos the data provide strong evidence that distributed shear strain starts at the kephalonia fault zone kfz were an anomalously high earthquake activity is also observed a striking interruption of the motion is seen at the island of strofades at the southwest leading edge of the wha where a south oriented displacement of 12 cm was detected coincident with the m 6 4 strofades earthquake of nov 18 1997

reassessment of the source of the 1976 friuli ne italy earthquake sequence from the joint inversion of high precision levelling and triangulation data summary in this study we revisit the mechanism of the 1976 friuli ne italy earthquake sequence main shocks mw 6 4 5 9 and 6 0 we present a new source model that simultaneously fits all the available geodetic measurements of the observed deformation we integrate triangulation measurements which have never been previously used in the source modelling of this sequence with high precision levelling that covers the epicentral area we adopt a mixed linear non linear optimization scheme in which we iteratively search for the best fitting solution by performing several linear slip inversions while varying fault location using a grid search method our preferred solution consists of a shallow north dipping fault plane with assumed azimuth of 282 and accommodating a reverse dextral slip of about 1 m the estimated geodetic moment is 6 6 1018 nm mw 6 5 in agreement with seismological estimates yet our preferred model shows that the geodetic solution is consistent with the activation of a single fault system during the entire sequence the surface expression of which could be associated with the buia blind thrust supporting the hypothesis that the main activity of the eastern alps occurs close to the relief margin as observed in other mountain belts the retrieved slip pattern consists of a main coseismic patch located 3 5 km depth in good agreement with the distribution of the main shocks additional slip is required in the shallower portions of the fault to reproduce the local uplift observed in the region characterized by quaternary active folding we tentatively interpret this patch as postseismic deformation afterslip occurring at the edge of the main coseismic patch finally our rupture plane spatially correlates with the area of the locked fault determined from interseismic measurements supporting the hypothesis that interseismic slip on the creeping dislocation causes strain to accumulate on the shallow above 10 km depth locked section assuming that all the long term accommodation between adria and eurasia is seismically released a time span of 500 700 years of strain accumulating plate motion would result in a 1976 like earthquake

geomorphic indicators of holocene winds in egypt s western desert abstract geomorphic mapping of egypt s western desert from landsat mss images reveals oriented aeolian landforms that record in part holocene winds wind directions reconstructed from these landforms indicate the dominance of n s airflow from 30 n to 20 n turning clockwise southward to ne sw conformable with modern circulation a second direction appears over western egypt w between 30 n and 26 n nw between 26 n and 20 n cross cutting aeolian landforms show that w nw winds are older than the n ne winds geomorphic evidence abundant south to 26 n and less abundant to 20 n also indicates that w and nw winds were early holocene palaeowesterlies some evidence also indicates that they extended eastward to at least 30 e perhaps to the red sea these winds steered moist atlantic mediterranean air masses to egypt sustaining early holocene lakes and playas north of the limit of tropical monsoonal rainfall at 20 n upon aridification beginning after 5 kyr bp yardangs oriented west to east were eroded in early holocene basinal sediments in western egypt indicating that these winds continued there for 1 2 kyr until 3 4 kyr bp optically stimulated luminescence osl ages of surface sand sheet in southern egypt indicate that the present north south winds were established ca 3 4 kyr bp at the same time as the northern savanna boundary was stabilized at its present position

accuracy of topographic maps derived from ers 1 interferometric radar an interferometric radar technique for topographic mapping of surfaces promises a high resolution approach to the generation of digital elevation models the authors present analyses of data collected by the synthetic aperture radar instrument on board the ers 1 satellite on successive orbits use of a single satellite in a nearly repeating orbit is attractive for reducing cost and spaceborne hardware complexity also it permits inference of changes in the surface from the correlation properties of the radar echoes the data have been reduced to correlation maps and digital elevation models the correlation maps show that temporal correlation decreases significantly with time but not necessarily at a constant well defined rate likely depending on environmental factors when correlation among passes remains high however it is possible to form digital elevation models analyses of noise expected in ers 1 interferometric data collected over alaska and the southwestern united states indicate that maps with relative errors less than 5 m rms are possible in some regions however orbit uncertainties imply that tie points are required in order to reduce absolute height errors to a similar magnitude the authors find that about 6 tie points per 40 spl times 40 km scene with 5 m rms or better height accuracy are needed to keep systematic map height errors below 5 m rms the performance of the ers 1 radar system for topographic applications though useful for a variety of regional and local discipline studies may be improved with respect to temporal decorrelation errors and absolute height acuity by modifying the orbit repeat period and incorporating precise orbit determination techniques the resulting implementation will meet many but not all objectives of a global mapping mission

interferometric radar measurement of ocean surface currents we describe a new method of measuring surface currents using an interferometric synthetic aperture radar an airborne implementation has been tested over the san francisco bay near the time of maximum tidal flow resulting in a map of the east west component of the current only the line of sight component of velocity is measured by this technique where the signal to noise ratio was strongest statistical fluctuations of less than 4 cm s 1 were observed for ocean patches of 60 60 m

earthquake induced rockfall hazard zoning abstract a methodology for quantitative probabilistic hazard zonation for earthquake induced rockfalls is presented and demonstrated in the area of friuli eastern italian alps affected by the 1976 mw 6 5 earthquake four rockfall datasets have been prepared both from historical data analysis and field surveys the methodology relies on a three dimensional hazard vector whose components include the rockfall kinetic energy the fly height and the annual frequency the values of the first two components are calculated for each location along the slope using the 3d rockfall runout simulator hy stone the rockfall annual frequency is assessed by multiplying the annual onset frequency by the simulated transit frequency the annual onset frequency is calculated through a procedure that combines the extent of unstable areas calculated for 10 different seismic hazard scenarios with different annual frequencies of occurrence and the magnitude relative frequency relationship of blocks as derived from the collected field data for each annual frequency of occurrence the unstable area is calculated as a function of morphometric and earthquake characteristics a series of discriminant analysis models using the rockfall datasets and dems of different resolution 1 and 10 m identified the controlling variables and verified the model robustness in contrast with previously published relationships we show that the slope curvature plays a relevant role in the computation of the unstable area

computer assisted discrimination of morphological units on north central crete greece by applying multivariate statistics to local relief gradients traditional manual methods have been employed for decades to measure geomorphometric properties from topographic maps such measurement techniques tend to be tedious and time consuming and the designated landform elements cannot be easily overlaid on any digital map and imagery for further applied research this study deals with a new quantitative geomorphometric procedure based on the multivariate statistical analysis of local topographic gradients within a part of northcentral crete this method employs sets of computer algorithms that automatically extract and classify geomorphometric properties from digital elevation models dems this was done by evaluating the morphological setting around each pixel of the dem along the eight azimuth directions isodata unsupervised classification was implemented to generate 10 morphometric classes showing the spatial distribution of areas with a similar geomorphic scenario results revealed that this approach permitted a quick estimation of the spatial distribution of morphologically homogeneous terrain units it also demonstrated the ability of the delineated landform elements to be superimposed on any digital map and imagery for further investigation this became apparent during the examination of the relationship between the geomorphological units and the land cover land use types in the study area both relative association and the dominant land cover land use types in relation to geomorphological units are presented d 2003 elsevier b v all rights reserved

the lowest place on earth is subsiding an insar interferometric synthetic aperture radar perspective since the early 1990s sinkholes and wide shallow subsidence features wssfs have become major problems along the dead sea shores in israel and jordan sinkholes are readily observed in the field but their locations and timing are unpredictable wssfs are often difficult to observe in the field however once identified they delineate zones of instability and increasing hazard in this study we identify characterize and measure rates of subsidence along the dead sea shores by the interferometric synthetic aperture radar insar technique we analyze 16 sar scenes acquired during the years 1992 to 1999 by the european remote sensing ers 1 and ers 2 satellites the interferograms span periods of between 2 and 71 months wssfs are observed in the lisan peninsula and along the dead sea shores in a variety of appearances including circular and elongate coastal depressions a few hundred meters to a few kilometers in length depressions in ancient alluvial fans and depressions along salt diapir margins phase differences measured in our interferograms correspond to subsidence rates generally in the range of 0 20 mm yr within the studied period with exceptional high rates that exceed 60 mm yr in two specific regions during the study period the level of the dead sea and of the associated ground water has dropped by 6 m this water level drop within an aquifer overlying fine grained marly layers would be expected to have caused aquifer system consolidation resulting in gradual subsidence comparison of our insar observations with calculations of the expected consolidation shows that in areas where marl layers are known to compose part of the upper 30 m of the profile estimated consolidation settlements are of the order of the measured subsidence our observations also show that in certain locations subsidence appears to be structurally controlled by faults seaward landslides and salt domes gradual subsidence is unlikely to be directly related to the sinkholes excluding the use of the wssfs features as predictable precursors to sinkhole formation

mapping small elevation changes over large areas differential radar interferometry a technique that uses synthetic aperture radar sar images to measure very small 1 cm or less surface motions with good resolution 10 m over large swaths 50 km is presented along with experimental results the method could be used for accurate measurements of many geophysical phenomena including swelling and buckling in fault zones residual displacements from seismic events and prevolcanic swelling the method is based on sar interferometry where two images are made of a scene by simultaneously flying two physically separated antennas then the phases of corresponding pixels are differenced and altitude formation is deduced from some simple computation and image rectification it is also possible to use one antenna flown twice over the same scene then if the second flight exactly duplicates the track of the first an interesting possibility occurs there would be no phase changes between the images at all unless there was a physical change in the scene such as ground swelling that would alter the distance from some resolution element to the antenna since the phase changes all occur at the short carrier wavelength the basic limitation on sensitivity is only the phase noise in the system when the two imaging passes are made from flight tracks that are separated which is the case with the seasat images used here it is no longer possible to distinguish surface changes from the parallax caused by topography however with some additional computation a third image made at some other baseline may be used to remove the topography and leave only the surface changes this method was applied using seasat data to an imaging site in imperial valley california where motion effects were observed that were ascribed to the expansion of water absorbing clays phase change images of this area are shown along with associated ground truth about the presence of water problems with the technique are explored along with a discussion of future experimental possibilities on upcoming sar missions like earth observing system eos earth resources satellite ers 1 sir c and the venus imaging radar magellan

stress and strain tensors based on focal mechanisms in the seismotectonic framework of the friuli venezia giulia region northeastern italy the principal axes of stress and strain are inferred for the seismotectonic zones of the friuli venezia giulia region which forms the eastern part of the european southern alps this region corresponds to a polyphase deformational belt formed during the meso and neoalpine compressions from the eocene to plio quaternary several distinct seismotectonic zones are recognized by comparing seismological and tectonic characteristics inference of the stress and strain tensors is based on 243 fault plane solutions corresponding to earthquakes occurring between 1984 and 2001 magnitude range 2 1 5 6 the analysis reveals two main regional stress patterns a strike slip regime active in the eastern and northwestern parts of the area under study and dominant thrusting processes in the central and western zones the orientation of the maximum principal stress varies from north northwest south southeast to north northeast south southwest the stress magnitude ratio of the calculated stress tensors varies from 0 4 to 0 7 the orientation of the maximum shortening axis is generally north northwest south southeast changing to north northeast south southwest in the southeastern part of the region for most seismotectonic domains the inferred strain pattern is quite concordant with the surface tectonics the orientations of the principal axes of stress and strain are in most cases similar the complex regional tectonic structure consisting of two indented tectonic wedges appears to control the patterns of horizontal stress and strain

discrimination of geophysical phenomena in satellite radar interferograms various geophysical phenomena are recorded in the interference patterns formed by differencing two synthetic aperture radar sar images the fringes generated by the topographic relief can be removed using a digital elevation model dem the remaining fringes map the change in satellite to ground range which occurred between the acquisition times of the two images by comparing different pairs of images spanning different intervals of time it is possible to discriminate between geophysical signal and interferometric artifact here we apply this pair wise logic to the area around the 1992 landers california earthquake using sar images acquired by the ers 1 satellite the range varies with time as a constant step impulsive or sloping function examples of each type include a dem error an aftershock two atmospheric perturbations and postseismic afterslip respectively their signatures are identified and separated using the pair wise logic

geodetic airborne laser altimetry of breidamerkurjokull and skeidararjokull iceland and jakobshavns isbrae west greenland

surface displacement of the 17 may 1993 eureka valley california earthquake observed by sar interferometry satellite synthetic aperture radar sar interferometry shows that the magnitude 6 1 eureka valley earthquake of 17 may 1993 produced an elongated subsidence basin oriented north northwest parallel to the trend defined by the aftershock distribution whereas the source mechanism of the earthquake implies a north northeast striking normal fault the 3 millimeter accuracy of the radar observed displacement map over short spatial scales allowed identification of the main surface rupture associated with the event these observations suggest that the rupture began at depth and propagated diagonally upward and southward on a west dipping north northeast fault plane reactivating the largest escarpment in the saline range

paleoenvironmental events during the last 13 000 years in the central red sea as recorded by pteropoda a high resolution record was obtained by investigating a sedimentary sequence from two cores taken in the central red sea r v meteor cruise 5 leg 2 the numerical variations between nonmigratory and migratory pteropods and their stable isotopic record were studied together with variations in the carbonate and total organic carbon content in order to estimate changes in the structure of the water column during the last 13 kyr the results indicate the existence of a highly stratified water column during deglaciation and early holocene 13 8 5 ka during this period the depth of the mixed layer varied between less than 50 100 m at most and productivity was markedly reduced in comparison to the recent situation the intermediate and deep water were constantly highly depleted in oxygen a pronounced younger dryas event was recognized at 10 4 ka which coincides with an arid phase on the border land the oxygenation of the intermediate water improved remarkably after 7 5 ka and peaked during the period between 4 6 and 2 0 ka during this period the mixed layer reached its present depth and the productivity which was maximal during middle holocene attained present level during the last 4 6 kyr

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

holocene environment and subsistence patterns near the tree shelter red sea mountains egypt abstract the tree shelter site dates to the early to mid holocene 8000 to 4900 14c yr bp present conditions around the site are hyperarid but charcoal remains indicate less severe aridity at the time of its occupation the environment around the site then supported a rich wadi vegetation which allowed hunting during the epipaleolithic and herding during the neolithic occupation although more favorable than today the environmental conditions also displayed a desert character and seem to have limited the range of domestic herbivores introduced in the area

fault plane structure of the antofagasta chile earthquake of 1995 from a large dataset of aftershocks in the rupture area of the mw 8 0 1995 antofagasta earthquake we derived the spatial distribution of hypocenters and a b value map along the fault plane we further examined various focal mechanisms of the aftershock sequence the b value distribution on the fault plane clearly indicates the heterogeneity of the rupture area we found a positive correlation between the b value variations and the main shock source time function determined by delouis 1996 where zones of high b value are related to high slip with these results we propose to have found evidence for the segmentation of the fault plane and suggest that the mapped inhomogeneities could have played the role of asperities prior to the main shock rupture

an improved method for determining the regional stress tensor using earthquake focal mechanism data application to the san fernando earthquake sequence the orientations of fault planes and slip directions indicated by a population of earthquake focal mechanisms can be used to determine best fit regional principal stress directions and r 2 1 3 1 a measure of relative stress magnitudes under the assumption of uniform stress in the source region this analysis allows for the possibility that failure occurs on preexisting zones of weakness of any orientation in the inversion we perform a grid search of stress models to find the one which requires the smallest total rotation of all the fault planes that is needed to match the observed and predicted slip directions the method allows for errors in orientations of both the fault planes and slip directions we have an objective means for identifying the more likely of the two possible fault planes from each focal mechanism relative to a given stress model thus we do not face the problem of ambiguity of nodal planes which plagues other analyses of this kind by using a grid search of stress models rather than a linearization scheme we are able to perform a realistic error analysis and thus establish confidence limits for the preferred regional stresses the method can be used to investigate possible stress inhomogeneities during earthquake sequences by analyzing subsets of the data population the technique has been applied to 76 events from the san fernando earthquake sequence for which we have found best fit stresses plunge and azimuth 1 7 187 2 27 281 3 62 84 and r 0 65 the average misfit between this stress model and all the data is about 8 and all but eight of the aftershocks have misfits of less than 20 these values are considerably less than the uncertainty of the focal mechanism determinations therefore significant stress inhomogeneities are not required by the data our analysis does not support the suggestion of a change in stresses during the aftershock sequence as proposed by others on the basis of an apparent change in focal mechanisms

coseismic stress and strain field changes investigation through 3 d finite element modeling of dinsar and gps measurements and geological seismological data the l aquila italy 2009 earthquake case study

high frequency attenuation of shear waves in the southeastern alps and northern dinarides summary we investigated the high frequency attenuation of s waves in the southeastern alps and northern external dinarides using waveforms from 331 earthquakes 3 0 mw 6 5 the spectral decay parameter k was computed using 1345 three component high quality records collected by the italian strong motion network ran and by the short period seismometric network of northeastern italy nei in the period 1976 2007 weak motion data from 11 stations of the nei network and strong motion data collected by five accelerometers of the ran were analysed the k parameter was estimated in the 0 250 km distance range in a frequency band extending from the corner frequency of the event up to 25 or 45 hz using the amplitudeaccelerationfourierspectraofs waves theobservedrecord to recordvariabilityof k was modelled by applying a generalized inversion procedure using both parametric and nonparametric approaches our results evidence that k is independent on earthquake size while it shows both site and distance dependence stations of the nei network present the same increase of k with epicentral distance re and show values of the zero distance k parameter k0 s between 0 017 and 0 053 s for the whole region the k increase with distance can be describedthroughalinearmodelwithslopedk dre 1 4 0 1 10 4 skm 1 assumingan average s wave velocity 3 34 km s 1 between 5 and 15 km depth we estimate an average frequency independent quality factor qi 2140 for the corresponding crustal layer the non parametric approach evidences a weak positive concavity of the curve that describes the k increase withre at about 90 km distance this result can be approximated through a piecewise linear function with slopes of 1 0 10 4 and 1 7 10 4 sk m 1 in accordance with a three layers model where moving from the intermediate to the bottom layer both qi and decrease two regional dependences were found data from earthquakes located westward to the nei network evidence weaker attenuation properties probably because of s wave reflections from different parts of the moho discontinuity under the eastern po plain at about 25 30 km depth while earthquakes located eastward in western slovenia where the moho deepens up to 45 50 km evidence a higher attenuation moreover the k estimates obtained with data from earthquakes located in the area of the 1998 mw 5 7 and 2004 mw 5 2 kobarid events are 0 017 s higher than the values predicted for the whole region probably because of the high level of fracturing that characterizes fault zones the comparison between measured and theoretical values of k computed at a few stations with available s wave velocity profiles reveals that the major contribution to the total k0 s is due to the sedimentary column from surface to 800 m depth the hard rock section contribution is limited to 0 005 s in accordance with a maximum contribution of 0 010 s predicted by the non parametric inversion

topographic mapping from interferometric synthetic aperture radar observations interferometric synthetic aperture radar observations provide a means for obtaining high resolution topographic terrain maps from data acquired simultaneously at two slightly displaced antennas calculation of the three dimensional coordinates of all the points in a radar image can be made from the combination of along track slant range and interferometer fringe measurements thus the result compensates for the layover exhibited by conventional radar maps and removes the false targets generated by multiple signal paths to a given object in the scene we have derived a topographic map of a portion of the san francisco bay area utilizing data that were recorded by a radar system mounted on a nasa cv990 aircraft and processed by a general purpose digital computer this map displays the height above sea level of a region approximately 11 km by 10 km in size sampled on an 11 m pixel grid uncertainties in the estimated height result from imprecise knowledge of the observational geometry radar bandwidth limitations and finite signal to noise ratios for our system each factor contributed approximately 3 4 m to a relative rms error of about 6 m additional global errors of the order of 10 m can result from inaccurate monitoring of aircraft attitude the statistical variation of the height measurements from the ocean portion of the map which we can presume to be quite flat is 2 10 m rms which is consistent with the theoretical estimate comparison of our results with u s geological survey contour maps indicates a high degree of correlation between the two sets of altitude data

application of airborne lidar to mapping seismogenic faults in forested mountainous terrain southeastern alps slovenia results are presented of the first airborne lidar survey ever flown in europe for the purpose of mapping the surface expression of earthquake prone faults detailed topographic images derived from lidar data of the idrija and ravne strike slip faults in nw slovenia reveal geomorphological and structural features that shed light on the overall architecture and kinematic history of both fault systems the 1998 mw 5 6 and 2004 mw 5 2 ravne fault earthquakes and the historically devastating 1511 m 6 8 idrija earthquake indicate that both systems pose a serious seismic hazard in the region because both fault systems occur within forested terrain a tree removal algorithm was applied to the data the resulting images reveal surface scarps and tectonic landforms in unprecedented detail importantly two sites were discovered to be potentially suitable for fault trenching and palaeo seismological analysis this study highlights the potential contribution of lidar surveying in both low relief valley terrain and high relief mountainous terrain to a regional seismic hazard assessment programme geoscientists working in other tectonically active regions of the world where earthquake prone faults are obscured by forest cover would also benefit from lidar maps that have been processed to remove the canopy return and reveal the forest floor topography

karst landform development and related sediments in the miocene rocks of the red sea coastal zone egypt limestones and evaporites are the main rock types constituting the exposed middle miocene sediments of the red sea coastal zone between quseir and mersa alam these rocks represent typical conekarst and karst ridge landforms with minor surface and subsurface solution features

an experiment in systematic study of global seismicity centroid moment tensor solutions for 201 moderate and large earthquakes of 1981 data from the global digital seismograph network were used to obtain centroid moment tensor solutions using the method of dziewonski et al 1981 results were obtained for 201 earthquakes ranging in seismic moment from 7 1023 to 3 1027 dyne cm the wide dynamic range of the sro asro stations allows us to investigate using the same algorithm series of events among which the smallest and the largest may differ in moment by a factor as large as 1000 among the events studied is a particularly interesting series in january 1981 off the island of honshu the main shock was preceded by three foreshocks and followed by four aftershocks all falling within the range of our analysis there is an indication that the source mechanism changes with the size of the event statistical analysis of the results for all earthquakes reveals that the half duration of shallow and intermediate events is approximated by 1 6 10 8 m01 3 the shifts in origin time for deep focus earthquakes are indicative of the general complexity of these events which depends only weakly on the seismic moment the extreme departures from a double couple mechanism seem to depend both on the moment and on the focal depth while for shallow earthquakes these departures decrease from a maximum at about 1025 dyne cm with increasing moment the reverse appears to be true with respect to deep focus earthquakes shallow earthquakes north of new guinea and along the solomon islands show systematic and substantial departures from the double couple mechanism

insar observations of low slip rates on the major faults of western tibet two contrasting views of the active deformation of asia dominate the debate about how continents deform i the deformation is primarily localized on major faults separating crustal blocks or ii deformation is distributed throughout the continental lithosphere in the first model western tibet is being extruded eastward between the major faults bounding the region surface displacement measurements across the western tibetan plateau using satellite radar interferometry insar indicate that slip rates on the karakoram and altyn tagh faults are lower than would be expected for the extrusion model and suggest a significant amount of internal deformation in tibet

earthquake triggering inferred from rupture histories dinsar ground deformation and stress transfer modelling the case of central italy during august 2016 january 2017 on august 24 october 26 and 30 2016 central apennines italy were hit by three shallow normal faulting very strong earthquakes rupturing in an nw se striking zone event 3 norcia occurred between event 1 amatrice at the se and event 2 visso at the nw of the entire rupture zone the rupture histories of the three events as revealed by teleseismic p wave inversion showed that all were characterized by bilateral rupture process with stronger rupture directivity towards nw for events 1 and 3 and towards sse for event 2 maximum seismic slip of 1 2 0 8 and 1 4 m in the hypocenter and magnitude of m w 6 2 6 1 and 6 5 were calculated for the three events respectively dinsar measurements based on sentinel 1 and 2 satellite images showed ground deformation directivity from events 1 and 2 towards event 3 which is consistent with the rupture process directivity for events 1 2 and 3 the maximum ground subsidence was found equal to 0 2 0 15 and 0 35 m based on rupture directivity and ground deformation pattern we put forward the hypothesis that the area of the second event was stress loaded by the first one and that both the first and second earthquake events caused stress loading in the area where the third event ruptured coulomb stress transfer modelling yields strong evidence in favor of our hypothesis the stress in the fault plane of event 2 was increased by 0 19 bars due to loading from event 1 event 3 fault plane was loaded by an amount of 2 bars due to the combined stress transfer from the two previous events despite its proximity to the negative positive lobe boundary the three events produced combined stress loading of more than 0 5 bar along the apennines to the nw and se of the entire rupture zone in the se stress lobe a series of strong earthquakes of m w 5 3 5 6 and 5 7 occurred on january 18 2017 but likely seismic potential remains in the area we consider that in the nw and more extensive stress lobe the seismic potential has also elevated due to stress loading

global cmt analysis of moderate earthquakes mw 4 5 using intermediate period surface waves a new method for calculating centroid moment tensor cmt solutions for moderate sized earthquakes is presented and tested in the new algorithm which is a modification to the standard harvard cmt method intermediate period surface waves are included in the inversion for source parameters the dispersion of teleseismic surface waves in the period range 40 to 150 sec is predicted by interpolation of recent global phase velocity maps the method is tested on a set of 20 moderate and large 5 2 mw 7 2 earthquakes with known mechanisms the retrieved mechanisms are similar to the previous results even when noise is added to the seismograms to simulate earthquakes of a smaller magnitude mw 4 5 the inversion algorithm is applied to the 1993 klamath falls mainshock and aftershock sequence and the results compare well with earlier results a catalog of mw 4 5 focal mechanisms for greece and surrounding areas for the first six months of 1995 is derived using the new method of analysis

increasing seismicity in southern tibet following the 2015 mw 7 8 gorkha nepal earthquake abstract we conducted a systematic detection of micro seismicity in southern tibet 1 6 days before and 4 4 days after the 2015 mw 7 8 gorkha nepal earthquake our study employs 368 template events listed in the china earthquake networks center cenc catalog with the waveform based matched filter technique we detected five times more earthquakes than listed in the cenc catalog during our study period the seismicity in southern tibet shows a significant increase immediately following the gorkha nepal earthquake including two normal faulting events the mw 5 8 tingri and mw 5 3 nyalam earthquakes about 3 and 11 h after the mainshock respectively although the static stress changes cfs showed a slightly better correlation with the seismicity rate changes than the peak dynamic stress changes cfs t the absolute value of the static stress change at the epicenter region of the mw 5 8 tingri earthquake is 10 kpa roughly two orders smaller than the peak dynamic stress change of 2 2 mpa although we are unable to identify the primary triggering mechanism it is evident that the 2015 nepal earthquake triggered widespread seismicity in southern tibet our results highlight the potential increase of seismic hazard in southern tibet due to the occurrence of major thrust earthquakes along the himalaya frontal thrust faults

microtremor hvsr study for assessing site effects in the bovec basin nw slovenia related to 1998 mw5 6 and 2004 mw5 2 earthquakes abstract the bovec basin which is filled with glacial and fluvial sediments has recently been struck by two strong earthquakes 1998 and 2004 which caused extensive damage vii viii ems 98 strong site effects resulted in large variations in damage to buildings in the area which could not be explained by the surface variations in quaternary sediments the microtremor horizontal to vertical spectral ratio hvrs method was therefore applied to a 200 m dense grid of free field measurements to assess the fundamental frequency of the sediments large variations in the sediment frequency 3 22 hz were obtained with most of the observed values in the range 6 12 hz the observed frequencies cannot be related to the total thickness of quaternary sediments sand gravel but can be explained by the presence of conglomerate or lithified moraine at shallow depths the results were compared also with the velocity structure derived from seismic refraction data microtremor measurements performed in several two and some three and four storey houses masonry with rc floors which prevail in the bovec basin have shown that the main building frequencies in the area are in the range 7 11 hz this indicates that damage to houses in both earthquakes in some parts of the basin was enhanced by site amplification and soil structure resonance areas of possible soil structure resonance were identified in the settlements bovec brdo bovec mala vas cezsoca and kal koritnica considerable changes in fundamental frequencies within short distances were established in the town of bovec their values are as high as 22 hz in the central part of the town but diminish to 6 11 hz in the adjacent brdo and mala vas districts this is in agreement with the distribution of damage in both earthquakes which was considerably higher in brdo and mala vas although the houses in the central part of the town are older microtremor investigations have proved an effective tool for assessment of site effects in cases of complex geological structure commonly encountered in young alpine basins filled with glaciofluvial sediments which are partly cemented lithified layers can considerably change the fundamental frequency and consequently the site effects by taking additional measurements in buildings possible soil structure resonance can be identified