stress fields and fault reactivation angles of the 2000 western tottori aftershocks and the 2001 northern hyogo swarm in southwest japan abstract we estimated the stress fields of the aftershocks of the 2000 western tottori earthquake m w 6 6 and the northern hyogo swarm max m w 5 2 by a stress tensor inversion of moment tensor solutions reported from the national research institute for earth science and disaster prevention japan the maximum principal stress direction of the western tottori sequence was estimated as n107 e with a strike slip regime in the northern hyogo swarm the orientations of the principal stress directions could not be well constrained by the observed data but after examining the detailed characteristics of the solution we obtained a most probable solution of n113 e for the 1 direction these solutions are consistent with the maximum horizontal directions roughly estimated from the strike directions of large earthquakes occurring geographically between these two seismic activities we measured the angle between each fault slip direction and maximum principal stress direction to investigate the frictional properties of earthquakes the distribution of the angles was forward modeled to estimate the coefficient of friction and the stress ratio assuming uniformly distributed fault orientations for the western tottori sequence a homogeneous stress field with a coefficient of friction less than 0 4 was estimated a high stress level was also suggested because very little change occurred in the stress field during the mainshock for the northern hyogo sequence the coefficient of friction was estimated to be between 0 5 and 1 0

non double couple mechanism of moderate earthquakes occurred in lower siang region of arunachal himalaya evidence of factors affecting non dc moment tensor solutions of 104 earthquakes which were observed at local distances in lower siang region of arunachal himalaya have been estimated using isola code the magnitude range of analyzed earthquakes lies between 1 8 mw and 5 3 mw out of 104 earthquakes only 32 events are having good data the signal noise ratio of these 32 events is greater than 6 with magnitude greater than 2 5 all possible sources of non dc such as noise present in the data depth of the source low azimuthal coverage of the event and non dc as a part of real earthquake source process are examined the study reveals that non dc is highly dependent on the source depth as comparatively shallow events shows high clvd the clvd is also highly affected by the noise present in the data another factor is the magnitude of the event the high magnitude event shows quite high dc so the source mechanisms of high magnitude events are double couple dc

rupture process of the 2011 tohoku oki mega thrust earthquake m9 0 inverted from strong motion data 1 we investigate the rupture process of the m9 0 tohoku oki mega thrust earthquake using the relatively low frequency strong motion records 0 01 0 125 hz observed at 36 k net and kik net stations the epicentral distances of which range from 120 km to 400 km the fault model is a rectangular plane the length and width of which are 510 km along the japan trench and 210 km along subducting direction of the pacific plate respectively we perform the multi time window inversion analysis with a 30 30 km2 subfault the derived slip model has one large slip area this area extends from the region around the hypocenter to the shallow part of the fault plane and further to the north and south along the trench axis located far off southern iwate miyagi and northern fukushima prefectures the seismic moment is 4 42 1022 nm mw 9 0 and the maximum slip is 48 m the slips near the coast are relatively small except off miyagi prefecture which experienced a slip greater than 5 m the shallow large slip area which continuously ruptured from 60 s to 100 s after the initial break radiated seismic waves rich in very low frequency content 0 02 hz the rupture after 100 s propagating to the southern fault area contributes to the distinct phases observed for fukushima and ibaraki prefectures the relationship between the proposed rupture model and the feature of the acceleration waveforms is not straightforward and suggests the frequency dependency of the seismic wave radiation

detection of anomalous seismic phases by the wavelet transform summary strong motion data at la union one of three near fault stations of the michoacan mexico earthquake in 1985 are analysed by a wavelet transform in order to identify a clear later energy arrival whose frequency content and particle motion are quite different from the main part of the seismograms we used an orthonormal set of analysing wavelets a discrete wavelet transform proposed by meyer and yamada with which an efficient computational procedure can be achieved utilizing the fast fourier transform results of an application of the above wavelet transform to three component velocity data of la union are summarized as follows a vertical seismogram does not contain any distinguishable later energy arrivals for the entire frequency range recorded the major energy arrives in the time interval between 10 and 30 s in contrast an east west component seismogram shows a peculiar later arrival more than 10 s later than the main energy arrival and our wavelet analysis shows that this later phase is characterized by an arrival time of 38 s and a frequency range from 0 1 to 1 hz where the amplitude of the later phase is even larger than the main part this example clearly demonstrates the potential of wavelet transforms to identify objectively any phase in seismograms localized in both time and frequency from the information on its particle motion the above phase corresponds to a heterogeneous and delayed break of one stronger portion on a fault on which the rupture was very smooth or crack like elsewhere

seasonal diurnal and storm scale hydrochemical variations of typical epikarst springs in subtropical karst areas of sw china soil co2 and dilution effects summary two year continuous ph conductivity temperature and water stage of the two typical epikarst springs nongla spring and maolan spring about 200 km apart in subtropical karst areas of sw china were presented our primary study objective was to understand how karst systems respond hydrochemically to recharge at different time scales and what the biogeochemical processes and controlling factors in the sw china epikarst environment are a thermodynamic model was used to link the continuous data to monthly water quality data allowing the calculation of co 2 partial pressures and calcite dolomite saturation levels on a continuous basis marked seasonal diurnal and storm scale variations were observed for ph conductivity co 2 partial pressures and calcite dolomite saturation indexes of the springs indicating that both springs are dynamic and variable systems however the coefficients of variation of these hydrogeochemical features tends to be in the order of seasonal storm scale diurnal the seasonal and diurnal variations of these features higher conductivity and lower ph in summer and at daytime lower conductivity and higher ph in winter and at nighttime tend to co vary with temperature which influences the production of co 2 in soils thus being the driving force for the variations soil co 2 effect the storm scale fluctuations occur during the spring summer rainy days due to the storm events depending on the rainfall intensities however there are differences in magnitudes and direction of the variations of these features at very high rainfall intensity the dilution effect dominates the variations characterized by the decrease in both conductivity and calcite dolomite saturation of the springs while soil co 2 effect determines the variations at lower rainfall intensity characterized by increase in co 2 partial pressure and conductivity but decrease in ph and calcite dolomite saturation in a word the hydrodynamic aspects together with hydrobiogeochemical characteristics need to be taken into account to correctly explain the hydrochemical variations of the epikarst springs results from the study demonstrate the need to redesign hydrogeochemical sampling strategies for epikarst springs in karst areas with monsoon climate like sw china i e with remarkable seasonal matching fluctuations in temperature rainfall and vegetation

using stable isotopes to quantify water uptake by cyclobalanopsis glauca in typical clusters of karst peaks in china in this study stable isotopes 18o and 2h were used to determine the sources of water for cyclobalanopsis glauca in two habitats limestone outcrops and thin soils in clusters of karst peaks in southwest china where soils are scattered only in rock gaps and are underlain by rigid carbonate rocks we used a direct inference approach and the isosource mixing model to estimate the contributions of different sources to the plant xylem water the results showed that adult c glauca growing on limestone outcrops mainly used water from soils in rock gaps which comprised 65 of all water sources during the rainy season and water from rainwater sources during the rain dry season and dry season the proportion of deep water used increased during the dry season in contrast young c glauca growing on limestone outcrops relied on a mixture of rainwater and soil water during the rainy and the rain dry seasons and on rainwater in the dry season accounting for 66 3 and 64 0 of water use respectively adult c glauca on thin soils mainly used soil water in rainy seasons a mixture of soil water and rain water in the rain dry season and rainwater in the dry season water held within bedrock was essential for meeting plant transpiration requirements in karst peak cluster areas the results will provide knowledge for the effective protection of vulnerable karst environments and for the recovery of vegetation on karst rocky desertification areas

quantification of frequency dependent lengthening of seismic ground motion duration due to local geology applications to the volvi area greece many methods have been proposed through the last decades for the experimental estimation of site effects however these estimates have largely fo cused on the amplitude of motion and less attention has been given to duration the present study is an attempt to fill this gap through a comparison of the phase of the fourier spectrum at two nearby sites the method makes use of the frequency dependent mean group delay as proposed by sawada 1998 its application on weak and moderate motion recordings from the european test site near volvi greece yields stable and physically satisfactory results the soft sites inside the graben exhibit a consistent increase of the mean group delay which is maximum around the fun damental frequency of amplification while rock sites on either side of the graben have comparable spectra in terms of both modulus and phase a further comparison with results of 2d finite difference simulations provides qualitatively similar results the mean group delays are found however to be much smaller on numerical syn thetics than on observed records although the increase of duration for simple input signals is obvious by visual inspection this may offer a way to discriminate the existence of 2d or 3d effects at a given site finally this technique also allows construction of site specific time domain synthetics accounting for both the amplitude and phase modifications associated with site conditions the method requires how ever a good signal to noise ratio

laboratory investigation into off fault seismic activity abstract the off fault pattern of weak seismic activity which was observed in the laboratory around fault pairs with already generated tensile cracks led to the comparison with similar patterns observed in nature in some seismoactive regions on the basis of the results of the laboratory model experiments the off fault seismic activity can be attributed to fault segments oriented obliquely or roughly perpendicular to the main fault system these fault segments may have originated as tensile fractures during one of the foregoing strong earthquakes to study the off fault foreshock and aftershock occurrences a method of laboratory seismology physical modeling was employed the use of this method is based on the assumption that the obtained information on the seismic regime of fault models is relevant to the seismic manifestation of faults in the earth the results of laboratory experiments can thus be used to analyze the pattern of seismic energy release in selected seismoactive fault regions

a new strategy of finite fault inversion using multiscale waveforms and its application to the 2015 gorkha nepal earthquakefinite fault inversion using multiscale waveforms and its application to the 2015 gorkha earthquake

the 2000 tottori earthquake a shallow earthquake with no surface rupture and slip properties controlled by depth the m w 6 8 tottori earthquake japan does not exhibit any surface trace but was particularly well instrumented strong motion displacement records and gps coseismic data are used to constrain the evolution of the slip on the fault plane in time and space we adopt in this study a two plane fault geometry based on aftershock distributions and analysis of close station records in a first step our inversion allowed surface slip the model obtained has a significant surface slip which contradicts the absence of clear surface slip reported by geologists in a second step models with no slip at the surface buried faults compatible with geological observations have been tested the tests with different fault depths show that when slip is allowed to occur close to the surface the fit to seismological and geodetic data is increased these tests confirm that slip actually occurred at shallow depth despite the nonuniqueness of the solution all the inverted source models show 1 a large slip amplitude patch at a depth of about 4 5 km and 2 relatively small slip in the hypocentral area the rupture velocity is about 2750 m s in the asperity region the total rupture duration is about 8 s the slip distribution seems to be controlled by the variation of fault properties with depth another feature that could control the rupture of this earthquake is a fault plane almost perpendicular to the main fault nw of the epicenter which apparently inhibits further rupture propagation

inversion for parameters of tensile earthquakes the tensile source model generalizes the shear source model by assuming that the slip vector can be arbitrarily oriented with respect to the fault and is not constrained to lie within the fault plane the proposed inversion for the parameters of tensile sources is based on the evaluation of the isotropic iso compensated linear vector dipole clvd and double couple dc components in seismic moment tensors the most significant parameters inverted are the ratio at the fault denoted as the parameter and the inclination of the slip vector from the fault the parameter is significant for discriminating noisy moment tensors of shear earthquakes from those of tensile earthquakes the inclination can be accurately determined from the dc component in the moment tensor because the dc component rapidly decreases with increasing for example the inclination of 20 causes dc being 50 60 only the inversion is applied to earthquakes which occurred in january 1997 in west bohemia czech republic it is shown that some of these earthquakes display tensile faulting the parameter is 0 1 the inclination of the slip from the fault attains values of up to 20 this inclination is a result of tensile traction and reduced shear traction along the fault and high fluid pressure in the region

assessment of p and s wave energy radiated from very small shear tensile seismic events in a deep south african mine 1 we discuss requirements for reliable estimates of radiated seismic energy in s and p phases and derive ratios of s to p radiated energy es ep of 539 seismic events with local magnitudes 5 23 ml 2 41 subdecimeter size recorded by high frequency acoustic emission ae sensors of the jaguars seismic network in the mponeng deep gold mine south africa the analyzed events are aftershocks of a mw1 9 earthquake and the recording ae sensors are located within about 40 m of the events a shear tensile model is used to simulate the radiation pattern of p and s phases from a family of rupture models ranging from pure shear to pure tensile failure the calculations include correction factors for energy estimates associated with given source receiver geometries and expected focal mechanism with possible tensile component synthetic calculations are used to assess the effects of limited observed frequency band and attenuation on the estimated es ep ratios the model calculations provide guidelines on when different approximations may be used the obtained es ep ratios for the analyzed events are relatively low median value 5 for the full range of model parameters tested suggesting that significant number of the events display a tensile component events with very small ratios e g 1 may reflect enhanced p radiation associated with rock damage in the source volumes

kinematic source parameters for the 1989 loma prieta earthquake from the nonlinear inversion of accelerograms we describe a technique to infer the kinematic parameters of the earth quake rupture process by the nonlinear inversion of near source high frequency seis mic records the model assumes that each point on the fault plane slips when the rupture front passes with a variable slip amplitude for a given rupture model syn thetic seismograms are computed by using the ray theory and a plane layered velocity structure the rupture velocity and the final slip are specified at a set of control points on the fault plane and the values at any point on the fault are then obtained by a bicubic interpolation the final slip and rupture velocity at the fault grid nodes are determined by searching for the minimum of a misfit function by using the genetic algorithm the number of control points is progressively increased to move from a high to low wavelength description of final slip and rupture velocity on the fault plane the optimal model parameter set is chosen according to the minimum of the corrected akaike information criterion parameter the uncertainty on the source parameters has been estimated through the analysis of cross correlation of the misfit function in the neighborhood of the final best fit rupture model the method is applied to near source strong motion records of the 1989 loma prieta earthquake we find that the most earthquake slip occurred in two regions located northwest and southeast of the hypocenter consistent with previous models obtained using other data and techniques moreover we find that the rupture propagated faster toward the southeast than in the northwest direction the total duration of the rupture is found to be approximately 9 sec

intra ordovician deformation in southeast ireland evidence from the geological setting geochemical affinities and u pb zircon age of the croghan kinshelagh granite the croghan kinshelagh alkali granite intrudes a cleaved volcano sedimentary sequenceon the border of counties wicklow and wexford in southeast ireland u pb dating of zircons fromthe granite indicate a mid caradoc emplacement age of 454 1 ma the duncannon group hostrocks form the southwestern end of the avoca volcanic belt a mid ordovician caradoc sequenceof acid and intermediate lavas and volcaniclastics dolerite dykes intrude the granite elsewhere in theregion dolerites are generally associated with volcanic rocks the main dl deformation within theduncannon group rocks is manifest as a steep dl cleavage generally regarded as a product of latecaledonian regional deformation in southeast ireland the croghan kinshelagh granite showsstrong geochemical coherence with subalkaline varieties of the caradoc volcanic rocks relativelyhigh th y nb and ree contents set it apart from any other known granite type in southeastireland together with the geochemical evidence the age determination of 454 ma indicates that thecroghan kinshelagh granite was generated and emplaced during ordovician volcanism in southeastireland volcanism was closely followed by penetrative deformation and emplacement of the granite the intra ordovician deformation may have been a consequence of closure of the iapetus ocean ormore localized events such as accretion on the hanging wall of the subduction zone the age of thecroghan kinshelagh granite provides an important datum for ordovician volcanism and subductionin southeast ireland

estimation of high frequency wave radiation areas on the fault plane by the envelope inversion of acceleration seismograms we have developed an inversion method to estimate high frequency wave radiation areas on the fault plane it is very difficult to perform a source inversion for seismic waveforms whose frequencies are higher than 1 hz because of two problems one is the difficulty in obtaining green s functions that are accurate enough for such high frequencies and the other is that involved in doing a waveform inversion for such oscillatory data we overcame these problems by using aftershock records as empirical green s functions and by using the envelopes of acceleration seismograms as the inversion data instead of waveforms envelopes were calculated by smoothing the acceleration seismograms with a running root mean square time window we applied this method to the 1993 kushiro oki japan earthquake mw 7 6 which occurred on a horizontal fault plane inside the pacific plate subducting beneath the north american plate we adopted the mjma 4 9 aftershock as the empirical green s function event we bandpass filtered 2 0 10 0 hz the strong motion acceleration seismograms at three stations and calculated the envelopes by smoothing with a 5 0 s window length the 40 km 60 km fault plane was divided into 4 6 meshes and the acceleration radiation intensity and rupture time of each mesh were obtained by the inversion the results are as follows 1 high frequency waves radiated weakly around the rupture starting point but radiated mainly near the periphery of the fault plane an area with particularly strong radiation intensity of high frequency waves is seen at the edge of the fault plane about 30 km southwest of the rupture starting point its size is about 20 km 20 km 2 the distribution of high frequency radiation intensity and slip distribution are complementary to each other that is the radiation of high frequency waves was strong in those areas where that of low frequency waves was weak

automated full moment tensor inversion of coal mining induced seismicity seismicity induced by coal mining in the ruhr region germany has been monitored continuously over the last 25 yr in 2006 a dense temporary network hamnet was deployed to locally monitor seismicity induced by longwall mining close to the town of hamm between 2006 july and 2007 july more than 7000 events with magnitudes m l from 1 7 to 2 0 were detected the spatiotemporal distribution of seismicity shows high correlation with the mining activity in order to monitor rupture processes we set up an automated source inversion routine and successfully perform double couple and full moment tensor mt inversions for more than 1000 events with magnitudes above m l 0 5 the source inversion is based on a full waveform approach both in the frequency and in the time domain providing information about the centroid location focal mechanism scalar moment and full mt inversion results indicate a strong dominance of normal faulting focal mechanisms with a steeper plane and a subhorizontal one fault planes are oriented parallel to the mining stopes we classify the focal mechanisms based on their orientation and observe different frequency magnitude distributions for families of events with different focal mechanisms the overall frequency magnitude distribution is not fitting the gutenberg richter relation full mts indicate that non negligible opening tensile components accompanied normal faulting source mechanisms finally extended source models are investigated for largest events results suggest that the rupture processes mostly occurred along the subvertical planes

mapping of the high frequency source radiation for the loma prieta earthquake california waveform inversion has been successfully applied to map the spatial distribution of earthquake fault slip from strong motion records but its application has been restricted to a relatively lower frequency range of the data 5 hz generation is incoherent between neighboring patches on the fault we formulated an analytical model for calculating the envelope time history of the squared high frequency displacement seismogram this envelope time history is found through the line integration of the squared energy radiation intensity over the isochron using a recursive stochastic inversion scheme we determined both the lower frequency slip distributions from the low pass filtered strong motion displacement data and the higher frequency energy radiation intensity from the envelope of the squared high frequency displacement data on an extended fault for the 1989 loma prieta earthquake respectively our resulting lower frequency slip model shows that there are two main slip patches and little slip directly updip of the hypocenter one major slip zone located 10 km northwest of the hypocenter with predominant dip slip and the other located 12 km southeast of the hypocenter with predominant oblique slip our preliminary results of the high frequency energy radiation intensity inversion indicate three large high frequency sources and few smaller ones located on the outer periphery of the large slip zones this suggests that the high frequency energy sources are located along or near the boundaries of large slip zones which is consistent with the theoretical consideration that high frequencies are primarily generated from the rupture stopping areas or places with large slip variation

spatio temporal distribution of fault slip and high frequency radiation of the 2010 el mayor cucapah mexico earthquake 1 earthquake slip history and moment release are best resolved using long period seismic waves but details in the rupture process such as sharp changes in rupture velocity or direction can be imaged more clearly using higher frequency waves here we investigate the slip and the high frequency radiation histories of the 2010 el mayor cucapah baja california mexico earthquake mw 7 2 the slip distribution inferred from inversion of strong motion data between 0 02 and 0 25 hz indicates northwest propagating rupture followed by bilateral rupture for 40 s the sources of high frequency radiation between 0 3 and 2 hz inferred from back projection analysis using teleseismic data are adjacent to but not within the high slip patches from the finite slip model in time and space this implies relatively smooth rupture during the times and regions of maximum moment release as theoretical models have predicted high frequency radiation seems mostly associated with changes in rupture velocity or slip magnitude strong high frequency radiation is also found where the rupture propagated to a branch fault 50 km northwest of the hypocenter complementary constraints on both fault slip and high frequency radiation provide increased understanding of earthquake rupture mechanics and may help improve strong motion evaluation at high frequencies

a tensile shear crack model for the mechanism of volcanic earthquakes abstract temporary seismic observations were carried out for about 1 month at miyakejima island on the izu bonin arc after an eruption on october 3 1983 more than 3000 seismic events were observed and they are classified into 4 different categories short period earthquakes long period earthquakes isolated tremors and continuous tremors two active source regions of the short period earthquakes were located along the old caldera rim of the miyakejima volcano one region was very close to the eruptive fissures another was about 1 2 km northwest of the fissures almost all the earthquakes in the former region showed dilatant first motions of p waves at all the stations in the island on the other hand almost all events in the latter region showed compressive first motions of p waves at all the stations the first motions of p waves for these earthquakes cannot be explained by the quadrant type pattern due to a double couple force system nucleation of a tensile crack coupled with a shear crack a tensile shear crack model is proposed as a source mechanism of the short period earthquakes moment tensor elements of tensile and shear cracks have been determined by the least squares method using observed p and s wave data results suggest that tensile cracking opening or closing is dominant for generating those earthquakes in comparison with shear cracking the strikes of the tensile cracks for the earthquakes are shown to be nearly parallel to the strike of the fissures the earthquakes that occurred in the northwestern region of the fissures are considered to be generated by a sudden opening of tensile shear cracks due to the excess pressure of intrusive magma in contrast the earthquakes occurring beneath the fissures are probably generated by a sudden closing of tensile shear cracks and this suggests that the magmatic pressure under the fissures rapidly decreased after the eruption moment tensor analysis of the tensile shear crack model in this study demonstrates the non double couple source mechanism for volcanic earthquakes related to magmatic activity

stress and the direction of slip on fault planes the shear stress direction on a fault plane depends only on four of the six components of the stress tensor assuming only that the slip direction marks the shear stress direction on any fault plane and that stress is homogeneous it is possible to estimate these four stress parameters from populations of fault planes with known slip directions as several workers have observed different formulations of the problem may yield varying best fitting stresses and estimates of uncertainty in the simplest case no assumptions are made regarding the orientations of fault planes relative to the stress tensor thus the technique allows for the possibility that the fault planes may be very weak here we present simple analytical and graphical descriptions of the field of admissible fault geometries relative to any four parameter stress model which can be used to illustrate the significance of various inverse strategies in particular this paper explores the effects of using two alternative measures of misfit between an observed fault datum and stress model 1 the pole rotation the angle between the observed and predicted slip direction on the observed fault plane and 2 the minimum rotation the smallest angle between the observed fault geometry and any fault geometry which is consistent with the model by allowing for variation of the fault plane as well as the slip vector the minimum rotation procedure generally achieves a more stable and presumably realistic estimate of the actual discrepancy between a fault observation and stress model than the pole rotation procedure in a test case using 17 earthquake focal mechanisms from the yuii region of eastern taiwan separate inversions based on the two misfit criteria yield different optimum stress models and uncertainty estimates additional constraints on the stress tensor such as the effect of friction can be superimposed on the ones used here

full moment tensor inversion as a practical tool in case of discrimination of tectonic and anthropogenic seismicity in poland tectonic seismicity in poland is sparse the biggest event was located near my lenice in 17th century of magnitude 5 6 on the other hand the anthropogenic seismicity is one of the highest in europe related for example to underground mining in upper silesian coal basin uscb and legnica glogow copper district lgcd open pit mining in belchatow brown coal mine and reservoir impoundment of czorsztyn artificial lake the level of seismic activity in these areas varies from tens to thousands of events per year focal mechanism and full moment tensor mt decomposition allow for deeper understanding of the seismogenic process leading to tectonic induced and triggered seismic events the non dc components of moment tensors are considered as an indicator of the induced seismicity in this work the mt inversion and decomposition is proved to be a robust tool for unveiling collapse type events as well as the other induced events in polish underground mining areas the robustness and limitations of the presented method is exemplified by synthetic tests and by analyzing weak tectonic earthquakes the spurious non dc components of full mt solutions due to the noise and poor focal coverage are discussed the results of the mt inversions of the human related and tectonic earthquakes from poland indicate this method as a useful part of the tectonic and anthropogenic seismicity discrimination workflow

data dependent non double couple components of shallow earthquake source mechanisms effects of waveform inversion instability seismic moment tensors are routinely determined for global earthquakes using waveform inversions and the resulting double couple and non double couple characteristics are extensively used in tectonic analyses for shallow events several moment tensor components are intrinsically poorly resolved especially for surface wave inversions which can lead to artificial non double couple components or can obscure actual non double couple components in the source representations the relatively greater instability of surface wave inversions can cause differences between inversions based on only body waves and joint inversions of body and surface waves the harvard cmt catalog exhibits systematic variations in non double couple components with seismic moment which can be attributed to use of only body waves in inversions for small events and combined body and surface waves for large events systematic behavior of non double couple components with regional strain environment is significantly less dependent on seismic moment when solutions influenced by less stable surface waves are omitted

broadband seismic wave radiation process of the 2000 western tottori japan earthquake revealed from wavelet domain inversion 1 we develop a new inversion method to obtain the low and high frequency wave radiation processes whose border is 1 hz in this method we adopt a consecutive approach to evaluate the fitness between the observed and synthetic strong motions and to synthesize the waveforms a new feature of our inversion is an evaluation of the fitness of broadband strong motions including the high frequency range using the wavelet coefficient of velocity waveforms based on the frequency dependent characteristics of seismic waves another new feature is the introduction into the source inversion of a hybrid green s function which is constructed from theoretical and empirical green s functions for the low and high frequency ranges respectively in order to reach the global minimum by nonlinear inversion we introduce a multiscale approach for the low frequency inversion after a synthetic test the inversion method was applied to the 2000 western tottori earthquake for three frequency bands the low frequency inversion 0 0625 1 hz reveals that the asperity extends from the southeast of the hypocenter to the shallow part of the fault above the hypocenter the waves of 1 2 hz are radiated most intensely from the rupture starting area of the southeast asperity on the other hand the higher frequency waves of 2 4 hz are radiated most strongly from the edge of the southeast asperity the inversion result suggests a possibility that broadband strong motions are generated from the asperities and the high frequency wave radiations are particularly related to the initiation and termination of the asperity rupture

joint seismological magnetotelluric investigation of shallow and implosive non dc and dc earthquakes beneath the gravitationally unstable heisei shinzan lava dome unzen volcano japan abstract shallow implosive non double couple ndc earthquakes have been detected beneath unzen volcano japan by a routinely operated seismometer network here we analyze the waveforms from 14 temporary seismic stations around mt fugen fugendake and heisei shinzan lava dome which formed during the 1990 1995 eruptions to further investigate this shallow seismicity we also estimate the subsurface electrical resistivity structure using broadband magnetotelluric observations and investigate its relationship to the shallow seismicity we find that 1 implosive ndc earthquakes occur at the craters that were active during the 1990 1991 eruptions which are currently buried by the approximately 200 m thick heisei shinzan lava dome 2 the detected ndc earthquakes generally possess downward p wave arrivals although upward p wave arrivals are observed at a few seismic stations 3 the tensile axes of the ndc earthquakes show various slip directions 4 repeated ndc earthquakes are in some cases detected within 20 s of the initial event and 5 a high resistivity zone exists beneath the ndc earthquakes we conclude that the implosive ndc earthquakes were generated by the collapse of small randomly oriented vapor filled voids at the two buried craters with active volcanic conduits still present beneath these craters the shallow dc earthquakes consist of two clusters that are located 2 3 km below the ndc earthquakes the focal mechanisms of the shallower cluster approximately 2 km depth indicate various fault mechanism whereas those of the deeper cluster approximately 3 km depth indicate strike slip faulting the top of the shallower cluster corresponds to the base of the conductive zone which suggests that the dc earthquakes in the shallower cluster are generated in a zone of high pore pressure that is capped by a hydrothermally altered clay layer

water source partitioning among trees growing on carbonate rock in a subtropical region of guangxi china it is not clear how the water sources are used by trees in typical karst areas of guangxi china trees growing on rigid carbonate rock can primarily use spring water precipitation recharged soil water or a mixture of the two in this study the nongla karst dynamic monitoring station in the southwest of guangxi china was observed to determine the water sources accessed by trees growing on rigid carbonate rock seasonal change of isotope ratios 18o and d in twig sap soil water rainfall and spring water were measured stem water samples plotted to the right of the meteoric water line indicates utilization of water sources subject to evaporative isotopic enrichment trees growing on rigid carbonate rock in the southwest of china used rainfall directly in the rainy season adult trees tended to use deeper water stored in the epikarst zone while the young ones used soil water when precipitation decreased in the dry season all trees sampled depend mostly on water stored in the epikarst zone spring water was the major water source for all of the tree species investigated in the dry season in conclusion these data indicate that trees growing on rigid carbonate rock in southwest china depend mostly on water stored in the epikarst zone therefore water storage in the epikarst zone is the essential water source for trees growing on carbonate rock in southwest china

resolution of non double couple components in the seismic moment tensor using regional networks i a synthetic case study summary we perform a detailed synthetic study on the resolution of non double couple non dc com ponents in the seismic moment tensors from short period data observed at regional networks designed typically for monitoring aftershock sequences of large earthquakes in addition we test two different inversion approaches a linear full moment tensor inversion and a non linear moment tensor inversion constrained to a shear tensile source model the inversions are applied to synthetic first motion p and s wave amplitudes which mimic seismic observa tions of aftershocks of the 1999 mw 7 4 izmit earthquake in northwestern turkey adopting a shear tensile source model to analyse the resolution capability for the obtained non dc components inverted we contaminate synthetic amplitudes with random noise and incorporate realistic uncertainties in the velocity model as well as in the hypocentre locations we find that the constrained moment tensor inversion yields significantly smaller errors in the non dc components than the full moment tensor inversion in particular the errors in the compensated linear vector dipole clvd component are reduced if the constrained inversion is applied furthermore we show that including the s wave amplitudes in addition to p wave amplitudes into the inversion helps to obtain reliable non dc components for the studied station config urations the resolution remains limited due to the lack of stations with epicentral distances less than 15km assuming realistic noise in waveform data and uncertainties in the velocity model the errors in the non dc components are as high as 15 percent for the isotropic and clvd components respectively thus being non negligible in most applications however the orientation of p and t axes is well determined even when errors in the modelling procedure are high

resolution of non double couple components in the seismic moment tensor using regional networks ii application to aftershocks of the 1999 mw 7 4 izmit earthquake summary we study potential non double couple non dc components in aftershocks of the 1999 izmit earthquake the izmit earthquake ruptured a 140 km long segment of the north anatolian fault zone in northwestern turkey and was followed by the mw 7 1 d uzce earthquake that extended the rupture further to the east focal mechanisms of izmit aftershocks clearly indicate a segmentation of the rupture into several segments one of which is the akyazi plain a pull apart structure where significant non dc components might be observed the analysedearthquakecataloguecontainswaveformsofmorethan4000accuratelylocatedevents observedat35three componentshort periodseismicstations toensurehigh qualitydatawith good focal coverage we apply strict quality criteria to the aftershock catalogue reducing the number of events to only 33 aftershocks for which stable moment tensors were calculated using p and s wave amplitudes the moment tensors of the 33 analysed aftershocks display significant differences in the percentage of the non dc components for the three distinct fault segments the izmit sapanca karadere d uzce and the akyazi segments events located in the izmit sapanca and karadere d uzce segments exhibit only small percentages of the non dc components and if existent they are mainly positive this correlates well with the predominant strike slip stress regime along these segment and also with the main shock rupture being rightlateral strike slip in contrary we found a substantial percentage of non dc components for events below the akyazi plain where the sapanca fault splits into the mudurnu and karadere faults there the observed non dc components are entirely positive indicating a tensional regime and ranging from 20 to 48 percent clearly exceeding the defined error bounds found in a synthetic study this observation is in accordance with the post seismic setting following the izmit main shock that left a remarkable slip deficit of 3 5 m below the akyazi bend

isotopic dating in metamorphic belts isotopic dating in metamorphic rocks is concerned with the timing of processes whose operation is controlled by continually changing physical conditions of these temperature has a pervasive influence and the use of physical models to elucidate the ways in which temperature is likely to vary is briefly reviewed the central concept of closure temperature is critically discussed and quantitative estimates for biotite and hornblende are evaluated in order to illustrate the factors which control closure temperatures and limit their application in practice the possibility of dating crystallization using minerals which crystallize below their respective closure temperatures is examined taking examples involving k ar rb sr sm nd and u pb analyses the indirect dating of metamorphism via structurally dated plutons is briefly considered and the problems of interpreting both discordant u pb zircon ages and rb sr whole rock isochrons in metamorphosed granites are discussed the value of near concordant zircon ages is emphasized the extent of isotopic equilibration during metamorphism specifically of sr isotopes in metasediments is shown not to be a simple function of metamorphic grade the flow of fluids produced by metamorphic reactions appears to be crucial and there is a potential for dating metamorphism using whole rock samples where such flow can he demonstrated independently the concluding discussion briefly examines existing data for the dalradian and indicates the potential for further progress using both well established and novel approaches

further testing of the bedding plane slip model for hydraulic fracture opening using moment tensor inversions abstractmoment tensors are calculated by using the p wave first motion peak amplitudes of 59 microseismic events with high signal to noise ratio these events are from a surface microseismic data set gathered during hydraulic fracture stimulation of the marcellus gas shale in washington county pennsylvania usa the majority of these 59 events have a horizontal nodal plane a few degrees characteristic of a dip slip horizontal slip moment tensor if the horizontal nodal plane is an auxiliary the vertical nodal plane has a pure dip slip motion which is inconsistent with the opening motion for vertical hydraulic fractures that enables proppant loading this points to slip on horizontal nodal planes with the auxiliary vertical nodal planes aligned with the local maximum horizontal stress orientation as indicated by drilling induced fractures in nearby vertical wells these 59 microseismic events are caused by slip on horizontal mechanical discontinuities such as bedding planes during the opening of ver

low temperature thermal history of eastern ireland effects of fluid flow abstract a reconnaissance apatite fission track study was undertaken in eastern ireland to evaluate the low temperature thermal history of palaeozoic basement rocks outcropping adjacent to the irish sea basin on a sampling transect across the lapetus suture zone the distributions of single grain ages and track lengths indicate cooling after maximum palaeotemperatures of between 80 and 100 110 c at various times during the early tertiary about 30 45 ma although a significant component of tertiary uplift and erosion is inferred in eastern ireland from geological observations maximum palaeotemperatures are interpreted as principally due to heat advection by gravity driven groundwater flow following early tertiary uplift at about 60 ma this phase of fluid flow produced the localized remagnetization of the palaeozoic basement and overlying carboniferous limestones in north co dublin limited sampling in eastern ireland indicates extreme local heterogeneity in apatite age also characteristic of apatite fission track results from northern england thus heterogeneity requires an annealing control independent of the sample s thermal history suggested to be the individual crystal uranium content and indirectly the effects of fluid flow

stress tensor inversion using detailed microearthquake information and stability constraints application to olfus in southwest iceland using detailed microearthquake data we present a stress tensor inversion scheme with new methods for selecting the fault planes and allowing for errors in the focal mechanisms the nonuniqueness of earthquake focal mechanisms is accounted for in our inversion scheme through the introduction into the inversion of a range of well fitting focal mechanisms for each event the range of focal mechanisms significantly improves the quality of the estimated stress tensor relative localization of clusters of microearthquakes is used to obtain information about which nodal plane could be correct fault plane the clusters frequently fall on a common fault plane and if there are acceptable focal mechanisms where one nodal plane has orientation similar to the common plane we assume this is the correct fault plane for the event if there is no predefined fault plane we utilize a simple mohr coloumb failure criterion to obtain a physical choice of fault plane between the two nodal planes in the focal mechanism the nodal plane with highest relative instability is chosen as the fault plane differences between the instability and the standard slip angle criterion are investigated the new inversion scheme has been applied to microearthquake data from the olfus area in the vicinity of the southwest iceland triple junction we estimate an oblique strike slip state of stress maximum horizontal stress at n30 e and minimum horizontal stress at n60 w with significant normal faulting influence the instability fault selection criterion predicts very well the orientation of faults mapped by relative localization

isotopic u pb ages of zircon and monazite from the leinster granite southeast ireland a more precise age for the synkinematic emplacement of the large s type leinster batholith southeast ireland has been obtained by u pb dating of zircon and monazite separates from the two main granite varieties of the northern pluton a concordant age of 405 2 ma derived from monazite is considered to reflect both the age of intrusion and the main regional deformation event d1 in southeast ireland the monazite age is in good agreement with an earlier less precise whole rock rb sr isochron determination the zircon data indicate recent pb loss effects and the existence of a small component of inherited radiogenic pb derived from a crustal precursor during the generation of the batholith

a new nonlinear finite fault inversion with three dimensional green s functions application to the 1989 loma prieta california earthquake 1 we present a new procedure to invert for kinematic source parameters on a finite fault on the basis of the reciprocity relation of the green s functions we use a newly developed fourth order viscoelastic finite difference algorithm to calculate three dimensional 3 d green s functions actually the tractions on the fault we invert the data for the unknown source parameters at the nodes or corners of the subfaults the source parameters within a subfault area are allowed to vary this variation is calculated through bilinear interpolation of the four nodal quantities we have developed a global nonlinear inversion algorithm that is based on simulated annealing methods to solve efficiently for the nodal parameters we apply this method to the 1989 loma prieta california m 6 9 earthquake for both a 1 d and 3 d velocity structure we show 1 the bilinear interpolation technique reduces the dependence of inversion results on the subfault size by naturally including the effects of nearby subfaults 2 while the number of synthetic seismograms that must be computed is greatly increased by the bilinear interpolation the structure of the inversion method minimizes the actual numbers of computations 3 as expected complexity in the velocity structure is mapped into the source parameters that describe the rupture process there are significant differences between faulting models derived from 1 d and 3 d structural models

source characterization for broadband ground motion simulation kinematic heterogeneous source model and strong motion generation area we estimate strong motion generation areas that reproduce near source ground motions in a broadband frequency range 0 2 10 hz using the empirical green s function technique the strong motion generation areas are defined as extended areas with relatively large slip velocities within a total rupture area four m 6 class the 1997 kagoshima on march and may 1997 yamaguchi and 1998 iwate and several moderate size earthquakes in japan were analyzed we examine the relationship between the strong motion generation area and the area of asperities which is characterized based on heterogeneous slip distributions estimated from low frequency 1 hz waveform inversions somerville et al 1999 we performed waveform fitting in acceleration velocity and displacement then obtained the strong motion generation area occupying about a quarter of the total rupture area the size and position of the strong motion generation area coincide with those of characterized asperities we find self similar scaling of seismic moment to both the size of the strong motion generation area and the rise time for a magnitude range of analyzed earthquakes based on our results we propose a characterized source model for the broadband ground motion simulation which consists of strong motion generation areas with large slip velocities and a background slip area with a small slip velocity waveform modeling of the characterized source model suggests that the strong motion generation areas play important roles in simulating broadband ground motions and have the potential to be an about 10 mpa stress release area on the fault manuscript received 22 august 2002

cryptic sr and nd isotopic variation across the leinster granite southeast ireland rb sr isotope whole rock data from the end caledonian leinster batholith define an errorchron age of 464 26 ma appreciably older than the accepted emplacement age of c 405 ma this anomalously old age is the consequence of a highly variable initial sr isotopic composition initial nd ratios and t dm model ages also show a wide range of values however these isotopic variations are neither randomly distributed nor related to petrographic changes but instead reflect in a simple way geographic position about the axis of the batholith the isotopic pattern revealed in the leinster batholith means that isochron ages obtained from s type granites may be largely dependent on the sampling scheme adopted the variable isotopic composition of the granite most likely resulted from either a heterogeneous metasedimentary source or hybridization of coeval dominantly crustal melts

fault slip and rupture velocity inversion by isochrone backprojection summary a new technique is proposed here for the retrieval of slip images from the backprojection of high frequency displacement records when direct s waves are seen to be dominant in the near source data green functions can be approximated by the far field terms as described by ray theory assuming that the slip rapidly reaches the final value i e short slip duration the measured displacement can be ascribed to the slip contributions lying on the corresponding isochrone on the fault plane here we use the far field representation theorem to backproject on the fault plane the displacement amplitudes measured along the seismogram through the weighted stack of amplitude maps obtained from different stations we recover high slip zones on the fault the resolution analysis of the backprojected images is realized with spike tests that we refer to as image green functions which revealed to be an useful tool for detecting and locating artificial distortions of high slip patches due to a poor data coverage however when the slip is uniformly spread along the isochrones energy is scattered everywhere on the fault leading to defocusing effects on the final images a partial deconvolution technique is proposed by reiterating the backprojection an important implication of this study is that slip maps can be obtained as functions of the rupture time on the fault that is the method can be used to retrieve variable rupture velocity kinematic models since the latter parameter is not known a priori we suggest that a data set of coupled rupture velocity and slip maps is built up and the optimal model is chosen according to a waveform fitness criterion this procedure allows the slip inversion to be separated from the rupture velocity inversion significantly reducing the number of parameters to be estimated additionally the parametrization of the rupture velocity is done on a less dense grid than the slip by way of example the technique is applied to estimation of the kinematic rupture model of the 2000 tottori earthquake m 6 8 based on the inversion of near source strong motion data

stress breakdown time and slip weakening distance inferred from slip velocity functions on earthquake faults we estimate the critical slip weakening distance on earthquake faults by using a new approach which is independent of the estimate of fracture energy or radiated seismic energy the approach is to find a physically based relation between the breakdown time of shear stress tb the time of peak slip velocity tpv and the slip weakening distance dc from the time histories of shear stress slip and slip velocity at each point on the fault which can be obtained from dynamic rupture calculations using a simple slip weakening friction law numerical calculations are carried out for a dynamic shear crack propagating either spontaneously or at a fixed rupture velocity on a vertical fault located in a 3d half space and a more realistic horizontally layered structure with finite difference schemes the results show that tpv is well correlated with tb for faults even with a heterogeneous stress drop dis tribution except at locations near strong barriers and the fault edges we also inves tigate this relation for different types of slip weakening behavior we have applied the method to two recent strike slip earthquakes in western japan the 2000 tottori and the 1995 kobe events we integrated the slip velocity functions on the vertical fault obtained from kinematic waveform inversion of strong motion and teleseismic records from the arrival time of rupture tr to the time of the peak slip velocity tpv and we then corrected the slip obtained at tpv for the errors expected from the dynamic calculations it was found that the slip weakening dis tance d c estimated in the frequency window between 0 05 and 0 5 hz ranges between 40 and 90 cm on the two earthquake faults however if we consider the limited frequency resolution of the observed waveforms probable time errors in the slip velocity functions obtained from kinematic inversion and the uncertainty of the slip weakening behavior the above estimates may be those located between the minimum resolvable limit and the upper bound of their real values the estimated dc values do not necessarily seem to indicate larger values in the shallower part and smaller values in the deeper part of the fault but rather a spatially heterogeneous distribution that appears to be dependent on the local maximum slip this possible dependence might be interpreted by the frictional properties of the fault such as the degree of roughness or the thickness of gouge layers in addition to stress heterogeneities

vertical seismic profile synthetics by dynamic ray tracing in laterally varying layered anisotropic structures dynamic ray tracing drt is important in evaluating high frequency seismic wave fields in complicated structures two formulations of the drt equations for inhomogeneous anisotropic media are presented one of them is represented by the classical drt system suggested by cerven 15 years ago both systems are specified in cartesian coordinates the drt equations are supplemented with formulae for the transformation of drt across a smoothly curved interface between two inhomogeneous anisotropic media cerven s formulation of the drt is applied to the computation of vertical seismic profile vsp synthetics the results of drt are used for the evaluation of the geometrical spreading and of the coefficients of the paraxial ray approximation for travel times and ray amplitudes in addition the drt is also used in the interval ray tracing procedure a procedure searching for rays starling from the source and terminating in a specified interval on a profile results of numerical modeling of vsp measurements in a three dimensional laterally varying structure consisting of isotropic and anisotropic layers separated by curved interfaces are presented ray diagrams of selected elementary waves time distance curves and multisource three component vsp synthetics generated for two different source locations calculated for the anisotropic model are compared with the results determined for a reference isotropic model the latter is obtained by averaging phase velocities of the anisotropic model this comparison clearly shows the effects of anisotropy and the lateral variation of the model on seismic wave fields the reliability of the ray synthetics is briefly discussed

the matter of size on the moment magnitude of microseismic events abstractwe investigated the method of estimating seismic moment and moment magnitude for microseismic events we determined that the m0t defined by bowers and hudson is the proper scalar moment to be used in microseismic studies for characterizing the size of an event and calculating its moment magnitude for non double couple sources the proportional relationship between body wave amplitude and seismic moment in the brune model breaks down so under such situations the brune model is not an appropriate way to estimate the seismic moment and magnitude moreover the s wave alone is not sufficient for determining the total seismic moment instead the p wave must be analyzed an example barnett shale data set was studied and the results concluded that the magnitudes estimated with the brune model could be off by as much as 1 92 with an absolute average of 0 35 the moment magnitudes based on the scalar moment m0t also gave a significantly different event size distribution and b value estimation finall

detection of high frequency tensile vibrations of a fault during shear rupturing observations from the 2008 west bohemia swarm summary the analysis of 12 earthquakes of magnitudes between 1 7 and 3 7 that occurred in 2008 in west bohemia czech republic reveals that shear rupturing along a fault is accompanied by weak tensile vibrations of the fault the vibrations are of a narrow frequency band with frequencies distinctly higher than those of shear rupturing the tensile vibrations decay slowly in time and often resemble resonant waves they complicate the radiated p waveforms and the p wave radiation pattern the tensile vibrations can be observed in waveforms in directions near the nodal lines where the dominance of shear faulting radiation is lost the tensile vibrations are probably generated by opening of the fault during shear rupturing or by creating a wing tensile crack at the tip of the fault when shear fracturing stops

bayesian imaging of the 2000 western tottori japan earthquake through fitting of strong motion and gps data summary we image the rupture process of the 2000 western tottori earthquake m w 6 6 through fitting of strong motion and gps data we consider an observational network consisting of 18 strong motion and 16 gps stations located within three fault lengths from the epicentre we assume a planar fault and compute green s functions for a 1 d velocity model the earthquake rupture is described as a shear dislocation parameterized in terms of peak slip velocity rake angle rupture time and rise time defined on a regular grid of nodes on the fault surface and derived at inner points through bilinear interpolation our inversion procedure is based on a bayesian approach the solution of the inverse problem is stated in terms of a posterior probability density function pdf representing the conjunction of prior information with information contained in the data and in the physical law relating model parameters with data inferences on model parameters are thus expressed in terms of posterior marginal pdfs due to the non linearity of the problem we use a markov chain monte carlo mcmc method based on the metropolis algorithm to compute posterior marginals except for a few cases posterior marginals do not show a gaussian like distribution this prevents us from providing a mean model and from characterizing uncertainties in terms of standard deviations only resolution on each single parameter is analysed by looking at the difference between prior and posterior marginal pdfs posterior marginals indicate that the best resolved feature is a major slip patch peak value of 311 140 cm located between the hypocentre and the top edge of the fault centered at a depth of 4 5 km this shallow slip patch is triggered about 3 s after the earthquake nucleated and required about 4 s to reach its final slip value the presence of this shallow slip patch is common to all previous studies in contrast to some previous studies we do not identify any significant slip 1 m at the bottom of the fault we also compare inferences from both strong motion and gps data with inferences derived from strong motion data only in both cases the shallow slip patch is identified at other locations the main effect of the gps data is in reducing the probability associated with high values of slip gps data reduce the presence of spurious fault slip and therefore strongly influence the resulting final seismic moment

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

seismogram envelope inversion for the spatial distribution of high frequency energy radiation from the earthquake fault application to the 1994 far east off sanriku earthquake japan incoherency of high frequency seismic waves leads to the idea to analyze seismogram envelopes disregarding phase information for the source study we develop an inversion method for estimating high frequency above 1 hz energy radiation from the earthquake fault and site amplification factors from observed mean square s wave seismogram envelopes the inversion is executed by using the s wave envelope green function from the onset to coda for a point shear dislocation source in a scattering medium which is formulated based on an extended version of the radiative transfer theory the use of the envelope green function enables us to estimate the spatial distribution of high frequency energy radiation on a fault plane this has been difficult by conventional waveform inversion methods the rupture velocity and the duration time of energy radiation on each subfault are also estimated by grid search method we apply this new method to the 1994 far east off sanriku northeastern japan earthquake mw 7 7 which ruptured a 90 km segment of the plate boundary along the japan trench inverting observed seismogram envelopes at 10 strong motion stations in japan it is concluded that above 90 of the high frequency energy was radiated from the western half of the fault with the largest energy radiation near the deep side edge the rupture velocity is estimated to be 2 7 km s the estimated site amplification factors ranging between 0 3 and 15 are consistent with those independently estimated by the coda normalization method

rupture mechanism and interface separation in foam rubber models of earthquakes a possible solution to the heat flow paradox and the paradox of large overthrusts abstract spontaneous stick slip along the interface between stressed foam rubber blocks is a simple analog of earthquake rupture and stick slip results from this model are used to elucidate the role of normal stress variations along the interface in the stick slip process observations indicate significant normal interface vibrations and separation during slip suggesting that dynamic changes in normal stress rather than a drop in the coefficient of friction may control stick slip as suggested for example by tolstoi oden and martins and brune and co workers observations of particle trajectories indicate that stick slip shear motion is associated with various degrees of fault separation for an asymmetric model the motion is consistent with slipping motion of the type suggested by schallamach and price for a symmetric model the motion is similar to that suggested by comninou and dundurs if interface waves of this type involving separation during slip occur in earthquakes they may be a solution to the heat flow paradox since a major part of the slip occurs during separation and during low normal stress thus frictional heat generation is reduced normal interface vibrations during stick slip may explain the high corner frequency of p wave spectra and the generally high levels of p wave spectra beyond the corner frequency schallamach comninou type waves are consistent with the partial stress drop abrupt locking self healing models of brune and heaton

characteristics of subevents and three stage rupture processes of the 2015 mw 7 8 gorkha nepal earthquake from multiple array back projection abstract on 25 april 2015 an mw 7 8 earthquake occurred in nepal and caused about 9000 casualties this earthquake ruptured part of the main himalaya thrust fault which is due to the convergence of the subducting indian plate to the overriding eurasian plate and showed thrust mechanism with a very small fault dip angle about 7 10 we apply teleseismic multiple array back projection analysis to study the rupture process of this earthquake and find 6 clear high frequency radiation sources subevents our results illustrate a simple unilateral eastward rupture of 160 km with relative stable rupture speed of 2 8 km s and a duration of 56 s the entire rupture processes can be divided into 3 stages the high frequency radiation appears to be mainly located at the edge of the large slip area but the subevents have different characteristics in the western and eastern rupture areas for this 2015 nepal earthquake the scales of asperities appear to be mainly controlled by depth which dominates the overall patterns of slip and high frequency radiation we finally propose a multiple scale asperity model with stress and structural heterogeneities along the rupture direction to explain the distribution of high frequency subevents co seismic slip and aftershocks

along dip variation in seismic radiation of the 2011 ibaraki oki japan earthquake m w 7 9 inferred using a multiple period band source inversion approach

a global search inversion for earthquake kinematic rupture history application to the 2000 western tottori japan earthquake 1 we present a two stage nonlinear technique to invert strong motions records and geodetic data to retrieve the rupture history of an earthquake on a finite fault to account for the actual rupture complexity the fault parameters are spatially variable peak slip velocity slip direction rupture time and risetime the unknown parameters are given at the nodes of the subfaults whereas the parameters within a subfault are allowed to vary through a bilinear interpolation of the nodal values the forward modeling is performed with a discrete wave number technique whose green s functions include the complete response of the vertically varying earth structure during the first stage an algorithm based on the heat bath simulated annealing generates an ensemble of models that efficiently sample the good data fitting regions of parameter space in the second stage appraisal the algorithm performs a statistical analysis of the model ensemble and computes a weighted mean model and its standard deviation this technique rather than simply looking at the best model extracts the most stable features of the earthquake rupture that are consistent with the data and gives an estimate of the variability of each model parameter we present some synthetic tests to show the effectiveness of the method and its robustness to uncertainty of the adopted crustal model finally we apply this inverse technique to the well recorded 2000 western tottori japan earthquake mw 6 6 we confirm that the rupture process is characterized by large slip 3 4 m at very shallow depths but differently from previous studies we imaged a new slip patch 2 2 5 m located deeper between 14 and 18 km depth

non double couple microearthquakes in the focal area of the 2000 western tottori earthquake m 7 3 via hyperdense seismic observations

non double couple earthquakes 1 theory historically most quantitative seismological analyses have been based on the assumption that earth quakes are caused by shear faulting for which the equiv alent force system in an isotropic medium is a pair of force couples with no net torque a double couple or dc observations of increasing quality and coverage however now resolve departures from the dc model for many earthquakes and find some earthquakes especially in volcanic and geothermal areas that have strongly non dc mechanisms understanding non dc earth quakes is important both for studying the process of faulting in detail and for identifying nonshear faulting processes that apparently occur in some earthquakes this paper summarizes the theory of moment tensor expansions of equivalent force systems and analyzes many possible physical non dc earthquake processes contrary to long standing assumption sources within the earth can sometimes have net force and torque components described by first rank and asymmetric sec ond rank moment tensors which must be included in analyses of landslides and some volcanic phenomena non dc processes that lead to conventional symmetric second rank moment tensors include geometrically complex shear faulting tensile faulting shear faulting in an anisotropic medium shear faulting in a heteroge neous region e g near an interface and polymorphic phase transformations undoubtedly many non dc earthquake processes remain to be discovered progress will be facilitated by experimental studies that use wave amplitudes amplitude ratios and complete waveforms in addition to wave polarities and thus avoid arbitrary assumptions such as the absence of volume changes or the temporal similarity of different moment tensor com ponents

petrogenesis of the granitic donkerhuk batholith in the damara belt of namibia protracted syntectonic short range crustal magma transfer the areally extensive 5000 km2 syn tectonic ca 520 ma mainly s type donkerhuk batholith was constructed through injection of thousands of mainly sheet like magma pulses over 20 25 myr it intruded schists of the southern zone accretionary prism in the damara belt of namibia each magma pulse had at least partly crystallised prior to the arrival of the following batch however much of the batholith may have remained partially molten for long periods close to the h2o saturated granite solidus the batholith shows extreme variation in chemistry while having limited mineralogical variation and seems to be the world s most heterogeneous granitic mass the nd model ages of 2 ga suggest that eburnean rocks of the former magmatic arc structurally overlain by the accretionary wedge are the most probable magma sources crustal melting was initiated by mantle heat flux probably introduced by thermal diffusion rather than magma advection the granitic magmas were transferred from source to sink with minimal intermediate storage the whole process having occurred in the middle crust resulting in feeble crustal differentiation despite the huge volume of silicic magma generated source heterogeneity controlled variation in the magmas and neither mixing nor fractionation was prominent however due to the transpressional emplacement regime local filter pressing formed highly silicic liquids as well as felsic cumulate rocks the case of the donkerhuk batholith demonstrates that emplacement level tectonics can significantly influence compositional evolution of very large syn tectonic magma bodies

crustal anisotropy from local observations of shear wave splitting in west bohemia czech republic abstract the results of a systematic study of shear wave splitting observed in the three component digital seismograms of about 400 local microearthquakes that occurred during the 1985 1986 west bohemian earthquake swarm are presented two shear phases polarized nearly perpendicularly in horizontal projection were observed at all five stations of the local seismic network for most of the events the polarization of the faster shear wave is aligned in the wnw ese direction regardless of the mechanism and hypocenter location of the individual events and coincides with the direction of the maximum horizontal compressive tectonic stress in the region these effects are interpreted in terms of effective anisotropy of the upper crust in the region the maximum delay time between the split shear waves is 0 15 sec and corresponds to 6 anisotropy directional variation of the delay time was observed at the nearest station epicentral distance 5 km this variation was compared with functions predicted by theoretical models of cracked media to resolve which model is the most appropriate for crustal anisotropy surprisingly no agreement could be found for hudson9s model of dry or water filled parallel cracks that is widely used by many authors a successful fit was obtained for schoenberg douma9s model of a medium with parallel fractures the fracture normal pointed n31 e and the optimum fracture parameters were e n 0 4 and e t 0 02 the theoretically calculated fractures are aligned parallel to the tectonic stress direction and do not correspond to any real tectonic lines in the region

non double couple mechanisms of microearthquakes induced by hydraulic fracturing 1 we have inverted polarity and amplitude information of representative microearthquakes to investigate source mechanisms of seismicity induced by hydraulic fracturing in the carthage cotton valley east texas gas field with vertical arrays of four and eight three component geophones in two monitoring wells respectively we were able to reliably determine source mechanisms of the strongest events with the best signal to noise ratio our analysis indicates predominantly non double couple source mechanisms with positive volumetric component consistent with opening cracks oriented close to expected hydraulic fracture orientation our observations suggest the induced events are directly the result of opening cracks by fluid injection in contrast to many previous studies where the seismicity is interpreted to be primarily shearing caused by pore pressure diffusion into the surrounding rock or associated with shear stresses created at the hydraulic fracture tip

source model of the 1995 hyogo ken nanbu earthquake and simulation of near source ground motion the 1995 hyogo ken nanbu earthquake struck the heavily populated kobe and adjacent cities in western japan more than 6400 people were killed and more than 150 000 buildings were destroyed the characteristics of mainshock ground motions in the heavily damaged area are needed to understand how buildings and bridges performed and why they reached failure unfortunately very few strong ground motions were recorded in the heavily damaged area during the mainshock in this study we attempt to estimate mainshock ground motions by using the em pirical green s function method egf method first we assume an initial source model with the asperities based on the rupture process obtained by inversion of strong ground motion records for simplicity we consider each asperity as a sub event with uniform stress drop in a finite extent then the initial model was improved by matching the synthetic and observed ground motions using a trial and error pro cedure the final model consists of three subevents subevent 1 with stress drop of 163 bars under the akashi strait around the rupture starting point subevent 2 with stress drop of 86 bars under the nojima fault in awaji island and subevent 3 with stress drop of 86 bars under kobe finally we estimate strong ground motions using aftershock records at sites where the mainshock was not recorded the near source motions in kobe synthesized with the best fit model are characterized by two large pulses with a duration of 1 to 3 sec the pulses are caused by forward rupture directivity effects from subevents 1 and 3 peak horizontal acceleration and velocity of the synthesized motions at the heavily damaged sites are about 1000 cm sec 2 and 130 crrdsec respectively while those at a rock site in the near source region are about 300 crrdsec 2 and 60 cm sec

high resolution study on the hydrochemical variations caused by the dilution of precipitation in the epikarst spring an example spring of landiantang at nongla mashan china in addition to rainfall high resolution measurements of water level ph specific conductivity and temperature of landiantang epikarst spring at nongla mashan county in guangxi province china were recorded in summer rainy season by using a data logger with time interval of fifteen minutes water from the spring issues along a karst conduit during the rainstorms in summer it was found that the ph and temperature of landiantang spring increased while its specific conductivity decreased as hco3 ca2 and mg2 are the dominant ions linear relationships between concentrations of those ions and specific conductivity were developed according to the ion concentrations from the linear relationships the saturation indexes of calcite sic the saturation indexes of dolomite sid and co2 partial pressure log text p text co text 2 of the spring were calculated results indicated that the log text p text co text 2 of the spring during the rainstorms was lower than that without rain and its sic and sid was also lower combined with the characteristics of the epikarst zone it was inferred that the above results were caused by the dilution of rainwater because overland flow with high ph due to neutralization of carbonate rock dusts in the air to rainwater and low specific conductivity traveling through the conduit rapidly during rainstorms showed greater influences on the hydrochemical variations of the epikarst spring

regional patterns of tectonic stress in europe nearly 1500 stress orientation determinations are now available for europe the data come from earthquake focal mechanisms overcoring measurements well bore breakouts hydraulic fracturing measurements and young fault slip studies and sample the stress field from the surface to seismogenic depths three distinct regional patterns of maximum compressive horizontal stress shmax orientation can be defined from these data a consistent nw to nnw shmax stress orientation in western europe a wnw ese shmax orientation in scandinavia similar to western europe but with a larger variability of shmax orientations and a consistent e w shmax orientation and n s extension in the aegean sea and western anatolia the different stress fields can be attributed to plate driving forces acting on the boundaries of the eurasian plate locally modified by lithospheric properties in different regions on average the orientation of maximum stress in western europe is subparallel to the direction of relative plate motion between africa and europe and is rotated 17 clockwise from the direction of absolute plate motion the uniformly oriented stress field in western europe coincides with thin to medium lithospheric thickness approximately 50 90 km and high heat flow values 80 m w m2 in western europe a predominance of strike slip focal mechanisms implies that the intermediate principal stress is vertical the more irregular horizontal stress orientations in scandinavia coincide with thick continental lithosphere 110 170 km and low heat flow 50 m w m2 the cold thick lithosphere in this region may result in lower mean stresses associated with far field tectonic forces and allow the stress field to be more easily perturbed by local effects such as deglaciation flexure and topography the stress field of the aegean sea and western anatolia is consistent with n s extension in a back arc setting behind the hellenic trench subduction zone the stress field is influenced in places by regional geologic structures e g in the western alps where shmax directions show a slight tendency toward a radial stress pattern not all major geologic structures however appear to affect the shmax orientation e g in the vicinity of the rhine rift system horizontal stress orientations are continuous

non double couple earthquake mechanisms at the hengill grensdalur volcanic complex southwest iceland the hengill grensdalur area in iceland generates frequent small non double couple earthquakes with explosive volumetric components we collected high quality three component digital recordings of 4 000 earthquakes on a purpose designed 32 station network in 1991 and determined focal mechanisms for 100 of the best recorded earthquakes by inverting amplitude ratios many of the mechanisms are consistent within the errors with simultaneous shear and tensile faulting with tensile faults parallel to the local spreading ridge and shear faulting similar to that in the south iceland transform fault zone some events cannot be explained by this model however and require other processes such as crack closing and partial compensation of tensile cracks by fluid flow

source description of the 1999 hector mine california earthquake part ii complexity of slip history we present a rupture model of the hector mine earthquake m 7 1 determined from the joint inversion of strong motion records p and sh teleseismic body waves global positioning system gps displacement vectors and measured surface offset we solve for variable local slip rake angle rise time and rupture velocity of a finite fault model involving multiple segments the inversion methodology developed in a companion article ji et al 2002 combines a wavelet transform approach with a nonlinear simulated annealing algorithm the final model is checked by forward simulating the interferometric synthetic aperture radar insar data our estimation to the seismic moment is 6 28 10 19 n m which is distributed along three segments from north to south releasing 37 41 and 22 of the total moment respectively the average slip is 1 5 m with peak amplitudes as high as 7 m the fault rupture has an average rise time of 3 5 sec and a relatively slow average rupture velocity 1 9 km sec resulting in a 14 sec rupture propagation history our approach permits large variation in rupture velocity and rise time and indicates that rise time appears to be roughly proportional to slip and shorter rise times are associated with the initiation of asperity rupture we also find evidence for nearly simultaneous rupture of the two northern branches

hengill triple junction sw iceland 1 tectonic structure and the spatial and temporal distribution of local earthquakes the hengill area is an unstable ridge ridge transform triple junction in sw iceland it contains the active central volcano hengill associated with the present accretionary zone and the extinct grensdalur central volcano associated with an accretionary zone that became inactive at about 0 7 m y when the locus of spreading migrated about 5 km w to the hengill zone the dominant tectonic trend of the area is n25 e parallel to the accretionary zones but transverse tectonic topographic features have also developed in the neighborhood of the two central volcanoes these result from local modification of the regional stress field associated with the spreading by radially symmetric stress fields associated with the volcanoes and the migration of volcanism a double high temperature geothermal system mirrors the double volcanic system the transform branch of the triple junction is represented by an ew striking zone of historic destructive earthquakes in the s of the area a seismological study was conducted with the aims of studying the tectonic structure and evaluating the passive seismic method as a geothermal prospecting tool the seismicity may be broadly divided into two groups first infrequent intense episodes of crustal movement occur that are associated with the release of tectonic stress along the plate boundary second continuous small magnitude activity occurs on a day to day basis this activity is mostly associated with the extinct grensdalur central volcano not the present plate boundary statistically significant temporal variations in b accompanied a swarm in the transform zone the continuous small magnitude activity may be geothermal in origin releasing thermal stress and not associated with plate boundary tectonics

field validation of isotopic procedures for determining sources of water used by plants in a semi arid environment abstract methods for using stable isotopes of water 2 h 18 o for determining the sources of water transpired by plants in a semi arid field situation are validated a comparison of the isotopic composition of the soil water in zones of high soil water potential and hence high plant water availability with that in plants shows that the overall approach is subject to a randomly distributed error of 5 in 2 h isotopic composition with no indication of any bias this includes errors involved in the extraction of water from plants and soil in spatial heterogeneity in soil profiles in heterogeneity within plant canopies in the time of travel of water through the plant and in assumptions about fractionation of isotopes during water uptake by plants these errors are generally smaller than natural variations of isotope thus allowing the isotopic method to be used similarly an estimate for the error in 18 o is is 1 a compartmental model was used to quantify errors associated with an inversion model using isotopic data of water coming from two soil layers the error in the estimation of the fraction of water taken from each compartment was 20 for many hydrological purposes this error is acceptable this is the first study estimating the errors associated with the method