simulation of accelerograms peak ground accelerations and mmi for the tecoman earthquake of 21 january 2003 abstract the tecoman mexico earthquake 21 january 2003 20 06 shows directivity in the area in which it spread the colima graben the presence of soft soils and the location of 8 out of 10 major urban zones in the area are important factors concerning the acceleration peak ground acceleration pga and modified mercalli intensity mmi caused by this earthquake data are not available due to the lack of instrumentation in the area in this paper we simulate acceleration time histories whose main contribution is to reflect a model that considers the source the path and the site effects in order to reach this objective we used the source model generated by ramirez gaytan and aguirre 2008 for the tecoman earthquake the pga and mmi were estimated from the waveforms in 25 points within the state of colima and eight more outside thus the maximum accelerations obtained are compared with four different ground motion prediction equations gmpes our results show an expected and reasonable behavior in agreement with the considerations of each one of the statistical methods compared in the end we generated an isoseismal map for the region this map is overlaid by the isoseismal map for this earthquake generated by other authors who used traditional methods to determine mmi first we conclude that the empirical green s function method can be successfully applied to simulate the acceleration waveforms in sites without instrumentation during the mainshock second the simulated records can be successfully used in seismic risk studies

short period source model of the 2011 mw 9 0 off the pacific coast of tohoku earthquake we have constructed a short period source model for the 2011 m w 9 0 off the pacific coast of tohoku earthquake using strong motion records at stations near the source fault the observed strong motions contain five wavepackets that correspond to specific strong motion generation areas smgas the origins of the wavepackets were retrieved from the original seismograms using a semblance analysis we determine the locations of the smgas based on sources extracted from the corresponding wavepackets the short period source model consists of five smgas smga1 5 which are located west of the hypocenter and along the down dip edge of the source fault smga1 is located in the miyagi oki source region west of the hypocenter smga2 in the middle sanriku oki source region north of the hypocenter and smga3 in the southern sanriku oki source region west of the hypocenter smga4 and smga5 are located near the down dip edge of the mainshock source fault extending from offshore fukushima prefecture to offshore ibaraki prefecture at some stations near the source fault impulsive waves are also seen on the recorded seismograms ground motions corresponding to these impulsive waves cannot be accounted for using the conventional uniform smga model we attempt instead to simulate the observed ground motions at the onagawa nuclear power plant at a depth of 128 m very near the source fault using a heterogeneous source model the impulsive waves are well simulated using the heterogeneous model with higher stress parameters within a small subarea inside the smgas

morphometric analysis of a subtropical andean basin tucuman argentina a morphometric analysis was done to determine the drainage characteristics of lules river basin using land sat imageries and topographical maps this catchment was divided into seven sub basins for the analysis liquimayo hoyada cienaga de las tablas siambon potrerillo and san javier yungas ecoregion covers almost all the watershed the drainage patterns of the sub basins are dendritic and parallel the basin includes seventh order stream and lower streams order mostly dominate the basin the development of stream segments is affected by slope and local relief the mean bifurcation ratio indicates that the drainage pattern is not much influenced by geological structures the shape parameters also reveal the elongation of the basin and sub basins

sensitivity of prestack depth migration to the velocity model to get a correct earth image from seismic data acquired over complex structures it is essential to use prestack depth migration a necessary condition for obtaining a correct image is that the prestack depth migration is done with an accurate velocity model in cases where we need to use prestack depth migration determination of such a model using conventional methods does not give satisfactory results thus new iterative methods for velocity model determination have been developed the convergence of these methods can be accelerated by defining constraints on the model in such a way that the method only looks for those components of the true earth velocity field that influence the migrated image in order to determine these components the sensitivity of the prestack depth migration result to the velocity model is examined using a complex synthetic data set the marmousi data set for which the exact model is known the images obtained with increasingly smoothed versions of the true model are compared

correction to source processes of the 1978 and 2005 miyagi oki japan earthquakes repeated rupture of asperities over successive large earthquakes 1 highly similar seismograms commonly observed along transform or convergent plate boundaries indicate that repeated small to moderate earthquakes occur within a single area the results of source process inversions for seismic events within the northeastern japan subduction zone suggest that large earthquakes and their component asperities also exhibit this repeating nature under certain conditions however sets of similar seismograms that might provide direct evidence of the repeated rupture of large earthquake asperities have not been observed this paper analyzes two offshore earthquakes near miyagi prefecture japan the most recent occurring in 2005 with a jma magnitude m of 7 2 in the source region of the 1978 earthquake m7 4 we demonstrate the similarity in waveforms from the seismograms recorded during the 1978 and 2005 earthquakes the early portions of the 2005 seismograms resemble the 1978 seismograms suggesting that the asperities located close to the 1978 hypocenter ruptured again during the 2005 event the seismogram similarities provide the first direct evidence for the repeated rupture of asperities during successive large earthquakes the results of our waveform inversions further indicate that the two asperities of the 2005 event largely coincide with the southern two asperities of the 1978 event these repeating asperities are recorded in the early portions of the 2005 seismograms with 60 of the amplitude recorded in the 1978 seismograms the characteristic behavior of the asperities supports the slip predictable recurrence model of earthquake rupture rather than the time predictable recurrence model

morphometric analysis of colanguil river basin and flash flood hazard san juan argentina this work analyzes various morphometric characteristics of the colanguil river basin in order to evaluate flash flood hazards such high water events pose a risk to the similarly named small village located at the basin s foot area for this purpose the basin is divided into seven sub basins and some basic measurements surface perimeter basin length river beds elevations and slope of the main river bed and of a number of minor river beds are calculated these measurements permit to predict approximately the behavior of the basin in the presence of a series of theoretical rainstorms that may generate unusual runoff volumes that make up such flash floods

morphometric and landsliding analyses in chain domain the roccella basin ne sicily italy the dynamic interaction of endogenic and exogenic processes in active geodynamic context leads to the deterioration of the physico mechanical characteristics of the rocks inducing slopes instability in such context the morphometric parameters and the analysis of landslide distribution contribute to appraise the evolutive state of hydrographic basins the aim of the study is the morphometric characterization of the roccella torrent basin rtb located in south italy landsliding and tectonic structure dynamically interact with the drainage pattern that records these effects and permits the definition of the evolutive geomorphic stage of the basin the air photograph investigation and field surveys permitted to draw the main geomorphic features the drainage pattern of the rtb to calculate the morphometric parameters and to delimit the landslides bodies detailed analysis about the landslide distribution within a test site 17 km2 wide were carried out to elaborate indicative indexes of the landslides type and to single out the lithotypes that are more involved in slope instability phenomena the morphometric parameters indicate the rejuvenation state within the rtb where the stream reaches show the effects of increased energy relief in agreement with the geological settings of this sector of the apennine maghrebian chain

broadband ground motion simulation of the 2004 and 1977 vrancea romania earthquakes using empirical green s function method we estimated the parameters of strong motion generation areas and simulated broadband ground motions for the moderate october 27 2004 m w 5 8 and damaging march 4 1977 m w 7 4 vrancea romania intermediate depth subduction earthquakes using the empirical green s function method the method allows the simulation of ground motions in a broadband frequency range by summing up the subevent records corresponding to small magnitude events in the near source areas which are assumed to follow the source scaling relationship and the omega square source spectral model we first estimated the strong motion generation area that reproduces near source ground motions in a broadband frequency range of 0 3 10 hz for the 2004 earthquake by fitting the synthetic acceleration velocity and displacement waveforms to the observed data the source properties of the obtained strong motion generation area are in agreement with the predictions made using an empirical source scaling relationship for crustal earthquakes implying a stress drop of approximately 10 mpa for the 2004 earthquake we then modeled the strong motion generation area for the 1977 damaging earthquake using the 2004 earthquake as an empirical green s function and constructing a source model based on its estimated source parameters to simulate the unique record at bucharest capital city of romania the rupture was assumed to have propagated from the northeast bottom of the strong motion generation area having a stress drop of 50 mpa broadband ground motion simulations were further compared in terms of the modified mercalli intensity values calculated from the peak ground accelerations and peak ground velocities of synthetic waveforms with the observed medvedev sponheuer karnik intensity values our estimates of the source properties for the 2004 and 1977 vrancea intermediate depth earthquakes support the size dependent stress drop

characterized source model for simulating strong ground motions during the 2008 wenchuan earthquake extremely valuable strong motion records during the 2008 wenchuan earthquake were obtained at a number of stations close to the source region we estimate the characterized source model for simulating ground motions using the empirical green s function egf method and the hybrid method using strong motion data from the earthquake the characterized source model consists of several asperities with large slip in the entire rupture area of the earthquake the locations of the asperities that generate strong motions were determined from the timing of pulse arrivals in observed records near the source fault because aftershock records of the earthquake had not been released yet observed records from an aftershock m w 4 9 of the 2008 iwate miyagi nairiku earthquake m w 6 9 which occurred in the shallow inland crust of the northeastern region in japan are used as substitutes for the egfs the synthetic motions obtained by the egf method agree well with the observed records with respect to acceleration and velocity waveforms in the period range of less than 2 s broader band strong motions are simulated by the hybrid method which combines the numerical method for periods longer than 2 s with the egf method for periods shorter than 2 s the best fit source model was obtained with stress drop on each asperity of approximately 13 mpa the ground motions numerically simulated at the bajiao station sfb near an asperity and in the forward rupture direction show directivity effects that are too strong in comparison with the observed motions we examined the influence of rupture velocity fluctuation on the synthetic waveforms in the forward rupture direction near the asperity finding that the forward directivity effects decrease with increase in velocity variances

source parameters of intermediate depth vrancea romania earthquakes from empirical green s functions modeling abstract several source parameters source dimensions slip particle velocity static and dynamic stress drop are determined for the moderate size october 27th 2004 mw 5 8 and the large august 30th 1986 mw 7 1 and march 4th 1977 mw 7 4 vrancea romania intermediate depth earthquakes for this purpose the empirical green s functions method of irikura e g irikura k 1983 semi empirical estimation of strong ground motions during large earthquakes bull dis prev res inst kyoto univ 33 part 2 no 298 63 104 irikura k 1986 prediction of strong acceleration motions using empirical green s function in proceedings of the 7th japan earthquake engineering symposium 151 156 irikura k 1999 techniques for the simulation of strong ground motion and deterministic seismic hazard analysis in proceedings of the advanced study course seismotectonic and microzonation techniques in earthquake engineering integrated training in earthquake risk reduction practices kefallinia 453 554 is used to generate synthetic time series from recordings of smaller events with 4 mw 5 in order to estimate several parameters characterizing the so called strong motion generation area which is defined as an extended area with homogeneous slip and rise time and for crustal earthquakes corresponds to an asperity of about 100 bar stress release miyake h t iwata and k irikura 2003 source characterization for broadband ground motion simulation kinematic heterogeneous source model and strong motion generation area bull seism soc am 93 2531 2545 the parameters are obtained by acceleration envelope and displacement waveform inversion for the 2004 and 1986 events and msk intensity pattern inversion for the 1977 event using a genetic algorithm the strong motion recordings of the analyzed vrancea earthquakes as well as the msk intensity pattern of the 1977 earthquake can be well reproduced using relatively small strong motion generation areas which corresponds to small asperities with high stress drops 300 1200 bar and high particle velocities 3 5 m s these results imply a very efficient high frequency radiation which has to be taken into account for strong ground motion prediction and indicate that the intermediate depth vrancea earthquakes are inherently different from crustal events

anisotropy parameter inversion in vertical axis of symmetry media using diffractions diffractions play a vital role in seismic processing as they can be utilized for high resolution imaging applications and analysis of subsurface medium properties like velocity they are particularly valuable for anisotropic media as they inherently possess a wide range of dips necessary to resolve the angular dependence of velocity however until recently the focus of diffraction imaging or inversion algorithms have been only on the isotropic approximation of the subsurface using diffracted waves we develop a framework to invert for the effective model this effective model is obtained through scanning over possible effective values and selecting the one that best fits the observed moveout curve for each diffractor location the obtained effective model is then converted to an interval model using a dix type inversion formula the inversion methodology holds the potential to reconstruct the true model with sufficiently high accuracy and resolution properties however it relies on an accurate estimation of diffractor locations which in turn requires good knowledge of the background velocity model we test the effectiveness and applicability of our method on the vertical transverse isotropic marmousi model the inversion results yield a reasonable match even for the complex marmousi model

morphometric characterization of the carrizal basin applied to the evaluation of flash floods hazard san juan argentina the carrizal river basin is located to the northwest of san juan province in the iglesia department one of the main geological hazards that affect the iglesia department is flash floods produced by heavy seasonal rains characterized by their high velocities and destructive power the carrizal river basin was selected as a test case to evaluate the potential magnitude of flash floods in relation to their associated hazard level this paper evaluates some of the hydrological aspects of a torrential regime of carrizal basin that can cause severe damage like the event that took place in the area during february 1944 various morphometric characteristics of the carrizal river basin were analysed in order to evaluate its flash ood hazard for this purpose the basin was divided into five sub basins according to lithological aspects and some basic measurements surface perimeter basin length river beds elevations and slope of the main river bed and of a number of minor river beds were calculated these measurements allowed predicting approximately the behaviour of the basin in the presence of a series of theoretical rainstorms that may generate unusual runoff volumes the predicted flash floods were compared against the carrizal flash flood

drainage morphometry of himalayan glacio fluvial basin india hydrologic and neotectonic implications morphometric analysis being widely used to assess the drainage characteristics of the river basins has been found to be a useful tool to delineate the glacial till covered overburden material as well as to identify areas prone to flash floods in present studies a number of parameters including the stream frequency drainage density and drainage texture suggest that the unconsolidated unstratified and highly permeable glacially deposited overburden till material facilitates the infiltration of snowmelt and rainwater in the pindari glacio fluvial basin eastern kumaun himalaya india likewise other till overburden covered glacial and proglacial areas of higher himalayan regions have been contributing to the groundwater budget the shape parameters further suggest that the sub basins with higher form factor are more prone to flash floods besides this the anomalies in the morphometric parameters have been found to be a useful tool to delineate zones of active tectonics in such areas

quantitative analysis of morphometric parameters of kali river basin southern india using bearing azimuth and drainage bad calculator and gis this study deals with the application of visual basic program bearing azimuth and drainage bad calculator which employs a new and easy methodology for extraction of watershed morphometric parameters using bad calculator morphometric analysis was carried out for the kali river basin of southwest coast of india the basin forms a part of the western ghats which is an important mountain range of the indian sub continent and runs nearly parallel to the coast spatial maps of six morphometric parameters have been prepared from the results obtained various linear areal shape and relief morphometric parameters of fifth and sixth order basins have been calculated and interpreted majority of the sub basins show less uniform values 3 to 4 of rbm which indicate the uniform and systematic branching pattern of streams high dd zones are found in the western ghats region whereas low dd zones are observed in the eastern part of the basin and near the estuary the eastern part of the basin shows low fs values whereas nw and sw parts of the basin show high fs values compared to manual measurement bad calculator requires minimal time to quantify the morphometric parameters experimental results show that the software is effective in calculating drainage parameters such as drainage density frequency bifurcation ratio etc using the text file of esri shapefile

morphometric characterization of del molle basin applied to the evaluation of flash floods hazard iglesia department san juan argentina abstract one of the main geological hazards that affect the iglesia department is flash floods produced by heavy seasonal rains characterized by their high velocities and destructive power these streams are generated in the watersheds of the mountainous region of the cordillera frontal the del molle basin was selected as a suitable case to evaluate the potential magnitude of flash floods in relation to their associated hazard level in maliman de arriba located directly at the confluence of the tributaries with the blanco river this paper evaluates some of the hydrological aspects of a torrential regime basin that caused severe damage in maliman during january 2010 this work analyzes different morphometric characteristics of the el molle basin in order to evaluate the flash flood hazard for this purpose the basin is divided into four sub basins and some basic parameters surface perimeter basin length elevations and slope of the main riverbed are calculated these parameters allow approximate prediction of the behavior of the basin in the presence of a series of theoretical rainstorms which may generate unusual runoff volumes the predicted flash floods were compared against the maliman flash flood

plate tectonics and crustal deformation around the japanese islands we analyze over a century of geodetic data to study crustal deformation and plate motion around the japanese islands using the block fault model for crustal deformation developed by matsu ura et al 1986 in this model crustal deformation corresponds to the sum of relative movement among designated blocks and displacement due to dislocations along the locked parts of designated faults we model the area including the japanese islands with 19 crustal blocks and 104 faults based on the distribution of active faults and seismicity three kinds of data are used rates of change of angles and lengths and average velocities of very long baseline interferometry stations with the inversion of these geodetic data we obtain block motions and average slip rates of faults this geodetic model predicts that the pacific plate moves n69 2 w at about 80 3 mm yr relative to the eurasian plate which is much lower than that predicted in geologic models substantial aseismic slip occurs on the subduction boundaries the block containing the izu peninsula may be separated from the rigid part of the philippine sea plate the faults on the coast of japan sea and the western part of the median tectonic line have slip rates exceeding 4 mm yr while the fossa magna does not play an important role in the tectonics of the central japan the geodetic model requires the division of northeastern japan contrary to the hypothesis that northeastern japan is a part of the north american plate owing to rapid convergence the seismic risk in the nankai trough may be larger than that of the tokai gap

seismic monitoring of diffraction images for detection of local heterogeneities diffracted waves contain valuable information regarding both the structure and composition of the media they are in in seismic data processing however these waves are usually regarded as noise in this paper we present an attempt to use scattered diffracted waves for the detection of local heterogeneities the method is based on the detection of diffracted waves by concentrating the signal amplitudes from diffracting points on the seismic section this is done using a correlation procedure that enhances the amplitude of the seismic signal at the location of the diffractors on the common diffraction point section d section the new local time correction for diffraction traveltime curve parameterization is based on the radius of curvature of the diffracted wavefront and near surface velocity we use the idea of seismic monitoring for detection and delineating local objects which may occur within the subsurface resulting from human activity or fast geological processes the method consists of continuou

imaging discontinuities on seismic sections in routine seismic processing normal moveout nmo corrections are performed to enhance the reflected signals on common depth point or common midpoint stacked sections however when faults are present reflection interference from the two blocks and the diffractions from their edges hinder fault location determination destruction of diffraction patterns by poststack migration further inhibits proper imaging of diffracting centers this paper presents a new technique which helps in the interpretation of diffracting edges by concentrating the signal amplitudes from discontinuous diffracting points on seismic sections it involves application to the data of moveout and amplitude corrections appropriate to an assumed diffractor location the maximum diffraction amplitude occurs at the location of the receiver for which the diffracting discontinuity is beneath the source receiver midpoint since the amplitudes of these diffracted signals drop very rapidly on either side of the midpoint an appropriate amplitude correction must be applied also because the diffracted signals are present on all traces one can use all of them to obtain a stacked trace for one possible diffractor location repetition of this procedure for diffractors assumed to be located beneath each surface point results in the common fault point cfp stacked section which shows diffractor locations by high amplitudes the method was tested for synthetic data with and without noise it proves to be quite effective but is sensitive to the velocity model used for moveout corrections therefore the velocity model obtained from nmo stacking is generally used for enhancing diffractor locations by stacking finally the technique was applied to a field reflection data set from an area south of princess well in alberta

dislocation model for aseismic crustal deformation at hollister california geodetic observations at many active plate margins reveal relatively steady aseismic motion during the time between major earthquakes we model the aseismic motion by the relative motion between several blocks that suffer frictional resistance in the upper crust frictional drag is represented by uniform dislocation on a fault surface we assume that friction occurs only on the upper brittle zone of each block boundary and that frictionless sliding occurs below this zone using a bayesian inversion procedure we invert geodetic data to determine the parameters of the block and dislocation model parameters to be estimated include the two horizontal components of velocity for each block and the dislocation rate dip angle slip angle and width of each rectangular fault patch for hollister we assume five blocks and nine rectangular fault patches rates of length change on 92 lines observed by trilateration make up the data triangulation leveling very long baseline interferometry satellite ranging and global positioning system data can also be easily included in our model our inversion procedure uses prior estimates of all block and fault parameters based on geological and seismological data the block parameters are estimated from geological observations of fault displacement rates while the widths of the fault patches are estimated from earthquake hypocentral depths we choose prior estimates of the dislocation rate to match observed creep rates the estimated block motion is well resolved by the geodetic data and agrees well with the geological estimates this suggests that the block motion is steady on time scales from 10 years to 1 m y the net motion across the san andreas calaveras fault system is 38 3 mm yr oriented s38 e thus some additional displacement possibly offshore is needed to match the rate of 56 mm yr predicted by plate tectonic models the depth of the transition from frictional to free sliding varies considerably from 0 4 km on the southern calaveras to 11 km on the central san andreas fault two segments of the san andreas north of 36 50 and south of 36 40 have the greatest potential for moderate to large earthquakes

poststack velocity analysis by separation and imaging of seismic diffractions small geologic features manifest themselves in seismic data in the form of diffracted waves which are fundamentally different from seismic reflections using two field data examples and one synthetic example we demonstrate the possibility of separating seismic diffractions in the data and imaging them with optimally chosen migration velocities our criteria for separating reflection and diffraction events are the smoothness and continuity of local event slopes that correspond to reflection events for optimal focusing we develop the local varimax measure the objectives of this work are velocity analysis implemented in the poststack domain and high resolution imaging of small scale heterogeneities our examples demonstrate the effectiveness of the proposed method for high resolution imaging of such geologic features as faults channels and salt boundaries

integration of hydrological factors and demarcation of groundwater prospect zones insights from remote sensing and gis techniques the study demonstrates the potential of geographical information system and statistical based approaches to identify the hydrological processes and demarcate the groundwater prospect zones of the gangolli basin karnataka state india the basin is situated in humid tropical climate and influenced by three major rivers viz kollur 6th order stream chakra 6th order stream and haladi 7th order stream which cover an area of 1 512 km2 and cumulative length of 84 km various thematic maps drainage geomorphology geology slope soil lineament and lineament density were prepared using survey of india topographic maps indian remote sensing irs p6 images and other published maps hydrogeomorphologic characteristics were correlated with different morphometric parameters to identify the hydrological processes and demarcate the groundwater potential zones of the basin all the hydrological units and morphometric parameters were assigned suitable weightages according to their relative importance to groundwater potentiality to identify the most deficit surplus zones of groundwater based on hydrological characteristics integrated thematic maps reveal that 14 217 km2 of basin area falls under very good 32 486 km2 under good 23 353 km2 under moderate and 30 443 km2 under poor zones for groundwater potential from the sub basin wise prioritisation it has been inferred that sb iii scored highest groundwater potential followed by sb x result of morphometric analyses with the hydrologic parameters indicates that 99 area of sb iii and sb x are under very good to moderate groundwater potential zone this study clearly demonstrates that hydrological parameters in relation with morphometric analyses are useful to demarcate the prospect zones of groundwater

enhancing the detection of small coal structures by seismic diffraction imaging abstract faults are the most important geological structures that need to be detected in any modern underground coal mining project even a fault with a throw of a few metres can create safety issues and lead to costly delays in mine production while seismic surveys are usually successful at locating faults with throws greater than 5 10 m reliable techniques for resolving more subtle faults dykes and other minor features are yet to be developed in seismic data there are two types of seismic energy signatures that can be used for subsurface imaging specular reflections and diffractions specular reflections are created by relatively smooth surfaces between layers of differing impedance contrasts such as at coal rock interfaces specular reflections are used in conventional seismic reflection surveys diffractions are generated by local discontinuities caused by surface roughness faults dykes and fractures in this paper we describe the use of a moving average error filter which along with a process of reflection event flattening for accommodation of dips and undulations of coal seam reflections can be used to effectively extract diffraction signals from post stack reflection seismic data by identifying diffractions small faults and other minor features that are elusive using conventional seismic reflection processing can be detected suggesting that diffraction imaging may be a superior method to seismic reflection imaging both synthetic and real 2d and 3d coal seismic data are used to illustrate the feasibility of diffraction imaging for small fault detection it is demonstrated from synthetic examples that the extracted diffractions can be used to detect faults with a throw of 1 m while a real data example shows that it is possible to detect igneous dykes with widths of just 4 m

diffraction imaging by multifocusing correct identification of geologic discontinuities such as faults pinch outs and small size scattering objects is a primary challenge of the seismic method seismic response from these objects is encoded in diffractions our method images local heterogeneities of the subsurface using diffracted seismic events the method is based on coherent summation of diffracted waves arising in media that include interface discontinuities and local velocity heterogeneities this is done using a correlation procedure that coherently focuses diffraction energy on a seismic section by flattening diffraction events using a new local time correction formula to parameterize diffraction traveltime curves this time correction which is based on the multifocusing method depends on two parameters the emergent angle and the radius of curvature of the diffracted wavefront these parameters are estimated directly from prestack seismic traces the diffraction multifocusing stack dmfs can separate diffracted and reflected energy on a stacked section by focusing diffractions to the diffraction location and defocusing the reflection energy over a large area

geomorphology and morphometry of the de la flecha river basin san juan argentina a geomorphologic and morphometric analysis was performed to determine the characteristics of the de la flecha river basin located in the southwest of san juan province 31 50 s 68 57 w precordillera of san juan the drainage networks were derived from shuttle radar topographic mission srtm satellite imageries landsat tm and spot image and field works the paper also addresses a preliminary evaluation of the flood hazard responsible for severe damage to people and infrastructure in the downstream region the study area covers about 300 km2 comprising of six sub watersheds ranging from 31 7 to 81 8 km2 the irregular morphology of the basin and the diversity of alluvial deposits found along the de la flecha river allow the authors to infer that it is in an active tectonic environment with strong lithological and structural controls one feature common to all analyzed sub basins is their elongated shape which allows for a rapid concentration of water that intensifies the power of the flash floods the drainage network in the different sub basins has in general two predominant patterns one is parallel to sub parallel to the headers and foothill areas and the other in the alluvial zone is divergent los berros canada honda and media agua towns located downstream of the basin are the most affected by flash floods coming from the mountainous area

drainage morphometry and its influence on hydrology in an semi arid region using srtm data and gis an attempt has been made to study drainage morphometry and its influence on hydrology of peddavanka watershed south india drainage networks for the sub basins were derived from topographical map 1 50 000 and shuttle radar topographic mission srtm digital elevation model dem data used for preparing elevation slope and aspects maps geographical information system gis was used in evaluation of linear areal and relief aspects of morphometric parameters the study reveals that srtm dem and gis based approach in evaluation of drainage morphometric parameters and their influence on hydrological characteristics at watershed level is more appropriate than the conventional methods the mean bifurcation ratio r b of the entire basin is 3 88 which indicate that the drainage pattern is not much influenced by geological structures viii sub basin have high elongation ratio r e basin relief b h ruggedness number rn and time of concentration t c it indicates that the erosion and peak discharges are high in these basins therefore the construction of the check dams and earth dams will help in reducing peak discharge on the main channel these studies are very useful for implementing rainwater harvesting and watershed management

quantitative geomorphology applied to fluvial dynamic in aviles and moneta basins tierra del fuego southern argentina the morphometric characteristics of the moneta river basin are compared to those of the aviles river basin both are located in the north of the province of tierra del fuego in argentina and they also have their catchment area in the same range the sierras del bosque runoff on the ne oriented slopes forms the aviles river basin while runoff on the se slopes forms the moneta river basin the analysis was made in two different scales the first as a general scale of the basin and the second as the catchment sector upper middle and lower the quantitative analysis was applied in order to know the behavior of these two fluvial systems for the analysis a cartographic basis scale to 1 20 000 was used which was made on a mosaic of images from google earth the altimetric information was obtained throughout a digital elevation model of 45 m spatial resolution srtm45 shuttle radar topographic mission the indices used were rr rb ish and dd to characterize the geological and geomorphological context and rl re if ct and ca to infer the behavior of the runoff in the catchment it was established that the moneta river basin reaches 6 in order of hierarchy its main channel is 65 52 km long the re determines an elongated basin the ct obtained in the basin is 0 96 whereas the sub basin level was identified to a maximum value of the o3 sm 10 1 46 the dd is low 1 94 km km2 which is directly proportional to the intensity of rainfall and the slopes of the area considered the comparison made at the same scale between basins determines specific fluvial characteristics of each sector upper middle and lower

neotectonic control on drainage systems gis based geomorphometric and morphotectonic assessment for crete greece abstract geomorphic indices can be used to examine the geomorphological and tectonic processes responsible for the development of the drainage basins such indices can be dependent on tectonics erosional processes and other factors that control the morphology of the landforms the inter relationships between geomorphic indices can determine the influence of regional tectonic activity in the shape development of drainage basins a multi criteria decision analysis mcda procedure has been used to perform an integrated cluster analysis that highlights information associated with the dominant regional tectonic activity factor analysis fa and analytical hierarchy process ahp were considered within that procedure producing a representation of the distributed regional tectonic activity of the drainage basins studied the study area is western crete located in the outer fore arc of the hellenic subduction zone one of the world s most tectonically active regions the results indicate that in the landscape evolution of the study area especially the western basins tectonic controls dominate over lithological controls

flood hazard assessment of upper jhelum basin using morphometric parameters morphometric parameters can be useful tools to provide general understanding of physical characteristics of drainage basin with respect to floods to evaluate the flood influencing factors in the upper jhelum basin we delineate the upper jhelum basin into ten sub basins followed by extraction of drainage network and morphometric parameters using advanced spaceborne thermal emission and reflection radiometer digital elevation model and topographic maps in geographic information system the overall flood potential was determined on the basis of compound value obtained for all morphometric parameters of each sub basin the analysis reveals that in general the northeastern segment of the upper jhelum basin reveals comparative higher flood potential than the southwestern segment the tributaries such as lidder veshav arapal arapat and bring exhibit greater potential to produce peak flows during rainfall events while the tributaries like dudhganga rambiara sandran romushi and sasara express moderate to low flood potential respectively the results of this study are likely to be very useful for effective flood hazard mitigation in upper jhelum floodplain

the significance of morphometric analysis for obtaining groundwater potential zones in a structurally controlled terrain watershed development and management plans are more important for harnessing surface water and groundwater resources in arid and semi arid regions to prepare a comprehensive watershed development plan it becomes necessary to understand the topography erosion status and drainage patterns of the region this study was undertaken to determine the drainage characteristics of pageru river basin using topographical maps on a scale of 1 50 000 the total area of the pageru river basin is 480 km2 it was divided into x sub basins for analysis the drainage patterns of the basin are dendritic and include a sixth order stream the quantitative analysis of various aspects of a river basin drainage network characteristics reveals complex morphometric attributes the streams of lower orders mostly dominate the basin the development of stream segments in the basin area is more or less affected by rainfall the elongated shape of the basin is mainly due to the guiding effect of thrusting and faulting the erosional processes of fluvial origin have been predominately influenced by the subsurface lithology of the basin

morphometric analysis of morar river basin madhya pradesh india using remote sensing and gis techniques hydrogeological mapping and drainage analysis can form an important tool for groundwater development assessment of drainage and their relative parameters have been quantitatively carried out for the morar river basin which has made positive scientific contribution for the local people of area for the sustainable water resource development and management geographical information system has been used for the calculation and delineation of the morphometric characteristics of the basin the dendritic type drainage network of the basin exhibits the homogeneity in texture and lack of structural control the stream order ranges from first to sixth order the drainage density in the area has been found to be low which indicates that the area possesses highly permeable soils and low relief the bifurcation ratio varies from 2 00 to 5 50 and the elongation ratio 0 327 reveals that the basin belongs to the elongated shaped basin category the results of this analysis would be useful in determining the effect of catchment characteristics such as size shape slope of the catchment and distribution of stream net work within the catchment

morphometrical analysis of two tropical mountain river basins of contrasting environmental settings the southern western ghats india the morphometric analysis of river basins represents a simple procedure to describe hydrologic and geomorphic processes operating on a basin scale a morphometric analysis was carried out to evaluate the drainage characteristics of two adjoining mountain river basins of the southern western ghats india muthirapuzha river basin mrb in the western slopes and pambar river basin prb in the eastern slopes the basins forming a part of the proterozoic high grade southern granulite terrain of the peninsular india are carved out of a terrain dominantly made of granite and hornblende biotite gneisses the western ghats forming the basin divide significantly influences the regional climate i e humid climate in mrb while semi arid in prb the survey of india topographic maps 1 50 000 and shuttle radar topographic mission digital elevation data were used as the base for delineation and analysis both river basins are of 6th order and comparable in basin geometry the drainage patterns and linear alignment of the drainage networks suggest the influence of structural elements the rb of either basins failed to highlight the structural controls on drainage organization which might be a result of the elongated basin shape the irregular trends in rb between various stream orders suggest the influence of geology and relief on drainage branching the dd values designate the basins as moderate to well drained with lower infiltration rates the overall increasing trend of rl between successive stream orders suggests a geomorphic maturity of either basins and confirmed by the characteristic i hyp values the re values imply an elongate shape for both mrb and prb and subsequently lower vulnerability to flash floods and hence easier flood management the relatively higher rr of prb is an indicative of comparatively steeply sloping terrain and consequently higher intensity of erosion processes further the derivatives of digital elevation data slope aspect topographic wetness index and stream power index showing significant differences between mrb and prb are useful in soil conservation plans the study highlighted the variation in morphometric parameters with respect to the dissimilarities in topography and climate

source models of two large intraslab earthquakes from broadband strong ground motions we construct source models of two large intraslab earthquakes the 1993 kushiro oki and 1994 hokkaido toho oki earthquakes along the southern kurile hokkaido arc based on strong motion records the source models well explain observed broadband strong ground motions we assume a distribution of rectangular shaped asperities on a fault plane and apply the empirical green9s function method to the synthesis of strong ground motions from the asperities the asperity parameters area and stress drop are estimated by matching the synthetic waveforms displacement velocity and acceleration time histories and spectra to the observed ones our source models have the following characteristics compared with those of inland and plate boundary earthquakes having a comparable seismic moment 1 the total asperity area is much smaller and 2 the stress drop is extremely high about 200 400 mpa these indicate that the large intraslab earthquakes radiate seismic energies from a small area in a short time this rupture process results in extremely strong radiation of short period seismic waves finally we confirm a correlation between outer entire fault size seismic moment and short period level of the acceleration source spectrum and inner fault parameters areas and stress drops of asperities for the two intraslab earthquakes

diffraction imaging by focusing defocusing an outlook on seismic superresolution diffractions always need more advertising it is true that conventional seismic processing and migration are usually successful in using specular reflections to estimate subsurface velocities and reconstruct the geometry and strength of continuous and pronounced reflectors however correct identification of geological discontinuities such as faults pinch outs and small size scattering objects is one of the main objectives of seismic interpretation the seismic response from these structural elements is encoded in diffractions and diffractions are essentially lost during the conventional processing migration sequence hence we advocate a diffraction based data oriented approach to enhance image resolution as opposed to the traditional image oriented techniques which operate on the image after processing and migration even more it can be shown that at least in principle processing of diffractions can lead to superresolution and the recovery of details smaller than the seismic wavelength the so called reflection stack is capable of effectively separating diffracted and reflected energy on a prestack shot gather by focusing the reflection to a point while the diffraction remains unfocused over a large area muting the reflection focus and defocusing the residual wavefield result in a shot gather that contains mostly diffractions diffraction imaging applies the classical isotropic diffraction stack to these diffraction shot gathers this focusingmuting defocusing approach can successfully image faults small size scattering objects and diffracting edges it can be implemented both in model independent and modeldependent contexts the resulting diffraction images can greatly assist the interpreter when used as a standard supplement to full wave images

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

diffraction imaging in depth high resolution imaging is of great value to an interpreter for instance to enable identification of small scale faults and to locate formation pinch out positions standard approaches to obtain high resolution information such as coherency analysis and structure oriented filters derive attributes from stacked migrated images since they are image driven these techniques are sensitive to artifacts due to an inadequate migration velocity in fact the attribute derivation is not based on the physics of wave propagation diffracted waves on the other hand have been recognized as physically reliable carriers of high or even super resolution structural information however high resolution information encoded in diffractions is generally lost during the conventional processing sequence indeed migration kernels in current migration algorithms are biased against diffractions we propose here methods for a diffraction based data oriented approach to image resolution we also demonstrate the different behaviour of diffractions compared to specular reflections and how this can be leveraged to assess characteristics of subsurface features in this way a rough surface such as a fault plane or unconformity may be distinguishable on a diffraction image and not on a traditional reflection image we outline some characteristic properties of diffractions and diffraction imaging and present two novel approaches to diffraction imaging in the depth domain the first technique is based on reflection focusing in the depth domain and subsequent filtering of reflections from prestack data the second technique modifies the migration kernel and consists of a reverse application of stationary phase migration to suppress contributions from specular reflections to the diffraction image both techniques are proposed as a complement to conventional full wave pre stack depth migration and both assume the existence of an accurate migration velocity

2d common offset traveltime based diffraction enhancement and imaging the diffracted energy in a seismic recording contains key information about small scale inhomogeneities or discontinuities of the subsurface diffractions can therefore lead to high resolution imaging of subsurface structures associated with hydrocarbon traps however seismic diffracted signals are often much weaker than specular reflections and consequently require enhancement before they can be utilized in this paper diffractions are enhanced relative to reflections based on two traveltime techniques namely the modified common reflection surface approach which uses the common reflection surface technique with some modification to tailor it for diffractions and the replacement media approach derived here for the purpose of a simplified parametrization of diffraction traveltimes both approaches are implemented in the common offset domain with the use of a finite offset central ray unlike the zero or small offset diffraction enhancement techniques that use a zero offset central ray the validity of the two moveout expressions is tested using velocity data taken from a smooth isotropic marmousi model a feasibility test was also carried out with respect to the new replacement media traveltime approximation addressing the various effects of signal to noise ratio depth and lateral displacement of the diffractor location finally diffraction enhancement and imaging was performed on 2d seismic data from the jequitinhonha basin offshore brazil diffractions were significantly enhanced and a high resolution image of the discontinuities of the subsurface was obtained

predictive models to estimate sediment volumes deposited by debris flows vargas state venezuela an adjustment of multivariate statistical techniques debris flows are a moving mass composed from water and solids mixture mainly in form of sediments with a high destructive power the debris volume that is transported and deposited outside the drainage system of a watershed has a great importance in the definition of its hydrological response the objective of this work was to propose predictive models generated through the adjustment of multivariate statistical techniques to estimate the sediment volumes deposited by debris flows measurements and calculations of the morphometric parameters of the watersheds and drainage networks have been performed with the support of gis software and spreadsheets the relationships between morphometric parameters and sediment volumes have been analyzed by applying multivariate statistical techniques such as linear correlation analysis the principal component analysis and multiple linear regression analysis have been performed with principal components which allowed the generation of predictive models from the predictive models generated for the sediment volumes deposited by the debris flow event of december 1999 raised results closer to reality with better pearson s correlation coefficients from those related to the gradient and shape of the watershed relief and extension of the drainage network morphometric variables for the estimation of deposited sediment volumes due pre and post 1999 event conditions only the predictive models generated with the gradient and shape of the watershed relief variable have had good results

the interplate coupling and stress accumulation process of large earthquakes along the nankai trough southwest japan derived from geodetic and seismic data abstract the interplate coupling and stress accumulation process associated with the subduction of the philippine sea plate beneath the eurasian plate along the nankai trough where large earthquakes have occurred periodically have been investigated in detail taking into account the three dimensional complicated structure of the philippine sea plate and its motion relative to the eurasian plate for this purpose we mainly used extensive geodetic data in southwest japan such as levelling tide gauge and trilateration which presumably are effective means of revealing coupling properties and applied a three dimensional finite element method here two seismic periods associated with the 1944 tonankai and 1946 nankaido earthquakes were considered interseismic and pre seismic stages comparing the coupled regions obtained for the two cases a possible explanation of its temporal change was proposed it might gradually spread from a shallower to deeper portion with transition from the interseismic to pre seismic stage a comparison of the coupling properties between southwest japan and northeast japan reveals the following properties in southwest japan the coupling is generally strong and its region is limited in a relatively shallow portion the pre seismic coupled regions coincide with the co seismic and post seismic fault zone suggesting that the accumulated stress is released at the time of a large earthquake in northeast japan on the other hand the coupling is weak and its extent appears to reach a depth of about 100 km and the co seismic and post seismic regions are limited to the upper half of the coupled region the weakly coupled region in southwest japan seems to correspond well to the region with high seismic activity a high dip angle subducting slab and the possible existence of seamounts in contrast to the strongly coupled region correlated with low seismicity low dip angle subduction and no seamounts on the western coupled region off shikoku an anomalously strongly coupled region corresponding to a convergence rate of 7 8 cm year 1 was identified this may be caused by geomorphological properties such as the low dip angle of the subducting plate and smooth plate boundary resulting in a large amount of stress concentration there the stress field associated with the interplate coupling was also calculated there is fair agreement between the observations and calculations near the plate boundary beneath the southern kii peninsula and shikoku although the effects of the interplate coupling may have some influence on strike slip faulting with the n s compressive axes beneath shikoku other earthquake generating stress such as a two layered double buckling would be dominant there

near field observations of an offshore mw 6 0 earthquake from an integrated seafloor and subseafloor monitoring network at the nankai trough southwest japan an mw 6 0 earthquake struck 50 km offshore the kii peninsula of southwest honshu japan on 1 april 2016 this earthquake occurred directly beneath a cabled offshore monitoring network at the nankai trough subduction zone and within 25 35 km of two borehole observatories installed as part of the international ocean discovery program s nantroseize project the earthquake s location close to the seafloor and subseafloor network offers a unique opportunity to evaluate dense seafloor geodetic and seismological data in the near field of a moderate sized offshore earthquake we use the offshore seismic network to locate the main shock and aftershocks seafloor pressure sensors and borehole observatory data to determine the detailed distribution of seafloor and subseafloor deformation and seafloor pressure observations to model the resulting tsunami contractional strain estimated from formation pore pressure records in the borehole observatories equivalent to 0 37 to 0 15 strain provides a key to narrowing the possible range of fault plane solutions together these data show that the rupture occurred on a landward dipping thrust fault at 9 10 km below the seafloor most likely on the plate interface pore pressure changes recorded in one of the observatories also provide evidence for significant afterslip for at least a few days following the main shock the earthquake and its aftershocks are located within the coseismic slip region of the 1944 tonankai earthquake mw 8 0 and immediately downdip of swarms of very low frequency earthquakes in this region illustrating the complex distribution of megathrust slip behavior at a dominantly locked seismogenic zone

rupture process of the 1944 tonankai earthquake ms 8 1 from the inversion of teleseismic and regional seismograms 1 we digitized teleseismic and regional records of the 1944 tonankai earthquake we used the multiple time window method to invert these records for the spatial and temporal distribution of slip and rake we assume a 220 140 km fault with a spacing of 20 20 km and a maximum rupture velocity of 2 5 km s the inversion resolved an asperity along the accretionary wedge and under the shima and atsumi peninsulas the rupture propagated from southwest to northeast and there was little slip near the hypocenter consistent with the absence of uplift in the overlying submarine forearc basin the peak slip is 2 3 m and the total seismic moment is 2 4 1028 dyn cm mw 8 2 we compared the predicted and observed vertical geodetic displacements and inferred that the limit of rupture is consistent with the change from subsidence to uplift west of the atsumi peninsula this suggested that the earthquake did not rupture the plate interface in the tokai gap we modeled the tsunami using sea bottom displacements generated from this slip model the tide gauge amplitudes and frequency content are consistent with those predicted resolution tests from inverting synthetic seismograms computed using a simplified slip model indicated that the combination of teleseismic and regional data sets best recovers the asperity locations and peak slips given similar station geometry and degrees of freedom an inversion of the synthetic regional data set indicates that slip artifacts can occur early in the rupture process due to many clipped records while the inversion of synthetic teleseismic data set had less resolution and recovered only 50 of the peak slip

deformation of an island arc rates of moment release and crustal shortening in intraplate japan determined from seismicity and quaternary fault data the historical record of large m 6 9 earthquakes and geologically determined rates of slip on quaternary faults in intraplate japan honshu and shikoku are used to estimate the average rate of seismic moment release m for the last 400 years and during the late quaternary respectively values of m estimated from the two data sets are similar in regions where seismic activity is concentrated on land we interpret this observation to suggest that m in intraplate japan has been constant during the late quaternary and is relatively free from secular variation when averaged over periods of several hundreds of years m in shikoku may be attributed almost solely to right lateral slip of the median tectonic line mtl the easterly strike of the mtl is consistent with a compressive stress field that trends northwest crustal shortening of the izu peninsula taken up on a set of strike slip faults that show north by northwest compression is 1 mm yr northeast honshu is characterized by a set of reverse type faults that trend northerly conversion of m in northeast japan to strain rates suggests that about 5 of the relative plate motion between japan and the pacific plate 9 7 cm yr is accommodated as a permanent east west shortening 5 mm yr of northeast honshu the predominant deformation in central and western honshu takes place as slip on a conjugate system of strike slip faults that strike northeast and southeast and show right lateral and left lateral motion respectively crustal shortening resulting from slip on faults in central and western honshu is 5 and 0 5 mm yr respectively in an easterly direction central and western honshu are in closest proximity to the nankai trough and hence the stress field in these regions cannot simply be attributed to the accommodation of the relative northwesterly convergence of the philippine sea plate the northward impingement of the izu peninsula into honshu may influence stresses in central and western japan but a conclusive explanation of the stress field in central and western honshu remains an enigma

hydrogeomorphological and groundwater prospects of the pageru river basin by using remote sensing data hydrogeomorphology and lineament studies have been completed by using satellite data for the pageru river basin cuddapah district andhra pradesh india through visual interpretation of irs 1b liss ii fcc 57j 6 j 7 j 10 and j 11 on a 1 50 000 scale the area has been visually interpreted to delineate various hydrogeomorphic units and lineaments for the development of groundwater from these studies various geomorphic units were classified as favourable moderately favourable and poor zones of groundwater the integration of geomorphology and lineament studies reveal that shallow groundwater occurrence is controlled by geomorphological characteristics whereas faults fractures control the yield of groundwater at intermediate depths

morphometric evaluation of papanasam and manimuthar watersheds parts of western ghats tirunelveli district tamil nadu india a gis approach a morphometric analysis was carried out to describe the topography and drainage characteristics of papanasam and manimuthar watersheds these watersheds are part of western ghats which is an ecologically sensitive region the drainage areas of papanasam and manimuthar watersheds are 163 and 211 km2 respectively and they show patterns of dendritic to sub dendritic drainage the slope of both watersheds varied from 0 to 59 and 0 to 55 respectively moreover the slope variation is chiefly controlled by the local geology and erosion cycles each watershed was classified as a fifth order drainage basin the stream order of the basin was predominantly controlled by physiographic and structural conditions the increase in stream length ratio from lower to higher order suggests that the study area has reached a mature geomorphic stage the development of stream segments is affected by rainfall and local lithology of the watersheds

perceptions in seismic imaging part 2 reflective and diffractive contributions to seismic imaging everyone who deals with seismic data probably believes they understand the reflective process to some degree particularly when the depiction involves raypaths linking a source and receiver to a reflection point on a planar boundary delimiting two materials with different elastic properties there is slightly less unanimity when expanding wave fronts represent the transmission of seismic energy but no obvious major hurdles arise to interfere with our basic understanding

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

zenisu ridge a deep intraoceanic thrust related to subduction off southwest japan abstract during the french japanese kaiko project seabeam seismic and submersible observations were made in the eastern part of the nankai subduction zone close to the area of collision between the izu bonin island arc and the japan margin the most prominent feature is the zenisu ridge an elongated relief of the philippine sea plate running parallel to the trench magnetic anomalies indicate that the crust of the zenisu ridge is a part of the shikoku oceanic basin formed in the early miocene 23 ma ago and presumably uplifted at a later stage structural analysis of seismic data and diving observations lead us to interpret the superficial structure as being due to compressive tectonics mapping the acoustic basement reveals that the southeastern flank of the ridge is bounded by a double thrust both segments being of equal magnitude vertical offset about 1 to 1 5 km geophysical data support the hypothesis of a main thrust cutting through most of the lithosphere and flattening at depth the overall structure of the surrounding area reveals a compressive deformation zone widening toward the east the magnitude of the compressive deformation decreasing westward as well as southward of the zenisu ridge

rupture directivity effect and stress heterogeneity of the 2013 nantou blind thrust earthquakes taiwan abstract we investigated broadband evidence of the rupture directivity effect and estimated stress drop for the 2013 nantou blind thrust earthquakes the 0327 and 0602 crustal events from three individual analyses using empirical green s functions deconvolution source time function analysis source spectral ratio analysis and broadband waveform modeling of a strong motion generation area although these two adjacent events have similar focal mechanisms the 0327 event shows only up dip directivity to the west with an estimated stress drop of 9 0 mpa and the 0602 event displays significant rupture directivity to the southwest with an estimated stress drop of 14 2 mpa the obvious variance in the rupture behavior and stress drop of these two nearby events which might be related to immature blind faulting suggests that this region requires additional study of the stress heterogeneity to better assess the seismic hazard

seismotectonics of the hida region central honshu japan abstract seismotectonic features of the northern hida region central honshu japan have been investigated in some detail mainly on the basis of the last 6 years of observations of seismicity and focal mechanism of a large number of earthquakes with reference to the geological and tectonic setting and evidence of a large earthquake in the past it was found that high seismicity is concentrated with a remarkably clear lineation but with a relatively low activity in the central section along the atotsugawa fault extending for about 70 km this is one of major quaternary faults in this region the high seismicity with spatially nonuniform distribution may be related to postseismic stress concentration after the 1858 hida earthquake m 7 0 and to heterogeneous fault strength seismicity is also high with belt like extension beneath the hida mountain range which is the highest mountain system in the japan islands the depth distribution of seismicity is clearly bounded at 15 km below the atotsugawa fault and 8 km beneath the hida mountains the local variations can be interpreted as being due to the difference in the brittle ductile transition depth which suggests higher temperature beneath the mountains involving active volcanoes the focal mechanism solutions indicate that the maximum compressive stress is oriented in an ese wnw direction which is more consistent with the direction of motion of the pacific plate relative to the eurasian plate rather than the suggested relative motion between the north america and eurasian plates the magnitude of the shear stress working in this region is estimated to be less than 700 bar

separation and imaging of seismic diffractions using migrated dip angle gathers abstractcommon reflection angle migration can produce migrated gathers either in the scattering angle domain or in the dip angle domain the latter reveals a clear distinction between reflection and diffraction events we derived analytical expressions for events in the dip angle domain and found that the shape difference can be used for reflection diffraction separation we defined reflection and diffraction models in the radon space the radon transform allowed us to isolate diffractions from reflections and noise the separation procedure can be performed after either time migration or depth migration synthetic and real data examples confirmed the validity of this technique