identifying space time clustering properties of the 1983 1997 irpinia basilicata southern italy seismicity abstract the fractality of the earthquake sequence 1983 1997 of irpinia basilicata southern italy one of the most seismically active regions of the mediterranean area has been analysed by temporal and spatial fractal tools the fractal exponent estimated by the allan factor method characterises the time clustering behaviour of the set of earthquakes while the correlation dimension d c calculated by means of the correlation integral method gives information on the space clustering behaviour of the sequence of seismic events analysing the variations of both the parameters we recognised the presence of a strong space time clusterisation associated with the major events that occurred in the investigated area

estimation of offsets in gps time series and application to the detection of earthquake deformation in the far field extracting geophysical signals from global positioning system gps coordinate time series is a well established practice that has led to great insights into how the earth deforms often small discontinuities are found in such time series and are traceable to either broad scale deformation i e earthquakes or discontinuities due to equipment changes and or failures estimating these offsets accurately enables the identification of coseismic deformation estimates in the former case and the removal of unwanted signals in the latter case which then allows tectonic rates to be estimated more accurately we develop a method to estimate accurately discontinuities in time series of gps positions at specified epochs based on a so called offset series the offset series are obtained by varying the amount of gps data before and after an event while estimating the offset two methods a mean and a weighted mean method are then investigated to produce the estimated discontinuity from the offset series the mean method estimates coseismic offsets without making assumptions about geophysical processes that may be present in the data i e tectonic rate seasonal variations whereas the weighted mean method includes estimating coseismic offsets with a model of these processes we investigate which approach is the most appropriate given certain lengths of available data and noise within the time series themselves for the sumatra andaman event with 4 5 yr of pre event data we show that between 2 and 3 yr of post event data are required to produce accurate offset estimates with the weighted mean method with less data the mean method should be used but the uncertainties of the estimated discontinuity are larger

geochemistry of champagne hot springs shallow hydrothermal vent field and associated sediments dominica lesser antilles the champagne hot springs chs shallow submarine hydrothermal system is located along the submerged flank of the plat pays volcanic system on the southwest section of the island of dominica lesser antilles we have conducted a detailed geochemical study of the hydrothermal system with the objectives to investigate the source of the hydrothermal fluids and gases their effect on sediment and precipitate chemistry as well as comparing the submarine vent chemistry with nearby on land hydrothermal vents finally we compare our findings to previous preliminary data from chs and compare sediment chemistry to that of average caribbean sediments we also report on a newly discovered area of submarine hydrothermal venting located approximately 40 m to the north of chs this area consists of hydrothermally altered areas of sand that contain abundant coatings of hydrous ferric oxides hfo on sediment grains geochemical and mineralogical analyses of vent waters pore waters gases sediments and precipitates reveal that the vent fluids consist of a mixture of entrained seawater and meteorically derived hydrothermal fluid in varying proportions vent fluids are depleted in br s o4 c l n a k and sr 2 relative to ambient seawater these species are all positively correlated with mg 2 which is also depleted relative to seawater boron fe as sb mn si and li are all enriched relative to ambient seawater pore waters in the hydrothermally altered sand patches have essentially the same chemistry mixing between fe 2 rich vent fluids and seawater causes rapid oxidation of fe 2 to insoluble fe 3 and leads to precipitation of hfo at the vent site and subsequent formation of hydrothermally altered sand patches the elevated concentrations of as and sb in the precipitates and sediments relative to average caribbean seafloor sediments reflect adsorption by hfo gas samples from the vent site are typical arc type gases and have both meteoric and magmatic signatures d 2005 elsevier b v all rights reserved

fault source of the 2 september 2009 mw 6 8 tasikmalaya intraslab earthquake indonesia analysis from gps data inversion tsunami height simulation and stress transfer abstract we estimate the fault model of the 2 september 2009 tasikmalaya intraslab earthquake based on the gps data available in western java indonesia the focal mechanism of the earthquake was used to help construct two possible fault models a west dipping fault with a strike of 160 8 and an east dipping fault with a strike of 34 0 in this study vertical information from gps data is crucial for constructing the top depth of the fault the subsidence information from gps data located near the epicenter suggests that the earthquake involved a deeper fault model while the amount of the moment release of the east dipping fault model dipe is equivalent to mw 6 9 the moment release of the west dipping fault model dipw is equivalent to mw 6 8 the gps data inversion indicates that model dipw produces a better fit than model dipe the tsunami simulation indicates that the tsunami height generated by the east dipping fault is smaller than that generated by the west dipping fault implying that the maximum tsunami height of the latter is closer to agreement with the reported one unlike model dipe the stress transfer analysis of model dipw indicates that most of the aftershocks were located in the region where cff is positive suggesting positive stress from the ruptured triggered aftershocks the combined analysis of gps data tsunami simulation and stress transfer suggests that the fault ruptured during the 2009 earthquake was dipping westward with a steep dip angle

analysis of the far field crustal displacements caused by the 2011 great tohoku earthquake inferred from continuous gps observations abstract small coseismic offsets detectable using gps techniques were found more than 2300 km away from the great tohoku 2011 earthquake epicenter area of the most intense far field co and postseismic deformations with the maximum offset values exceeding 40 and 18 mm respectively extends westward from honshu island to the korean peninsula northeastern china and southern far east russia sakhalin island does not exhibit notable displacements caused by the earthquake in contrast to the adjacent territories a rectangular fault model with uniform slip was developed based on the gps detected far field coseismic displacements using the spherically layered earth assumption both far and near field coseismic deformations are generally well described by a single segment rupture of 200 96 km2 characterized by thrust slip with minor strike slip component of about 33 m and by the seismic moment value of 1 9 1022 n m mw 8 8 which roughly constrains the major slip area the resultant compact fault geometry revealed that the main portion of the seismic moment had been realized in a relatively small sized rupture segment the sensitivity of far field gps data to the major slip area might also be used in the development of a seismically generated giant tsunami warning system

5 9 mw 18th june 2010 earthquake and fault segment linkage at andaman a study based on macroseismic survey gps geodesy and coulomb stress changes abstract 18th june 2010 5 9 mw earthquake at north andaman triggered along nw se pre existing fault with reverse fault mechanism macroseismic survey and gps geodesy reveal maximum damages following ne sw trend due to normal fault mechanism coulomb stress modeling for post and inter seismic earthquakes after the 2004 mega earthquake show different stages of fault segment linkage at north andaman the present earthquake has been explained as co shock due to asiesmic soft linkage of fault propagation

spatial aftershock distribution of the 26 december 2004 great sumatra andaman earthquake in the northern sumatra area 1 in july 2005 about 6 months after the 2004 great sumatra andaman earthquake 20 ocean bottom seismometers were deployed in the northern sumatra area more than 1000 events were identified during the 12 day recording period after relocation the seismicity shows different patterns on each side of the lower splay fault east of this feature and beneath the aceh basin and fore arc the deep earthquakes outline the subduction megathrust fault west of it the aftershocks distribution is strongly influenced by the active n s oceanic fracture zones of the subducted plate two n s trending clusters of 10 to 50 km deep earthquakes observed below the lower wedge are interpreted as reactivated oceanic fracture zones the postseismic activity suggests a significant influence of the n s active fracture zones of the oceanic plate on the toe of the wedge explaining the dextral wrenching of wedge thrusts in the morphology the megathrust fault does not extend to the trench but outcrops east of these active oceanic fractures and seems to merge upward along the lower splay fault where shallow earthquakes are observed

spatiospectral localization of global geopotential fields from the gravity recovery and climate experiment grace reveals the coseismic gravity change owing to the 2004 sumatra andaman earthquake 1 regional mass fluxes owing to transport and adjustment within the earth system that are implicitly contained in the monthly gravity recovery and climate experiment grace global geopotential coefficients are revealed by localizing global spectra using spatiospectrally concentrated window functions we have analyzed 45 monthly global grace harmonic coefficient series in order to find the coseismic signature associated with the 2004 great sumatra andaman earthquake a significant gravity change after the earthquake is found in the time series of the grace coefficients after localization with a single band limited window centered near the north of the island of sumatra this change is undetectable from the original global coefficients or from coefficients localized elsewhere on the globe a step function with its discontinuity at 26 december 2004 usefully models the coseismic gravity change the localized grace coefficients contain the jumps associated with the earthquake up to degree and order 55 although not all of them within this band produce changes that are statistically significant the gravity change calculated from the localized grace coefficients displays 30 gal peak to peak variations that are very well correlated with an independently derived seismic model based on elastic dislocation theory

transtension to transpression a study of strain evolution in andaman islands based on gps measurements following great sumatra andaman earthquake 2004 we use campaign mode and continuous gps data from 2005 to 2008 to examine the evolving strain pattern in andaman islands after the great sumatra andaman earthquake two and half years after the earthquake the post seismic period changes to inter seismic period at port blair post seismic displacement rate reduced to about 95 with clockwise rotation of azimuths and towards north andaman velocity vector gradually rotates towards north with drop in magnitude the inter seismic displacement was dominated by trench parallel movement strain calculations on inclined transpession model shows deformations at andaman were highly heterogeneous both in post and inter seismic periods with dominant strike slip and dip slip shearing along with layer parallel shortening and extension post seismic and inter seismic periods had suffered simultaneous subduction perpendicular extension and contraction leading to transtension and transpression deformational environments respectively occurrence of earthquakes during post and inter seismic periods were results of interplay between simple shear and pure shear components of the strain matrix

coseismic and post seismic signatures of the sumatra 2004 december and 2005 march earthquakes in grace satellite gravity s u m m a r y the grace satellite mission has been measuring the earth s gravity field and its temporal variations since 2002 april although these variations are mainly due to mass transfer within the geofluid envelops they also result from mass displacements associated with phenomena including glacial isostatic adjustment and earthquakes however these last contributions are difficult to isolate because of the presence of noise and of geofluid signals and because of grace s coarse spatial resolution 400 km half wavelength in this paper we show that a wavelet analysis on the sphere helps to retrieve earthquake signatures from grace geoid products using a wavelet analysis of grace geoids products we show that the geoid variations caused by the 2004 december m w 9 2 and 2005 march m w 8 7 sumatra earthquakes can be detected at grace resolution the 2004 december earthquake produced a strong coseismic decrease of the gravity field in the andaman sea followed by relaxation in the area affected by both the andaman 2004 and the nias 2005 earthquakes we find two characteristic timescales for the relaxation with a fast variation occurring in the vicinity of the central andaman ridge we discuss our coseismic observations in terms of density changes of crustal and upper mantle rocks and of the vertical displacements in the andaman sea we interpret the post seismic signal in terms of the viscoelastic response of the earth s mantle the transient component of the relaxation may indicate the presence of hot viscous material beneath the active central andaman basin

long term seismic observations along myanmar sunda subduction margin insights for 2004 m w 9 0 earthquake the present study investigates the temporal variation of few seismic parameters between the myanmar zone i andaman nicobar northwest sumatra zone ii southeast sumatra west indonesia zone iii and east indonesia zone iv converging boundaries in reference to the generation of 26 december 2004 mw 9 0 off sumatra mega earthquake event the four segments are distinguished based on tectonics parameters distinct geological locations great earthquake occurrences and the wadati benioff zone characteristics two important seismic parameters such as seismic energy and b values are computed over a time window of 6 month period during the entire 1976 2013 period for these segments the b values show a constant decrease in zones ii iii and iv whereas the zone i does not show any such pattern prior to the 2004 mega event the release of seismic energy was also gradually decreasing in zones ii and iii till the 2004 event and little similar pattern was also noted in zone iv this distinct observation might be indicating that the stress accumulation was dominant near the sumatra java area located towards southeast of zone ii and northwest of zone iii the released strain energy during the 2004 event was subsequently migrated towards north rupturing 1300 km of the boundary between the northwest sumatra and the north andaman the occurrence of 2004 mega event was apparently concealed behind the long term seismic quiescence existing near the sumatra and nicobar margin a systematic study of the patterns of seismic energy release and b values and the long term observation of collective behaviour of the margin tectonics might have had given clues to the possibility of the 2004 mega event

seismicity gravity anomalies and lithospheric structure of the andaman arc ne indian ocean abstract the andaman arc in the northeastern indian ocean defines nearly 1100 km long active plate margin between the india and burma plates where an oblique benioff zone develops down to 200 km depth several east trending seismologic sections taken across the andaman benioff zone abz are presented here to detail the subduction zone geometry in a 3 d perspective the slab gravity anomaly computed from the 3 d abz configuration is a smooth long wavelength and symmetric gravity high of 85 mgal amplitude centering to the immediate east of the nicobar island where a prominent gravity high follows the nicobar deep the slab residual gravity anomaly srga and mantle bouguer anomaly mba maps prepared for the andaman plate margin bring out a double peaked srga low in the range of 150 to 240 mgal and a wider cum larger mba low having the amplitude of 280 to 315 mgal demarcating the andaman arc trench system the gravity models provide evidences for structural control in propagating the rupture within the lithosphere the plate margin configuration below the andaman arc is sliced by the west andaman fault waf as well as by a set of sympathetic faults of various proportions often cutting across the fore arc sediment package some of these fore arc thrust faults clearly give rise to considerably high post seismic activity but the seismic incidence along the waf further east is comparatively much less particularly in the north although the lack of depth resolution for many of the events prohibits tracing the downward continuity of these faults tectonic correlation of the gravity derived models presented here tends to favour the presence of oceanic crust below the andaman nicobar outer arc ridge

a regionalized upper mantle rum seismic model seismic velocity heterogeneity in the earth s mantle is strongly concentrated near its top the shallow heterogeneity of the mantle correlates strongly with surface tectonics we use these observations as constraints of a tomographic experiment aimed at building a regionalized upper mantle rum reference model we use a select set of teleseismic travel times to minimize the mapping of mislocation into structure the data selection emphasizes the robustness of individual picks the form of the rum model is a set of velocity profiles as functions of depth through the upper mantle for each of the different tectonic provinces of earth together the profiles constitute a three dimensional model which incorporates considerable structural detail but is described by only 90 parameters and has only about 22 degrees of freedom this is achieved by irregularly sampling a detailed regionalization of the globe by detailed mapping of subducted lithosphere in the mantle as defined by seismicity and by combining these structures in an irregular grid in which bookkeeping is efficiently handled the resulting rum model includes subducting slabs as sharp fast features in the upper mantle old continents are fast young oceans are slow models have been derived for both compressional and shear velocity the rum model is designed to represent as much of upper mantle heterogeneity as seen by body wave travel times as possible with a simple model it can be useful as a reference model for individual tectonic regions travel times are efficiently generated for the rum model mislocations of explosions of known location are significantly reduced when corrections for the rum model are applied to travel time residuals for a spherically symmetrical earth model

seismology speed and size of the sumatra earthquake we now have a clearer picture of the seismic features of last year s gigantic event our seismological results reveal that indonesia s devastating sumatra andaman earthquake on 26 december 2004 was 2 5 times larger than initial reports suggested second only to the 1960 chilean earthquake in recorded magnitude they indicate that it slowly released its energy by slip along a 1 200 km fault generating a long rupture that contributed to the subsequent tsunami now that the entire rupture zone has slipped the strain accumulated from the subduction of the indian plate beneath the burma microplate has been released and there is no immediate danger of a similar tsunami being generated on this part of the plate boundary although large earthquakes on segments to the south still present a threat

multiple cmt source analysis of the 2004 sumatra earthquake while it is agreed that the great sumatra earthquake of december 26 2004 was among the largest earthquakes of the past century there has been disagreement on how large it was which part of the fault ruptured and how the rupture took place we present a centroid moment tensor cmt analysis of the earthquake in which multiple point sources are used in the inversion to mimic a propagating slip pulse the final model consists of five point sources with the southernmost sources accounting for the majority of the moment release the presumed fault planes of the southern sources strike northwest while those in the north strike northeast consistent with the geometry of the subduction trench slip on the fault is found to be more oblique in the north than in the south the inversion with five sources leads to a moment magnitude for the sumatra earthquake of m w 9 3 consistent with estimates from long period normal mode amplitudes

structural styles chronology rates of deformation and time space relationships in the umbria marche thrust system central apennines italy structural interpretation of geological and geophysical data available for the central apennines italy allowed us to draw balance and restore three geological profiles across the external zones of the umbria marche thrust system and to evaluate the timing and rates of deformation in a roughly 4 ma time window from late messinian to late pleistocene time from this data set we established a general correlation between spacing l and thickness d of the thrust sheets which was used as a depth correction factor for deriving local versus regional depths to the sole thrust and a time space relationship between the closing time of activity of each thrust and the distance x from a reference point within the system

low frequency acoustic gravity waves from coseismic vertical deformation associated with the 2004 sumatra andaman earthquake mw 9 2 1 atmospheric pressure perturbations from the 2004 sumatra andaman earthquake mw 9 2 were observed by sensitive microbarographs at several global stations among these observations very low frequency acoustic gravity waves 1 4 2 8 mhz with a group velocity around 300 314 m s and amplitudes ranging between 1 and 12 pa can be clearly identified through data processing at four stations on the japanese islands and also at four international monitoring system ims stations around the indian ocean assuming several seismic source parameters for this great thrust earthquake we produce synthetic barograms using a realistic thermal structure in the atmosphere up to an altitude of 220 km for this modeling we incorporate the source dimensions in different zones the expanding velocity of the source region the vertical displacements of uplift and subsidence and their time constants combinations of these source parameters provide synthetic waveforms consistent with the general features of the observed low frequency records the results clearly indicate that the recorded waves may have been generated by large scale coseismic uplift and subsidence of the sea bottom and associated swelling and depression of the sea surface over the source region extending for 1500 km the uplift in the south central zone of the andaman nicobar regions may be substantially larger than in the other zones the time constant of the coseimic vertical deformation is found to be in the range of 1 0 1 5 min which may correspond to the time elapsed shortly before the generation of tsunami waves

visibility graph analysis of the 2003 2012 earthquake sequence in the kachchh region of western india a visibility graph vg is a rather novel statistical method in earthquake sequence analysis it maps a time series into networks or graphs converting dynamical properties of the time series into topological properties of networks by using the vg approach we defined the parameter window mean interval connectivity time that informs about the mean linkage time between earthquakes we analysed the time variation of in the aftershock depleted catalogue of kachchh gujarat western india seismicity from 2003 to 2012 and we found that i changes through time indicating that the topological properties of the earthquake network are not stationary and ii appeared to significantly decrease before the largest shock m5 7 that occurred on march 7 2006 near the gedi fault an active fault in the kachchh region

rupture process of the 2004 sumatra andaman earthquake the 26 december 2004 sumatra andaman earthquake initiated slowly with small slip and a slow rupture speed for the first 40 to 60 seconds then the rupture expanded at a speed of about 2 5 kilometers per second toward the north northwest extending 1200 to 1300 kilometers along the andaman trough peak displacements reached 15 meters along a 600 kilometer segment of the plate boundary offshore of northwestern sumatra and the southern nicobar islands slip was less in the northern 400 to 500 kilometers of the aftershock zone and at least some slip in that region may have occurred on a time scale beyond the seismic band

the great sumatra andaman earthquake of 26 december 2004 the two largest earthquakes of the past 40 years ruptured a 1600 kilometer long portion of the fault boundary between the indo australian and southeastern eurasian plates on 26 december 2004 seismic moment magnitude mw 9 1 to 9 3 and 28 march 2005 mw 8 6 the first event generated a tsunami that caused more than 283 000 deaths fault slip of up to 15 meters occurred near banda aceh sumatra but to the north along the nicobar and andaman islands rapid slip was much smaller tsunami and geodetic observations indicate that additional slow slip occurred in the north over a time scale of 50 minutes or longer

forecasting where larger crustal earthquakes are likely to occur in italy in the near future a forecast of future occurrences of larger m 5 9 crustal earthquakes in italy is made on the basis of historic and instrumental seismicity and following a seismotectonic regionalization recently derived on the basis of geological evidence combined with earthquake epicenters and focal mechanisms completeness problems in the seismic catalog allow one to study only 20 regions out of 58 large crustal seismicity within each seismogenic region is modeled as either a periodic gauss process or a random poisson process according to the experimental coefficient of variation of the series of past occurrences in each region return times are estimated directly from the series of m 4 5 earthquakes if they are sufficient in number or from the gutenberg richter law applied to lower magnitude seismicity m 4 5 otherwise the immediate probability of an m 5 9 crustal seismic event is esti mated to be very low in all regions except southeastern sicily and appennino abrnz zese in the near future next 20 yr the estimated probability is high above 65 also in the appennino forlivese and naso capo d orlando regions in addition to detailed seismic risk reevaluations these regions represent the best bet for a program of intensive monitoring to gather a record of the process of strain accumulation and seismic release

constraining the overall kinematics of the 2004 sumatra and the 2005 nias earthquakes using the earth s gravest free oscillations the giant aceh sumatran 2004 earthquake is the largest earthquake recorded since the great chilean 1960 and the alaskan 1964 events the earth s free oscillations were strongly excited and recorded by numerous stations with an extremely good signal to noise ratio even for the gravest modes these particular modes are interesting because phases of these well separated split free oscillations carry information on the overall kinematics of the source of large earthquakes m w 8 and in particular on the length duration and mean rupture velocity using the singlet stripping technique we study some of the earth s gravest free oscillations s 2 s 3 s 4 1 s 2 s and 1 s recorded at several broadband permanent stations geoscope incorporated research institutions for seismology iris global geodynamics project ggp to recover individual singlet parameters phases frequencies and quality factors we use these parameters to constrain the spatiotemporal extent of the source of the sumatra earthquake of 26 december 2004 and the nias earthquake of 28 march 2005 we mainly use vertical component data from seismometers and superconducting gravimeters because they are less noisy than the horizontal seismic data but we also show that for the 2004 event horizontal components can also be used 1 s 2 on the basis of the initial phase measurements presented here we obtain for the 2004 event a fault length of about 1250 km and a duration of about 550 sec for the 2005 event our measurements favor a model in which the southern segment breaks 40 sec later but the bilateral nature of the rupture and its spatial dimension prevent us from properly constraining its spatial extent

heterogeneous coupling of the sumatran megathrust constrained by geodetic and paleogeodetic measurements geodetic and paleogeodetic measurements of interseismic strain above the sumatran portion of the sunda subduction zone reveal a heterogeneous pattern of coupling annual banding in corals provides vertical rates of deformation spanning the last half of the 20th century and repeated gps surveys between 1991 and 2001 and continuous measurements at gps stations operated since 2002 provide horizontal velocities near the equator the megathrust is locked over a narrow width of only a few tens of kilometers in contrast the locked fault zone is up to about 175 km wide in areas where great interplate earthquakes have occurred in the past formal inversion of the data reveals that these strongly coupled patches are roughly coincident with asperities that ruptured during these events the correlation is most spectacular for rupture of the m w 8 7 nias simeulue earthquake of 2005 which released half of the moment deficit that had accumulated since its previous rupture in 1861 suggesting that this earthquake was overdue beneath the mentawai islands strong coupling is observed within the overlapping rupture areas of the great earthquakes of 1797 and 1833 the accumulated slip deficit since these events is slowly reaching the amount of slip that occurred during the 1833 earthquake but already exceeds the slip that occurred during the 1797 earthquake thus rerupture of part of the mentawai patch in september 2007 was not a surprise in contrast coupling is low below the batu islands near the equator and around enggano island at about 5 s where only moderate earthquakes m w 8 0 have occurred in the past two centuries the correlation of large seismic asperities with patches that are locked during the interseismic period suggests that they are persistent features this interpretation is reinforced by the fact that the large locked patches and great ruptures occur beneath persistent geomorphologic features the largest outer arc islands depth and convergence rate dependent temperature might influence the pattern of coupling through its effect on the rheology of the plate interface but other influences are required to account for the observed along strike heterogeneity of coupling in particular subduction of the investigator fracture zone could be the cause for the low coupling near the equator

active tectonics in the central apennines and possible implications for seismic hazard analysis in peninsular italy abstract the central apennines fault system cafs of peninsular italy overprints earlier structures of a neogene fold and thrust belt and includes segments characterized by diffuse seismicity distributed within a nnw sse trending zone 50 60 km wide the system has been analysed by means of morphotectonic and structural analysis of exposed active fault segments the resulting fault structure consists of an interconnecting network of roughly n s trending left lateral strike slip segments and mostly nw se oriented transtensional to normal faults evidence for recent activity of cafs structures is provided by faulted middle pleistocene holocene deposits including 30 40 ka old pyroclastites and 40 ka old palustrine sediments fresh scarps in both bedrock and late quaternary continental deposits and decametric lateral offsets locally affecting the post wurmian drainage pattern of the area the regional stress field responsible for the development and evolution of the cafs as inferred from fault slip data is characterized by a nw se compression and by a ne sw extension the cafs pattern and its present day kinematics have been related to left lateral strike slip motion on north south trending crustal faults the existence of deep seated strike slip faults in the central apennines has implications for seismic hazard analysis motion along these structures suggests in fact that coseismic surface faulting is distributed and that cumulative displacements include normal transtensional and strike slip components the seismogenic potential of cafs structures can therefore be best described by multiple rupture models and be better analysed in terms of partial contributions of lower rank features constituting congruent structural associations within the system

geochemistry of reduced fluids from shallow cold vents hosting chemosynthetic communities comau fjord chilean patagonia 42 s abstract reduced fluids from shallow marine vents sustain chemosynthetic bacterial mats located at the base of the volcano barranco colorado in comau fjord x huinay 42 23 279 s 72 27 635 w we characterized the chemical environment in which these bacteria thrive to this end we analyzed ch4 h2s o2 dic and stable isotopes 13c 2h and 18o and compared them with readings taken at a control station which lacks evidence of fluid venting and mat forming bacteria in addition ctd measurements chlorophyll a and nutrient analyses were performed at depths of approximately 5 7 m the water column exhibited a pycnocline that formed under the influence of fresh water discharges especially during the summer season which also affected the surface temperature bacterial mats and elemental sulfur flocs were observed in the vicinity of the vents x huinay station and higher concentrations of reduced compounds ch4 and h2s were found in the vent fluids in particular at a depth of 36 m no significant differences in the temperatures of vent and ambient waters were detected the bottom water close to the vents possessed notably low concentrations of reduced compounds indicating a rapid and large quantity dilution of the chemicals from vents the surface water featured light isotopic values of 2h and 18o due to the freshwater input from melting ice and precipitation a linear mixing trend was observed between the freshwater negative isotopic values and the fjord bottom water positive values that was not influenced by vent fluid this trend suggests that the venting water corresponds to the mixing among local meteoric water spring water and seawater this result is relevant to understanding how freshwater and meteoric water influence the chemical composition of seawater and how this mixing could impact the marine biota in the vicinities of the vents

slow slip acceleration beneath andaman islands triggered by the 11 april 2012 indian ocean earthquakes the m w 8 6 and 8 2 strike slip earthquakes that struck the northeast indian ocean on 11 april 2012 resulted in coseismic deformation both at near and distant sites the slip distribution deduced using seismic wave analysis for the orthogonal faults that ruptured during these earthquakes is sufficient to predict the coseismic displacements at the global positioning system gps sites such as ntus palk and cusv but fall short at four continuous sites in the andaman islands region slip modeling for times prior to the events suggests that the lower portion of the thrust fault beneath the andaman islands has been slipping at least at the rate of 40 cm yr in response to the 2004 sumatra andaman coseismic stress change modeling of gps displacements suggests that the en echelon and orthogonal fault ruptures of the 2012 intraplate oceanic earthquakes could have possibly accelerated the ongoing slow slip along the lower portion of the thrust fault beneath the islands with a month long slip of 4 10 cm the misfit to the coseismic gps displacements along the andaman islands could be improved with a better source model assuming that no local process contributed to this anomaly

seismic gap hypothesis ten years after the seismic gap hypothesis states that earthquake hazard increases with time since the last large earthquake on certain faults or plate boundaries one of the earliest and clearest applications of the seismic gap theory to earthquake forecasting was by mccann et al 1979 who postulated zones of high medium and low seismic potential around the pacific rim in the 10 years since there have been over 40 large m 7 0 earthquakes enough to test statistically the earlier forecast we also analyze another forecast of long term earthquake risk that by kelleher et al 1973 the hypothesis of increased earthquake potential after a long quiet period can be rejected with a large confidence the data suggest that contrary to these forecasts places of recent earthquake activity have larger than usual seismic hazard whereas the segments of the circum pacific belt with no large earthquakes in recent decades have remained relatively quiet the clustering of earthquake times does not contradict the plate tectonic model which constrains only the long term average slip rate not the regularity of earthquakes

measuring multifractality in seismic sequences abstract we investigated the multifractal structure of the interevent times between successive earthquakes that occurred in umbria marche which is one of the most seismically active areas of central italy we used the multifractal detrended fluctuation analysis mf dfa which permits detection of multifractality in nonstationary series analyzing the time evolution of the multifractal behaviour of the seismic sequence a loss of multifractality during the aftershocks is revealed

spatial variations of the fractal properties of seismicity in the anatolian fault zones abstract the anatolian fault zones are seismically active strike slip fault zones transcending the anatolian plate in e w and n s directions we investigate the spatial variations of seismicity along these zones in an attempt to investigate fault complexity along strike quantified by the gutenberg richter b value and the fractal correlation dimension of earthquake epicentres using the maximum likelihood method and the correlation integral respectively the investigation covers instrumentally recorded carthquakes of magnitude m 4 5 occurring between 1900 and 1992 we find systematic spatial variations which may be related to structural or mechanical variability along strike in particular the large change in strike at the northern apex of the north anatolian fault zone is associated with the highest correlation dimension and lowest b value for seismicity this century the correlation dimension and b value show a negative correlation with respect to each other similar to results reported in other regional studies of japan and southern california this statistical correlation is stronger when more objective seismic zoning is carried out based on number of events rather than more subjective seismotectonic zoning in common use in seismic hazard analysis

low deformation rate in the koyna warna region a reservoir triggered earthquake site in west central stable india abstract we analyse nine years of gps measurements of crustal deformation from the koyna warna region within the stable india plate the koyna warna region experienced a strong earthquake on 10 december 1967 m 6 3 that is considered to have been induced by the impoundment of the koyna reservoir and the continuing earthquake activity in the region is considered to be associated with the koyna and warna reservoirs the earthquakes occur in a very small region of 30 10 km2 in two well defined seismic zones the nne ssw trending koyna seismic zone and the nnw sse trending warna seismic zone these zones are characterised by predominantly left lateral strike slip motion and normal motion respectively in 2003 we initiated campaign mode gps measurements in the region analysis of the gps data collected over nine years indicate low to moderate deformation rate

structural context of the great sumatra andaman islands earthquake 1 a new three dimensional seismic model and relocated regional seismicity are used to illuminate the great sumatra andaman islands earthquake of december 26 2004 the earthquake initiated where the incoming indian plate lithosphere is warmest and the dip of the wadati benioff zone is least steep along the subduction zone extending from the andaman trench to the java trench anomalously high temperatures are observed in the supra slab mantle wedge in the andaman back arc the subducting slab is observed along the entire plate boundary to a depth of at least 200 km these factors contribute to the location of the initiation of rupture the strength of seismic coupling the differential rupture properties between the northern and southern segments of the earthquake and the cause of convergence in the andaman segment

geochemical characterization of two distinctive systems with evidence of chemosynthetic activity explored at the se pacific margin off chile 46 s and 33 s this study presents the geochemical composition of superficial sediment under oxic and suboxic bottom water conditions along the chilean continental margin se pacific where evidence for benthic chemosynthetic activity associated with diffuse seeping of chemically reduced fluids has been reported the exploration was carried out at 1 the chilean triple junction ctj at a water depth of 2900 m with the additional indication of hydrothermal activity near a methane rich cold seep area 46 s german et al 2010 and 2 the el quisco methane seep site eqss at 340 m water depth 33 s melo et al 2007 krylova et al 2014 while the deeper ctj is located within an oxic environment dissolved oxygen in the bottom waters 164 m the shallower eqss lies within a suboxic environment dissolved oxygen in bottom water 23 m located within the lower limit of the se pacific oxygen minimum zone omz pore water from short cores was analyzed for dissolved major minor and trace elements cl na mg k ca sr si b p ba pb mn fe cd u and mo 13dic sulfide sulfate and methane the solid sediment fraction was likewise analyzed for total organic carbon toc metals and redox potential elevated sediment temperatures were found in superficial sediments 5 13 c at the ctj site which could be due to warm fluids associated with the proximity of the ridge where hydrothermal vents may occur reduced fluids were also present here indicated by higher mn fluxes toward the water column even in oxidized sediments rpd 8 cm which contrasted with the lower fluxes in reduced sediments of the eqss site rpd 2 cm 13c depleted dic anomalously low pore water cl 15 ppb and low concentrations of other major elements may be the result of dilution by fluid seeping and precipitation of major elements producing authigenic enrichment ca mg sr the fluid could also a be diluted by pure water produced during methane hydrate dissociation as observed in other cold seep areas and b correspond to clay mineral dehydration as reported in plate subduction systems the reducing conditions established at the ctj conduct the cd enrichment at a similar magnitude of that seen at the shallower suboxic site eqss evidence of chimney or vent fauna was not observed at the eqss higher toc and total sulfide contents were consistent with enhanced deposition of organic matter and reducing conditions developed in the omz favoring the authigenic enrichment of cd u and pb the geochemical evidence based only on methane concentrations and 13dic is insufficient to establish the presence of methane seeps as previously reported

excitation of 4 min periodic ionospheric variations following the great sumatra andaman earthquake in 2004 1 periodic variations of the ionosphere were detected by ground based gps total electron content tec measurements after the sumatra andaman earthquake in 2004 the observational data showed that the 4 min periodic tec variations occurred 1 h after the earthquake and continued for longer than 4 h at the phkt station about 30 cycles of the 4 min periodic tec variations were observed from 0230 to 0430 ut the maximum peak to peak amplitude of the variations was about 0 6 total electron content unit tecu 1 tecu 1016 el m 2 around 0320 ut the frequency of these periodic variations was 3 9 mhz they were detected by the samp station in the northern sumatra and the phkt and bnkk stations in thailand with the signal from seven gps satellites prn 8 11 13 19 23 27 and 31 they were observed in a limited area from 4 n to 15 n in latitude and from 96 e to 101 e in longitude although the western boundary was not certain because of the limit of the observational field of view the amplitude of these tec variations showed the dependence on the zenith angle of the path between the gps receiver and satellite the amplitude had a maximum when the zenith angle was the smallest this could be caused by the vertical structure of the electron density variations this also suggested that the electrons were oscillating along the geomagnetic field the 4 min periodic tec variations were interpreted to be induced by the long lasting free oscillation of the atmosphere set up by the earthquake their long duration also indicates that they were generated by a nontransient process like resonance

constraints on rupture of the december 26 2004 sumatra earthquake from far field gps observations we use global positioning system gps data from nine permanent gps sites surrounding the epicentre of the december 26 2004 sumatra earthquake to infer coseismic displacements at these sites the results suggest that gps site at samp medan in sumatra island the nearest site from the epicentre experienced a westward coseismic horizontal displacement of about 14 cm while sites in southern india namely hyde and iisc experienced predominantly eastward coseismic horizontal displacement of about 6 11 mm we estimated the slip on the mainshock rupture and rupture extent in a uniform half space by analysing these coseismic displacements we estimate an average reverse slip of about 11 m on the southern part of the rupture and an oblique slip of about 10 m on the northern part of the 1200 100 175 km2 rupture our results of estimated coseismic horizontal displacement in the andaman and nicobar region using the above rupture parameters are also consistent with the near field gps measured coseismic displacements in the region

seismotectonic zoning in east central italy deduced from an analysis of the neogene to present deformations and related stress fields this paper concerns the space time evolution of the late miocene to present contractional and extensional deformations within east central italy with an analysis of the pattern and orientation of the related stress field an insight into the cover basement relations and a discussion of the seismotectonic implications the pattern and orientation of the deformation and stress fields have remained unchanged since late miocene time and have been always characterized by the coexistence and parallelism in contiguous areas in a given time of shortening to the east and elongation to the west with time during a multistage deformation history both the contraction and the extension fields have moved eastward basement involved tectonics with a west dipping multiple detachment system would have allowed the progressive eastward shift of crustal slices corresponding at the surface to well defined tectonic domains with consequent crustal thinning in the tuscan zone and crustal thickening beneath the apennine mountain chain by comparing macroseismic epicenters hypocenters and focal mechanisms with crustal structure and independently known active faults it appears evident that the pattern frequency and distribution of the crustal seismicity are tectonically controlled and that a contraction extension pair is active also at the present time in fact along the adriatic coastline contractional deformation prevails with involvement of pleistocene layers whereas beneath the apennine range extensional deformation prevails both t axes in the inner domain and p axes in the outer domain are oriented southwest northeast or west south west east northeast and this coaxiality reflects the situation depicted by the geologic stress field on this basis we have produced a seismotectonic zoning of east central italy with three distinct domains intramountain seismic zone isz foothills seismic zone fsz and coastal seismic zone csz a plausible explanation for the genesis of the active seismic deformations of east central italy is that the locally intense extensional upper crustal seismicity of the intramountain seismic zone is confined to the hanging wall of a major west dipping active extensional discontinuity whereas the less frequent contractional seismic activity of the coastal seismic zone is within the hanging wall of an outer major active west dipping contractional discontinuity an area of overlap between these two zones is represented by the foothills seismic zone where superposed epicentral patterns from different surfaces of weakness at different depths are the predictable result of the asymmetry of the deformation

second order moment of central california seismicity 1969 1982 the second order moment cross correlation function of earthquakes in the u s geological survey central california catalog between 1969 and 1982 was calculated with respect to a magnitude threshold m 4 0 over interevent distances up to 80 km and interevent times up to 320 days the statistical procedure results in a representation of the spatial temporal structure of the catalog associated with m 4 0 earthquakes and is capable of revealing patterns too weak to be detected in the space time distribution of seismicity for individual earthquake sequences a method is introduced for identifying aftershocks based on a physical two parameter model of the earthquake interaction process the results show that the aftershock process dominates the second order moment and may even obscure the statistical expression of a precursory process a concentration of foreshocks within 15 km and 3 days of m 4 0 main shocks exhibits an apparent migration toward the main shock loci with velocity 2 6 5 3 km d this concentration may be related to an observed tendency for m 4 0 events to cluster auto correlate over this interevent range with the identified aftershocks removed the residual catalog is poissonion in space and time when two m 4 0 earthquakes occur within 80 km and 40 days of each other aftershock productivity appears to be relatively enhanced in the earlier sequence this suggests that aftershock populations are not solely dependent on their main shocks and that unusually productive aftershock sequences may be predictors of future moderate earthquakes

late holocene rupture of the northern san andreas fault and possible stress linkage to the cascadia subduction zone we relate the late holocene northern san andreas fault nsaf paleo seismic history developed using marine sediment cores along the northern california continental margin to a similar dataset of cores collected along the cascadia margin including channels from barclay canyon off vancouver island to just north of mon terey bay stratigraphic correlation and evidence of synchronous triggering imply earthquake origin and both temporal records are compatible with onshore paleoseis mic data in order to make comparisons between the temporal earthquake records from the nsaf and cascadia we refine correlations of southern cascadia great earth quakes including the land paleoseismic record along the nsaf during the last 2800 yr 15 turbidites including one likely from the great 1906 earthquake establish an average repeat time of 200 yr similar to the onshore value of 240 yr the combined land and marine paleoseismic record from the southern cascadia subduction zone includes a similar number of events during the same period while the average recurrence interval for full margin cascadia events is 520 yr the southern cascadia margin has a repeat time of 220 yr similar to that of the nsaf thirteen of the 15 nsaf events were preceded by cascadia events by 0 80 yr averaging 25 45 yr as compared to 80 400 yr by which cascadia events follow the nsaf based on the temporal association we model the coseismic and cumulative post seismic deformation from great cascadia megathrust events and compute related stress changes along the nsaf in order to test the possibility that cascadia earth quakes triggered the penultimate and perhaps other nsaf events the coulomb fail ure stress cfs resulting from viscous deformation related to a cascadia earthquake over 60 yr does not contribute significantly to the total cfs on the nsaf however the coseismic deformation increases cfs on the northern san andreas fault nsaf b y up to about 9 bars offshore of point delgada most likely enough to trigger that fault to fail in north to south propagating ruptures

non uniform scaling features in central italy seismicity a non linear approach in investigating seismic patterns and detection of possible earthquake precursors 1 the detrended fluctuation analysis dfa is a powerful method for capturing scaling behavior in nonstationary time series using an appropriate instability index it is possible to identify and quantify deviations from uniform power law scaling which suggest the presence of changing dynamics in the system under study in this context the scaling behavior of the 1981 2007 seismicity in umbria marche central italy which is one of the most seismically active areas in italy was investigated significant deviations from uniform power law scaling in the seismic temporal fluctuations were revealed mostly linked with the occurrence of rather large earthquakes or seismic clusters

fractal interrelationships between topography and structure fractal interrelationships between topography and structure are investigated in two areas of the north american central appalachian mountains one in the intensely deformed valley and ridge province and the other in the relatively undeformed foreland area of the appalachian plateau province in the valley and ridge province the fractal dimensions of topographic and structural relief vary systematically along the strike of major folds following a second order polynominal trend cross correlation of the fractal dimensions of topography to structure indicates that there is a significant positive correlation between the two fractal analysis of topography in the relatively undeformed foreland area of the appalachian plateau revealed no significant variation in the fractal characteristics of topography across the study area consistent with the lack of near surface structure however fractal analysis of deeper structures beneath the plateau area undertaken using reflection seismic data revealed step wise increases in fractal dimension from the deeply buried precambrian basement to the near surface these vertical changes in fractal dimension can be related to the tectonic history of the area taken together these studies indicate that fractal analysis provides a means to quantify and compare the influence of near surface structure on topographic development and lateral and vertical structural variability fractal analysis provides a means to characterize the systematic changes in the complex patterns formed by topography and structure and the interrelationships between them similarity in their fractal characteristics implies similarity in the relative amplitude and abundance of different wavelength features in the topographic or structural profile 1998 john wiley sons ltd

intraplate deformation of the indian subcontinent 1 while deformation at the earth s surface primarily occurs along tectonic plate boundaries major earthquakes have shaken regions deep within continental interiors three of the largest m 7 5 historic intraplate earthquakes occurred within the indian subcontinent suggesting the possibility of significant intraplate deformation we consider surface velocities determined from new gps data collected at 29 continuous gps stations and 41 survey mode gps stations in india between 1995 and 2007 to find a north south shortening rate of 0 3 0 05 nanostrain yr 1 which may be accommodated by 2 1 mm yr of more localized convergence across central india southward motions at 4 7 mm yr of sites on the shillong plateau in northeast india reflect rapid shortening and high earthquake hazard associated with active thrust faults bounding the plateau the width and magnitude of the elastic strain accumulation field across the himalaya varies little from 76 90 longitude but the strain is more broadly distributed and convergence rates are higher along the eastern 200 km of the range

kinematics and source zone properties of the 2004 sumatra andaman earthquake and tsunami nonlinear joint inversion of tide gauge satellite altimetry and gps data 1 we re analyzed the source of the 26 december 2004 sumatra andaman earthquake and tsunami through a nonlinear joint inversion of an inhomogeneous data set made up of tide gauges satellite altimetry and far field gps recordings the purpose is twofold 1 the retrieval of the main kinematics rupture parameters slip rake and rupture velocity and 2 the inference of the rigidity of the source zone we independently estimate the slip from tsunami data and the seismic moment from geodetic data to derive the rigidity our results confirm that the source of the 2004 sumatra andaman earthquake has a complex geometry constituted by three main slip patches with slip peaking at 30 m in the southern part of the source the rake direction rotates counterclockwise at the northern part of the source according to the direction of convergence along the trench the rupture velocity is higher in the deeper than in the shallower part of the source consistent with the expected increase of rigidity with depth it is also lower in the northern part consistent with known variations of the incoming plate properties and shear velocity our model features a rigidity 20 30 gpa that is lower than the preliminary reference earth model prem average for the seismogenic volume the source rigidity is one of the factors controlling the tsunami genesis for a given seismic moment the lower the rigidity the higher the induced seafloor displacement the general consistence between our source model and previous studies supports the effectiveness of our approach to the joint inversion of geodetic and tsunami data for the rigidity estimation

depth dependent time clustering behaviour in seismicity of southern california temporal fluctuations in seismicity of southern california have been investigated by means of two methods the allan factor analysis and the detrended fluctuation analysis which are used to detect the scaling behaviour of an nonstationary observational time series performing the time clustering analysis varying the depth of the events we found that the seismicity of the area reveals a tendency toward poissonian behaviour near the depth ranges 14 16 km

aftershock investigation in the andaman nicobar islands of india and its seismotectonic implications six three component short period digital seismograph four reftek and two kinemetrics stations were established in different parts of the andaman nicobar islands following the 26 december 2004 devastating sumatra andaman mainshock m w 9 3 here we analyze about 18 000 aftershocks m 3 0 recorded from 6 january to 16 march 2005 to better understand the seismotectonics of the region a sudden burst of aftershock activity with irregular trend in the month of january 2005 was observed at almost all seismograph stations the estimate of p value 0 9532 from aftershocks m 4 5 is near to normal value of 1 0 which suggests a slow decay sequence of aftershock with complex and nonuniform stress change in a fault system creep effects and history dependent stress changes the frequency magnitude relation of the aftershocks followed the power law with average b value of 0 7723 and it varies from 0 49 to 1 03 indicating the compressive stress state of the region and its heterogeneous structure with possible variations in frictional conditions along the fault the distribution of the located aftershocks by a multistation method shows a north south trending aftershock cluster in an area of about 800 300 km 2 which reflects an approximate rupture dimension of the mainshock beneath the andaman nicobar islands most of aftershocks occurred in a depth range of 5 65 km the determination of composite fault plane solutions of the best located aftershock clusters at three different depth ranges 0 15 16 30 and 31 km in the ten blocks of the region suggests that the mainshock rupture propagated through normal reverse and strike slip earthquakes the areas in the vicinity of barren and narcondum volcanic zones show a dominantly normal fault mechanism due to predominant tensional forces suggesting the facilitation of brittle failure in the weakened crust by the process of underheating the zone near baratang mud volcano is associated predominantly with thrust fault at depth of 0 30 km suggesting a high compressive force beneath the baratang that ejected a huge amount of mud and slurry materials to the surface after the 26 december 2004 sumatra andaman earthquake m w 9 3 here we propose that the relocation of our large aftershock dataset using converted sp depth phase technique for precise depth control is needed and its sharing with global earthquake data can render more information on the subduction dynamics and geodynamical processes of the region

spatial variability of the time correlated behaviour in italian seismicity abstract using the national institute of geophysics and volcanology seismic catalogue an analysis of the time clustering behaviour of the instrumental seismicity of italy was performed the time span of the analysed catalogue is from 1986 to 2001 and only the events with magnitude m 2 4 were considered the analysis carried out on the full and aftershock depleted catalogues was performed using detrended fluctuation analysis which permits the identification of correlated temporal structures in time series even in the presence of trends or non stationarities our findings confirm the presence of long range behaviour in the temporal distribution of seismicity data of both full and depleted catalogues suggesting that the clustering phenomenon is not due only to the generation of aftershocks following the occurrence of large shocks but relies on the underlying time structure of the seismicity of italian areas

the size and duration of the sumatra andaman earthquake from far field static offsets the 26 december 2004 sumatra earthquake produced static offsets at continuously operating gps stations at distances of up to 4500 kilometers from the epicenter we used these displacements to model the earthquake and include consideration of the earth s shape and depth varying rigidity the results imply that the average slip was 5 meters along the full length of the rupture including the approximately 650 kilometer long andaman segment comparison of the source derived from the far field static offsets with seismically derived estimates suggests that 25 to 35 of the total moment release occurred at periods greater than 1 hour taking into consideration the strong dip dependence of moment estimates the magnitude of the earthquake did not exceed mw 9 2

rapid determination of earthquake magnitude using gps for tsunami warning systems 1 the 26 december 2004 sumatra earthquake mw 9 2 9 3 generated the most deadly tsunami in history yet within the first hour the true danger of a major oceanwide tsunami was not indicated by seismic magnitude estimates which were far too low mw 8 0 8 5 this problem relates to the inherent saturation of early seismic wave methods here we show that the earthquake s true size and tsunami potential can be determined using global positioning system gps data up to only 15 min after earthquake initiation by tracking the mean displacement of the earth s surface associated with the arrival of seismic waves within minutes displacements of 10 mm are detectable as far away as india consistent with results using weeks of data after the event these displacements imply mw 9 0 0 1 indicating a high tsunami potential this suggests existing gps infrastructure could be developed into an effective component of tsunami warning systems

study of the temporal correlations in the magnitude time series before major earthquakes in japan a characteristic change of seismicity has been recently uncovered when the precursory seismic electric signals activities initiate before an earthquake occurrence in particular the fluctuations of the order parameter of seismicity exhibit a simultaneous distinct minimum upon analyzing the seismic catalog in a new time domain termed natural time and employing a sliding natural time window comprising a number of events that would occur in a few months here we focus on the minima preceding all earthquakes of magnitude 8 and 9 class that occurred in japanese area from 1 january 1984 to 11 march 2011 the day of the m9 tohoku earthquake by applying detrended fluctuation analysis to the earthquake magnitude time series we find that each of these minima is preceded as well as followed by characteristic changes of temporal correlations between earthquake magnitudes in particular we identify the following three main features the minima are observed during periods when long range correlations have been developed but they are preceded by a stage in which an evident anticorrelated behavior appears after the minima the long range correlations breakdown to an almost random behavior possibly turning to anticorrelation the minima that precede m 7 8 earthquakes are distinguished from other minima which are either nonprecursory or followed by smaller earthquakes furthermore it is discussed whether tsallis statistical mechanics in the frame of which it has been suggested that kappa distributions arise can capture the effects of temporal correlations between earthquake magnitudes

spherical earth finite element model of short term postseismic deformation following the 2004 sumatra earthquake 1 decadal scale postseismic deformation of subduction earthquakes has been widely modeled using a maxwell viscoelastic earth with a mantle wedge viscosity of about 1019 pa s short term postseismic deformation within a few years after the earthquake remains a more challenging problem because of the predominance of afterslip of the megathrust and the potentially more complex mantle rheology questions include the necessity of invoking the transient rheology and the relative importance of contributions from afterslip and viscoelastic relaxation in this work we address these questions by developing a spherical earth viscoelastic finite element model for the short term postseismic deformation following the magnitude 9 2 sumatra earthquake of 2004 the model consists of elastic overriding and subducting plates and a viscoelastic mantle of bi viscous burgers rheology with the continental mantle mantle wedge being less viscous than the oceanic mantle by a factor of ten primary observational constraints for the short term postseismic deformation include 1 year net displacements of nine near field gps sites and 3 year time series from three far field sites several hundred kilometers from the 2004 rupture zone model results indicate that the afterslip of the fault must be at work within the first few years after the earthquake the observed deformation is best explained with a model that includes both the afterslip and transient rheology in the preferred model the transient and steady state viscosities of the mantle wedge are 5 1017 pa s and 1019 pa s respectively