observing earthquakes triggered in the near field by dynamic deformations we examine the hypothesis that dynamic deformations associated with seismic waves trigger earthquakes in many tectonic environments our analysis focuses on seismicity at close range within the aftershock zone complementing published studies of long range triggering our results suggest that dynamic triggering is not confined to remote distances or to geothermal and volcanic regions long unilaterally propagating ruptures may focus radiated dynamic deformations in the propagation direction therefore we expect seismicity triggered dynamically by a directive rupture to occur asymmetrically with a majority of triggered earthquakes in the direction of rupture propagation bilaterally propagating ruptures also may be directive and we propose simple criteria for assessing their directivity we compare the inferred rupture direction and observed seismicity rate change following 15 earthquakes m 5 7 to m 8 1 that occurred in california and idaho in the united states the gulf of aqaba syria guatemala china new guinea turkey japan mexico and antarctica nine of these mainshocks had clearly directive unilateral ruptures of these nine seven apparently induced an asymmetric increase in seismicity rate that correlates with the rupture direction the two exceptions include an earthquake preceded by a comparable magnitude event on a conjugate fault and another for which data limitations prohibited conclusive results similar but weaker correlations were found for the bilaterally rupturing earthquakes we studied although the static stress change also may trigger seismicity it and the seismicity it triggers are expected to be similarly asymmetric only if the final slip is skewed toward the rupture terminus for several of the directive earthquakes we suggest that the seismicity rate change correlates better with the dynamic stress field than the static stress change manuscript received 1 march 2002

holocene coastal morphologies and shoreline reconstruction for the southwestern coast of the bohai sea china abstract ground penetrating radar gpr reflection profiles were interpreted and combined with sedimentological data to highlight the morpho evolutionary history of the southwestern sector of the bohai sea the internal structures in gpr images obtained near the holocene maximum transgression boundary revealed concave upward and onlap types of transgressive paleo topography the relationship between historical courses of the yellow river and the distribution of shell ridges at three periods 6 ka 2 ka and recent times showed that the concave upward types derived from the marine sediments overlap the fluvial sediments and the onlap types from the marine sediments cover the coastal lagoon sediments based on the above paleo geographical setting previous sea level markers were corrected taking into account uncertainties of their relationship to former water levels the rates of vertical tectonic displacement evaluated through comparison of the relative sea level rsl data from the gpr images and the holocene predicted sea level elevation markedly affected rsl changes the fitted rsl curves from the corrected sea level indicators showed that the accuracy of former sea level determinations can be improved by comparing with the maximum transgressive position of gpr detection a topographic digital elevation model dem for 6 ka is reconstructed based on the corrected data

sea level change along the italian coast during the holocene and projections for the future published and new sea level data are used to provide projections of sea level change in italy for the year 2100 by adding new isostatic and tectonic component to the ipcc and rahmstorf projections comparison of the observations from more than 130 sites with different geomorphological and archaeological sea level markers with the predicted sea level curves provides estimates of the vertical tectonic contribution to the relative sea level change the results are based on the most recent anu model for the ice sheets of both hemispheres including an alpine deglaciation model on the basis of the eustatic tectonic and isostatic components to the sea level change projections are provided for marine inundation scenarios for the italian coastal plains for the year 2100 that today are at elevations close to current sea level

triggering of the ms 5 4 little skull mountain nevada earthquake with dynamic strains abstract we have developed an approach to test the viability of dynamic strains as a triggering mechanism by quantifying the dynamic strain tensor at seismogenic depths we focus on the dynamic strains at the hypocenter of the m s 5 4 little skull mountain lsm nevada earthquake this event is noteworthy because it is the largest earthquake demonstrably triggered at remote distances 280 km by the m s 7 4 landers california earthquake and because of its ambiguous association with magmatic activity our analysis shows that if dynamic strains initiate remote triggering the orientation and modes of faulting most favorable for being triggered by a given strain transient change with depth the geometry of the most probable lsm fault plane was favorably oriented with respect to the geometry of the dynamic strain tensor we estimate that the magnitude of the peak dynamic strains at the hypocentral depth of the lsm earthquake were 4 strain 2 mpa which are 50 smaller than those estimated from velocity seismograms recorded at the surface we suggest that these strains are too small to cause mohr coulomb style failure unless the fault was prestrained to near failure levels the fault was exceptionally weak and or the dynamic strains trigger other processes that lead to failure

a new observation of dynamically triggered regional seismicity earthquakes in greece following the august 1999 izmit turkey earthquake the m w 7 4 izmit turkey earthquake triggered widespread regional seismicity in greece over a study region extending from 400 km to nearly 1000 km away from the epicenter small events began immediately after the passage of the mainshock surface waves suggesting that the transient stresses of the seismic waves were the trigger the increase in cataloged earthquakes in ordinary continental crust is a new observation and is statistically significant at the 95 level unlike the previous example of distant triggering during the landers earthquake the activated seismicity occurred entirely in non volcanic areas the greek sites were triggered by waves with amplitudes at least a factor of 3 lower than the observed triggering threshold for imperial valley we speculate that dynamic triggering on a regional scale results in countrywide episodes of increased seismicity or superswarms in regions with low triggering thresholds such as greece

nonlinear dynamics granular media and dynamic earthquake triggering the landers earthquake of 1992 triggered a series of earthquakes in other parts of california focusing attention on the mechanism of remote triggering laboratory experiments on granular material under pressure suggest that triggering is a result of seismic waves impinging on a fault and inducing elastic nonlinear behaviour of the fault core accompanied by instantaneous weakening and failure the resulting softening to weakening model fits in well with field observations of real earthquakes the 1992 magnitude 7 3 landers earthquake triggered an exceptional number of additional earthquakes within california and as far north as yellowstone and montana1 2 3 since this observation other large earthquakes have been shown to induce dynamic triggering at remote distances for example after the 1999 magnitude 7 1 hector mine1 and the 2002 magnitude 7 9 denali4 earthquakes and in the near field as aftershocks5 the physical origin of dynamic triggering however remains one of the least understood aspects of earthquake nucleation1 2 3 4 5 the dynamic strain amplitudes from a large earthquake are exceedingly small once the waves have propagated more than several fault radii for example a strain wave amplitude of 10 6 and wavelength 1 m corresponds to a displacement amplitude of about 10 7 m here we show that the dynamic elastic nonlinear behaviour of fault gouge perturbed by a seismic wave may trigger earthquakes even with such small strains we base our hypothesis on recent laboratory dynamic experiments conducted in granular media a fault gouge surrogate6 7 from these we infer that if the fault is weak8 9 10 seismic waves cause the fault core modulus to decrease abruptly and weaken further if the fault is already near failure this process could therefore induce fault slip

geomorphological features of the archaeological marine area of sinuessa in campania southern italy abstract submarine surveys carried out since the 90s along the coastland of sinuessa allowed us to draw up a geomorphological map with archaeological findings along the sea bottom 650 m off and 7 m depth a campanian ignimbrite bedrock was detected dated 39 kyr bp its position is incompatible with the current sea level towards the northern edge of the shoal a depressed area with 24 cubic elements in concrete was surveyed these artefacts pilae are typical of roman maritime structures widespread along the southernmost phlegrean coast beachrocks and accessory landforms at the same depth of bedrock suggest that this was emerging and attended by man in roman times even for activities related to port facilities submerged palaeo channels in alignment of current watercourses on the mainland dissect the shoal these channels were moulded in subaerial environment during wurm glaciation following the tuff deposition and then were drowned by sea level rise the northernmost channel next to the pilae likely allowed transit and manoeuvring of roman ships the discovery along the seabed of a large stump of lead anchor hundreds of roman amphorae and fragments as well as of a depression of millstone confirm this finding probably the sinuous physiography favored the choice of this site for the docking of sinuessa as sheltered from storms

holocene coastline evolution of procida island bay of naples italy abstract we studied the sea level change and the volcano tectonic behaviour of the pericoastal belt of procida and vivara islands which are part of the insular phlegraean fields in the naples bay southern italy on the basis of geological geomorphological and archaeological markers the recognition of two outcrops of submerged beachrocks and the use of many different archaeological remains allowed us to better constrain the morpho evolutionary history of the study area in term of both temporal and palaeoenvironmental reconstructions the archaeological heritage of the phlegraean area is very rich spanning from the bronze age to the middle age and presenting a high density of evidence also in the submarine environment the submarine geomorphological survey furnished numerous new data for the construction of reliable eustatic and subsidence curves three major episodes of subsidence can be recognized in the phlegraean area in the bronze age roman period and middle age the events related to the oldest period have been linked to the history of the vivara procida geoarchaeological system whereas the subsequent episodes recorded in the study area have been correlated to the roman and medieval episodes of subsidence recorded in part of the continental phlegraean area the sea level curve reveals some differences with regard the other similar curves from the continental area both in the amount of subsidence in single time intervals and for the absence of positive motion during the post roman period the curve relative to the subsidence rates is characterized by a cyclic alternation of periods with different rates with a frequency of about 2 ky due to the inversion of the volcano tectonic vertical mobility

seismic velocity change patterns along the san jacinto fault zone following the 2010 m7 2 el mayor cucapah and m5 4 collins valley earthquakes

ground movements and sea level changes in urban areas 5000 years of geological and archaeological record from naples southern italy abstract the occasion offered by the construction of a new branch of naples subway and the related geotechnical and archaeological investigations allowed recognition that the city shoreline underwent remarkable changes during the late holocene highstand when coastal evolution was influenced by vertical ground movements in particular for three investigation sites the density and quality of data were such to permit for the first time the reconstruction of graphs of relative sea level change rslc which compared with curves of the coeval eustatic changes in the tyrrhenian sea were transformed into data about the late holocene history of local tectonics by averaging the data collected in all the different sites the obtained curve of the tectonics suggests that the coastal strip of naples underwent a subsidence rate of 1 3 mm a from about 5000 bp to the xii century ad followed by a 1 m uplift during the last eight centuries mean rate of 1 0 mm a the subsidence trend is consistent with the regional tectonics even if the mean rate was less that in other portions of the bay of naples graben probably because the study area lies among the parallel synthetic faults forming the nw margin of that depression magnaghi sebeto fault zone and not on the proper hanging wall block the prevailing subsiding trend was probably interrupted by minor episodes of uplift not only in the last eight centuries but also during the 3rd millennium bc likely in connection with periods in which the volcano tectonic phenomena of the phlegrean fields district superimposed on the descending movements caused by the msfz the three investigation sites share substantially the same tectonic behaviour in the long term but the details of their rslc records show also discrepancies in some centuries if not due to errors in dating and or in estimating palaeo elevations such discrepancies could be ascribed to episodes of fragmentary tectonic behaviour due probably to occasional reactivation of some e w trending minor lines of the magnaghi sebeto fault zone

in situ assessment of the g γ curve for characterizing the nonlinear response of soil application to the garner valley downhole array and the wildlife liquefaction array abstract we analyze the nonlinear and near surface geological effects of two network for earthquake engineering simulation at university of california santa barbara nees ucsb instrumented sites the garner valley downhole array gvda and the wildlife liquefaction array wla the seismic interferometry by deconvolution method is applied to earthquake data recorded by the multisensor vertical array between january 2005 and september 2013 along the cross section local shear wave velocity is extracted by estimating travel time between sensors the s wave velocity profiles are constructed and compared with classical in situ geophysical surveys we show that velocity values change according to the amplitude of the ground motion and we find anisotropy between east west and north south directions at the gvda site the ratio between average peak particle velocity v and local s wave velocity between two boreholes is tested as a deformation proxy using average peak particle acceleration a the a versus curve is used to represent the stress strain curve for observing the site s nonlinear responses under different levels of excitation nonlinearity is observed from quite low shear strain levels 1 10 5 and a classic hyperbolic model is derived proves to be a good deformation proxy finally the shear modulus degradation curves are constructed for each depth and test site and they are similar to previous laboratory measurements or in situ geophysical surveys a simple comparison regarding nonlinear behavior between gvda and wla is performed

fluid mediated influence of adjacent thrusting on the seismic cycle at parkfield the san andreas fault near parkfield california has experienced moderate to large earthquakes about every 20 years since 1881 the most recent of which occurred in 19661 3 statistical recurrence and precursory quiescence models1 4 5 led to a prediction of the next event for 1992 or before but this event has not yet occurred here i present a model6 that attributes the non occurrence of the expected earthquake to the influence of adjacent thrusting on the rate of fault weakening from increasing pore pressures within the fault zone reductions in fault normal strain rates7 9 and the onset of seismic quiescence along the san andreas fault both coincide with adjacent blind thrust faulting in the 1982 85 earthquake sequence of new idria coalinga and kettleman hills these events turned off a compaction induced weakening mechanism and extended the proposed seismic cycle at parkfield a model simulation of this effect shows a strong correlation in space and time of calculated and observed earthquake hypocentres and shows that observed seismicity patterns from 1969 95 can be explained by reduced compaction rates brought on by adjacent thrusting the model may have applications to other linked thrust strike slip fault systems such as are found in southern california and other transpressional regions

role of fluids in faulting inferred from stress field signatures the stress orientation signature of weak faults containing high pressure fluids has been observed for segments of the san andreas fault system in southern california the inferred lithostatic fluid pressures extend into the surrounding relatively intact rock in a zone scaling with the width of the interseismic strain accumulation repeated strain related fracturing and crack sealing may have created low permeability barriers that seal fluids into the network of currently active fractures

depositional sequences from high concentration turbidity currents cretaceous uhangri formation sw korea abstract a detailed sedimentary facies analysis of the middle part of the uhangri formation late cretaceous sw korea reveals that the dominant facies sequences consist of 1 crudely stratified and inverse to normally graded gravelly sandstone laminated sandstone and sand siltstone couplets 2 inverse to normally graded gravelly sandstone laminated sandstone and sand siltstone couplets 3 stratified and normally graded gravelly sandstone and laminated sandstone the lower units of each fining upward sequence are characterized by crude stratification probably formed under high concentration and cohesionless flow conditions a progressive freezing of the traction carpet causes crude stratification whereas strong dispersive pressures at the base form inverse grading the upper laminated sandstone and sand siltstone couplets represent the overlying low concentration turbidity currents

studying relative sea level change and correlative adaptation of coastal structures on submerged roman time ruins nearby naples southern italy abstract the southwestern periphery of naples is dominated by the posillipo promontory an elongated tuffaceous ridge belonging to campi flegrei active volcanic complex cf the central caldera of cf is well known for offering a rich geoarchaeological record of the vertical ground movements occurred since roman times as the case of the portus julius ruins 37 bc presently found between 10 and 5 m bsl and the middle ages lithophaga perforations at about 7 m asl on the marble columns of the mecellum previously interpreted as serapaeum morhange et al 2006 in the last one hundred years several unrest episodes have been precisely reconstructed in the same area del gaudio et al 2010 de martino et al 2014 but never before vertical ground movements have been presumed along the posillipo hill positioned over the caldera rim this paper deals with a research aimed to evaluate the vertical movements at posillipo area during the last two millennia by means of geomorphological and geophysical surveys in three submerged archaeological sites nisida roman port marechiaro roman port and ruins offshore villa rosebery by precisely measuring the present submersion of all remains found in those sites two relative paleo sea levels have been detected one for the 1st century bc at 4 4 5 0 5 m and another for the 1st century ad at 3 0 5 m only seventeen centimetres of the difference between the two paleo sea levels is attributable to eustasy lambeck et al 2011 while the rest 2 0 5 m has to be ascribed to a phase of accelerated subsidence which has still to be precisely dated and whose duration could have been as short as few years or decades the additional subsidence suffered by the area after the 1st century ad was calculated to be 2 0 0 5 m even though the ground deformations reconstructed in the posillipo area appear less strong than those recognized inside the cf caldera they prove that vertical movements of volcanic origin were not always confined inside the caldera rim in terms of human adaptation the observed archaeological evidence narrates that palazzo degli spiriti was restored closing the rooms submerged by sea the breakwater of marechiaro and the villa foundations at rosebery were probably raised in response to the relative sea level rise

remotely triggered seismicity in yunnan southwestern china following the 2004 mw9 3 sumatra earthquake 1 following the 2004 mw9 3 sumatra earthquake seismicity rate increased sharply over a wide area of up to 2700 km away in yunnan province southwestern china raised seismicity lasts for 14 days during this period more than 800 earthquakes with magnitude between 1 5 and 5 1 occurred this is perhaps the most impressive example of remotely triggered seismicity yet observed major events were clustered at several sites that exhibit complex fault geometries such as step overs and junctures we use statistic approaches including the statistics to examine the statistical significance of the seismic rate increases associated with the sumatra main shock and conclude that there is a reasonable probability that the raised seismicity was remotely triggered by the sumatra earthquake both rapid onset of dynamic triggering the very first event is a m4 6 earthquake occurred during the passage of the rayleigh wave from the sumatra earthquake and delayed response activated a few hours to a few days after the sumatra earthquake are well established the triggered activities show more earthquake swarm like characteristics as indicated by the epidemic type aftershock sequence modeling results large percentage of random components and less magnitude dependence in omori law type self triggering multiple sources of evidence including intensive hydrothermal activities and low velocity and high vp vs zones in the lower to middle crust suggests that magma mantle generated fluids have a role in the region high fluid pressure in branched fault zones weakened the faults making them sensitive to external disturbances and leading to fluid driven seismicity

seismology dynamic triggering of earthquakes the landers earthquake of 1992 triggered a series of earthquakes in other parts of california focusing attention on the mechanism of remote triggering laboratory experiments on granular material under pressure suggest that triggering is a result of seismic waves impinging on a fault and inducing elastic nonlinear behaviour of the fault core accompanied by instantaneous weakening and failure the resulting softening to weakening model fits in well with field observations of real earthquakes after an earthquake numerous smaller shocks are triggered over distances comparable to the dimensions of the mainshock fault rupture although they are rare at larger distances here we analyse the scaling of dynamic deformations the stresses and strains associated with seismic waves with distance from and magnitude of their triggering earthquake and show that they can cause further earthquakes at any distance if their amplitude exceeds several microstrain regardless of their frequency content these triggering requirements are remarkably similar to those measured in the laboratory for inducing dynamic elastic nonlinear behaviour which suggests that the underlying physics is similar1 2

crustal stress field in southern california and its implications for fault mechanics we present a new high spatial resolution image of stress orientation in southern california based on the inversion of earthquake focal mechanisms we use this image to study the mechanics of faulting in the plate boundary region the stress field contains significant spatial heterogeneity which in some cases appears to be a result of the complexity of faulting and in other cases appears to be a cause temporal changes in the stress field are also observed primarily related to major earthquakes the observed 15 10 rotation of the stress axes due to the 1992 m7 3 landers mainshock implies that the deviatoric stress magnitude in the crust is low of the order of 10 mpa this suggests that active faults in southern california are weak the maximum principal stress axis near the san andreas fault is often at 50 to the fault strike indicating that the shear stress on the fault is comparable to the deviatoric stress the san andreas in southern california may therefore be a weak fault in a low strength crust

slow dynamics in the nonlinear elastic response of berea sandstone a typical resonance curve measured accel eration versus drive frequency made on a thin bar of rock shows peak bending with a softening nonlinear modulus as drive levels are increased the shapes of these nonlinear resonance curves were found in earlier work to depend somewhat on sweep rate these slow dynamics are now examined and quantified we have measured slow dynamics in a 0 3 m long 50 mm diam eter bar of berea sandstone under ambient conditions peak strain levels during the experiments ranged from 10 to 10 at driving frequencies near 4 khz the fun damental longitudinal resonance frequency of the bar slow dynamics begin to manifest themselves at strain amplitudes above 10 a at ambient conditions and at the onset of nonlinear peak bending strains above this value condition the rock altering its response for min utes to hours after the drive has been turned off ter the pressure on the rock was changed the work presented here is the first to specifically document the slowly varying time response to periodic excitation i e slow dynamics of a berea sandstone sample moreover we demonstrate that the slow dynamics produce promi nent effects even at room conditions slow dynamics manifest themselves in a sandstone sample during high intensity longitudinal elastic reso nance we first report the effects of high strain on a sample by comparing conditioned resonance curves e g after the sample is driven at high intensity with a set of fully recovered curves e g after the sample is left untouched for a long period we illustrate that the first resonance curve made on a recovered sample differs remarkably from subsequent curves we present several results that illustrate aspects of the sample s memory and concludiwith a discussion of measurements to de termine how the rock recovers and to understand what

odp leg 107 in the tyrrhenian sea insights into passive margin and back arc basin evolution leg 107 of the ocean drilling program drilled a west northwest east southeast transect of seven sites across the tyrrhenian sea the youngest of the sub basins of the mediterranean sea sites 654 653 652 and 656 document the rifting and subsidence of the sardinia passive continental margin on the upper margin site 654 we cored a classic transgressive sequence subaerial conglomerates overlain by oyster bearing sands overlain by marine marl comparison between the recovered lithologies and seismic reflection profiles suggests that the synrift sediments on the upper margin are tortonian late miocene to messinian latest miocene in age whereas synrift sediments on the lower margin are messinian to pliocene in age during the messinian desiccation of the mediterranean sites 654 and 653 now on the upper sardinian margin apparently occupied a basinal setting where they received nannoplankton bearing clays interbedded with laminated gypsum sites 656 and 652 now on the lower sardinia margin were apparently higher standing during the desiccation event their messinian facies are subaerial and lacustrine respectively we infer from these lines of evidence that tilting and subsidence occurred more than a million years earlier on the upper margin than on the lower margin such diachroneity can be interpreted in terms of migration of the zone of maximum extension above a rolling back subduction zone or in terms of extension of continental crust by shear along a deep detachment fault sites 655 651 and 650 were drilled into two small basalt floored basins of the central and eastern tyrrhenian emplacement of basaltic crust in the central tyrrhenian vavilov basin apparently began more than a million years before emplacement of basaltic crust in the eastern tyrrhenian marsili basin this observation is compatible with previous suggestions that the tyrrhenian has grown southeastward in response to rollback of the down going slab that currently dips northwestward under the toe of italy at the easternmost site high vesicularity of the basalt and benthic foram assemblages in the oldest sediments imply that the basalt erupted in water shallower than 2 500 m it has apparently subsequently subsided to its present depth of 4 100 m below sea level nearly three times as fast as normal subsidence of crust formed at a mid ocean ridge

ultrafast oceanic spreading of the marsili basin southern tyrrhenian sea evidence from magnetic anomaly analysis spectral analysis of both shipborne and airborne magnetic maps of the southern tyrrhenian sea reveals seven subparallel positive negative magnetic anomaly stripes over the flat lying deep floor of the marsili oceanic basin this represents the first evidence of oceanic magnetic anomalies in the tyrrhenian sea the central positive stripe is along the marsili seamount a superinflated spreading ridge located at the basin axis the stratigraphy of ocean drilling program site 650 and k ar ages from the marsili seamount suggest that the marsili basin opened at the remarkable full spreading rate of 19 cm yr between ca 1 6 and 2 1 ma about the olduvai subchron this is the highest spreading rate ever documented including that observed at the cocos pacific plate boundary renewed but slow spreading during the brunhes chron after 0 78 ma coupled with huge magmatic inflation gave rise to the marsili volcano our new data and interpretation show that backarc spreading of the tyrrhenian sea was episodic with sudden rapid pulses punctuating relatively long periods of tectonic quiescence

palaeo shorelines of the historic period sant antioco island south western sardinia italy abstract this article illustrates the results of the recent multidisciplinary studies carried out in the southern part of sardinia western mediterranean sea on the last 2 5 ka palaeo sea level the survey has specifically investigated some geo archaeological sea level markers related to two submerged structures the first represents a near port building of punic roman age 2300 100 bp and is located in the sant antioco lagoon the second structure is a road of roman age 1030 20 bp in the near coastal area of palmas gulf a bone and ceramics fragment rich pericoastal beach rock chronologically referable to the imperial roman age between tiberius and claudius 1940 20 bp has been studied the results of this study fit the new predicted glacio hydro isostatic model of lambeck et al and agree with similar data from other sardinian sites that show almost no vertical tectonic mobility during the late holocene the study of a new stratigraphic section along the western coast of sant antioco island has identified the inner margin of a wave cut platform with fossils referred to mis 5 5 at 7 5 m highlighting a relative tectonic stability since the upper pleistocene for this area the geomorphological context of palmas gulf continental shelf shows a buried palaeo riverbed referred to mis 2 and a coastal palaeo system related to the holocene sea level change between 15 and 25 m these features are typical of the conservative style of low tectonic mobility areas