tsunami of december 26 2004 on the southwest coast of india post tsunami geomorphic and sediment characteristics this paper discusses the impact of the december 26 2004 tsunami on the geomorphic features and sediment characteristics along the southwest coast of india the data used include field observations made after the tsunami and the inferences drawn from the satellite imagery taken before and after the tsunami sediment samples collected from the inner shelf beach and estuarine environments were analyzed to understand post tsunami changes in grain size characteristics the tsunami eroded and transported landwards significant volumes of distinct black sands rich in heavy minerals from the shelf onto the beaches of the kerala region and up to 500 m inland of the present coast

the 2004 sumatra tsunami in the southeastern pacific ocean new global insight from observations and modeling the 2004 sumatra tsunami was an unprecedented global disaster measured throughout the world oceans the present study focused on a region of the southeastern pacific ocean where the westward circumferentially propagating tsunami branch converged with the eastward branch based on data from fortuitously placed chilean dart 32401 and tide gauges along the coast of south america by comparison of the tsunami and background spectra we suppressed the influence of topography and reconstructed coastal spectral ratios that were in close agreement with a ratio at dart 32401 and spectral ratios in other oceans findings indicate that even remote tsunami records carry spectral source signatures birth marks the 2004 tsunami waves were found to occupy the broad frequency band of 0 25 10 cph with the prominent ratio peak at period of 40 min related to the southern fast slip source domain this rupture hot spot of 350 km was responsible for the global impact of the 2004 tsunami data from dart 32401 provided validation of model results the simulated maximum tsunami wave height of 2 25 cm was a conservative approximation to the measured height of 2 05 cm the computed tsunami travel time of 25 h 35 min to dart 32401 although 20 min earlier than the actual travel time provided a favorable result in comparison with 24 h 25 min estimated from classical kinematic theory the numerical simulations consistently reproduced the wave height changes observed along the coast of south america including local amplification of tsunami waves at the northern stations of arica 72 cm and callao 67 cm

evaluation of tsunami risk from regional earthquakes at pisco peru we evaluate tsunami risk for the port city of pisco peru where major liquefied natural gas facilities are planned we use a compilation of instrumental and historical seismicity data to quantify the sources of six earthquakes that generated tsunamis resulting in minor inundation 1974 to catastrophic destruction 1687 1746 1868 in pisco for each of these case scenarios the seismic models are validated through hydrodynamic simulations using the most code which compute both flow depth on virtual offshore gauges located in pisco harbor and the distribution of runup in the port and along the nearby beach space time histories of major earthquakes along central and southern peru are used to estimate recurrence times of tsunamigenic earthquakes we conclude that pisco can expect a metric tsunami capable of inflicting substantial damage every 53 years and a dekametric tsunami resulting in catastrophic destruction of infrastructures every 140 years the last such event occurred 138 years ago an important result of our study is that total destruction of the city of pisco during the famous 1868 arica tsunami requires an earthquake rupture straddling the nazca ridge which thus constitutes at best an imperfect barrier for the propagation of rupture during megathrust events this gives a truly gigantic size to the 1868 arica earthquake with a probable seismic moment reaching 1030 dyne cm

observations and analysis of b type earthquakes explosions and volcanic tremor at pavlof volcano alaska an eight station network of short period seismometers has been operated near pavlof volcano 55 25 n 161 54 w alaska peninsula since 1976 high quality analog to digital and direct digital data were recorded during eruptions in 1980 through 1983 data are analyzed from explosions with distinct air phases b type volcanic earthquakes shallow low frequency events lacking clear s phases and volcanic tremor to determine source and propagation effects between zero and several hundred b type events and explosions per day are recorded with higher numbers during eruptions magnitudes range between 0 5 and 1 3 and b values range between 1 9 0 1 and 2 6 0 1 with no systematic relation to eruptive activity six results are most important 1 data from a recently installed three component station reveal that the highest amplitude waves of the b type events show retrograde elliptical particle motion and normal dispersion and are hence probably rayleigh waves 2 stacking of the events enhances the p wave which has a velocity of 3 1 0 1 km sec 1 3 the explosions and b type events have similar hypocenters as evidenced by signal characteristics and wave arrival times 4 the b type events contain virtually no high frequency energy even when allowing for attenuation effects in particular we estimate the anelastic attenuation coefficient q to have a value of 45 20 for rayleigh waves in the shallow part of the volcano 5 volcanic tremor spectra exhibit evenly spaced narrow peaks which we model as eigenvalues of organ pipe resonance in the magma conduit we estimate the length of the conduit to be a maximum of 1 6 km 6 the volcano shows evidence of extreme lateral variation of velocity and attenuation in its shallow structure

excitation of basin wide modes of the pacific ocean following the march 2011 tohoku tsunami this study is an attempt towards understanding the sources of long oscillations observed within the pacific ocean following the 11 march 2011 tohoku earthquake we present evidence that extremely long modes of the pacific ocean in the range of 2 48 h were excited by this giant tsunami a numerical approach was employed to calculate the basin wide modes of the pacific ocean resulting in 49 modes in the range of 2 48 h we studied 15 tide gauge records around the pacific ocean in order to extract basin wide modes of the pacific ocean excited by this transoceanic tsunami spectral analysis of these tide gauge records showed that some of the calculated basin wide modes were indeed excited by the tohoku tsunami the observed modes ranged from 2 to 49 8 h we attributed the long oscillations of the pacific ocean during the 2011 tohoku tsunami to the excitation of these basin wide modes which can be grouped into global modes 15 48 h and regional modes 2 15 h we classified the signals on the tide gauges into three groups 1 basin wide modes 1 5 h 2 the tsunami source periods 20 90 min and 3 local bathymetric effects 20 min the average contributions to the total tsunami energy were 6 4 for the basin wide mode 64 1 for the tsunami source and 29 5 for the local bathymetry although the ratios varied from station to station simulations suggest that the amount of contribution of basin effects to the total tsunami energy depends on the location of the tsunami source

depth dependent rupture mode along the ecuador colombia subduction zone a large earthquake mw 7 7 occurred on 16 april 2016 within the source region of the 1906 earthquake in the ecuador colombia subduction zone the 1906 event has been interpreted as a megathrust earthquake mw 8 8 that ruptured the source regions of smaller earthquakes in 1942 1958 and 1979 in this subduction our seismic analysis indicated that the spatial distribution of the 2016 earthquake and its aftershocks correlated with patches of high interplate coupling strength and was similar to those of the 1942 earthquake and its aftershocks suggesting that the 2016 and 1942 earthquakes ruptured the same asperity our analysis of tsunami waveforms of the 1906 event indicated mw around 8 4 and showed that large slip occurred near the trench off the source regions of the above three historical and the 2016 earthquakes suggesting that a depth dependent complex rupture mode exists along this subduction zone

source of the 1730 chilean earthquake from historical records implications for the future tsunami hazard on the coast of metropolitan chile historical records of an earthquake that occurred in 1730 affecting metropolitan chile provide essential clues on the source characteristics for the future earthquakes in the region the earthquake and tsunami of 1730 have been recognized as the largest to occur in metropolitan chile since the beginning of written history the earthquake destroyed buildings along 1000 km of the coast and produced a large tsunami that caused damage as far as japan here its source characteristics are inferred by comparing local tsunami inundations computed from hypothetical earthquakes with varying magnitude and depth with those inferred from historical observations it is found that a 600 800 km long rupture involving average slip amounts of 10 14 m mw 9 1 9 3 best explains the observed tsunami heights and inundations this large earthquake magnitude is supported by the 1730 tsunami heights inferred in japan the inundation results combined with local uplift reports suggest a southward increase of the slip depth along the rupture zone of the 1730 earthquake while shallow slip on the area to the north of the 2010 earthquake rupture zone is required to explain the reported inundation only deeper slip at this area can explain the coastal uplift reports since the later earthquakes of the region involved little or no slip at shallow depths the near future earthquakes on metropolitan chile could release the shallow slip accumulated since 1730 and thus lead to strong tsunami excitation moderate shaking from a shallow earthquake could delay tsunami evacuation for the most populated coastal region of chile 250 250

fault slip distribution of the 2014 iquique chile earthquake estimated from ocean wide tsunami waveforms and gps data we applied a new method to compute tsunami green s functions for slip inversion of the 1 april 2014 iquique earthquake using both near field and far field tsunami waveforms inclusion of the effects of the elastic loading of seafloor compressibility of seawater and the geopotential variation in the computed green s functions reproduced the tsunami traveltime delay relative to long wave simulation and allowed us to use far field records in tsunami waveform inversion multiple time window inversion was applied to tsunami waveforms iteratively until the result resembles the stable moment rate function from teleseismic inversion we also used gps data for a joint inversion of tsunami waveforms and coseismic crustal deformation the major slip region with a size of 100 km 40 km is located downdip the epicenter at depth 28 km regardless of assumed rupture velocities the total seismic moment estimated from the slip distribution is 1 24 1021 n m mw 8 0

high frequency tsunami signals of the great indonesian earthquakes of 26 december 2004 and 28 march 2005 tsunamis generated by the great indonesian earthquakes of 26 december 2004 m w 9 3 and 28 march 2005 m w 8 6 produced high frequency 5 mhz dispersed signals recorded by hydrophone stations offshore from diego garcia and cape leeuwin australia and by many seismic stations in the indian ocean and on the coast of antarctica for the first and greater earthquake the dispersed energy is commonly observed to 30 mhz and in one case to 60 mhz the high frequency signals are consistent with being generated at pointlike sources the earliest arriving tsunami signals originate from a point near 4 3 n 93 8 e determined using event to station distances estimated by matching predicted dispersion to observations the location is further constrained with azimuth estimates from an array of hydrophones fine structure in the tsunami signal indicates a second high frequency source just south of great nicobar island near 6 5 n 93 6 e the point sources are located close to the maximum slip area determined in several other seismic and tsunami studies the dispersion of much later arriving energy is consistent with travel over longer paths and matches predictions for reflections of the tsunami from bathymetric features in the indian ocean basin for the 28 march 2005 tsunami the high frequency dispersion is observed at the diego garcia hydrophone station and the ais seismic station and tsunami signals without apparent dispersion are seen at four other seismic stations phase velocities estimated at hydroacoustic stations agree with linear dispersion theory at frequencies above 12 mhz

fault slip and seismic moment of the 1700 cascadia earthquake inferred from japanese tsunami descriptions 1 the 1700 cascadia earthquake attained moment magnitude 9 according to new estimates based on effects of its tsunami in japan computed coseismic seafloor deformation for hypothetical ruptures in cascadia and tsunami modeling in the pacific ocean reports of damage and flooding show that the 1700 cascadia tsunami reached 1 5 m heights at seven shoreline sites in japan three sets of estimated heights express uncertainty about location and depth of reported flooding landward decline in tsunami heights from shorelines and post 1700 land level changes we compare each set with tsunami heights computed from six cascadia sources each source is vertical seafloor displacement calculated with a three dimensional elastic dislocation model for three sources the rupture extends the 1100 km length of the subduction zone and differs in width and shallow dip for the other sources ruptures of ordinary width extend 360 670 km to compute tsunami waveforms we use a linear long wave approximation with a finite difference method and we employ modern bathymetry with nearshore grid spacing as small as 0 4 km the various combinations of japanese tsunami heights and cascadia sources give seismic moment of 1 9 1022 n m equivalent to moment magnitude 8 7 9 2 this range excludes several unquantified uncertainties the most likely earthquake of moment magnitude 9 0 has 19 m of coseismic slip on an offshore full slip zone 1100 km long with linearly decreasing slip on a downdip partial slip zone the shorter rupture models require up to 40 m offshore slip and predict land level changes inconsistent with coastal paleoseismological evidence

hydrodynamic implications of textural trends in sand deposits of the 2004 tsunami in sri lanka abstract field observations and sediment samples at a coastal plain setting in southeastern sri lanka were used to document the erosional and depositional impacts of the 2004 indian ocean tsunami and to interpret the hydrodynamic processes that produced an extensive sand sheet deposit tsunami deposit thicknesses ranged from 6 to 22 cm with thickness being controlled partly by antecedent topography the deposit was composed of coarse to medium sand organized into plane parallel laminae and a few laminasets vertical textural trends showed an overall but non systematic upward fining and upward thinning of depositional units with an upward increase in heavy mineral laminations at some locations repeated patterns in the vertical textural trends upward fining upward coarsening uniform were used to subdivide and correlate the deposit into five hydro textural stratigraphic units the depositional units were linked to hydrodynamic processes and upcurrent conditions such as rates of sediment supply and composition of the sediment sources vertical changes in grain size distributions recorded the depositional phases associated with flow acceleration initial unsteady pulsating flow relatively stable and uniform flow flow deceleration slack water and return flow or flow redirection study results suggest that vertical textural trends from multiple cross shore sections can be used to interpret complex tsunami flow histories but at the location examined interpretation of the lateral textural trends did not provide a basis for identifying the correct sediment transport pathways because flow near the landward boundary was multidirectional

glacial isostatic adjustment i the forward problem summary the isostatic adjustment of a radially stratified visco elastic spheroid is treated using space time green functions for the associated surface mass load boundary value problem these impulse response functions are convolved with a heaviside function to give the time dependent deformation of the planet which would be produced by a unit point mass brought up from infinity at t 0 and allowed to remain on the surface the resulting heaviside green functions can be employed to simulate all of the important signatures of glacial isostatic adjustment given a space time dependent surface mass load consisting of ice sheet ablation histories and a model of the simultaneous filling of the ocean basins these source terms are simply convolved with the heaviside green function appropriate to a specific response signature a realistic model of the spatial distribution of the main late pleistocene ice loads and of their temporal disintegration is constructed the response of two visco elastic earth models is computed and compared to a global set of relaxation data relative sea level curves on the basis of this initial comparison of theory and observation the possibility that the lower mantle has a viscosity which is significantly in excess of the viscosity of the upper mantle is excluded in addition clear evidence of the presence of the lithosphere has been found in relaxation data from sites which were near the edge of the laurentide ice sheet such data should therefore prove useful as a basis for analysis of lateral variations in lithosphere thickness further extensions of the calculation are suggested

multi proxy evidence for trans pacific tsunamis in the hawai ian islands abstract the origin of two sand layers buried in polol wetland on the northeast coast of the island of hawai i was investigated using a multi proxy approach including radiometric dating sedimentology geochemistry micropalaeontology palynology and historical records based on 210 pb 137 cs and pollen data the lower sand unit extending 250 to 350 m inland is attributed to the 1946 aleutian tsunami while the upper sand unit was laid down by the 1957 aleutian tsunami chronological information does not appear to support any link between these deposits and historical storm events furthermore sedimentological geochemical diatom and pollen results suggest deposition of marine and near beach sediments under high energy conditions typically associated with tsunami inundation this work presents the first conclusive sedimentary evidence for distantly generated tsunamis on the hawai ian islands opening the way for more comprehensive historical and palaeotsunami studies indeed a brief review of archaeological data suggests that the hawai ian coast may have experienced similar large magnitude events in the past from both local and distant sources

tsunami heights along the pacific coast of northern honshu recorded from the 2011 tohoku and previous great earthquakes the 2011 tohoku earthquake generated a huge destructive tsunami with coastal heights of up to 40 m recorded along northern honshu the sanriku coast experienced similar tsunamis and damage from the 1896 and 1933 sanriku earthquakes whereas the only damaging tsunamis on both the ibaraki and chiba coasts in the previous century were from the 1960 and 2010 chile earthquakes we summarized 12 field surveys in which the height of the 2011 tsunami was recorded at 296 points along with descriptions of the survey method reliability and accuracy we then compared them with the above mentioned tsunamis at locations for which specific measurements were given in previous reports on the sanriku coast the 2011 tsunami heights are positively correlated with the previous sanriku tsunamis indicating that local variations resulting from the irregular coastline were more dominant factors than the earthquake location type or magnitude for near field tsunamis the correlations with the chilean tsunami heights are less significant due to the differences between the local and trans pacific tsunamis on the ibaraki and chiba coasts the 2011 tohoku and the two chilean tsunami heights are positively correlated showing the general decrease toward the south with small local variations such as large heights near peninsulas

distribution origin and transport process of boulders deposited by the 2004 indian ocean tsunami at pakarang cape thailand abstract the tsunami of 2004 in the indian ocean transported thousands of meters long boulders shoreward at pakarang cape thailand we investigated size position and long axis orientation of 467 boulders at the cape most of boulders found at the cape are well rounded ellipsoid in shape without sharp broken edges they were fragments of reef rocks and their sizes were estimated to be 3 22 7t the distribution pattern and orientation of long axis of boulders reflect the inundation pattern and behavior of the tsunami waves it was found that there is no clear evidence indicating monotonous fine coarse shoreward trends of these boulders along each transect line on the other hand the large boulders were deposited repeatedly along the three arcuate lines at the intertidal zone with a spacing of approximately 136m interval this distribution pattern may suggest that long lasting oscillatory flows might have repositioned the boulders and separated the big ones from small no boulders were found on land indicating that the hydraulic force of the tsunami wave rapidly dissipated on reaching the land due to the higher bottom friction and the presence of a steep slope we further conducted numerical calculation of tsunami inundation at pakarang cape according to the calculation the sea receded and the major part of the tidal bench area with boulders at present was exposed above the sea surface before the arrival of the first tsunami wave the first tsunami wave arrived at the cape from west to east at approximately 130min after the tsunami generation and then inundated inlands our calculation shows that tsunami wave was focused around the offshore by a small cove at the reef edge and spread afterwards in a fan like shape on the tidal bench the critical wave velocities necessary to move the largest and average size boulders by sliding can be estimated to be approximately 3 2 and 2 0m s respectively the numerical result indicates that the maximum current velocity of the first tsunami wave was estimated to be from 8 to 15m s between the reef edge and approximately 500m further offshore this range is large enough for moving even the largest boulder shoreward these suggest that the tsunami waves that were directed eastward struck the reef rocks and coral colonies originally located on the shallow sea bottom near the reef edge and detached and transported the boulders shoreward

the 1964 prince william sound earthquake joint inversion of tsunami and geodetic data the 1964 prince william sound alaska earthquake mw 9 2 ruptured a large area beneath the continental margin of alaska from prince william sound to kodiak island a joint inversion of tsunami waveforms and geodetic data consisting of vertical displacements and horizontal vectors gives a detailed slip distribution two areas of high slip correspond to seismologically determined areas of high moment release the prince william sound asperity with average slip of 18 m and the kodiak asperity with average slip of 10 m the average slip on the fault is 8 6 m and the seismic moment is estimated as 6 3 1022 n m or over 75 of the seismic moment determined from long period surface waves

shelf resonance and impact of near field tsunami generated by the 2010 chile earthquake 1 the 2010 chile earthquake of mw 8 8 generated a destructive tsunami in the near field that resulted in warnings across the pacific numerical modeling shows trapping and amplification of the energy over the continental shelf and slope a spectral analysis of the computed surface elevation reveals resonance oscillations with periods up to 129 min along the central chile coast the temporal and spectral data provides an explanation for the long period waves recorded by dart buoys and the prolonged wave activities and belated impacts reported by residents and survey teams the present study of the 2010 chile tsunami together with those of the 2006 kuril and 2009 samoa tsunamis has directly associated shelf resonance with impacts on insular and continental coasts and provided a tool to identify at risk localities in tsunami hazard assessment

global frequency of magnitude 9 earthquakes for decades seismologists have sought causal relationships between maximum earthquake sizes and other properties of subduction zones with the underlying notion that some subduction zones may never produce a magnitude 9 or larger event the 2004 andaman m w 9 2 earthquake called into question such ideas given multicentury return times of the greatest earthquakes ignorance of those return times and our very limited observation span i suggest that we cannot yet make such determinations present evidence cannot rule out that any subduction zone may produce a magnitude 9 or larger earthquake based on theoretical recurrence times i estimate that one to three m9 earthquakes should occur globally per century and the past half century with five m9 events reflects temporal clustering and not the long term average

gradual unlocking of plate boundary controlled initiation of the 2014 iquique earthquake a long foreshock series unlocked the south american plate boundary until eventually initiating the m 8 1 iquique chile earthquake two groups publishing in this issue of nature analyse the seismic context of the iquique earthquake that occurred off the coast of northern chile on 1 april 2014 in a seismic zone that had been quiescent since a significant event in 1877 gavin hayes et al identify areas of remaining or elevated earthquake hazard along the megathrust fault in the region and conclude that the 2014 iquique event was not the earthquake that had been anticipated given that significant sections of the northern chile subduction zone have not ruptured in almost 150 years they suggest that it is likely that future megathrust earthquakes will occur south and potentially north of the 2014 iquique sequence bernd schurr et al show that the april 2014 earthquake broke a central fraction of the northern chile seismic gap the last major segment of the south american plate boundary that had yet to rupture in the past century from july 2013 up to the april earthquake they identify three seismic clusters along this part of the plate boundary each lasting a few weeks with earthquakes of increasing peak magnitudes they conclude that these seismic clusters and their slip transients reflect a gradual weakening of the central part of the seismic gap that was instrumental in initiating the final failure on 1 april 2014 northern chile was struck by a magnitude 8 1 earthquake following a protracted series of foreshocks the integrated plate boundary observatory chile monitored the entire sequence of events providing unprecedented resolution of the build up to the main event and its rupture evolution here we show that the iquique earthquake broke a central fraction of the so called northern chile seismic gap the last major segment of the south american plate boundary that had not ruptured in the past century1 2 since july 2013 three seismic clusters each lasting a few weeks hit this part of the plate boundary with earthquakes of increasing peak magnitudes starting with the second cluster geodetic observations show surface displacements that can be associated with slip on the plate interface these seismic clusters and their slip transients occupied a part of the plate interface that was transitional between a fully locked and a creeping portion leading up to this earthquake the b value of the foreshocks gradually decreased during the years before the earthquake reversing its trend a few days before the iquique earthquake the mainshock finally nucleated at the northern end of the foreshock area which skirted a locked patch and ruptured mainly downdip towards higher locking peak slip was attained immediately downdip of the foreshock region and at the margin of the locked patch we conclude that gradual weakening of the central part of the seismic gap accentuated by the foreshock activity in a zone of intermediate seismic coupling was instrumental in causing final failure distinguishing the iquique earthquake from most great earthquakes finally only one third of the gap was broken and the remaining locked segments now pose a significant increased seismic hazard with the potential to host an earthquake with a magnitude of 8 5

geological and historical evidence of irregular recurrent earthquakes in japan great m 8 earthquakes repeatedly occur along the subduction zones around japan and cause fault slip of a few to several metres releasing strains accumulated from decades to centuries of plate motions assuming a simple characteristic earthquake model that similar earthquakes repeat at regular intervals probabilities of future earthquake occurrence have been calculated by a government committee however recent studies on past earthquakes including geological traces from giant m 9 earthquakes indicate a variety of size and recurrence interval of interplate earthquakes along the kuril trench off hokkaido limited historical records indicate that average recurrence interval of great earthquakes is approximately 100 years but the tsunami deposits show that giant earthquakes occurred at a much longer interval of approximately 400 years along the japan trench off northern honshu recurrence of giant earthquakes similar to the 2011 tohoku earthquake with an interval of approximately 600 years is inferred from historical records and tsunami deposits along the sagami trough near tokyo two types of kanto earthquakes with recurrence interval of a few hundred years and a few thousand years had been recognized but studies show that the recent three kanto earthquakes had different source extents along the nankai trough off western japan recurrence of great earthquakes with an interval of approximately 100 years has been identified from historical literature but tsunami deposits indicate that the sizes of the recurrent earthquakes are variable such variability makes it difficult to apply a simple characteristic earthquake model for the long term forecast and several attempts such as use of geological data for the evaluation of future earthquake probabilities or the estimation of maximum earthquake size in each subduction zone are being conducted by government committees

the orphan tsunami of 1524 on the konkan coast western india and its implications in comparison to the east coast the tsunami hazard for the west coast of india remains under recognized despite the impact in 1945 following a mw 8 1 earthquake in the makran subduction zone in the northern arabian sea the previous occurrences of tsunamis in the arabian sea that would have a bearing on the west coast of india are being debated including the question whether the makran region has the potential to generate greater magnitude earthquakes with this in the backdrop we present here the historical and geological evidence of a tsunami impact zone from a site on the konkan coast of western india located in the village of kelshi the impact zone is preserved within a coastal dune complex that also reveals occupation layers this laterally extending 30 40 cm thick zone coinciding with a habitation level displays varied sedimentary structures including scour fill features and is inter layered with shells at a height of 3 m from the high tide level we attribute these sedimentary features to a tsunami flooding event that was contemporaneous with the transportation of shells dated at 1508 1681 ce the geological inference matches with the description by the portuguese fleets of a sea disturbance in 1524 ce reported from dabhol not far from kelshi and also from the gulf of cambay located about 500 km to the north precluding submarine landslide scenarios the modeling results suggest that the high impact in kelshi could have been generated by a mw 9 earthquake sourced in the makran subduction zone it is however intriguing how a mw 9 earthquake in the makran region finds no mention in the historical documentation we underscore the need for fresh efforts along the makran coast to reconstruct the tsunami recurrence history that would generate required validating constraints on the 1524 event if it was indeed generated by a massive earthquake among other mechanisms

assessment of the size of large and great historical earthquakes in peru a critical reappraisal of great historical earthquakes in peru is made in order to obtain quantitative estimates of rupture length seismic moment tsunami magnitude mt and moment magnitude mw newly collected information concerning several historical earthquakes permits the evaluation of macroseismic zones and from the size of these zones the estimation of length of rupture seismic moment and magnitude mw it is found that local tsunami data provide good quantitative estimates of mt and therefore an independent way of verifying macroseismic estimates of rupture length and seismic moment a space time diagram of great historical earthquakes shows the existence of three zones roughly corresponding to the segmentation of the nazca plate hasegawa and sacks 1981 subducting under peru the northern zone looks aseismic the central one is very complex it breaks either completely or in smaller segments and it may go through long quiescence periods the recurrence time for the southern segment the more regular one is of the order of one century

reexamination of the magnitudes for the 1906 and 1922 chilean earthquakes using japanese tsunami amplitudes implications for source depth constraints far field tsunami records from the japanese tide gauge network allow the reexamination of the moment magnitudes mw for the 1906 and 1922 chilean earthquakes which to date rely on limited information mainly from seismological observations alone tide gauges along the japanese coast provide extensive records of tsunamis triggered by six great mw 8 chilean earthquakes with instrumentally determined moment magnitudes these tsunami records are used to explore the dependence of tsunami amplitudes in japan on the parent earthquake magnitude of chilean origin using the resulting regression parameters together with tide gauge amplitudes measured in japan we estimate apparent moment magnitudes of mw 8 0 8 2 and mw 8 5 8 6 for the 1906 central and 1922 north central chile earthquakes the large discrepancy of the 1906 magnitude estimated from the tsunami observed in japan as compared with those previously determined from seismic waves ms 8 4 suggests a deeper than average source with reduced tsunami excitation a deep dislocation along the chilean megathrust would favor uplift of the coast rather than beneath the sea giving rise to a smaller tsunami and producing effects consistent with those observed in 1906 the 1922 magnitude inferred from far field tsunami amplitudes appear to better explain the large extent of damage and the destructive tsunami that were locally observed following the earthquake than the lower seismic magnitudes ms 8 3 that were likely affected by the well known saturation effects thus a repeat of the large 1922 earthquake poses seismic and tsunami hazards in a region identified as a mature seismic gap

tsunami coda across the pacific ocean following the 2011 tohoku oki earthquake abstract a tsunami coda lasting more than 5 days was clearly recorded across the pacific ocean following the 2011 tohoku oki earthquake we found that the coda energy per unit area elapsed time of 60 96 hr from the earthquake origin time does not show a systematic variation with respect to the travel distance at the stations located at sea depths deeper than 2000 m whereas the maximum amplitude near the source is significantly larger than those of the far field stations this feature is similar to that of a seismic coda in the sense that the coda energy is distributed uniformly in space the average tsunami coda decays with a decay time of 24 hr when we carefully examined the tsunami waveform near japan a large amplitude wave was identified at an elapsed time of 48 hr which corresponds to the round trip travel time for waves reflected from chile to investigate the excitation mechanisms of the tsunami coda we conducted a tsunami simulation using a global model although linear long wave tsunami equations were found to overestimate the observed coda amplitude the equations including an intrinsic energy loss could successfully simulate the observed coda decay if a bottom friction coefficient of 10 5 was assumed this indicates that not only wave scattering but also intrinsic energy loss plays an important role in the tsunami coda excitation and decay process

fine structure of the dipping seismic zone and subduction mechanics in the shumagin islands alaska microearthquake data from a permanent telemetered array have been used to elucidate the structure and tectonics of the subduction zone in the shumagin islands alaska the shallow microseismicity is characterized by active interplate thrusting in the 25 45 km depth range arcward of this interplate activity microearthquakes in the overlying plate have a strike slip mechanism the near horizontal p axis of this mechanism is oriented in the direction of plate convergence suggesting that the plate interface at shallow depths is currently efficiently coupled below 45 km depth the dipping seismic zone appears to be double planed the upper plane dips at 32 from 45 to 100 km depth where it exhibits a kneelike bend below the volcanic front the lower plane begins at about 65 km depth where it is separated from the upper plane by some 25 km and appears to converge with the upper plane at about 120 km depth the inferred geometry of the plate interface suggests that the double planed portion of the dipping seismic zone is a product of elastic unbending of the subducted plate a composite fault plane solution for events in the upper plane indicates however that downdip tension is currently present rather than the downdip compression that would be expected from unbending it is proposed that because of locking of the plate interface at shallower depths slab pull is currently overprinting the unbending stresses which predominate at times when the plates are unlocked this model is consistent with previous interpretations that there is a high probability of a great earthquake in the shumagin islands seismic gap within the next decade or two

estimation of seismic moment and slip distribution of the april 1 1946 aleutian tsunami earthquake the 1946 aleutian earthquake produced a tsunami of tsunami magnitude mt 9 3 but the surface wave magnitude is only ms 7 4 making it a tsunami earthquake the discrepancy between the apparent size of the earthquake based on the seismic data and the size of the tsunami has been explained by several mechanisms including a landslide and a slow earthquake but there are few seismic data available to determine the correct mechanism we study the generating mechanism of the tsunami using tsunami waveforms recorded on tide gauges we have modeled the source of the 1946 aleutian tsunami as the result of an underthrusting earthquake we performed both forward and inverse modeling of the data using a finite difference calculation to compute synthetic tsunamis we include both vertical and horizontal deformation of the ocean bottom due to faulting in the computation the results of the inversion of the tsunami waveforms show that the slip on the fault is mainly concentrated in the shallow section of the fault near the epicenter there is little slip in the area of the aftershocks indicating that the aftershocks may represent an area of afterslip or triggered seismicity the moment estimate of the earthquake is 23 1020 n m or mw 8 2 the majority of the waveforms are well explained by this fault model and slip distribution including the honolulu waveform but the hawaiian data also suggest that other effects such as a landslide may be necessary for explaining the abnormal tsunami amplitudes in hawaii the 1946 earthquake is similar to other tsunami earthquakes such as the 1896 sanriku and 1992 nicaragua earthquakes indicating that slow shallow rupture may explain the disproportionally large tsunamis

traveltime delay and initial phase reversal of distant tsunamis coupled with the self gravitating elastic earth systematic tsunami traveltime delays of up to 15 min relative to the numerically simulated long waves from the 2010 chilean and 2011 tohoku oki earthquakes were widely observed at deep ocean tsunamimeters enigmatic small negative phases appearing before the main peak were commonly found only at the trans oceanic locations the frequency dependence of the measured tsunami phase velocities shows reverse dispersions at long periods i e the tsunami speed becomes slower at periods beyond 1000 s this is consistent with the phase velocities of a tsunami mode coupled with a self gravitating elastic earth suggesting that the effects of compression and dilatation of seawater elastic tsunami loadings on a solid earth and the geopotential variations associated with the motion of mass during tsunami propagation are responsible for the traveltime delays and the initial negative phases simple 1 d tsunami propagation tests confirm that the reverse dispersion creates a small negative phase that precedes the main peak at large distances a new method to simulate tsunami waveforms on real ocean bathymetry that takes into account seawater compressibility the elasticity of the earth and geopotential perturbations has been developed by applying a phase correction to the simulated long waves the simulated waveforms in which phase corrections are applied for the dispersion effects accurately reproduce the observed waveforms including a small initial negative phase that appears at distant locations the traveltime difference between the observed and simulated waveforms has been decreased to less than 5 min and the waveform difference between them remarkably diminishes

edge wave and non trapped modes of the 25 april 1992 cape mendocino tsunami the 25 april 1992 cape mendocino earthquake generated a tsunami characterized by both coastal trapped edge wave and non trapped tsunami modes that propagated north and south along the u s west coast both observed and synthetic time series at crescent city and north spit are consistent with the zero order edge wave mode solution for a semi infinite sloping beach depth profile wave amplitudes at crescent city were about twice that observed at north spit in spite of the fact that the source region was three times farther from crescent city than north spit the largest observed amplitude was due to an edge wave which arrived almost three hours after the initial onset of the tsunami since such waves are highly localized nearshore this suggests that the enhanced responsiveness at crescent city is at least partly due to local dynamic processes furthermore the substantially delayed arrival of this wave which was generated at the southern end of the cascadia subduction zone has significant implications for hazard mitigation efforts along the entire u s west coast specifically this study demonstrates that slow moving but very energetic edge wave modes could be generated by future large tsunamigenic earthquakes in the csz and that these might arrive unexpectedly at coastal communities several hours after the initial tsunami waves have subsided

five great tsunamis of the 20th century as recorded on the coast of british columbia the five great trans pacific tsunamis of the 20th century that occurred in 1946 1952 1957 1960 and 1964 were accurately recorded by analogue tide gauges on the coast of british columbia all available pen and paper records of these events were collected digitised de tided and analysed the 1946 aleutian islands event was recorded at two stations tofino and victoria where maximum trough to crest tsunami wave heights were 55 and 27 cm respectively these two gauged stations as well as prince rupert alert bay and kitimat also recorded the 1952 kamchatka tsunami which generated a maximum wave height of 77 cm at tofino the 1957 andreanof islands tsunami was recorded at six primary stations and the 1960 chile tsunami by 17 primary and temporary tide gauges for both of these events the maximum tsunami wave heights also occurred at tofino 48 cm 1957 and 132 cm 1960 the 1964 alaska tsunami remains the strongest tsunami yet instrumentally recorded on the coast of british columbia our examination of 16 records from this event shows that maximum wave heights at eight stations were higher than 1 m including port alberni 770 cm ocean falls 376 cm tofino 237 cm and alert bay 222 cm we also find that the maximum wave at all stations for this event was among the first three waves subsequent wave heights rapidly attenuated following this group of waves frequency time f t analyses of the tsunami waveforms reveal that for each station the dominant frequencies of the waves and their evolution with time were very similar for different tsunamis but differed considerably among sites for a particular tsunami indicating the strong influence of local regional topography on the incoming waves from the latter point of view the 1964 tsunami was exceptional the epicentre of the 1964 alaska earthquake was located much closer to the bc coast than for the other events and therefore the influence of the source was much stronger the ringing of this tsunami was substantially shorter 1 5 days the energy decay much faster and the f t diagrams at all sites more similar than for the other major events during the 1964 event energy associated with the dominant period of 2 h rapidly decayed all of the tsunamis examined penetrated deep inside the narrow channels fjords and inlets typical of the bc coast waves also propagated far into some of the rivers the 1952 kamchatka tsunami was recorded at kitimat located at the head of kitimat arm about 80 km from hecate strait while the 1957 andreanof islands tsunami was measured at bella coola located at the remotest part of burke channel a distance of 110 km from the open ocean queen charlotte sound the 1960 chile tsunami was recorded at five stations located in the complex network of inlets and channels that make up the seymour belize inlet system on the central mainland coast of british columbia while the 1964 alaska tsunami was observed at many stations in the fraser river including pitt lake that is connected to the strait of georgia through a 64 km route upstream in the fraser and pitt rivers our results further show that occasionally the fjords and inlets of the bc coast not only do not hinder the incoming waves but can strongly enhance them through resonant amplification this was the case for the 1964 tsunami waves in alberni inlet where the resonant response to the incoming waves resulted in severe damage to port alberni at the head of the inlet the results of our analyses make it possible to isolate the tsunami signal and evaluate the principal parameters of tsunami waves this in turn is of considerable value for three major problems 1 cataloguing of tsunami events 2 estimation of the potential tsunami risk to the bc coast and 3 verification and calibration of numerical tsunami models

tohoku earthquake a surprise abstract we consider three questions related to the 2011 tohoku mega earthquake 1 why was the event size so grossly underestimated by japan s national hazard map 2 how should we evaluate the chances of giant earthquakes in subduction zones 3 what is the repeat time for magnitude 9 earthquakes off the tohoku coast the maximum earthquake size is often guessed from the available history of earthquakes a method known for its significant downward bias we show that historical magnitudes systematically underestimate this maximum size of future events but the discrepancy shrinks with time there are two quantitative methods for estimating the corner magnitude in any region a statistical analysis of the available earthquake record and the moment conservation principle however for individual zones the statistical method is usually ineffective in estimating the maximum magnitude only the lower limit can be evaluated the moment conservation technique which we prefer matches the tectonic deformation rate to that predicted by earthquakes with a truncated or tapered magnitude frequency distribution for subduction zones the seismic or historical record is insufficient to constrain either the maximum or corner magnitude however the moment conservation principle yields consistent estimates for all the subduction zones the corner magnitude is of the order 9 0 9 7 moreover moment conservation indicates that variations in estimated corner magnitude among subduction zones are not statistically significant another moment conservation method applied at a point on a major fault or plate boundary also suggests that magnitude 9 events are required to explain observed displacement rates at least for the tohoku area the global rate of magnitude 9 earthquakes in subduction zones predicted from statistical analysis of seismicity as well as from moment conservation is about five per century five actually happened

long term perspectives on giant earthquakes and tsunamis at subduction histories of earthquakes and tsunamis inferred from geological evidence aid in anticipating future catastrophes this natural warning system now influences building codes and tsunami planning in the united states canada and japan particularly where geology demonstrates the past occurrence of earthquakes and tsunamis larger than those known from written and instrumental records under favorable circumstances paleoseismology can thus provide long term advisories of unusually large tsunamis the extraordinary indian ocean tsunami of 2004 resulted from a fault rupture more than 1000 km in length that included and dwarfed fault patches that had broken historically during lesser shocks such variation in rupture mode known from written history at a few subduction zones is also characteristic of earthquake histories inferred from geology on the pacific rim

the 26 december 2004 sumatra tsunami analysis of tide gauge data from the world ocean part 1 indian ocean and south africa the m w 9 3 megathrust earthquake of december 26 2004 off the northwest coast of sumatra in the indian ocean generated a catastrophic tsunami that was recorded by a large number of tide gauges throughout the world ocean part 1 of our study of this event examines tide gauge measurements from the indian ocean region at sites located from a few hundred to several thousand kilometers from the source area statistical characteristics of the tsunami waves including wave height duration and arrival time are determined along with spectral properties of the tsunami records

the global reach of the 26 december 2004 sumatra tsunami numerical model simulations combined with tide gauge and satellite altimetry data reveal that wave amplitudes directionality and global propagation patterns of the 26 december 2004 sumatra tsunami were primarily determined by the orientation and intensity of the offshore seismic line source and subsequently by the trapping effect of mid ocean ridge topographic waveguides

improved phase corrections for transoceanic tsunami data in spatial and temporal source estimation application to the 2011 tohoku earthquake systemic travel time delays of up to 15 min relative to the linear long waves for transoceanic tsunamis have been reported a phase correction method which converts the linear long waves into dispersive waves was previously proposed to consider seawater compressibility the elasticity of the earth and gravitational potential change associated with tsunami motion in the present study we improved this method by incorporating the effects of ocean density stratification actual tsunami raypath and actual bathymetry the previously considered effects amounted to approximately 74 for correction of the travel time delay while the ocean density stratification actual raypath and actual bathymetry contributed to approximately 13 4 and 9 on average respectively the improved phase correction method accounted for almost all the travel time delay at far field stations we performed single and multiple time window inversions for the 2011 tohoku tsunami using the far field data 3 h travel time to investigate the initial sea surface displacement the inversion result from only far field data was similar to but smoother than that from near field data and all stations including a large sea surface rise increasing toward the trench followed by a migration northward along the trench for the forward simulation our results showed good agreement between the observed and computed waveforms at both near field and far field tsunami gauges as well as with satellite altimeter data the present study demonstrates that the improved method provides a more accurate estimate for the waveform inversion and forward prediction of far field data

determination of large scale velocity structure of the crust and upper mantle in the vicinity of pavlof volcano alaska pavlof volcano is a 2715 m high stratovolcano located at latitude 55 4 n and longitude 161 9 w near the western end of the alaska peninsula in this study the large scale lateral perturbations to a vertical reference velocity structure in the vicinity of pavlof volcano are determined using modified versions of standard three dimensional inversion techniques we use as the primary data set p wave arrival times and residuals from shallow 40 km deep regional earthquakes located by the shumagin islands seismic network relative residuals mainly from refracted e g pn arrivals allow us to constrain models for a laterally varying crustal velocity structure several strong ray path dependent patterns are seen in the residuals the most pronounced is that rays passing through the crust beneath the volcano are delayed positive residuals by up to 1 0 s while those rays traveling subparallel to and behind the volcanic axis on the retroarc bering sea side arrive as much as 0 5 s early negative residuals the corresponding results of a formal velocity inversion show the presence of a lowvelocity body beneath the volcanic arc that coincides geographically with emmons caldera 10 km sw of pavlof computed velocity values are about 12 14 lower than in the surrounding crust and are comparable to values found at other volcanic areas the exact shape and position of the low velocity body and its suitability for geothermal power development have not yet been sufficiently determined for such an assessment a much denser station distribution is required

the 1957 great aleutian earthquake the 9 march 1957 aleutian earthquake has been estimated as the third largest earthquake this century and has the longest aftershock zone of any earthquake ever recorded 1200 km however due to a lack of high quality seismic data the actual source parameters for this earthquake have been poorly determined we have examined all the available waveform data to determine the seismic moment rupture area and slip distribution these data include body surface and tsunami waves using body waves we have estimated the duration of significant moment release as 4 min from surface wave analysis we have determined that significant moment release occurred only in the western half of the aftershock zone and that the best estimate for the seismic moment is 50 100 1020 nm using the tsunami waveforms we estimated the source area of the 1957 tsunami by backward propagation the tsunami source area is smaller than the aftershock zone and is about 850 km long this does not include the unalaska island area in the eastern end of the aftershock zone making this area a possible seismic gap and a possible site of a future large or great earthquake we also inverted the tsunami waveforms for the slip distribution slip on the 1957 rupture zone was highest in the western half near the epicenter little slip occurred in the eastern half the moment is estimated as 88 1020 nm or m w 8 6 making it the seventh largest earthquake during the period 1900 to 1993 we also compare the 1957 earthquake to the 1986 andreanof islands earthquake which occurred within a segment of the 1957 rupture area the 1986 earthquake represents a rerupturing of the major 1957 asperity

history and features of trans oceanic tsunamis and implications for paleo tsunami studies abstract far field tsunamis and their features as well as methods to quantify trans oceanic tsunamis are reviewed with examples of instrumental and historical data tsunamis from the 1854 nankai earthquakes the 1946 aleutian tsunami earthquake the 1960 and 2010 chile earthquakes as well as the 2011 tohoku earthquake were recorded around the pacific ocean the 1883 krakatoa volcanic eruption caused volcanic tsunami in the indian ocean and meteotsunami in the pacific ocean the 2004 indian ocean tsunami was also recorded in the pacific ocean when a tsunami amplitude is larger than that of ocean tides which usually requires the parent earthquake to be gigantic mw 9 it can cause damage and may be historically documented the trans pacific tsunamis described in historical documents include those from the 1700 cascadia earthquake the 1730 1751 1837 and 1877 earthquakes off chile and the 1687 and 1868 earthquakes off peru the tsunami record in japan from the 1586 peru earthquakes was found to be incorrect and should be discounted the tsunami magnitude scale relates the tsunami heights to the earthquake size tsunami travel time can be computed from actual bathymetry and the tsunami ray tracing provides relative amplitudes due to focusing defocusing caused by irregular bathymetry numerical computations from fault models produce tsunami amplitudes and waveforms and indicate strong directivity due to strike of fault or orientation of subduction zones far field tsunamis are often long lasting due to multiple reflections across the basin or on continental shelf or due to resonance in bays harbors these features would provide important criteria to estimate tsunami sources from paleo tsunami data

waveform and spectral analyses of the 2011 japan tsunami records on tide gauge and dart stations across the pacific ocean we studied the 11 march 2011 tohoku tsunami through analysis of the sea level records from 21 tide gauge and 16 dart deep ocean assessment and reporting of tsunamis stations from across the pacific ocean the extreme power of this trans oceanic tsunami was indicated by the trough to crest heights of 3 03 m at arena cove on the western coast of the usa and 3 94 m at coquimbo on the southern coast of chile the average value of the maximum amplitude was 163 9 cm for the examined tide gauge records at many coastal tide gauge stations the largest wave arrived several hours after the first arrival of the tsunami wave and the tsunami lasted for a long time with an average duration of 4 days on the contrary at most of the dart stations in the deep ocean the first wave was the largest the tsunami amplitudes were smaller with an average maximum of 51 2 cm and the durations were shorter with an average of 2 days the two dominant tsunami periods on the dart records were 37 and 67 4 min which are possibly attributed to the width and length of the tsunami source fault respectively the dimensions of the tsunami source was estimated as 233 km 424 km wavelet analyses of tide gauge and dart records showed that most of the tsunami energy was distributed at the wide period band of around 10 80 min during the first hour after the tsunami arrival then it was concentrated in a relatively narrower band the frequency time plots showed the switches and lapses of tsunami energy at the 35 and 65 min period bands

effects of bathymetry on tsunami propagation application of ray tracing to tsunamis ray tracing of seismic surface waves is applied to tsunami propagation to examine bathymetric effect along its propagation path computations are made for trans pacific tsunamis and for near field tsunamis in the japan sea for tsunamis across the pacific ocean the comparison to a uniform ocean shows that focusing and defocusing due to bathymetry are significant for some combinations of source and receiver for example the refraction of rays is predominant at the east pacific rise for the tsunami from chile the tsunamis in the japan sea are strongly affected by the shallow yamato rise the predicted arrival time and amplitude distribution generally agree with the observations from an actual tsunami since the computation can be made very quickly the method is useful for preliminary analysis of tsunami propagation such as in an operational warning system or in the determination of computational area for finite difference computation

seismic monitoring of the indian ocean tsunami the 26 december 2004 sumatra andaman earthquake of mw 9 3 triggered a massive tsunami in the indian ocean we here report on observations of the indian ocean tsunami at broadband seismic stations located on islands in the area the tsunami induces long period 1000 s signals on the horizontal components of the sensor frequency time analysis shows that the long period signals cannot be due to seismic surface waves but that it arrives at the expected time of the tsunami the waveforms are well correlated to tide gauge observations at a location where both observations are available to explain the signals we favour tilt due to coastal loading but we cannot at the present stage exclude gravitational effects the density of broadband stations is expected to increase rapidly in the effort of building an earthquake monitoring system they may unexpectedly become useful tsunami detectors as well

source model of the 16 september 2015 illapel chile m w 8 4 earthquake based on teleseismic and tsunami data teleseismic data were provided by the incorporated research institutions for seismology http www iris edu wilber3 find event tide gauge data can be found at the intergovernmental oceanographic commission website http www ioc sealevelmonitoring org dart records were provided by noaa http nctr pmel noaa gov dart earthquake catalogs by the usgs national earthquake information center http earthquake usgs gov earthquakes search and global instrumental earthquake catalogue 1900 2009 of international seismological centre global earthquake model http www globalquakemodel org what seismic hazard instrumental catalogue were used in this study we used the gmt software for drawing the figures wessel and smith 1998 this article benefited from constructive review comments by costas e synolakis university of southern california usa and yuichiro tanioka hokkaido university japan for which we are grateful we acknowledge financial supports from the japan society for the promotion of science

time and size of a giant earthquake in cascadia inferred from japanese tsunami records of january 1700 geological evidence shows that great earthquakes have occurred in the recent prehistoric past in the cascadia subduction zone off the pacific coast of north america the most recent event or series of events is dated at about 300 years ago1 4 but the precise date and magnitude have not been determined geological investigations have not been able to distinguish a single giant earthquake from a series of great earthquakes occurring over a timespan of a decade or two4 although this information is important for the assessment of future hazard5 we have found several tsunami records in japan from ad 1700 with no indication of a local cause historical earthquake records and palaeoseismic evidence indicate the absence of a large earthquake in 1700 in south america alaska or kamchatka leaving cascadia as the most likely source of this tsunami the estimated time of the earthquake is the evening about 21 00 local time of 26 january 1700 the magnitude is estimated as 9 from the tsunami heights in which case the earthquake ruptured the entire length of the cascadia subduction zone2 these estimates are consistent with native american legends that an earthquake occurred on a winter night6

magnitude limits of subduction zone earthquakes maximum earthquake magnitude m x is a critical parameter in seismic hazard and risk analysis however some recent large earthquakes have shown that most of the existing methods for estimating m x are inadequate moreover m x itself is ill defined because its meaning largely depends on the context and it usually cannot be inferred using existing data without associating it with a time interval in this study we use probable maximum earthquake magnitude within a time period of interest m p t to replace m x the term m p t contains not only the information of magnitude limit but also the occurrence rate of the extreme events we estimate m p t for circum pacific subduction zones using tapered gutenberg richter tgr distributions the estimation of the two tgr parameters value and corner magnitude m c is performed using the maximum likelihood method with the constraint from tectonic moment rate to populate the tgr the rates of smaller earthquakes are needed we apply the whole earth model a high resolution global estimate of the rate of m 5 earthquakes to estimate these rates the uncertainties of m p t are calculated using monte carlo simulation our results show that most of the circum pacific subduction zones can generate m 8 5 earthquakes over a 250 year interval m 8 8 earthquakes over a 500 year interval and m 9 0 earthquakes over a 10 000 year interval for the cascadia subduction zone we include the 10 000 year paleoseismic record based on turbidite studies to supplement the limited instrumental earthquake data our results show that over a 500 year period m 8 8 earthquakes are expected in this zone over a 1000 year period m 9 0 earthquakes are expected and over a 10 000 year period m 9 3 earthquakes are expected

active tectonics of peru heterogeneous interseismic coupling along the nazca megathrust rigid motion of the peruvian sliver and subandean shortening accommodation over 100 gps sites measured in 2008 2013 in peru provide new insights into the present day crustal deformation of the 2200 km long peruvian margin this margin is squeezed between the eastward subduction of the oceanic nazca plate at the south america trench axis and the westward continental subduction of the south american plate beneath the eastern cordillera and subandean orogenic wedge continental active faults and gps data reveal the rigid motion of a peruvian forearc sliver that extends from the oceanic trench axis to the western eastern cordilleras boundary and moves southeastward at 4 5 mm yr relative to a stable south america reference frame gps data indicate that the subandean shortening increases southward by 2 to 4 mm yr in a peruvian sliver reference frame the residual gps data indicate that the interseismic coupling along the nazca megathrust is highly heterogeneous coupling in northern peru is shallow and coincides with the site of previous moderate sized and shallow tsunami earthquakes deep coupling occurs in central and southern peru where repeated large and great megathrust earthquakes have occurred the strong correlation between highly coupled areas and large ruptures suggests that seismic asperities are persistent features of the megathrust creeping segments appear at the extremities of great ruptures and where oceanic fracture zones and ridges enter the subduction zone suggesting that these subducting structures play a major role in the seismic segmentation of the peruvian margin in central peru we estimate a recurrence time of 305 40 years to reproduce the great 1746 mw 8 8 lima callao earthquake

sea level variations in relation to coastal flow around the gulf of alaska adjusted sea level deviations at six tide stations around the gulf of alaska were examined in light of our recent knowledge of the flow regime on the east side of the gulf a maximum in the deviations seems to be caused by winter barotropic flow on the shelf on the north side of the gulf the maximum in fall is apparently produced by a marked increase in flow of the baroclinic coastal current farther west the seasonal sea level signal is appreciably reduced

slip distribution and seismic moment of the 2010 and 1960 chilean earthquakes inferred from tsunami waveforms and coastal geodetic data the slip distribution and seismic moment of the 2010 and 1960 chilean earthquakes were estimated from tsunami and coastal geodetic data these two earthquakes generated transoceanic tsunamis and the waveforms were recorded around the pacific ocean in addition coseismic coastal uplift and subsidence were measured around the source areas for the 27 february 2010 maule earthquake inversion of the tsunami waveforms recorded at nearby coastal tide gauge and deep ocean assessment and reporting of tsunamis dart stations combined with coastal geodetic data suggest two asperities a northern one beneath the coast of constitucion and a southern one around the arauco peninsula the total fault length is approximately 400 km with seismic moment of 1 7 1022 nm mw 8 8 the offshore dart tsunami waveforms require fault slips beneath the coasts but the exact locations are better estimated by coastal geodetic data the 22 may 1960 earthquake produced very large 30 m slip off valdivia joint inversion of tsunami waveforms at tide gauge stations in south america with coastal geodetic and leveling data shows total fault length of 800 km and seismic moment of 7 2 1022 nm mw 9 2 the seismic moment estimated from tsunami or joint inversion is similar to previous estimates from geodetic data but much smaller than the results from seismic data analysis

eruptions of pavlof volcano and their possible modulation by ocean load and tectonic stresses all nine magmatic eruptions at pavlof volcano in six of the years from 1973 to 1984 have occurred between september 9 and november 20 volumes of erupted material range from 0 1 to 15 9 106 m3 dense rock equivalent at an average rate of 3 106 m3 yr 1 the volumes are estimated from eyewitness reports for two eruptions the others are estimated from a relationship that we derive between eruption volume and harmonic tremor duration and amplitude the volume of lava erupted is approximately time predictable a significant correlation exists between the eruptions and yearly nontidal variations in sea level and may result from ocean loading calculated volume changes beneath the volcano due to ocean loading are from 0 02 to 2 times eruption volumes and we postulate that the volcano acts as a long period several month volume strain meter with lava being preferentially erupted when strain beneath the volcano is compressive the volcano did not erupt during the period 1978 1980 when tilt seismic data and sea level data indicate that deep aseismic slip may have occurred models of this event predict a volume increase beneath the volcano that might have compensated strain from magma injection these observations indicate that pavlof volcano may be responsive to small slow changes in ambient stresses or strains and that these changes may modify or trigger eruptions