landslide generated tsunamis at reunion island 1 landslides that occur on oceanic volcanoes can reach the sea and trigger catastrophic tsunamis reunion island has been the location of numerous huge landslides involving tens to hundreds of cubic kilometers of material we use a new two fluid seawater and landslide numerical model to estimate the wave amplitudes and the propagation of tsunamis associated with landslide events on reunion island a 10 km3 landslide from the eastern flank of piton de la fournaise volcano would lift the water surface by about 150 m where it entered the sea the wave thus generated would reach saint denis the capital of reunion island population of about 150 000 people in only 12 min with an amplitude of more than 10 m and would reach mauritius island in 18 min although mauritius is located about 175 km from the impact waves reaching its coast would be greater than those for reunion island this is due to the initial shape of the wave and its propagation normal to the coast at mauritius but generally coast parallel at reunion island a submarine landslide of the coastal shelf of 2 km3 would trigger a 40 m high wave that would severely affect the proximal coast in the western part of reunion island for a landslide of the shelf of only 0 5 km3 waves of about 2 m in amplitude would affect the proximal coast

the 1989 macquarie ridge earthquake seismic moment estimation from long period free oscillations we have analyzed the long period 1000 s part of the earth s free oscillation spectrum of the 1989 macquarie ridge earthquake this event stands out as the largest in the last decade and as the first great earthquake to have been recorded digitally on the new generation of very broadband seismic sensors around the globe its spectrum was modeled for five spectral peaks 0s4 0s6 0s9 1s8 and 5s3 taking into account the effects of lateral heterogeneity rotation and ellipticity which cause coupling within the spectral peaks self coupling and between different multiplets multiplet coupling the effects of self coupling were calculated following the formulation of woodhouse and girnius 1982 multiplet coupling only weakly affected the spectral peaks that were used a large discrepancy in phase and amplitude between the calculated spectrum and the data was observed which suggests that the seismic moment was 50 larger than that inferred from surface wave analysis satake and kanamori 1990 an error analysis was performed in order to detect inaccuracies that might have resulted in this discrepancy centroid time source finiteness correction and directivity effects are likely to cause a significant bias both in the moment and phase determination we saw no direct evidence that a precursory event could have been responsible for the additional energy release as was suggested by ihmle et al 1993

seismic evidence for an earthquake nucleation phase near source observations show that earthquakes initiate with a distinctive seismic nucleation phase that is characterized by a low rate of moment release relative to the rest of the event this phase was observed for the 30 earthquakes having moment magnitudes 2 6 to 8 1 and the size and duration of this phase scale with the eventual size of the earthquake during the nucleation phase moment release was irregular and appears to have been confined to a limited region of the fault it was characteristically followed by quadratic growth in the moment rate as rupture began to propagate away from the nucleation zone these observations suggest that the nucleation process exerts a strong influence on the size of the eventual earthquake

scale dependent seismic velocity in heterogeneous media the measurable traveltimes of seismic events propagating in heterogeneous media depend on the geologic scale the seismic wavelength and the propagation distance in general the velocity inferred from arrival times is slower when the wavelength is longer than the scale of heterogeneity and faster when the wavelength is shorter for normal incidence propagation in stratified media this is the difference between averaging seismic slownesses in the short wavelength limit and averaging elastic compliances in the long wavelength limit in two and three dimensions there is also the path effect shorter wavelengths tend to find faster paths thus biasing the traveltimes to lower values in the short wavelength limit the slowness inferred from the average traveltime is smaller than the mean slowness of the medium when the propagation distance is much larger than the scale of the heterogeneity the path effect causes the velocity increase from long to short wavelengths to be much larger in two dimensions tha

teleseismic detection of a slow precursor to the great 1989 macquarie ridge earthquake low frequency spectra for the 1989 macquarie ridge earthquake magnitude 8 2 show an amplitude increase and a phase delay decrease below 6 millihertz that require a short term slow precursor this earthquake can be modeled as a compound event in which a fast rupturing ordinary earthquake was initiated by an episode of slow smooth deformation that began more than 100 seconds before the main shock the moment released in the slow precursor was large about 3 x 10 20 newton meters equivalent to an event of magnitude 7 6 the data are consistent with the precursor being generated in a region of the oceanic upper mantle below the main rupture

oceanic propagation of a potential tsunami from the la palma island 1 the likelihood of a large scale tsunami from the la palma island is considered small by most nevertheless the potential catastrophic consequences call for attention here we report on numerical simulations of a tsunami that might result from the extreme case of a flank collapse of the cumbre vieja volcano at the la palma island done by combining a multimaterial model for the wave generation with boussinesq models for the far field propagation our simulations show that the slide speed is close to critical effectively generating an initial wave of several hundred meters height our main focus is the wave propagation which is genuinely dispersive in the far field propagation becomes increasingly complex due to the combined effects of dispersion refraction and interference in the direction of propagation constructive interference of the trailing waves are found to decrease the decay of the maximum amplitude with distance compared to classical asymptotic theory at transatlantic distances thus the commonly used hydrostatic models fail to describe the propagation consequences of the la palma scenario would be largest at the canary islands but our findings also suggests that the whole central atlantic would face grave consequences however the largest surface elevations are smaller than the most pessimistic reports found in literature we also find undular bores towards the shorelines of america

the storegga slide tsunami comparing field observations with numerical simulations abstract deposits from the storegga tsunami have been found in coastal areas around the norwegian sea and north sea from the northeast coast of england to beyond the arctic circle in northern norway the tsunami deposits reach onshore elevations of 10 12 m above sea level of their time in western norway 3 6 m in northeast scotland and above 20 m on the shetland islands these elevations are compared with surface wave elevations derived from a numerical simulation of the storegga slide a good agreement is obtained for a retrogressive slide that descends at 25 30 m s and that has short time lags of 15 20 s between each individual slide block

a simplified 3 d navier stokes numerical model for landslide tsunami application to the gulf of mexico 1 a simplified three dimensional navier stokes 3 d ns model for two fluids water and landslide material mudslide is presented and validated with standard laboratory experiments dubbed tsunami3d tsunami solution using navier stokes algorithm with multiple interfaces is applied to a 3 d full scale landslide scenario in the gulf of mexico gom i e the east breaks underwater landslide the simplified 3 d ns model is conceived to be computationally efficient for tsunami calculations the simplification is derived from the large aspect ratio of the tsunami waves wavelength wave height and the selected computational grid that has a smaller aspect ratio this allows us to assume a horizontal fluid surface in each individual cell containing the interface air water air mudslide and water mudslide the tracking of fluid interfaces is based on the volume of fluid method and the surfaces are obtained by integrating the fluxes of each individual fluid cell along the water column in the momentum equation the pressure term is split into two components hydrostatic and nonhydrostatic the internal friction is solved in a simplified manner by adjusting the viscosity coefficient despite the simplification to get an efficient solution the numerical results agree fairly well with standard landslide laboratory experiments required by the national tsunami hazard mitigation program for tsunami model validation the numerical effect caused by using a sharp versus a diffusive water mudslide interface for a full scale landslide tsunami scenario is also investigated observations from this experiment indicated that choosing a sharp or diffusive interface seems to have no remarkable effect at early stages of the tsunami wave propagation last a large scale 3 d numerical simulation is carried out for the ancient gom s east breaks landslide by using the simplified model to calculate the early stages of the tsunami wave propagation

petrologic evolution of krakatau indonesia implications for a future activity abstract krakatau volcano is located along a n35e volcanic lineament running through the sunda straits indonesia its last activity has been characterized by successive phases each beginning with the construction of a cone and ending with its destruction and the formation of a caldera the two last pre and post 1883 cycles are well known but the more ancient ones are not so clearly defined lavas of krakatau belong to an andesitic series in which fractional crystallization plays the most important role the petrologic evolution is characterized by a cyclicity in good agreement with the structural evolution the succession is regular basalts basic andesites acid andesites dacites a gap between acid and basic andesites occurs in each cycle the destructive stages correspond to the occurrence of dacitic terms the anak cycle was characterized from 1927 to 1979 by basalts and basic andesites the 1981 eruption involved a more differentiated magma close to dacitic detailed study of the petrologic evolution since 1883 emphasizes the predominant role of fractional crystallization this process occurred during a very short period between 1979 and 1981 separation of labradorite augite olivine and magnetite from parental basic andesite may generate the dacitic descendant in a shallow reservoir p h 2 o estimated about 0 5 kbar implications for a future activity are considered

advances in the study of mega tsunamis in the geological record abstract extreme geophysical events such as asteroid impacts and giant landslides can generate mega tsunamis with wave heights considerably higher than those observed for other forms of tsunamis in this paper we review recent advances in the study of mega tsunamis in the geological record focusing on well documented examples that have captured particular attention over the past decade we provide up to date background on the source mechanisms of tsunami generation during asteroid impacts and ocean island landslides which are the largest landslides on earth we also discuss the main sources of uncertainty for modelling such mega tsunamis and for addressing associated hazards

earthquake source nucleation a physical model for short term precursors abstract ohnaka m 1992 earthquake source nucleation a physical model for short term precursors in t mikumo k aki m ohnaka l j ruff and p k p spudich editors earthquake source physics and earthquake precursors tectonophysics 211 149 178 this paper deals with a quasistatic leading to a quasidynamic at a later time nucleation process that precedes the earthquake dynamic rupture and models of the earthquake source nucleation are put forward based on physical principles a quasistatic to quasidynamic rupture nucleation process is an intrinsic part of the ensuing earthquake dynamic rupture in other words the nucleation process itself is an short term or immediate precursor that occurs in a localized zone during the earthquake nucleation premonitory slip proceeds in the localized nucleation zone and shear stress also decreases gradually in the zone since slip weakening occurs during the nucleation immediate foreshock activity is a part of the nucleation process leading to the mainshock dynamic rupture therefore hypocentral locations of foreshocks are necessarily restricted to lie near the mainshock hypocentre onset of the mainshock rupture whether or not foreshocks occur during the mainshock nucleation depends on how the rupture growth resistance varies on a local to small scale since patches of greater rupture growth resistance are considered to prevail on a local to small scale in the fault zone carrying immediate foreshocks would be one of the major characteristics of earthquakes that nucleate within the brittle seismogenic layer when a mainshock earthquake nucleates within the brittle seismogenic layer and its hypocentre is located near the base of the seismogenic layer immediate foreshocks for this mainshock are necessarily restricted to lie within a localized region shallower than hypocentral depth of the mainshock by contrast the nucleation process below the base of the seismogenic layer is aseismic in nature so that carrying no conspicuous foreshocks would be a common characteristic of interplate earthquakes that nucleate below the base of the brittle seismogenic layer the breakdown strength p the breakdown stress drop b and the critical slip displacement dc are indicative of the rupture growth resistance to estimate depth variations of these parameters the effects of the normal stress n and temperature t on those parameters are examined using available data so far published the combined effects of n and t on p in the brittle to semibrittle regime are found to be represented empirically by p n t po n 1 cosh 50 t 40 sinh 50 t exp 2000 t where po n 135 7 0 750 n and t is measured in k and n in mpa it is found that dc increases sharply with t but is insensitive to n above 300 c while dc depends on n but is insensitive to t below 300 c on the basis of these results variations in p dc and b at mid crustal depths are estimated for quartzo feldspathic rocks for a given geothermal gradient

numerical modeling of the september 13 1999 landslide and tsunami on fatu hiva island french polynesia 1 on september 13 1999 omoa bay fatu hiva island french polynesia was struck by 2 to 5 m high water waves several buildings were flooded and destroyed but no lives were lost observations gathered during a post event survey revealed the recent collapse into the sea of a 300 300 m2 at least 20 m thick cliff located 5 km southeast of omoa this cliff failure most certainly triggered the tsunami waves since the cliff was reported intact 45 min earlier we simulate the tsunami generation due to a subaerial landslide using a finite difference model assimilating the landslide to a flow of granular material numerical modeling shows that a 0 0024 km3 landslide located in the presumed source area accounts for the tsunami waves reported in omoa bay we show that the striking amplification observed in omoa bay is related to the trapping of waves due to the shallow submarine shelf surrounding the island

numerical simulation of the last flank collapse event of montagne pelee martinique lesser antilles 1 we model the submarine emplacement of a debris avalanche generated by the last flank collapse event of montagne pelee volcano we estimate the collapsed volume 1 7 km3 using both the volume of the missing material in the horseshoe shaped structure and the volume of submarine deposits this avalanche is treated as the gravitational flow of a homogeneous continuum it is simulated by a finite difference model solving mass and momentum conservation equations that are depth averaged over the slide thickness numerical simulations show that the emplacement of this debris avalanche can be suitably modeled by a coulomb type friction law with a variable friction angle below 10 we propose that variations of the friction angle are mainly influenced by the thickness of the flowing mass

numerical modelling of tsunami generation and propagation from submarine slumps the 1998 papua new guinea event summary deep and large submarine slumps may generate tsunamis as disastrous as tsunamis of tectonic origin such a landslide is likely to be the origin of the 1998 july 17 tsunami of papua new guinea the deadliest tsunami in the last 50 years water waves devastated a 20 km stretch of coastline wiping out three villages and killing more than 2200 people a numerical model has been developed to study the efficiency of deep slumps in producing tsunamis and has been applied to the papua new guinea event the landslide is treated as the flow of a homogeneous gravity driven continuum governed by a rheological law water waves are generated by sea bottom displacements induced by the landslide the shallow water approximation is adopted for both the landslide and the associated water waves the resulting differential equations are solved by a finite difference method based on shock capturing the shallow water hypothesis is tested by comparison with a model solving navier stokes equations for a mixture of water and sediments sensitivity tests carried out for a 2 d simplified geometry show that the water surface profile depends strongly on the constitutive law of the landslide the 1998 event is simulated numerically by the shallow water model testing different friction laws the observed inundation height distribution is well reproduced by the model for a volume of 4 km3 with its top located at a water depth of 550 m and sliding with a coulomb type friction law over a distance of 5 km

numerical modeling of tsunami waves generated by the flank collapse of the cumbre vieja volcano la palma canary islands tsunami source and near field effects 1 in this work we study waves generated by the potential collapse of the west flank of the cumbre vieja volcano cvv la palma canary island spain through numerical simulations performed in two stages i the initial slide motion and resulting free surface elevation are first calculated using a 3d navier stokes model ii generated waves are then input into a 2d horizontal boussinesq model to further simulate propagation to the nearby islands unlike in earlier work on cvv besides a similar extreme slide volume scenario of 450 km3 in our simulations i we consider several slide scenarios featuring different volumes i e 20 40 80 km3 which partly result from a geotechnical slope stability analysis ii we use a more accurate bathymetry and iii an incompressible version of a multiple fluid material navier stokes model we find wave trains for each scenario share common features in terms of wave directivity frequency and time evolution but maximum elevations near cvv significantly differ ranging from 600 to 1200 m for increasing slide volume additionally our computations show that significant energy transfer from slide to waves only lasts for a short duration order 200 s which justifies concentrating our best modeling efforts on the early slide motion phase the anticipated consequences of such wave trains on la palma and other canary islands are assessed in detail in the paper

numerical simulation of the december 1997 debris avalanche in montserrat lesser antilles emplacement of a debris avalanche in the white river valley of southern montserrat lesser antilles on 26 december 1997 was caused by sector failure of the south flank of the active soufriere hills volcano pre and post emplacement surveys of the region indicate a debris avalanche deposit volume of about 40 50 106 m this avalanche is modeled as the gravitational flow of a homogeneous continuum governed by a basal friction law mass and momentum equations are depth averaged over the slide thickness numerical results show that the observed distribution of debris and duration of emplacement is simulated well for a coulomb type friction law with a dynamic friction coefficient dependent upon the thickness and the velocity of the flowing mass

the december 22 2018 anak krakatau indonesia landslide and tsunami preliminary modeling results on the evening of december 22 2018 the coasts of the sunda strait indonesia were hit by a tsunami generated by the collapse of a part of the anak krakatau volcano hundreds of people were killed thousands were injured and displaced this paper presents a preliminary modeling of the volcano flank collapse and the tsunami generated based on the results of a 2d depth averaged coupled model involving a granular rheology and a coulomb friction for the slide description and dispersive effects for the water flow part with a reconstructed total volume subaerial and submarine of the landslide of 150 million hbox m 3 inferred from pre and post collapse satellite and aerial images the comparison of the simulated water waves with the observations tide gauges located all around the strait photographs and field surveys is satisfactory due to the lack of information for the submarine part of the landslide the reconstructed submarine slope is assumed to be approximately constant a significant time delay on the results and particularly in the bandar lampung bay could be attributed to imprecisions of bathymetric data the sensitivity to the basal friction and to dispersive effects is analyzed through numerical tests results show that the influence of the basal friction angle on the simulated wave heights decreases with distance and that a value of 2 circ gives consistent results with the observations the dispersive effects are assessed by comparing water waves simulated by a shallow water model and a boussinesq model simulations with frequency dispersion produce longer wave periods and smaller wave amplitudes in the sunda strait and particularly in deep waters

generation mechanism of tsunamis from the 1883 krakatau eruption the 1883 eruption of krakatau generated a destructive tsunami which claimed about 34 000 lives we compute the generation and propagation of tsunamis from three models previously proposed they are 1 large scale caldera collapse of the northern part of krakatau island 2 emplacement of pyroclastic flow deposits 3 submarine explosion we numerically solve the non linear shallow water equations on actual bathymetry all three models displace the same volume 11 5 km 3 of water in different ways we compare the results of our computation with the observed tsunami waveforms at batavia and tsunami wave heights along the coasts of java and sumatra the comparison shows that the submarine explosion model of 1 to 5 min duration best explains the generation of the largest tsunami

direct observation of rupture propagation during the 1979 imperial valley earthquake using a short baseline accelerometer array abstract the 1979 imperial valley california earthquake m s 6 9 was recorded on the el centro differential array a 213 m long linear array of 5 three component digital accelerometers 5 6 km from the nearest tectonic surface rupture although absolute time was not recorded on the array elements a relative time base was established using the main shock hypocentral p wave and the p and s waves from a later aftershock a cross correlation technique was used to measure the difference in arrival times of individual seismic waves in a moving 0 6 to 1 2 sec window at each array element which would then be converted into the wave9s slowness 1 velocity along the array when applied to the main shock vertical and horizontal accelerograms results from both components of motion indicated that the early arriving energy came from a source to the south of the array and the source of the energy moved rapidly to the north of the array during the strong shaking the ground motions at the array elements were well correlated for about the first 11 sec of motion these observations suggest that we have observed the initiation of rupture south of the array and its subsequent propagation along the fault to a position north of the array in about 10 sec and that the energy was radiated from a fairly compact region around the rupture front if the observed vertical and horizontal ground motions are assumed to be caused by p and s waves respectively then the observed slownesses show irregularities which can be interpreted as implying that the observed high frequency ground motions originated at irregularly distributed regions on the fault surface or that the rupture velocity was variable or both one possible interpretation of the data suggests that the rupture proceeded at near p wave velocity over a 7 km long section of fault average rupture velocities of about 2 7 to 3 2 km sec at 8 km depth are consistent with the data and 2 8 km sec is weakly preferred under the assumption that rupture propagates at a fixed fraction of the shear velocity the large vertical pulse which had a peak acceleration of 1 7 g at e06 was emitted from the portion of the fault extending 25 to 30 km northwest of the hypocenter near meloland overpass and not from the point on the fault closest to the differential array nothing can be said about fault behavior southeast of the hypocenter

evidence calibrated numerical model of december 22 2018 anak krakatau flank collapse and tsunami on december 22 2018 a sector of the anak krakatau volcano edifice collapsed into the sea generating a tsunami that hit the sunda strait coasts in indonesia the collapse followed a period of 6 months of volcanic activity that was insufficient to warn the tsunami threatened coastal population the anak krakatau tsunami resulted in hundreds of casualties thousands of injured and displaced people and massive coastal damage this paper uses the tsunami records the collected field survey data and satellite imagery based interpretations to develop a model of the anak krakatau flank failure and tsunami we address the dynamics of the flank failure the tsunami generation and propagation and the coastal impact using evidence calibrated numerical modelling an in house developed multi layer viscoplastic shallow water numerical code is employed to simulate the anak krakatau collapse mass movement and the whole source to coast tsunami process our results suggest that a flank collapse scenario involving a volume of material of 0 135 km3 and occurring as a sequence of two failures fairly reproduces the local and regional tsunami records and survey data

numerical simulations of large water waves due to landslides a mathematical model based on the hydrodynamic shallow water equations is developed for numerical simulation of slide generated waves in fjords the equations are solved numerically by a finite difference technique to examine the performance of the numerical model we have simulated the slide catastrophe in tafjord western norway 1934 the predicted runup heights are in good agreement with measured runup heights the effects of wave amplification are estimated in runup zones with gentle beach slopes the model results reveal wave energy trapping due to the fjord geometry this causes standing wave oscillations in accordance with the observations

numerical simulation of the landslide generated tsunami in kitimat arm british columbia canada 27 april 1975 1 it remains challenging to predict and estimate potential damage from tsunamis using computer models one of the approaches to validate models is to compare their results with site observations we carried out numerical modeling for both the underwater landslide and the associated tsunami that occurred near kitimat british columbia canada on 27 april 1975 a few observations of high water marks along the coastline indicated 8 2 m tsunami waves previous survey results of the seafloor showed that a landslide traveled about 5 km down the axis of the fjord from its source areas on the sidewall of the fjord near the head of the inlet and on the lower kitimat river delta we modeled the subaqueous slope failure as a bingham visco plastic fluid debris flow based on previous geotechnical investigations at the site and numerically solved the landslide generated tsunami wave and debris flow equations using a finite volume godunov type scheme this method resolves abrupt wave and landslide front interactions and remains oscillation free the computed motion of the debris flow is generally consistent with observations simulations indicate that the failure propagated approximately 4 5 km down the fjord axis from its inception point we have found that computed amplitudes for the tsunami wave crest at the coast of kitimat arm were between 6 and 11 m these values are somewhat higher than previous simplistic solitary wave theory estimates of 6 3 m and observations of 8 2 m

numerical modelling of the tsunami triggered by the guimar debris avalanche tenerife canary islands comparison with field based data abstract some tsunami deposits have been previously identified 41 188 m asl in the agaete valley on the northwest coast of the island of gran canaria in the canary islands in this paper the guimar sector collapse tenerife 0 83 ma and its expected associated tsunami that is thought to be at the origin of these tsunami deposits are tentatively reproduced using a two fluid numerical code two failure processes are considered 1 the whole 44 km 3 volume is released in one go or 2 the 44 km 3 are released in five retrogressive failures of equal volume occurring each 120 s in both cases two rheologies are used to simulate the landslide propagation the mohr coulomb frictional law and a constant retarding stress two hypotheses concerning the origin of the offshore mapped deposits are also considered 1 the mapped deposits are the direct result of a single collapse event occurring either in one go or by near retrogressive failures or 2 the mapped deposits result from a collapse followed by later partial remobilization of its deposits in all scenarios the subaerial destabilisation spreads out eastwards into the sea triggering waves 390 500 m high when considering a collapse in one go and 225 380 m when considering successive retrogressive failures the first wave reaches the coast of gran canaria located at 70 km from the scar 495 560 s after the collapse onset whatever the scenario considered water enters the agaete valley on gran canaria 555 690 s after the onset of collapse reaching up to 9 1 km inland for a collapse in one go and 5 0 km when considering five retrogressive failures in this valley the simulated waves inundate all the locations where tsunami deposits were identified with the flow depth measured reaching a maximum of 50 m collapse by retrogressive failures to 150 m collapse in one go at these particular places the directions of maximum kinetic energy as a function of time for the simulated waves are consistent with the current directions recorded by the cobble fabrics present in the run up and backwash layers of the tsunami deposits at one outcrop this study shows that the major source of uncertainty when reproducing landslide triggered tsunamis is linked to the way the landslide happens failure mechanisms that should be thus more precisely taken into account for landslide triggered tsunamis hazard assessment the rheology chosen to simulate the landslide propagation has only a second order impact on the produced waves

surface processes recorded by rocks and soils on meridiani planum mars microscopic imager observations during opportunity s first three extended missions the microscopic imager mi on the mars exploration rover opportunity has returned images of mars with higher resolution than any previous camera system allowing detailed petrographic and sedimentological studies of the rocks and soils at the meridiani planum landing site designed to simulate a geologist s hand lens the mi is mounted on opportunity s instrument arm and can resolve objects 0 1 mm across or larger this paper provides an overview of mi operations data calibration and analysis of mi data returned during the first 900 sols mars days of the opportunity landed mission analyses of opportunity mi data have helped to resolve major questions about the origin of observed textures and features these studies support eolian sediment transport rather than impact surge processes as the dominant depositional mechanism for burns formation strata mi stereo observations of a rock outcrop near the rim of erebus crater support the previous interpretation of similar sedimentary structures in eagle crater as being formed by surficial flow of liquid water well sorted spherules dominate ripple surfaces on the meridiani plains and the size of spherules between ripples decreases by about 1 mm from north to south along opportunity s traverse between endurance and erebus craters

seismicity of the sunda strait evidence for crustal extension and volcanological implications the sunda strait is located in the transitional zone between two different modes of subduction the java frontal subduction and the sumatra oblique subduction this setting implies that the sunda strait region is a key to the understanding of the geodynamic processes involved in order to study the shallow seismicity a microearthquake survey was carried out in that region twelve stations accurately located by the aim of satellite positionning recorded about 300 local events in the summer 1984 from this set 174 shallow earthquakes have been precisely located the results of this study reveal that the crustal earthquakes in the sunda strait area occurs in three main areas 1 beneath the krakatau complex where earthquakes are generated by double couples and are of tectonic origin 2 inside a graben in the western part of the strait and 3 in a more diffused zone to the south of sumatra the individual and composite focal mechanisms from the events inside the strait show an extensional regime a stress tensor which have been deduced from the individual focal mechanisms of earthquakes of the krakatau group shows that the tensional axis is oriented n130oe this study confirms that the sunda strait is in an extensional tectonic regime as a result of the northwestward movement of the sumatra sliver plate along the semangko fault zone

ice marginal environment and ecosystem prior to initial advance of the late palaeozoic ice sheet in the mount butters area of the central transantarctic mountains antarctica basal rocks of the upper carboniferous to lower permian pagoda formation at mount butters provide an unusual view of periglacial conditions in the central transantarctic mountains region prior to the initial advance of the gondwanide ice sheet these rocks were deposited on a high relief unconformity that developed on granite deposition within relief on the unconformity possibly in the lee of a granite buttress protected the rocks from erosion during subsequent overriding by the ice sheet the succession reflects deposition in a glacial fed to ice contact lake that contained a freshwater crustacean fauna centimetre to decimetre scale basal layers include breccia and coarse grained sandstone the occurrence of breccia resting on weathered granite suggests sedimentation as scree and as mass flow deposits overlying decimetre to metre scale stratified diamictites interbedded with metre scale coarsening upward successions of siltstone to cross laminated sandstone suggest lacustrine deposition by suspension settling rain out of ice rafted debris and deltaic progradation thin zones with abundant conchostracans and or with prolific trace fossils in addition to less common remains of other crustaceans attest to the presence of a low diversity benthic fauna conchostracans are concentrated in a series of thin beds that reflect moderately lengthy perhaps seasonal periods of free flowing water patchy vertical and lateral distribution of intense bioturbation and profuse trace fossils probably reflect repeated colonization events during times of favourable environmental conditions massive diamictite overlies the basal rocks and indicates that the ice marginal lake was subsequently overridden by the late palaeozoic ice sheet occurrences of lodgement till glacitectonite and deformation till suggest deposition from temperate or warm based ice whereas underlying lacustrine and deltaic deposits along with a crustacean and trace fossil fauna suggest temperate periglacial conditions previous studies have stressed that upper palaeozoic glacigenic deposits in antarctica and in gondwanaland record deglaciation events in contrast rocks at mt butters provide an unusual glimpse into an ice margin lake and its fauna just prior to ice sheet advance

large scale volcanic cone collapse the 1888 slope failure of ritter volcano and other examples from papua new guinea a largely submarine avalanche amphitheatre that formed catastrophically in 1888 on ritter volcano has been identified from a bathymetric survey collapse of the volcano in 1888 therefore is considered to have been caused by rapid large scale slope failure rather than by cauldron subsidence as previously supposed escarpments of pre historic slope failures are common on other papua new guinea volcanoes directions of avalanching on some volcanoes in the bismarck volcanic arc appear to be controlled by a regional stress pattern and those for some volcanoes in the fly highlands province on mainland papua new guinea point away from the regional centre of pliocene uplift large amphitheatres such as at doma peaks in the fly high lands province probably originated by multiple collapses

teleseismic search for slow precursors to large earthquakes some large earthquakes display low frequency seismic anomalies that are best explained by episodes of slow smooth deformation immediately before their high frequency origin times analysis of the low frequency spectra of 107 shallow focus earthquakes revealed 20 events that had slow precursors 95 percent confidence level 19 were slow earthquakes associated with the ocean ridge transform system and 1 was a slow earthquake on an intracontinental transform fault in the east african rift system these anomalous earthquakes appear to be compound events each comprising one or more ordinary fast ruptures in the shallow seismogenic zone initiated by a precursory slow event in the adjacent or subjacent lithosphere

numerical modeling of the june 17 2017 landslide and tsunami events in karrat fjord west greenland on june 17 2017 the western coast of greenland was the site of a tsunami which flooded several villages killing 4 people and destroying 11 houses in the village of nuugaatsiaq this tsunami was triggered by a subaerial landslide which occurred in a fjord 32 km ene of nuugaatsiaq this paper presents the numerical modeling of this landslide of sim 50 million hbox m 3 and of the tsunami propagation from its source to nuugaatsiaq the landslide is considered as a granular flow under gravity forces and the water waves generated are related to the displacement of the sea bottom the results obtained are similar in amplitude to our inferences from videos i e three water waves between 1 and 1 5 m arriving at nuugaatsiaq with a period of roughly 3 min and are also in general agreement with the amplitude 1 m resulting from deconvolution of oscillations recorded on a horizontal seismogram operating at nuugaatsiaq nuug according to the field survey performed by fritz et al egu general assembly conference abstracts vol 20 of egu general assembly conference abstracts p 18345 2018a on july 2017 a second mass next to the landslide is threatening karrat fjord a sensitivity study is realized on its volume with 2 7 14 and 38 million hbox m 3 reaching the sea the shape of the water waves is found to be independent of volume and linearity is observed between the volume and the water wave heights finally the orientation of the slide does not seem to influence either the period or the shape of the generated water waves

the 1741 oshima oshima eruption extent and volume of submarine debris avalanche oshima oshima is a small volcanic island southwest off hokkaido in japan sea the violent eruption on august 29 1741 caused a sector collapse of the north flank very destructive tsunami with 2000 casualties was also documented but the generation mechanism has been controversial volume of subaerial sector collapse about 0 4 km was considered too small to generate such a devastating tsunami we compile and analyze recently obtained swath bathymetry data around the island the volcano is more than 2 3 km high from ocean bottom with its base diameter of 18 km the total slide volume both subaerial and submarine is estimated as 2 4 km nearly an order of magnitude larger than the subaerial part to the north of island hummocky terrain of debris deposits extends in an area of 69 km with the total volume of 2 5 km a value similar to the total slide volume it is one of the largest debris avalanches in historic time and probably responsible to the tsunami generation

modelling 2018 anak krakatoa flank collapse and tsunami effect of landslide failure mechanism and dynamics on tsunami generation the 2018 anak krakatoa volcano flank collapse generated a tsunami that impacted the sunda strait coastlines in the absence of a tsunami early warning system it caused several hundred fatalities there are ongoing discussions to understand how the failure mechanism of this event affected landslide dynamics and tsunami generation in this paper the sensitivity to different failure scenarios on the tsunami generation is investigated through numerical modelling to this end the rate of mass release the landslide volume the material yield strength and orientation of the landslide failure plane are varied to shed light on the failure mechanism landslide evolution and tsunami generation we model the landslide dynamics using the depth averaged viscoplastic flow model bingclaw coupled with depth averaged long wave and shallow water type models to simulated tsunami propagation we are able to match fairly well the observed tsunami surface elevation amplitudes and inundation heights in selected area with the numerical simulations however as observed by other authors discrepancies in simulated and observed arrival times for some of the offshore gauges are found which raises questions related to the accuracy of the available bathymetry for this purpose further sensitivity studies changing the bathymetric depth near the source area are carried out with this alteration we are also able to match better the arrival times of the waves

rupture process of the ms 6 6 superstition hills california earthquake determined from strong motion recordings application of tomographic source inversion abstract we analyze strong motion recordings of the m s 6 6 superstition hills earthquake to determine the timing location spatial extent and rupture velocity of the subevents that produced the bulk of the high frequency 0 5 to 4 hz seismic energy radiated by this shock the earthquake can be characterized by three principal subevents the largest ones occurring about 3 and 10 sec after initiation of rupture timing relationships between pulses on the seismograms indicate that the three subevents are located within 8 km of each other along the northern portion of the superstition hills fault the two largest subevents display different directivity effects we apply a tomographic source inversion to the integrated accelerograms to determine the slip acceleration on the fault as a function of time and distance based on a one dimensional fault model the azimuthal distribution of amplitudes for the second subevent can be largely explained by a rupture that propagated about 2 km to the southeast along the superstition hills fault at a velocity about equal to the p wave velocity an alternative model with rupture propagating to the northeast along a conjugate fault plane can also account for the observed directivity of this subevent but it is not supported by the aftershock distribution the third subevent ruptured to the southeast along an 8 km long portion of the superstition hills fault at about the shear wave velocity this rupture propagation caused the relatively large accelerations and velocities observed in strong motion records for stations southeast of the hypocenter the long time intervals between the subevents and their relative proximity to each other indicate a very slow component to the rupture development the southern half of the superstition hills fault did not generate significant high frequency strong ground motion although it showed substantial co seismic surface displacement the subevents are situated along the same northern portion of the fault where most of the aftershocks are located the locations of the subevents appear to be controlled by bends in the fault mapped at the surface and by changes in basement structure at depth

rockslide tsunamis in complex fjords from an unstable rock slope at akerneset to tsunami risk in western norway abstract an unstable rock volume of more than 50 million m 3 has been detected in the akerneset rock slope in the narrow fjord storfjorden more romsdal county western norway if large portions of the volume are released as a whole the rockslide will generate a tsunami that may be devastating to several settlements and numerous visiting tourists along the fjord the threat is analysed by a multidisciplinary approach spanning from rock slope stability via rockslide and wave mechanics to hazard zoning and risk assessment the rockslide tsunami hazard and the tsunami early warning system related to the two unstable rock slopes at akerneset and hegguraksla in the complex fjord system are managed by aknes tafjord beredskap iks previously the aknes tafjord project the present paper focuses on the tsunami analyses performed for this company to better understand the effects of rockslide generated tsunamis from akerneset and hegguraksla two and three dimensional site specific laboratory experiments are conducted to study the generation propagation and run up of the wave for several potential rockslide scenarios from akerneset furthermore the two models globouss and dpwaves are applied for numerical simulations of the generation propagation phase and a third model most is applied for numerical simulations of the near shore propagation and inundation of the wave in selected locations strong emphasis is put on verification validation and sensitivity of the numerical models the best match between the numerical simulations and the laboratory experiments is found for the larger scenarios with the linear dispersive solution for the propagation phase the corresponding calculated run up values are remarkably similar to the ones observed during the laboratory experiments during the risk assessment it was found that the rockslide tsunami hazard probability of impact is higher than accepted by the norwegian planning and building act this should at that time prevent any further development in all the exposed areas of the entire fjord system the act is today altered to open for specified further development in the various hazard zones the results of the tsunami analyses are applied in risk management in terms of hazard map production and land use planning two failure scenarios for each of the two unstable rock slopes are designed for the hazard zoning the larger and less probable scenarios 1 in 5000 years are applied for evacuation zones and routes while the smaller and more probable scenarios larger than 1 in 1000 years are applied for location and design of less critical facilities accepted in the inundation zone

source parameters of small earthquakes recorded at 2 5 km depth cajon pass southern california implications for earthquake scaling a 2 5 km deep triaxial seismometer at cajon pass in southern california has recorded several hundred earthquakes ml4 0 occurring within the san andreas fault system at 2 5 km seismic background noise is below amplifier sensitivity and the 2 250 hz spectral range of recorded seismic motion is wider and higher than that of most natural event catalogs compared with downhole recorded motion seismic amplitudes at the surface are amplified below 10 hz and severely attenuated above 30 hz we estimate that qs is at least 1000 for wave motion at 2 5 km and below and qp is over 2000 the range of source dimensions in the downhole recorded catalog is 10 m to 70 m ml 2 0 mo 108 nm to ml 2 7 mo 1013 nm the plot of log source radius vs log moment has a straight line trend compatible with earthquake scaling at constant stress drop inferred stress drops are scattered between 1 and 500 bars there is no evidence in the catalog for the proposed minimum source dimension at 100 m when the cajon pass borehole catalog containing some of the smallest recorded natural earthquakes is combined with 800 larger events from previous studies the moment radius trend suggests that natural earthquakes are self similar over a magnitude range m 2 to 8 we suggest that inferences of minimum source dimension are more likely due to bias in bandlimited individual catalogs than to properties of the seismic crust

evidence for and implications of self healing pulses of slip in earthquake rupture dislocation time histories of models derived from waveforms of seven earthquakes are discussed in each model dislocation rise times the duration of slip for a given point on the fault are found to be short compared to the overall duration of the earthquake 10 however in many crack like numerical models of dynamic rupture the slip duration at a given point is comparable to the overall duration of the rupture i e slip at a given point continues until information is received that the rupture has stopped propagating alternative explanations for the discrepancy between the short slip durations used to model waveforms and the long slip durations inferred from dynamic crack models are 1 the dislocation models are unable to resolve the relatively slow parts of earthquake slip and have seriously underestimated the dislocations for these earthquakes 2 earthquakes are composed of a sequence of small dimension short duration events that are separated by locked regions barriers 3 rupture occurs in a narrow self healing pulse of slip that travels along the fault surface evidence is discussed that suggests that slip durations are indeed short and that the self healing slip pulse model is the most appropriate explanation a qualitative model is presented that produces self healing slip pulses the key feature of the model is the assumption that friction on the fault surface is inversely related to the local slip velocity the model has the following features high static strength of materials kilobar range low static stress drops in the range of tens of bars and relatively low frictional stress during slip less than several hundreds of bars it is suggested that the reason that the average dislocation scales with fault length is because large amplitude slip pulses are difficult to stop and hence tend to propagate large distances this model may explain why seismicity and ambient stress are low along fault segments that have experienced large earthquakes it also qualitatively explains why the recurrence time for large earthquakes may be irregular

model simulations of tsunamis generated by the storegga slides abstract a mathematical model based on the hydrodynamic shallow water equations is developed for numerical simulation of water waves generated by the submarine storegga slides on the norwegian continental slope the equations are solved numerically by a finite difference technique computations of wave amplification effects reveal run up heights for the second storegga slide between 3 and 5 m in exposed areas along the eastern coast of greenland iceland and scotland and the western coast of norway the calculated run up heights agree remarkably well with possible tsunami wave heights deduced from geological evidences along the eastern coast of scotland the generated wave heights are strongly dependent on the acceleration of the slide the effects of shear stress at the interface between the water and the slide body has turned out to be important

the 1979 submarine landslide generated tsunami in mururoa french polynesia this paper aims at best describing the submarine landslide which induced partial submersion of the atolls of mururoa and fangataufa in 1979 more precisely waves propagated along the south coast of mururoa atoll and penetrated into its lagoon some minutes after the landslide triggering t 0 s whereas a train of eight water waves reached the runway located on the north east coast of fangataufa 40 km south of mururoa between t 7 min 30 s and t 20 min a numerical model based on shallow water equations is used to simulate the landslide as well as the associated tsunami saint venant equations are used to propagate the tsunami in coastal areas whereas the offshore propagation is simulated by solving weakly nonlinear boussinesq equations low and high resolution nested grids are used to simulate the tsunami propagation in deep sea and in shallow waters respectively several scenarios have been tested to reproduce the observed water and run up heights in the near and far fields the best scenarios correspond to a landslide with a volume in the range 75 90 mm3 for a basal friction angle of 35 and with a basal friction angle in the range 30 40 for a volume of 80 mm3 these results have been completed by a parametric study on the slide parameters

did a submarine landslide contribute to the 2011 tohoku tsunami many studies have modeled the tohoku tsunami of march 11 2011 as being due entirely to slip on an earthquake fault but the following discrepancies suggest that further research is warranted 1 published models of tsunami propagation and coastal impact underpredict the observed runup heights of up to 40 m measured along the coast of the sanriku district in the northeast part of honshu island 2 published models cannot reproduce the timing and high frequency content of tsunami waves recorded at three nearshore buoys off sanriku nor the timing and dispersion properties of the waveforms at offshore dart buoy 21418 3 the rupture centroids obtained by tsunami inversions are biased about 60 km nne of that obtained by the global cmt project based on an analysis of seismic and geodetic data together with recorded tsunami waveforms we propose that while the primary source of the tsunami was the vertical displacement of the seafloor due to the earthquake an additional tsunami source is also required we infer the location of the proposed additional source based on an analysis of the travel times of higher frequency tsunami waves observed at nearshore buoys we further propose that the most likely additional tsunami source was a submarine mass failure smf i e a submarine landslide a comparison of pre and post tsunami bathymetric surveys reveals tens of meters of vertical seafloor movement at the proposed smf location and a slope stability analysis confirms that the horizontal acceleration from the earthquake was sufficient to trigger an smf forward modeling of the tsunami generated by a combination of the earthquake and the smf reproduces the recorded on near and offshore tsunami observations well particularly the high frequency component of the tsunami waves off sanriku which were not well simulated by previous models the conclusion that a significant part of the 2011 tohoku tsunami was generated by an smf source has important implications for estimates of tsunami hazard in the tohoku region as well as in other tectonically similar regions

refined numerical modeling of the 1979 tsunami in nice french riviera comparison with coastal data 1 the 16 october 1979 landslide at nice airport france produced tsunami waves observed in several harbors and the city of antibes was significantly flooded a new simulation of this event is presented in this paper to assess the sensitivity of the tsunami to the properties of the slide and to evaluate how local bathymetry and harbor resonance influence the effects of the tsunami at the coast a study of slide viscosity and water incorporation is performed using a detailed numerical model with a single initial volume of about 107 m3 the propagation of the tsunami is then simulated with a multigrid finite difference code using high resolution bathymetry in the harbors to a greater level of detail than previous studies we show that while the slide parameters are of great importance to properly model the later stages of the slide the initial volume and early dynamics of the slide are the relevant factors for determining the characteristics of the tsunami numerical results are compared with tide recordings in nice and villefranche as well as a mapping of the flood computed maximum elevation maps are compared with witness reports highlighting a focusing of the waves on antibes which explains its vulnerability this kind of focusing pattern should be considered when assessing the tsunami hazard for coastal regions calculated resonant periods in nice villefranche port vauban and la salis are matched with components present in both observed and computed waveforms most of the observed waves in nice and villefranche can be attributed to resonance

the coupling of a submarine slide and the surface waves which it generates underwater landslides are a common source of small scale tsunamis in coastal areas they have been the object of only a few theoretical and experimental studies a numerical model is developed to study the coupling of a submarine landslide and the surface waves which it generates a formulation of the dynamics of the problem is presented where the landslide is treated as the laminar flow of an incompressible viscous fluid and the water motion is assumed irrotational long wave approximation is adopted for both water waves and the mudslide the resulting differential equations are solved by a finite difference method we present the numerical results which contrast the behavior of the mud flow under a fixed surface in the presence of one way coupling bottom deformations affect the free surface and with full coupling surface pressure gradients react on the mud flow it is found that three main waves are generated by a landslide starting from rest on a gentle uniform slope the first wave is a crest which propagates away from the mudslide site into deeper water this crest is followed by a trough in the form of a forced wave which propagates with the speed of the mudslide front the third wave is a relatively small trough which propagates shoreward two major parameters dominate the interaction between the slide and the waves it produces the density of sliding material and the depth of water at the mudslide site the two way interactions are significant for the cases of a smaller mud density and shallower waters for the cases of larger mud density and shallower waters the two way interactions are small but the waves generated are very large for larger initiation depth of the mudslide the interactions are weak and the waves generated are small we also examined the possibility of a resonance between the slide and the waves our numerical results indicate that a resonance is not expected in many practical cases

hierarchy in earthquake size distribution abstract we propose a fault model in which there are a finite number of characteristic lengths between the smallest and the largest scales e g between a grain size and a size of great earthquakes a fault plane in one scale is segmented into blocks of statistically similar sizes by the barriers of statistically similar heights rupture expands by successively climbing the barriers the average barrier height is proportional to the average block size which defines the characteristic length of the relevant scale stresses before and after rupturing are assumed to be independent of earthquake size with these assumptions the probability for rupture to grow further is shown to be independent of the scale of barrier structure the rupture in one scale however tends to grow more easily as it grows so that once the rupture exceeds some critical size it no longer stops until it encounters the barriers in the next larger scale rupture grows by repeating this cycle which starts with rupturing of a unit block in one scale and ends with one in the next larger scale our model involves two parameters which must be determined empirically one is the length ratio r between two successive scales the other is the critical number of blocks n c which defines the critical size for unstable rupture growth in one scale we suggest values of 5 for both r and n c with these values our model explains a diversity of earthquake phenomena such as the magnitude frequency relation the seismic gap and the magnitude gap the magnitude difference between a main shock and its largest aftershock the occurrence of multiplet earthquakes the generation of high frequency seismic waves the incoherency of the near field acceleration and the recent observation by furumoto and nakanishi that the main rupture is often preceded by a precursory rupture whose time duration in general scales with seismic moment

structures and sedimentary deposition in the sunda strait indonesia abstract the sunda strait lies between the islands of java and sumatra and separates the nearly orthogonal subduction along the south of java and oblique subduction beneath sumatra the sumatra fault accommodating most of the trench parallel shear of the oblique subduction initiates in the sunda strait this setting implies that the sunda strait is an attractive area to study the geodynamic evolution of the western indonesian region thirteen multichannel seismic lines acquired in the sunda strait have allowed a detailed study of the structure sedimentation patterns and volcanic activities that occurred in the sunda strait the sunda strait evolution has been strongly tied with the development of the sumatra fault in this area the opening of the sunda strait initiated in the early late miocene following the commencement of the sumatra fault system in the middle miocene since then three major graben systems have been evolved which are referred to as the west and east semangko grabens and the krakatau graben these graben systems can be regarded as pull apart basins developed within the releasing fault overstep area in between the main strand of the sumatra fault and its relay faults south off ujung kulon prior to the late miocene most of the sunda strait and the surroundings probably developed in a non marine environment in late miocene the sunda strait started to open and volcanism began and has been the main source of clastics three major sedimentary units can be identified which represent late miocene pliocene and pleistocene sediments respectively the late miocene unit has been developed in the shelfal area on top of the middle miocene unconformity following a relative rapid sea level rise and a subsequent highstand prior to the sea level fall at the end of miocene its lower part has syn structurally been deposited into the late miocene basement block faulting the early deposition of the pliocene unit was in response to the pliocene sea level rise and abundant clastic supply the deposition became very rapid due to graben formation combined with stronger volcanism however its lateral distribution was confined by uplift of ridges within the grabens

the bright spot of an earthquake abstract umeda y 1992 the bright spot of an earthquake in t mikumo k aki m ohnaka l j ruff and p k p spudich editors earthquake source physics and earthquake precursors tectonophysics 211 13 22 field surveys in the source region for some large shallow earthquakes reveal that there is a special spot characterized by high acceleration aftershock gap and parallel faults system this spot is called an earthquake bright spot which occupies a relatively small region compared to the final rupture region at least two kinds of phases p1 and p2 which are responsible for the rupture initiation and the bright spot formation can be identified on the broad band seismograms for large earthquakes duration times of preliminary waves p1 p2 are proportional to the earthquake magnitudes by using this evidence from the field and seismograms a model having three rupture stages is proposed for a growth process of large earthquakes the 1st stage is an initiation and propagation of rupture the 2nd stage is formation of the bright spot which produces the high frequency seismic waves in the 3rd stage smooth dislocations again propagate in bi laterally and radiate the long period seismic waves

near field high resolution strain measurements prior to the october 18 1989 loma prieta ms 7 1 earthquake high resolution strain recordings were made in deep boreholes throughout california prior to during and following the october 18 1989 ms 7 1 loma prieta earthquake the nearest dilational strainmeters sensitivity 1010 and 3 component tensor strainmeters sensitivity 10 9 were 37 km to 42 km respectively from the main shock high quality data including details of strain offsets were recorded on both instruments through the earthquake these data have been searched for indications of short intermediate and long term strain redistribution and or fault slip that might have indicated imminent rupture short and intermediate term changes in both tensor strain and dilational strain several nanostrain if any during the minutes to months before the earthquake are at least 1000 times smaller than that generated by the earthquake itself if short term preseismic slip did occur at the nucleation point of the earthquake during the previous week and if the type of slip is similar to that during the earthquake its moment could not be more than 1024 dyne cm stated another way slip equivalent to that expected for a m 5 3 earthquake could have occurred in the hypocentral region without the strainmeters detecting it at these distances and azimuthal positions long term changes appear to have occurred in mid 1988 and mid 1989 these changes were both followed by ml 5 earthquakes in the hypocentral region on june 27 1988 and august 8 1989 respectively and since they correspond approximately to changes in geodetic strain rate over the epicenter may indicate precursory strain redistribution in the epicentral region minor postseismic strain recovery 14 occurred in the month following the main shock

a theoretical comparison of tsunamis from dislocations and landslides we use simple physical models to evaluate and compare the orders of magnitude of the energy generated into a tsunami wave by seismic dislocations and underwater slumps we conclude that the two sources can generate tsunamis of comparable total energy however the slumping source is shown to be fundamentally dipolar in nature which results in a low frequency deficiency in the far field these simple conclusions corroborate the interpretation of the 1998 papua new guinea tsunami as being generated by an underwater slump

the december 2018 anak krakatau volcano tsunami as inferred from post tsunami field surveys and spectral analysis we present analysis of the december 2018 anak krakatau tsunami in sunda strait indonesia from a combination of post tsunami field surveys bathymetric changes and spectral analysis of the tsunami tide gauge records post tsunami surveys revealed moderate tsunami height along the coast of sumatra and java with maximum surveyed runup of 13 5 m and maximum inundation distance of 330 m at small islands located close to the volcano extreme tsunami impacts were observed indicating not only a huge tsunami was generated by large amounts of collapse material which caused notable changes of seafloor bathymetry but also indicates the role of those small islands in reducing tsunami height that propagated to the mainland of indonesia our spectral analysis of tide gauge records showed that the tsunami s dominant period was 6 6 7 4 min indicating the short period nature of the 2018 sunda strait tsunami

earthquake nucleation on faults with rate and state dependent strength abstract dieterich j h 1992 earthquake nucleation on faults with rate and state dependent strength in t mikumo k aki m ohnaka l j ruff and p k p spudich editors earthquake source physics and earthquake precursors tectonophysics 211 115 134 faults with rate and state dependent constitutive properties reproduce a range of observed fault slip phenomena including spontaneous nucleation of slip instabilities at stresses above some critical stress level and recovery of strength following slip instability calculations with a plane strain fault model with spatially varying properties demonstrate that accelerating slip precedes instability and becomes localized to a fault patch the dimensions of the fault patch follow scaling relations for the minimum critical length for unstable fault slip the critical length is a function of normal stress loading conditions and constitutive parameters which include dc the characteristic slip distance if slip starts on a patch that exceeds the critical size the length of the rapidly accelerating zone tends to shrink to the characteristic size as the time of instability approaches solutions have been obtained for a uniform fixed patch model that are in good agreement with results from the plane strain model over a wide range of conditions above the steady state stress the logarithm of the time to instability linearly decreases as the initial stress increases because nucleation patch length and premonitory displacement are proportional to dc the moment of premonitory slip scales by d3c the scaling of dc is currently an open question unless dc for earthquake faults is significantly greater than that observed on laboratory faults premonitory strain arising from the nucleation process for earthquakes may by too small to detect using current observation methods excluding the possibility that dc in the nucleation zone controls the magnitude of the subsequent earthquake then the source dimensions of the smallest earthquakes in a region provide an upper limit for the size of the nucleation patch

lituya bay landslide impact generated mega tsunami 50th anniversary on july 10 1958 an earthquake mw 8 3 along the fairweather fault triggered a major subaerial landslide into gilbert inlet at the head of lituya bay on the southern coast of alaska the landslide impacted the water at high speed generating a giant tsunami and the highest wave runup in recorded history the mega tsunami runup to an elevation of 524 m caused total forest destruction and erosion down to bedrock on a spur ridge in direct prolongation of the slide axis a cross section of gilbert inlet was rebuilt at 1 675 scale in a two dimensional physical laboratory model based on the generalized froude similarity a pneumatic landslide tsunami generator was used to generate a high speed granular slide with controlled impact characteristics state of the art laser measurement techniques such as particle image velocimetry piv and laser distance sensors lds were applied to the decisive initial phase with landslide impact and wave generation as well as the runup on the headland piv provided instantaneous velocity vector fields in a large area of interest and gave insight into kinematics of wave generation and runup the entire process of a high speed granular landslide impact may be subdivided into two main stages a landslide impact and penetration with flow separation cavity formation and wave generation and b air cavity collapse with landslide run out and debris detrainment causing massive phase mixing formation of a large air cavity similar to an asteroid impact in the back of the landslide is highlighted a three dimenional pneumatic landslide tsunami generator was designed constructed and successfully deployed in the tsunami wave basin at osu the lituya bay landslide was reproduced in a three dimensional physical model at 1 400 scale the landslide surface velocities distribution was measured with piv the measured tsunami amplitude and runup heights serve as benchmark for analytical and numerical models

earthquake aftereffects and triggered seismic phenomena the physical basis for delayed aftereffects of large crustal earthquakes is analyzed these effects apparently range in scale from typical aftershocks near the source region of a prior earthquake to the triggering of groundwater and deformation related anomalies possibly including other large earthquakes at locations as much as a few hundred kilometers from the source of a great earthquake observational reports of such aftereffects are reviewed and possible mechanisms for their occurrence are discussed

field survey and numerical modelling of the december 22 2018 anak krakatau tsunami on december 22 2018 the eruption and flank collapse of the anak krakatau volcano generated a tsunami in the sunda strait causing catastrophic damage to uninhabited coastlines proximal to the source along the heavily populated shores of banten and lampung provinces in java and sumatra tsunami waves caused severe damage extensive inundation and more than 430 deaths an international tsunami survey team itst deployed 6 weeks after the event documented the tsunami effects including runup heights flow depths and inundation distances as well as sediment deposition patterns and impacts on infrastructure and the natural environment the team also interviewed numerous eyewitnesses and educated residents about tsunami hazards this itst was the first to visit and document the extreme tsunami effects on the small islands in the sunda strait closest to anak krakatau rakata panjang sertung sebesi and panaitan along the steep slopes of rakata and sertung islands located less than 5 km from and facing directly towards the southwest flank of anak krakatau all of the dense coastal vegetation was stripped to bare earth up to elevations of more than 80 m while on the northeast tip of sertung island facing away from the source a single tree remained standing after flow depths of 11 m above ground struck there the runup distributions on the islands encircling anak krakatau highlight the directivity of the tsunami source suggesting that the collapse occurred towards the southwest this manifested as tsunami runup of 10 m that stripped away coastal forests to bare rock for up to 400 m inland in the ujung kulon national park located 50 km to the south southwest inundation and damage were mostly limited to within 400 m of the shoreline likely the result of the relatively short wavelengths caused by the landslide generated tsunami a significant variation in tsunami impact was observed along the shorelines of the sunda strait with runup heights rapidly decreasing with distance from the inferred tsunami source to model the event we applied a hot start initial condition that roughly reproduced the measured tsunami runup heights along rakata and sertung the waveforms were then propagated through the sunda straight using a boussinesq type wave model the results showed a good fit to the observed heights along the java and sumatra coastlines the northern coast of panaitan island and ujung kulon nation park the model also produced an acceptable fit to the observed amplitudes at tide gauges despite the regional volcanic and tsunamigenic history of the region and 6 months of eruptive activity prior to the event the tsunami largely caught the local population off guard this further highlights the need for community based education and awareness programs as essential to save lives in locales at risk from locally generated tsunamis

a constitutive law for rate of earthquake production and its application to earthquake clustering seismicity is modeled as a sequence of earthquake nucleation events in which the distribution of initial conditions over the population of nucleation sources and stress ing history control the timing of earthquakes the model is implemented using solutions for nucleation of unstable fault slip on faults with experimentally derived rate and state dependent fault properties this yields a general state variable constitutive formulation for rate of earthquake production resulting from an applied stressing history to illustrate and test the model some characteristics of seismicity following a stress step have been explored it is proposed that various features of earthquake clustering arise from sensi tivity of nucleation times to the stress changes induced by prior earthquakes the model gives the characteristic omori aftershock decay law and interprets aftershock parameters in terms of stress change and stressing rate earthquake data appear to support a model prediction that aftershock duration defined as the time for rates to return to the back ground seismicity rate is proportional to mainshock recurrence time observed spatial and temporal clustering of earthquake pairs arises as a consequence of the spatial depen dence of stress changes of the first event of the pair and stress sensitive time dependent nucleation applications of the constitutive formulation are not restricted to the simple stress step models investigated here it may be applied to stressing histories of arbitrary complexity the apparent success at modeling clustering phenomena suggests the possibil ity of using the formulation to estimate short to intermediate term earthquake probabil ities following occurrence of other earthquakes and for inversion of temporal variations of earthquake rates for changes in driving stress

numerical modelling of a landslide generated tsunami the 1979 nice event on the 16th of october 1979 a part of the nice new harbour extension close to the nice international airport french riviera slumped into the mediterranean sea during landfilling operations a submarine slide with initial volume close to seashore of about 10 millions m3 which could have evolved later into an avalanche was followed by a small tsunami noticed by several witnesses in the baie des anges the maximum tsunami effects were observed 10 km from the slide location near antibes city which was inundated previous analyses used rough approximate methods and produced models which did not conveniently fit data in this paper both the slide and the generated water waves are numerically simulated on the basis of the shallow water approximation the landslide is assimilated to a heavy newtonian homogeneous fluid downslope under gravity water waves are generated by sea bottom displacements induced by the landslide taking into account a very accurate multibeam bathymetric map the nice slide of 10 millions m3 is simulated by this model the numerical results are generally consistent with the observed hydraulic local effects in front of the nice airport however they are not in agreement in the far field a larger and deeper landslide 2 km off nice airport is tested to quantitatively study the effects of the landslide volume on water waves generation

near field modeling of the july 17 1998 tsunami in papua new guinea modest earthquakes may trigger large submarine landslides responsible for disastrous tsunami waves as demonstrated by the papua new guinea event of july 17 1998 the relatively small earthquake was followed by unexpectedly high waves up to 15 m wiping out 3 villages and killing more than 2200 people numerical simulations show that seismic dislocation sources are not energetic enough to reproduce the observed tsunami along the coast tsunami generation by a submarine landslide has been simulated by a finite difference model assimilating the landslide to a flow of granular material long wave approximation is adopted for both water waves and the slide numerical results show that observed inundation heights are well reproduced for a volume of 4 km located 20 km offshore sliding downslope with a coulomb type friction

high amplitude seismic waves radiated from the bright spot of an earthquake abstract in the source region of a large shallow earthquake there is likely to be a small spot characterized by the production of high accelerations and a gap in the aftershocks on the seismograms of most large shallow earthquakes and on some seismograms of moderate main shocks two types of p waves may be detected the relatively low amplitude waves following phase p 1 and the predominant high frequency waves following phase p 2 the duration of the seismic waves following phase p 1 the p 1 p 2 time increases proportionately with the earthquake magnitude this fact strongly suggests that the preliminary rupture period is closely related to the radiation of the predominant high frequency seismic waves to explain the above observation the shear strain waves radiated from a moving rupture are calculated because the seismic wave velocity is generally higher than the rupture propagation velocity maximum shear strains by seismic waves usually precede the rupture front if the total shear strain which is equal to the static pre earthquake shear strain plus dynamic shear strain excited by seismic waves exceeds the critical shear strain 10 4 the secondary ruptures break out in the forward direction from the initial rupture the rupture processes of large or moderate earthquakes occur in two stages one is the initiation of rupture corresponding to phase p 1 and the other is the development of secondary ruptures triggered by seismic shear strain waves the latter process generates an earthquake bright spot which radiates high amplitude seismic waves

theory of time dependent rupture in the earth at a velocity x which is a well defined function of k this propagation is stable and quasi static and is referred to as subcritical crack growth we shall use the terms stable quasistatic and subcritical to mean propagation at velocities much less than the sonic velocities of the medium this behavior results from stress induced corrosion at the crack tip the principal corrodent for the present application being h20 this behavior has been firmly established in the laboratory for mode i tensile cracks in a wide variety of materials ineluding silicates and silicate glasses see cholz 1968a 1972a martin 1972 wiederhorn and bolz 1970 atkinson 1979 lawn and wilshaw 1975 knott 1973 the form of the relationship between k and x does not vary significantly with the material only the parameters in the law vary as an example we show in figure 1 data on subcritical crack growth in quartz after atkinson 1979 the empirical relationship is found to take the form