seismic source modeling seismic source modeling is taken to mean the modeling of seismograms to investigate kinematic properties of the earthquake source current trends such as the use of other data types e g geodetic measurements of coseismic deformation and the explicit consideration of source dynamics when modeling seismograms are beginning to blur this definition but i will adhere to it in this review i have divided seismic source modeling into teleseismic regional and near source modeling teleseismic modeling has the advantage of global coverage for earthquakes of magnitude 5 5 and larger but does not provide much more than point source parameters regional distance modeling has the advantage of a more rapid assessment of earthquake source properties but is complicated by relatively complex wave propagation the coverage is also limited to areas of broadband regional networks typically continental areas of developed countries near source modeling has the potential for detailed imaging of source properties but very few earthquakes occur in regions with sufficient instrumentation to allow this i have also included a section on historical earthquakes because of the additional issues that seismologists face in working with pre wwssn data and because of the important issues such as earthquake recurrence that require historical data in addition to reviewing the progress in seismic source modeling during the last four years i have also briefly reviewed some of the progress in understanding earthquake physics and hazards that has come about because of basic research in earthquake source modeling

geologic implications of great interplate earthquakes along the aleutian arc the aleutian arc is one of the most seismically active regions of the world it consists of a number of segments or blocks that are rotating clockwise and translating westward along the north american pacific plate boundary two of the largest recorded earthquakes have occurred along the interplate boundary south of the andreanof islands in 1957 and the rat islands in 1965 the large magnitudes of these earthquakes implied that the probability of the recurrence of a large magnitude event at these same locations was low however the occurrence of a great earthquake south of the andreanof islands in 1986 less than 30 years after the 1957 event has prompted a reevaluation of the seismic potential of the arc we present new marine geophysical observations and synthesize previous geologic interpretations of the aleutian arc to show that the epicenters of these great thrust type earthquakes coincide with upper plate segments of the arc characterized by a coherent forearc structural fabric these segments which are associated with large plutonic masses are mechanically stronger and are related to the location of asperities positioned at depth along the main thrust zone they appear to be more strongly attached to the north american plate than adjacent blocks the tectonically controlled locations of these asperities thus appear to influence the seismicity along the arc the andreanof and rat segments of the arc are separated by the delarof segment which is considered to have a high probability of a large magnitude earthquake in the near future based on probabilistic estimates of seismic potential nishenko 1991 the delarof segment of the arc however is highly disrupted by arc transverse faults this segment is structurally weak and does not appear to be capable of accumulating the interplate strain necessary to generate a great subduction zone earthquake we propose that variations in upper plate structural strength and mobility affect the mechanical properties of the interplate thrust zone and need to be considered in localizing interplate asperities forearc tectonic segmentation associated with the partitioning of strike slip and thrust motions may exert long term controls on the rates of seismic moment release

sources of tsunami and tsunamigenic earthquakes in subduction zones we classified tsunamigenic earthquakes in subduction zones into three types earth quakes at the plate interface typical interplate events earthquakes at the outer rise within the subducting slab or overlying crust intraplate events and tsunami earthquakes that generate considerably larger tsunamis than expected from seismic waves the depth range of a typical interplate earthquake source is 10 40km controlled by temperature and other geological parameters the slip distribution varies both with depth and along strike recent examples show very different temporal change of slip distribution in the aleutians and the japan trench the tsunamigenic coseismic slip of the 1957 aleutian earthquake was concentrated on an asperity located in the western half of an aftershock zone 1200km long this asperity ruptured again in the 1986 andreanof islands and 1996 delarof islands earthquakes by contrast the source of the 1994 sanriku oki earthquake corresponds to the low slip region of the previous interplate event the 1968 tokachi oki earthquake tsunamis from intraplate earthquakes within the subducting slab can be at least as large as those from interplate earthquakes tsunami hazard assessments must include such events similarity in macroseismic data from two southern kuril earthquakes illustrates difficulty in distinguishing interplate and slab events on the basis of historical data such as felt reports and tsunami heights most moment release of tsunami earthquakes occurs in a narrow region near the trench and the concentrated slip is responsible for the large tsunami numerical modeling of the 1996 peru earthquake confirms this model which has been proposed for other tsunami earthquakes including 1896 sanriku 1946 aleutian and 1992 nicaragua

implications of the 26 december 2004 sumatra andaman earthquake on tsunami forecast and assessment models for great subduction zone earthquakes results from different tsunami forecasting and hazard assessment mod els are compared with observed tsunami wave heights from the 26 december 2004 indian ocean tsunami forecast models are based on initial earthquake information and are used to estimate tsunami wave heights during propagation an empirical forecast relationship based only on seismic moment provides a close estimate to the observed mean regional and maximum local tsunami runup heights for the 2004 indian ocean tsunami but underestimates mean regional tsunami heights at azimuths in line with the tsunami beaming pattern e g sri lanka thailand standard forecast models developed from subfault discretization of earthquake rupture in which deep ocean sea level observations are used to constrain slip are also tested forecast models of this type use tsunami time series measurements at points in the deep ocean as a proxy for the 2004 indian ocean tsunami a transect of deep ocean tsunami amplitudes recorded by satellite altimetry is used to constrain slip along four subfaults of the m 9 sumatra andaman earthquake this proxy model performs well in comparison to observed tsunami wave heights travel times and inundation patterns at banda aceh hypothetical tsunami hazard assessments models based on end member estimates for average slip and rupture length m w 9 0 9 3 are compared with tsunami observations using average slip low end member and rupture length high end member m w 9 14 consistent with many seismic geodetic and tsunami inversions adequately estimates tsunami runup in most regions except the extreme runup in the western aceh province the high slip that occurred in the southern part of the rupture zone linked to runup in this location is a larger fluctuation than expected from standard stochastic slip models in addition excess moment release 9 deduced from geodetic studies in comparison to seismic moment estimates may gen erate additional tsunami energy if the exponential time constant of slip is less than approximately 1 hr overall there is significant variation in assessed runup heights caused by quantifiable uncertainty in both first order source parameters e g rupture length slip length scaling and spatiotemporal complexity of earthquake rupture

evidence of crustal thickening beneath the central apennines italy from teleseismic receiver functions abstract we computed receiver functions of teleseismic events that occurred within a distance of 35 90 and were recorded in central italy by 15 temporary stations and 1 permanent station in the receiver functions we identified the p to s phase converted at the moho discontinuity beneath each station and estimated crustal thickness from the time delay of this phase with respect to the direct p arrival for the temporary stations this relatively simple approach is justified given their limited recording period to the permanent station we also applied the slant stacking technique to try to constrain the bulk crustal vp vs and validate our estimate of crustal thickness our results show that in central italy the moho is shallow 22 km beneath the tyrrhenian margin of the peninsula and deepens toward the east beneath the central apennines moho depth ranges from 39 to 47 km the thickest crust matches the highest topography at the tremiti islands in the adriatic sea crustal thickness is 33 km while our moho depths beneath the tyrrhenian side of the peninsula and the adriatic sea are in agreement with previous results a new result of this study is the crustal thickening beneath the central apennines this leads to the conclusion that the central apennine topography is supported by a significant crustal root

inferences on the upper crustal structure of southern apennines italy from seismic refraction investigations and subsurface data abstract this paper presents an interpretation of crustal seismic refraction data from the northern sector of the southern apennines thrust belt a region that in historical times experienced large destructive earthquakes the data were acquired in 1992 along a seismic line 75 km long and parallel to the apenninic chain in order to determine a detailed 2 d p wave velocity model of the upper crust in an area that had not been deeply investigated by geophysical methods previously we have used a 2 d ray tracing technique based on asymptotic ray theory to model travel times of first and reflected p wave arrivals synthetic seismograms have been produced by finite difference simulations in order to check the reliability of the velocity model inferred by ray tracing modelling the interpretation of the velocity model is constrained by stratigraphic and sonic velocity logs from wells for oil exploration located close to the seismic line gravity data modelling allows to check the velocity model and to extend the structural interpretation in 3 d in the shallow crust up to a depth of 3 4 km strong lateral variations of the modelled velocities are produced by the overlapping of thrust sheets formed by 1 cenozoic flyschoid cover and basinal successions that underlie the seismic profile with p wave velocities in the 2 8 4 1 km s range and thicknesses varying between 0 5 and 4 5 km 2 mesozoic basinal sequences with a velocity of 4 8 km s and a depth of 1 5 2 1 km in the northern part of the profile 3 mesozoic limestones of the western carbonate platform with a velocity of 6 0 km s and a depth of 0 1 0 8 km in the southern part of the profile at a greater depth the model becomes more homogeneous a continuous seismic interface 3 0 4 5 km deep with a velocity of 6 0 km s is interpreted as the top of the meso cenozoic carbonate multilayer of the apulia platform characterized by an increase in seismic velocity from 6 2 to 6 6 km s at depths of 6 7 km a lower p wave velocity about 5 0 km s is hypothesized at depths ranging between 9 5 and 11 km as inferred by commercial seismic lines and data from two deep wells located in the apulia foreland and bradano foredeep this low velocity layer can be related to permo triassic clastic deposits drilled at the bottom of the apulia platform seismic data do not allow us to identify possible deeper seismic interfaces that could correspond to the top of the paleozoic crystalline basement this is probably due to the low velocity layer at the bottom of the carbonate multilayer that reflects and attenuates a great part of the seismic energy the joint interpretation of seismic refraction and well data in accordance with gravity data provides the first detailed p wave velocity model of the upper crust of the northern sector of the southern apennines which differs considerably from previous 1 d velocity models used to study the seismicity of the region and reveals new information about the structure of the thrust belt

the lithosphere asthenosphere system in the calabrian arc and surrounding seas southern italy a fairly detailed structural model of the lithosphere asthenosphere system thickness s and p wave velocities of the crust and of the uppermost mantle layers has been defined in the calabrian arc region southern tyrrhenian sea calabria and the northwestern part of the ionian sea in southern italy using seismic data from literature as a priori constraints of the nonlinear inversion of surface wave data

v s crustal models of the roccamonfina volcano and relationships with neapolitan volcanoes southern italy shear wave velocities of the crust and upper mantle are defined beneath the roccamonfina volcano and surrounding apennines southern italy from the simultaneous nonlinear inversion of the local group velocity dispersion data obtained from seismic events recorded in 1988 2004 at roccamonfina station of the ingv rsnc network and regional dispersion data obtained in previous studies the main features of the representative vs models are a carbonatic basement and a low velocity zone at 6 10 km of depth the sedimentary succession is 5 km thick below the roccamonfina volcano and lays above a high vs 3 8 km s ascribable to solidified magma body while it is 10 km thick below the surrounding apennines a low velocity layer with an average thickness of 10 km is detected below the roccamonfina volcano which can be associated with the presence of partial melting and interpreted as magmatic reservoir such low velocity layer also found below the surrounding apennines but with a reduced thickness of 2 3 km extends to the campanian plain and to the neapolitan volcanic area from campi flegrei to somma vesuvius

inversion of tsunami waveforms for the estimation of heterogeneous fault motion of large submarine earthquakes the 1968 tokachi oki and 1983 japan sea earthquakes waveform inversion of tsunami data provides independent and reliable information on earthquake source processes the propagation effects of tsunamis are accounted for by computing green s functions using a finite difference method and using the known bathymetry which is much better constrained than the seismic velocity structure the observed tsunami waveforms are corrected for the response of the tide gage system by using the results of in situ measurements using green s functions computed from bathymetric data on a 2 5 km grid and the observed waveforms digitized at 1 min intervals the spatial resolution of the faulting heterogeneity by the present method is as small as 30 km this method is applied to the 1968 tokachi oki and 1983 japan sea earthquakes the slip is concentrated at the northwestern part of the fault plane for the 1968 event for the 1983 event the slip on the fault just north of the epicenter is twice that of the other parts these asperity distributions are similar to those inferred from seismic wave analysis however the recovered total seismic moments are smaller the present method is shown to be a useful technique for estimating heterogeneous fault motion especially for historical events with no or poor seismic records and tsunami earthquakes in which the excitations of seismic and tsunami waves are different

origin of the calderas and evolution of roccamonfina volcano roman region italy abstract the roccamonfina volcano consists of a volcanic fluvial succession dated 549 ka bp paleoauruncus overlain by a 546 ka bp stratacone main cone formed by leucite bearing lava and tephra the main cone was dissected by four nested calderas a ring fracture concentric with and outside of the central caldera is also present detailed mapping of the volcano inspection of landsat satellite images and radiometric dating establish that the gli stagli and northern calderas subsided between respectively 546 474 and 403 374 ka bp and that the summit part collapsed between 546 and 446 ka bp to form the central caldera a chronologically intermediate state dated in the range 376 323 ka bp was identified between the 549 374 ka bp leucite bearing high k series hks stage i and the 317 96 ka bp leucite free low k series lks stage ii this stage is made up of concurrent hks lks rocks stage ics the central gli stagli and northern calderas are older than blt and wtt as supported by the strong discrepancies between calculated volumes of these pyroclastic rocks and the volume of the caldera also caldera collapses due to sector sliding are improbable as tested by the absence of rock slide avalanche deposits the collapses occurred incrementally through repetitive draining of the magma chamber s resulting from a succession of moderate sized volcanic events gli stagli caldera was infilled by a lake early after collapse so that sediments alternated with leucite tephrite lava flows and tephra within the lake the sequence was overlain by a thick succession of young pyroclastic rocks downfaulting downsagging cut the flat lying gli stagli filling sequence resulting in the old valle caldera successive pyroclastic and debris flows derived by updoming of the central caldera deposits infilled the last structure and downfaulted part of the valle fill producing the young valle caldera

noncharacteristic behavior and complex recurrence of large subduction zone earthquakes the last few years have been remarkable with respect to the number of large underthrusting earthquakes in subduction zones that reruptured plate boundary segments that failed in previous great events availability of modern seismic data for two consecutive large earthquakes rupturing the same portion of the plate interface provides the opportunity to compare the spatial distribution of moment release for both events such comparisons have been made for the plate boundary segments that failed in 1 the 1957 mw 8 6 1986 mw 8 0 and 1996 mw 7 9 aleutian islands earthquakes 2 the 1963 mw 8 5 and 1995 mw 7 9 kuril islands earthquakes 3 the 1971 mw 8 0 and 1995 mw 7 7 solomon islands earthquakes and 4 the 1968 mw 8 2 and 1994 mw 7 7 northern honshu earthquakes the spatial distribution of moment release for all four of the initial great earthquakes and two of the repeat events has been determined in previous studies here slip distributions for the three most recent events are determined from inversion of source time functions derived by empirical greens function analysis of long period surface waves and broadband body waves comparisons of the spatial distribution of moment release for sequential earthquake ruptures reveal considerable differences in the pattern of recurrent fault slip the 1994 northern honshu and 1995 solomon islands earthquakes primarily fill in areas of slip deficit left by their preceding events rather than rerupture identical asperities the 1995 kuril islands and the 1996 aleutian islands earthquakes both rerupture portions of an asperity distribution defined by preceding events but with variable amounts of slip this study provides the first direct evidence that recurrence of large circum pacific plate boundary events is more complex than repeat rupture of dominant asperities recurrent fault slip for the four plate boundary segments studied does not support characteristic slip models either where failure on an entire fault segment occurs repeatedly in events with nearly identical rupture lengths locations and slip magnitudes or where failure of individual asperities occurs with identical slip functions through consecutive earthquake cycles these sequential slip patterns are not consistent with physical models of earthquake rupture where slip complexity is exclusively controlled by invariant geometric and or material heterogeneity but suggest that dynamic considerations are also important

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

seismic cycles along the aleutian arc analysis of seismicity from 1957 through 1991 we catalog and relocate aleutian arc seismicity between 1957 and 1991 two great earthquakes ruptured the same 250 km long portion of the central aleutian arc the 1957 aleutian islands earthquake and the 1986 andreanof islands earthquake because accurate estimates of the moment distribution of the 1957 earthquake are not available the spatial distribution of aftershocks for each of these events is compared and tested against models describing the modes of occurrence of great subduction zone earthquakes earthquake relocations are based on p wave arrival times published in the international seismological summary the bureau central international seismologique and the international seismological centre bulletins and include corrections for the near source velocity structure associated with the down going slab magnitude estimates are extracted from bulletins and prior to 1964 are estimated by us from microfilmed records our catalog is complete above magnitude 5 5 aftershocks associated with the 1957 and 1986 earthquakes appear to occur in different areas east of the main shock epicenters aftershock locations are anticorrelated west of the main shock epicenter aftershocks of the 1986 earthquake tended to concentrate along the updip edge of aftershock clusters associated with the 1957 earthquake if we assume aftershocks rim the distribution of seismic moment release associated with each event these observations imply that the moment distribution of the 1986 earthquake was different from that of the 1957 earthquake this suggests that we should use caution in identifying mechanically strong portions of a fault asperities by simply mapping the moment distribution of a single great earthquake a fundamental tenet of the asperity model that rupture always occurs on the strongest portions of the fault with weaker portions rupturing either aseismically or dynamically as a result of rupture on a strong fault patch may in the case of the central aleutian arc not be correct thus observing the moment distribution from a single great earthquake may tell us little about what the distribution of moment release will look like during the next earthquake

post collapse volcanic history of calderas on a composite volcano an example from roccamonfina southern italy roccamonfina part of the roman potassic volcanic province is an example of a composite volcano with a complex history of caldera development the main caldera truncates a cone constructed predominantly of this caldera may have been associated with one of the ignimbritic eruptions of the brown leucitic tuff blt around 385 000 yr bp the campagnola tuff the youngest ignimbrite of the blt however drapes the caldera margin and must postdate at least the initial stages of collapse during the subsequent history of the caldera there were several major explosive eruptions the largest of these was that of the galluccio tuff at about 300 000 yr bp it is likely that there was further collapse within the main caldera associated with these eruptions it is of note that despite these subsequent major explosive eruptions later collapse occurred within the confines of the main caldera between eruptions caldera lakes developed producing numerous lacustrine beds within the caldera fill extensive phases of phreatomagmatic activity generated thick sequences of pyroclastic surge and fall deposits activity within the main caldera ended with the growth of a large complex of basaltic trachyandestite lava domes around 150 000 yr bp early in the history of roccamonfina sector collapse on the northern flank of the volcano formed the northern caldera one of the youngest major events on roccamonfina occurred at the head of this northern caldera with explosive activity producing the conca ignimbrite and associated caldera there is no evidence that there was any linkage in the plumbing systems that fed eruptions in the main and northern calderas

detection and characterization of transient forcing episodes affecting earthquake activity in the aleutian arc system abstract crustal slow deformation transients can be caused by fluid or magmatic intrusions and by slow slip on faults they can affect earthquake dynamics if they occur close to or within seismically active zones we here further develop and test a statistical method for detecting and characterizing seismicity anomalies that is only based on earthquake occurrence times and locations we make use of this method to analyze the 2004 2013 seismicity at m c 3 5 in the aleutian subduction system to find six statistically significant anomalies with typical 1 day duration and 30 to 50 km size that are likely related to slow deformation transients they tend to be located in zones characterized by intermediate seismic coupling and to mark the termination of past large to mega thrust earthquakes these anomalies account for a non negligible 9 part of the total activity proving that non stationary aseismic loading plays an important role in the dynamics of crustal deformation

locating and quantifying the seismic discontinuities in a complex medium through the migration and ava analysis of reflected and converted waves an application to the mt vesuvius volcano summary in this paper we show how the migration of active seismic data can be used to identify and position a seismic discontinuity in a complex medium and how the amplitude variations of the converted p to s waves can be interpreted to constrain the seismic velocities below the interface for the application we turn our attention on mt vesuvius an active volcano threatening a densely populated area to better define its plumbing system we investigate a mid crust seismic discontinuity first identified by zollo et al 1996 science 274 592 594 and assumed to be the top of a layer containing low velocity material we deduce a reference velocity model from previous works on first arrival times and use it to migrate pp reflected and ps converted waves in the migration image the interface extends at least 20 000 m ne and 20 000 m sw of the volcano at the depth of 8000 m and with a mean dip less than 3 per cent the migration of finite difference synthetics exclude the fact that the migrated phases interpreted as 8000 m deep reflections or conversions might be multiples in the shallow layers the ps and first arrival amplitudes are compared at a fixed station and for all the shots to determine the variations of the p to s conversion coefficient with the angle of incidence it appears to vary very slowly over the whole range of incidence angle at disposal 50 80 this implies a dramatic drop of s wave velocity from approximately 3600 m s 1 above to less than 1000 m s 1 below the interface the smoothness of the variations indicate that the p wave velocity also diminishes across the interface the very low s wave velocity other geophysical observations at vesuvius and in other volcanic systems lead to the conclusion that below the 8000 m discontinuity there is a very extended layer of hot partially molten material

meteorological controls on glacier mass balance empirical relations suggested by measurements on glacier de sarennes france glacial mass balance reconstruction for a long term time scale requires knowledge of the relation between climate change and mass balance fluctuations a large number of mass balance reconstructions since the beginning of the century are based on statistical relations between monthly meteorological data and mass balance the question examined in this paper is are these relationships reliable enough for long term time scale extrapolation from the glacier de sarennes long mass balance observations series we were surprised to discover large discrepancies between relations resulting from different time periods the importance of the albedo in relation to ablation and mass balance is highlighted and it is shown that it is impossible to ignore glacier surface conditions in establishing the empirical relation between mass balance fluctuations and climatic variation to omit this parameter leads to incorrect results for mass balance reconstruction in the past based on meteorological data

source parameters of the 1957 aleutian earthquake from tsunami waveforms we studied the source parameters of the 1957 aleutian earthquake using tsunami waveform data recorded on tide gauges around the pacific ocean using a finite difference computation this tsunami can be numerically simulated the tsunami records were inverted for the slip distribution on the rupture area results show that slip was concentrated in the western half of the aftershock zone with a maximum displacement of 7m the moment computed from the slip distribution is 88 1020 nm giving the 1957 earthquake a moment magnitude of mw 8 6 the waveform inversion confirms that no slip occurred in the unalaska island area making this area a possible seismic gap with a potential to rupture in a great earthquake and generate a pacific wide tsunami

high altitude varve records of abrupt environmental changes and mining activity over the last 4000 years in the western french alps lake bramant grandes rousses massif abstract two twin short gravity cores and a long piston core recovered from the deepest part of proglacial lake bramant grandes rousses massif french alps under and overlying a large slump identified by high resolution seismic profile allow the investigation of holocene natural hazards and interactions between human activity and climatic changes at high altitude annual sedimentation throughout the cores glacial varves is identified on photographs itrax high resolution continuous microfluorescence x and cat scan computerized axial tomography analyses and is supported by 1 the number of dark and light laminations between dates obtained by radionuclide measurements 137cs 241am 2 the correlation of a slump triggered by the nearby ad 1881 allemond earthquake msk intensity vii and of a turbidite triggered by the ad 1822 chautagne regional earthquake msk intensity viii 3 the number of laminations between two accelerator mass spectrometry ams 14c dates and 4 archaeological data in lake bramant dark layers are coarser contain less detrital elements but more neoformed elements and organic matter content these darker laminations result from calm background sedimentation whereas the lighter layers are finer and rich in detrital elements and reflect the summer snowmelt traces of mining activity during the roman civilization apogee ad 115 330 and during the early bronze age 3770 3870 cal bp are recorded by lead and copper content in the sediments and probably result from regional and local mining activity in the nw alps warmer climate during the bronze age in this part of the alps is suggested by 1 two organic deposits 4160 3600 cal bp and 3300 2850 cal bp likely reflecting a lower lake level and smaller glaciers and 2 evidence of a different vegetation cover around 2500 m a s l the onset of clastic proglacial sedimentation between 3600 3300 cal bp and since 2850 cal bp is synchronous with periods of glacier advances documented in the alps and high lake levels in west central europe this major change in proglacial sedimentation highlights the development of a larger st sorlin glacier in the catchment area of lake bramant

of the may 7 1986 andreanof islands earthquake source parameters source characteristics of the may 7 1986 andreanof islands earthquake 51 412 n 174 830 w neic are investigated from wwssn gdsn and ida records first motions from over 60 stations determine one steeply dipping nodal plane we constrained this nodal plane and inverted long period surface waves at a period of t 256 sec and determined the second nodal plane to be dip 18 rake 116 and strike 257 this shallowly dipping thrust mechanism is consistent with plate motions in this region seismic moment from surface wave inversion is 1 3 1028 dyne cm corresponding to mw 8 0 amplitudes of body and surface waves from short period instruments yield magnitudes of and ms 7 7 the teleseismic average p wave moment rate spectrum from 17 short and intermediate period instruments is slightly lower than that of an average mw 8 0 subduction zone event we constrained the fault plane as determined above to deconvolve the first 90 secs of the long period body wave at 11 teleseismic stations to determine the source time function and the spatial distribution of moment release the source time function consists of 4 moment releasing episodes which have a total moment release of 9 4 1027 dyne cm the fault ruptured bilaterally with the largest moment releasing subevent occurring between 30 45 sec this subevent nucleates approximately 75 90 km west of the determined epicenter this region corresponds to the epicentral area of the 1957 great aleutian earthquake which is one of the largest earthquakes in recorded history

a comparison of the spatio temporal distribution of moment release for the 1986 andreanof islands earthquake with relocated seismicity we compare relocated teleseismically recorded seismicity before and after the may 7 1986 andreanof islands earthquake mw 8 to the spatial and temporal distribution of seismic moment release during the mainshock relocated seismicity from 1964 through april 1987 clusters strongly along the main thrust zone in similar locations for the pre and post mainshock periods we performed simultaneous iterative inversions of broadband teleseismic gdsn and nars p waveforms using the method of kikuchi and fukao 1987 fault plane parameters e g strike dip depth and extent of fault plane consistent with regional tectonics and aftershock locations were specified the results of the inversions are spatial and temporal maps of moment release on the fault plane most of the moment found by the inversion is localized in several regions of the fault plane resolution of the location and timing of the major subevents is good the rupture was bilateral with a highly variable rupture velocity a shallow updip region of the fault plane ruptured toward the end of the mainshock process the mainshock moment release tended to occur in regions of the fault plane in which no or few aftershocks or preshocks are located this tendency suggests that regions of high moment release in the 1986 andreanof islands earthquake resulted from rupture of mechanically strong regions i e asperities on the fault plane which exhibited little seismicity before or after the mainshock that ruptured them we infer that the asperity regions were locked and quiescent before the mainshock while surrounding seismically active areas did not store as much strain and slipped mostly aseismically

the rupture process and tectonic implications of the great 1964 prince william sound earthquake we have determined the rupture history of the march 28 1964 prince william sound earthquake m w 9 2 from long period wwssn p wave seismograms source time functions determined from the long period p waves indicate two major pulses of moment release the first and largest moment pulse has a duration of approximately 100 seconds with a relatively smooth onset which reaches a peak moment release rate at about 75 seconds into the rupture the second smaller pulse of moment release starts at approximately 160 seconds after the origin time and has a duration of roughly 40 seconds because of the large size of this event and thus a deficiency of on scale digitizable p wave seismograms it is impossible to uniquely invert for the location of moment release however if we assume a rupture direction based on the aftershock distribution and the results of surface wave directivity studies we are able to locate the spatial distribution of moment along the length of the fault the first moment pulse most likely initiated near the epicenter at the northeastern down dip edge of the aftershock area and then spread over the fault surface in a semi circular fashion until the full width of the fault was activated the rupture then extended toward the southwest approximately 300 km ruff and kanamori 1983 the second moment pulse was located in the vicinity of kodiak island starting at 500 km southwest of the epicenter and extending to about 600 km although the aftershock area extends southwest past the second moment pulse by at least 100 km the moment release remained low we interpret the 1964 prince william sound earthquake as a multiple asperity rupture with a very large dominant asperity in the epicentral region and a second major but smaller asperity in the kodiak island region

a new gps velocity field for the pacific plate part 1 constraints on plate motion intraplate deformation and the viscosity of pacific basin asthenosphere

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

how can one test the seismic gap hypothesis the case of repeated ruptures in the aleutians the test that kagan and jackson 1991 1995 applied to the seismic gap hypothesis did not bring us closer to understanding the generation of large earthquakes on the contrary it led some to the conclusion that the rebound theory of earthquake generation should be rejected we disagree with this point of view and argue that a global test of the simplified gap hypothesis cannot be done because it cannot account for differences in the slip history of fault segments and tectonic differences between separate plate boundaries kagan and jackson did show however that the original gap hypothesis was oversimplified and should be refined we propose that consideration of all the facts including slip history and seismicity patterns in the andreanof islands show that the concept of seismic gaps and the elastic rebound theory are correct for that segment of the plate boundary the coseismic slip in the m w 8 7 earthquake that broke this plate boundary segment in 1957 was only 2 m as published before the repeat earthquake of 1986 m w 8 and thus using a plate convergence rate of 7 3 cm year the return time in this cycle was expected to be less than 30 years unless substantial aseismic creep occurs this supports the time predictable model of mainshock recurrence in addition kisslinger et al 1985 and kisslinger 1986 noticed a seismic quiescence in the subsequent source volume before the 1986 earthquake and attempted to predict it the specific parameters he estimated were not entirely correct although his interpretation of the observed quiescence as a precursor was we conclude that the 1986 m w 8 andreanof earthquake was not an example that disproves the seismic gap hypothesis on the contrary it shows that the hypothesis that plate motions reload plate boundaries after most of the elastic energy is released in great ruptures was correct in this case this suggests that great earthquakes occur preferably in mature gaps we believe the testing of the seismic gap hypothesis by algorithm on a global scale is an example that illustrates that overly simplified tests can lead to erroneous conclusions to make progress in the actual understanding of the physics of the process of great earthquake ruptures one must consider all the facts known for case histories

stratigraphy chronology and sedimentology of ignimbrites from the white trachytic tuff roccamonfina volcano italy abstract we describe the stratigraphy chronology and grain size characteristics of the white trachytic tuff wtt of roccamonfina volcano italy the pyroclastic rock was emplaced between 317 and 230 ma bp during seven major eruptive events units a to g and three minor events units bc cd and de these units are separated by paleosol layers and compositionally well differentiated pyroclastic successions stratigraphic control is favored by the occurrence at the base of major units of marker layers four wtt units 1 to 4 occur within the central caldera these are not positively correlated with specific extracaldera units the source of most of the wtt units was the central caldera units b and c were controlled by the western wall of the caldera whereas units d and e were able to overcome this barrier spreading symmetrically along the flanks of mc the maximum pumice size mp of units increases with distance from the caldera whereas the maximum lithic size ml decreases mp and ml of the marker layer of unit d mkda mkdp do not show any systematic variations with respect to the central caldera in contrast the thickness of surge mkda decreases with distance from the source and mkdp accumulates to the north of mc probably controlled respectively by mobility transport power and by wind blowing northwards the grain size characteristics of the wtt deposits are used for classifying the units there is no systematic variation of the grain size as a function of stratigraphic height either among units or within single units large variation of components in subunit e1 with repetitive alternation of pyroclastic flow to surge through fallout vs surge deposits suggests that the process of eruption took place in a complex or piecemeal fashion pumice concentration zones pcz occur at all wtt levels on the volcano but they are much thicker and pumice clasts are much larger within the central caldera these were probably originated by the disruption of lava flow or dome to pumice fragments and fine ash due to sudden depressurization and interaction with lake waters of the molten lava local basal pcz are in some cases similar to the lapilli rich layer 1p that has been described elsewhere and may have been deposited from currents transitional between pyroclastic surge and flow other basal pcz formed in response to small undulations in the substrate or can be originated by fallout lenticular pcz within ignimbrite interiors and tops are interpreted to record marginal pumice levees and pumice rafts some of which were buried by subsequant pyroclastic flows lithic concentration zones lcz also occur at various stratigraphic height within the extracaldera ignimbrites whereas intracaldera lcz are absent probably due to the fact that ignimbrite currents are strongly energetic and erosive near vent lcz at the top of basal inversely graded layers are formed by mechanical sieving or dispersive pressure in response to variable velocity gradients and particle concentration gradients a segregation process coarse lcz and coarse lithic breccias lb that reside in the interior or tops of pyroclastic flows and that occur in medial to distal areas are interpreted to be the result of slugs of lithic rich debris introduced by vent collapse or rockslides into the moving pyroclastic flows along their flow paths these lcz become mixed to varying degrees due to differential densities and velocities relative to the pyroclastic flows desegregation processes

are icelandic rock slope failures paraglacial age evaluation of seventeen rock slope failures in the skagafjorður area based on geomorphological stacking radiocarbon dating and tephrochronology in iceland there are numerous rock slope failures especially in the tertiary basaltic formations of the northern eastern and northwestern regions the temporal pattern of rock slope failures is fundamental for understanding post glacial events in the skagafjor ur district central northern iceland 17 rock slope failures were investigated to determine the age of their occurrence a geomorphic survey was carried out to identify and characterize landform units both on the rock slope failures and in their immediate vicinity in this coastal area we used geomorphological stacking which included the relationship between rock slope failures and raised beaches caused by glacial isostatic rebounds the chronology of which was established in previous studies we searched for depressions on the rock slope failures to then excavate a series of pits and map the stratigraphy the resulting stratigraphic framework was then validated using i radiocarbon dating of wood remains and ii tephrochronology both of which were complemented by age depth model calibration the results confirm that all the rock slope failures potentially occurred before the boreal 8 ka while 94 occurred before the preboreal 10 ka they all potentially occurred after the glacial retreat following the maximal ice extent and the preboreal more precisely 11 of them potentially occurred between the preboreal and the first half of the holocene this study demonstrates the relationship between the deglaciation and destabilization of slopes during the paraglacial phase debuttressing decompression glacial isostatic rebound seismic activity etc which are also controlling factors favouring landsliding but are difficult to identify for each individual rock slope failure

indication of active overthrust faulting along the holocene wisconsin transition in the marginal zone of jakobshavn isbrae 1 a zone of highly irregular ice motion has been detected within the ice sheet adjacent to jakobshavn isbrae a fast moving ice stream in west greenland two tilt sensors in different boreholes and frozen into the ice show angle variations of up to 0 1 and 0 3 within a 1200 s interval the amplitude of these flutter oscillations increases toward the transition from holocene to wisconsin ice at 682 m depth 150 m above bedrock all other tilt sensors above and below show low background noise a numerical model confirms that the stress configuration is exceptional in the neighborhood of the ice stream stress transfer from the ice stream to the margins causes an extra forcing of the basal ice at the drill site several possible explanations for the observed flutter oscillations are given the most likely being dynamic rupture events or stick slip motion along the holocene wisconsin transition if true this would correspond to an active overthrust fault with very high loading rates

geophysical and petrological modelling of the structure and composition of the crust and upper mantle in complex geodynamic settings the tyrrhenian sea and surroundings abstract information on the physical and chemical properties of the lithosphere asthenosphere system las can be obtained by geophysical investigation and by studies of petrology geochemistry of magmatic rocks and entrained xenoliths integration of petrological and geophysical studies is particularly useful in geodynamically complex areas characterised by abundant and compositionally variable young magmatism such as in the tyrrhenian sea and surroundings a thin crust less than 10 km overlying a soft mantle where partial melting can reach about 10 is observed for magnaghi vavilov and marsili which belong to the central tyrrhenian sea backarc volcanism where subalkaline rocks dominate similar characteristics are seen for the uppermost crust of ischia a crust about 20 km thick is observed for the majority of the continental volcanoes including amiata vulsini roccamonfina phlegraean fields vesuvius vulture stromboli vulcano lipari etna and ustica a thicker crust is present at albani about 25 km and at cimino vico sabatini about 30 km the structure of the upper mantle in contrast shows striking differences among various volcanic provinces volcanoes of the roman region vulsini sabatini alban hills sit over an upper mantle characterised by vs mostly ranging from about 4 2 to 4 4 km s at the alban hills however slightly lower vs values of about 4 1 km s are detected between 60 and 120 km of depth this parallels the similar and rather homogeneous compositional features of the roman volcanoes whereas the lower vs values detected at the alban hills may reflect the occurrence of small amounts of melts within the mantle in agreement with the younger age of this volcano the axial zone of the apennines where ultrapotassic kamafugitic volcanoes are present has a mantle structure with high velocity lid vs 4 5 km s occurring at the base of a 40 km thick crust beneath the campanian volcanoes of vesuvius and phlegraean fields the mantle structure shows a rigid body dipping westward a feature that continues southward up to the eastern aeolian arc in contrast at ischia the upper mantle contains a shallow low velocity layer vs 3 5 4 0 km s just beneath a thin but complex crust the western aeolian arc and ustica sit over an upper mantle with vs 4 2 4 4 km s although a rigid layer vs 4 55 km s from about 80 to 150 km occurs beneath the western aeolian arc in sardinia no significant differences in the las structure are detected from north to south the petrological geochemical signatures of italian volcanoes show strong variations that allow us to distinguish several magmatic provinces these often coincide with mantle sectors identified by vs tomography for instance the roman volcanoes show remarkable similar petrological and geochemical characteristics mirroring similar structure of the las the structure and geochemical isotopic composition of the upper mantle change significantly when we move to the stromboli campanian volcanoes the geochemical signatures of ischia and procida volcanoes are similar to other campanian centres but sr pb isotopic ratios are lower marking a transition to the backarc mantle of the central tyrrhenian sea the structural variations from stromboli to the central vulcano and lipari and western aeolian arc are accompanied by strong variations of geochemical signatures such as a decrease of sr isotope ratios and an increase of nd pb isotope and lile hfse ratios the dominance of mafic subalkaline magmatism in the tyrrhenian sea basin denotes large degrees of partial melting well in agreement with the soft characteristics of the uppermost mantle in this area in contrast striking isotopic differences of plio quaternary volcanic rocks from southern to northern sardinia does not find a match in the las geophysical characteristics the combination of petrological and geophysical constraints allows us to propose a 3d schematic geodynamic model of the tyrrhenian basin and bordering volcanic areas including the subduction of the ionian adria lithosphere in the southern tyrrhenian sea and to place constraints on the geodynamic evolution of the whole region

rupture extent of the 1938 alaskan earthquake as inferred from tsunami waveforms using tsunami waveforms we estimate the source parameters of the 10 november 1938 alaskan earthquake the earthquake ruptured a 300 kin long segment of the alaskan arc which corresponds to the aftershock area the seismic moment is approximately 20x102o nm or mw 8 2 and the moment release was concentrated in the eastern end of the aftershock zone the tsunami and seismic evidence strongly suggest that the 1938 earthquake did not rupture into the shumagin islands gap

slope instability in relation to glacial debuttressing in alpine areas upper durance catchment southeastern france evidence from field data and 10be cosmic ray exposure ages the upper durance catchment is an area prone to rock slope failures such failures reflect the combination of high relief litho structural controls and paraglacial stress release the aim of this study is to determine the role of deglacial unloading and resulting paraglacial stress release in conditioning or triggering slope failure former dimensions of the durance glacier are reconstructed then combined with digital elevation model data in a raster geographic information system to quantify the spatial pattern of stresses associated with glacial loading at the last glacial maximum preliminary calculations suggest that major rock falls and rock avalanches are associated with areas subject to the highest decompression stresses focus on two case studies allows the consequences of paraglacial stress release on slope instability to be evaluated description of slope failure runout deposits allows reconstruction of the nature of slope failure surface exposure dates based on concentration of cosmogenic 10be allows the timing of both deglaciation and that of post glacial rock slope failures to be established it is shown that rock slope failures are concentrated on lower valley side slopes within the area occupied by ice at the last glacial maximum and that their locations coincide with zones of inferred high glacial loading stress consistent with interpretation of both bedrock disruption and large scale rock slope failures as paraglacial phenomena induced by stress release following deglaciation timing of initial rock avalanche runout deposition at one site is consistent with this conclusion though later instability episodes at the same site may have occurred independent of the influence of paraglacial stress release

extension of glacier de saint sorlin french alps and equilibrium line altitude during the little ice age glacier de saint sorlin french alps left terminal moraines at 1 3 2 9 and 3 7 km ahead of the present terminus according to proxy data and to historical maps these were formed in the 19th 18th and 17th centuries respectively a plateau at 2700 2625 m was then surrounded by ice but never became an accumulation area this fact shows that the equilibrium line altitude ela on the glacier never dropped below 2300 m the following simple models apply sufficiently to yield reliable estimations of past ela 1 a uniform and constant vertical gradient of the mass balance down to the terminus and 2 a plane bed with a slope of 8 5 and a uniform width then in a steady situation the accumulation area ratio is 1 2 compared to the mean for 1956 72 at the onset of the little ice age the balances were higher by 3 75 m ice a 1 and the ela was 400 m lower correlations between 1956 72 balances and meteorological data suggest that during the melting season the 0 c isotherm was about 800 m lower while the winter precipitation at low altitudes did not change these correlations may have been different in the past but an equal lowering of the ela and of the 0 c isotherm as assumed by several authors seems excluded

structural composition and sediment transfer in a composite cirque glacier glacier de st sorlin france robserson s 2008 structural composition and sediment transfer in a composite cirque glacier glacier de st sorlin france earth surface processes and landforms 33 13 1931 1947

a survey of methane isotope abundance 14c 13c 2h from five nearshore marine basins that reveals unusual radiocarbon levels in subsurface waters methane ch4 in the subsurface ocean is often supersaturated compared to equilibrium with the modern atmosphere in order to investigate sources of ch4 to the subsurface ocean isotope surveys 14c ch4 13 c ch4 2 h ch4 were conducted at five locations skan bay sb santa barbara basin sbb santa monica basin smb cariaco basin cb and the guaymas basin gb depth distributions of ch4 concentration and isotopic abundance were determined for both the sediment and water column at the sb sbb smb and cb sites ch4 emitted from seeps on the continental shelf adjacent to the sbb as well as seeps and decomposing clathrate hydrates in the gb was also collected purified and analyzed methane isotope distributions in the sediments were consistent with known methanogenic and methanotrophic activity seep and clathrate hydrate derived ch4 was found to be depleted in radiocarbon however surprising results were obtained in the water column at all sites investigated in sb the radiocarbon content of the subsurface ch4 concentration maximum was on average 41 less than its suspected sediment ch4 source suggesting ch4 seepage in the bay in the sbb smb and cb the 14c ch4 contents in the subsurface ocean were 1 2 to 3 6 times greater than modem carbon quantities suggesting a source of 14c from atmospheric nuclear weapons testing nuclear power plant effluents or cosmogenic isotope production copyright 2008 by the american geophysical union

composition and microstructure of magma bodies from effective medium theory summary the extent and seismic properties of magma bodies beneath the subsurface are normally ascertained via seismic methods the seismic properties of such bodies depend on the composition and microstructure of both melt and crystals using effective medium theory we assess the effect of microstructure geometry and orientation of melt and crystals on the seismic properties namely p and s wave velocities and anisotropy we find that s wave velocity and anisotropy are key observables in determining the composition and microstructure of magma bodies

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

experimental insights into the scaling and variability of local tsunamis triggered by giant subduction megathrust earthquakes 1 giant subduction megathrust earthquakes of magnitude 9 and larger pose a significant tsunami hazard in coastal regions in order to test and improve empirical tsunami forecast models and to explore the susceptibility of different subduction settings we here analyze the scaling of subduction earthquake triggered tsunamis in the near field and their variability related to source heterogeneities we base our analysis on a sequence of 50 experimentally simulated great to giant mw 8 3 9 4 subduction megathrust earthquakes generated using an elastoplastic analog model experimentally observed surface deformation is translated to local tsunami runup using linear wave theory we find that the intrinsic scaling of local tsunami runup is characterized by a linear relationship to peak earthquake slip an exponential relationship to moment magnitude and an inverse power law relationship to fore arc slope tsunami variability is controlled by coseismic slip heterogeneity and strain localization within the fore arc wedge and is characterized by a coefficient of variation cv 0 5 wave breaking modifies the scaling behavior of tsunamis triggered by the largest mw 8 5 events in subduction settings with shallow dipping 1 2 fore arc slopes limits tsunami runup to 30 m and reduces its variability to cv 0 2 the resulting effective scaling relationships are validated against historical events and numerical simulations and reproduce empirical scaling relationships the latter appear as robust and liberal estimates of runup up to magnitude mw 9 5 a global assessment of tsunami susceptibility suggests that accretionary plate margins are more prone to tsunami hazard than erosive margins

velocities strain rates stresses crevassing and faulting on glacier de saint sorlin french alps 1957 76 stake surveys on glacier de saint sorlin french alps during the period 1957 76 show that annual surface velocities fit a linear vectorial model with a term depending on the site another on the year and an important random component strain rates viscosities and stresses at shallow depth are computed using strain triangles ofhectometric 10 2 m size between 1961 62 and 1972 73 the isotropic point where streamlines cease to converge moved downstream about 200 m this trend may explain increasing velocities crevasses appear where annual strain is 1 2 faults limit the effective shear stress at the surface to about 0 38 bar ten modes of flow are distinguished instead of only two for the two dimensional model compressive and extensive the gradients of shallow stresses which ensure extra driving forces are computed with another mosaic of triangles of similar size stress triangles there are also important extra driving forces at the bottom which force the flow to deviate from the direction of the steepest surface slope two criteria allow elimination of stress triangles where these unknown basal extra driving forces are important even so no sliding law in terms of mean annual values can be obtained this study shows that the classical perturbation theory which explains advances and retreats by the arrival of kinematic waves is unsuitable for glaciers of kilometric size

complex earthquake rupture and local tsunamis 1 in contrast to far field tsunami amplitudes that are fairly well predicted by the seismic moment of subduction zone earthquakes there exists significant variation in the scaling of local tsunami amplitude with respect to seismic moment from a global catalog of tsunami runup observations this variability is greatest for the most frequently occurring tsunamigenic subduction zone earthquakes in the magnitude range of 7 mw 8 5 variability in local tsunami runup scaling can be ascribed to tsunami source parameters that are independent of seismic moment variations in the water depth in the source region the combination of higher slip and lower shear modulus at shallow depth and rupture complexity in the form of heterogeneous slip distribution patterns the focus of this study is on the effect that rupture complexity has on the local tsunami wave field a wide range of slip distribution patterns are generated using a stochastic self affine source model that is consistent with the falloff of far field seismic displacement spectra at high frequencies the synthetic slip distributions generated by the stochastic source model are discretized and the vertical displacement fields from point source elastic dislocation expressions are superimposed to compute the coseismic vertical displacement field for shallow subduction zone earthquakes it is demonstrated that self affine irregularities of the slip distribution result in significant variations in local tsunami amplitude the effects of rupture complexity are less pronounced for earthquakes at greater depth or along faults with steep dip angles for a test region along the pacific coast of central mexico peak nearshore tsunami amplitude is calculated for a large number n 100 of synthetic slip distribution patterns all with identical seismic moment mw 8 1 analysis of the results indicates that for earthquakes of a fixed location geometry and seismic moment peak nearshore tsunami amplitude can vary by a factor of 3 or more these results indicate that there is substantially more variation in the local tsunami wave field derived from the inherent complexity subduction zone earthquakes than predicted by a simple elastic dislocation model probabilistic methods that take into account variability in earthquake rupture processes are likely to yield more accurate assessments of tsunami hazards

the 1965 rat islands earthquake a critical comparison of seismic and tsunami wave inversions we use the 1965 rat islands earthquake to compare seismic wave inversion results for moment release distributions to tsunami wave inversion results for slip distribution inversion using the two different datasets shows a high correlation between the areas of high moment release and areas of high slip these areas of high slip correspond to the tectonic features of the western aleutians namely the rat buldir and near blocks less slip is observed between the blocks the correlation indicates that far field tsunami data is as useful as seismic data for studying moment distributions

volcanic and tectonic deformation on unimak island in the aleutian arc alaska 3 3 10 6 m 3 yr 1 the gps data indicate that inflation may have slowed down slightly compared with interferometric synthetic aperture radar insar observations between 1993 and 1998 the accumulated subsurface volume increase during the gps and insar observation period 1993 2001 70 10 6 m 3 already accounts for at least 15 more than the erupted volume from the last eruption in 1991 1992 fisher caldera shows subsidence and contraction across the caldera center the data are fit best with a rectangular dislocation source at a shallow depth it is 14 km long and 0 5 km wide dips 80 to the nw and strikes n35 e with rather large uncertainties for most of these parameters its volume decrease is 2 0 10 6 m 3 yr 1 the main mechanisms to explain the subsidence and contraction are degassing and contractional cooling of a shallow magma body and depressurization of fisher s hydrothermal system possibly triggered by an earthquake in 1999 at the 95 confidence level no significant strain accumulation due to subduction is observed across the entire island the low coupling across the rupture zone of the 1946 earthquake is a strong argument for the idea that the earthquake and tsunami did not result from a purely double couple earthquake source index terms 1206 geodesy and gravity crustal movements interplate 8155 8135 tectonophysics evolution of the earth hydrothermal systems 8424 8145 tectonophysics evolution of the earth physics of magma and magma bodies 8150 tectonophysics evolution of the earth plate boundary general 3040 keywords volcanic deformation caldera deformation aleutian arc alaska unimak island citation mann d and j freymueller volcanic and tectonic deformation on unimak island in the aleutian arc alaska j geophys res 108 b2 2108 doi 10 1029 2002jb001925 2003

two 1993 kamchatka earthquakes two earthquakes occurred in 1993 off southern kamchatka they have similar surface wave magnitudes focal mechanisms and depths but have distinctly different characteristics the november earthquake is a standard or impulsive m7 underthrusting event the june earthquake is a tsunamigenic or low stress drop event with several unusual characteristics including a large diffuse aftershock zone directivity and a long source time function the 1993 earthquakes ruptured a segment of the kamchatka arc which has not ruptured since 1904 the 1993 earthquakes seem to signal the midpoint in the southern kamchatka seismic cycle

time scale for adjustment of glaciers to changes in mass balance the length of time tm over which a glacier responds to a prior change in climate is investigated with reference to the linearized theory of kinematic waves and to results from numerical models we show the following tm may in general be estimated by a volume time scale describing the time required for a step change in mass balance to supply the volume difference between the initial and final steady states the factor f in the classical estimate of m l u where i is glacier length and u is terminus velocity has a simple geometrical interpretation ft is the ratio of thickness change averaged over the full length i to the change at the terminus although both u and f relate to dynamic processes local to the terminus zone the ratio f u and therefore tm are insensitive to details of the terminus dynamics in contrast to conclusions derived from some simplified kinematic wave models a more robust estimate of tm independent of terminus dynamics is given by tm h b where h is a thickness scale for the glacier and b is the mass balance rate negative at the terminus we suggest that tm for mountain glaciers can be substantially less than the 1o2 103 years commonly considered to be theoretically expected

asperity distribution of the 1952 great kamchatka earthquake and its relation to future earthquake potential in kamchatka the 1952 kamchatka earthquake is among the largest earthquakes of this century with an estimated magnitude of m w 9 0 we inverted tide gauge records from japan north america the aleutians and hawaii for the asperity distribution the results show two areas of high slip the average slip is over 3 m giving a seismic moment estimate of 155 x 102onm or m w 8 8 the 20th century seismicity of the 1952 rupture zone shows a strong correlation to the asperity distribution which suggests that the large earthquakes m 7 are controlled by the locations of the asperities and that future large earthquakes will also recur in the asperity regions

deep structural heterogeneities and the tectonic evolution of the abruzzi region central apennines italy revealed by microseismicity seismic tomography and teleseismic receiver functions abstract the crustal structure of central apennines italy is still poorly defined leaving uncertainties on the tectonic style thin or thick skinned responsible for the development of the thrust and fold belt the today active extension which replaced compression since early quaternary is presumably influenced by the pre existing structure that yields location and segmentation of the fault system to focus on such issues we computed p and s wave velocity models of the crust by using the independent methodologies of local earthquakes tomography and teleseismic receiver function we document strong lateral and vertical heterogeneities that define shallow imbricate sheets of the mesozoic cover that overlay exceptionally high vp and high vs bodies these bodies can be interpreted as either dolomitic or partially hydrated mafic rocks the two alternative interpretations respectively imply an ultra thick deposition of dolomitic rocks in the hanging wall of triassic normal fault or a deep exhumation of the pre mesozoic basement during the early mesozoic sin rift tectonic in both cases these bodies influenced the evolution of the thrust and fold belt very remarkably active normal faults like those ruptured during the still ongoing 2009 l aquila sequence concentrate at the border of these bodies suggesting that they have an active role in the segmentation of the normal fault system the rheological behavior of such high vp high vs bodies weak or strong is still uncertain but of utmost importance to understand the risk of future normal faulting earthquakes

structural setting of a typical alkali potassic volcano roccamonfina southern italy abstract the structural setting of roccamonfina volcano is reconstructed using gravity and magnetotelluric plus time domain electromagnetic data a 887 m deep bore hole drilled within the summit caldera was utilized to constrain the inversion models roccamonfina volcano appears located at the intersection of two east northeast and north trending narrow grabens the location of historical seismic activity indicates that at least one of them the north trending is still active mt tdem apparent resistivity curves show the existence of a ubiquitous conductive layer which includes hydrothermally altered volcanic rocks and flysch formations the average thickness of the volcanic sequence is about 800 1000 m no evidence was found for the presence of the intracrustal magmatic reservoir which is required to justify the chemistry of magmas erupted during the second and final stage of activity of the volcano

crustal structure and moho depth profile crossing the central apennines italy along the n42 parallel 1 we present results from a teleseismic receiver function study of the crustal structure in the central apennines italy data from 15 stations deployed in a linear transect running along the n42 parallel were used for the analysis a total number of 364 receiver functions were analyzed the crustal structure has been investigated using the neighborhood algorithm inversion scheme proposed by sambridge 1999a obtaining crustal thicknesses bulk crustal vp vs ratio and velocity depth models in each inversion the degree of constraint of the different parameters has been appraised by the bayesian inference algorithm by sambridge 1999b the study region is characterized by crustal complexities and intense tectonic activity recent volcanism orogenesis active extensional processes and these complexities are reflected in the receiver functions however the relatively close spacing among the seismometers about 20 km helped us in the reconstruction of the crustal structure and moho geometry along the transect crossing the apennines from west to east the moho depth varies by more than 20 km going from a relatively shallow depth around 20 km on the tyrrhenian side deepening down to about 45 km depth beneath the external front of the apenninic orogen and rising up again to about 30 km depth in correspondence of the adriatic foreland despite the strong variability of the crustal thickness the average crustal vs values show little variation along the transect fluctuating around 3 km s the average vp values obtained from the vs and vp vs are generally lower than 6 km s