role of clastic sedimentology in the exploration and production of oil and gas in the north sea summary the nature and quality of clastic reservoir rocks is the result of a complex interplay of tectonic setting provenance depositional environment and diagenesis in particular it is now well established that the reconstruction of depositional environments in clastic successions provides the optimum framework for describing and predicting reservoir development and reservoir quality distribution on both regional exploration and field production scales this review in the context of the 21st anniversary of the british sedimentological research group bsrg expands the above mentioned theme in relation to the development of depositional models of each of the major oil and or gas bearing clastic reservoirs in the u k sector of the north sea which has been the subject of a surge in geological interest following the first gas discoveries approximately 21 years ago each major reservoir interval is used to illustrate specific themes with emphasis placed on how the application of depositional models has contributed to a better understanding of the exploration for and the production from the following reservoirs i permian aeolian and fluvial sands rotliegendes sandstones southern north sea ii jurassic fluvial deltaic and marginal marine sands lower jurassic statfjord formation and middle jurassic brent group northern north sea iii jurassic shallow marine and deeper marine mass flow sands and conglomerates upper jurassic fulmar piper type sands and brae magnus type deposits central and northern north sea and iv tertiary deep marine turbidite fan deposits palaeocene and eocene sands central and northern north sea

a two asperity fault model with wave radiation abstract we study the dynamics of a fault containing two asperities having different strengths and subject to a constant strain rate the fault is modeled by a discrete dynamical system with two degrees of freedom that are the slip deficits of the asperities the radiation of elastic waves during the slipping modes is taken into account by introducing a term proportional to slip rate in the equations of motion we give a complete analytical solution of the four dynamic modes of the system any seismic event can be expressed as a sequence of modes for which the moment rate the spectrum and the total seismic moment can be calculated we consider the energy budget of the event and calculate the seismic efficiency the presence of radiation may remarkably change the evolution of the system from a given state since it moves the boundaries between the different subsets of the sticking region in addition the slip amplitude in a seismic event is smaller while the slip duration is longer in the presence of radiation the shape of the moment rate function depends on the seismic efficiency and the seismic moment decreases with increasing efficiency at constant radiated energy as an application of the model we consider the 1964 great alaska earthquake and calculate the mode durations the slip distribution the moment rate function and the seismic moment of the earthquake obtaining values that are consistent with observations

clyde field growth fault secondary detachment above basement faults in north sea the clyde oil field in the southern north sea comprises a jurassic fulmar sand reservoir developed on a fault bounded terrace on the margin of the central graben palinspastic sections were constructed to honor seismic and well data and were repeatedly tested using new techniques for balancing structural sections in extensional regimes cross sectional area and bed length balance clearly demonstrate the presence of both shallow and deep fault detachments seismic remapping has substantiated this model and demonstrates the decoupling of the basement and shallow listric fault sets the new model has significance in terms of variations in reservoir quality and possible reservoir discontinuities resulting from fault seals of regional interest is the possibility of additio al growth fault plays of this type within the north sea basin

a viscoelastic and afterslip postseismic deformation model for the 1964 alaska earthquake 1 we developed a 3 d viscoelastic model in concert with an afterslip model to describe the postseismic deformation following the 1964 alaska earthquake our model incorporates a realistic geometry including an elastic slab with very low dip angle these geometric factors are important and require a reanalysis of the 1964 coseismic model our coseismic model differs from previous models in that the montague island splay fault extends farther along the kenai peninsula coast and as a result slip on the megathrust in that region is smaller we computed postseismic deformation models using a range of mantle viscosities with maxwell relaxation time of 1 to 50 years with a best estimate of 20 years the viscoelastic model explains most of the trenchward motion observed in the present velocity field but has little impact on cumulative 1965 to present uplifts after removing the viscoelastic response the largest residual cumulative uplifts were located downdip from areas of largest coseismic slip area and we explain them using an afterslip model constrained in space by the observed cumulative postseismic uplifts and in time by tide gauge records no single mechanism can explain both the 30 years of cumulative uplift and the present velocities but a combination of viscoelastic relaxation afterslip interseismic elastic deformation and motion of southern alaska relative to north america explains the first order features of the observations forty years after the earthquake the present day velocities contain a significant component of postseismic deformation so very long lived postseismic deformation plays an important role in the subduction zone earthquake cycle for great earthquakes

influence of asperities along subduction interfaces on the stressing and seismicity of adjacent areas abstract dmowska r and lovison l c 1992 influence of asperities along subduction interfaces on the stressing and seismicity of adjacent areas in t mikumo k aki m ohnaka l j ruff and p k p spudich editors earthquake source physics and earthquake precursors tectonophysics 211 23 43 we have investigated the influence of large scale fault inhomogeneities in large subduction earthquakes on the style of deformation and seismic behavior of the incoming oceanic plate and slab at intermediate depths during the earthquake cycle the zones of the large subduction events of rat islands 1965 alaska 1964 and valparaiso 1985 have been searched for earthquakes with m b 5 0 if available and for time periods as long as possible it has been found that in general the seismicity in the incoming oceanic plate clusters in front of asperities areas of highest seismic moment release and strongest locking and is positioned relative to them in the direction of plate motion it is usually lacking in areas adjacent to non asperities that is to zones that slip during the main event but with appreciably smaller seismic moment release and possibly slip seismically aseismically during the whole cycle similar behavior occurs in the downgoing slab at intermediate depths where seismicity during the cycle clusters but less strongly than in the oceanic crust next to asperities and down dip from them we infer that the locking of asperities causes higher stresses associated with the earthquake cycle itself to occur in areas adjacent to asperities both up dip and down dip from them along the direction of plate motion and that such stressing is much less pronounced in the areas adjacent to non asperities this opens the possibility of identifying the areas of highest seismic moment release in future subduction earthquakes and carries implications for where the highest deformation and possibly precursory phenomena and or nucleation of a future event might occur

asperity distribution of the 1964 great alaska earthquake and its relation to subsequent seismicity in the region abstract the 1964 alaska earthquake was the second largest seismic events in the 20th century the aim of this work is the use of surface deformation data to determine asperity and slip distributions on the fault plane of the alaska earthquake these distributions are calculated by a monte carlo method to this aim we decompose the fault plane in a large number of small square asperity units with a side of 25 km this allows us to obtain plane surfaces with an irregular shape in the first stage each asperity unit is allowed to slip a constant amount or not to slip at all providing the geometry of the dislocation surface that best reproduces the observed displacements to this purpose a large number of slip distributions have been tried by the use of the monte carlo method the slip amplitude is the same for all the asperities and is equal to the average fault slip inferred from the seismic moment in the second stage we evaluate the slip distribution in the dislocation area determined by the monte carlo inversion in this case we allow unit cells to undergo different values of slip in order to refine the initial dislocation model the results confirm the previous finding that the slip distribution of the great alaska earthquake was essentially made of two dislocation areas with a higher slip the prince william sound and the kodiak asperities analysis of the post 1964 seismicity in the rupture region shows a strong correlation between the larger earthquakes mw 6 and the distribution of locked asperities following the 1964 event which can be considered as an independent test of the validity of the model we do not find slip values higher than 25 m for any of the patches and we determine two separate high slip zones one correspondent to the prince william sound asperity and one 18 m slip to the kodiak asperity the slip distribution connected with the 1964 shock appears to be consistent with the following seismicity in the region

long term dynamics of a fault with two asperities of different strengths summary a fault made of two segments or asperities having different strengths and subject to a constant strain rate is considered the fault is modelled by a discrete dynamical system made of two blockscoupledbyaspringandpulledatconstantvelocityonaroughplane wegiveacomplete analytical solution for the evolution of the system the long term behaviour of the fault is studied by calculating the orbits of the system in the phase space the dynamics of the system has four different modes and produces a variety of behaviours the asperities may slip one at a time originating a medium size earthquake or simultaneously originating a large earthquake in the latter case the focus may be at one asperity or at the other in some cases the weaker asperity may slip twice both before and after the failure of the stronger asperity the time pattern of the seismic events generated by the fault is controlled by the stress distribution on the asperities and may include many different behaviours we devise suitable correspondence rules allowing application of the discrete model to real fault systems as an example the model is applied to the 1964 great alaska earthquake which was originated by the failure of two asperities and a possible evolution of this fault system is discussed

stress changes due to recent seismic events in the central apennines italy the central apennines italy are characterized by moderate seismic activity on normal faults oriented in directions parallel to the apenninic chain the subject of this study is the umbria marche apennines a segment approximately 200 km long where three main seismic events occurred in the last three decades the 1979 norcia earthquake was a mw 5 8 event taking place at the south end of the considered segment the 1984 gubbio earthquake was a mw 5 6 event which took place at the north end the 1997 1998 colfiorito sequence constituted 8 main shocks with magnitudes mw between 5 and 6 and epicenters located between the gubbio and the norcia earthquake areas a model made of an elastic half space is considered in which the seismic sources are represented by rectangular dislocations which have the appropriate values of source parameters and in which the static stress field produced by each event is calculated the analysis of the coulomb stress change c as a function of time shows that the coseismic stress transfer and fault interaction played an important role in the region during the past three decades 7 earthquakes of the 9 considered took place where c 0 such an interaction has been confirmed by the analysis of the aftershocks in the colfiorito zone post september 26 1997 about the 61 of the aftershocks considered took place where c 0 the comparison between the cs due to the coseismic stress transfer and the rate t due to the tectonic stress allows us to quantify the time advance of the earthquakes the cs pattern shows positive values in two areas that can be regarded as historical seismic gaps

contemporary deformation and stressing rates in southern alaska summary the subduction of the pacific plate beneath north america induces broad scale stressing of the alaskan crust that has led to the development of the highest mountains in north america the highest slip rates along some of the longest strike slip faults on earth and widespread seismicity that includes the 1964 m9 2 alaska earthquake the second largest ever recorded these features are a consequence of deformation associated with three primary processes interseismic loading due to relative plate motions large earthquakes and postseismic processes how these mechanisms contribute to the evolution of stress in the alaskan crust is not well understood here we use observed contemporary surface velocities to constrain 2 d and 3 d viscoelastic numerical models of relative pacific north american plate motions coseismic slip associated with the 1964 m9 2 megathrust event and strike slip earthquakes on the transform boundary in 1949 m8 1 1958 m7 8 and 1972 m7 6 the four largest events prior to the 2002 m7 9 denali quake viscoelastic relaxation following these events and afterslip to gain insight into how these processes are shaping alaska today results suggest that interseismic deformation and on going post seismic deformation following the 1964 earthquake both contribute significantly to the gps measured contemporary velocity field viscoelastic relaxation associated with a mantle with a viscosity of 10 19 pa s is required to explain southerly directed velocities that are observed in the cook inlet region to well north of the denali fault results also suggest that subduction of the pacific plate leads to a broad zone of deformation with high stressing rates concentrated in a band that lies several hundred kilometres from the plate boundary coeval with the inboard location of the maximum locking depth of the megathrust interseismic deformation and stressing rates remain high further inland across the yakutat microplate where flat subduction extends the width of the locked plate interface calculations show that post seismic relaxation following the large strike slip events serves to reload these rupture surfaces while relieving stress on the eastern denali fault post seismic relaxation following the 1964 earthquake combined with coseismic stress changes promoted the triggering of the 2002 denali quake calculations also suggest that over the past 50 years high stress has accumulated on part of the thrust interface to the west and east of the 1964 rupture surface and along the queen charlotte fault to the south of the 1949 rupture surface

permian and triassic rifting in northwest europe the permo triassic roughly coincided with the life span of pangaea so far as europe is concerned pangaea s creation began in the early carboniferous visean when the northward drifting megacontinent gondwana began to collide with the iberian portion of the slower moving laurussia while proto tethys was subducted beneath the southern margin of central europe creation was complete by the end of the carboniferous or early in the permian with the final development of the variscan orogenic belt which trends from brittany eastward through central europe and with the addition of western siberia along the line of the ural orogen ziegler 1989 despite or perhaps because of its bulk pangaea was not a stable megacontinent no sooner had it formed than it tried to break apart again the disintegration of pangaea had already started before the end of the triassic with the westerly extension of tethys between iberia and africa though not yet underlain by oceanic crust and by early in the jurassic rifting was taking place between africa and the americas in the newly forming central atlantic ocean ziegler 1988 indeed e w extensional movements within a proto atlantic ocean possibly began as early as the late carboniferous haszeldine russell 1987 whilst mid permian extension is well documented in east greenland surlyk et al 1984 these extensional movements may have propagated southward to initiate fracturing in the viking and central grabens of the north sea along which the late permian zechstein sea was to break into the subsiding rotliegend basins and towards the central atlantic where a shallow seaway eventually developed early in the jurassic thus in the northern half of pangaea the continued existence of the former laurussia was already at risk in the permian although crustal separation in the north atlantic which possibly started in the rockall trough in the early cretaceous was finally achieved along the line of the reykjanes ridge only in the paleocene these major events on the periphery of what is now europe separately and jointly were factors that probably controlled a whole sequence of tectonic events within the continent which in turn controlled its patterns of mostly terrestrial sedimentation climatically the northward drift of laurussia had carried nw europe from a region of equatorial rain forest during the later carboniferous to the latitudes of a trade wind desert like the modern sahara in the permian the late permian basins of upper rotliegend and zechstein deposition were arid rotliegend sediments are characterized by dune sand and the saline mudstones of a semipermanent desert lake and the zechstein by shallow water carbonates and anhydrite and deeper water halite during the triassic however brackish water fluvial and lacustrine sediments occupied the basinal areas although even here halite horizons e g rrt muschelkalk and keuper in the north sea area associated with local transgressions from tethys testify that arid conditions were never far away

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

estimation of strong ground motion from the great 1964 mw 9 2 prince william sound alaska earthquake we are generating physically plausible near field synthetic ground motions for the great 1964 prince william sound alaska earthquake compatible with available seismological data tectonic information and eyewitness accounts the first objective of this study is the simulation of the low frequency i e f 0 03 hz strong ground motions on selected locations and on a dense grid of observation points extending over the shallow dipping causative fault of the 1964 alaska earthquake in order to accomplish this task we are utilizing the slip model proposed by johnson et al 1996 based on a joint inversion of tsunami waveforms and geodetic data the calculations are carried out using the discrete wavenumber representation method bouchon and aki 1977 bouchon 1979 and the generalized transmission and reflection coefficient technique luco and apsel 1983 the second objective of this study is the reconstruction of the strong ground motion time histories and response spectra that the city of anchorage experienced during the 1964 alaska earthquake the low frequency i e f 0 03 hz ground motions are generated using the methodology described previously the intermediate frequency i e 0 03 f 0 50 hz ground motions are simulated by convolving green s functions generated by the discrete wavenumber representation method with far field radiation pulses of circular cracks sato and hirasawa 1973 dong and papageorgiou 2002a the high frequency i e 0 5 f 8 0 hz ground motions are simulated using the stochastic modeling approach the three independently derived ground motion components are then properly combined to generate synthetic broadband ground motion time histories and response spectra for the city of anchorage due to the 1964 prince william sound earthquake the third objective of this study is the validation of the synthetic strong ground motions for the 1964 alaska earthquake against observed tectonic deformation ground motion estimates inferred from descriptions of structural damage and eyewitness accounts in summary the analysis presented in this study contributes to a better understanding of the seismological aspects of the 1964 alaska earthquake and provides synthetic time histories and response spectra for engineering applications compatible with all available information i e seismological tectonic and eyewitness accounts it should be noted however that the generated strong ground motions are not necessarily unique nor do they reflect the entire uncertainty that characterizes the problem under investigation

comment on the timing and evolution of the post glacial transgression across the sea of marmara shelf south of istanbul by eris et al marine geology 243 57 76 abstract in their recent paper eris and co authors attempt to refute much of our work on deltaic sediments at the southern exit of the bosphorus strait turkey first their age model is completely inconsistent with the well constrained chronology of our cores mar02 110 and mar02 111 their calypso core md 2750 must have seriously oversampled the holocene section giving an erroneous impression of true thicknesses and ties to seismic data and therefore leading to an incorrect assessment of the timing of deltaic sedimentation second they have ignored evaporative drawdown in the marmara sea from 14 7 11 3 ka lowering of the sea surface by evaporation is a better explanation for a lowstand shoreline at 83 m elevation than their proposal that the dardanelles sill was this deep at the time of reconnection with the global ocean third we contest their conclusion that the uppermost delta in this area was sourced from the kurbagalidere river the sediment flux of this river is too little it cannot account for the strong upward climb of the topset to foreset transition into a rapidly rising ocean and eris et al make no attempt to explain the absence of a precursor shelf edge delta that would be mandatory if this river had the water and sediment discharge that they suggest

inversion of long period p waves from great earthquakes along subduction zones abstract long period p waves from subduction zone earthquakes in the moment range from 7 1027to 8 1029dyn cm are analyzed using an iterative deconvolution method in addition to discrete subevents which effectively contribute to the observed seismograms the long period component of the moment rate function is derived with the constraint that the total seismic moment is equal to the moment determined from long period surface waves it is shown that great earthquakes can be described by several subevents with a duration of about 10 s which changes little from earthquake to earthquake in the above moment range the long period component of the moment rate function becomes larger for a greater earthquake the greatest earthquakes of mw 9 additionally involve subevents with another duration scale much longer than 10 s it is also shown that the local stress drop is 1 order of magnitude larger than the stress drop averaged over the entire fault plane the constancy of the local stress drop as well as the average stress drop holds among various magnitudes of earthquakes these observations suggest an essential similarity in the mode of dislocation distribution

slip on the suckling hills splay fault during the 1964 alaska earthquake abstract the suckling hills in southern alaska experienced localized anomalously large coseismic uplift in the m w 9 2 1964 alaska earthquake large uplift at the suckling hills can be explained by increased slip or an asperity on the alaska aleutian megathrust however this paper suggests that increased uplift may be a result of slip on the suckling hills splay fault we present a series of models that demonstrate how the inclusion of the suckling hills fault improves the fit between modeled vertical displacement and measured coseismic uplift in comparison to slip on the alaska aleutian megathrust alone our results suggest that 3 m of average slip on the suckling hills fault during the 1964 earthquake can help explain the large coseismic uplift data these results are consistent with recent studies indicating pleistocene slip on the suckling hills fault and together highlight the potential seismic and tsunami risk associated with this segment of the alaskan subduction complex

paleoseismic potential of sublacustrine landslide records in a high seismicity setting south central alaska abstract sublacustrine landslide stratigraphy is considered useful for quantitative paleoseismology in low seismicity settings however as the recharging of underwater slopes with sediments is one of the factors that governs the recurrence of slope failures it is not clear if landslide deposits can provide continuous paleoseismic records in settings of frequent strong shaking to test this we selected three lakes in south central alaska that experienced a strong historical megathrust earthquake the 1964 m w 9 2 great alaska earthquake and exhibit high sedimentation rates in their main basins 0 2 cm yr 1 1 0 cm yr 1 we present high resolution reflection seismic data 3 5 khz and radionuclide data from sediment cores in order to investigate factors that control the establishment of a reliable landslide record seismic stratigraphy analysis reveals the presence of several landslide deposits in the lacustrine sedimentary infill most of these landslide deposits can be attributed to specific landslide events as multiple landslide deposits sourced from different lacustrine slopes occur on a single stratigraphic horizon we identify numerous events in the lakes eklutna lake proximal basin 14 events eklutna lake distal basin 8 events skilak lake 7 events and kenai lake 7 events the most recent event in each basin corresponds to the historic 1964 megathrust earthquake all events are characterized by multiple landslide deposits which hints at a regional trigger mechanism such as an earthquake the synchronicity criterion this means that the landslide record in each basin represents a record of past seismic events based on extrapolation of sedimentation rates derived from radionuclide dating we roughly estimate a mean recurrence interval in the eklutna lake proximal basin eklutna lake distal basin skilak lake and kenai lake at 250 yrs 450 yrs 900 yrs and 450 yrs respectively this distinct difference in recording can be explained by variations in preconditioning factors like slope angle slope recharging sedimentation rate and the sediment source area faster slope recharging and a predominance of delta and alluvial fan failures increase the sensitivity and lower the intensity threshold for slope instability also the seismotectonic setting of the lakes has to be taken into account this study demonstrates that sublacustrine landslides in several alaskan lakes can be used as reliable recorders of strong earthquake shaking when a multi lake approach is used and can enhance the temporal and spatial resolution of the paleoseismic record of south central alaska

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

combined effects of tectonic and landslide generated tsunami runup at seward alaska during the mw 9 2 1964 earthquake we apply a recently developed and validated numerical model of tsunami propagation and runup to study the inundation of resurrection bay and the town of seward by the 1964 alaska tsunami seward was hit by both tectonic and landslide generated tsunami waves during the m rm w 9 2 1964 megathrust earthquake the earthquake triggered a series of submarine mass failures around the fjord which resulted in landsliding of part of the coastline into the water along with the loss of the port facilities these submarine mass failures generated local waves in the bay within 5 min of the beginning of strong ground motion recent studies estimate the total volume of underwater slide material that moved in resurrection bay to be about 211 million m3 haeussler et al in submarine mass movements and their consequences pp 269 278 2007 the first tectonic tsunami wave arrived in resurrection bay about 30 min after the main shock and was about the same height as the local landslide generated waves our previous numerical study which focused only on the local landslide generated waves in resurrection bay demonstrated that they were produced by a number of different slope failures and estimated relative contributions of different submarine slide complexes into tsunami amplitudes suleimani et al in pure appl geophys 166 131 152 2009 this work extends the previous study by calculating tsunami inundation in resurrection bay caused by the combined impact of landslide generated waves and the tectonic tsunami and comparing the composite inundation area with observations to simulate landslide tsunami runup in seward we use a viscous slide model of jiang and leblond j phys oceanogr 24 3 559 572 1994 coupled with nonlinear shallow water equations the input data set includes a high resolution multibeam bathymetry and lidar topography grid of resurrection bay and an initial thickness of slide material based on pre and post earthquake bathymetry difference maps for simulation of tectonic tsunami runup we derive the 1964 coseismic deformations from detailed slip distribution in the rupture area and use them as an initial condition for propagation of the tectonic tsunami the numerical model employs nonlinear shallow water equations formulated for depth averaged water fluxes and calculates a temporal position of the shoreline using a free surface moving boundary algorithm we find that the calculated tsunami runup in seward caused first by local submarine landslide generated waves and later by a tectonic tsunami is in good agreement with observations of the inundation zone the analysis of inundation caused by two different tsunami sources improves our understanding of their relative contributions and supports tsunami risk mitigation in south central alaska the record of the 1964 earthquake tsunami and submarine landslides combined with the high resolution topography and bathymetry of resurrection bay make it an ideal location for studying tectonic tsunamis in coastal regions susceptible to underwater landslides

coseismic slip in the 1964 prince william sound earthquake a new geodetic inversion the 1964 prince william sound earthquake march 28 1964 m w 9 2 caused crustal deformation over an area of approximately 140 000 km 2 in south central alaska in this study geodetic and geologic measurements of this surface deformation were inverted for the slip distribution on the 1964 rupture surface previous seismologic geologic and geodetic studies of this region were used to constrain the geometry of the fault surface in the kodiak island region 28 rectangular planes 50 by 50 km each oriented 218 with a dip varying from 8 nearest the aleutian trench to 9 below kodiak island define the rupture surface in the prince william sound region 39 planes with variable dimensions 40 by 50 km near the trench 64 by 50 km inland and orientation 218 in the west and 270 in the east were used to approximate the complex faulting prior information was introduced to constrain offshore dip slip values the strike slip component and slip variation between adjacent planes our results suggest a variable dip slip component with local slip maximums occurring near montague island up to 30 m further to the east near kayak island up to 14 m and trenchward of the northeast segment of kodiak island up to 17 m a single fault plane dipping 30 corresponding to the patton bay fault with a slip value of 8 m modeled the localized but large uplift on montague island the moment calculated on the basis of our geodetically derived slip model of 5 0 1029 dyne cm is 30 less than the seismic moment of 7 5 x 1029 dyne cm calculated from long pe riod surface waves kanamori 1970 but is close to the seismic moment of 5 9 1029 dyne cm obtained by kikuchi and fukao 1987

note on the 1964 alaska tsunami generation by horizontal displacements of ocean bottom numerical modeling of the runup in chenega cove alaska a numerical model of the wave dynamics in chenega cove alaska during the historic m w 9 2 megathrust earthquake is presented during the earthquake locally generated waves of unknown origin were identified at the village of chenega located in the western part of prince william sound the waves appeared shortly after the shaking began and swept away most of the buildings while the shaking continued we model the tectonic tsunami in chenega cove assuming different tsunami generation processes modeled results are compared with eyewitness reports and an observed runup results of the numerical experiments let us claim the importance of including both vertical and horizontal displacement into the 1964 tsunami generation process we also present an explanation for the fact that arrivals of later waves in chenega were unnoticed

near field modeling of the 1964 alaska tsunami the role of splay faults and horizontal displacements near field observations of tsunami waves generated by the mw9 2 1964 alaska earthquake reveal a complex relationship between coseismic slip and the tsunami wavefield in the source area the documen

monte carlo inversion of dinsar data for dislocation modeling application to the 1997 umbria marche seismic sequence central italy the study of surface deformation due to seismic activity is often made using dislocations with uniform slip and simple geometries a better modeling of coseismic and postseismic surface displacements can be obtained by using dislocations with variable slip and nonregular shapes this is consistent with the asperity model of fault surfaces assuming a friction distribution on faults made of locked zones with much higher friction than surrounding zones in this paper we consider the 1997 1998 colfiorito seismic sequence the coseismic surface displacements in the colfiorito zone are used in order to infer the slip distribution on the fault surface at different stages of the sequence the displacement field has been modeled varying the slip distribution on the fault and comparing the deformation observed by sar and gps techniques with model results the slip distribution is calculated by monte carlo simulations on a normal fault with the dip angle equal to 40 a good approximation is obtained by using square asperity units of 1 5 1 5 km2 in the first stage we employed a simplified model with uniform slip in which each asperity unit is allowed to slip a constant amount or not to slip at all and in the second stage we evaluate the slip distribution in the dislocation area determined by the monte carlo inversion in this case we allow unit cells to undergo different values of slip in order to refine the initial dislocation model the results show that the 1997 seismic events of the sequence can be modeled by irregular dislocations obtaining a good fit to the dinsar and gps observations the model also confirms the results of previous studies by a different methodology defining the distribution of asperities on the fault plane using the fault geometry the geodetic data and the seismic moment of the 1997 1998 colfiorito seismic sequence furthermore the analysis of 1997 aftershocks in the seismogenic region shows a strong correlation between most events and the asperity distribution which can be considered as an independent test of the validity of the model