field survey of the 1993 hokkaido nansei oki earthquake tsunami runup data in hokkaido and in three prefectures in the tohoku district are described with a few witnessed arrival times and with comments of tide records the highest runup of 31 7 m was found at the bottom of a narrow valley on the west coast of okushiri island in order to explain high runups of 20 m at hamatsumae in the sheltered area roles of edge waves refraction of the okushiri spur and tsunami generation by causes other than the major fault motion should be understood an early arrival of the tsunami on the west coast of hokkaido suggests another tsunami generation mechanism in addition to the major fault motion

field survey report on tsunami disasters caused by the 1993 southwest hokkaido earthquake detailed field work at okushiri island and along the southwest coast of hokkaido has revealed quantitatively 1 the advancing direction of tsunami on land 2 the true tsunami height i e height of tsunami excluding its splashes as measured from the ground and 3 the flow velocity of tsunami on land in heavily damaged areas when a japanese wooden house is swept away by tsunami bolts that tie the house to its concrete foundation resist until the last moment and become bent towards the direction of the house being carried away the orientations of more than 850 of those bent bolts and iron pipes all that can be measured mostly at okushiri island and fell down direction of about 400 trees clearly display how tsunami behaved on land and caused serious damage at various places the true tsunami height was estimated by using several indicators such as broken tree twigs and a window pane the flow velocity of tsunami on land was determined by estimating the hydrodynamic force exerted on a bent handrail and a bent down guardrail by the tsunami through in situ strength tests

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

finite element modeling of the july 12 1993 hokkaido nansei oki tsunami a fault plane model and a finite element hydrodynamic model are applied to the simulation of the hokkaido nansei oki tsunami of july 12 1993 the joint performance of the models is assessed based on the overall ability to reproduce observed tsunami waveforms and to preserve mass and energy during tsunami propagation while a number of observed characteristics of the waveforms are satisfactorily reproduced in particular amplitudes and arrival times at tidal gauges relatively close to the source and general patterns of energy concentration others are only marginally so notably wave periods at the same gauges and wave heights along okushiri differences between observations and simulations are traceable to both the fault plane and the hydrodynamic models nonnegligible losses of energy occur throughout the simulated tsunami propagation these losses seem to be due to a combination of factors including numerical damping and possible deficiencies of the shallow water equations in preserving energy

linear and nonlinear computations of the 1992 nicaragua earthquake tsunami numerical computations of tsunamis are made for the 1992 nicaragua earthquake using different governing equations bottom frictional values and bathymetry data the results are compared with each other as well as with the observations both tide gauge records and runup heights comparison of the observed and computed tsunami waveforms indicates that the use of detailed bathymetry data with a small grid size is more effective than to include nonlinear terms in tsunami computation linear computation overestimates the amplitude for the later phase than the first arrival particularly when the amplitude becomes large the computed amplitudes along the coast from nonlinear computation are much smaller than the observed tsunami runup heights the average ratio or the amplification factor is estimated to be 3 in the present case when the grid size of 1 minute is used the factor however may depend on the grid size for the computation

computer simulations of tsunamis due to sector collapse at stromboli italy abstract stromboli is an island volcano of the aeolian volcanic arc characterised by persistent activity the cone rises about 2500 3000 m from its submarine base with very steep slopes its summit at 924 m above the sea level the subaerial growth of stromboli occurred in the last 100 ka has been marked by repeated episodes of large gravitational collapses especially affecting the nw flank of the island in the last 13 ka the last one occurred less than 5000 years ago forming the deep depression on the nw seaward flank named sciara del fuoco sdf and it produced very likely large water waves this paper envisages a scenario where a huge mass of volcanic material collapses into the sea in the same sector in which the sdf collapse took place in holocenic times and it computes possible tsunami evolutions assuming the present day bathymetry numerical simulations are performed by means of two distinct models one for the mass collapse and one for the tsunami slope failure dynamics are calculated with the aid of a lagrangian model the landslide is subdivided into blocks and the motion of each constituent block is calculated by applying the basic principle of mechanical momentum conservation with block block and block ambient interactions being taken into account water waves are computed by solving a system of shallow water equations including a forcing term dependent on the sliding mass motion the finite element fe technique is employed since it permits the use of non uniform grids which are adequate to account for marine basins with irregular coastlines in addition to the sensitivity analysis concerning the main parameters governing the slide motion two main cases are explored differing in the slide path followed by the mass the resulting tsunami is very large with giant waves as high as several meters tens of meters in the worst cases impinging the coast due to the strong wave refraction induced by bathymetry waves travel around the island affecting even the island coast opposite the source

seismic signals associated with landslides and with a tsunami at stromboli volcano italy in this article we analyze the seismic signals produced by two landslides that occurred at the stromboli volcano on 30 december 2002 recorded by both broadband and short period seismic stations located in the 2 5 22 km distance range from the source for both landslides the characteristics of the low frequency seismograms indicate a complex time history in the release of seismic energy the first landslide occurred over the submerged part of the northwest sector of the volcano and had associated a large amplitude low frequency pulse representative of the abrupt detachment of a large mass lower amplitude phases in the following 3 minutes possibly indicate minor detachment events the highest amplitude low frequency signals are well described by a single force source model the second mass failure episode is also characterized by a complex source and can be interpreted as a multiple event with a less abrupt onset and at least four detachments occurring during 4 5 minutes and producing low frequency signals synthetic seismograms generated by a shallow single force located in the submerged area of sciara del fuoco and directed upslope fit well the first low frequency seismic pulse recorded at stromboli and panarea by three component stations from this simulation we estimated the force exerted by the first mass failure the estimate of the volume through two different procedures gives values in the range of 1 0 1 5 million m3 and about 14 million m3 respectively the landslides which involved both the submarine and the subaerial northwest flank of the volcano produced a tsunami that struck the coast of stromboli island and in a few minutes reached the other islands of the aeolian archipelago three broadband seismic stations installed on land about 100 m from the coastline at panarea island located 20 km southwest of stromboli recorded very long period seismic signals produced by the tsunami waves analysis of these signals gives invaluable information on the spectral content and propagation properties of tsunami waves and on their interaction with the ground at a short distance from the coast synthetic tsunami waves obtained by a landslide source model and taking into account the bathymetry of the sea surrounding stromboli and panarea islands fit the observed phenomena and the experimental data very well manuscript received 19 november 2003

numerical modeling of the great 2004 indian ocean tsunami focus on the mascarene islands on 26 december 2004 the m w 9 2 sumatra earthquake triggered the greatest tsunami ever observed in recent times the unprecedented quality and variety of observations on modern instruments provide opportunities to refine modeling techniques as well as our perception of tsunami hazard in oceanic regions where historical events are not as frequent as in the pacific ocean we present a numerical modeling of the 2004 tsunami on the mascarene islands with refined computations on la reunion island where postevent survey observations and one tide gauge record are available we use two different source models models a and b to account for the observations and we also test an additional source model model c to study the effect of a tsunami originating in the 1833 epicentral area southern sumatra a wave trapped on the edge of la reunion may explain the greatest water heights reached in the western coastline of the island the observed tide gauge data are reasonably well fit models a and b the run up data can also be explained with our models late disturbances observed in la pointe des galets may be explained by a late tsunami reflection from madagascar or by harbor resonances finally we also show that model c 1833 like strikes la reunion more heavily than models a and b

microseisms and its impact on the marine controlled source electromagnetic signal the marine controlled source electromagnetic method mcsem is employed for studying the electrical characteristics and fluid contents of sedimentary reservoirs however the success rate of the method can be improved significantly by finding the sources of electromagnetic noise and addressing the challenge posed by them at larger offsets where the reservoir signal is often weak i have studied the mcsem data and reporting an electromagnetic noise the strength of the noise is observed 1600 times stronger than the seafloor mcsem signal at 0 1 hz moreover the noise and the transmitted mcsem signals are found coherent in interstation recordings these readings suggest the severity of the noise the source investigation presuming the observed noise as an infragravity wave failed to match the response then the role of microseisms is investigated microseism causes oscillation of the seafloor and produces electromagnetic disturbances by the dynamics of water i have used various conditions for a proper discrimination of the noise as microseisms this mechanism is clearly illustrated with the help of a conceptual diagram the role of the directionality is part of the study which is argued for having a significant role in the generation of microseisms in this paper a new algorithm is presented and is used for calculating the coherency the algorithm helps in mapping the coherency value simultaneously in time and frequency domains

three dimensional experiments on landslide generated waves at a sloping coast abstract this paper describes new three dimensional experiments on water waves generated by landslides the landslide is reproduced by a rigid elliptical body sliding along an inclined plane slope of 1 3 1 vertical 3 horizontal the generated water waves are free to propagate both offshore and alongshore since the plan dimensions of the used wave tank are of at least one order of magnitude larger than the width of the landslide which can be considered to be a scale of the wave length the experimental study has been carried out reproducing both subaerial and partially submerged landslides the wave generation process is studied by means of video records of the near field flow and measurement of the landslide movement the properties of the waves propagating along the coast are described on the basis of runup gauges the waves observed during the experiments always present first a crest and then a trough as the first wave propagates away from the generation area the crest tends to become smaller than the trough and the maximum runup along the coast is given by the second or by the third wave an important feature is that the observed runup along the coast firstly grows with the distance from the generation area it reaches a maximum value at about two times the width of the landslide and then decreases an estimate of the celerity at which the waves propagate along the coast is given on the basis of gauge measurements it results that the crests propagate faster than the troughs and the wave period increases

runup of solitary waves on a circular island this is a study of the interactions of solitary waves climbing up a circular island a series of large scale laboratory experiments with waves of different incident height to depth ratios and different crest lengths is described detailed two dimensional run up height measurements and time histories of surface elevations around the island are presented a numerical model based on the two dimensional shallow water wave equations including runup calculations was developed numerical model predictions agreed very well with the laboratory data and the model was used to study wave trapping and the effect of slope under certain conditions enhanced runup and wave trapping on the lee side of the island were observed suggesting a possible explanation for the devastation reported by field surveys in babi island off flores indonesia and in okushiri island japan

radio echo sounding and ice volume estimates of western nordenskiold land glaciers svalbard as part of ongoing work to obtain a reliable estimate of the total ice volume of svalbard glaciers and their potential contribution to sea level rise we present here volume calculations with detailed error estimates for ten glaciers on western nordenskiold land central spitsbergen svalbard the volume estimates are based upon a dense net of gpr retrieved ice thickness data collected over several field campaigns spanning the period 1999 2012 the total area and volume of the ensemble are 116 06 4 53 km 2 and 10 439 0 373 km 3 respectively while the individual areas volumes and average ice thickness lie within 2 6 50 4 km 2 0 08 5 54 km 3 and 29 108 m respectively volume area scaling relationships overestimate the total volume of these glaciers by up to 35 with respect to our calculation on the basis of the pattern of scattering in the radargrams we also analyse the hydrothermal structure of these glaciers nine of the ten are polythermal while only one is entirely cold

finite element numerical simulation of tsunamis generated by earthquakes near a circular island a numerical model for the propagation of tsunamis generated by earthquakes is applied to study the impact of the water waves against the coast of a circular island the hydraulic source is modeled by means of the static deformation of the seafloor produced by an offshore seismic fault the initial sea surface disturbance is assumed to equal the seabed displacement that is computed analytically through the classical dislocation theory of plane faults with uniform slip the wave propagation is described by means of the shallow water approximation of the navier stokes equations and is computed in a radially symmetric domain for which a quasi analytical solution is available the governing equations are solved numerically by means of a finite element fe method making use of the galerkin procedure the mesh consisting of triangular elements of variable size after a preliminary test of the numerical model against the analytical results several simulations are performed by varying the fault location dimension and dip as well as by varying the radial profiles of the basin bathymetry most attention is devoted to studying the amplification of tsunami waves impacting the island coast what is seen is that depending on the source characteristics namely fault length dip strike and distance from the island and on the basin bathymetry high amplifications in the range 1 to 5 are normally obtained not only in the front of the island as is expected but also on the lee side of the island because of positive interference of waves traveling around the island in both directions under particular conditions downwardly concave bathymetry the largest amplifications are found neither on the front side nor on the lee side but at intermediate places along the island coast

source models for the 1993 hokkaido nansei oki earthquake tsunami a source model for the 1993 hokkaido nansei oki tsunami must satisfy certain conditions such conditions are presented in this paper and two methods are used to determine the best source model for this event a trial and error method selects dcrc 17a as the best among 24 different models this model has three fault planes dipping westward to reproduce well the tide gauge records at two locations an inversion analysis is used to modify the dislocation of dcrc 17a

on the relationship between induced polarization and surface conductivity implications for petrophysical interpretation of electrical measurements abstractpetrophysical interpretation of resistivity measurements is often hindered by the dependence of resistivity on the interconnected pore fluids and the interconnected pore surfaces induced polarization ip measurements yield parameters that are only controlled by the interconnected pore surfaces thereby offering the opportunity to constrain interpretation of resistivity measurements using a database composed of 63 sandstone and unconsolidated sediment samples covering nine independent investigations we identified a strong linear relationship between the real part of surface conductivity surf determined from multisalinity w resistivity measurements and the imaginary conductivity measured with ip at a frequency of about 1 hz we found surf l 0 042 with a coefficient of determination r2 of 0 911 and a standard deviation of l of 0 022 we found a similar relation when the normalized chargeability from debye decomposition of the frequency dependence of the ip response is used in

laboratory experiments of tsunami runup on a circular island laboratory experiments of a 7 2 m diameter conical island were conducted to study three dimensional tsunami runup the 62 5 cm tall island had 1 on 4 side slopes and was positioned in the center of a 30 m wide by 25 m long flat bottom basin solitary waves with height to depth ratios ranging from 0 05 to 0 20 and source lengths ranging from 0 30 to 7 14 island diameters were tested in water depths of 32 and 42 cm twenty seven capacitance wave gages were used to measure surface wave elevations at incident and four radial transects on the island slope maximum vertical runup measurements were made at 20 locations around the perimeter of the island using rod and transit a new runup gage was located on the back or lee side of the island to record runup time series

some recent developments in the acquisition and processing of seismic data abstract industry style 3 d surveys are different in the volume of data processing techniques and expected results from academic 3 d surveys industry has developed new acquisition techniques for marine 3 d surveys multi streamer seismic ships vertical cables and dual sensor bottom cables as opposed to 2 d post stack time migration new techniques involving 2 d and 3 d pre stack depth migration are becoming important examples are given migration of wide angle data to obtain subsurface imaging is discussed attribute analyses including the use of wavelets to detect azimuthal anisotropy and lithologic contrasts are described the use of the recent developments in wavelets in seismic analysis is introduced

comment on on the relationship between induced polarization and surface conductivity implications for petrophysical interpretation of electrical measurements a weller l slater and s nordsiek geophysics 78 no 5 d315 d325 weller et al 2013 have recently presented an attempt to connect the surface and quadrature conductivities of porous media using the polaris model developed by revil 2012 this is an important contribution because the development of such a model can be applied in hydrogeophysics and well logging to determine in a more accurate way textural properties including the pore size distribution the porosity and the permeability of sedimentary rocks in the last decade a growing number of researchers have oversold what can be accomplished by resistivity alone neglecting the effect of surface conductivity unfortunately the paper of weller et al 2013 contains inaccurate statements that are discussed below in more detail three points deserve a more careful discussion 1 weller et al 2013 argue that the value of the mobility ratio i e the ratio of the mobility of the counterions in the stern layer by the mobility of the counterions in the diffuse layer is the same for silicates and aluminosilicates at the opposite the polaris model revil 2012 2013a 2013b predicts two distinct values for this ratio one for silicates and one for aluminosilicates 2 the implications that the mobility ratio is not the same for silica sands and clayey materials may imply that the relationship between the surface conductivity and the quadrature conductivity is not universal the polaris model at the opposite of what is claimed by weller et al 2013 predicts the existence of two distinct trends one for silicates and one for aluminosilicates 3 the relationship between surface and quadrature conductivities both in the paper of weller et al 2013 and in the polaris model is also based on another key parameter the fraction of counterions in the stern layer f also known as the partition coefficient in polaris according to weller et al 2013 f should

tsunami trapping near circular islands trapping of long water waves that are induced by submarine earthquakes and that attack circular islands is studied by applying a theoretical model tinti andvannini 1994 that is based on the linear shallow water approximation the solution is computed as the superposition of the eigenmodes of the water basin the tsunami trapping is seen in terms of the capability of the source to excite the trapped eigenmodes of the basin the bottom depth dependence around the island is shown to be quite important in determining the trapping capability of the island a depth profile that is downwardly concave as the distance from the island coasts increases is substantially more efficient in amplifying the incoming waves and in trapping their energy than a profile exhibiting an upward concavity

an introduction to marine controlled source electromagnetic methods for hydrocarbon exploration early development of marine electromagnetic methods dating back about 80 years was driven largely by defense military applications and use for these purposes continues to this day deepwater frequency domain electric dipole dipole controlled source electromagnetic csem methods arose from academic studies of the oceanic lithosphere in the 1980s and although the hydrocarbon exploration industry was aware of this work the shallow water environments being explored at that time were not ideally suited for its use low oil prices and increasingly successful results from 3d seismic methods further discouraged investment in costly alternative geophysical data streams these circumstances changed in the late 1990s when both statoil and exxonmobil began modeling studies and fieldtrials of csem surveying in deep water around 1000 m or deeper specifically for characterizing the resistivity of previously identified drilling targets trials offshore angola in 2000 2002 by both these companies showed that

the slip distribution of the 1992 nicaragua earthquake from tsunami run up data the 2 september 1992 nicaragua tsunami was induced by an ms 7 7 3 earthquake and caused about 170 victims and significant damage to the coastal areas the aim of this work is to infer the slip distribution along the causative seismic fault from the available tsunami run up field data we have subdivided the fault plane into five slip independent subfaults and computed the corresponding numerical green s functions by integrating shallow water equations via a finite element technique the slip distribution on the fault has been determined by applying a least squares procedure to the differences between the observed run up values and the computed maximum water levels along the coast the main result is that the best fit is found for a nonuniform coseismic slip with the highest displacement taking place in the southernmost part of the fault the measure of the improvement is given by the global rms residual of the heterogeneous slip case being circa 25 smaller than that of the uniform case an ancillary outcome of the analysis is the evaluation of the mean amplification factor of the tsunami wave investing the nicaraguan coast that on assuming a rigidity of 1 1010 n m results to be 3 45

csem technology as a value driver for hydrocarbon exploration abstract the use of the controlled source electromagnetic csem method as a risk reduction tool in marine hydrocarbon exploration is gaining increased acceptance in the oil industry this is related to the ability to map resistivity contrasts in the sub surface and thus aid the detection of hydrocarbons which are typically more resistive than surrounding rocks whereas acoustic seismic energy allows for mapping sub surface structures that may contain hydrocarbons electromagnetic em energy can often say something about the fluids contained within the structures numerous successful csem case stories have been published over the past several years however there are also quite a few stories about failure cases although not well documented in the literature such failure cases may reflect the lack of understanding of the csem technology and how csem data can act as a value driver in order to understand this it is necessary to handle uncertainties and decisions associated with the technology these include geological uncertainties noise models survey designs forward modelling parameters inversion migration parameters and pre processing of real data a proper handling of these uncertainties and decisions will aid in defining and constraining the chance of geologic success and geologic success case net present value for prospects prior to drilling wells as such the csem technology has a significant potential to increase exploration efficiency if applied correctly