environmental perturbations caused by the impacts of asteroids and comets we review the major impact associated mechanisms proposed to cause extinctions at the cretaceous tertiary geological boundary we then discuss how the proposed extinction mechanisms may relate to the environmental consequences of asteroid and comet impacts in general our chief goal is to provide relatively simple prescriptions for evaluating the importance of impacting objects over a range of energies and compositions but we also stress that there are many uncertainties we conclude that impacts with energies less than about 10 mt are a negligible hazard for impacts with energies above 10 mt and below about 104 mt i e impact frequencies less than one in 6 104 years corresponding to comets and asteroids with diameters smaller than about 400 m and 650 m respectively blast damage earthquakes and fires should be important on a scale of 104 or 105 km which corresponds to the area damaged in many natural disasters of recent history however tsunami excited by marine impacts could be more damaging flooding a kilometer of coastal plain over entire ocean basins in the energy range of 104 105 mt intervals up to 3 105 years corresponding to comets and asteroids with diameters up to 850 m and 1 4 km respectively water vapor injections and ozone loss become significant on the global scale in our nominal model such an impact does not inject enough submicrometer dust into the stratosphere to produce major adverse effects but if a higher fraction of pulverized rock than we think likely reaches the stratosphere stratospheric dust causing global cooling would also be important in this energy range thus 105 mt is a lower limit where damage might occur beyond the experience of human history the energy range from 105 to 106 mt intervals up to 2 106 years corresponding to comets and asteroids up to 1 8 and 3 km diameter is transitional between regional and global effects stratospheric dust sulfates released from within impacting asteroids and soot from extensive wild fires sparked by thermal radiation from the impact can produce climatologically significant global optical depths of the order of 10 moreover the ejecta plumes of these impacts may produce enough no from shock heated air to destroy the ozone shield between 106 and 107 mt intervals up to 1 5 107 years corresponding to comets and asteroids up to 4 and 6 5 km diameter dust and sulfate levels would be high enough to reduce light levels below those necessary for photosynthesis ballistic ejecta reentering the atmosphere as shooting stars would set fires over regions exceeding 107 km and the resulting smoke would reduce light levels even further at energies above 107 mt blast and earthquake damage reach the regional scale 106 km tsunami cresting to 100 m and flooding 20 km inland could sweep the coastal zones of one of the world s ocean basins fires would be set globally light levels may drop so low from the smoke dust and sulfate as to make vision impossible at energies approaching 109 mt 108 years the ocean surface waters may be acidified globally by sulfur from the interiors of comets and asteroids the cretaceous tertiary impact in particular struck evaporate substrates that very likely generated a dense widespread sulfate aerosol layer with consequent climatic effects the combination of all of these physical effects would surely represent a devastating stress on the global biosphere

frequency domain response at pacific coast harbors to major tsunamis of 2005 2011 tsunamis waves caused by submarine earthquake or landslide might contain large wave energy which could cause significant human loss and property damage locally as well as in distant region the response of three harbors located at the pacific coast i e crescent city harbor los angeles long beach port and san diego harbor to six well known tsunamis events generated both near field and far field between 2005 and 2011 are examined and simulated using a hybrid finite element numerical model in frequency domain the model incorporated the effects of wave refraction wave diffraction partial wave reflection from boundaries entrance and bottom energy dissipation it can be applied to harbor regions with arbitrary shapes and variable water depth the computed resonant periods or modes of oscillation for three harbors are in good agreement with the energy spectral analysis of the time series of water surface elevations recorded at tide gauge stations inside three harbors during the six tsunamis events the computed wave induced currents based on the present model are also in qualitative agreement with some of the reported eye witness accounts absence of reliable current data the simulated results show that each harbor responded differently and significantly amplified certain wave period s of incident wave trains according to the shape topography characteristic dimensions and water depth of the harbor basins

some tsunami characteristics deducible from tide records abstract after an initial 40 hour diffusion period the time decay of tsunami variance was found to be uniformly exponents for 28 events among eight pacific tide stations thew results essentially confirm munk s acoustic deny hypothesis except that the decay e folding time 22 h more nearly equated the ocean s normal mode transit time 21 h than munk s mean collision time 14 h relative tsunami energy obtained by extrapolating exponential decay back to t 0 was found to be similarly ranked among tsunamis at all stations and roughly proportional to seismic energy a total energy estimate for the tsunami of 9 march 1957 obtained by correcting the observed energy decay at wake island for instrument and island response provided normalized total energy estimates for all tsunamis that were consistent with independent estimates by kajiura and by aida similarities between power spectra computed from these time series suggests that station response is primarily linear normal mode forcing of the conti

relationship between maximum tsunami amplitude and duration of signal all available tsunami observations at tide gauges situated along the north american coast were examined to determine if there is any clear relationship between maximum amplitude and signal duration in total 89 historical tsunami recordings generated by 13 major earthquakes between 1952 and 2011 were investigated tidal variations were filtered out of the signal and the duration between the arrival time and the time at which the signals drops and stays below 0 3 m amplitude was computed the processed tsunami time series were evaluated and a linear least squares fit with a 95 confidence interval was examined to compare tsunami durations with maximum tsunami amplitude in the study region the confidence interval is roughly 20 h over the range of maximum tsunami amplitudes in which we are interested this relatively large confidence interval likely results from variations in local resonance effects late arriving reflections and other effects

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

stratigraphy and sedimentology of the middle ordovician hawaz formation murzuq basin libya the middle ordovician hawaz formation is a 200 m 660 ft thick succession made up of fine grained quartzarenites displaying a variable degree of bioturbation it records the deposition in a large scale low gradient estuary which was partially controlled by tectonic extension the upper boundary of the formation is marked by two erosion surfaces unconformities u1 and u2 related to the late ordovician glaciation the u1 and u2 erosion surfaces generated a pronounced paleotopography that controlled the deposition of the upper ordovician sequences tectonism influenced the paleogeography although faults were unimportant from the point of view of sedimentary thickness tectonic subsidence was moderate and accumulation rates were low physiography favored tidal power especially during transgressive episodes when the coastal embayment was flooded we defined 11 lithofacies forming 6 facies associations these associations are subtidal sandstones storm reworked shoreface sandstones shoreface to beach sandstones channel sandstone bodies nearshore to inner platform sandstones and k bentonites trace fossil assemblages match skolithos and cruziana archetypal ichnofacies on the basis of the dominant facies associations and ichnofacies we divided the formation into three informal units from base to top hw 1 hw 2 and hw 3 periodically volcanic ash was supplied to the basin from distal eruptive centers and was preserved as thin beds of k bentonite interstratified with the shoreface sandstones but not with the tidal dominated sandstones we divided the hawaz formation into five third order depositional sequences lowstand deposits were not identified the lower boundaries of transgressive systems tracts are tidal ravinement surfaces or sequence boundaries whereas the upper boundaries are flooding surfaces the transgressive systems tracts are constituted by early transgressive tidal deposits separated by a wave ravinement surface from the late transgressive storm dominated deposits highstand systems tracts consist of bioturbated shoreface to beach sandstones which record seaward shoreline progradation emilio obtained his ph d in geology from the universitat de barcelona in 1988 since then he has been a lecturer in basin analysis and petroleum geology he has been involved in several research projects on sedimentology and basin analysis in spain northern africa antarctica and south america his present day research interests include three dimensional modeling of sedimentary bodies and reservoirs a professor of stratigraphy at the universitat de barcelona m marzo s research interest focuses on the application of clastic sedimentology sequence stratigraphy reservoir modeling and basin analysis to the exploration and production of hydrocarbons he has been involved in several research projects funded by oil companies in southern europe the north sea south america and northern africa jordi m de gibert received his ph d from the universitat de barcelona in 1996 after a period at the university of utah he returned to barcelona in 1999 where he currently holds a position as a tenure track lecturer his interests and areas of expertise include trace fossils their paleobiological significance and their implications for understanding ancient depositional environments k tawengi received a b sc degree in geology from alfateh university libya in 1984 and an m sc degree in sedimentology and stratigraphy from durham university england in 1996 he worked as an explorationist with agip oil company in libya from 1985 to 2000 and since then has worked as a senior exploration member with repsol exploration in murzuq s a his main fields of interest are sedimentology stratigraphy and subsurface geology a khoja graduated in 1972 from the university of libya he received a diploma in petroleum geosciences from oxford polytechnic 1991 and an m sc degree from oxford brookes university 1993 he joined the national oil corporation of libya in 1972 and is presently the regional studies superintendent in the national oil exploration department nestor obtained his degree in geology from cordoba university argentina in 1982 and his postgraduate in petroleum geology in the university of cuyo argentina he joined ypf in 1984 and worked in their exploratory department in mendoza plaza huincul and neuquen until the year 2000 subsequently he became libya team leader for repsol ypf in madrid he is currently director of exploration and production in brazil

tide gauge observations of the indian ocean tsunami december 26 2004 the magnitude 9 0 earthquake centered off the west coast of northern sumatra 3 307 n 95 947 e on december 26 2004 at 00 59 utc united states geological survey usgs 2005 usgs earthquake hazards program latest earthquakes earthquake hazards program http earthquake usgs gov eqinthenews 2004 usslav 2005 generated a series of tsunami waves that devastated coastal areas throughout the indian ocean tide gauges operated on behalf of national and international organizations recorded the wave form at a number of island and continental locations this report summarizes the tide gauge observations of the tsunami in the indian ocean available as of january 2005 and provides a recommendation for the use of the basin wide tide gauge network for future warnings

seismicity induced by gas production ii lithology correlated events induced stresses and deformation a 3d relocation technique permits precise locations of induced earthquakes geostatistical processing using the data of 87 boreholes provides the basis of a precise 3d structure with a dome geometry conventional laboratory mechanical tests performed on deep rock samples 1000 m to 5000 m define the rock properties at depths similar to those of the seismic events 1 ml 4 2 that range from 1 to 7 km

microearthquakes near the sleepy hollow oil field southwestern nebraska between april 1982 and june 1984 311 earthquakes were detected and 176 earthquakes were located in the vicinity of the sleepy hollow oil field southwestern nebraska the oil field is being injected with water to enhance oil production and the earthquakes may be related to production there is geologic evidence however to suggest that the earthquakes are tectonic in origin and are related to uplift along the axis of the cambridge arch on which the field is located first motion data from these events do not yield a well constrained fault plane solution furthermore first motion detections are inconsistent for earthquakes with nearly coincident hypocenters indicating that more than one faulting mechanism is active in the oil field injection pressures do not correlate well with earthquake occurrence

triggered earthquakes and deep well activities earthquakes can be triggered by any significant perturbation of the hydrologic regime in areas where potentially active faults are already close to failure the increased pore pressure resulting from fluid injection or alternatively the massive extraction of fluid or gas can induce sufficient stress and or strain changes that with time can lead to sudden catastrophic failure in a major earthquake injection induced earthquakes typically result from the reduction in frictional strength along preexisting nearby faults caused by the increased formation fluid pressure earthquakes associated with production appear to respond to more complex mechanisms of subsidence crustal unloading and poroelastic changes in response to applied strains induced by the massive withdrawal of subsurface material as each of these different types of triggered events can occur up to several years after well activities have begun or even several years after all well activities have stopped this suggests that the actual triggering process may be a very complex combination of effects particularly if both fluid extraction and injection have taken place locally to date more than thirty cases of earthquakes triggered by well activities can be documented throughout the united states and canada based on these case histories it is evident that owing to preexisting stress conditions in the upper crust certain areas tend to have higher probabilities of exhibiting such induced seismicity

free oscillation of the japan sea excited by earthquakes ii modal approach and synthetic tsunamis summary the free oscillations of the japan sea excited by the 1964 niigata and the 1983 japan sea earthquakes are examined adopting a modal approach normal mode solutions with periods longer than 50 min are obtained numerically for the actual bathymetry provided by the grids of 20km in size the eigenvectors or water height distributions obtained show that the modes with longest eigenperiods are determined by the size and depth of the whole japan sea many modes with shorter eigenperiods are regionally trapped in a shallow part such as the continental shelf where the amplitude of eigenvectors is large the niigata earthquake excites mainly the regional modes whereas the japan sea event excites both kinds of modes equally the difference in excitation is attributed to the different water depth at the source the niigata earthquake occurred on a continental shelf about 100 m deep whereas the depth at the source area of the japan sea event is about 2500 m the synthetic tsunami is computed by a superposition of the normal modes the spectra agree well with those observed in the period range of 50 to 210 min

darts and cork in cascadia basin high resolution observations of the 2004 sumatra tsunami in the northeast pacific 1 we report unique deep sea recordings of the sumatra tsunami of december 2004 by high resolution dart deep ocean assessment and reporting of tsunami and cork circulation obviation retrofit kit bottom pressure sensors deployed at depths of 1500 3500 m in cascadia basin in the northeast pacific the simultaneous records from these sites establish the first ever regional scale tsunami detection array for the open ocean enabling us to resolve both seafloor and crustal tsunami signals and to determine fundamental properties of the waves following their 22 000 km journey from the source region waves reaching the basin had mean amplitudes of 5 mm with energy spread over a broad frequency band from 0 4 to 7 cph peak tsunami energy was in the 0 8 to 2 cph 75 to 30 min band leading waves from the event arrived 34 35 h after the earthquake roughly 7 h later than expected suggesting that the tsunami mainly propagated by the most economic minimum energy loss path along mid ocean ridge wave guides rather than taking the direct and fastest path across the ocean motions within the peak energy band comprise roughly 50 coherent progressive waves propagating from the south at longwave phase speeds of 150 ms 1 and 50 random waves scattered from the coast and bottom irregularities tsunami amplitudes in the borehole were one third those on the seafloor the extensive ringing and anomalously slow 3 5 day e folding decay time of the tsunami wave energy indicates long duration energy flux radiating from the indian ocean via the southern pacific ocean

the possible role of fluids for the structuring of the continental crust abstract some well known seismic reflectivity patterns of continental crusts characterize specific tectonic terranes the role of fluids in enhancing or destroying such structures is studied seismicity is strongly dependent on the different pore pressure of fluids in intraplate settings in strike slip or extensional areas hydrostatic pore pressure seems to be approached in accordance with standard rheological models and standard seismicity depth distributions in suture zones or zones of developing loads possibly also along zones of near horizontal normal faults extremely high pore pressure develops which approaches lithostatic values they are accompanied by a number of weakening processes with enhanced shear and reduced viscosity these values correlate with low seismic velocities v p in accordance with an empirical v p relationship

seismic signals from tsunamis in the pacific ocean 1 we examine seismic signals from tsunamis for 14 earthquakes of mw 7 1 to 8 4 in the circum pacific region that generated tsunamis measured previously from tide gauges or coastal runup low frequency signals of 0 5 mhz up to 2 8 mhz are observed at the expected tsunami arrival time on the horizontal components of low elevation seismic stations near coastlines for eight of the 14 earthquakes lower amplitude signals are observed for the other six for two earthquakes mw 8 2 8 4 we observe a dispersed tsunami signal between 1 and 8 mhz with lower frequencies arriving earlier this dispersion is consistent with predictions from the standard model for gravity waves for the bathymetry along these source station paths these observations along with earlier observations from the indian ocean suggest that seismic data could be used to complement tide gauges and ocean bottom pressure recorders to indicate the arrival of a tsunami

investigation of microearthquakes macroseismic data and liquefaction associated with the 1867 wamego earthquake in eastern kansas historical felt earthquakes and instrumentally recorded microseismicity in eastern kansas and western missouri have been attributed to the movement of the nemaha ridge and humboldt fault zone nrhf our investigations of the nrhf have concentrated on relocation of microearthquakes in the kansas catalog re evaluation of the 1867 earthquake felt reports and field studies to determine the presence or absence of sedimentary evidence of earthquake induced liquefaction microearthquakes in the kansas catalog have been relocated in a joint inversion with 3d seismic velocity variations this improved set of hypocenters affirms the loose association of seismicity with the basement nrhf structure even though seismicity does not seem to follow a single well defined fault feature overall the association of microearthquakes with the nrhf suggests that it remains a potential source of large earthquakes our field investigations confirm that sedimentary deposits with moderate liquefaction susceptibility are present in the vicinity of wamego and wabaunsee kansas soft sediment deformation features including flame and dish structures are present in the late holocene floodplain deposits of the kansas river these features may have formed by liquefaction or by processes unrelated to seismic activity such as sediment dewatering we found several clastic dikes that may be attributed to seismically induced liquefaction our initial results suggest that liquefaction features are present but may not be pervasive in this region these data imply that the 5 2 magnitude of the 1867 wamego earthquake may characterize the seismic source in this location however additional field investigations are still necessary to complete the assessment for liquefaction features

tsunami forecast analysis for the may 2006 tonga tsunami 1 this study applies tsunami forecast models developed for noaa s tsunami warning and forecast system to investigate the may 2006 tonga tsunami inversion of the deep ocean assessment and reporting of tsunamis dart measurements estimates a tsunami magnitude equivalent to an earthquake moment magnitude of 8 0 the dart constrained modeling forecasts show good agreement with observations at eight coastal tide stations in hawaii u s west coast and alaska including first arrival times wave periods wave amplitudes and decay during the day following the earthquake the forecast system correctly reproduces the reflected waves from north america and the scattered waves by the bottom topography in the south pacific which arrived in the hawaiian islands 16 and 18 5 h after the earthquake respectively wavelet analysis of the tsunami waves suggests that harbor and local shelf resonances may be predominantly responsible for the late occurrence of the maximum wave observed in some coastal areas these results suggest expanding the operational use of the real time forecast models and demonstrate the applicability of the forecast results for all clear evaluations search and rescue operations as well as event and postevent planning this research highlights the value of high resolution inundation models in real time forecasts during a long duration hazard for coastal communities it also provides a rigorous and successful test of the performance and accuracy of the forecast models when run in real time mode

seismicity induced by gas production i correlation of focal mechanisms and dome structure from august 1976 to june 1979 more than 220 seismic events were recorded by a 7 station network operating over an active gas field in france 120 earthquakes with magnitudes greater than 1 0 were selected for a detailed study in order to understand the seismic response to a decrease in the gas reservoir pressure of 50 mpa composite focal mechanisms were determined for these events we found that where preexisting fractures were known from well logs faults with the most favorable orientation were reactivated in the part of the gas field where no preexisting faults were known orientation of the fracture planes was close to the orientations of stratigraphic interfaces our kinematic model constrained by the distribution of the earthquakes and their focal mechanisms consists of the downward dropping of a block located close to the top of the gas field the main faults as defined by the spatial density of the seismic activity define the limits of this block the displacements observed along these faults can be either normal or reverse mechanism dependent on the preexisting orientation of each fault another important result is the evidence that the depletion of the gas reservoir exerts the major influence on local seismic displacements obscuring the effect of regional setting

japan s 2011 tsunami characteristics of wave propagation from observations and numerical modelling we use a numerical tsunami model to describe wave energy decay and transformation in the pacific ocean during the 2011 tohoku tsunami the numerical model was initialised with the results from a seismological finite fault model and validated using deep ocean bottom pressure records from darts from the neptune canada cabled observatory as well as data from four satellite altimetry passes we used statistical analysis of the available observations collected during the japan 2011 tsunami and of the corresponding numerical model to demonstrate that the temporal evolution of tsunami wave energy in the pacific ocean leads to the wave energy equipartition law similar equipartition laws are well known for wave multi scattering processes in seismology electromagnetism and acoustics we also show that the long term near equilibrium state is governed by this law after the passage of the tsunami front the tsunami wave energy density tends to be inversely proportional to the water depth this fact leads to a definition of tsunami wave intensity that is simply energy density times the depth this wave intensity fills the pacific ocean basin uniformly except for the areas of energy sinks in the southern ocean and bering sea

spectral analysis of tsunami waves separation of source and topography effects a new approach is proposed to separate the influence of source and topography in observed tsunami spectra and to reconstruct the initial source spectrum the method assumes a linear tide gauge response to external forcing and is based on comparative analysis of tsunami and background spectra evaluation of the ratio of tsunami to background spectra gives functional characteristics that are invariant of station location and dependent only on the source parameters three events the urup tsunami of december 22 1991 northwest pacific the hokkaido southwest okushiri tsunami of july 12 1993 sea of japan and the shikotan tsunami of october 4 1994 northwest pacific are used as examples of the proposed approach the source spectra reconstructed from the analysis of different tide gauges were found to be in good agreement with each other and with the seismological geodetic and field survey data

energy decay of the 2004 sumatra tsunami in the world ocean the catastrophic indian ocean tsunami generated off the coast of sumatra on 26 december 2004 was recorded by a large number of tide gauges throughout the world ocean this study uses gauge records from 173 sites to examine the characteristics and energy decay of the tsunami waves from this event in the indian atlantic and pacific oceans findings reveal that the decay e folding time of the tsunami wave energy within a given oceanic basin is not uniform as previously reported but depends on the absorption characteristics of the shelf adjacent to the coastal observation site and the time for the waves to reach the site from the source region in general the decay times for island and open ocean bottom stations are found to be shorter than for coastal mainland stations decay times for the 2004 sumatra tsunami ranged from about 13 h for islands in the indian ocean to 40 45 h for mainland stations in the north pacific

the mad sea phenomenon in the strait of sicily sea level observations at cape bon tunisia and mazara del vallo sicily show that large coherent oscillations exist across the strait of sicily with significant energy bands centered at periods of 35 3 41 6 50 6 75 8 and 134 5 min whose possible structure is confirmed by a numerical approximation to the gravitational barotropic normal modes with realistic topography it is observed that these oscillations are related to the passage of synoptic weather systems over the region an investigation on the configuration phase velocity and direction of approach of atmospheric disturbances over the region suggests that the oscillations in the strait of sicily could be forced by instabilities that develop in large scale low pressure fronts that propagate as pressure gravity waves with an approximate phase speed between 24 and 30 m s21

forecasting wave amplitudes after the arrival of a tsunami the destructive pacific ocean tsunami generated off the east coast of honshu japan on 11 march 2011 prompted the west coast and alaska tsunami warning center wcatwc to issue a tsunami warning and advisory for the coastal regions of alaska british columbia washington oregon and california estimating the length of time the warning or advisory would remain in effect proved difficult to address this problem the wcatwc developed a technique to estimate the amplitude decay of a tsunami recorded at tide stations within the warning center s area of responsibly aor at many sites along the west coast of north america the tsunami wave amplitudes will decay exponentially following the arrival of the maximum wave mofjeldet al nat hazards 22 71 89 2000 to estimate the time it will take before wave amplitudes drop to safe levels the real time tide gauge data are filtered to remove the effects of tidal variations the analytic envelope is computed and a 2 h sequence of amplitude values following the tsunami peak is used to obtain a least squares fit to an exponential function this yields a decay curve which is then combined with an average west coast decay function to provide an initial tsunami amplitude duration forecast this information may then be provided to emergency managers to assist with response planning

observations of the 2004 and 2006 indian ocean tsunamis from a pressure gauge array in indonesia 1 five shallow pressure gauges located in straits in the southern indonesian islands were used to evaluate tsunami signals triggered by the earthquakes off the northwest coast of sumatra in december 2004 and the south coast of java in july 2006 tsunami waves reached the pressure gauges around 5 to 6 hours after the 2004 earthquake the largest waves arrived 10 to 23 hours later with amplitudes ranging from 9 to 25 cm after the 2006 earthquake tsunami arrivals were only evident at the ashmore and roti pressure gauges in timor passage at these two gauges the first waves arrived around 2 25 hours after the earthquake and the largest waves arrived 2 to 3 hours later with amplitudes of 6 and 18 cm spectral analysis shows an increase of energy in the 40 to 80 min period band during the 2004 tsunami and at periods of 10 to 20 min in 2006 a simple ray tracing model of both the 2004 and 2006 events which approximates the tsunami as a shallow water wave was used to evaluate the effect of topography on tsunami propagation in order to provide a physical explanation for the features observed in the pressure gauge data

sedimentology of an ordovician fan delta complex western libya abstract the ordovician haouaz formation in the western central gargaf arch of western libya provides a well exposed example of an ancient fan delta system the haouaz sequence consists of delta front deposits overlain by subaqueous distributary channels with intervening distributary mouth shoals and swash bars this delta front complex is abruptly and erosively overlain by braided fluvial and distributary channels of the lower deltaic plain lower deltaic plain deposits may show reworking by wave swash processes in the upper portion indicating marine destructive phases of delta building this process is attributed to diminished or absent detrital influx allowing wave reworking of the deltaic plain margin these reworked deposits may in turn be overlain by thin transgressive marine shelf sequences also formed during periods of minimal detrital influx the lower deltaic plain may also pass upward into an upper deltaic plain and alluvial plain environment

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

tsunami scattering provinces in the pacific ocean we use a scattering index to identify the regions in the pacific ocean where topographic features scatter significant tsunami energy based on linear wave theory the index is computed from the smith sandwell topography consistent with numerical simulations it shows that there is a narrow band of strong scatterers running across the ocean from the northwest emperor seamount chain to the southeast easter island fracture zone the eastern pacific is nearly devoid of scatterers except for this band and isolated features along the eastern margin to the west of the band lies a region with moderate scattering the strongest scattering occurs in the southwestern pacific the pacific is rimmed by island arcs and shallow continental shelves that also trap and scatter tsunamis these results show that numerical models of trans pacific tsunamis must resolve the effects of the small scale topography in order to accurately simulate their wave patterns and amplitudes

land water boundary treatment for a tsunami model with dimensional splitting the method of splitting tsunamis most model adapted by national oceanic and atmospheric administration noaa for tsunami forecasting operations is praised for its computational efficiency associated with the use of splitting technique it will be shown however that splitting the computations between x and y directions results in specific sensitivity to the treatment of land water boundary slight modification to the reflective boundary condition in most caused an appreciable difference in the results this is demonstrated with simulations of the tohoku 2011 tsunami from the source earthquake to monterey bay california and in southeast alaska followed by comparison with tide gage records in the first case the better representation of later waves reflected from the coasts by the modified model in a pacific wide simulation resulted in twice as long match between simulated and observed tsunami time histories at monterey gage in the second case the modified model was able to propagate the tsunami wave and approach gage records at locations within narrow channels juneau ketchikan to where most had difficulty propagating the wave the modification was extended to include inundation computation the resulting inundation algorithm cliffs has been tested with the complete set of noaa recommended benchmark problems focused on inundation the solutions are compared to the most solutions obtained with the version of the most model benchmarked for the national tsunami hazard mitigation program in 2011 in two tests cliffs and most results are very close and in another two tests the results are somewhat different very different regimes of generation disposal of water by cliffs and most inundation algorithms which supposedly affected the benchmarking results have been discussed

the open ocean energy decay of three recent trans pacific tsunamis 1 the 2009 samoa mw 8 1 2010 chile 8 8 and 2011 tohoku 9 0 earthquakes generated destructive tsunamis recorded by a large number of dart stations in the pacific ocean high resolution 15 s dart records yield mean energy decay times for these events of 17 3 24 7 and 24 6 h respectively we attribute these differences to the frequency content of the tsunamis specifically the samoa tsunami was a high frequency event with periods of 2 30 min whereas the chile and tohoku tsunamis were broad band events with periods of 2 180 min differences in frequency content are linked to differences in the source parameters samoa was a relatively small deep water earthquake while chile and tohoku were extensive shallow water earthquakes frequency dependent analysis of the chile and tohoku tsunamis indicates that shorter period waves attenuate much faster than longer period waves decay times range from 15 h for 2 6 min waves to 29 h for 60 180 min waves

ten years of seismic monitoring over a gas field abstract ten years of seismic recording allows us to locate more than 800 tremors with magnitudes ranging from 1 0 to 4 2 in a small 10 by 10 by 5 km volume near a major gas field lacq france the seismic activity began 10 yr after gas extraction began nearly all of the epicenters are located within the lateral extent of the gas field the only perturbation of the stress or strain fields which has the same spatial and temporal scale as the seismicity is the 500 bar drop in gas pressure due to 20 yr of gas exploitation demonstrating that these events are induced the network established to monitor this activity consists of eight telemetered stations including a well bottom geophone located at 3200 m depth using three dimensional relocation techniques we computed new hypocenter positions for more than 280 events these better located hypocenters form a diffuse zone that mimics the local dome structure taking the regional tectonic stresses into account we suggest that these ruptures may be the result of unfolding of the dome structure

sedimentology of the lower huronian supergroup early proterozoic elliot lake area ontario canada abstract the early proterozoic huronian supergroup is a slightly metamorphosed sedimentary succession locally 10 km thick exposed to the north of lake huron ontario canada the lower part of the supergroup comprising the matinenda mckim ramsay lake and pecors formations was studied in the quirke syncline area elliot lake and regions immediately to the west and south thirteen lithofacies are present trough and planar cross stratified sandstone quartz pebble conglomerate clay rich sandstone lenticular bedded sandstone siltstone mudstone laminated sandstone siltstone mudstone massive sandstone massive pebbly sandstone massive diamictite stratified matrix supported diamictite stratified clast supported diamictite graded diamictite and massive siltstone the lithofacies may be grouped into associations which correspond approximately to the mapped formations the crossbedded sandstones and conglomerates comprise a fluvial association matinenda formation which was formed mainly in shallow braided channels clay rich sandstone and the lenticular and laminated lithofacies constituting portions of the mckim and pecors formations were deposited on the strand and offshore areas of braid deltas interfingering laterally and vertically with the matinenda fluvial deposits four glacigenic subassociations are present in the ramsay lake formation an ice proximal subassociation i consists of massive pebbly sandstone and diamictite which progressively truncates the matinenda and mckim formations to the north the massive sandstone may be an ice override deposit formed by erosion and reworking of the underlying matinenda formation or a sub ice shelf rain out accumulation of locally eroded glacial debris subassociations ii and iii consist mainly of subaqueous sediment gravity flow and ice rain out deposits subassociation iv is interpreted as an ice proximal fluvial outwash deposit containing resedimented blocks of moraine material stratigraphic and paleocurrent data indicate a south dipping paleoslope that tilted southeast during the deposition of the fluvial and deltaic units a trough of relatively deep water extended nw se across the region transverse to the e w divergent continental margin hinge line that is assumed to have existed to the south of the project area analogies are suggested to mesozoic recent basins on the atlantic margin of canada where transverse paleogeographic trends reflect either landward extension of active oceanic fracture zones or reactivation of earlier structural lineaments

dispersion and nonlinear effects in the 2011 tohoku oki earthquake tsunami this study reveals the roles of the wave dispersion and nonlinear effects for the 2011 tohoku oki earthquake tsunami we conducted tsunami simulations based on the nonlinear dispersive equations with a high resolution source model the simulations successfully reproduced the waveforms recorded in the offshore deep sea and focal areas the calculated inundation area coincided well with the actual inundation for the sendai plain which was the widest inundation area during this event by conducting sets of simulations with different tsunami equations we obtained the followings insights into the wave dispersion nonlinear effects and energy dissipation for this event although the wave dispersion was neglected in most studies the maximum amplitude was significantly overestimated in the deep sea if the dispersion was not included the waveform observed at the station with the largest tsunami height 2 m among the deep ocean stations also verified the necessity of the dispersion it is well known that the nonlinear effects play an important role for the propagation of a tsunami into bays and harbors additionally nonlinear effects need to be considered to accurately model later waves even for offshore stations in particular including nonlinear terms rather than the inundation was more important when precisely modeling the waves reflected from the coast

explanation of temporal clustering of tsunami sources using the epidemic type aftershock sequence model temporal clustering of tsunami sources is examined in terms of a branching process model it previously was observed that there are more short interevent times between consecutive tsunami sources than expected from a stationary poisson process the epidemic type aftershock sequence etas branching process model is fitted to tsunami catalog events using the earthquake magnitude of the causative event from the centennial and global centroid moment tensor cmt catalogs and tsunami sizes above a completeness level as a mark to indicate that a tsunami was generated the etas parameters are estimated using the maximum likelihood method the interevent distribution associated with the etas model provides a better fit to the data than the poisson model or other temporal clustering models when tsunamigenic conditions magnitude threshold submarine location dip slip mechanism are applied to the global cmt catalog etas parameters are obtained that are consistent with those estimated from the tsunami catalog in particular the dip slip condition appears to result in a near zero magnitude effect for triggered tsunami sources the overall consistency between results from the tsunami catalog and that from the earthquake catalog under tsunamigenic conditions indicates that etas models based on seismicity can provide the structure for understanding patterns of tsunami source occurrence the fractional rate of triggered tsunami sources on a global basis is approximately 14 online material figures of residual analysis for tsunami and earthquake catalogs

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

a study of the microearthquakes of the gobles oil field area of southwestern ontario abstract from july 1980 to august 1984 the university of western ontario operated a small seismic telemetry network over the gobles oil field in southwestern ontario a total of 478 small earth tremors mainly in the 1 to 2 magnitude range were detected by this array there were three events greater than magnitude 3 felt by residents up to 15 km from the oil field approximately 10 events month were recorded on average although the actual number was rather erratic and tended to have a winter maximum event locations did not correlate with the actual positions of the oil and gas wells in the field but rather are confined to two main areas one lying 1 5 km northwest of the town of gobles and the other just south of the town the depths of the well recorded events were found to be near the depth of the producing horizon the observed first motion patterns indicated that at least two active faults almost perpendicular to each other are present in the area the results are consistent with the hypothesis that the events are induced or triggered by fluids which are pumped in and out of wells during secondary recovery activities

marshall islands fringing reef and atoll lagoon observations of the tohoku tsunami the magnitude 9 0 tohoku earthquake on 11 march 2011 generated a tsunami which caused significant impacts throughout the pacific ocean a description of the tsunami within the lagoons and on the surrounding fringing reefs of two mid ocean atoll islands is presented using bottom pressure observations from the majuro and kwajalein atolls in the marshall islands supplemented by tide gauge data in the lagoons and by numerical model simulations in the deep ocean although the initial wave arrival was not captured by the pressure sensors subsequent oscillations on the reef face resemble the deep ocean tsunami signal simulated by two numerical models suggesting that the tsunami amplitudes over the atoll outer reefs are similar to that in deep water in contrast tsunami oscillations in the lagoon are more energetic and long lasting than observed on the reefs or modelled in the deep ocean the tsunami energy in the majuro lagoon exhibits persistent peaks in the 30 and 60 min period bands that suggest the excitation of closed and open basin normal modes while energy in the kwajalein lagoon spans a broader range of frequencies with weaker multiple peaks than observed at majuro which may be associated with the tsunami behavior within the more irregular geometry of the kwajalein lagoon the propagation of the tsunami across the reef flats is shown to be tidally dependent with amplitudes increasing decreasing shoreward at high low tide the impact of the tsunami on the marshall islands was reduced due to the coincidence of peak wave amplitudes with low tide however the observed wave amplitudes particularly in the atoll lagoon would have led to inundation at different tidal phases

the 2011 tohoku tsunami on the coast of mexico a case study the tohoku east japan earthquake of 11 march 2011 m w 9 0 generated a great trans oceanic tsunami that spread throughout the pacific ocean where it was measured by numerous coastal tide gauges and open ocean dart deep ocean assessment and reporting of tsunamis stations statistical and spectral analyses of the tsunami waves recorded along the pacific coast of mexico have enabled us to estimate the principal parameters of the waves along the coast and to compare statistical features of the tsunami with other tsunamis recorded on this coast we identify coastal hot spots manzanillo zihuatanejo acapulco and ensenada corresponding to sites having highest tsunami hazard potential where wave heights during the 2011 event exceeded 1 5 2 m and tsunami induced currents were strong enough to close port operations based on a joint spectral analysis of the tsunamis and background noise we reconstructed the spectra of tsunami waves in the deep ocean and found that with the exception of the high frequency spectral band 5 cph the spectra are in close agreement with the true tsunami spectra determined from dart bottom pressure records the departure of the high frequency spectra in the coastal region from the deep sea spectra is shown to be related to background infragravity waves generated in the coastal zone the total energy and frequency content of the tohoku tsunami is compared with the corresponding results for the 2010 chilean tsunami our findings show that the integral open ocean tsunami energy i 0 was 2 30 cm2 or approximately 1 7 times larger than for the 2010 event comparison of this parameter with the mean coastal tsunami variance 451 cm2 indicates that tsunami waves propagating onshore from the open ocean amplified by 14 times the same was observed for the 2010 tsunami the tsunami colour frequency content for the 2011 tohoku tsunami was red with about 65 of the total energy associated with low frequency waves at frequencies 35 min the red colour i e the prevalence of low frequency waves in the 2011 tohoku as well as in the 2010 chile tsunamis is explained by the large extension of the source areas in contrast the 2014 and 2015 chilean earthquakes had much smaller source areas and consequently induced bluish high frequency tsunamis

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

mechanics of seismic instabilities induced by the recovery of hydrocarbons we review earthquake distributions associated with hydrocarbon fields in the context of pore pressure diffusion models poroelastic stress transfer and isostasy theory these three mechanisms trigger or induce seismic instabilities at both local scale d 5 km and at regional scale d 20 km the modeled changes in stress are small 1 mpa whatever the tectonic setting each mechanism corresponds to different production processes 1 local hydraulic fracturing due to fluid injection induces seismic slip on cracks ml 3 within the injected reservoir through decreasing the effective stress 2 pure fluid withdrawal causes pore pressure to decrease within the reservoir it triggers adjustments of the geological structure to perturbations related to the reservoir response to depletion poroelastic mechanisms transfer this stress change from the reservoir to the surrounding levels whereml 5 seismic instabilities occur either above or below the reservoir 3 massive hydrocarbon recovery induces crustal readjustments due to the removal of load from the upper crust it can induce larger earthquakes ml 6 at greater distance from the hydrocarbon fields than the two other mechanisms

application of palynomorph darkness index pdi to assess the thermal maturity of palynomorphs a case study from north africa abstract this study focuses on the thermal maturity assessment of silurian devonian sediments from the ghadamis basin north africa comparing optical and geochemical analyses of palynomorphs in southern tunisia the investigated subsurface cored section comprises the argiles principales formation of silurian age in libya the succession studied covers the awaynat wanin iii and iv formations assigned to the late devonian frasnian famennian geochemical approaches used to reconstruct thermal alteration of sediments necessitate advanced relatively expensive analytical techniques in this study the effectiveness of the less costly relatively simple approaches of visually assessing palynomorph colour to determine thermal alteration i e sci spore colour index tai thermal alteration index and pdi palynomorph darkness index was evaluated sci and tai are qualitative methods strictly related to the operator s perception which use ten and five point scales respectively to characterize colour in terms of illustrated specimens and or descriptions in contrast pdi is obtained from the measurement of the red green and blue rgb intensities of light transmitted through palynomorphs using standard optical microscopes and digital cameras the palynomorph based thermal alteration estimates were compared to rock eval pyrolysis data from the same samples this calibration showed a linear relationship between these quantitative parameters and pdi these results show that pdi is more reliable than the sci and tai methods

detection of tsunami driven phase and amplitude perturbations of subionospheric vlf signals following the 2010 chile earthquake we report on specific fluctuations in phase and amplitude of vlf signals that correlate both spatially and temporally with the passage of the tsunamis recorded by the deep ocean assessments and reporting of tsunamis bottom pressure stations measurements from the vlf lf receiver sited in petropavlovsk kamchatsky and sensor buoys placed throughout the pacific ocean at great distances hawaii and japan from the epicenter are consistent with the hypothesis that the ocean tsunami following the chile earthquake on 27 february 2010 radiated internal gravity waves which propagated through the lower ionosphere

effects of the march 2011 japanese tsunami in bays and estuaries of se australia on 11 march 2011 a subsea earthquake off the north eastern coast of honshu island japan generated a huge tsunami which was felt throughout the pacific at the opposite end of the pacific ocean on the south east coast of australia multiple reflections scatterings and alternate pathways lead to a prolonged and complicated response this response was largely unaltered in crossing the continental shelf but was then transformed by bay resonances and admittances these effects are described using data from tide recorders sparsely spread over 1 000 km of the coast some new adaptations and applications of time series analysis are applied to separate tsunami waves that have followed different pathways but contain the same spectral components the possible types of harbour response are classified and illustrated despite its small height in this region the tsunami put several swimmers at serious risk and generated strong harbour oscillations which should be considered when generating future warnings

pressure forced seiches of large amplitude in inlets of the balearic islands large amplitude harbor seiches usually occur in summer in the balearic islands a significant correlation between sea level oscillations and atmospheric pressure disturbances has been found though a proved physical mechanism to account for this atmosphere ocean interaction is still missing using a flat bottom shallow water model we show that a direct coupling between atmospheric pressure and the free mode of an inlet is unlikely but that an oceanic wave of atmospheric origin can act as an intermediate mechanism and adequately force the inlet by resonance the phase relationship derived from this mechanism is in good agreement with observations provided the whole spectrum of oceanic waves is in opposite phase to the generating atmospheric disturbance we also show that the very large oscillations observed at ciutadella an elongated shallow inlet in the west coast of menorca balearic islands can be explained in terms of the particular shape of this inlet

direct energy estimation of the 2011 japan tsunami using deep ocean pressure measurements 1 we have developed a method to compute the total energy transmitted by tsunami waves to the case where the earthquake source is unknown by using deep ocean pressure measurements and numerical models tsunami source functions based on the first wave recorded at the two closest tsunameters deep ocean assessment and reporting of tsunamis dart our analysis suggests that the march 11 2011 tohoku oki tsunami generated off japan originated from a 300 400 km long and 100 km wide area and the total propagated energy is 3 1015j with 6 uncertainty measurements from 30 tsunameters and 32 coastal tide stations show excellent agreement with the forecasts obtained in real time our study indicates that the propagated energy and the source location are the most important source characteristics for predicting tsunami impacts interactions of tsunami waves with seafloor topography delay and redirect the energy flux posing hazards from delayed and amplified waves with long duration seafloor topography also gives its spectral imprint to tsunami waves travel time forecast errors are path specific and correlated to the major wave scatterers in the pacific numerical dissipation in the propagation modeling highlights the need of high resolution inundation models for accurate coastal predictions on the other hand it also can be used to account for physical dissipation to achieve efficiency our results provide guidelines for the earliest reliable tsunami forecast warnings of long duration tsunami waves signals and enhancement of the experimental tsunami forecast system we apply the method to quantify the energy of 15 past tsunamis independently from earthquake magnitudes the small tsunami to seismic radiation energy ratios and their variability 0 01 0 8 reinforce the importance of using deep ocean tsunami data the direct measures of tsunamis for estimates of tsunami energy and accurate forecasting

possibility of induced seismicity in the vicinity of the sleepy hollow oil field southwestern nebraska an array of four seismographs operating in northwestern kansas and southwestern nebraska detected 31 earthquakes in the magnitude range 0 6 to 2 9 from march 1979 to march 1980 of these 22 were recorded at enough stations to allow accurate location and at least three of them were felt by local residents sixteen of the located events occurred in the immediate vicinity of the most productive oil field in nebraska the sleepy hollow field a mail canvass revealed a well constrained felt area about 10 km across which coincides remarkably well with the oil field water injection has been used as a method of enhanced recovery in this field since 1966 some of the earthquakes occurred on possible downward extensions of faults in the deeper sedimentary rocks and granite basement implying that some of the seismicity may be induced deeper events and other supporting data however suggest current tectonic activity on the chadron cambridge arch the recently installed eight station sleepy hollow seismic network should provide the data necessary to test these hypotheses