deposition models for chronological records abstract long term sedimentary sequences provide a wealth of useful information for research into the palaeo environment especially in relation to past climate change shorter records provide similar information in many archaeological contexts however if such records are to be used to provide precise timing of events and more critically the relative timing between different records methods are needed to provide accurate and precise age depth models for these sequences given the imprecision of individual calibrated radiocarbon determinations it is necessary to use the information we have about the deposition process to refine our chronologies and also to provide interpolation between dated levels in any sequence even with layer counted chronologies the uncertainties are sometimes hard to quantify this paper outlines a range of bayesian models for deposition which have been implemented in the computer programme oxcal these models can be used to combine information from the sediments themselves with radiocarbon or other direct dating information such models have the potential to integrate information between different records and provide a coherent chronology on which to base environmental or archaeological research

sedimentary features of the seismo turbidites lake biwa japan abstract seismo turbidite layers are deposited at the foot of the steep slope of the half graben in which lake biwa has accumulated sedimentary studies especially of grain size distribution of selected turbidites provide excellent information for clarifying the distinctive features of general seismo turbidites development of the two constituent sublayers lower sandy sublayer and upper silt sublayer lack or limited appearances of traction indicating structures and characteristic grain size distribution in the two constituent sublayers are most remarkable and significant the characteristic grain size distribution features are coarse tail grading in a relatively thick sandy sublayer exceptionally rapid distribution grading through the thin boundary interval between the two sublayers height increase and fluctuation of the silt mode and high clay content brief discussion was made on the causes of these sedimentary features the need and importance of further comparative studies of various turbidites known triggering forces are emphasized

tide gauge observations of 2004 2007 indian ocean tsunamis from sri lanka and western australia tide gauge data collected from sri lanka three stations and western australia eleven stations during the indian ocean tsunamis which occurred in december 2004 march 2005 july 2006 and september 2007 and incorporated five tsunamis were examined to determine tsunami behaviour during these events during the december 2004 tsunami maximum wave heights of 3 87 m and 1 75 m were recorded at colombo sri lanka and bunbury western australia respectively the results indicated that although the relative magnitudes of the tsunamis varied the tsunami behaviour at each station was similar this was due to the effect of the local and regional topography at all tide gauges the spectral energy corresponding to periods between 20 and 85 minutes increased during the tsunami the sea level data obtained from the west and south coasts of sri lanka colombo and kirinda indicated the importance of wave reflections from the maldives island chain which produced the maximum wave two to three hours after the arrival of the first wave in contrast trincomalee on the east coast did not show evidence of a reflected wave similarly along the west coast of australia the highest waves occurred 15 hours after the arrival of the first wave here based on travel times we postulated that the waves were reflected from the mascarene ridge and or the island of madagascar reflected waves were not present in the 2006 tsunami where the primary waves propagated away from topographic features one of the main influences of the tsunami was to set up oscillations at the local resonance frequency because sri lanka and western australia have relatively straight coastlines these oscillations were related to the fundamental period of the shelf oscillation for colombo this corresponded to 75 minute period whereas in geraldton and busselton australia the four hour period was most prominent at jurien bay and fremantle the resonance period was 2 7 hours

genesis and depositional model of subaqueous sediment gravity flow deposits in a lacustrine rift basin as exemplified by the eocene shahejie formation in the jiyang depression eastern china abstract subaqueous sediment gravity flow ssgf deposits have recently been recognized as a major reservoir plays in lacustrine basins research on their genesis and depositional models are crucial to understand gravity flow evolution and the distribution of their deposits this study analysed ssgf deposits in the third member of the shahejie formation in the jiyang depression eastern china based on 3 d seismic data well log data and core observations the types and origins of ssgf the distribution patterns and depositional models of ssgf deposits have been investigated the dominant types of ssgf include muddy debris flows sandy debris flows high density turbidity currents surge like low density turbidity currents and quasi steady low density turbidity currents which are mainly caused by river floods and sediment failures the overall distribution of ssgf deposits is controlled by the sediment supplies basin structure and sequence stratigraphic framework paleotopography flood energy triggering mechanism and the slope angle of the delta front are also important ssgf deposits associated with river floods can be further subdivided into elongated and fan shaped deposits elongated sandstones are composed predominantly of bedload dominated and suspension load dominated hyperpycnal flow deposits the fan shaped sandstones can be subdivided into an inner fan a middle fan and an outer fan inner fan deposits are dominated by gully filling debrites middle fan deposits are composed predominantly of channel fill deposits while outer fan deposits consist of thin bedded and laterally extensive lobe intervals ssgf deposits triggered by sediment failures can be further subdivided according to their proximity to slumping proximal intermediate and distal parts the proximal deposits are composed predominantly of slide and slump deposits the intermediate deposits are dominated by sandy debrite tongues while the distal deposits are composed predominantly of thin bedded surge like low density turbidites this study offers some insight into the types origin of gravity flow as well as the distribution of their deposits in a lacustrine rift basin

widespread deformation of basin plain sediments in aysen fjord chile due to impact by earthquake triggered onshore generated mass movements abstract the 2007 mw 6 2 earthquake in aysen fjord caused widespread basin plain deformation and has had prehistorical predecessors both superficial and buried deformed basin plain deposits are mapped using multibeam bathymetry and seismic reflection sparker profiling the seismic signature of the sediment was ground truthed with short cores on key locations deformed basin plain deposits induced by the 2007 earthquake can be divided in frontally emergent and confined deposits with both a deep and shallow basal shear surface all deformed basin plain deposits with a deep basal shear surface are induced by the weight and impact of a slope adjacent mass flow wedge the frontally emergent most mobile basin plain deformation is triggered by mass flows originating from onshore mass movements i e debris flows rock slides and avalanches propagating into the fjord this basin plain deformation results in vertical seafloor offsets of up to 20 m therefore it might be even more important for far field tsunami propagation than the impact of the onshore mass movements on the sea surface in the depressions created by the basin plain deformation megaturbidites occur while more distally sandy density flow deposits cover the seafloor the data also indicates that these density flows propagate slower than the basin plain deformation based on correlations with the two main eruptions of the hudson volcano we hypothesize that during the holocene three to four similar events have struck the fjord the small variability of the structural characteristics of the liquine ofqui fault zone in the northern patagonian fjordland and historical seismic swarms in this area make us conclude that similar hazards should be taken into account for most of the fjords in this region

the ionian and alfeo etna fault zones new segments of an evolving plate boundary in the central mediterranean sea highlights plate boundary re organization in the central mediterranean sea segmentation of the subduction complex along lithospheric transverse faults step faults in the ionian sea pleistocene active faulting and mt etna formation abstract the calabrian arc is a narrow subduction rollback system resulting from africa eurasia plate convergence while crustal shortening is taken up in the accretionary wedge transtensive deformation accounts for margin segmentation along transverse lithospheric faults one of these structures is the nnw sse transtensive fault system connecting the alfeo seamount and the etna volcano alfeo etna fault aef a second nw se crustal discontinuity the ionian fault if separates two lobes of the ca subduction complex western and eastern lobes and impinges on the sicilian coasts south of the messina straits analysis of multichannel seismic reflection profiles shows that 1 the if and the aef are transfer crustal tectonic features bounding a complex deformation zone which produces the downthrown of the western lobe along a set of transtensive fault strands 2 during pleistocene times transtensive faulting reactivated structural boundaries inherited from the mesozoic tethyan domain which acted as thrust faults during the messinian and pliocene 3 the if and the aef and locally the malta escarpment accommodate a recent tectonic event coeval and possibly linked to the mt etna formation regional geodynamic models show that whereas aef and if are neighboring fault systems their individual roles are different faulting primarily resulting from the ese retreat of the ionian slab is expressed in the northwestern part of the if the aef on the other hand is part of the overall dextral shear deformation resulting from differences in africa eurasia motion between the western and eastern sectors of the tyrrhenian margin of northern sicily and accommodating diverging motions in the adjacent compartments which results in rifting processes within the western lobe of the calabrian arc accretionary wedge as such it is primarily associated with africa eurasia relative motion

seismic and landslide source of the 1908 straits of messina tsunami sicily italy 1 one hundred years ago december 1908 a devastating tsunami associated with an earthquake struck the straits of messina area causing many casualties on the basis of seismic data and observed runups and arrival times we suggest that the tsunami was likely generated by coseismic seafloor displacement coupled with a small submarine landslide triggered by the earthquake backwards ray tracing using a depth dependent velocity field submarine slope analysis and inferences form the main drainage network allowed us to identify possible locations for the source of the submarine landslide we then performed direct simulations of tsunamis generated by the earthquake and landslides and identified the tsunami source earthquake plus landslide that best fits observational data in a small volume submarine landslide 1 5 km3 located offshore nizza sicily

possible submarine tsunami deposits on the outer shelf of sendai bay japan resulting from the 2011 earthquake and tsunami off the pacific coast of tohoku abstract although it is accepted that large tsunami waves impact the sea floor the response of surface sediments to tsunami is not yet fully understood tsunami by the 2011 off the pacific coast of tohoku earthquake caused considerable damage to northeast japan surface sediments on the outer shelf of sendai bay also show evidence of strong ground motion and agitation by the subsequent tsunami sediments in the hemipelagic mud below the erosional surface contain vein like structures providing evidence of strong ground motions induced by the earthquake two turbidite sequences are present above the erosional surface in which 134 cs and 137 cs only occur in the upper turbidite unconsolidated mud on the inner mid sendai shelf was agitated and resuspended by the high frictional velocities associated with the tsunami waves the high concentration of suspended sediment in the water column above the shelf is likely to have generated turbidity currents and have made the lower turbidite after the release of 134 cs by the accident at the fukushima no 1 nuclear power plant the second turbidity current generated and created the upper turbidite

p wave velocity tomography from local earthquakes in western mexico in western mexico the subduction of the rivera and cocos plates beneath the north america plate has deformed and fragmented the overriding plate forming several structural rifts and crustal blocks to obtain a reliable subsurface image of the continental crust and uppermost mantle in this complex area we used p wave arrivals of local earthquakes along with the fast marching method tomography technique we followed an inversion scheme consisting of 1 the use of a high quality earthquake catalog and corrected phase picks 2 the selection of earthquakes using a maximum location error threshold 3 the estimation of an improved 1 d reference velocity model and 4 the use of checkerboard testing to determine the optimum configuration of the velocity nodes and inversion parameters surprisingly the tomography results show a very simple vp distribution that can be described as being controlled by geologic structures formed during two stages of the separation of the rivera and cocos plates the earlier period represents the initial stages of the separation of the rivera and cocos plates beneath western mexico the later period represents the more advanced stage of rifting where the rivera and cocos plates had separated sufficiently to allow melt to accumulate below the colima volcanic complex during the earlier period 14 or 10 1 6 ma ne sw oriented structures lineaments such as the southern colima rift were formed as the two plates separated during the second period 1 6 ma to the present the deformation is attributed to magma generated within and above the tear zone between the rivera and cocos plates rising beneath the region of the colima volcanic complex the rising magma fractured the overlying crust forming a classic triple rift junction geometry this triple rift system is confined to the mid to lower crust perhaps indicating that this rifting process is still in an early stage this fracturing along with fluid circulation and associated heat advection within the fractures can easily explain the observed distribution of vp as well as many of the results of previous seismological studies also surprisingly we find no evidence at deep crustal depths to support either a trenchward migration of the volcanic arc or toroidal asthenospheric flow through the slab tears bounding the jalisco block to the nw and se

new simulations and understanding of the 1908 messina tsunami for a dual seismic and deep submarine mass failure source abstract over 100 years after the event the mechanism of the 1908 messina tsunami remains unresolved the up to 12 m runups observed along the coasts of sicily and calabria cannot be explained by the coseismic tsunami so recent studies have proposed a dual earthquake submarine mass failure smf mechanism here we propose a new dual source and use it to simulate tsunami generation with a three dimensional non hydrostatic model coupled to a two dimensional fully nonlinear and dispersive model to simulate tsunami propagation to shore we first reanalyze observations of tsunami arrival times from eyewitnesses acquired shortly after the 1908 event and a tsunami record at a tide gauge in malta similar to earlier work this data is used to locate the likeliest tsunami source area by inverse wave ray tracing but accounting for frequency dispersion effects on wave celerity uncertainty in reported arrival times and a time delay between the eq and smf triggering analyzing the seafloor morphology in this area we identify a new smf at the foot of the fiumefreddo valley northeast of mount etna the general location is consistent with earlier studies however our smf is much smaller 2 km3 than e g that of billi et al 2008 and is a fairly rigid block slump rather than a translational smf we model the block motion and simulate tsunami generation from a dual eq smf source and its propagation to shore in higher resolution grids and based on more accurate bathymetry and topography than in earlier work runups and travel times agree well with observations except for runups on either side of the messina straits north of the smf which are still underpredicted in the far field simulations reproduce well the arrival time and initial wave amplitudes at the malta tide gauge our newly parameterized smf and modeling improve tsunami runups simulated near the smf location and south of it however as with all previous modeling of this event additional sources are required to explain runups in the northern messina straits which we suggest might be smaller and shallower smfs located in this area these will be considered in future work

multidirectional synchronously triggered seismo turbidites and debrites revealed by x ray computed tomography ct on 21 april 2007 a mw 6 2 earthquake struck aysen fjord chilean patagonia and caused onshore and offshore mass movements which triggered tsunamis and density flows in the fjord to better understand the facies successions in and the intercalation of the density flow deposits a study was made of the 2007 deposits in 22 short sediment cores taken in the inner aysen fjord by combining grain size analysis with x ray computed tomography scanning it was possible to demonstrate that the encountered facies correspond to classical divisions of debrites and turbidites the single event deposits consist of a succession of several sub deposits deposited under different flow directions and can be interpreted as stacked turbidites orientations of i folds ii imbricated mud clasts iii backsets and foresets of climbing ripples and iv asymmetrical convolute lamination were used to determine relative flow directions at the location of the cores by assigning the basal flow of the stacked debrites and turbidites to the closest principal mass flow the absolute flow directions of the sub deposits were determined which in combination with multibeam basin floor morphology allowed reconstruction of the 2007 density flow successions in aysen fjord furthermore alternating flow directions provide evidence for a seiche induced by the density flows it was concluded that x ray computed tomography scans provide crucial information for reconstructing palaeoflows and can be a useful tool in marine and lacustrine sedimentology and palaeoseismology the multidirectionality of sub deposits in turbidites is next to differences in mineralogy a new criterion to identify stacked turbidites these multidirectional stacked turbidites are an indication of simultaneous triggering of density flows and can therefore in most cases be attributed to earthquakes ruling out other triggers such as floods storms or other sediment failures this article is protected by copyright all rights reserved

reply to comment by andrea argnani et al on on the cause of the 1908 messina tsunami southern italy within minutes after the passage of the seismic waves atsunami with maximum observed runup of almost 12 m hitthe coasts of calabria and sicily platania 1909 baratta 1910 soon after the catastrophic events omori 1909 concluded that one remarkable fact is that the tsunamiwasstrongestatthoseplaceswheretheearthquakeshockwasnot most violent indicating the probable non coincidencein position of the origin of the earthquake with that ofthe tsunami by using computer simulations tinti andarmigliato 2003 reached a similar conclusion the firstconclusion we arrive at is that it is difficult to find a singlesource matching simultaneously both tsunami and levelingdata recently we presented new results supporting thehypothesis that the tsunami was generated by a submarinelandslide triggered by the earthquake at c 40 km from theepicentral area billi et al 2008 argnani et al 2009 nowproduce new marine data and numerical models to questionsome of our inferences here we reply to their criticisms

three dimensional gravity modeling of the geysers hydrothermal system and vicinity northern california the gravity low associated with the geysers hydrothermal system is the southwest lobe of a regional 24 mgal gravity low centered near mount hannah in northern california by subtracting the effect of a deep low density source beneath mount hannah a large 3 to 5 mgal gravity low is defined this gravity low is interpreted to coincide with the present and past locations of the geysers hydrothermal system the producing steam field is now to the northeast of the anomaly and overlaps its northeastern boundary the northeastern boundary of the anomaly consists of dense ultramafic and mafic rocks between 0 5 and 1 0 km in thickness which mask whatever density anomaly is associated with the steam reservoir below them a three dimensional density model constructed to fit this residual gravity field employs a low density volume of about 100 km 3 that has a density contrast of 0 06 g cm 3 if a deep low density source is included in the model the shallow density cannot be less than 0 04 g cm 3 this shallow low density anomaly could be caused by a combination of high temperatures unsaturated conditions dissolution and fracturing and it may be flanked by density gradients due to chemical precipitation at the boundaries of the hydrothermal system the possibility of a deep low density source to the gravity low indicates a possible extension of the deep low density source that produces the 24 mgal low centered near mount hannah an overlapping low velocity anomaly coincides with the low density region below mount hannah and the low velocity anomaly also extends beneath the geysers these low density and low velocity sources may be representative of the heat source that generated the geysers hydrothermal system

sedimentology of seismo turbidites off the cascadia and northern california active tectonic continental margins northwest pacific ocean abstract holocene turbidites from turbidite channel systems along the active tectonic continental margins of the cascadia subduction zone offshore vancouver island to mendocino triple junction and the northern san andreas transform fault the triple junction to san francisco bay have been analyzed for sedimentologic features related to their seismic origin centimeter thick silt sand beds turbidite base capped by mud layers turbidite tail and interbedded with hemipelagic silty clay intervals with high biogenic content have been characterized by visual core descriptions grain size analysis x ray radiographs and physical properties along the northern california margin in upstream single tributary canyons and channels most turbidites are uni pulsed classic fining up whereas downstream below multiple tributary canyon and channel confluences most deposits are stacked turbidites because each set of stacked turbidites has no hemipelagic sediment between each turbidite unit and each unit has a distinct mineralogy from a different tributary canyon we interpret that a stacked turbidite is deposited by several coeval turbidity currents fed by multiple tributary canyons and channels with synchronous triggering from a single san andreas fault earthquake the cascadia margin is characterized by individual multi pulsed turbidites that contain multiple coarse grained sub units without hemipelagic sediment between pulses because the number and character of multiple coarse grained pulses for each correlative multi pulsed turbidite is almost always constant both upstream and downstream in different channel systems for 600 km along the margin we interpret that the earthquake shaking or aftershock signature is usually preserved for the much stronger cascadia 9 mw compared to weaker california 8 mw earthquakes which result in upstream uni pulsed turbidites and downstream stacked turbidites consequently both the strongest 9 mw great earthquakes and downstream confluences cause multi pulsed and stacked turbidites that are typical for seismo turbidites generated by a single great earthquake along both margins earthquake triggering and multi pulsed or stacked turbidites become an alternative explanation for amalgamated turbidite beds in active tectonic margins and show that multiple grain size pulses and reverse grading are not unique criteria for hyperpycnites thalweg levee turbidites or mini basin margin turbidites the analyses of the turbidites along the cascadia and northern california margins reveal common sedimentologic characteristics of turbidites triggered by great earthquakes that can be used to distinguish seismo turbidites in other active tectonic margins around the world

lake sediments record high intensity shaking that provides insight into the location and rupture length of large earthquakes on the alpine fault new zealand abstract understanding the seismic hazard posed by large earthquakes requires paleoseismic investigation because most faults have not ruptured repeatedly during the period of historic records however determining the location and length of fault ruptures using paleoseismic data remains challenging our study demonstrates that lake sediments record the high intensity shaking that occurs proximal to fault rupture allowing the location and length of ruptures to be reconstructed in two lakes adjacent to the alpine fault new zealand seismic shaking is recorded as subaqueous mass wasting derived turbidites formed by coseismic subaqueous slope failures which are overlain by sets of hyperpycnites representing elevated fluvial sediment fluxes from earthquake induced landslides precise radiocarbon age models show that shaking events are synchronous between the two lake sites and correlate with the timing of known alpine fault earthquakes modelled shaking intensities for the last two alpine fault earthquakes show that subaqueous mass wasting occurs when shaking intensities exceed modified mercalli scale mm vi vii and that fluvial sediment fluxes from earthquake induced landslides occur when shaking intensities exceed mm ix the data demonstrate that lake records distinguish between strong mm vi and violent mm ix shaking at a lake site the ability to map the spatial extent of mm ix shaking provides new insights into the timing and extent of rupture for the last five earthquakes on the alpine fault the study demonstrates that lake deposits constrain the spatial extent of rupture during large earthquakes and may yield long records of the spatial and temporal patterns of fault rupture

remobilization of surficial slope sediment triggered by the a d 2011 mw 9 tohoku oki earthquake and tsunami along the japan trench the a d 2011 tohoku oki m w 9 earthquake ruptured the megathrust up to the japan trench with a large displacement and caused a catastrophic tsunami this study is the first to use short lived radioisotopes including those emitted by the damaged nuclear reactors at the fukushima daiichi nuclear power plant japan to document the remobilization of the upper few centimeters of sediment as a highly significant process triggered by the earthquake and its aftershocks targeting the post earthquake environment allowed characterization of the sedimentary signature of this event for a better understanding of paleoearthquakes in japan and other tectonically active boundary areas the results stem from 23 piston cores recovered by the 2013 expedition nt13 19 of the japan agency for marine earth science and technology we document submarine homogeneous muddy flow deposits that were triggered by ground motion in 2011 they are highly enriched with excess xs xs 210 pb requiring only centimeters deep sediment remobilization over large areas of the seafloor some contain 134 cs and 137 cs radioisotopes derived from the fukushima nuclear reactors indicating that sedimentation persisted for at least 30 days after the main shock we found these deposits at all sampling sites in an 5000 km 2 area of the seafloor in 4000 6000 m of water depth the study area extends for 260 km parallel to the strike of the trench the thickness of this tohoku layer 3 200 cm increases toward the zone of maximum megathrust slip where deposits are thickest these results demonstrate that the shaking of the seafloor above large megathrust ruptures near the trench remobilized surficial unconsolidated sediment for hundreds of kilometers the characteristics of these deposits may typify deposits resulting from large fault slips like that of the tohoku oki earthquake but also other earthquake deposits contributing to their identification in the sedimentary record globally

a 125 kyr long geological record of seismic source repeatability the messina straits southern italy and the 1908 earthquake ms7 2 the occurrence of characteristic earthquakes along segments of major active belts has been described as early as the beginning of the century the large 1908 messina straits blind normal faulting earthquake provides an opportunity to investigate the repetition of characteristic earthquakes and the persistency of the main features of the fault zone over a time scale in the order of 100 kyr we have compared seismological and geodetic descriptions of the 1908 rupture process with long term crustal deformation recorded at different stratigraphic levels by marine terraces marine sedimentary units and landscape features the wealth of elevated coastal features in and around a region affected by large normal faulting earthquakes indicates that coseismic strain is superimposed on much faster uplift on a regional scale we investigated in detail the pattern of deformation of the 125 kyr old lowest emergent terrace and found that it mimics the pattern of elevation changes observed following the earthquake this suggests 1 that the 1908 earthquake is characteristic 2 that its segment boundaries have been stationary during the past 125 kyr and 3 that even the locations of the regions of largest coseismic release do not change through many seismic cycles based on a comparison between observed heights of the 125 kyr terrace and 1908 displacements we estimated an average repeat time of 1000 yr for a 1908 type earthquake we also investigated the height position age and state of deformation of older terraces and found 1 that uplift of the region started about 1 ma and has since continued rather uniformly at 0 9 1 4 mm yr 1 2 that during this time the straits have narrowed at a rate of 10 20 mm yr 1 and 3 that all the main geomorphic features of the messina straits result from the interaction of fast regional uplift 1908 type coseismic subsidence and global sea level fluctuations

tsunami landfalls in the maltese archipelago reconciling the historical record with geomorphological evidence the maltese islands lie in the middle of the tsunamigenic mediterranean domain around whose margins and islands evidence of historic tsunami landfall has been increasingly recognized in recent years critical review of historical evidence of events in 1693 and 1908 indicates extremely modest tsunami impacts in marked contrast though recently discovered geomorphological evidence summarized herein suggests that malta s coastlines have been overwashed up to elevations of 20 m asl by an exceptional event a new perspective is provided by a review of the central mediterranean context within which the maltese evidence is located recent advances in understanding of the holocene sequence forming the mediterranean sea floor present a new stratigraphic and temporal framework within which to elucidate tsunami history within 100 km of malta terrestrial stratigraphy on sicily also provides supporting evidence of tsunami impact review of these advances suggests that the exceptional event required to emplace the most extreme sedimentary and geomorphological signatures on and around malta is likely to have had a far field origin the currently available circumstantial evidence points strongly toward a probability that the ad365 earthquake and tsunami were responsible this in turn enables critical reassessment of the exposure of malta to tsunami hazard

untangling the complex origin of turbidite activity on the calabrian arc ionian sea over the last 60ka abstract the ionian sea due to the presence of two accretionary prisms the calabrian arc and the mediterranean ridge associated with the subduction of the nubia plate and the eurasia plate is the witness of large and catastrophic turbidite events these events are associated with high magnitude earthquakes and tsunamis they lead an important gravity driven sedimentary deposit in the ionian basin in this study we analysed turbidite deposits in order to establish a calendar of the palaeoseismicity and volcaniclastic events from etna on the calabrian arc two gravity cores collected in a slope basin on the calabrian arc and in the ionian abyssal plain record more than two hundred turbidites over the last 60 000 years these turbidites were dated with a multi proxy approach radiometric dating tephrochronology and sapropels the origin of the turbidites was studied with a sedimentary approach grain size lithology thin section and geochemistry of volcanic glass the results suggest that three triggers are responsible for the deposits of turbidites there are siliciclastic turbidites triggered by earthquakes and tsunamis waves and volcaniclastic turbidites triggered by the etna volcano eruptions or flank collapses co seismic turbidites present different recurrence times depending on the location of the core on the calabrian arc recurrence times vary between 450 and 1000 years according to the periods in time on the abyssal plain recurrence times are shorter and more regular around every 240 years

submarine earthquake geology along the north anatolia fault in the marmara sea turkey a model for transform basin sedimentation abstract the submerged portions of the north anatolia fault system beneath the marmara sea were studied with high resolution multibeam bathymetry subbottom profiling and sediment cores the major objectives were to learn about the seismic and tectonic history of the fault from the stratigraphic record at a scale similar to paleoseismic studies on land and to develop tools for submarine earthquake geology that can be applied to fault controlled basins in general we focused on holocene sediment in several marmara sea basins of different sizes the approach was to test whether 1 the depocenters of the larger basins contain a record of all historic ms 7 earthquakes within the marmara sea region 2 the small transform basins record earthquakes that rupture through them 3 vertical and strike slip holocene deformation can be quantified and 4 the effects of an earthquake generally includes both primary structural features due to rupture of the sea floor such as strata offset scarps and tilting as well as secondary effects due to shaking such as mass wasting and gravitational flows we found evidence of earthquakes that we correlate with historic events in 181 ad 740 ad 1063 ad 1343 ad 1509 ad 1766 ad 1894 ad and 1912 ad the geologic evidence is primarily from those basins adjacent to the rupture as inferred from historic data this suggests that coseismic deformation of the sea floor along the rupture is a critical factor in the sedimentary record we propose a qualitative sedimentation model that relates this coseismic deformation to mass wasting of the slope scour of the basin floor seiche motions and homogenite deposition frequent earthquake activity sheds sediments from the flanks contributes to the much thicker sediment on the basin floor and decreases the likelihood of sediment failures in response to normal marine gravity driven processes the surveying techniques and approaches used have therefore the potential of documenting earthquake ruptures of fault segments and to extend the earthquake record far before the known history thus improving hazard evaluations and the fundamental understanding of earthquake process

lake sediments as natural seismographs a compiled record of late quaternary earthquakes in central switzerland and its implication for alpine deformation central switzerland lies tectonically in an intraplate area and recurrence rates of strong earthquakes exceed the time span covered by historic chronicles however many lakes are present in the area that act as natural seismographs their continuous datable and high resolution sediment succession allows extension of the earthquake catalogue to pre historic times this study reviews and compiles available data sets and results from more than 10 years of lacustrine palaeoseismological research in lakes of northern and central switzerland the concept of using lacustrine mass movement event stratigraphy to identify palaeo earthquakes is showcased by presenting new data and results from lake zurich the late glacial to holocene mass movement units in this lake document a complex history of varying tectonic and environmental impacts results include sedimentary evidence of three major and three minor simultaneously triggered basin wide lateral slope failure events interpreted as the fingerprints of palaeoseismic activity a refined earthquake catalogue which includes results from previous lake studies reveals a non uniform temporal distribution of earthquakes in northern and central switzerland a higher frequency of earthquakes in the late glacial and late holocene period documents two different phases of neotectonic activity they are interpreted to be related to isostatic post glacial rebound and relatively recent re activation of seismogenic zones respectively magnitudes and epicentre reconstructions for the largest identified earthquakes provide evidence for two possible earthquake sources i a source area in the region of the alpine or sub alpine front due to release of accumulated north west south east compressional stress related to an active basal thrust beneath the aar massif and ii a source area beneath the alpine foreland due to reactivation of deep seated strike slip faults such activity has been repeatedly observed instrumentally for example during the most recent magnitude 4 2 and 3 5 earthquakes of february 2012 near zug the combined lacustrine record from northern and central switzerland indicates that at least one of these potential sources has been capable of producing magnitude 6 2 to 6 7 events in the past

tsunami induced sediment transport in the abyssal mediterranean sea an unusual stratigraphic unit nicknamed homogenite fills topographic lows in the complex ridge and trough bathymetry at two survey sites on the western mediterranean ridge and the calabrian ridge on near bottom 4 khz seismic reflection profiles this unit us an acoustically transparent near surface flat lying layer whereas in cores it is a homogeneous gray marl as much as 7 m thick grain size decreases upcore within the unit implying that it was deposited in a single event controlled by gravitational settling the stratigraphic position of the homogenite relative to a firmly dated sapropel bed suggests emplacement between 4400 and 3100 yr b p the source of the homogenite is inferred to be the nearby basin walls farther east two other sites with similar rugged topography lack homogenite entirely a triggering mechanism is required which is capable of initiating massive sediment transport simultaneously in many separate basins at the western two survey sites but which is not effective at the eastern sites a large archeologically recorded earthquake of the correct age is considered and rejected because its epicenter is closer to the nonhomogenite bearing sites than to the sites where this sediment type was observed and because several other earthquakes of comparable magnitude have since been recorded in the area whereas the homogenite is unique the 3 500 yr b p collapse of the caldera of the volcano of santorini caused a huge tsunami which is recorded archeologically and geologically around the eastern mediterranean because of refraction of the tsunami by the bathymetry and because the caldera collapsed in its southwest corner a disproportionate amount of tsunami energy was directed toward the western area where homogenite is observed in contrast the homogenite free sites were relatively sheltered an order of magnitude calculation shows that the near bottom oscillating currents accompanying the santorini tsunami were at or above the threshold erosion velocity at the homogenite bearing sites in addition the near bottom pressure pulse under the tsunami at the homogenite bearing sites was sufficient to cause liquefaction of sediments neither mechanism was adequate to cause sediment transport or slope failure at the homogenite free sites

sedimentary features of seismoturbidites triggered by the 1983 and older historical earthquakes in the eastern margin of the japan sea abstract both mass failure deposits and turbidites are widely distributed in the epicentral area of the 1983 earthquake mw 7 9 in the eastern margin of the japan sea this basin is semi enclosed with no active conduits for the entrance of coarse detrital sediments seismic reflection surveys and sediment cores reveal that mass failure deposits which are distributed on the continental slopes merge into turbidites in the basin plain hence the mass wasting process is a major transportation process in this region one gravity core gh93 816 was recovered from the southeastern margin of the japan basin close to the epicentral area of the 1983 japan sea earthquake sedimentological results show that five turbidite beds are intercalated in the top 68 cm of the column occurrence of the b tm tephra at the depth of 68 71 cm indicates that these turbidite beds were developed during the last 1000 years the high 137cs concentration in the top 20 cm of the core implies that the uppermost turbidite bed was deposited after 1954 based on these age limits for the top and the bottom of the studied interval we estimate the recurrence intervals of turbidites as 160 330 years we suggest that these turbidites were generated by submarine slides which were triggered by the 1983 and older historical earthquakes in this region these seismoturbidites are characterized by amalgamated beds irregular structure sequences grain size breaks fluctuations abrupt changes in composition within bed and variable composition among beds from these features we infer that deposition resulted from a series of turbidity currents associated with multiple or line sources for example multiple shallow slides that were regionally initiated by the same earthquake the sedimentary features described herein may be useful as criteria for identifying modern seismoturbidites in other settings as well as seismoturbidites in the geologic record however further study is needed for the distinction of this type of turbidites from other types e g tempestites reflected turbidites

on the cause of the 1908 messina tsunami southern italy 1 a century after the catastrophic event the sources of the 1908 messina southern italy earthquake and tsunami which caused at least 60 000 deaths remain uncertain through a simple backward ray tracing method we convert the tsunami travel time data reported in a 100 years old paper into distances and find that the sources of the earthquake and tsunami are different overturning a long held assumption reconsideration of the available tsunami bathymetric seismic and seismological data indicates that the tsunami was generated by an underwater landslide

paleoseismicity of the cascadia subduction zone evidence from turbidites off the oregon washington margin cores from cascadia deep sea channel contain sequences of turbidites that can be correlated and dated by the first occurrence of volcanic glass from the mount mazama eruption 6845 50 radiocarbon yrbp turbidity currents from the tributaries appear to have occurred synchronously to form single deposits in the main channel there being only 13 turbidite deposits in the lower main channel since the mazama eruption instead of the twice as many expected if the tributaries had behaved independently in addition to the cascadia channel 13 post mazama turbidites have been deposited in the astoria canyon and at two sites off cape blanco sample locations that span 580 km of the oregon washington margin pelagic intervals deposited between the turbidites suggest that in each place the turbidity currents occurred fairly regularly every 590 170 years on average the best explanation of the spatial and temporal extent of the data is that the turbidity currents were triggered by 13 great earthquakes on the cascadia subduction zone the variability of turbidite timing is similar to that for great earthquake cycles the thickness of the topmost pelagic layer suggests the last event was 300 60 years ago from three places along the margin but this number may be a biased underestimate it is however consistent with the youngest sudden subsidence event on the washington coast the turbidite data demonstrate that the near term hazard of a great earthquake on the cascadia subduction zone is of the order of 2 10 in the next 50 years

sedimentary characteristics and depositional models of two types of homogenites in an eocene continental lake basin shulu sag eastern china abstract homogenites are homogeneous and structureless fine grained rocks they have been studied extensively in marine settings and are typically interpreted as being related to catastrophic events such as earthquakes however studies on lacustrine homogenite like rocks are limited new core data from the shulu sag in china reveal that thick massive calcilutites exist in the lower shahejie 3 formation which formed during the middle eocene rifting stage based on petrographic geochemical and mineralogical data these massive calcilutites are interpreted as homogenites and grouped into two types type a homogenite is composed of intrabasinal materials characterized by high calcite total organic carbon toc content and 13c value type a homogenite has two facies successions the first of which is characterized by homogeneous appearance capped by an erosional interface and the second is characterized by repeated massive laminated calcilutite successions type b homogenite contains abundant allochthonous materials displaying relatively high dolomite content and low calcite toc and 13c content type b homogenite represents the topmost finer portion of a graded megabed which includes from base to top grain supported carbonate conglomerates slumped deformed portions and debrites the whole unit can be considered as a megaturbidite earthquakes are the most reasonable triggers of homogenite formation in the shulu sag type a homogenites are thought to be derived by fluidification resuspension and decantation of lacustrine fines due to shock waves generated by an earthquake type b homogenites might be deposits of distal turbidity currents and turbid clouds transformed from other gravity flows the results of this study provide a better understanding of the formation of homogenites caused by earthquakes in a confined lacustrine basin

low sea level emplacement of a very large late pleistocene megaturbidite in the western mediterranean sea large volume turbidites termed megaturbidites or megabeds result from catastrophic slope failures and the associated downslope transport of enormous quantities of sediment from continental margins to the deep sea such large sediment failures can generate tsunamis and in terrains underlain by gas hydrates clathrates may be associated with the release of substantial amounts of the greenhouse gas methane it has been proposed that the megaturbidite events may be triggered by seismic activity or may result from gas hydrate release itself caused by a lowering of hydrostatic pressure on clathrates as a result of low sea level previous conclusions on the significance of sea level change however have been conditional because of the lack of absolute times of turbidite emplacement here we use accelerator mass spectrometry radiocarbon dating in five widely spaced cores to constrain the date of emplacement of a large volume 500 km3 bed in the balearic basin of the western mediterranean this turbidite is exceptional in its magnitude and represents the main sedimentation event in the balearic basin over the past 100 kyr our data provide an estimate of 22 000 calendar years before present for emplacement of the megabed a time when sea level stood at its lowest level during the last glacial maximum the coincidence of these dates is consistent with emplacement due to clathrate destabilization caused by low sea level although other triggering mechanisms such as seismic shock cannot be ruled out

preservation of elemental and isotopic source identification of sedimentary organic matter the amount and type of organic matter in the sediments of lakes and oceans contribute to their paleoenvironmental and paleoclimatological records only a small fraction of the initial aquatic organic matter survives destruction and alteration during sinking and sedimentation selective degradation modifies the character of the surviving small fraction of organic matter which becomes incorporated in bottom sediments organic matter alterations can continue to sub bottom depths of hundreds of meters corresponding to millions of years source and paleoenvironmental information nonetheless remains preserved in the molecular elemental and isotopic compositions of organic matter c n and 13c values of total organic matter in particular appear to retain paleoenvironmental information for multi myr time periods

late quaternary lacustrine paleo seismic archives in north western alps examples of earthquake origin assessment of sedimentary disturbances abstract the late quaternary sedimentary fills of several lakes of the north western alps are revealed to be possible paleo seismological archives in a moderately active seismo tectonic region the strongest historically reported events can be correlated with specific layers whose textures result from different processes i mass failures of sub aqueous slope deposits especially delta foresets evolving into hyperpycnal currents influenced by seiche effects and or multiple reflections on lake basin slopes ii in situ liquefaction and flowage and iii micro fracturing based on identification of the sedimentary signature of a well documented historical earthquake the paleoseismic interpretation can be extrapolated back to 16 000 yrs bp with a reconstruction of a time series and textural identification of slope failure related turbidites the most frequent earthquake signature the obtained time series are compatible with historical seismicity in terms of recurrence interval

earthquakes as a triggering mechanism for debris flows and turbidites on the calabrian ridge abstract debris flows and turbidites have been described in piston cores bottom photographs and side looking sonar records from basin floors amid the rugged irregular topography of the calabrian ridge a sediment transport process is inferred which began with a rotational slump on the steep basin wall subsequently transformed into a debris flow and turbid cloud such events occurred approximately every 1500 years because the debris flow turbidite deposits are correlative between basins some relatively widespread mechanism such as an earthquake is required to initiate the slope failure the estimated intensity of ground shaking as a result of historical earthquakes on the nearby calabrian and hellenic arcs has been used to develop a relationship between frequency of occurrence and intensity of ground shaking extrapolation of this relation to infrequent large magnitude events shows that the 1500 yr event is small enough to be geologically plausible but large enough to cause slope failure on basin walls it is possible that the historical record fortuitously contains one of these large magnitude long repeat time events which may have caused the most recent of the observed debris flows in 1903

extensional tectonics at the geysers geothermal area california comparisons between the yearly volume of steam withdrawn from the geysers california geothermal reservoir and the number of earthquakes indicate that most of the seismicity is induced to establish the inducing mechanism an estimate of the stress field orientation was calculated from inversion of 210 fault plane solutions below 1 km depth the geysers is undergoing uniaxial extension with the least principal stress 3 oriented near horizontal at approximately 105 azimuth the consistency between the local and regional stress fields indicates that the regional tectonic stress is much larger than the stresses induced locally through geothermal activities the stress data are equivocal as to whether earthquakes are induced due to conversion of aseismic to seismic slip or by increased shear stresses arising from reservoir contraction the observed tendency for downward growth of seismicity may arise from a preferential fracture orientation that is near vertical in conjunction with a stress state where the gradient of 1 exceeds that of 3 evidence of extension at the geysers and in the surrounding clear lake region indicates a direct relationship to the presence of the quaternary clear lake volcanics

sedimentary earthquake records in the izmit gulf sea of marmara turkey abstract sedimentary earthquake records of the last 2400 a including that of the devastating 17 august 1999 izmit earthquake mw 7 4 were studied in cores from the 210 m deep central karamursel basin of the izmit gulf in the eastern sea of marmara using laser grain size physical properties stable o and c isotopes and xrf core scanner analyses and dated by radionuclide and radiocarbon methods the earthquake records are represented by turbidite homogenite mass flow units thu that commonly contain a basal coarse layer a middle laminated silt layer and an overlying homogeneous mud layer the coarse basal part has a sharp and sometimes scoured lower boundary and includes multiple coarse sand silt layers or laminae showing normal size grading multiple coarse layers and occasional bi directional cross bedding suggest deposition from a bed load during water column oscillations or seiche effect the grain size characteristics of the overlaying laminated silt and the homogeneous mud units indicate deposition from weak oscillating currents and homogeneous suspension respectively high mn value just below the base of thus suggests diagenetic enrichment at oxic anoxic redox boundary before the mass flow event sharp decrease in mn with very low values within the thus suggests transient redox conditions following the mass flow variable geochemical compositions of the basal coarse layers indicate different sediment sources for different thus eight sedimentary earthquake records observed in the last 2400 a in the izmit gulf can be confidently correlated with the historical earthquakes of 1999 1509 ad ms 7 2 1296 ad i vii 865 ad i viii 740 ad i viii 268 ad i viii 358 ad i ix and 427 bc this gives an earthquake recurrence time of ca 300 a with the interval between consecutive events ranging from 90 to 695 a

sub decadal turbidite frequency during the early holocene eel fan offshore northern california remotely operated and autonomous underwater vehicle technologies were used to image and sample exceptional deep sea outcrops where an 100 m thick section of turbidite beds is exposed on the headwalls of two giant submarine scours on eel submarine fan offshore northern california usa these outcrops provide a rare opportunity to connect young deep sea turbidites with their feeder system 14 c measurements reveal that from 12 8 ka to 7 9 ka one turbidite was being emplaced on average every 7 yr this emplacement rate is two to three orders of magnitude higher than observed for turbidites elsewhere along the pacific margin of north america the turbidites contain abundant wood and shallow dwelling foraminifera demonstrating an efficient connection between the eel river source and the eel fan sink tur bidite recurrence intervals diminish fivefold to 36 yr from 7 9 ka onward reflecting sea level rise and re routing of eel river sediments

turbidite paleoseismology in the calabrian arc subduction complex ionian sea 1 the calabrian arc subduction system is part of the africa eurasia plate boundary is one of the most seismically active regions in the mediterranean sea and has been struck repeatedly by destructive historical earthquakes in this study we investigate the effects of historical earthquakes on abyssal marine sedimentation through the analysis of the turbidite record we collected gravity cores in tectonically controlled basins where the eastern mediterranean pelagic sequence is interbedded with resedimented units textural micropaleontological geochemical and mineralogical signatures reveal three turbidite events in the last millennium we dated the turbidite sequences from two different cores using different radiometric methods whereas the average time interval between successive turbidite beds was estimated from pelagic sediment thickness and sedimentation rates chronologies were refined through age modeling that provided age ranges 2 of each turbidite bed the results suggest that turbidite emplacement was triggered by three historical earthquakes recorded in the area i e the 1908 1693 and 1169 events their magnitude epicentral location and associated tsunamis support causative faults located in the ionian sea the source for all the turbidites as inferred from their mineralogy is the metamorphic basement outcropping in southern calabria and or northeastern sicily turbidite composition and cable breaks for the 1908 event have been used to infer likely traveling paths and seismogenic faults in the subduction system our findings suggest that ionian sea turbidites represent more than 80 of sedimentation and may be seabed archives of paleo earthquakes capable of reconstructing seismicity back in time during several earthquake cycles

a depositional model for seismo turbidites in confined basins based on ionian sea deposits abstract this study investigates ionian sea seismo turbidite st deposits that we interpret to be triggered by major historic earthquakes and tsunamis in the calabrian arc st beds can be correlated with the ad 1908 mw 7 24 messina ad 1693 mw 7 41 catania and ad 1169 mw 6 6 eastern sicily earthquakes while two previously unknown turbidites might have been generated by the ad 1818 mw 6 23 catania and ad 1542 mw 6 77 siracusa earthquakes textural micropaleontological geochemical and mineralogical signatures of sts reveal cyclic patterns of sta stb stc and std sedimentary units for each earthquake with an associated tsunami the sta unit contains multiple st stacks with different mineralogy geochemistry foraminiferal assemblages and sedimentary structures that are deposited from synchronous multiple slope failures and turbidity currents the stb homogenite graded mud unit overlying the sta unit is deposited by the waning flows of the multiple turbidity currents that are trapped in the ionian sea confined basin the stc laminated and marine sourced unit results from seiching of the confined water mass that appears to be generated by earthquake ruptures combined with tsunami waves the std unit is a tsunamite cap deposited by the slow settling suspension cloud created by tsunami wave backwash erosion of the shoreline and continental shelf this tsunami process interpretation is based on the textural gradation of the upper unit and a more continental source of the tsunamite cap which includes c n 10 and the presence of inner shelf foraminifera with a lack of abyssal species this interpretation is in agreement with the lack of a tsunamite cap for the turbidite likely linked to the ad 1542 historic earthquake that is not associated with a tsunami the new sedimentologic criteria identifies the final seiche and tsunamite cap deposits of sts and provides a model that can now be tested in other locations to better understand the different depositional processes of seismo turbidites in confined basins

postglacial after 18 ka deep sea sedimentation along the hikurangi subduction margin new zealand characterisation timing and origin of turbidites recent sedimentation along the hikurangi subduction margin off northeastern new zealand is investigated using a series of piston cores collected between 2003 and 2008 the active hikurangi margin lies along the pacific australia subduction plate boundary and contains a diverse range of geomorphologic settings slope basin stratigraphy is thick and complex resulting from sustained high rates of sedimentation from adjacent muddy rivers throughout the quaternary turbidites deposited since c 18 ka in the poverty ruatoria and matakaoa re entrants are central to this study in that they provide a detailed record of the past climatic conditions and tectonic activity here alternating hemipelagite turbidite debrite and tephra layers reflect distinctive depositional modes of marine sedimentation turbidity current debris flow and volcanic eruption respectively turbidites dominate the record ranging in lithofacies from muddy to sandy turbidites and include some basal reverse graded turbidites inferred to be derived from hyperpycnal flows stacked turbidites are common and indicate multiple gravity flows over short time periods the chronology of turbidites is determined by collating an extremely dense set of radiocarbon ages and dated tephra which facilitate sedimentation rate calculation and identification of the origin of turbidites sedimentation rates range from 285 cm ka during late glacial time 18 5 17 ka to 15 to 109 cm ka during postglacial time 17 0 ka turbidite deposition is controlled by 1 the emplacement of slope avalanches reorganising sediment pathways 2 the postglacial marine transgression leading to a five fold reduction in sediment supply to the slope due to disconnection of river mouths from the shelf edge and 3 the holocene pleistocene boundary climate warming resulting in a drastic decrease in the average turbidite grain size flood induced turbidites are scarce nine hyperpycnites are recognised since 18 ka and the youngest is correlated to the largest enso related storm event recorded onland lake tutira other turbidites contain a benthic foraminiferal assemblage which is strictly reworked from the upper slope and which relates to large earthquakes over the last c 7 ka they yield a shorter return time 270 430 years than the published coastal records for large earthquakes c 670 years but the offshore record is likely to be more complete the deep sea sedimentation along the new zealand active margin illustrates the complex interaction of tectonic and climate in turbidite generation climate warming and glacio eustatic fluctuations are well recorded at a millennial timescale 18 ka while tectonic deformation and earthquakes appear predominant in fostering turbidite production at a centennial timescale 270 430 years

seismoturbidites a new group of resedimented deposits abstract turbidite beds of exceptionally large volume and areal extent occur in both modern and ancient deep water basins these beds which may reach individual volumes in excess of 100 km3 are apparently the product of catastrophic gravity flows triggered by earthquakes along the margins of highly mobile basins most commonly elongate flysch troughs turbidite beds produced by these catastrophic events are generally characterized by very distinctive geometry internal structures and composition and are termed herein seismoturbidites characteristically these sediments lack time persistent features of deep sea fans such as channels and lobes seismoturbidites may occur as scattered intercalations diluted within otherwise normal turbidite sequences thus forming generally excellent markers for basin wide correlations or as closely spaced repetitive units comprising the bulk of the sedimentary fill of certain flysch basins in both cases they may offer a tremendously useful tool for a better understanding of the distribution of paleoseismic zones in time and space

offshore sedimentary effects of the 12 january 2010 haiti earthquake although the 12 january 2010 haiti earthquake was one of the deadliest earthquakes in history it left no clear geological evidence of rupture on land as a tectonic event the earthquake was complex even the faults involved remain unclear using geophysical and coring data we document direct evidence of the sedimentation generated by the catastrophic 12 january 2010 earthquake offshore these studies document submarine paleoseismology methods that can be used for assessing seismic risk in this and other tectonic settings such as the california san andreas fault where deeper buried blind thrusts may exist shaking by the 12 january main shock triggered sediment failures and turbidity currents from coastal sources to deep water sinks an 0 05 km 3 turbidite was deposited in the canal du sud basin 1750 m water depth over 50 km 2 almost 2 months after the main shock a 600 m thick sediment plume was still present in the lowermost water column at this location the turbidite was time correlated to the 12 january earthquake by the excess 234 th in the sediments with a half life of 24 days its presence documents an infl ux of terrigenous sediment mixing with marine sources derived from the basin slopes this turbidite and older ones observed beneath it displays complex cross bedded and fi ning upward stratigraphy indicative of long waves and seiche oscillations that are consistent with locally reported tsunamis this 12 january sedimentary record highlights the potential for submarine paleoseismology to unravel the seismic history of continental transform boundaries such as the enriquillo plantain garden fault in the dominican republic haiti and jamaica as well as other tectonic settings where no clear land based evidence for a rupture exists

reactivated lithospheric scale discontinuities localize dynamic uplift of the moroccan atlas mountains comment the atlas mountains of morocco have received considerable attention in the past decade regarding the lithospheric structure and the uplift mechanisms of this structurally simple mountain belt miller and becker 2014 have recently added to the discussion with new results from receiver functions and shear wave splitting analysis these results confirm the mantle upwelling hypothesis for the atlas uplift that was postulated 10 years ago and we now see highlighted in several forums the relationship between modest tectonic shortening and high topography in the atlas was first addressed by teixell et al 2003 they concluded that crustal thickness is insufficient to account for the observed elevations and proposed a mantle driven upwelling component of uplift supported by low seismic velocities in the atlas mantle reported already by seber et al 1996 subsequent efforts focused on modeling of gravity the geoid and topography that indicated a prominent lithospheric thinning placing the lithosphere asthenosphere boundary lab at 70 90 km beneath the atlas mountains e g teixell et al 2005 zeyen et al 2005 missenard et al 2006 fullea et al 2010 new contributions on the basis of active and passive seismology partly under the picasso project frame are on their way e g bezada et al 2013 carbonell et al 2013 palomeras et al 2013 miller and becker 2014 miller and becker present a receiver functions profile that also shows a thinned crust and lithosphere beneath the atlas mountains however the thinned domain is bounded by abrupt steps coinciding with the location of the south atlas thrust front the authors propose offsets of 9 km of the moho and 26 km of the lab across the boundary thrust fault at errachidia miller and becker 2014 their figure 2 arguing for the important role of lithosphericscale discontinuities in the atlas mountain building as for the crust this is intriguing because early refraction studies by wigger et al 1992 and a more dense wide angle survey by carbonell et al 2013 failed to detect a crustal step in this position but especially because there is ample evidence that the south atlas fault is a low angle thrust zone saint bezar et al 1988 teixell et al 2003 moreover miller and becker imply that the same fault discontinuity goes down to offset the lab which means that the south atlas thrust projects vertically to a depth of 90 km this has doubtful geological sense even assuming that the present day thrusts derive from the inversion of earlier extensional faults those would also have a dip and at a depth of 90 km they would be off the vertical projection of the fault surface exposure miller and becker recognize that previous authors document shallowly dipping thrust faults from outcrop and seismic reflection studies but they do not further discuss this issue we are left questioning whether there is an enigmatic geological feature in the atlas that escapes our understanding or an issue of seismic data resolution miller and becker compare the detected position of the lab with a modeled position on the basis of the residual topography and on the assumption of isostasy resulting in a large discrepancy as the modeled lab is even shallower than the actual base of the crust this indicates a strong contribution of dynamic topography due to active mantle upwelling we do not question the validity of dynamic topography for the atlas but we miss a discussion of the earlier potential field models which on the basis of isostatic equilibrium fitted the residual topography and the geoid with a greater lithospheric thickness which would be in accord with the new receiver function results see references above finally we wish to conclude with a formal comment on the referencing to earlier work in the atlas miller and becker report a small orogenic shortening 15 25 inconsistent with airy isostatic support and cite four papers but none of them resulting in these small values of shortening nor do they address relationships between shortening and topography fullea et al 2010 are not the primary reference for the distribution of quaternary basalts frizon de lamotte et al 2009 do not provide cross sections to demonstrate shallowly dipping thrust faults sebrier et al 2006 do not provide regional tomography models and beauchamp et al 1999 do not suggest a mantle thermal anomaly as the source of volcanism in the middle atlas although these citations by miller and becker do not alter the main point of their paper we wish to raise a word of caution for the persistence of incorrect citations

storm induced sediment gravity flows at the head of the eel submarine canyon northern california margin 1 as part of the strataform program a bottom boundary layer bbl tripod was deployed at 120 m depth in the northern thalweg of the eel canyon during winter 2000 increases of the near bottom suspended sediment concentrations ssc recorded at the canyon head were not directly related to the eel river discharge but were clearly linked to the occurrence of storms bbl measurements revealed that during intensifications of the wave orbital velocity sediment transport at the head of the canyon occurred as sediment gravity flows directed down canyon observational evidence for near bed sediment gravity flow transport included an increase toward the bed of the down canyon component of wave averaged velocity and high estimated ssc at higher sampling frequencies 1 hz the current components during these events fluctuated at the same periodicity as the pressure reflecting a clear influence of the surface wave activity on the generation and maintenance of the sediment gravity flows the origin of such flows is not related to the formation of fluid muds on the shelf or to intense wave current sediment resuspension around the canyon head region rather liquefaction of sediment deposited at the head of the canyon induced by wave load excess pore water pressures during storms combined with elevated slopes around the canyon head appear to be the mechanisms initiating sediment transport the resulting fluidized sediment layer can easily be eroded entrained into the water column and transported down canyon as a sediment gravity flow results from this study reveal that storm induced sediment gravity flows occur periodically in the eel canyon head and suggest that this kind of sediment transport process can occur in other submarine canyons more frequently than previously expected

analysis of tropical like cyclones over the mediterranean sea through a combined modeling and satellite approach 1 several mediterranean vortices with characteristics similar to tropical cyclones are analyzed by means of numerical simulations satellite products and lightning data numerical analysis suggests that the broad tropical like cyclone category includes in reality a set of different cyclones ranging from very small and weak vortices to larger and stronger cyclones one case displays a much longer persistence of tropical features than the other events the analysis of the tracks identifies two preferred areas of occurrence the ionian sea and the balearic islands the satellite analysis of cloud top height and retrieved rainfall indicates that the stage characterized by the most intense convective activity and rainfall anticipates the mature phase when the cyclone is more intense and characterized by tropical features during which convection is shallower and rainfall weaker this result is confirmed by a preliminary analysis of the lightning activity

gravity driven deposits in an active margin ionian sea over the last 330 000 years in the ionian sea the subduction of the nubia plate underneath the eurasia plate leads to an important sediment remobilisation on the calabrian arc and the mediterranean ridge these events are often associated with earthquakes and tsunamis in this study we analyse gravity driven deposits in order to establish their recurrence time on the calabrian arc and the western mediterranean ridge four gravity cores collected on ridges and slope basins of accretionary prisms record turbidites megaturbidites slumping and micro faults over the last 330 000 years these turbidites were dated by correlation with a hemipelagic core with a multi proxy approach radiometric dating 18o b colour curve sapropels and tephrochronology the origin of the gravity driven deposits was studied with a sedimentary approach grain size lithology thin section geochemistry of volcanic glass the results suggest three periods of presence absence of gravity driven deposits a first on the western lobe of the calabrian arc between 330 000 and 250 000 years a second between 120 000 years and present day on the eastern lobe of the calabrian arc and over the last 60 000 years on the western lobe and a third on the mediterranean ridge over the last 37 000 years return times for gravity driven deposits are around 1000 years during the most important record periods the turbidite activity also highlights the presence of volcaniclastic turbidites that seems to be link to the etna changing morphology over the last 320 000 years

morphotectonics and late quaternary seismic stratigraphy of lake garda northern italy abstract lake garda the largest lake in italy at the southern front of the central alps provides a unique opportunity to reconstruct quaternary geological processes related to the interplay between deglaciation driven sedimentation and tectonic activity in fact the topographic depression presently occupied by the lake was site of a major glacial tongue during the lgm and is located close to the epicentral areas of two of the largest magnitude historical earthquakes recorded in the po plain the verona jan 13 1117 and brescia dec 25 1222 seismic events characterized by io ix x mcs respectively despite this peculiarity geophysical surveys of the lake are scant we present results of a waterborne geophysical survey of lake garda leading to the acquisition of a densely spaced grid of high resolution seismic reflection profiles which image the lake floor and uppermost sedimentary sequence these data enabled us to compile thematic maps which provide insights on active geologic processes in different sectors of the basin we focused our work on a prominent seismic reflector h1 correlated over the entire lake surface to estimate the sediment deposition rate at the scale of the last 10 ka and to evaluate the variability of seismic facies and geological processes in different sectors of the basin based on available stratigraphic data we discuss whether h1 could mark the diachronic glacial fluvio glacial transition after the last glacial maximum when the ice tongues south of the alps started to melt and collapse we observed that sediments of the southern lake garda are affected by incipient tectonic deformation and two major seismoturbidite homogenite beds might represent over 50 of the holocene sedimentary record in the lake depocenter making the study of the lake garda stratigraphy an interesting tool for assessing earthquake hazards at the southern front of the alpine chain

mass transport deposits and geo hazard assessment in the bradano foredeep southern apennines ionian sea abstract seafloor bathymetry combined with multi scale seismic reflection profiles were used to describe the morphostructural setting of the bradano foredeep gulf of taranto northern ionian sea where a submerged portion of the southern apennines is facing the apulia platform in the calabrian arc convergent margin in this complex area marine geophysical data highlight the presence of two mega slide deposits at the shelf slope transition which are most likely the largest ever described in the region these slid masses named the bradano basento megaslide bbms and bradano basento megaslide 1 bbms1 form a mass transport deposit complex mtdc affecting and eroding the topmost portion of the outer apennines deformation front and the apulian foreland ramp it was emplaced in late pleistocene times inside the narrow about 10 km wide bradano foredeep basin a plio pleistocene submarine trough developing at the chain front the youngest of these deposits bbms1 likely predates the last glacial maximum location of the mtdc within the subduction complex suggests that active tectonics and seismic shaking might represent the main triggering mechanisms for gravitative instability in this area although gravitational tectonics and sediment creeping mechanisms cannot be excluded on the other hand size and distribution of the mtdc in the sedimentary record of the bradano foredeep suggest the need of re evaluating the potential for large earthquakes tsunamis and more in general geological hazard related to submarine sliding masses along the coast of this highly populated area

topography of the calabria subduction zone southern italy clues for the origin of mt etna 1 calabria represents an ideal site to analyze the topography of a subduction zone as it is located on top of a narrow active wadati benioff zone and shows evidence of rapid uplift we analyzed a pattern of surface deformation using elevation data with different filters and showed the existence of a long wavelength 100 km relatively positive topographic signal at the slab edges the elevation of mis 5 5 stage marine terraces supports this pattern although the record is incomplete and partly masked by the variable denudation rate we performed structural analyses along the major active or recently reactivated normal faults showing that the extensional direction varies along the calabrian arc and laterally switches from arc normal within the active portion of the slab to arc oblique or even arc parallel along the northern and southern slab edges this surface deformation pattern was compared with a recent high resolution p wave tomographic model showing that the high seismic velocity anomaly is continuous only within the active wadati benioff zone whereas the northern and southwestern sides are marked by low velocity anomalies suggesting that large scale topographic bulges volcanism and uplift could have been produced by mantle upwelling we present numerical simulations to visualize the three dimensional mantle circulation around a narrow retreating slab ideally similar to the one presently subducting beneath calabria we emphasize that mantle upwelling and surface deformation are expected at the edges of the slab where return flows may eventually drive decompression melting and the mount etna volcanism

mass movement induced tsunami hazard on perialpine lake lucerne switzerland scenarios and numerical experiments previous studies of the sediments of lake lucerne have shown that massive subaqueous mass movements affecting unconsolidated sediments on lateral slopes are a common process in this lake and in view of historical reports describing damaging waves on the lake it was suggested that tsunamis generated by mass movements represent a considerable natural hazard on the lakeshores newly performed numerical simulations combining two dimensional depth averaged models for mass movement propagation and for tsunami generation propagation and inundation reproduce a number of reported tsunami effects four analysed mass movement scenarios three based on documented slope failures involving volumes of 5 5 to 20 8 106 m3 show peak wave heights of several metres and maximum runup of 6 to 10 m in the directly affected basins while effects in neighbouring basins are less drastic the tsunamis cause large scale inundation over distances of several hundred metres on flat alluvial plains close to the mass movement source areas basins at the ends of the lake experience regular water level oscillations with characteristic periods of several minutes the vulnerability of potentially affected areas has increased dramatically since the times of the damaging historical events recommending a thorough evaluation of the hazard

geophysical characterization of the northwest geysers geothermal field california abstract the clear lake volcanic field in northern california is the youngest and northern most part of a long lived volcanic system that has produced recent 10 ka eruptions adjacent to the clear lake volcanic field is the world s largest energy producing geothermal field the geysers the hottest part of the geyser s geothermal field is in the northwest where temperatures reach 400 c at 3 km depth low permeability high thermal gradients and low steam saturation prescribed development of an enhanced geothermal system egs in the northwest geysers to increase energy producing capacity though the northwest geysers is known to be the hottest part of the field geophysical methods have failed to adequately image any inferred heat source this project aims to image the heat source of the northwest geysers using newly collected gravity and magnetotelluric mt measurements gravity data were jointly modeled with existing magnetic data along a two dimensional profile aligned with an existing geologic cross section the key feature of the potential field model is a low density low susceptibility body at 5 km depth bmsl under the egs mt data were modeled in three dimensions to characterize subsurface resistivity structure where the upper 3 km of the resistivity model agrees well with existing data lithologic and steam saturation are estimated from modeled resistivity values using existing geophysical data below 3 km depth bmsl the resistivity model images a possible young intrusion under the egs a possible zone of partial melt

lacustrine turbidites as a tool for quantitative earthquake reconstruction new evidence for a variable rupture mode in south central chile understanding the long term earthquake recurrence pattern at subduction zones requires continuous paleoseismic records with excellent temporal and spatial resolution and stable threshold conditions south central chilean lakes are typically characterized by laminated sediments providing a quasi annual resolution our sedimentary data show that lacustrine turbidite sequences accurately reflect the historical record of large interplate earthquakes among others the 2010 and 1960 events furthermore we found that a turbidite s spatial extent and thickness are a function of the local seismic intensity and can be used for reconstructing paleo intensities consequently our multilake turbidite record aids in pinpointing magnitudes rupture locations and extent of past subduction earthquakes in south central chile comparison of the lacustrine turbidite records with historical reports a paleotsunami subsidence record and a marine megaturbidite record demonstrates that the valdivia segment is characterized by a variable rupture mode over the last 900 years including i full ruptures mw 9 5 1960 1575 1319 9 1127 44 ii ruptures covering half of the valdivia segment mw 9 1837 and iii partial ruptures of much smaller coseismic slip and extent mw 7 5 8 1737 1466 4 also distant or smaller local earthquakes can leave a specific sedimentary imprint which may resolve subtle differences in seismic intensity values for instance the 2010 event at the maule segment produced higher seismic intensities toward southeastern localities compared to previous megathrust ruptures of similar size and extent near concepci n

late holocene rupture of the northern san andreas fault and possible stress linkage to the cascadia subduction zone we relate the late holocene northern san andreas fault nsaf paleo seismic history developed using marine sediment cores along the northern california continental margin to a similar dataset of cores collected along the cascadia margin including channels from barclay canyon off vancouver island to just north of mon terey bay stratigraphic correlation and evidence of synchronous triggering imply earthquake origin and both temporal records are compatible with onshore paleoseis mic data in order to make comparisons between the temporal earthquake records from the nsaf and cascadia we refine correlations of southern cascadia great earth quakes including the land paleoseismic record along the nsaf during the last 2800 yr 15 turbidites including one likely from the great 1906 earthquake establish an average repeat time of 200 yr similar to the onshore value of 240 yr the combined land and marine paleoseismic record from the southern cascadia subduction zone includes a similar number of events during the same period while the average recurrence interval for full margin cascadia events is 520 yr the southern cascadia margin has a repeat time of 220 yr similar to that of the nsaf thirteen of the 15 nsaf events were preceded by cascadia events by 0 80 yr averaging 25 45 yr as compared to 80 400 yr by which cascadia events follow the nsaf based on the temporal association we model the coseismic and cumulative post seismic deformation from great cascadia megathrust events and compute related stress changes along the nsaf in order to test the possibility that cascadia earth quakes triggered the penultimate and perhaps other nsaf events the coulomb fail ure stress cfs resulting from viscous deformation related to a cascadia earthquake over 60 yr does not contribute significantly to the total cfs on the nsaf however the coseismic deformation increases cfs on the northern san andreas fault nsaf b y up to about 9 bars offshore of point delgada most likely enough to trigger that fault to fail in north to south propagating ruptures

late quaternary co seismic sedimentation in the sea of marmara s deep basins the deep northern part of the sea of marmara northwestern turkey is composed of several aligned actively subsiding basins which are the direct structural and morphological expression of the north anatolian fault s northern branch the last 20 kyr of their sedimentary fill lacustrine before 12 kyr bp have been investigated through giant piston coring onboard r v marion dufresne marmacore cruise 2001 and chirp subbottom profiler onboard r v atalante during marmarascarps cruise 2002 especially during the lacustrine stage the infilling of the deep basins tekirda central kumburgaz and cinarcic basins up to 1250 m depth was dominated by turbidites with coarse mixed siliciclastic and bioclastic basal part intercalated in hemipelagic type finegrained calcareous and slightly siliceous clays often especially in the thickest ones the turbidites show strong segregation and a sharp boundary between coarse part and suspendedload part in the central basin 8 m of a unique sedimentary event include a 5 to 8m thick homogenite well imaged on seismic profiles the latter is interpreted as related to a major possibly triggered tsunami effect as described in the eastern mediterranean by kastens and cita 1981 in the marine holocene upper part of the sedimentary fill repeated to and from structures affecting silt or fine sand are evidencing seiche like effects and thus earthquake triggering detailed correlations between two deep coring sites 1250 and 1200 m indicate more than 100 overthickening in the deepest one this implies specific processes of distribution of terrigenous input by dense hyperpycnal currents high kinetic energy seiche effect complex reflections on steep slopes the peculiar sedimentary infilling of the sea of marmara s central basin and by extrapolation of the whole set is tentatively interpreted as a direct consequence of the strong seismic activity the imprint of the latter is more obvious prior to the base of the holocene as environmental conditions favoured marginal accumulation especially on the southern shelf of large amounts of erosion products available for mass wasting

did the a d 365 crete earthquake tsunami trigger synchronous giant turbidity currents in the mediterranean sea in the ionian sea one of the most seismically active regions in the mediterranean subduction is commonly associated with uplift of coastal mountains enhanced erosion and seismic activity along the calabrian arc and hellenic arc thus potentially resulting in repetitive mass failures some of the turbidites observed in the deep basins are thick and prominent on seismic records because of the acoustic transparency of their upper structureless mud layer our high resolution study of the most recent of these megabeds the homogenite augias turbidite hat provides key proxies to identify pelagic sediments deposited following the catastrophic causative event radiometric dating in an area 150 000 km2 indicates that the different mediterranean so called homogenite deposits are in fact synchronous and were deposited during a single basin wide event within the time window a d 364 415 unlike interpretations that relate this turbidite to different triggering events including the santorini caldera collapse the turbidite can be traced back to a large tsunami sourced from the a d 365 crete megathrust earthquake correlation of the single event hat over a wide area of the mediterranean from the northern ionian sea to the mediterranean ridge and the anoxic tyro basin south of crete suggests that the a d 365 crete earthquake and tsunami must have produced devastating effects including widespread massive sediment remobilization in the eastern mediterranean sea

signatures of slope failures and river delta collapses in a perialpine lake lake lucerne switzerland historical reports from the 17th century document two destructive tsunamis with runups exceeding 5 m affecting proximal basins of lake lucerne switzerland one event in ad 1601 is coeval with a strong nearby earthquake mw ca 5 9 which caused extensive slope failures in many parts of the lake the second event in ad 1687 is associated with an apparently spontaneous partial collapse of the muota river delta this study combines high resolution bathymetry reflection seismic and lithological data in order to document the sedimentary and morphological signatures of the two subaqueous mass movements that probably generated the observed tsunamis such mass movements are significant as a common sedimentation process and as natural hazard in fjord type lakes and similar environments the deposits covering large parts of the basins with thicknesses reaching 10 m consist of two subunits a lower massflow deposit contains variably deformed sediments from the source areas its emplacement affected pre existing sediments incorporating thin sediment slices into the deposit and increasing its volume deep reaching deformation near this is an accepted article that has been peer reviewed and approved for publication in the sedimentology but has yet to undergo copy editing and proof correction

high resolution morpho bathymetric imaging of the messina strait southern italy new insights on the 1908 earthquake and tsunami the 28 december 1908 reggio calabria and messina earthquake named after the two most damaged cities on the coasts of messina strait was one of the strongest mw 7 1 ever to occur in italy and was also followed by a tsunami that severely impacted the coasts of the strait although there is general agreement that its epicentre is located offshore in the messina strait the source fault has never been detected a century long question is therefore pending on the source of both the 1908 earthquake and tsunami within the ongoing debate on this subject little attention has been given so far to morphological insights from high resolution bathymetric multibeam data particularly as regarding the evidence of faults affecting the seafloor and the question of whether a submarine landslide may had been the cause of the tsunami we aim to address this issue by presenting the results of a morpho bathymetric study in the messina strait and surroundings investigated by means of high resolution swath bathymetry the primary morpho structural feature in this area is the axial channel of the messina canyon towards which flow several tributary canyons that incise the steep continental slope on the calabrian and sicilian margins these canyons carve deeply into a very narrow almost lacking continental shelf and merge laterally forming a continuous erosional margin rimming the messina strait this giant composite canyon environment is the locus of intense erosional and depositional processes that superimpose on active tectonic deformation resulting in a complex geomorphology that hinders the distinction between tectonic and sedimentary features seafloor ruptures that may be linked to fault systems compatible with the source of the 1908 earthquake and tsunami could not be identified based from our morpho bathymetric analysis however we provide evidence of several geomorphic features indicative of tectonic deformation in the messina strait define the presence and distribution of submarine landslides and evaluate their possible role as tsunami sources

near synchronous and delayed initiation of long run out submarine sediment flows from a record breaking river flood offshore taiwan subsea fiber optic telecommunication cables can break under fast sediment flows that travel 100s of kilometers through the deep ocean in response to earthquakes and submarine landslides similar flows are inferred to form from major river floods whose sediment laden waters plunge and travel along the seabed however the complex initiation of flood related flows and their hazard potential have not been observed until now here we use cable fault data from the gaoping canyon manila trench off taiwan to show that a major river flood formed during typhoon morakot 2009 generated two long run out destructive sediment flows one during peak flood and the other 3 days later the latter flow was more damaging with speeds and run out similar to that of landslide triggered turbidity currents formed in the same catchment if the second flow was due to remobilized canyon sediment it occurred during low earthquake mw 2 0 activity suggesting other triggering mechanisms

are repetitive slumpings during sapropel s1 related to paleo earthquakes abstract the recurrence of mass flow units within sapropel s1 an organic carbon rich lower holocene marker bed in the eastern mediterranean sea was used to study the interplay between earthquakes and sedimentation along the seismically active calabrian arc ionian sea nine turbidite beds interrupt anoxic conditions during the deposition of sapropel s1 each of these turbidites is associated with sharp grain size and geochemical elemental anomalies high al and si low ca and coarse grained basal part marked by zr peaks and with displaced foraminiferal species from different bathymetric ranges we used these proxies to identify turbidite beds also above and below the sapropel where turbidite signature is less clear due to the absence of major color changes turbidite structure and composition as well as comparison with historical seismoturbidites suggest a seismic triggering for such mass flow events the peculiar color well known composition geochemistry and age of sapropel s1 make this unit a key bed within which turbidites may be considered a sort of sedimentary bar code recording high energy events within the background pelagic sedimentation deciphering this code will reconstruct paleo seismicity in this well defined stratigraphic interval the pelagic units bracketing turbidite beds were radiometrically dated and the age of the sapropel s1 deduced through age modeling is between 6 0 and 10 2 kyr cal bp the emplacement age of each turbidite was estimated considering the average time interval between successive turbidite beds from pelagic sediment thickness and sedimentation rate subsequently these ages were further refined through age modeling in this way we compiled a catalogue of mass flow events during sapropel s1 deposition a time span long enough to include several earthquake cycles and allow reliable seismic and tsunami hazard assessment in this area

rupture lengths and temporal history of significant earthquakes on the offshore and north coast segments of the northern san andreas fault based on turbidite stratigraphy piston gravity and jumbo kasten cores were collected from channel and canyon systems draining the northern california continentalmargintoinvestigatetherecordofperiodicholoceneturbiditesforpossibleconnectiontolargemagnitudeearthquakeson the adjacent northern san andreas fault poorly known channel systems were mapped with multibeam sonar to define pathways and channel confluences cores sampled all major and many minor channel systems extending from cape mendocino to just north of monterey bay sampling both along and across channels was done and particular attention was paid to channel confluences as these areas afford opportunities to test for synchronous triggering of turbidity currents while at sea all cores were scanned using a geotek multisensor core logger mscl which collects high resolution photography p wave velocity gamma ray density and magnetic susceptibility data from the unsplit cores lithology was logged visually and cores were later imaged with x radiography we use 14 c ages relative dating tests at channel confluences and stratigraphic correlation using physical properties to determine

can turbidites be used to reconstruct a paleoearthquake record for the central sumatran margin turbidite paleoseismology aims to use submarine gravity flow deposits turbidites as proxies for large earthquakes a critical assumption being that large earthquakes generate turbidity currents synchronously over a wide area we test whether all large earthquakes generate synchronous turbidites and if not investigate where large earthquakes fail to do this the sumatran margin has a well characterized earthquake record spanning the past 200 yr including the large magnitude earthquakes in 2004 mw 9 1 and 2005 mw 8 7 sediment cores collected from the central sumatran margin in 2009 reveal that surprisingly few turbidites were emplaced in the past 100 150 yr and those that were deposited are not widespread importantly slope basin deposits preserve no evidence of turbidites that correlate with the earthquakes in 2004 and 2005 although recent flow deposits are seen in the trench adjacent slope basins and adjacent pairs of slope basin and trench sites commonly have different sedimentary records and cannot be correlated these core sites from the central sumatran margin do not support the assumption that all large earthquakes generate the widespread synchronous turbidites necessary for reconstructing an accurate paleoearthquake record

computer axial tomography in geosciences an overview abstract computer axial tomography cat is one of the most adequate non destructive techniques for the investigation of the internal structure of a large category of objects this method based on the attenuation of x or gamma ray generates digital images which map the numerical values of the linear attenuation coefficient of a section or of the entire volume of the investigated sample depending on the energy of the utilized radiation as well as on the effective atomic number of the sample cat can furnish with a spatial resolution of 0 01 0 5 mm quantitative as well as qualitative information concerning local density or chemical composition of the sample in geosciences cat has been successfully applied to the investigation of bulk density moisture content or macroporosity of the soil soil plant water system oil sand or shales small scale heterogeneities in siltstone or sandstone diamonds in kimberlite mineralization layers in manganese nodules local structure of marine sediments or coal composition the method has also been used for the investigation of the rock mechanical properties rock permeability fracture network two or three phase flow or residual oil distribution in carbonate cores a review of the actual applications of cat in soil science sedimentology coal geology as well as rock mechanics is presented all these applications reveal the great potential of cat in geoscience investigations

source discriminants for near field tsunamis summary we present numerical simulations of tsunami run up in the near field for a data set of 72 models of sources involving both seismic dislocations and landslides by varying one by one the parameters describing the source and the receiving beach we are able to separate their individual influence on the amplitude and distribution of run up which we characterize by forming several dimensionless parameters principally the ratio i 2 of its maximum amplitude to its lateral extent along the beach we find that i 2 remains less than 10 4 for seismic dislocation sources but is greater than this threshold for all physically realistic models of underwater landslides thus it can be used as a discriminant for the nature of the source of a near field tsunami for seismic dislocations we also consider the ratio i 1 of maximum run up to seismic slip on the fault plane and validate numerically the previously suggested rule of thumb that this ratio cannot be much greater than 1 in the case of underwater landslides we show that the distribution of near field run up is primarily controlled by the 2 d wall of water displaced on the ocean surface as an initial condition to the simulation and is practically independent of its extension in the third dimension perpendicular to the beach we apply this approach to nine profiles of tsunami run up obtained experimentally during recent field surveys and show that our method successfully identifies the 1998 papua new guinea tsunami as having been generated by an underwater landslide thus confirming the results of shipboard and hydroacoustic investigations it also strongly suggests a similar mechanism for the generation of the near field aleutian tsunami of 1946 april 1