statistical analysis of the induced basel 2006 earthquake sequence introducing a probability based monitoring approach for enhanced geothermal systems summary geothermal energy is becoming an important clean energy source however the stimulation of a reservoir for an enhanced geothermal system egs is associated with seismic risk due to induced seismicity seismicity occurring due to the water injection at depth have to be well recorded and monitored to mitigate the seismic risk of a damaging event an appropriate alarm system needs to be in place for each individual experiment in recent experiments the so called traffic light alarm system based on public response local magnitude and peak ground velocity was used we aim to improve the pre defined alarm system by introducing a probability based approach we retrospectively model the ongoing seismicity in real time with multiple statistical forecast models and then translate the forecast to seismic hazard in terms of probabilities of exceeding a ground motion intensity level one class of models accounts for the water injection rate the main parameter that can be controlled by the operators during an experiment by translating the models into time varying probabilities of exceeding various intensity levels we provide tools which are well understood by the decision makers and can be used to determine thresholds non exceedance during a reservoir stimulation this however remains an entrepreneurial or political decision of the responsible project coordinators we introduce forecast models based on the data set of an egs experiment in the city of basel between 2006 december 2 and 8 approximately 11500 m 3 of water was injected into a 5km deep well at high pressures a six sensor borehole array was installed by the company geothermal explorers limited gel at depths between 300 and 2700 m around the well to monitor the induced seismicity the network recorded approximately 11200 events during the injection phase more than 3500 of which were located with the traffic light system actions where implemented after an ml 2 7 event the water injection was reduced and then stopped after another ml 2 5 event a few hours later an earthquake with ml 3 4 felt within the city occurred which led to bleed off of the well a risk study was later issued with the outcome that the experiment could not be resumed we analyse the statistical features of the sequence and show that the sequence is well modelled with the omori utsu law following the termination of water injection based on this model the sequence will last 31 29 14 years to reach the background level we introduce statistical models based on reasenberg and jones and epidemic type aftershock sequence etas models commonly used to model aftershock sequences we compare and test different model setups to simulate the sequences varying the number of fixed and free parameters for one class of the etas models we account for the flow rate at the injection borehole we test the models against the observed data with standard likelihood tests and find the etas model accounting for the on flow rate to perform best such a model may in future serve as a valuable tool for designing probabilistic alarm systems for egs experiments

landslides in sado island of japan part ii gis based susceptibility mapping with comparisons of results from two methods and verifications abstract slope instability research and susceptibility mapping is a fundamental component of hazard management and an important basis for provision of measures aimed at decreasing the risk of living with landslides on this basis this paper presents the result of a comprehensive study on slope stability analyses and landslide susceptibility mapping carried out in part of sado island of japan various types of landslides occurred in the island throughout history little is known about the triggering factors and severity of old landslides but for many of the recent slope failures the slope characteristics and stratigraphy are such that ground surfaces retain water perennially and landslides occur when additional moisture is induced during rainfall and snowmelt a range of methods are available in literature for preparation of landslide susceptibility maps in this study we used two methods namely the analytical hierarchy process ahp and logistic regression to produce and later compare two susceptibility maps ahp is a semi qualitative method which involves a matrix based pair wise comparison of the contribution of different factors for landsliding logistic regression on the other hand promotes a multivariate statistical analysis with an objective to find the best fitting model that describes the relationship between the presence or absence of landslides dependent variable and a set of causal factors independent parameters elevation lithology and slope gradient were casual factors in this study the determinations of factor weights by ahp and logistic regression were preceded by the calculation of class weights landslide densities based on bivariate statistical analyses bsa the differences between the ahp derived susceptibility map and the logistic regression counterpart are relatively minor when broad based classifications are considered however with an increase in the number of susceptibility classes the logistic regression map gave more details but the one derived by ahp failed to do so the reason is that the majority of pixels in the ahp map have high values and an increase in the number of classes gives little change in the spatial distribution of susceptibility zones in the middle to verify the practicality of the two susceptibility maps both of them were compared with a landslide activity map containing 18 active landslide zones the outcome was that the active landslide zones do not completely fit into the very high susceptibility class of both maps for various reasons but 70 of these landslide zones fall into the high and very high susceptibility zones of the ahp map while this is 63 in the case of logistic regression this indicates that despite the skewed distribution of susceptibility indices the ahp map was better to capture the reality on the ground than the logistic regression equivalent

characteristics of a surface buoyant jet tidal outflow from leschenault estuary in winter forms an unsteady surface buoyant jet in koombana bay on each outgoing tide as the water moves away from the exit channel and spreads radially over the bay it assumes a plumelike nature the mean features of this buoyant outflow such as the plume shape frontal celerity internal circulation and the bulk entrainment were measured in an intensive field program these features are shown to compare favorably with results from previous laboratory investigations and predictions from a simple inertia buoyancy force balance which includes entrainment at the front the stability of the plume frontal region was examined and it is shown that subfronts were present but their behavior cannot be explained by reference to previous work

role of surface films in ers sar signatures of internal waves on the shelf 1 short period internal waves analysis of synthetic aperture radar sar images of internal waves iws on the iberian shelf and classification of the iw surface signatures is presented there are three types of iw signatures in the form of bright dark dark and bright bands that correspond to positive negative negative or positive variations of radar backscatter respectively strong positive sign iw signatures occur at very low wind velocities less than 2m s at winds higher than 2 m s both positive negative and negative signatures are observed for range propagating iws for azimuth propagating iws negative signatures prevail two groups of experiments carried out in the frame of the multidisciplinary oceanographic research in the eastern north atlantic morena project on the iberian shelf in august 1994 are described 1 iw measurements simultaneous with ers 1 sar overpasses and 2 iw measurements visual observations of the surface and sampling of films from the sea surface iw manifestations at low to moderate winds took the form of slicks locating over iw troughs at the near threshold wind velocity they were of the form of intensified decimeter scale waves antislicks located over iw crests measurements of wave damping due to films collected from the slick and nonslick areas showed the concentration of surfactants and retrieved film elasticity to be higher in the slicks than in the nonslick areas a theoretical model of the surface wave modulation by iws is developed to include surface wave straining by the iw current and surface wave damping due to surfactant films pressure area curves for real marine films are used in the model the relation between the film and the straining effects on the surface wave spectrum in the iw field is shown to depend on film parameters surface wave length and wind velocity the model predicts strong damping of centimeter scale waves over iw troughs mainly due to the film effect and intensification and depression of decimeter scale waves due to both straining and film effects dependencies of the model spectrum variations as a function of wind velocity for range and azimuth propagating iws are obtained the negative sign contrast being shown to predominate for azimuth propagating iws model variations of the spectrum of decimeter scale waves are shown to be significantly sensitive to surfactants film pressure the negative sign contrasts due to films being superimposed on the straining effects and these are eventually capable of suppressing the positive sign contrasts it is concluded that the occurrence of the different classes of iw signatures in the sar images can be explained by the action of surface active films

an airborne real aperture radar study of the chesapeake bay outflow plume an airborne real aperture radar rar has been used to study the fronts associated with the chesapeake bay outflow plume during spring outflow conditions the rar produced images of the ocean surface with a range resolution of 10 m an azimuthal resolution of approximately 30 m and an image size of 2 5 km 24 km two sampling strategies were utilized one to synoptically map the entire mouth of the chesapeake bay at roughly hourly intervals and a second to capture the rapid evolution of particular features in addition flight times were chosen such that over the course of the entire experiment data were collected over all phases of the semidiurnal tidal cycle three distinct frontal signatures were observed in the imagery a primary front extended from inside the estuary along the chesapeake channel to an anticyclonic turning region east of cape henry and then extended southward along the coast toward cape hatteras this is the classic expression of the plume front inertial turning region and coastal jet a second front with a north south orientation was observed approximately 20 km east of the bay mouth this secondary front appears to mark the residual offshore density gradient a third front was identified east and south of cape henry within 2 km of the coast this front appears to mark the inshore edge of the plume and has not been documented previously time sequences of the imagery indicate that when moving in a clockwise sense around the primary front the frontal translation speed varies systematically from 20 cm s in the northern section to 50 cm s in the south the position of the primary front and the locations and trajectories of small scale frontal cusps suggest that bathymetry may be both a significant determinant of the front location as well as a source of along front variability these observations are possible due to the airborne rar s ability to collect high frame rate image sequences a capability that is not shared by present space based radar systems

chronology of warm core ring 82b a chronology constructed from satellite derived thermal imagery is presented to describe the formation and life history of warm core ring 82b this overview provides insight into a classification of features and discrete events associated with gulf stream warm core rings and allows these events as well as our limited shipboard observations to be placed in a broader spatial and temporal context than would otherwise be possible without the satellite data events influencing the evolution of 82b include environmental factors such as meteorological influences and gulf stream interactions as well as those stimulated by encounters with changes in bottom topography the interactions of the ring with surrounding waters are especially noteworthy and the existence of vortex vortex interactions is shown to be a significant cause of local water advection through streamer activity ring events are documented by following changes in ring size shape translation and surface thermal structure our satellite observations are supported by extensive contemporaneous shipboard observations including xbt ctd bops biooptical profiling system temperature profiles and along track sea surface temperature measurements in addition acoustic velocity profiling and drifter trajectories have been used to corroborate hydrographic features of the ring and environs these ship and satellite data form a coherent space time overview of the ring and its environment and show them to be closely related and continually interacting

foreshock occurrence before large earthquakes rates of foreshock occurrence involving shallow m 6 and m 7 mainshocks and m 5 foreshocks were measured in two worldwide catalogs over 20 year intervals the overall rates observed are similar to ones measured in previous worldwide and regional studies when they are normalized for the ranges of magnitude difference they each span the observed worldwide rates were compared to a generic model of earthquake clustering based on patterns of small and moderate aftershocks in california the aftershock model was extended to the case of moderate foreshocks preceding large mainshocks overall the observed worldwide foreshock rates exceed the extended california generic model by a factor of 2 significant differences in foreshock rate were found among subsets of earthquakes defined by their focal mechanism and tectonic region with the rate before thrust events higher and the rate before strike slip events lower than the worldwide average among the thrust events a large majority composed of events located in shallow subduction zones had a high foreshock rate while a minority located in continental thrust belts had a low rate these differences may explain why previous surveys have found low foreshock rates among thrust events in california especially southern california while the worldwide observations suggests the opposite california lacking an active subduction zone in most of its territory and including a region of mountain building thrusts in the south reflects the low rate apparently typical for continental thrusts while the worldwide observations dominated by shallow subduction zone events are foreshock rich if this is so then the california generic model may significantly underestimate the conditional probability for a very large m 8 earthquake following a potential m 7 foreshock in cascadia the magnitude differences among the identified foreshock mainshock pairs in the harvard catalog are consistent with a uniform distribution over the range of observation

theory of radar imaging of internal waves radar images taken over ocean areas in particular those obtained by the synthetic aperture radar sar onboard the american seasat satellite in 19781 2 sometimes show features that seem to be surface manifestations of oceanic internal waves3 11 here i present a theory explaining the large radar signatures of internal waves in which the imaging is attributed to variations in the short scale surface roughness induced by current variations associated with internal waves

assessment of rockfall susceptibility by integrating statistical and physically based approaches in val di fassa dolomites eastern italian alps rockfalls constitute the most significant gravity induced natural disaster that threatens both the inhabitants of the valley who are few and the thousands of tourists who populate the area in summer and winter to assess rockfall susceptibility we developed an integrated statistical and physically based approach that aimed to predict both the susceptibility to onset and the probability that rockfalls will attain specific reaches through field checks and multi temporal aerial photo interpretation we prepared a detailed inventory of both rockfall source areas and associated scree slope deposits using an innovative technique based on gis tools and a 3d rockfall simulation code grid cells pertaining to the rockfall source area polygons were classified as active or inactive based on the state of activity of the associated scree slope deposits the simulation code allows one to link each source grid cell with scree deposit polygons by calculating the trajectory of each simulated launch of blocks by means of discriminant analysis we then identified the mix of environmental variables that best identifies grid cells with low or high susceptibility to rockfalls among these variables structural setting land use and morphology were the most important factors that led to the initiation of rockfalls we developed 3d simulation models of the runout distance intensity and frequency of rockfalls whose source grid cells corresponded either to the geomorphologically defined source polygons geomorphological scenario or to study area grid cells with slope angle greater than an empirically defined value of 37 empirical scenario for each scenario we assigned to the source grid cells an either fixed or variable onset susceptibility the latter was derived from the discriminant model group active inactive membership probabilities comparison of these four models indicates that the geomorphological scenario with variable onset susceptibility appears to be the most realistic model nevertheless political and legal issues seem to guide local administrators who tend to select the more conservative empirically based scenario as a land planning tool

elastic strain energy and pore fluid pressure control of aftershocks abstract aftershocks are well known however their triggering mechanisms remain unclear the coulomb failure stress change cfs has been widely implemented to understand the spatial distribution of aftershocks here we propose a new metric for evaluating aftershock generation based on the energetics of shear faulting in a prestressed state unlike cfs the new metric depends not only on coseismic stress changes but also on background crustal stresses the energetics based formulation expands the cfs defined on a specific plane into a generalized failure stress defined in a three dimensional space we examined the diagnostic ability of the new metric by applying receiver operating characteristic analysis to 12 175 aftershocks m 0 that followed the 1992 landers earthquake with a realistic background stress field inferred from thousands of earthquake focal mechanisms the new metric was able to discriminate the triggering mechanisms of the aftershocks two thirds were direct responses to coseismic stress changes and one fifth resulted from strength decreases owing to pore fluid pressure increases

the angle of reach as a mobility index for small and large landslides the relations between the angle of reach fahrboschung and other indexes expressing the mobility of landslides and vertical drop horizontal reach and volume of landslide mass have been analyzed by means of simplified plots and regression equations results for 204 landslides of all sizes show that whatever the mechanism of motion all kinds of landslides experience a continuous reduction of the angle of reach with volume increase this reduction starts from the smallest sizes scattering in this relation is mostly due to mechanisms of motion and to both obstacles and topographic constraints on the path this synthesis indicates that small landslides less than 0 5 106 m3 in relative terms display excesses of travel distance similar to large landslides since most small landslides are not expected to develop any change in the mechanism of progression while moving the decrease in the reach angle with volume suggests that scale effects should be taken into account the angle of reach is found to be

fundamental questions of earthquake statistics source behavior and the estimation of earthquake probabilities from possible foreshocks abstract estimates of the probability that an m l 4 8 earthquake which occurred near the southern end of the san andreas fault on 24 march 2009 would be followed by an m 7 mainshock over the following three days vary from 0 0009 using a gutenberg richter model of aftershock statistics reasenberg and jones 1989 to 0 04 using a statistical model of foreshock behavior and long term estimates of large earthquake probabilities including characteristic earthquakes agnew and jones 1991 i demonstrate that the disparity between the existing approaches depends on whether or not they conform to gutenberg richter behavior while gutenberg richter behavior is well established over large regions it could be violated on individual faults if they have characteristic earthquakes or over small areas if the spatial distribution of large event nucleations is disproportional to the rate of smaller events i develop a new form of the aftershock model that includes characteristic behavior and combines the features of both models this new model and the older foreshock model yield the same results when given the same inputs but the new model has the advantage of producing probabilities for events of all magnitudes rather than just for events larger than the initial one compared with the aftershock model the new model has the advantage of taking into account long term earthquake probability models using consistent parameters the probability of an m 7 mainshock on the southernmost san andreas fault is 0 0001 for three days from long term models and the clustering probabilities following the m l 4 8 event are 0 00035 for a gutenberg richter distribution and 0 013 for a characteristic earthquake magnitude frequency distribution our decisions about the existence of characteristic earthquakes and how large earthquakes nucleate have a first order effect on the probabilities obtained from short term clustering models for these large events

estuarine plume a case study by satellite sar observations and in situ measurements estuary plumes on the western louisiana continental shelf in the gulf of mexico outside of constricted channels of the sabine and calcasieu lakes were observed on two radarsat 1 synthetic aperture radar sar images the in situ data showed a change in salinity of 2 3 psus across the front on the northwest edge of the plume corresponding to locations of vertical salinity variation of 5 5 7 5 psu velocity magnitude outside of the inlet reached more than 2 3 ms mathrm 1 seaward and a brackish lens in the upper 4 5 m of the water column the spread of which contributed to the development of a plume the volume of brackish water within the plume was estimated an order of magnitude larger than the volume output from the calcasieu river within an entire ebb tidal period this implies that the plume was formed during multiple tidal cycles and it sustained during the flood tides because only weak diurnal tides exist both satellite and in situ observations showed an interesting western intensification of the plume an analysis to the momentum vorticity equations suggests that the western intensification is due to the asymmetry of the vorticity divergence relationship under the coriolis force this can also be enhanced by an ambient coastal current that strengthens the convergence at the front estuary plumes are shown as bright and dark features in two sar images results from a radar model simulation and in situ water temperature data showed that the sar observed plume features were dominated by the water temperature differences

a note on seismic activity near the eastern termination of the izmit rupture in the hours preceding the duzce earthquake we use continuous recordings at four stations installed near the eastern termination of the izmit rupture to analyze the seismic activity there during the 5 hr leading to the duzce earthquake the records clearly show the presence of three groups of events one of the groups originates from the middle of the izmit rupture and consists of aftershocks of the m 5 7 spanca lake earthquake that had occurred a day earlier and was itself to date the second largest aftershock in the izmit sequence a second group of events is spread over the 30 km long eastern karadere segment of the izmit rupture and a comparison with the number of aftershocks expected based on decay laws for similar sequences in other regions suggests that seismic activity was high on the eastern segment in the hours leading to the duzce earthquake the third group of events occurs beyond the termination of the izmit rupture and clusters around the hypocenter of the duzce earthquake it shows that in the little over 5 hr leading to the duzce earthquake this destructive event was preceded by six precursory shocks ranging in magnitude from 0 9 to 2 6 manuscript received 30 august 2000

evaluation of rock slope stability for a touristic coastal area near kusadasi aydin turkey the study area which will be open to tourism in kusadasi aydin has steep and high cliffs on the aegean coast in turkey flysch is the main lithological unit and consists of alternating sandstone claystone marl sequences some sliding and rockfall problems have occurred in the area in the past so potential geological hazards need to be investigated to ensure the safety of tourists the aim of this study is to mitigate geological hazards by recommending engineering solutions which will ensure the continuation of the nature friendly appearance of the slopes to accomplish these tasks a geological survey was performed it involved gathering information on rock discontinuities by means of scan line surveys and collection of rock samples furthermore in situ and laboratory tests were also carried out the data collected from the field and laboratory test results were used to perform slope stability and rockfall 2 d and 3 d analyses for different slope conditions along 43 profiles based on the analyses rockfall was found to be the main slope instability problem in the study area under the light of these studies rock removal drainage greening vegetation filling of caverns protective wall building and erosion prevention are offered as remedial measures

the rhine outflow plume studied by the analysis of synthetic aperture radar data and numerical simulations the dynamics of the rhine outflow plume in the proximity of the river mouth is investigated by using remote sensing data and numerical simulations the remote sensing data consist of 41 synthetic aperture radar sar images acquired by the first and second european remote sensing satellites ers 1 and ers 2 over the outflow region of the river rhine most of them show sea surface signatures of oceanic phenomena for example surface current and wind variations ship wakes and oil slicks in particular in 36 of these images pronounced frontal features are visible as narrow zones of mainly enhanced sometimes enhanced reduced radar backscatter that can be associated with the rhine surface front within the area enclosed by the frontal line large zones characterized by a lower radar backscatter than in the outer area are often visible the analysis of the ers sar images suggests that the form and the location of the frontal features are mainly linked to the semidiurnal tidal phase in the outflow region although their variability suggests also that they weakly depend on river discharge residual currents and neap spring tidal cycle in order to test this observational hypothesis the results obtained from the analysis of the ers sar images are compared with the results obtained from the numerical simulation of the hydrodynamics of the rhine outflow region carried out using a two layer frontal model which is based on the nonlinear hydrostatic shallow water equations on an f plane the model is forced by prescribing tidal and residual currents and river discharge at the open boundaries several simulations are performed by varying the values of these forcing parameters the numerical results corroborate the observational conjecture it is found that the form and the location of the simulated interface outcropping lines in the proximity of the river mouth are mainly determined by the semidiurnal tidal phase in the outflow region and that river discharge residual currents and neap spring tidal cycle contribute only secondarily to their determination inserting the simulated surface velocity field into a simple radar imaging model that relates the modulation of the backscattered radar power to the surface velocity convergence in radar look direction narrow elongated bands of enhanced radar backscatter emerge near the model frontal line while patches of low radar backscatter appear within the simulated rhine plume area the consistency of the model results with the results obtained from the analysis of the sar images enables one to infer a mean spatial and temporal evolution of the rhine outflow plume over a semidiurnal tidal cycle from the analysis of spaceborne sar images acquired during different tidal cycles over the rhine outflow area and suggests the possibility of using numerical modeling in conjunction with the analysis of spaceborne measurements for monitoring the oceanic variability in the rhine outflow area

relation between mainshock rupture process and omori s law for aftershock moment release rate summary we compare the source time functions i e moment release rates of three large california mainshocks with the seismic moment release rates during their aftershock sequences aftershock moment release rates computed by summing aftershock moments in time intervals follow a power law time dependence similar to omori s law from minutes to months after the mainshock furthermore in contrast to the previously observed saturation in numbers of aftershocks shortly after the mainshock rupture no such saturation is seen in the aftershock moment release rates which are dominated by the largest aftershocks we argue that the observed saturation in aftershock numbers described by the time offset parameter c in omori s law is likely an artefact due to the underreporting of small aftershocks which is related to the difficulty of detecting large numbers of small aftershocks in the mainshock coda we further propose that it is more natural for c to be negative i e singularity follows the onset of mainshock rupture than positive singularity precedes onset of rupture to make a more general comparison of mainshock rupture process and aftershock moment rates we then scale mainshock time functions to equalize the effects of the varied seismic moments for the three california mainshocks we compare the scaled time functions with similarly scaled aftershock moment rates finally we compare global averages of scaled time functions of many shallow events to the average scaled aftershock moment release rate for six california mainshocks in each of these comparisons the extrapolation using omori s law of the aftershock moment rates back in time to the onset of the mainshock rupture indicates that the temporal intensity of the aftershock moment release is about 1 5 orders of magnitude less than the maximum reached by the mainshock rupture this may be due to the differing amplitudes and relative importance of static and dynamic stresses in aftershock initiation compared to mainshock rupture propagation

coastal ocean fronts and eddies imaged with ers 1 synthetic aperture radar ers 1 c band synthetic aperture radar sar data were collected during the norwegian continental shelf experiment norcsex both in november 1991 during the ers 1 commissioning phase and at different seasons in 1992 and 1993 characteristic sar image expressions are observed in relation to perturbation of the surface current short wave interaction across the norwegian coastal current front for winds less than 10 12 rn s 1 in situ measurements document the existence of alternating zones of convergence and divergence coexisting with a strong near surface current shear of nearly 4f where f is the coriolis parameter across a distance of a few kilometers under calm to moderate winds i e 4 7 rn s 1 characteristic expressions of upper ocean circulation features also include the manifestation of eddies through the presence of surface film which damps the bragg waves comparison of a near coincident national oceanic and atmospheric administration advanced very high resolution radiometer image and an ers 1 sar image supports the interpretation that surface current fronts are imaged by sar in combination with an sar image simulation model the relative quantitative importance of shear convergence and divergence along the front is examined although the model formulation is simple and the absolute magnitude of the perturbations is uncertain the study shows that the sar images can sometimes be used to interpret frontal dynamics including growth and decay of meanders

the assessment of rockfall hazard at the base of talus slopes fragmental rockfall is characterized by the independent movement of individual rock fragments after detachment from a rock face the continued operation of the process leads to the accumulation of talus slopes on talus slopes the rockfall shadow extends beyond the base of the talus and consists of scattered boulders that have run out beyond the base of the slope the landing probability of boulders in the shadow is examined return periods of the order of 1000 years relative to a house site are typical rockfall behaviour particularly with respect to run out into the shadow can be assessed using geological evidence empirical methods physical modelling and computer based analytical models an empirical minimum shadow angle of 27 5 i e the angle between the distal limit of the shadow and the top of the talus slope is suggested and would be useful in rockfall vulnerability studies at the base of talus slopes as a first approximation to shadow limits it is preferable to the use of the rockfall fahrb

a gis based comparative study of frequency ratio analytical hierarchy process bivariate statistics and logistics regression methods for landslide susceptibility mapping in trabzon ne turkey abstract over the last few decades many researchers have produced landslide susceptibility maps using different techniques including the probability method frequency ratio the analytical hierarchy process ahp bivariate multivariate logistics regression fuzzy logic and artificial neural network in addition a number of parameters such as lithology slope aspect land cover elevation distance to stream drainage density distance to lineament seismicity and distance to road are recommended to analyze the mechanism of landslides the data quality is a very important issue in landslide studies and more accurate results will be achieved if the data is adequate appropriate and drawn from a wide range of parameters the aim of this study was to evaluate the susceptibility of the occurrence of landslides in trabzon province situated in north east turkey this was achieved using the following five methods the frequency ratio model ahp the statistical index wi weighting factor wf methods and the logistics regression model incorporating a geographical information system gis and remote sensing techniques in trabzon province there has been an increasing occurrence of landslides triggered by rainfall these landslides have resulted in death significant injury damage to property and local infrastructure and threat of further landslides continues in order to reduce the effects of this phenomenon it is necessary to scientifically assess the area susceptible to landslide to achieve this landslide susceptible areas were mapped the landslide occurrence parameters were analyzed using five different methods the results of the five analyses were confirmed using the landslide activity map containing 50 active landslide zones then the methods giving more accurate results were determined the validation process showed that the wf method is better in prediction than the frequency ratio model ahp the statistical index wi and logistics regression model

landslide hazard evaluation a review of current techniques and their application in a multi scale study central italy in recent years growing population and expansion of settlements and life lines over hazardous areas have largely increased the impact of natural disasters both in industrialized and developing countries third world countries have difficulty meeting the high costs of controlling natural hazards through major engineering works and rational land use planning industrialized societies are increasingly reluctant to invest money in structural measures that can reduce natural risks hence the new issue is to implement warning systems and land utilization regulations aimed at minimizing the loss of lives and property without investing in long term costly projects of ground stabilization government and research institutions worldwide have long attempted to assess landslide hazard and risks and to portray its spatial distribution in maps several different methods for assessing landslide hazard were proposed or implemented the reliability of these maps and the criteria behind these hazard evaluations are ill formalized or poorly documented geomorphological information remains largely descriptive and subjective it is hence somewhat unsuitable to engineers policy makers or developers when planning land resources and mitigating the effects of geological hazards in the umbria and marche regions of central italy attempts at testing the proficiency and limitations of multivariate statistical techniques and of different methodologies for dividing the territory into suitable areas for landslide hazard assessment have been completed or are in progress at various scales these experiments showed that despite the operational and conceptual limitations landslide hazard assessment may indeed constitute a suitable cost effective aid to land use planning within this framework engineering geomorphology may play a renewed role in assessing areas at high landslide hazard and helping mitigate the associated risk

coastal circulations driven by river outflow in a variable density 1 layer model a variable density 1 layer model is used to investigate the dynamics of the fresher water plumes generated by river outflow solutions are found in a north south channel and the transport mr and salinity sr of the outflow are specified as boundary conditions along a 25 km wide segment of the western boundary in most cases the river water discharges into a preexisting oceanic mixed layer with thickness h1 when mr is sufficiently low plumes remain coastally trapped immediately after the outflow is switched on a coastal kelvin wave is excited at the river mouth that establishes a southward current of oceanic water along the right hand coast in contrast all the river water first bends to the left as it exits the river mouth and the resulting plume advances northward along the left hand coast at the plume nose some of the fresher water reverses direction and this water together with some oceanic water flows southward on either side of the offshore density front between the fresher and salty waters two processes cause this upstream movement geostrophic adjustment generates the southward frontal current and kelvin wave propagation from the nose thins the layer within the plume thereby establishing the northward geostrophic coastal jet when mr is sufficiently high coastally trapped plumes no longer exist if the rossby number of the outflow is also large enough the river water flows directly offshore and only a portion of it recirculates to form a northward propagating coastal plume the angle at which the outflow leaves the river mouth becomes more southward as mr and sr increase and as h1 decreases the strength of the northward propagating plume is weakened as h1 decreases and sr increases when h1 0 so that there is no ambient oceanic layer there is no northward plume at all likewise the plume is weakened when the model includes entrainment a process that acts to prevent the layer thickness from thinning appreciably

gis based landslide susceptibility mapping for a problematic segment of the natural gas pipeline hendek turkey a segment of natural gas pipeline was damaged due to landsliding near hendek re routing of the pipeline is planned but it requires the preparation of a landslide susceptibility map in this study the statistical index wi and weighting factor wf methods have been used with gis to prepare a landslide susceptibility map of the problematic segment of the pipeline for this purpose thematic layers including landslide inventory lithology slope aspect elevation land use land cover distance to stream and drainage density were used in the study area landslides occur in the unconsolidated to semi consolidated clayey unit and regolith the wf method gives better results than the wi method lithology is found to be the most important aspect in the study area based on the findings obtained in this study the unconsolidated to semi consolidated clayey unit and alluvium should be avoided during re routing agricultural activities should not be allowed in the close vicinity of the pipeline

deep learning of aftershock patterns following large earthquakes aftershocks are a response to changes in stress generated by large earthquakes and represent the most common observations of the triggering of earthquakes the maximum magnitude of aftershocks and their temporal decay are well described by empirical laws such as bath s law1 and omori s law2 but explaining and forecasting the spatial distribution of aftershocks is more difficult coulomb failure stress change3 is perhaps the most widely used criterion to explain the spatial distributions of aftershocks4 8 but its applicability has been disputed9 11 here we use a deep learning approach to identify a static stress based criterion that forecasts aftershock locations without prior assumptions about fault orientation we show that a neural network trained on more than 131 000 mainshock aftershock pairs can predict the locations of aftershocks in an independent test dataset of more than 30 000 mainshock aftershock pairs more accurately area under curve of 0 849 than can classic coulomb failure stress change area under curve of 0 583 we find that the learned aftershock pattern is physically interpretable the maximum change in shear stress the von mises yield criterion a scaled version of the second invariant of the deviatoric stress change tensor and the sum of the absolute values of the independent components of the stress change tensor each explain more than 98 per cent of the variance in the neural network prediction this machine learning driven insight provides improved forecasts of aftershock locations and identifies physical quantities that may control earthquake triggering during the most active part of the seismic cycle neural networks trained on data from about 130 000 aftershocks from around 100 large earthquakes improve predictions of the spatial distribution of aftershocks and suggest physical quantities that may control earthquake triggering

numerical simulations of large earthquakes dynamic rupture propagation on heterogeneous faults our current conceptions of earthquake rupture dynamics especially for large earthquakes require knowledge of the geometry of the faults involved in the rupture the material properties of the rocks surrounding the faults the initial state of stress on the faults and a constitutive formulation that determines when the faults can slip in numerical simulations each of these factors appears to play a significant role in rupture propagation at the kilometer length scale observational evidence of the earth indicates that at least the first three of the elements geometry material and stress can vary over many scale dimensions future research on earthquake rupture dynamics needs to consider at which length scales these features are significant in affecting rupture propagation

long term evolution of elongated warm eddies abstract the purpose of this research is to investigate the evolution of elongated warm eddies a shallow water reduced gravity primitive equation model is used to perform a multicase numerical experiment which includes vortices of very different eccentricities and strengths the above is partly motivated by the increased number of oceanic observations performed in recent years that show the wide variety of warm eddies under the assumption that an eddy can be approximately described as a solid body rotating elliptical vortex the evolution is followed using a least squares fitting procedure results indicate that the majority of these eddies evolve toward less eccentric states a process called axisymmetrization a few of the most elongated eddies break up and some of the less eccentric ones remain unchanged axisymmetrization seems to be triggered by instability and in the space of the parameters that describe the elliptical vortex the trajectories followed in each of the cases fairly approximat

semidiurnal switching of stratification in the region of freshwater influence of the rhine observations in the rhine region of freshwater influence rofi system in the north sea show evidence of large semidiurnal oscillations in stability superimposed on a mean stratification occurring throughout the stratified region at times of reduced mixing the amplitude of this semidiurnal variation is of the same order as the mean stability and frequently results in conditions being mixed or nearly mixed once per tide it is deduced that this semidiurnal variation results primarily from cross shore tidal straining which interacts with the density gradient to induce stratification this conceptual picture of the contributing processes has been tested in a one dimensional point model forced by the observed slopes and the local density gradients the model exhibits the same qualitative behavior as the observations produces oscillations in stratification of the amplitude observed and confirms the critical role of cross shore tidal straining the large cross shore shear nder stratified conditions is identified with the changes in ellipse configuration which are observed between mixed and stratified conditions the occurrence of semidiurnal variations in stability in the rhine rofi is thus inferred to be a consequence of the development of mean stability whenever the horizontal density gradients relax in conditions of low stirring

earthquake hazard after a mainshock in california after a strong earthquake the possibility of the occurrence of either significant aftershocks or an even stronger mainshock is a continuing hazard that threatens the resumption of critical services and reoccupation of essential but partially damaged structures a stochastic parametric model allows determination of probabilities for aftershocks and larger mainshocks during intervals following the mainshock the probabilities depend strongly on the model parameters which are estimated with bayesian statistics from both the ongoing aftershock sequence and from a suite of historic california aftershock sequences probabilities for damaging aftershocks and greater mainshocks are typically well constrained after the first day of the sequence with accuracy increasing with time

ocean surface features and currents measured with synthetic aperture radar interferometry and hf radar this paper describes the results of the first quantitative comparison between high resolution ocean surface current fields extracted from interferometric synthetic aperture radar insar measurements and those from a high frequency hf ocean surface current radar oscr system data from each of these radar systems along with supporting measurements from shipboard and buoy mounted sensors were collected during the high resolution remote sensing experiment high res on june 20 1993 on the continental shelf off the coast of cape hatteras north carolina both components of the surface current were obtained from the insar system at roughly 10 m resolution from two orthogonal flight legs over the region separated in time by about 30 min the oscr system measured two dimensional surface current vectors at about 1 km resolution over this same region while the usns bartlett was collecting hydrographic samples and near surface current measurements two dimensional wave spectra as well as meteorological and additional current measurements were collected at two buoys within the experimental area we discuss in the paper two techniques for eliminating the effect of surface wave motion on the insar current estimates one method relies on some knowledge of the local wind and wave field and the use of a microwave scattering model the other method makes use of a few in situ current measurements spaced at different range locations across the insar image using either of these techniques we find that the agreement between the insar and oscr current estimates is generally very good furthermore the insar current and magnitude imagery show the presence of undulating surface features where abrupt changes in the current speed and direction occurred the ship surveys indicate that these features were caused by the collision of water masses of different density we show for the first time in this paper a high resolution area extensive vector surface current map derived from the insar of the two dimensional flow in the vicinity of these features our results demonstrate convincingly that high resolution oceanic surface current vectors can be derived from insar current measurements and that these measurements may be very beneficial for detailed studies of the dynamics of small scale surface features in regions of strong current divergences or shears

assessment of rockfall hazard around afyon castle turkey the afyon castle is a tourist destination and a historical site in the city of afyon in turkey the castle is located on a steep hill with a height of 226 m in close proximity to the castle there are settlements the hill consists of trachitic andesite the rock contains columnar joints and flow layering owing to these discontinuities blocks of varying sizes had fallen down the settlement areas near the castle are now in danger because of the rockfall risk in this study rockfall analysis was carried out along nine profiles of the hill fall out distance bounce height kinetic energy and velocity of the rocks along each profile were investigated the results of the analyses were evaluated and the areas delineated as susceptible to rockfall risk are highlighted remedial measures including rock bolts and protective fences were suggested on the basis of the field observations and the rockfall risk evaluation

geodetic investigation into the deformation of the salton trough 1 the salton trough represents a complex transition between the spreading center in baja california and the strike slip san andreas fault system and is one of the most active zones of deformation and seismicity in california we present a high resolution interseismic velocity field for the salton trough derived from 74 continuous gps sites and 109 benchmarks surveyed in three gps campaigns during 2008 2009 and previous surveys between 2000 and 2005 we also investigate small scale deformation by removing the regional velocity field predicted by an elastic block model for southern california from the observed velocities we find a total extension rate of 11 mm yr from the mesquite basin to the southern edge of the san andreas fault coupled with 15 mm yr of left lateral shear the majority of which is concentrated in the southern salton sea and obsidian buttes and is equivalent to 17 mm yr oriented in the direction of the san andreas fault differential shear strain is exclusively localized in the brawley seismic zone and dilatation rate indicates widespread extension throughout the zone in addition we infer clockwise rotation of 10 ma consistent with northwestward propagation of the brawley seismic zone over geologic time

landslide susceptibility analysis with a heuristic approach in the eastern alps vorarlberg austria the aim of the study is landslide hazard assessment carried out on a working scale of 1 25 000 the study area within the northern calcareous alps was geologically and geotechnically mapped in order to identify causes and mechanisms of active mass movements the field surveys were digitised by a geographical information system and divided into data layers the geological units were classified according to their geotechnical properties all layers were converted into grids and spatially analysed together with a digital elevation model comparing the layers with the inventory of active landslides the prevailing factors leading to sliding movements were identified because of the complex tectonic setting and the small number of active landslides a statistical method of hazard assessment was not applicable using the heuristic approach of an index method the data layers of geotechnical class bedding conditions tectonic layouts slope angles slope orientations vegetation and erosion were analysed the susceptibility of each layer has been evaluated with help of bivariate statistics the layers have been weighted with indices due to their importance iteratively and were combined into a landslide susceptibility map

field investigation and rockfall hazard zonation at the shijing mountains sutra caves cultural heritage china sutra inscriptions have been a main means for buddhistic monks to pass on their teachings nine sutra caves used to store about 5 000 pleromas carved during the sui dynasty of china more than 1 000 years ago were found in the shijing mountains close to beijing these sutra caves area have been affected by past failures and are subject to serious potential rockfall hazard from the relatively low rocky cliffs where caves are located the aim of this study was a preliminary assessment of rockfall hazard for this cultural heritage site to support the design of safe tourist paths the slope geometry has been surveyed by means of a laser profiler these slope profiles have been used for two dimensional distinct elements and rockfall simulations the volumes of more probably unstable rock blocks were measured in situ the results show that the runout distance ranges between 1 6 and 12 5 m affecting the most important tour route the rockfalls threaten the life safety of tourists walking around and waiting for visiting the sutra caves based on the analysis mentioned above a zonation map of runout distance was accomplished in the map the range between the release points of the potential rockfalls and the minimum runout distance is defined as the most dangerous zone the range between the maximum and the minimum runout distance is defined as danger zone the range beyond the runout distance is defined as a safe zone the map provides the guidance to the selection of safe tour routes at the scenic site finally to reduce the rockfall hazard remedial measures including rock bolts placement of an absorbing layer of loose material and flexible barriers are suggested

a multi method approach to study the stability of natural slopes and landslide susceptibility mapping abstract in this paper a multi method approach for the assessment of the stability of natural slopes and landslide hazard mapping applied to the dakar coastal region is presented this approach is based on the effective combination of geotechnical field and laboratory works of gis and of mechanical deterministic and numerical stability analysis by using this approach valuable results were gained regarding instability factors landslide kinematics simulation of slope failure and coastal erosion this led to a thorough assessment and strong reduction in the subjectivity of the slope stability and hazard assessment and to the development of an objective landslide danger map of the sw coast of dakar analysis of the results shows that the slides were influenced by the geotechnical properties of the soil the weathering the hydrogeological situation and the erosion by waves the landslide susceptibility assessment based on this methodological approach has allowed for an appropriate and adequate consideration of the multiple factors affecting the stability and the optimization of planning and investment for land development in the city

comment on elastic strain energy and pore fluid pressure control of aftershocks by terakawa et al earth planet sci lett 535 2020 116103 abstract aftershock occurrence is the dominant phenomenon observed in seismicity offering a wealth of data for the statistical learning of the earthquake nucleation process however physical interpretability can be biased by a number of well known pitfalls in this comment we show that the study of terakawa et al 2020 who concluded that the spatial distribution of aftershocks is best explained by a combination of elastic strain energy and pore fluid pressure change e f s is beset by both confirmation bias and data leakage using the same data 1992 landers mainshock procedure binary classification and metrics area under the curve auc we find that the simple empirical model based on aftershock distance to mainshock rupture mignan and broccardo 2019 performs to a level auc 0 76 similar to the one obtained by e f s auc 0 75 0 70 0 77 including the big bear rupture improves the distance based model performance up to auc 0 86 from a statistical perspective we further show that including pore fluid pressure change being calculated from earthquake focal mechanisms is equivalent to implicitly propagating aftershock location information into the model such type of data leakage clearly improves any classifier performance

introducing probabilistic aftershock hazard mapping aftershocks to large earthquakes pose a significant hazard a fact that was highlighted by damaging aftershocks to the 1999 turkey and taiwan mainshocks a new approach is introduced to quantify this hazard in terms of physical parameter maps that forecast the probabilistic aftershock hazard based on the observed spatially varying aftershock activity for two case studies the landers and northridge mainshocks probabilistic aftershock hazard maps are shown to improve conventional aftershock hazard assessment

tower based measurements of the ocean c band radar backscattering cross section continuous measurements of the c band normalized radar cross section nrcs at vertical vertical polarization as a function of wind speed and direction were carried out from a research platform in the north sea during a period of 11 months in 1984 the nrcss have been correlated with other environmental data routinely collected at the platform like air water temperature difference water temperature and ocean wave slope the wind speed exponent of the c band nrcs at 45 incidence angle was determined as 1 50 valid in the wind speed range 2 19 m s our data set shows that the c band nrcs depends strongly on the air sea temperature difference for example when the air sea temperature difference decreases from 5 c to 5 c the nrcs increases by 6 db at a wind speed of 8 9 m s and an incidence angle of 45 for stable air sea interfaces and low wind speeds the nrcs increases with increasing root mean square wave slope however no systematic dependence on water temperature was observed

role of surface films in ers sar signatures of internal waves on the shelf 2 internal tidal waves analysis of ers 1 synthetic aperture radar sar images over the iberian shelf shows that they contain the signatures of large scale banded structures with characteristic wavelengths of 10 20 km parallel to the shelf break their consistency with the structure of internal tides leads to the conclusion that they are the surface manifestations of internal tidal waves the effect of imaging of such large scale phenomena by sar operating in l c and x bands cannot be explained by conventional hydrodynamic modulation models based on the effect of straining of surface wind waves due to the internal tidal currents an alternative explanation is described by an analysis of modulation of centimeter and decimeter scale surface waves caused by the redistribution of surface active substances by internal tidal currents model calculations of variations of the wind wave spectrum across the internal tide profile are presented an empirical film pressure area equation and the results of thermistor chain measurements of internal tidal waves in the study area were used in the modeling the effect of additional modulation of short surface waves due to variations of wind velocity relative to the internal tidal current is also estimated it is demonstrated that modulation of centimeter decimeter wind waves in the presence of surfactant films is the dominant factor and can explain the effect of internal tidal wave imaging by sar

air sea fluxes and surface layer turbulence around a sea surface temperature front the observed effects of sharp changes in sea surface temperature sst on the air sea fluxes surface roughness and the turbulence structure in the surface layer and the marine atmospheric boundary layer are discussed in situ flux and turbulence observations were carried out from three aircraft and two ships within the fasinex framework three other aircraft used remote sensors to measure waves microwave backscatter and lidar signatures of cloud tops descriptions of the techniques intercomparison of aircraft and ship flux data and use of different methods for analyzing the fluxes from the aircraft data are described changing synoptic weather on three successive days yielded cases of wind direction both approximately parallel and perpendicular to a surface temperature front for the wind perpendicular to the front wind over both cold to warm and warm to cold surface temperatures occurred model results consistent with the observations suggest that an internal boundary layer forms at the sst

how long is an aftershock sequence the occurrence of a mainschok is always followed by aftershocks spatially distributed within the fault area the aftershocks rate decay with time is described by the empirical omori law which was inferred by catalogues analysis the sequences discrimination within catalogues is not a straightforward operation especially for low magnitude mainshocks here we describe the rate decay of the omori law obtained using different sequence discrimination tools and we discover that when the background seismicity is excluded the sequences tend to last for the temporal extension of the catalogue

modeling of two layer eddies and coastal flows with a particle method an existing particle in cell pic numerical method developed for the study of two layer mesoscale motions with outcropping pycnocline is applied to lens like anticyclonic vortices and buoyant coastal currents from a first series of experiments investigating the evolution of an initially elongated lens like anticyclone it is found that motions induced in the lower layer act only to increase the rotation of the vortex structure and do not appear to affect the process of eccentricity reduction partial axisymmetrization eccentricity reduction if any produces a final vortex of aspect ratio between 1 8 and 1 9 a value that is very close to the stability threshold of large reduced gravity lenses a second series of experiments devoted to vortex mergers determines how the maximal separation distance for which two circular anticyclonic lenses merge spontaneously varies with vortex size ratio of lens radius to deformation radius and stratification ratio of lens central thickness to ocean depth a third series of experiments considers the interaction of a lens vortex in the upper layer with a potential vorticity anomaly in the lower layer second hand relative vorticity generated in the lower layer under the action of vertical stretching induced by the movement of the upper layer vortex interacts with first hand relative vorticity created by the existing potential vorticity to create effects similar to those predicted by studies of two layer point vortices hetons finally the pic method is generalized to simulate the finite amplitude instability of a buoyant geostrophic hydrostatic intrusion flowing along a vertical coastal wall those results however are reported here more as a demonstration on how the pic method can be extended to include coastal boundaries than as a thorough investigation of coastal current instabilities

a spatiotemporal clustering model for the third uniform california earthquake rupture forecast ucerf3 etas toward an operational earthquake forecast we the ongoing working group on california earthquake probabilities present a spatiotemporal clustering model for the third uniform california earthquake rupture forecast ucerf3 with the goal being to represent aftershocks induced seismicity and otherwise triggered events as a potential basis for operational earthquake forecasting oef specifically we add an epidemic type aftershock sequence etas component to the previously published time independent and long term time dependent forecasts this combined model referred to as ucerf3 etas collectively represents a relaxation of segmentation assumptions the inclusion of multifault ruptures an elastic rebound model for fault based ruptures and a state of the art spatiotemporal clustering component it also represents an attempt to merge fault based forecasts with statistical seismology models such that information on fault proximity activity rate and time since last event are considered in oef we describe several unanticipated challenges that were encountered including a need for elastic rebound and characteristic magnitude frequency distributions mfds on faults both of which are required to get realistic triggering behavior ucerf3 etas produces synthetic catalogs of m 2 5 events conditioned on any prior m 2 5 events that are input to the model we evaluate results with respect to both long term 1000 year simulations as well as for 10 year time periods following a variety of hypothetical scenario mainshocks although the results are very plausible they are not always consistent with the simple notion that triggering probabilities should be greater if a mainshock is located near a fault important factors include whether the mfd near faults includes a significant characteristic earthquake component as well as whether large triggered events can nucleate from within the rupture zone of the mainshock because ucerf3 etas has many sources of uncertainty as will any subsequent version or competing model potential usefulness needs to be considered in the context of actual applications electronic supplement 1 figures showing discretization verification of the distancedecaycubesampler average simulated participation rate and average cumulative magnitude frequency distributions mfds 1 http www bssaonline org lookup suppl doi 10 1785 0120160173 dc1

characteristics of the great whale river plume observations of the motion field and dilution effects associated with the plume of great whale river in hudson bay are presented for both open water and ice covered conditions in the summer months a distinct plume of about 100 km2 in area is formed offshore which is characterized by a 1 2 m thickness and large velocities directed away from the river mouth in contrast to slower currents parallel to the shore in the ambient waters underneath surface drifter results suggest that the outer boundary of plume may be a zone of frontal convergence under ice covered conditions the plume was significantly thicker and extended much farther offshore in spite of a marked reduction in river runoff at this time

layer outcropping in numerical models of stratified flows abstract layered models of stratified flow are favored by theoreticians because of their conceptual simplicity but have only seen limited use in numerical modeling due to difficulties related to layer outcropping vanishing layer depth two mass transport schemes capable of handling outcropping are tested against analytic solutions describing wind and buoyancy forced flow in a two and three layer ocean in both cases the model is found to closely reproduce the available analytic solutions this result helps alleviate longstanding reservations about the severity of the outcrop problem in layer models

seismicity at the volcanoes of katmai national park alaska july 1995 december 1997 abstract upper crustal seismicity located within katmai national park occurs mainly within four distinct clusters originating near martin mageik mm subnet volcanoes trident volcano katmai caldera and snowy volcano analyses of earthquake frequency magnitude distributions reveal high b values beneath mm subnet 1 5 normal b values at trident volcano 1 0 and intermediate b values at katmai caldera 1 3 for all seismicity occurring between july 1995 and december 1997 detailed analyses of subsets of b values and hypocenter locations at mm subnet reveal a temporal increase in b value associated with an increase in the maximum depth of seismicity the changes occurred during a shallow earthquake swarm beneath mageik volcano between october 16 and 25 1996 and again in november december 1997 before the swarm the weighted least squares b value was 1 01 at mm subnet increased to 1 59 during the swarm and remained anomalously high until april 1997 the corresponding maximum depth of seismicity is generally less than 5 km for well located earthquakes occurring after september 18 1996 but shifted to 10 km during both the october 1996 swarm and the november december 1997 period the november december 1997 event is not associated with an increase in the rate of seismicity or the b value the october 1996 swarm had a cumulative moment release of 5 0 10 20 dyn cm and decayed from a peak rate of 110 events per day with a modified omori law p value of 1 06 0 11 modelling by the flow law with a 10 km depth limit for seismicity suggests that temperature gradients are on the order of 20 40 c km 1 in agreement with the p value estimate we infer that a simple pressurizing intrusion was not associated with the october swarm because higher stresses should increase seismicity and lower the b value the opposite of what we observed alternatively an actively degassing intrusion would reduce the effective stress and increase the b value at shallow depths while the increased stress would induce seismicity at depth surface temperature measurements taken at the mageik crater lake in july 1995 and again in july 1997 revealed an increase of about 10 c in the lake water temperature consistent with a degassing intrusive event

observations at the tidal plume front of a high volume river outflow 1 we present shipboard observations of very strong convergence vertical velocities and mixing and near bed impacts associated with the leading edge front of the tidally pulsed columbia river plume with upwelling favorable winds and riverflow of 4900 m3s 1 the plume propagates as a buoyant gravity current with a rotary bore like vertical frontal circulation and downwelling as strong as 0 35 m s 1 in waters as deep as 65 m near bed currents intensify to as much as 1 0 m s 1 after frontal passage and are often associated with elevated acoustic backscatter mixing is locally strong with an eddy diffusivity of o 0 2 m2s 1 50 m behind the front and t s diagrams imply plume mixing with 10 m deep ocean water these observations indicate that the leading edge front of a surface advected plume can cause exchanges of a nutrients between cold subsurface shelf waters and the river plume and b nutrients and sediments across the sediment water interface

estimating the quality of landslide susceptibility models we present a landslide susceptibility model for the collazzone area central italy and we propose a framework for evaluating the model reliability and prediction skill the landslide susceptibility model was obtained through discriminant analysis of 46 thematic environmental variables and using the presence of shallow landslides obtained from a multi temporal inventory map as the dependent variable for statistical analysis by comparing the number of correctly and incorrectly classified mapping units it is established that the model classifies 77 0 of 894 mapping units correctly model fitting performance is investigated by comparing the proportion of the study area in each probability class with the corresponding proportion of landslide area we then prepare an ensemble of 350 landslide susceptibility models using the same landslide and thematic information but different numbers of mapping units this ensemble is exploited to investigate the model reliability including the role of the thematic variables used to construct the model and the model sensitivity to changes in the input data by studying the variation of the model s susceptibility estimate the error associated with the susceptibility assessment for each mapping unit is determined this result is shown on a map that complements the landslide susceptibility map prediction skill of the susceptibility model is then estimated by comparing the forecast with two recent event inventory maps the susceptibility model is found capable of predicting the newly triggered landslides a general framework for testing a susceptibility model is proposed including a scheme for ranking the quality of the susceptibility assessment

decay of aftershock density with distance does not indicate triggering by dynamic stress the most predictable earthquakes are aftershocks which invariably follow mainshocks so what triggers aftershocks it was recently argued controversially that the decay of aftershocks with distance from the main earthquake could only be explained by dynamic triggering keith richards dinger and colleagues have tested this hypothesis and conclude that the observed decay can be better explained by static triggering resolving whether static or dynamic stress triggers most aftershocks and subsequent mainshocks is essential to understand earthquake interaction and to forecast seismic hazard it has recently been argued that the decay of aftershocks with distance from the main earthquake could be explained only by dynamic triggering this hypothesis has now been tested the conclusion being that the observed decay can be better explained by static triggering resolving whether static1 2 3 or dynamic4 5 6 7 8 stress triggers most aftershocks and subsequent mainshocks is essential to understand earthquake interaction and to forecast seismic hazard9 felzer and brodsky10 examined the distance distribution of earthquakes occurring in the first five minutes after 2 m 3 and 3 m 4 mainshocks and found that their magnitude m 2 aftershocks showed a uniform power law decay with slope 1 35 out to 50 km from the mainshocks from this they argued that the distance decay could be explained only by dynamic triggering here we propose an alternative explanation for the decay and subject their hypothesis to a series of tests none of which it passes at distances more than 300 m from the 2 m 3 mainshocks the seismicity decay 5 min before the mainshocks is indistinguishable from the decay five minutes afterwards indicating that the mainshocks have no effect at distances outside their static triggering range omori temporal decay the fundamental signature of aftershocks is absent at distances exceeding 10 km from the mainshocks finally the distance decay is found among aftershocks that occur before the arrival of the seismic wave front from the mainshock which violates causality we argue that felzer and brodsky10 implicitly assume that the first of two independent aftershocks along a fault rupture triggers the second and that the first of two shocks in a creep or intrusion driven swarm triggers the second when this need not be the case

foreshock occurrence rates before large earthquakes worldwide global rates of foreshock occurrence involving shallow m 6 and m 7 mainshocks and m 5 foreshocks were measured using earthquakes listed in the harvard cmt catalog for the period 1978 1996 these rates are similar to rates ones measured in previous worldwide and regional studies when they are normalized for the ranges of magnitude difference they each span the observed worldwide rates were compared to a generic model of earthquake clustering which is based on patterns of small and moderate aftershocks in california and were found to exceed the california model by a factor of approximately 2 significant differences in foreshock rate were found among subsets of earthquakes defined by their focal mechanism and tectonic region with the rate before thrust events higher and the rate before strike slip events lower than the worldwide average among the thrust events a large majority composed of events located in shallow subduction zones registered a high foreshock rate while a minority located in continental thrust belts measured a low rate these differences may explain why previous surveys have revealed low foreshock rates among thrust events in california especially southern california while the worldwide observations suggest the opposite california lacking an active subduction zone in most of its territory and including a region of mountain building thrusts in the south reflects the low rate apparently typical for continental thrusts while the worldwide observations dominated by shallow subduction zone events are foreshock rich

synthetic aperture radar imaging of upper ocean circulation features and wind fronts a sharp transition from dark to brighter backscatter regions the corresponding profiles of backscatter modulation across these features are expressed by a peak of about 2 db in contrast to a steplike increase of 5 8 db this suggests that sar image expressions of upper ocean circulation features and wind fronts can be distinguished and classified on the basis of this classification we attempt to quantify the dominating marine geophysical variables this method for systematic interpretation of sar images should be further validated with the use of airborne or satellite data such as from the first

comparison of rockfall susceptibility assessment at local and regional scale a case study in the north of beijing china this study shows a rockfall susceptibility assessment at local scale in north beijing of china including the identification of rockfall sources onsite by terrain and rock discontinuities analysis and run out distance prediction by rocfall simulation two types of rockfall were defined including one type on the cliffs with long inclined slopes and another type on the road slopes with low height two historical rockfall events were used to back calibrating the parameters used for run out distance simulation based on the work rockfall susceptibility map at local scale was created in gis which was compared with the map obtained at regional scale entire huairou district scale due to the difference of approaches applied procedure of assessment and types of source data acquired the two resulting rockfall susceptibility maps are proved to be different still both of them are useful and could be used at different level s decision for rockfall prevention and mitigation different types of uncertainties exist in the study of rockfall susceptibility assessment to reduce the uncertainties studies on both approaches and techniques are suggested

comparing landslide inventory maps landslide inventory maps are effective and easily understandable products for both experts such as geomorphologists and for non experts including decision makers planners and civil defense managers landslide inventories are essential to understand the evolution of landscapes and to ascertain landslide susceptibility and hazard despite landslide maps being compiled every year in the word at different scales limited efforts are made to critically compare landslide maps prepared using different techniques or by different investigators based on the experience gained in 20 years of landslide mapping in italy and on the limited literature on landslide inventory assessment we propose a general framework for the quantitative comparison of landslide inventory maps to test the proposed framework we exploit three inventory maps the first map is a reconnaissance landslide inventory prepared for the umbria region in central italy the second map is a detailed geomorphological landslide map also prepared for the umbria region the third map is a multi temporal landslide inventory compiled for the collazzone area in central umbria results of the experiment allow for establishing how well the individual inventories describe the location type and abundance of landslides to what extent the landslide maps can be used to determine the frequency area statistics of the slope failures and the significance of the inventory maps as predictors of landslide susceptibility we further use the results obtained in the collazzone area to estimate the quality and completeness of the two regional landslide inventory maps and to outline general advantages and limitations of the techniques used to complete the inventories

predictions of the 1997 strong earthquakes in jiashi xinjiang china abstract a sequence of strong earthquakes occurred in jiashi county xinjiang china 40 n 77 e population 280 000 in 1997 after a 10 month quiescence following a m s 6 9 earthquake on 19 march 1996 in the same area from 21 january 1997 through 18 october 1997 15 earthquakes occurred with m s 5 0 seven of which with m s 6 0 such sequences of strong earthquakes are rare around the world but have occurred six times in the land area of china during this century of the 15 m s 5 0 earthquakes in the jiashi sequence eight fell within the predicted 7 day time windows of a total of 8 short term and imminent stage predictions but the initial shocks of the sequence january 21 m s 6 4 6 3 were not predicted three of the eight predictions made were not fulfilled one of which was announced to the public a false alarm four of the remaining five predictions were acted on by local authorities and the public was notified 2 5 h to 4 days before the earthquakes which caused no deaths one earthquake april 11 m s 6 6 struck 30 min after the prediction was made but before action could be taken by the local authorities and it caused nine deaths these predictions were based on composite observations of precursory anomalies in seismicity electromagnetic fields and crustal deformation which were in turn compiled over the past 30 years in a nationwide earthquake monitoring program examples of precursory anomalies include 1 a clear seismicity pattern of quiescence intensification main shock s was observed for the april 6 earthquakes m s 6 3 6 4 which was previously applied to the prediction of the well known 1975 haicheng earthquake in laoning china 2 distinct decreases in b values preceded the earthquakes on march 1 m s 6 0 and april 6 m s 6 3 6 4 3 anomalous variation of geomagnetic vertical component preceded the april 6 earthquakes m s 6 3 6 4 4 sudden decreases in borehole strain preceded 8 of the earthquakes

estuary plumes and fronts in shelf waters a layer model abstract a layer model that treats fronts as discontinuities is developed to study the steady state behavior of shallow estuary plumes on the continental shelf the complete range of earth rotation effect is evaluated from small scale or nonrotating plumes kelvin number equal zero to large scale rotating plumes kelvin number equal order one supercritical flow is assumed in the outlet channel and the method of characteristics is used to compute the flow downstream nonrotating plumes have strong boundary fronts and concentrate their greatest layer depth and mass transport offshore near the front but form no coastal current rotating plumes have boundary fronts that weaken soon after discharge form a turning region where coriolis action deflects the flow toward shore and subsequently set up a coastal current soon after its formation this coastal current is bounded offshore by a strong front called the coastal front across which the momentum balance changes from nearly inertial in the turning regi

immediate and updated forecasting of aftershock hazard 1 it is well known that the detection rate of aftershocks is extremely low during the period immediately after a large earthquake due to the contamination of arriving seismic waves this has led to considerable difficulties in obtaining estimates of the empirical laws of aftershock decay and magnitude frequency immediately after main shocks this paper presents an estimation method for predicting the underlying occurrence rate of aftershocks of any magnitude range based on a magnitude frequency model that combines the gutenberg richter law with the detection rate function this procedure enables real time probability forecasting of aftershocks immediately after the mainshock when the majority of large aftershocks are likely to occur

on the determination of characteristics of the interior ocean dynamics from radar signatures of internal solitary waves in this paper we discuss two different methods of inferring characteristics of the interior ocean dynamics from radar signatures of internal solitary waves visible on synthetic aperture radar sar images the first one consists in the recognition and the interpretation of sea surface patterns of internal solitary waves the second one consists in the analysis of the modulation depth of the normalized radar backscattering cross section nrcs associated with internal solitary waves for this purpose we consider a data set composed of sar and in situ measurements carried out from 1991 to 1997 in the region of the strait of messina the recognition and the interpretation of sea surface patterns of internal solitary waves in the strait of messina can be used to study characteristics of the density distribution in the area the internal wave field varies with seasonal variations in the vertical density stratification and with remotely induced variations i e variations induced by the larger scale circulation in the horizontal density distribution in order to inquire into the possibility of inferring parameters of the interior ocean dynamics by analyzing the modulation of the nrcs associated with internal solitary waves several numerical simulations are carried out using a radar imaging model these simulations are performed by assuming different wind conditions and internal wave parameters it is shown that an accurate knowledge of wind conditions is crucial for deriving internal wave parameters and hence parameters of the interior ocean dynamics from the modulation of measured nrcs associated with internal solitary waves

study of a rockfall in a limy conglomerate canyon covarrubias burgos n spain in this paper a rockfall of some tenths of cubic metres of rock occurred in a conglomerate canyon in the northern castilian plateau n central spain is described in detail this includes the basic data geology mapping meteorological data and rock involved the mechanical mechanism of the instability the propagation and reach of the fallen rock boulders and the final location of the pieces the study is based on detailed geological aerial photography and geotechnical studies and advance topographical measurements geological engineering techniques are used to analyze the instability initiation and rockfall propagation this study contributes to a better understanding of the geological processes leading to the occurrence of calcareous canyons and cliffs in the drainage network of the upper castilian plateau it is also helpful to improve our knowledge on natural rockfall phenomena for risk engineering purposes aiming to quantify control and mitigate associated hazards

an improved composite surface model for the radar backscattering cross section of the ocean surface 2 model response to surface roughness variations and the radar imaging of underwater bottom topography in the companion paper we have presented an improved composite surface model for the calculation of normalized radar backscattering cross sections nrcs of the ocean surface the proposed model accounts for the impact of the full two dimensional ocean wave spectrum on the radar backscatter and was shown to reproduce measured absolute nrcs values for a variety of radar configurations and wind speeds satisfactorily after some reasonable tuning of the input ocean wave spectrum this paper focuses on the modulation of the nrcs in the presence of spatially varying surface currents first the sensitivity of the nrcs to intensity variations of different ocean wave spectral components is investigated then the hydrodynamic modulation of the wave spectrum over underwater bottom topography in tidal waters is computed in different ways and the resulting radar signatures are discussed the composite surface model yields comparable radar signatures at high 10 ghz x band and low 1 ghz l band radar frequencies which is in much better agreement with experimental results than the predictions of a first order bragg scattering model on the other hand measured variations of the nrcs at high radar frequencies appear to be still underestimated in some cases which may be due to shortcomings of our description of the wave current interaction by conventional weak hydrodynamic interaction theory possible improvements of the theory are discussed and requirements for future experiments are formulated

analysis of relaxation temporal patterns in greece through the retas model approach the temporal decay of eight aftershock sequences in the area of greece after 1975 was examined with main shocks magnitudes of mw 6 6 the analysis was done through the restricted epidemic type aftershock sequence retas stochastic model which enables the possibility to recognize the prevailing clustering pattern of the relaxation process in the examined areas in four of the cases the analysis selected the epidemic type aftershock sequence etas model to offer the most appropriate depiction of the aftershock temporal distribution which presumes that all shocks to the smallest ones in the sample can cause secondary aftershocks while for the rest of the sequences triggering potential seems to have aftershocks above a certain magnitude threshold retas model and they are expected to induce secondary activity the models developed on aftershock data were also applied to forecast real seismicity after the conclusion of the aftershock sequences for four out of eight cases we obtained promising estimations of ensuing seismicity after the end of the sequences with models based only on aftershock data some features of the retas model simulation were also studied like simulating magnitudes revealing that it is reasonable to consider in the model the temporal behavior of the aftershocks magnitudes as well stochastic modeling was also applied to estimate the duration of the relaxation process assuming that the end of each sequence is marked by the divergence of real seismicity from the modified omori formula mof model the latter known to represent pure aftershock activity the obtained results give an indication that possibly low stressing rate results in longer duration of the relaxation process in a region 2007 elsevier b v all rights reserved

landslide susceptibility mapping in the damrei romel area cambodia using frequency ratio and logistic regression models this study applied tested and compared a probability model a frequency ratio and statistical model a logistic regression to damre romel area cambodia using a geographic information system for landslide susceptibility mapping landslide locations were identified in the study area from interpretation of aerial photographs and field surveys and a spatial database was constructed from topographic maps geology and land cover the factors that influence landslide occurrence such as slope aspect curvature and distance from drainage were calculated from the topographic database lithology and distance from lineament were extracted and calculated from the geology database land cover was classified from landsat tm satellite imagery the relationship between the factors and the landslides was calculated using frequency ratio and logistic regression models the relationships frequency ratio and logistic regression coefficient were overlaid to make landslide susceptibility map then the landslide susceptibility map was compared with known landslide locations and tested as the result the frequency ratio model 86 97 and the logistic regression 86 37 had high and similar prediction accuracy the landslide susceptibility map can be used to reduce hazards associated with landslides and to land cover planning

landslide susceptibility mapping for a landslide prone area findikli ne of turkey by likelihood frequency ratio and weighted linear combination models landslides are very common natural problems in the black sea region of turkey due to the steep topography improper use of land cover and adverse climatic conditions for landslides in the western part of region many studies have been carried out especially in the last decade for landslide susceptibility mapping using different evaluation methods such as deterministic approach landslide distribution qualitative statistical and distribution free analyses the purpose of this study is to produce landslide susceptibility maps of a landslide prone area findikli district rize located at the eastern part of the black sea region of turkey by likelihood frequency ratio lrm model and weighted linear combination wlc model and to compare the results obtained for this purpose landslide inventory map of the area were prepared for the years of 1983 and 1995 by detailed field surveys and aerial photography studies slope angle slope aspect lithology distance from drainage lines distance from roads and the land cover of the study area are considered as the landslide conditioning parameters the differences between the susceptibility maps derived by the lrm and the wlc models are relatively minor when broad based classifications are taken into account however the wlc map showed more details but the other map produced by lrm model produced weak results the reason for this result is considered to be the fact that the majority of pixels in the lrm map have high values than the wlc derived susceptibility map in order to validate the two susceptibility maps both of them were compared with the landslide inventory map although the landslides do not exist in the very high susceptibility class of the both maps 79 of the landslides fall into the high and very high susceptibility zones of the wlc map while this is 49 for the lrm map this shows that the wlc model exhibited higher performance than the lrm model