the 1986 kalamata south peloponnesus earthquake detailed study of a normal fault evidences for east west extension in the hellenic arc tectonic and seismological data collected in the field following the september 13 1986 kalamata earthquake south peloponnesus are presented and analyzed to discuss the earthquake rupture process and the regional tectonics the event occurred on the kalamata normal fault whose trace was mapped with spot images and topographic and field observations this fault is part of an approximately nnw sse en echelon system cutting through the hellenic nappes the fault striking n15 e on the average with a dip of about 50 has a minimum cumulated quaternary throw of the order of 1 km the measured coseismic slip is 6 18 cm over a length of 6 km the main shock focal mechanism obtained from long period waveform modeling strike 201 10 20 dip 45 5 rake 283 10 25 represents almost pure east west extension and is in good agreement with tectonic observations the centroid depth is constrained to 5 3 km and the seismic moment to 7 0 2 5 1017 n m over 700 aftershocks located by a 16 station network installed after the earthquake for a period of 2 weeks define two clusters separated by a gap of aftershock activity from the surface to a depth of about 10 km the main cluster to the south defines a 45 west dipping plane which lies on the downward extension of the fault mapped at the surface focal mechanisms of aftershocks on this fault plane are homogeneous and represent e w extension as the main shock in contrast the majority of focal mechanisms in the uppermost part of the foot wall show more or less e w compression probably corresponding to postseismic stress release the northern cluster of aftershocks is very dense and located away from the surface rupture within a relay zone between the kalamata and the next en echelon faults to the nw the thouria faults there focal mechanisms represent extension from about n115 to n70 and n20 corresponding mostly to fault reactivation in an area where nonrigid deformations prevail the main shock probably initiated in this relay zone 3 4 s before the rupture front reached the main fault plane and released most of the energy there the rupture presumably propagating southward the focal mechanism of the kalamata earthquake and that of the april 27 1965 earthquake located to the northwest of crete as well as the regional active normal fault pattern imply that e w extension oblique to the hellenic arc is presently the dominant tectonic regime e w stretching occurs partly on reactivated nw se faults parallel to the hellenic structures but mostly on newly formed n s normal faults across those structures the latter faults are responsible for the apparent segmentation of the hellenic belt from southern peloponnesus to crete the existence of active e w extension in this region implies a recent change in the tectonic regime and consequently a change in boundary conditions at the subduction zone probably in response to the incoming margin of africa

earthquake mechanisms of the adriatic sea and western greece implications for the oceanic subduction continental collision transition summary we present 21 focal solutions magnitude 5 5 reliably computed by body wave modelling for the western hellenic arc from yugoslavia to the southern peloponnese mechanisms located within the aegean show normal faulting the t axis trending n s in the centre and parallel to the active boundary in the external part mechanisms associated with the keffalinia fault are consistent with dextral strike slip motion reverse mechanisms located along the active boundary are remarkably consistent and do not depend on the nature of the active boundary continental collision or oceanic subduction the consistency in azimuth of the slip vectors and of the gps velocity relative to africa all along the active boundary suggests that the deformation is related to the same motion the discrepancy between seismic energy release and the amount of shortening confirms that the continental collision is achieved by seismic slip on faults but the oceanic subduction is partially aseismic the northward decrease in velocity between continental collision and oceanic subduction suggests the continental collision to be a recent evolution of the active subduction

flow characteristics of large eruption triggered debris flows at snow clad volcanoes constraints for debris flow models abstract theoretical modelling is not yet adequate to predict the behavior of debris flows which can be an extremely hazardous hydrologic process commonly associated with volcanic eruptions particularly at snow clad stratovolcanoes to provide a realistic basis for modelling the behavior of large 1000 m3 s debris flows this paper summarizes kinematic volumetric and hydraulic characteristics of ten large historic volcanic debris flows from four different volcanoes although debris flows larger than these are known to have occurred in the past the ten summarized here define a practical upper range in magnitude of more typical flows to be considered for future hazard prediction peak flow velocities of the ten debris flows studied were indirectly measured to be between about 5 and 20 m s on gradients of 0 005 to 0 25 m m but locally they were as great as 40 m s hydraulic average depths were as great as 25 m but were more commonly between 5 and 15 m in channels up to 400 m wide computed peak discharges volumetric flow rates were as high as 105 m3 s and total volumes were as much as 108 m3 total flow volumes increased by as much as four times in relatively steep channels as eroded sediment was incorporated into the debris flows flows generally achieved supercritical flow and deposited minimal volumes of sediment on gradients steeper than 0 02 m m subcritical flow and active deposition predominated on gradients less than 0 01 m m although flows travelled tens of kilometers on such low gradients while laying down deposits total distances travelled as debris flows were as far as 120 km

active deformation of a segment of arc the strait of kythira hellenic arc greece abstract a field analysis of late cenozoic faults has been carried out in the southwest hellenic arc on the islands of kythira and antikythira as well as on both sides of the strait in southeast peloponnisos and western crete the previously unknown geological structure of antikythira is briefly described together with accurate bathymetric data obtained using a multi beam echo sounder on submarine fault scarps the results of studies on land lead to a new interpretation of the neotectonic deformation of this segment of the hellenic arc the submersion of the strait is a consequence of extension related to normal faulting the extension rate being faster than in adjacent segments of the arc the direction of extension related to late pliocene quaternary normal faulting is determined from on land information the existence of oblique en echelon normal faults indicates that dextral deformation plays a role within the kythira strait in connection with the opening of the adjacent cretan sea triggered by subduction beneath the hellenic arc the whole pattern of fault systems in southeast peloponnisos as inferred from teledetection and field studies is consistent with the clockwise rotation that has been independently proposed and verified by palaeomagnetic studies the kythira strait thus provides an example of a complex transform extensional deformation and rotation between two major segments of external arc

two dimensional water flood and mudflow simulation flo 2d is a two dimensional finite difference model that simulates clear water flood hazards mudflows and debris flows on alluvial fans and urban floodplains interactive flood or mudflow routing between channel street and floodplain flow is performed using a uniform grid system to describe complex floodplain topography a quadratic rheological model developed from field and laboratory mudflow data enables appropriate simulations of flooding conditions ranging from clear water to hyperconcentrated sediment flows computer aided design cad graphics of predicted time sequenced flood depths automates the delineation of flood hazards replication of the 1983 rudd creek mudflow in utah demonstrates the capability of the model

the role of the sediment budget in understanding debris flow susceptibility this study proposes a sediment budget model to predict the temporal variation of debris volume stored in a debris flow prone watershed the sediment budget is dominated by shallow landslides and debris outflow the basin topography and the debris volume stored in the source area of the debris flow prone watershed help evaluating its debris flow susceptibility the susceptibility model is applied to the tungshih area of central western taiwan the importance of the debris volume in predicting debris flow susceptibility is reflected in the standardized coefficients of the proposed statistical discriminant model the high prediction rate 0 874 for the occurrence of debris flows justifies the capability of the proposed susceptibility models to predict the occurrence of debris flows this model is then used to evaluate the temporal evolution of the debris flow susceptibility index the analysis results show that the numbers of watershed which are classified as a debris flow group correspond well to storage of sediment at different time periods these numbers are 10 before the occurrence of chi chi earthquake 13 after the occurrence of chi chi earthquake 16 after the occurrence of landslides induced by typhoon mindulle typhoon m and 14 after the occurrence of debris flows induced by typhoon m it indicates that the occurrence of 7 6 chi chi earthquake had significant impact on the debris flow occurrence during subsequent typhoons copyright 2009 john wiley sons ltd

active crustal deformation from the azores triple junction to the middle east the co seismic crustal deformation along the africa eurasia eurasia arabia plate boundary from the azores triple junction 30 w up to the karliova triple junction 41 e is examined based on the moment tensor summation of mainly post 1964 earthquakes with ms 5 0 strain rates range from 10 8 yr to 10 6 yr while values exceeding 10 7 yr were calculated for the back arc aegean area and for the north anatolian fault zone a remarkable stability in the azimuth of the component of compression and of extension is observed in the area that extends west of italy 17 e up to the azores triple junction along this region the deformation is taken up by compression along a mean direction of n140 with rates from 1 1 to 2 8 mm yr and by extension along a mean direction of n50 with rates from 2 4 to 12 0 mm yr at the gloria fault and in the surrounding area dextral strike slip motion occurs at a rate of 11 mm yr from sicily up to the eastern end of the hellenic arc the crust is compressed at azimuths in the range n20 n31 with an average value of 26 5 this compression is occurring at a rate of 1 21 mm yr with an average value of 9 8 mm yr in the back arc aegean area extension is occurring along a mean azimuth of n156 with a rate of 5 2 3 8 mm yr the average shortening rate along the convex side of the hellenic arc is 12 mm yr from the eastern end of the north anatolian fault 41 e up to the northern aegean trough extension along n68 n179 and compression along n158 n89 occurs which results in dextral strike slip motion the rate of extension reduces from east to west from 30 mm yr to 5 mm yr while the rate of compression reduces from 17 mm yr to 5 mm yr the northwards motion of arabia results in a n31 trending compression at a rate of 7 mm yr along the east anatolian fault zone

travel times of pn waves in the aegean and surrounding area summary based on accurately located 23 very shallow earthquakes h 1 14 km in northern and central greece by portable networks of seismic stations and by the joint epicentre method the travel times of the p waves from the foci of these earthquakes to the sites of 54 permanent stations in the balkan region have been determined the travel times of p waves in the central and eastern part of the area eastern greece south eastern yugoslavia the aegean sea bulgaria southern romania western turkey fit a straight line very well with the p velocity equal to 7 9 f 0 1 km s on the contrary the travel times of p waves to stations in the western part of the area albania western greece do not fit this curve because the p waves travelling to these stations are delayed by more than 1 s due to the thicker crust under the dinarides hellenides mountain range time delays for p waves have been calculated for each permanent station in the balkan area with respect to the mean travel time curve of these waves in the central and eastern part of the area corrections of the travel times for these delays contribute very much to the improvement of the accuracy in the location of the shallow earthquakes in the aegean and surrounding area

flow of variably fluidized granular masses across three dimensional terrain 2 numerical predictions and experimental tests numerical solutions of the equations describing flow of variably fluidized coulomb mixtures predict key features of dry granular avalanches and water saturated debris flows measured in physical experiments these features include time dependent speeds depths and widths of flows as well as the geometry of resulting deposits three dimensional 3 d boundary surfaces strongly influence flow dynamics because transverse shearing and cross stream momentum transport occur where topography obstructs or redirects motion consequent energy dissipation can cause local deceleration and deposition even on steep slopes velocities of surge fronts and other discontinuities that develop as flows cross 3 d terrain are predicted accurately by using a riemann solution algorithm the algorithm employs a gravity wave speed that accounts for different intensities of lateral stress transfer in regions of extending and compressing flow and in regions with different degrees of fluidization field observations and experiments indicate that flows in which fluid plays a significant role typically have high friction margins with weaker interiors partly fluidized by pore pressure interaction of the strong perimeter and weak interior produces relatively steep sided flat topped deposits to simulate these effects we compute pore pressure distributions using an advection diffusion model with enhanced diffusivity near flow margins although challenges remain in evaluating pore pressure distributions in diverse geophysical flows riemann solutions of the depth averaged 3 d coulomb mixture equations provide a powerful tool for interpreting and predicting flow behavior they provide a means of modeling debris flows rock avalanches pyroclastic flows and related phenomena without invoking and calibrating rheological parameters that have questionable physical significance

a comparison of pyroclastic flow and debris avalanche mobility many pyroclastic flows have runout distances longer than expected from basic frictional arguments in these cases the ratio of the height descended h and the runout l are as small as 0 2 a feature which has been attributed to fluidization however significant fluidization by gases is now considered unlikely during emplacement of debris avalanches where h l and volume are inversely related we determine whether pyroclastic flows are more mobile than debris avalanches of the same volume and if different emplacement mechanisms are needed to describe their runout h l and volume data were compiled for 34 nonvolcanic and 40 volcanic debris avalanche deposits as well as 15 pyroclastic flow deposits systematic differences in the volume versus h l plots were explored by statistical analysis results show an inverse relationship between h l and volume for both nonvolcanic and volcanic debris avalanche deposits as expected and also for pyroclastic flow deposits regression lines for plots of pyroclastic flow and volcanic debris avalanche data are statistically indistinguishable and the non volcanic debris avalanche line is parallel to the other two we argue that the nonvolcanic and volcanic debris avalanche differences are due to material properties rather than emplacement mechanisms therefore since pyroclastic flows and volcanic debris avalanches have indistinguishable h l versus volume it is unlikely that pyroclastic flows have a significantly different primary emplacement mechanism based on the data in hand we conclude that it is unnecessary to invoke gas fluidization to explain the mobility of the types of pyroclastic flows examined or the excess runout of large volume debris avalanches

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

triggering and predisposing factors for flow like landslides in pyroclastic soils the case study of the lattari mts southern italy abstract shallow flowslides debris flows and debris avalanches are rainfall induced landslides consisting in the shear failure of few metres of soils or in some cases even less than a metre which greatly increase downslope in volume and flow velocity the southern italian region of campania has been historically affected by such events involving pyroclastic soils mainly resting on steep carbonate slopes this paper deals with the analysis of factors influencing the occurrence of flow like landslides adopting the lattari mts in campania as a case study the results of two investigation campaigns carried out in the area allowed effective large scale geological and geotechnical characterization to be set up stratigraphic profiles mean physical properties and typical friction angles at the critical state for each soil layer were investigated the effect of suction on peak and critical shear strength whose drop is responsible for soil failure was analysed using detailed information on both the stratigraphic and geotechnical features of the soils involved in past flow like landslides typical triggering models were selected representing locally recurrent geomorphologic conditions at the basin scale the identified models were adopted for slope stability analyses carried out on four cross sections of flowslides occurring prior to the event to back analyse the triggering conditions from the evidence on the triggering mechanisms and the results of analyses the infinite slope approach is not always suitable to model slope stability conditions properly because the onset of landslides is also affected by local topographic and stratigraphic factors

the m w 6 7 12 october 2013 western hellenic arc main shock and its aftershock sequence implications for the slab properties the 12 october 2013 m w6 7 earthquake offshore crete island is one of the few strong earthquakes to have occurred in the last few decades in the southwestern part of the hellenic subduction zone hsz providing the opportunity to evaluate characteristics of the descending slab the hsz has experienced several strong m 7 0 earthquakes in historical times with the largest one being the 365 ad m w 8 4 earthquake the largest known ever occurred in the mediterranean region the 2013 main shock occurred in close proximity with the 365 event on an interplate thrust fault at a depth of 26 km onto the coupled part of the overriding and descending plates gcmt solution shows a slightly oblique rake 130 thrust faulting with downdip compression on a nearly horizontal dip 3 northeast dipping fault plane with strike 340 parallel to the subduction front with the compression axis being oriented in the direction of plate convergence the subduction interface can be more clearly resolved with the integration of aftershock locations and cmt solution for this scope the aftershocks were relocated after obtaining a v p v s ratio equal to 1 76 a one dimensional velocity model and time delays that approximate the velocity structure of the study area and the employment of double difference technique for both phase pick data and cross correlation differential times the first day relocated seismicity alike aftershocks in the first 2 months shows activation of an area at the upper part of the descending slab with most activity being concentrated between 13 and 27 km where the main shock is also encompassed aftershocks are rare near to the main shock implying homogeneous slip on a large patch of the rupture plane based on the aftershock distribution the size of the activated area estimated is about 24 km long and 17 km wide coulomb stress changes resolved for transpressive motion reveal negligible off fault aftershock triggering evidencing a comparatively stable regime in the downdip part of the slab or different fault mechanism

debris flow release processes investigated through the analysis of multi temporal lidar datasets in north western iceland debris flows are fast moving gravity flows of poorly sorted rock and soil mixed and saturated with water debris flow initiation has been studied using empirical and experimental modelling but the geomorphic changes indicative of different triggering processes are difficult to constrain with field observations only we identify signatures to distinguish two different debris flow release styles by integrating high resolution multi temporal remote sensing datasets and morphometric analysis we analyse debris flows sourced above the town of isafjor ur iceland two debris flow triggering processes were previously hypothesized for this site i slope failure characterised by landslides evolving into debris flows and ii the fire hose effect in which debris accumulated in pre existing steep sided bedrock passages is transported by a surge of water it is unknown which process dominates and determines the local risk to investigate this question we compare airborne lidar elevation models and aerial photographs collected in 2007 with similar data from 2013 we find that two new debris flow tracks were created by slope failures these are characterised by steep sliding surfaces and lateral leveed channels slope failure also occurred in two large recently active tracks creating the preparatory conditions for the fire hose effect to mobilise existing debris these tracks show alternating zones of fill and scour along their length and debris stored below the source area at rest angles 35 our approach allows us to identify and quantify the morphological changes produced by slope failure release process which generated the preparatory conditions for the fire hose effect as debris flows are rarely observed in action and morphological changes induced by them are difficult to detect and monitor the same approach could be applied to other landscapes to understand debris flow initiation in absence of other monitoring information and can improve the identification of zones at risk in inhabited areas near hillslopes with potential for debris flows

flow of variably fluidized granular masses across three dimensional terrain 1 coulomb mixture theory rock avalanches debris flows and related phenomena consist of grain fluid mixtures that move across three dimensional terrain in all these phenomena the same basic forces govern motion but differing mixture compositions initial conditions and boundary conditions yield varied dynamics and deposits to predict motion of diverse grain fluid masses from initiation to deposition we develop a depth averaged three dimensional mathematical model that accounts explicitly for solid and fluid phase forces and interactions model input consists of initial conditions path topography basal and internal friction angles of solid grains viscosity of pore fluid mixture density and a mixture diffusivity that controls pore pressure dissipation because these properties are constrained by independent measurements the model requires little or no calibration and yields readily testable predictions in the limit of vanishing coulomb friction due to persistent high fluid pressure the model equations describe motion of viscous floods and in the limit of vanishing fluid stress they describe one phase granular avalanches analysis of intermediate phenomena such as debris flows and pyroclastic flows requires use of the full mixture equations which can simulate interaction of high friction surge fronts with more fluid debris that follows special numerical methods described in the companion paper are necessary to solve the full equations but exact analytical solutions of simplified equations provide critical insight an analytical solution for translational motion of a coulomb mixture accelerating from rest and descending a uniform slope demonstrates that steady flow can occur only asymptotically a solution for the asymptotic limit of steady flow in a rectangular channel explains why shear may be concentrated in narrow marginal bands that border a plug of translating debris solutions for static equilibrium of source areas describe conditions of incipient slope instability and other static solutions show that nonuniform distributions of pore fluid pressure produce bluntly tapered vertical profiles at the margins of deposits simplified equations and solutions may apply in additional situations identified by a scaling analysis assessment of dimensionless scaling parameters also reveals that miniature laboratory experiments poorly simulate the dynamics of full scale flows in which fluid effects are significant therefore large geophysical flows can exhibit dynamics not evident at laboratory scales

a procedure for modelling shallow dislocation sources summary expressions for displacements on the surface of a layered half space due to an arbitrary oriented shear dislocation are given in terms of generalized ray expansions useful approximations of these expressions for shallow events as recorded at teleseismic distances for realistic earth models are presented the results of this procedure are used to generate synthetic p sv and sh waveforms for various assumptions of stress drop

rupture zones in the aegean region rupture zones of strong shallow earthquakes can be investigated by field observations of surface fault traces sf accurate location of spatial clusters of aftershocks or other small earthquakes cl reliable fault plane solutions fp and information on the spatial distribution of sites with high i viii macroseismic intensities ma the validity of these four techniques was successfully tested by comparing the results of their application to several cases of strong shallow earthquakes these techniques were then applied to spatially define the rupture zones of 150 strong m 6 0 shallow earthquakes in the aegean and surrounding area the type of faulting was determined for all these zones by the use of reliable fault plane solutions which are available for this area the orientation of most of these rupture fault zones is in good agreement with the presently acting stress field with some exceptions which are attributed to the rupture of pre existing faults the tectonic implications of these zones are discussed 1999 elsevier science b v all rights reserved

a detailed study of the active crustal deformation in the aegean and surrounding area abstract a detailed study of the active crustal deformation in the aegean sea and surrounding area is presented the estimation of the deformation velocities is not performed in broad seismic zones but in seismogenic sources of limited spatial extent where the seismic energy is practically released in order to describe the spatial variations of the components of the strain rate tensor the deformation analysis is based on previous work where the seismicity and the available focal mechanisms are used separately for estimating the rate and shape of the deformation respectively the calculations were performed for 63 seismogenic sources identified in the aegean sea and surrounding area which belong to eight belts with an almost uniform orientation of the stress field along the coasts of albania and northwestern greece up to leukada island the collision of the adria plate with eurasia results in a compressional velocity of about 4 mm yr in a direction n49 e almost normal to the coast line the dextral movement with almost 3 cm yr along the cephalonia transform fault with strike n45 e is expressed as an almost equal extension and compression in n s and e w direction respectively along the convex outer part of the hellenic arc a crustal shortening of 1 3 cm yr is observed in a mean direction n34 e the direction of this shortening is almost constant from the southern ionian islands zakynthos up to rodos while the shortening rate does not significantly change from the outer sources to the inner ones the aegean sea and surrounding area is characterised by an extensional deformation the direction of the maximum extension in the northern part of this area shows an anticlockwise rotation from east to west thus this extension has a nne direction in northwestern turkey n11 e a nnw direction in central and northern greece as well as along the southern aegean volcanic arc and its extension to southwestern turkey n12 w and a wnw direction in the westernmost part of this extensional area n72 w the mean value of the extensional velocities in this area is 5 mm yr the northern part of asia minor and of the aegean sea is characterised by the dextral strike slip movement of about 2 cm yr of the north anatolian fault and its continuation in the northern aegean where this movement gradually decreases to about 6 mm yr the vertical crustal upper 10 km of the crust thickening is about 2 mm yr along the convex side of the hellenic arc and the vertical crustal thinning is about 1 mm yr in the aegean sea these values were obtained from the component u 33 of the velocity tensor

surface fault traces fault plane solution and spatial distribution of the aftershocks of the september 13 1986 earthquake of kalamata southern greece a shallow earthquake ofms 6 2 occurred in the southern part of the peloponnesus 12 km north of the port of the city of kalamata which caused considerable damage the fault plane solution of the main shock geological data and field observations as well as the distribution of foci of aftershocks indicate that the seismic fault is a listric normal one trending nne ssw and dipping to wnw the surface ruptures caused by the earthquake coincide with the trace of a neotectonic fault which is located 2 3 km east of the city of kalamata and which is related to the formation of messiniakos gulf during the pliocene quaternary tectonics field observations indicate that the earthquake is due to the reactivation of the same fault

seismic faults in the aegean area abstract reliable fault plane solutions of shallow earthquakes and information on surface fault traces in combination with other seismic geomorphological and geological information have been used to determine the orientation and other properties of the seismic faults in the aegean and surrounding area thrust faults having an about nw se strike occur in the outer seismic zone along western albania westernmost part of mainland of greece ionian sea south of crete south of rhodes the inner part of the area is dominated by strike slip and normal faulting strike slip with an about ne sw slip direction occurs in the inner part of the hellenic arc along the line peloponnesus cyclades dodecanese southwest turkey as well as along a zone which is associated with the northern aegean trough and the northwesternmost part of anatolia all other regions in the inner part of the area are characterized by normal faulting the slip direction of the normal faults has an about sw ne direction in crete n38 e and an about e w direction n81 e in a zone which trends n s in eastern albania and its extension to western mainland of greece in all other regions central greece southern yugoslavia and bulgaria western turkey the slip of the normal faults has an about n s direction

an empirical approach to studying debris flows implications for planetary modeling studies 1 high resolution images acquired by the mars global survey mars orbiter camera show gullies on the walls of impact craters and valley systems on mars depositional aprons associated with these gullies have been interpreted by malin and edgett 2000 to be characteristic of debris flow and to indicate the presence of sources of liquid water at shallow depths below the martian surface by focusing on a terrestrial debris flow we test the application of chezy type modeling to provide more direct estimates of the dynamics of proposed debris flows on mars traditionally planetary scientists constrained by available remotely sensed data have used a range of flow models to gain insights from deposits into the behavior and rheologic nature of features such as lava flows debris flows and gravity driven flows on the basis of these model results broad interpretations of the physics governing flows of granular materials have been tempting based on limited field derived data this study tests and validates the extent to which the absolute value and relative variations of empirical parameters derived from the chezy type models describe the behavior of the general s slide debris flow 38 24 n 78 23 w in madison county virginia the results indicate that extreme caution must be taken when interpreting model results for turbulent flows of granular materials we obtained high precision topographic profiles superelevation data sedimentary facies and sedimentary textural properties over the debris flow this study focuses on the empirical parameter c whose value gauges energy dissipation in a flow thereby called flow resistance using field observations both variations and absolute values of c along the debris flow have been computed using two approaches 1 assuming constant volumetric flow rate q where only topography and high resolution images are required to compute channel dimensions and 2 a variable q calculated using field derived data assuming near newtonian flow conditions in the debris flow estimated values of c range from 0 035 to 0 099 when q is fixed c decreases as a function of distance downstream when q varies and c is computed from field derived flow speeds its value tends to increase downstream slightly these opposite results have been compared to the field observations to determine which best describes the behavior of the flow the variations in c downstream obtained using the flow speeds are most consistent with the geomorphic evidence for erosion of material by the debris flow and the presence of bends in the channel the average values of c 0 036 0 33 for the general s slide have been compared with computed c values for newtonian and near newtonian flows to assess the rheology of the flow during emplacement our terrestrial study demonstrates that advances in understanding of the dynamics of debris flows on the mars depends on obtaining debris flow speeds in addition to channel topography and flow thickness rather than just on channel topography flow thickness and the assumption that q is constant mars orbiter camera moc and mars observer laser altimeter mola data can be used to derive channel topography flow thickness and possibly flow speeds such data will provide more direct estimates of the dynamics of debris flows on mars than are currently available

a combined morphometric sedimentary gis and modelling analysis of flooding and debris flow hazard on a composite alluvial fan caveside tasmania abstract two episodes of intense flooding and sediment movement occurred in the westmorland stream alluvial system near caveside australia in january 2011 and june 2016 the events were investigated in order to better understand the drivers and functioning of this composite alluvial system on a larger scale so as to provide awareness of the potential hazard from future flood and debris flow events a novel combination of methods was employed including field surveys catchment morphometry gis mapping from lidar and aerial imagery and hydraulic modelling using riverflow 2d software both events were initiated by extreme rainfall events

estimating the mud depth of debris flow in a natural river channel a theoretical approach and its engineering application mud depth of debris flow is an essential parameter for assessing the hazard magnitude in an event however direct prediction of mud depth in a natural river channel is a scientific challenge because current methods often treat the complex relief of bed surface as a rectangular one which makes the prediction illogical in this paper we propose a new theoretical approach the so called numerical integral method based approach for estimating the maximum mud depth of debris flow at a complex cross section in a natural river channel given a predefined peak discharge of the debris flow event the numerical integral method based iteration algorithm uses the riemann method to search for an approximate mud depth in contrast to the previous methods the presented approach addresses an important issue namely it takes into account the complex shape of the bed surface and superelevation at the bend for natural channels two cases are used to illustrate the performance and advantages of the presented approach one is a well documented event in the previous study and the other is a debris flow event after ms 8 0 wenchuan earthquake an engineering application regarding the rational design of a debris flow canal is subsequently discussed the canal was completely destroyed in a debris flow event in 2008 we used the proposed method to back analyze the mud depth and velocity in the canal it was found that the abrupt decrease of mud depth from the natural channel to the concrete canal significantly reduced the transportation capability thereby causing blockage in the canal the canal was modified and reconstructed in 2009 with suggested improvements from the proposed method and successfully transported subsequent debris flow in 2011

source inversion of seismic waveforms the koyna india earthquakes of 13 september 1967 abstract the treatment of the seismic source inverse problem when diverse forms of waveform data are available is simple and elegant using a moment tensor formalism if earth structure is known and its effects predictable in terms of vertically inhomogeneous elastic layered models then all types of wave phenomena e g surface waves body waves leaky modes etc for a purely deviatoric moment tensor point source may be represented by at most a sum of three green9s functions for an arbitrary symmetric moment tensor point source one additional green9s function is needed for the p sv system however elegant this formalism may be for posing the linear inverse problem the major difficulties lie in earth structure unknowns and resultant nonlinearities in the green9s functions which can cause significant trade offs with source parameters a hybrid inversion procedure is set up to gain insight into the probable unknowns in particular problems by incorporating both a linearized least squares gradient method for the moment tensor or double couple and smoothed time function parameters and a nonlinear systematic trial and error search for moment tensor or double couple parameters for several assumptions of green9s function the inversion technique is applied to near regional waveform data from a small earthquake associated with the koyna reservoir which occurred 13 september 1967 as the second in a group of three events with very similar waveshapes but differing amplitudes the magnitudes of the second and third events are smaller by 0 2 and 0 8 units respectively compared to the first the absolute magnitude for the first event is poorly constrained but is estimated to be 4 0 to 4 5 rather than the previously published value of 5 5 to 6 0 from the similarity of waveshapes all three events are inferred to have the same mechanism and occurred within about 2 km of the same hypocenter the results from moment tensor and double couple inversions for event 2 data indicate that source depth was 5 km and that left lateral faulting occurred on a plane with a strike of n20 e 5 dip of 90 15 and a rake of 0 35 the inferred far field time function is approximately 3 sec in duration unusually long for the seismic moment of 9 10 22 dyne cm yielding a possible stress drop of about 0 05 bars a fault map was constructed from landsat image interpretation and shows a predominance of nnw to nne striking faults in the koyna area which is used to infer the appropriate nodal plane in the inversion results these faults tend to define a broad en echelon zone which parallels the western ghats in this area

probabilities of occurrence of large earthquakes in the aegean and surrounding area during the period 1986 2006 repeat times of large shocks are obtained for 17 seismic fracture zones of the aegean and surrounding area from times of historic and present century earthquakes the mean standard deviation of the repeat times is approximately 50 of any one observation

regional focal mechanisms for earthquakes in the aegean area the distribution of the focal mechanisms of the shallow and intermediate depth h 40 km earthquakes of the aegean and the surrounding area is discussed the data consist of all events of the period 1963 1986 for the shallow and 1961 1985 for the intermediate depth earthquakes with m s 5 5 for this purpose all published fault plane solutions for each event have been collected reproduced carefully checked and if possible improved accordingly the distribution of the focal mechanisms of the earthquakes in the aegean declares the existence of thrust faulting following the coastline of southern yugoslavia albania and western greece extending up to the island of cephalonia this zone of compression is due to the collision between two continental lithospheres apulian eurasian the subduction of the african lithosphere under the aegean results in the occurrence of thrust faulting along the convex side of the hellenic arc these two zones of compression are connected via strike slip faulting observed at the area of cephalonia island the p axis along the convex side of the arc keeps approximately the same strike throughout the arc 210 nne ssw and plunges with a mean angle of 24 to southwest the broad mainland of greece as well as western turkey are dominated by normal faulting with the t axis striking almost ns with a trend of 174 for greece and 180 for western turkey the intermediate depth seismicity is distributed into two segments of the benioff zone in the shallower part of the benioff zone which is found directly beneath the inner slope of the sedimentary arc of the hellenic arc earthquakes with depths in the range 40 100 km are distributed the dip angle of the benioff zone in this area is found equal to 23 this part of the benioff zone is coupled with the seismic zone of shallow earthquakes along the arc and it is here that the greatest earthquakes have been observed m s 8 0 the deeper part inner of the benioff zone where the earthquakes with depths in the range 100 180 km are distributed dips with a mean angle of 38 below the volcanic arc of southern aegean

gis assisted modelling for debris flow hazard assessment based on the events of may 1998 in the area of sarno southern italy part i maximum run out based on the debris flow events that occurred in may 1998 in the area of sarno southern italy this paper presents an approach to simulate debris flow maximum run out on the basis of the flow source areas and an average thickness of 1 2 m of the scarps we estimated debris flow volumes of the order of 104 and 105 m3 flow mobility ratios h l derived from the x y z coordinates of the lower most limit of the source areas i e apex of the alluvial fan and the distal limit of the flows ranged between 0 27 and 0 09 we performed regression analyses that showed a good correlation between the estimated flow volumes and mobility ratios this paper presents a methodology for predicting maximum run out of future debris flow events based on the developed empirical relationship we implemented the equation that resulted from the calibration as a set of gis macros written in visual basic for applications vba and running within arcgis we carried out sensitivity analyses and observed that hazard mapping with this methodology should attempt to delineate hazard zones with a minimum horizontal resolution of 0 4 km the developed procedure enables the rapid delineation of debris flow maximum extent within reasonable levels of uncertainty it incorporates sensitivities and it facilitates hazard assessments via graphic user interfaces and with modest computing resources copyright 2007 john wiley sons ltd

volcaniclastic debris flows in the clanio valley campania italy insights for the assessment of hazard potential abstract the rugged and steep slopes of the clanio valley campania southern italy mantled by volcaniclastic deposits from explosive eruptions of somma vesuvius and phlegraean fields volcanoes have a great potential for generating volcaniclastic debris flows during the well known meteorological event of may 5 6 1998 which triggered tens of debris flows causing enormous damage and casualties in the area of sarno quindici siano bracigliano sqsb the clanio valley was also affected by these hazardous phenomena debris flows were triggered by the failure of the volcaniclastic cover of the carbonate relief in the form of soil slips mainly on the sides of steep valleys slope between 26 and 45 a map of the hazard potential was created on the basis of both field and computer assisted morphometric data three classes characterised by a high medium and low hazard potential were distinguished within the higher class a better and more detailed zonation was obtained by studying the shape of the disrupted and undisrupted basins during the may 5 6 1998 event in the nearby sarno quindici siano bracigliano area this type of morphometric analysis can be applied rapidly by using a digital elevation model dem which allows a rapid investigation of large scale areas such an approach can be useful in areas characterised by similar geological and geomorphological settings

moment tensor inversion of complex earthquakes summary moment tensor inversion methods can be applied with success in the determination of source properties of simple earthquakes however these methods utilize the assumption of a point source which is inadequate for modelling many complicated shallow earthquakes for complex earthquakes an inversion using finite faulting models is desirable but the number of parameters involved requires that a good starting model be found or that independent constraints be placed on some of the parameters a method is presented for low pass filtering both the data and green s functions passing only signals with wavelengths greater than the dimension of the entire fault the filter tends to smooth complications in the waveforms and allows application of the point source moment tensor inversion this method is applied to body waves from the 1978 thessaloniki greece earthquake the 1971 san fernando earthquake and to a multiple point source synthetic model of the san fernando event for the thessaloniki event although a multiple source mechanism has been suggested inversion results before and after filtering were essentially identical indicating that a point source mechanism is sufficient in modelling the long period teleseismic body waves in the case of the san fernando earthquake the point source green s functions were incapable of simultaneously modelling the p and sh waves inversion of p waves alone resulted in extreme parameter resolution problems but allowed constraint in one axis of the moment tensor and suggested an overall source time function inversion of a synthetic san fernando data set yielded similar results but allowed an investigation of the shortcomings of the method under controlled circumstances although the results may require substantial interpretation the method presented represents a simple first step in the analysis of complex earthquakes

toward a homogeneous moment magnitude determination for earthquakes in greece and the surrounding area a strategy is presented in order to produce a statistically homogeneous catalog of historical and present century earthquakes of the aegean area by expressing the size of all these earthquakes in the moment magnitude scale records of the mainka and wiechert intermediate period t 4 sec seismographs in athens have been used to calculate the magnitudes of earthquakes that occurred in greece and its surrounding area albania s yugoslavia s bulgaria and w turkey during the whole instrumental period since 1911 this magnitude m has also been used to derive empirical relations with macroseismic data it is shown here that m is equivalent to moment magnitude mw for a wide range of earthquake sizes 5 0 m 8 0 and to the surface wave magnitude ms for large earthquake sizes 6 m 8 0 it is also shown that the local magnitude ml for earthquakes in greece is half a unit smaller than the moment magnitude in the low magnitude range 4 5 ml 6 0 this could be attributed to a magnification smaller than the nominal for the wood anderson seismographs in greece v 1000 relations are also proposed to calculate moment magnitude when other magnitudes m ml ms and mb are known for earthquakes in greece

edge wave and non trapped modes of the 25 april 1992 cape mendocino tsunami the 25 april 1992 cape mendocino earthquake generated a tsunami characterized by both coastal trapped edge wave and non trapped tsunami modes that propagated north and south along the u s west coast both observed and synthetic time series at crescent city and north spit are consistent with the zero order edge wave mode solution for a semi infinite sloping beach depth profile wave amplitudes at crescent city were about twice that observed at north spit in spite of the fact that the source region was three times farther from crescent city than north spit the largest observed amplitude was due to an edge wave which arrived almost three hours after the initial onset of the tsunami since such waves are highly localized nearshore this suggests that the enhanced responsiveness at crescent city is at least partly due to local dynamic processes furthermore the substantially delayed arrival of this wave which was generated at the southern end of the cascadia subduction zone has significant implications for hazard mitigation efforts along the entire u s west coast specifically this study demonstrates that slow moving but very energetic edge wave modes could be generated by future large tsunamigenic earthquakes in the csz and that these might arrive unexpectedly at coastal communities several hours after the initial tsunami waves have subsided

estimation of earthquake source parameters of the may 4 1972 event of the hellenic arc by the inversion of waveform data abstract average source parameters of the may 4 1972 m s 6 5 earthquake southwest of crete are obtained by the inversion of body waves a source depth of 40 km is determined which places the source in the mantle the source parameters of the major double couple are strike 309 dip 18 rake 89 and seismic moment m 0 2 62 10 25 dyn cm the source time function is of 5 s duration with a long rise time the mechanism obtained corresponds to a pure thrust with the p axis almost perpendicular to the hellenic arc although a point source is assumed the resulting synthetics match satisfactorily the observed waveforms

gis assisted modelling for debris flow hazard assessment based on the events of may 1998 in the area of sarno southern italy ii velocity and dynamic pressure the velocity and dynamic pressure of debris flows are critical determinants of the impact of these natural phenomena on infrastructure therefore the prediction of these parameters is critical for hazard assessment and vulnerability analysis we present here an approach to predict the velocity of debris flows on the basis of the energy line concept first we obtained empirically and field based estimates of debris flow peak discharge mean velocity at peak discharge and velocity at channel bends and within the fans of ten of the debris flow events that occurred in may 1998 in the area of sarno southern italy we used this data to calibrate regression models that enable the prediction of velocity as a function of the vertical distance between the energy line and the surface despite the complexity in morphology and behaviour of these flows the statistical fits were good and the debris flow velocities can be predicted with an associated uncertainty of less than 30 and less than 3 m s 1 we wrote code in visual basic for applications vba that runs within arcgis to implement the results of these calibrations and enable the automatic production of velocity and dynamic pressure maps the collected data and resulting empirical models constitute a realistic basis for more complex numerical modelling in addition the gis implementation constitutes a useful decision support tool for real time hazard mitigation copyright 2008 john wiley sons ltd

quantitative analysis of debris torrent hazards for design of remedial measures debris torrents which are rapid flows of soil and organic debris down steep mountain channels are a major natural hazard in many parts of british columbia a series of recent occurrences along the

numerical simulation of some lahars from mount st helens abstract an unsteady open channel model is used to simulate lahars discharge flow depth peak arrival time etc under the restriction of negligible volume and solid fraction variations and of channelled flow the model is able to deal with the propagation of steep fronts and transitions from a supercritical to a subcritical flow regime and vice versa conditions frequently occurring on account of the rapidity of lahar triggering mechanisms large water debris volumes are often mobilized in a very short time and of topographical characteristics the model is based on equations governing balance of mass and momentum while the energy dissipation term is expressed as a power function of the flow depth and discharge two past lahars at mount st helens the pine creek and muddy river lahars of may 18 1980 are simulated and the results obtained are discussed for these lahars the triggering mechanism was the melting of snow and ice due to pyroclastic flows and surges many millions of cubic meters of water mostly from the melting of ice and snow and sediments eroded material and pyroclastic products were mobilized in only a few minutes the simulation begins at some kilometers from the vent where lahar volumes reach an almost constant value and the flow is channelled the triggering mechanism plays a fundamental role in the downvalley destructive power of a lahar initial hydrographs characterized by steep slopes such as those occurring as a consequence of pyroclastic flows and surges rapidly flatten downvalley as predicted by the model conversely hydrographs with a prolonged peak discharge even if the peak value is smaller undergo little changes over distances of lens of kilometers with disastrous consequences as in the case of the 1980 north fork lahar at mount st helens triggered by the seismic shaking of an avalanche debris

microearthquake seismicity and fault plane solutions in the southern aegean and its geodynamic implications summary seismicity mi 3 5 in the southern aegean located using data collected during seven weeks of recording by a temporary network of seismological stations largely follows the hellenic arc the sea of crete is nearly aseismic and only little activity is located south of the hellenic trench within the african plate focal mechanisms exhibit reverse faulting in the external part of the arc and normal faulting inside it this normal faulting indicates n s extension in the northern aegean the gulf of corinth the cyclades and dodecanese islands but nw se extension in southern peloponnese and western crete and e w extension in eastern crete this non uniform strain pattern suggests that the aegean region not only extends in a n s sense with the hellenic arc moving south westward relative to the eurasian plate but also by e w extension of its southern margin so that there is a net divergence of material

the geometry of the wadati benioff zone and lithospheric kinematics in the hellenic arc abstract accurate locations of 961 shallow and intermediate depth earthquakes which occurred between 1956 and 1995 in the hellenic arc 34 39 n 19 28 e are used to define the plate boundaries in this area reliable fault plane solutions for 77 shallow and intermediate depth earthquakes are also used in order to define the interaction between the different plates in the arc an ocean continent type of interaction occurs on a curved surface which is defined by the shallow branch 20 100 km of the wadati benioff zone the intersection of this zone with the earth s surface is a curve which follows the convex outer side of the sedimentary arc western peloponnese west of cythera south coast of crete east coast of rhodes and dips at low angle 30 to the aegean sea coupling between the subducted oceanic crust and the overriding of the aegean lithospheric plate takes place on this surface the deep branch 100 180 km of the wadati benioff zone is dipping freely without coupling at a high angle 45 beneath the south aegean trough and the volcanic arc the high shallow seismicity h 20 km which is observed in the southwestern convex outer side of the arc ionian sea is attributed to the fast southwestward motion of the aegean plate location of strong deep earthquakes h 100 km in the fore arc area of the southwestern part of the hellenic arc west of cythera indicates that oceanic crust is destroyed in this part of the hellenic trench due to roll back of the descending lithospheric slab

earthquake mechanisms in the hellenic trench near crete summary in the hellenic trench south of crete convergence between the southern aegean sea and africa occurs at a rate of at least 60 mm yr 1 previously published first motion fault plane solutions show a variety of different fault orientations and types but are not well constrained furthermore the lack of reliable focal depths for these earthquakes has obscured any simple pattern of deformation that might exist nonetheless the mechanisms of these earthquakes have strongly influenced views of the tectonics in the hellenic trench we have improved estimates of the fault parameters and focal depths for 14 of these earthquakes using long period p and sh waveforms the earthquake mechanisms fall into four groups a normal faults with a n s strike in the over riding material above the subduction zone b low angle thrusts with an e w strike at a depth of about 40 km c high angle reverse faults with the same strike but shallower focal depths than b d events within the suducting lithosphere with approximately e w p axes the thrusting in groups b and c is probably the mechanism by which the sediments of the mediterranean sea underplate and uplift crete these events have slip vectors in the direction 025 12 which represents the convergence direction between crete and africa along the sw facing boundary of the hellenic trench one of the events in group d occurred beneath the mediterranean ridge and involved high angle reverse faulting with a wnw ese p axis almost perpendicular to the direction of shortening deduced from folds at the surface the mediterranean sea floor in this region appears to be in a state of e w compression for reasons that are not clear

source mechanisms of recent earthquakes in the hellenic arc from broadband data three component long period seismograms from the global digital seismic network gdsn are used to determine the focal mechanisms of recent large mb 5 5 earthquakes in the hellenic arc using the relative amplitude method results are consistent with the regional stress regime obtained from other methods but they are better constrained broadband seismograms have been deconvolved from gdsn short period data and preliminary modelling of the p phases has been carried out using a two dimensional finite dislocation model this results in better fits to the data than earlier models using point source trapezoids as a source time function the relatively shallow hypocentral depths and stress drops typical of interplate contact zones 30 bar are consistent with previous observations this latter contrasts with the relatively low intraplate earthquake stress drops 15 bar reported for back arc events using the same technique

classification of seismic strain estimates in the mediterranean region from a bootstrap approach summary the uncertainty that may affect seismic strain estimates in the mediterranean is investigated using a distribution free numerical approach based on the bootstrap resampling technique applied to more than 2000 seismic source mechanisms of shallow earthquakes that occurred from the azores to iran in the period 1905 1999 this analysis shows that the short time interval covered by the available data set may be the main source of uncertainty on long term strain estimates since it could imply a biased representation of contributions from large earthquakes our results also indicate that as a possible consequence of this bias the condition of strain field uniformity is poorly verified in most of the zones considered the confidence limits obtained for scalar strains and directions of principal strain axes indicate that both the amount and the style of seismic deformation are poorly defined for roughly half of the zones considered mostly located in the western and central mediterranean area these results suggest that one should be cautious in using seismic strain estimates when not accompanied by satisfactorily uncertainty evaluation

the 14 february 2008 earthquake m6 7 sequence offshore south peloponnese greece source models of the three strongest events abstract we investigate the rupture process of the strongest events of the 14 february 2008 sequence which ruptured 30 km of the western hellenic trench three were the strongest events of the sequence the first one m 6 7 occurred on 14 february 2008 at a depth of 30 km on a low angle 10 thrust fault followed within 2 h by an m 6 1 aftershock at a depth of 33 km also on a low angle thrust fault and the third one on 20 feb 2008 of m 6 0 which is characterized as a strike slip event at shallower depth 10 km we used the m 6 1 aftershock as empirical green s function egf to invert for the slip distribution of the strongest m 6 7 event of the sequence we were able to identify the low angle plane strike 288 dip 10 and rake 73 as the fault plane the slip model is dominated by two distinct slip patches which extend towards sse from the hypocenter thus implying rupture directivity toward the island of crete a result which is further supported by our teleseismic waveform inversion results maximum slip is estimated at 270 cm while average slip on the ruptured area area of subfaults of non zero slip was 70 cm most of the slip 95 of total is confined in an area of 34 22 km 2 we attribute the occurrence of the shallow strike slip event just above the interplate thrusting at depth to slip partitioning due to the deflection of slip vectors from the expected plate convergence vector

a fluid dynamics approach to modelling the 18th march 2007 lahar at mt ruapehu new zealand lahars are water sediment mass flows from a volcanic source they can be triggered by a variety of mechanisms and span a continuum of flow rheology and hydraulic properties even within the same event lahars are extremely powerful landscaping agents and represent a considerable hazard potential however this highly dynamic character and a lack of direct measurements has made modelling lahars difficult this study therefore applies a fluid dynamics model delft3d to analyse the 18th march 2007 dam break lahar at mount ruapehu new zealand the modelled lahar routed through the whangaehu gorge in 30 min crossed the whangaehu fan in 60 min and then over a further 3 h travelled an additional 22 km distance along the whangaehu river to the tangiwai bridge the modelled mean frontal velocity was 6 5 m s 1 along the gorge although peak velocity reached up to 19 6 m s 1 the modelled lahar flow front progressively slowed across the fan but along the river it accelerated from 2 1 3 3 m s 1 calculated peak velocity along the river was 4 5 m s 1 these results generally compare well with gauged records with historical records and with other modelling approaches however discrepancies in frontal velocity and time to peak stage arise due to 1 specifying roughness which arises from slope variations between adjacent computational nodes and which is stage dependant and 2 due to rapid topographic changes that produce frequent hydraulic jumps which are inadequately accommodated in the numerical scheme the overall pattern of discharge attenuation and of relationships between topographic and hydraulic variables is similar to that calculated for lahars on other volcanoes this modelling method could be applied at other similar sites where a likely source hydrograph and high resolution topographic data are available these results have important implications for hazard management at ruapehu and for examining geomorphic and sedimentary impacts of this lahar