a new algorithm for the automatic extraction of valley floor width abstract the width of the valley floor dictates the structure and function of the associated river or stream at the macro level consequently the valley floor width is increasingly recognized as a key parameter and has been employed for many applications e g river classification here we propose an automated algorithm approach to extract the valley floor width of u and v shaped valleys by using the breakpoint of the slope between the valley wall and valley floor to support digital elevation models dems of different resolutions the algorithm includes five steps 1 preprocessing data 2 extracting linear reach 3 extracting perpendiculars of reaches 4 delineating the outlines of the valley floor and 5 calculating the width of the valley floor eight case studies were used to validate the algorithm valley floor outlines and widths were computed and measured revealing that the algorithm performs well with a high correlation coefficient cc 0 88 and coefficient of determination r2 0 77 as well as low relative bias rb

temporal changes of shallow seismic velocity around the karadere duzce branch of the north anatolian fault and strong ground motion we analyze temporal variations of seismic velocity along the karadere duzce branch of the north anatolian fault using seismograms generated by repeating earthquake clusters in the aftershock zones of the 1999 mw7 4 izmit and mw7 1 duzce earthquakes the analysis employs 36 sets of highly repeating earthquakes each containing 4 18 events the events in each cluster are relocated by detailed multi step analysis and are likely to rupture approximately the same fault patch at different times the decay rates of the repeating events in individual clusters are compatible with the omori s law for the decay rate of regional aftershocks a sliding window waveform cross correlation technique is used to measure travel time differences and evolving decorrelation in waveforms generated by each set of the repeating events we find clear step like delays in the direct s and early s coda waves sharp seismic velocity reduction immediately after the duzce main shock followed by gradual logarithmic type recoveries a gradual increase of seismic velocities is also observed before the duzce main shock probably reflecting post seismic recovery from the earlier izmit main shock the temporal behavior is similar at each station for clusters at various source locations indicating that the temporal changes of material properties occur in the top most portion of the crust the effects are most prominent at stations situated in the immediate vicinity of the recently ruptured fault zones and generally decrease with normal distance from the fault a strong correlation between the co seismic delays and intensities of the strong ground motion generated by the duzce main shock implies that the radiated seismic waves produced the velocity reductions in the shallow material

prediction of the behaviour of landslide dams using a geomorphological dimensionless index landslide dams are a common phenomenon they form when a landslide reaches the bottom of a river valley causing a blockage the first effect of such a dam is the infilling of a lake that inundates the areas upstream while the possibility of a sudden dam collapse with a rapid release of the impounded waters poses a higher flood risk to the downstream areas the results of the main inventories carried out to date on landslide dams have been examined to determine criteria for forecasting landslide dam evolution with particular emphasis on the assessment of dam stability not all landslides result in the blockage of a river channel this only occurs with ones that can move a large amount of material with moderate or high velocities in most cases these landslides are triggered by rainfall events or high magnitude earthquakes a relationship also exists between the volume of the displaced material and the landslide dam stability several authors have proposed that landslide dam behaviour can be forecast by defining various geomorphological indexes that result from the combination of variables identifying both the dam and the dammed river channel further developments of this geomorphological approach are presented in this paper by the definition of a dimensionless blockage index starting with an analysis of 84 episodes selected worldwide it proved to be a useful tool for making accurate predictions concerning the fate of a landslide dam copyright 2002 john wiley sons ltd

using repeating earthquakes to correct high precision earthquake catalogs for time dependent station delays waveform cross correlation allows one to measure the relative arrival times of similar microearthquakes with errors of less than 1 10 of 1 sample location algorithms based on these measurements have greatly improved images of earthquake distribution for the northern california seismic network catalog however the relative location errors implied by the scatter of relocated repeating earthquakes sometimes 10s of meters is often considerably larger than the errors estimated from monte carlo simulations meters using a priori estimates of the cross correlation errors i find that most of this discrepancy arises from unmodeled time varying station delays by identifying many clusters of repeating earthquakes presumed to rupture the same source and assuming the measured arrival time differences between event pairs to be due to the difference in origin time plus the difference in station delay it is possible to invert for time dependent station corrections the method is robust in that these corrections are consistent over many kilometers of fault and greatly reduce the scatter and residuals when relocating earthquake clusters not used in the station correction determination many of the largest delay changes some approaching 2 samples 20 ms are associated with changing station electronics at several stations an annual cycle is also clearly seen with amplitudes up to 0 5 samples some m 4 7 earthquakes have produced comparable transient delay changes after applying the station corrections the scatter within clusters of repeating earthquakes is reduced to a few meters and the apparent seismogenic thickness of many kilometer long sections of faults is only 10 20 m manuscript received 31 may 2001

effects of loading velocity stiffness and inertia on the dynamics of a single degree of freedom spring slider system numerical simulation of the nonlinear dynamics of a single degree of freedom spring slider system can provide useful insight into the effects of loading velocity friction environment elastic stiffness and inertia on the stress drop and dynamic behavior of earthquakes in our numerical simulations using a rate and state dependent friction law we varied the loading velocity by 7 orders of magnitude the stiffness by 2 orders of magnitude the mass by 5 orders of magnitude and the velocity weakening parameter b a by a factor of 160 four stability regimes were identified in the load point velocity stiffness space when inertia was taken into account for cyclic stick slip instabilities the stress drop amplitude increases with decreasing load point velocity with decreasing stiffness with increasing velocity weakening parameter b a and with decreasing mass simple scaling relations for the static stress drop dynamic stress drop static friction and shear fracture energy with the natural logarithm of load point velocity were observed using the scaling relation for static stress drop we infer the normalized velocity weakening parameter b a with respect to normal stress to range from 0 0011 to 0 0039 for triaxial experiments on saw cut westerly granite specimens sandwiched with a simulated gouge layer of ultrafine quartz at pressures from 10 mpa to 100 mpa unless we take b a throughout the seismogenic layer to be much higher than experimental measurements the effect of loading velocity by itself is not sufficient to account for the increase of stress drop with increasing earthquake recurrence time inferred from seismological data to the extent that our simple system can be treated as an analog for earthquakes our study shows that the velocity weakening parameter b a controls the magnitude of the static stress drop far more than the loading velocity if velocity weakening increases systematically with increasing healing time then the coupled effect of loading velocity variation and change in friction environment can account for the seismological observations

the formation and failure of natural dams of the numerous kinds of dams that form by natural processes dams formed from landslides glacial ice and late neoglacial moraines present the greatest threat to people and property landslide dams form in a wide range of physiographic settings the most common types of mass movements that form landslide dams are rock and debris avalanches rock and soil slumps and slides and mud debris and earth flows the most common initiation mechanisms for dam forming landslides are excessive rainfall and snowmelt and earthquakes landslide dams can be classified into six categories based on their relation with the valley floor type i dams 11 of 184 landslide dams from around the world that we were able to classify do not reach from one valley side to the other type ii dams 44 span the entire valley floor in some cases depositing material high on opposite valley sides type iii dams 41 move considerable distances both upstream and downstream from the landslide failure type iv dams 1 are rare and involve the contemporaneous failure of material from both sides of a valley type v dams 1 also are rare and are created when a single landslide sends multiple tongues of debris into a valley and forms two or more landslide dams in the same reach of river type vi dams 3 involve one or more failure surfaces that extend under the stream or valley and emerge on the opposite valley side many landslide dams fail shortly after formation in our sample of 73 documented landslide dam failures 27 of the landslide dams failed less than 1 day after formation and about 50 failed within 10 days over topping is by far the most common cause of failure the timing of failure and the magnitude of the resulting floods are controlled by dam size and geometry material characteristics of the blockage rate of inflow to the impoundment size and depth of the impoundment bedrock control of flow and engineering controls such as artificial spill ways diversions tunnels and planned breaching by blasting or conventional excavation glacial ice dams can produce at least nine kinds of ice dammed lakes the most dangerous are lakes formed in main valleys dammed by tributary glaciers failure can occur by erosion of a drainage tunnel under or through the ice dam or by a channel over the ice dam cold polar ice dams generally drain supraglacially or marginally by downmelting of an outlet channel warmer temperate ice dams tend to fail by sudden englacial or subglacial breaching and drainage late neoglacial moraine dammed lakes are located in steep mountain areas affected by the advances and retreats of valley glaciers in the last several centuries these late neoglacial dams pose hazards because 1 they are sufficiently young that vegetation has not stabilized their slopes 2 many dam faces are steeper than the angle of repose 3 these dams and lakes are immediately downslope from steep crevassed glaciers and near vertical rock slopes and 4 downstream from these dams are steep canyons with easily erodible materials that can be incorporated in the flow and increase flood peaks the most common reported failure mechanism is overtopping and breaching by a wave or series of waves in the lake generated by icefalls rockfalls or snow or rock avalanches melting of ice cores or frozen ground and piping and seepage are other possible failure mechanisms natural dams may cause upstream flooding as the lake rises and downstream flooding as a result of failure of the dam although data are few for the same potential energy at the dam site ownstream flood peaks from the failure of glacier ice dams are smaller than those from landslide moraine and structed earth fill and rock fill dam failures moraine dam failures appear to produce some of the largest downstream flood peaks for potential energy at the dam site greater than 1011 1012 joules differences in flood peaks natural dam failures appear to be controlled by dam characteristics and failure mechanisms

systematic search for repeating earthquakes along the haiyuan fault system in northeastern tibet repeating earthquakes have been found at many faults around the world and they provide valuable information on diverse faulting behavior at seismogenic depth the haiyuan fault is a major left lat

analysis of landslide dams induced by the 2008 wenchuan earthquake abstract landslide dams caused by earthquakes are extremely hazardous disruptions of the flow of water and sediment in mountain rivers capable of delivering large outburst floods that may devastate downstream areas we analyzed a unique inventory of 828 landslide dams triggered by the m w 7 9 2008 wenchuan tectonic earthquake china constituting 1 4 of the 60 000 coseismic slope failures mapped and attributed to this event while 501 landslides blocked the rivers completely the remainder caused only partial damming or channel diversion the spatial distribution of landslide dams follows the same trend of that of the total landslide distribution with landslide dams being most abundant in the steep watersheds of the hanging wall of the yingxiu beichuan thrust fault and in the northeastern part of the strike slip fault near qingchuan besides the co seismic landslide density the river width also played a key role in determining the landslide dam formation narrow rivers are more prone to be dammed than the wide rivers the correlation between river width and landslide dam volume follows a linear relation which can be used to roughly estimate the dam formation possibility however the applicability of this correlation needs to be validated in other regions the decay failure rate of dams defined here as the percentage of the number and area of landslide dams that have failed over time shows that 25 of dams accounting for 30 of total landslide dam area failed one week after the earthquake these percentages increased to 60 within 1 month and to 90 within 1 year the geomorphometric parameters were analyzed revealing power law relations between landslide area and dam width landslide source area and dam area as well as lake area and lake volume the inventory presented in this study will enrich the worldwide earthquake induced landslide dam database and will also contribute to a better understanding of the post earthquake dam decay

strain rate effect on frictional strength and the slip nucleation process abstract kato n yamamoto k yamamoto h and hirasawa t 1992 strain rate effect on frictional strength and the slip nucleation process in t mikumo k aki m ohnaka l j ruff and p k p spudich editors earthquake source physics and earthquake precursors tectonophysics 211 269 282 the strain rate dependence of frictional strength is investigated in relation to sliding behaviour by biaxial compression tests of large scale granite samples frictional sliding is generated by increasing shear strain at a constant rate under a constant normal stress on the fault the ram displacement is held constant for a prescribed time interval between two successive sliding events so as to have the same time effect of stationary contact between sliding surfaces we obtained the following results as the strain rate increases 1 sliding becomes more unstable 2 the nucleation zone size of stick slip decreases and 3 frictional strength logarithmically increases result 3 is consistent with the previous study by dieterich 1979a and 1 and 3 are similar to the strain rate effects on failure characteristics of intact rocks reported in the literature result 3 can be explained by a rate and state dependent friction law our results suggest that the strain rate dependence of the fault strength plays an important role in controlling the nucleation process of faulting

faulting style controls for the space time aftershock patterns abstract to understand the complexity and thus to predict earthquake occurrence in size time and space seismicity patterns are characterized by two robust empirical laws the exponential distribution of magnitude and the power law decrease of aftershock rate over time these laws are known as the gutenberg richter law and the omori law respectively using global earthquake catalogs we resolve that on average the k aftershock productivity and the p value exponent of the power law decrease of aftershock rate over time are dependent on the mainshock faulting style strike slip events have a lower aftershock rate n and k values and a larger p value than thrust and normal events respectively within the epidemic type aftershock sequence model strong k n values are driven by a high branching ratio value n within the same framework a relatively higher n value for the thrust events also predicts the lower p value we observe for thrust events as compared to strike slip and normal faulting events respectively furthermore we observed that earthquake interactions through time and space are a function of the faulting style when measured by t the exponent of the power law decrease of earthquake density over space the t values of thrust events for different time windows always remain smaller than those of the strike slip events when changes in faulting styles are driven by stress pattern the anderson faulting theory predicts thrust faulting that requires somewhat larger stresses in absolute magnitude than do normal and strike slip faulting within the framework of rate and state friction law changes in the stress heterogeneity patterns reproduce the p value changes we observe our results suggest that only stress perturbations associated with mainshock rupture affect the productivity and decay rate over time of aftershocks

influence of diversion channel section type on landslide dam draining effect the present study focuses on the emergency response measures for landslide dams this work presents a series of centrifuge model tests conducted on the draining processes of barrier dams that are based on the grain composition of the tangjiashan landslide dam the effects of diversion channels with trapezoid triangular and compound sections on the discharge process and size of the residual dam are discussed the characteristics of the flow erosion during the process of discharge in the different channels are analyzed based on hydrodynamics the results suggest that a diversion channel with a compound section has a higher initial discharge efficiency and lower peak flow and the flow process curve corresponds to a chunky type the draining from this type of a diversion channel could clearly reduce the flood pressure of the river downstream and make the entire process smoother thus the excavation of a diversion channel with a compound section is an efficient and safe method for landslide dam emergency mitigation

seismicity rate immediately before and after main shock rupture from high frequency waveforms in japan 1 we analyze seismicity rate immediately before and after 82 main shocks with the magnitudes ranging from 3 to 5 using waveforms recorded by the hi net borehole array in japan by scrutinizing high frequency signals we detect 5 times as many aftershocks in the first 200 s as in the japan meteorological agency catalogue after correcting for the changing completeness level immediately after the main shock the aftershock rate shows a crossover from a slower decay with an omori s law exponent p 0 58 0 08 between 20 and 900 s after the main shock to a faster decay with p 0 92 0 04 after 900 s the foreshock seismicity rate follows an inverse omori s law with p 0 73 0 08 from several tens of days up to several hundred seconds before the main shock the seismicity rate in the 200 s immediately before the main shock appears steady with p 0 35 0 50 these observations can be explained by the epidemic type aftershock sequence etas model and the rate and state model for a heterogeneous stress field on the main shock rupture plane alternatively nonseismic stress changes near the source region such as episodic aseismic slip or pore fluid pressure fluctuations may be invoked to explain the observation of small p values immediately before and after the main shock

spatial patterns of landslide dimension a tool for magnitude mapping abstract the magnitude of mass movements which may be expressed by their dimension in terms of area or volume is an important component of intensity together with velocity in the case of slow moving deep seated landslides the expected magnitude is the prevalent parameter for defining intensity when assessed as a spatially distributed variable in a given area in particular the frequency volume statistics of past landslides may be used to understand and predict the magnitude of new landslides and reactivations in this paper we study the spatial properties of volume frequency distributions in the arno river basin central italy about 9100 km2 the overall landslide inventory taken into account around 27 500 events shows a power law scaling of volumes for values greater than a cutoff value of about 2 104 m3 we explore the variability of the power law exponent in the geographic space by setting up local subsets of the inventory based on neighbourhoods with radii between 5 and 50 km we found that the power law exponent varies according to geographic position and that the exponent itself can be treated as a random space variable with autocorrelation properties both at local and regional scale we use this finding to devise a simple method to map the magnitude frequency distribution in space and to create maps of exceeding probability of landslide volume for risk analysis we also study the causes of spatial variation of by analysing the dependence of power law properties on geological and geomorphological factors and we find that structural settings and valley density exert a strong influence on mass movement dimensions

earthquake induced chains of geologic hazards patterns mechanisms and impacts large earthquakes initiate chains of surface processes that last much longer than the brief moments of strong shaking most moderate and large magnitude earthquakes trigger landslides ranging from small failures in the soil cover to massive devastating rock avalanches some landslides dam rivers and impound lakes which can collapse days to centuries later and flood mountain valleys for hundreds of kilometers downstream landslide deposits on slopes can remobilize during heavy rainfall and evolve into debris flows cracks and fractures can form and widen on mountain crests and flanks promoting increased frequency of landslides that lasts for decades more gradual impacts involve the flushing of excess debris downstream by rivers which can generate bank erosion and floodplain accretion as well as channel avulsions that affect flooding frequency settlements ecosystems and infrastructure ultimately earthquake sequences and their geomorphic consequences alter mountain landscapes over both human and geologic time scales two recent events have attracted intense research into earthquake induced landslides and their consequences the magnitude m 7 6 chi chi taiwan earthquake of 1999 and the m 7 9 wenchuan china earthquake of 2008 using data and insights from these and several other earthquakes we analyze how such events initiate processes that change mountain landscapes highlight research gaps and suggest pathways toward a more complete understanding of the seismic effects on the earth s surface

experimental study on the river blockage and landslide dam formation induced by rock slides abstract rock slides triggered by strong earthquake or heavy rainfall may cause different degrees of blockage in flow channels resulting in a significant impact on the continuity of mountainous rivers based on the extent of blocking the blockage type is divided into three categories in this paper no blockage submerged dam partial blockage and complete blockage the accumulation process of sliding materials in the course of rock slides is an important issue for understanding the formation of landslide dams in this study rock slide and river valley models are developed to investigate the typical kinematic process and emplacement of rock slides and the factors that dictate the formation of landslide dams are critically analyzed the experimental study suggests that there is a positive correlation between the deposit height and the rock slide volume despite differences of rock fragmentation and flow condition in addition the less fragmented rocks result in larger maximum deposit height maxi dh and smaller minimum deposit height mini dh while the better fragmented rocks result in smaller maxi dh and larger mini dh furthermore the water depth has a significant impact on the river blockage type a new blockage index bi that combines the landslide volume and the wet cross sectional area is proposed to assess the damming capacity of rock slides then a method for predicting the river blockage type of rock slides is developed based on the relationship between blockage index and the ratio of maxi dh or mini dh and water depth the model proposed in this work can be used to assist estimating the formation of landslide dam for similar rock slides in the future

digital terrain modelling a review of hydrological geomorphological and biological applications the topography of a catchment has a major impact on the hydrological geomorphological and biological processes active in the landscape the spatial distribution of topographic attributes can often be used as an indirect measure of the spatial variability of these processes and allows them to be mapped using relatively simple techniques many geographic information systems are being developed that store topographic information as the primary data for analysing water resource and biological problems furthermore topography can be used to develop more physically realistic structures for hydrologic and water quality models that directly account for the impact of topography on the hydrology digital elevation models are the primary data used in the analysis of catchment topography we describe elevation data sources digital elevation model structures and the analysis of digital elevation data for hydrological geomorphological and biological applications some hydrologic models that make use of digital representations of topography are also considered

analyzing successive landslide dam formation by different triggering mechanisms the case of the tangjiawan landslide sichuan china abstract the catastrophic tangjiawan landslide triggered by the 2008 wenchuan earthquake blocked the duba river impounding one of the most dangerous coseismic barrier lakes in beichuan china the lake was drained by an artificial spillway within one month after the earthquake to minimize the potential dam breach flooding risk however on september 5 2016 this landslide was reactivated and dammed the river again creating a 20 m high dam at the same location and resulting in the formation of a barrier lake with a volume of 0 6 million m3 the day after the event we carried out a field investigation of the landslide and obtained a high resolution image and dem using uav the satellite images from 2005 2008 2010 and 2015 were also collected to analyze the evolution of the landslide together with multi temporal dems the geometry and volumes of the displaced mass and the landslide dams and barrier lakes were calculated using image interpretation and 3d spatial analysis with gis this landslide is of great scientific interest as it presents a good example of multiple reactivation of a pre historical giant landslide under different triggering conditions a reactivation of an older landslide during the wenchuan earthquake and a second reactivation during a rainfall event several years later meanwhile from the hazard assessment and prevention perspective it is also representative as it dammed the river twice in 2008 and 2016 posing threats to both upstream and downstream areas we infer that the successive landslides in this region could be caused by the strong tectonic activities including earthquakes and high average uplifting rate the results of landslide volume analysis using multi temporal dems contribute to the landslide mechanism analysis and suggest that the landslide volume estimation is effected by the landslide type landslide rupture surface location and resolution of dem we also compare the performance of different empirical models of landslide stability and dam breach flood parameters and discuss their application during the quick assessment of the potential hazard of the landslide dams generally the successive landslide dams at the tangjiawan site are caused by the successive landslide reactivations on an anti dip slope controlled by strong tectonic activity and river erosion involve with a mass of loose materials of previous landslide deposition and possess high flood risk to the downstream area the experience gained in this work can be used to assist the hazard assessment and the planning of the emergency measures for similar landslide dams in the future

geomorphic processes and risk related to a large landslide dam in a highly urbanized mediterranean catchment genova italy abstract we present our research on the prato casarile landslide dam in genoa city to illustrate the interactions between slope instability processes and structural stabilization interventions aimed to reduce the hazard in a densely populated area analysis of the degradation of structural interventions constructed after flood events in 1953 1970 and 2014 contributed to an improved mitigation strategy at the same time the slope instability processes intensively advanced and regressive erosion quickly proceeded to the landslide dam threshold the discontinuity in human interactions in a geomorphic system after the initial hazard reduction resulted in an increased threat that combined with a rise in vulnerability due to urbanization expansion the research findings underline the necessity of constantly assessing the geomorphic evolution and active processes involved in order to determine the specific actions and interventions required to ensure the stability of the landslide dam finally and more generally we illustrated that anthropogenic interaction in the geomorphic system specifically when finalized for hazard mitigation needs to be continuously performed through both the monitoring and maintenance operation phases of the artificial structures

triggering effect of m 4 5 earthquakes on the earthquake cycle of repeating events at parkfield california stress perturbations influence earthquake recurrence and are of funda mental importance to understanding the earthquake cycle and determining earthquake hazard the large population of repeating earthquakes on the san andreas fault at parkfield california provides a unique opportunity to examine the response of the repeating events to the occurrence of moderate earthquakes using 187 m 0 4 to 1 7 repeating earthquake sequences from the high resolution seismic network cat alog we find that the time to recurrence of repeating events subsequent to nearby m 4 5 earthquakes is shortened suggesting triggering by major events the triggering effect is found to be most evident within a distance of 5 km corresponding to static coseismic stress changes of 0 6 26 6 kpa and decays with distance we also find coherently reduced recurrence intervals from 1993 to 1998 this enduring recurrence acceleration over several years reflects accelerated fault slip and thus loading rates during the early 1990s online material figures of event chronologies of res estimates of dt and coseismic static stress changes

logistic regression model for predicting the failure probability of a landslide dam landslides may obstruct river flow and result in landslide dams they occur in many regions of the world the formation and disappearance of natural lakes involve a complex earth surface process according to the lessons learned from many historical cases landslide dams usually break down rapidly soon after the formation of the lake regarding hazard mitigation prompt evaluation of the stability of the landslide dam is crucial based on a japanese dataset this study utilized the logistic regression method and the jack knife technique to identify the important geomorphic variables including peak flow or catchment area dam height width and length in sequence affecting the stability of landslide dams the resulting high overall prediction power demonstrates the robustness of the proposed logistic regression models accordingly the failure probability of a landslide dam can also be evaluated based on this approach ten landslide dams formed after the 1999 chi chi earthquake the 2008 wenchuan earthquake and 2009 typhoon morakot with complete dam geometry records were adopted as examples of evaluating the failure probability the stable tsao ling landslide dam which was induced by the chi chi earthquake has a failure probability of 27 68 using a model incorporating the catchment area and dam geometry on the contrary the tangjiashan landslide dam which was artificially breached soon after its formation during the wenchuan earthquake has a failure probability as high as 99 54 typhoon morakot induced the siaolin landslide dam which was breached within one hour after its formation and has a failure probability of 71 09 notably the failure probability of the earthquake induced cases is reduced if the catchment area in the prediction model is replaced by the peak flow of the dammed stream for these cases in contrast the predicted failure probability of the heavy rainfall induced case increases if the high flow rate of the dammed stream is incorporated into the prediction model consequently it is suggested that the prediction model using the peak flow as causative factor should be used to evaluate the stability of a landslide dam if the peak flow is available together with an estimation of the impact of an outburst flood from a landslide dammed lake the failure probability of the landslide dam predicted by the proposed logistic regression model could be useful for evaluating the related risk

the 1786 earthquake triggered landslide dam and subsequent dam break flood on the dadu river southwestern china abstract chinese historic documents recorded that on june 1 1786 a strong m 7 75 earthquake occurred in the kangding luding area sichuan southwestern china resulting in a large landslide that fell into the dadu river as a result a landslide dam blocked the river ten days later the sudden breaching of the dam resulted in catastrophic downstream flooding historic records document over 100 000 deaths by the flood this may be the most disastrous event ever caused by landslide dam failures in the world although a lot of work has been carried out to determine the location magnitude and intensity of the 1786 earthquake relatively little is known about the occurrence and nature of the landslide dam in this paper the dam was reconstructed using historic documents and geomorphic evidence it was found that the landslide dam was about 70 m high and it created a lake with a water volume of about 50 106 m3 and an area of about 1 7 km2 the landslide dam breached suddenly due to a major aftershock on june 10 1786 the peak discharge at the dam breach was estimated using regression equations and a physically based predictive equation the possibility of a future failure of the landslide seems high particularly due to inherent seismic risk and detailed geotechnical investigations are strongly recommended for evaluating the current stability of the landslide

do earthquakes talk to each other triggering and interaction of repeating sequences at parkfield 1 knowledge of what governs the timing of earthquakes is essential to understanding the nature of the earthquake cycle and to determining earthquake hazard yet the variability and controls of earthquake recurrences are not well established the large population of small characteristically repeating earthquakes at parkfield provides a unique opportunity to study how the interaction of earthquakes affects their recurrence properties we analyze 112 m 0 4 3 0 repeating earthquake sequences ress to examine the triggering effect from nearby microseismicity we find that the repeating events with a smaller number of neighboring earthquakes in their immediate vicinity tend to recur in a more periodic manner i e the coefficient of variation in recurrence intervals is less than 0 3 the total static stress perturbation from close by earthquakes however does not seem to strongly influence res regularity the uneven distribution of stress changes in time has a modest but significant impact on recurrence intervals a significant reduction of recurrence intervals occurs in the case of very high stress changes from neighboring events close by events influence res timing in a matter of several days or less by short term triggering events that occurred within less than 1 day of an res often imposed or experienced high stress changes a static stress increment of 30 kpa can be enough to produce such short term triggering we find that the triggered repeating events are often near the end of their average earthquake cycle but some events occur following a substantially shortened interval when comparing the accelerated occurrence at the time of res events following neighboring events with varying magnitudes we find that the distance of short term triggering increases from 1 km to 4 km for m1 to m4 events

application of a multi temporal lidar derived digital terrain model in a landslide volume estimation sediments produced by landslides are crucial in the sediment yield of a catchment debris flow forecasting and related hazard assessment on a regional scale however it is difficult and time consuming to measure the volumes of such sediment this paper uses a lidar derived digital terrain model dtm taken in 2005 and 2010 at 2 m resolution to accurately obtain landslide induced sediment volumes that resulted from a single catastrophic typhoon event in a heavily forested mountainous area of taiwan the landslides induced by typhoon morakot are mapped by comparison of 25 cm resolution aerial photographs taken before and after the typhoon in an 83 6 km2 study area each landslide volume is calculated by subtraction of the 2005 dtm from the 2010 dtm and the scaling relationship between landslide area and its volume are further regressed the relationship between volume and area are also determined for all the disturbed areas vl 0 452al1 242 and for the crown areas of the landslides vl 2 510al1 206 the uncertainty in estimated volume caused by use of the lidar dtms is discussed and the error in absolute volume estimation for landslides with an area 105 m2 is within 20 the volume area relationship obtained in this study is also validated in 11 small to medium sized catchments located outside the study area and there is good agreement between the calculation from dtms and the regression formula by comparison of debris volumes estimated in this study with previous work it is found that a wider volume variation exists that is directly proportional to the landslide area especially under a higher scaling exponent copyright 2013 john wiley sons ltd

high resolution image of calaveras fault seismicity 1 by measuring relative earthquake arrival times using waveform cross correlation and locating earthquakes using the double difference technique we are able to reduce hypocentral errors by 1 to 2 orders of magnitude over routine locations for nearly 8000 events along a 35 km section of the calaveras fault this represents 92 of all seismicity since 1984 and includes the rupture zone of the m 6 2 1984 morgan hill california earthquake the relocated seismicity forms highly organized structures that were previously obscured by location errors there are abundant repeating earthquake sequences as well as linear clusters of earthquakes large voids in seismicity appear with dimensions of kilometers that have been aseismic over the 30 year time interval suggesting that these portions of the fault are either locked or creeping the area of greatest slip in the morgan hill main shock coincides with the most prominent of these voids suggesting that this part of the fault may be locked between large earthquakes we find that the calaveras fault at depth is extremely thin with an average upper bound on fault zone width of 75 m given the location error however this width is not resolvably different from zero the relocations reveal active secondary faults which we use to solve for the stress field in the immediate vicinity of the calaveras fault we find that the maximum compressive stress is at a high angle only 13 from the fault normal supporting previous interpretations that this fault is weak

distribution of postseismic slip on the calaveras fault california following the 1984 m6 2 morgan hill earthquake abstract repeating earthquakes res are sequences of events that have virtually identical waveforms and are interpreted to represent fault asperities driven to failure by loading from aseismic creep on the surrounding fault surface at depth to investigate the postseismic deformation after the 1984 m6 2 morgan hill earthquake we identify re sequences occurring on the central calaveras fault between 1984 and 2005 using a combination of cross correlation and spectral coherence techniques both the accelerated slip transients due to the earthquake as well as the return to interseismic background creep rates can be imaged from our dataset a comparison between the regions of the fault that ruptured coseismically and the locations of the res show that res preferentially occur in areas adjacent to the coseismic rupture using calculated re derived subsurface slip distributions at 6 months and 18 months after the mainshock we predict surface electronic distance meter edm line length changes between stations near the morgan hill rupture area the re derived slip model underpredicts a subset of the observed line length changes inclusion of transient aseismic slip below the seismogenic zone is needed to better match the measured surface deformation

linearized inversion for fault rupture behavior application to the 1984 morgan hill california earthquake we present a technique to infer the rupture history of an earthquake from near source records of ground motion unlike most previous studies each point on the fault is assumed to slip only once when the rupture front passes with a spatially variable slip intensity in this parameterization the data are linearly related to slip intensity but nonlinearly related to rupture time we perform a linearized inversion for slip intensity and rupture time by iteratively perturbing an assumed starting model the inverse problem for the model perturbation is solved using a tomographic back projection technique smoothing and inequality constraints are applied to ensure that the resulting solution is stable and feasible asymptotic ray theory is used to calculate theoretical seismograms and partial derivatives with respect to model parameters in test cases with noisy synthetic data sets we found that it is possible to distinguish between rupture models having variable slip amplitude and models having variable rupture velocity provided the station coverage is adequate we apply the technique to recordings of the april 24 1984 morgan hill earthquake the results indicate that slip amplitude on the fault plane was extremely variable and that the rupture front did not propagate uniformly away from the hypocenter in particular rupture was delayed on a 12 km2 section of the fault approximately 14 km to the southeast of the hypocenter the rupture front surrounded the region which subsequently failed with a component of rupture propagation back toward the hypocenter similar behavior has been observed in dynamic rupture models with stress or strength inhomogeneities this segment of the fault ruptured with a large slip amplitude releasing 12 of the total seismic moment from 4 of the total area of the aftershock zone the surface trace of this section of the fault is characterized by a complex left step that could act to increase the normal stress acting across the fault however the distribution of aftershocks suggests that the fault at depth is simpler and that it may bend to the right in either case our rupture model suggests that this segment of the fault represents an asperity which initially resisted rupture but eventually ruptured massively we estimate the shear fracture energy for this earthquake to be 2 106 j m2

interseismic coupling and refined earthquake potential on the hayward calaveras fault zone interseismic strain accumulation and fault creep is usually estimated from gps and alignment arrays data which provide precise but spatially sparse measurements here we use interferometric synthetic aperture radar to resolve the interseismic deformation associated with the hayward and calaveras faults hf and cf in the east san francisco bay area the large 1992 2011 sar data set permits evaluation of short and long wavelength deformation larger than 2 mm yr without alignment of the velocity field to a gps based model our time series approach in which the interferogram selection is based on the spatial coherence enables deformation mapping in vegetated areas and leads to refined estimates of along fault surface creep rates creep rates vary from 0 2 mm yr on the northern cf to 14 2 mm yr on the central cf south of the hf surface junction we estimate the long term slip rates by inverting the long wavelength deformation and the distribution of shallow slip due to creep by inverting the remaining velocity field this distribution of slip reveals the locations of locked and slowly creeping patches with potential for a m6 8 0 3 on the hf near san leandro a m6 6 0 2 on the northern cf near dublin a m6 5 0 1 on the hf south of fremont and a m6 2 0 2 on the central cf near morgan hill with cascading multisegment ruptures the hf rupturing from berkeley to the cf junction could produce a m6 9 0 1 the northern cf a m6 6 0 1 the central cf a m6 9 0 2 from the junction to gilroy and a joint rupture of the hf and central cf could produce a m7 1 0 1

rescaled earthquake recurrence time statistics application to microrepeaters slip on major faults primarily occurs during characteristic earthquakes the recurrence statistics of characteristic earthquakes play an important role in seismic hazard assessment a major problem in determining applicable statistics is the short sequences of characteristic earthquakes that are available worldwide in this paper we introduce a rescaling technique in which sequences can be superimposed to establish larger numbers of data points we consider the weibull and log normal distributions in both cases we rescale the data using means and standard deviations we test our approach utilizing sequences of microrepeaters microearthquakes which recur in the same location on a fault it seems plausible to regard these earthquakes as a miniature version of the classic characteristic earthquakes microrepeaters are much more frequent than major earthquakes leading to longer sequences for analysis in this paper we present results for the analysis of recurrence times for several microrepeater sequences from parkfield ca as well as ne japan we find that once the respective sequence can be considered to be of sufficient stationarity the statistics can be well fitted by either a weibull or a log normal distribution we clearly demonstrate this fact by our technique of rescaled combination we conclude that the recurrence statistics of the microrepeater sequences we consider are similar to the recurrence statistics of characteristic earthquakes on major faults

laboratory study of fault healing and lithification in simulated fault gouge under hydrothermal conditions abstract seismic data geologic observations and laboratory friction studies suggest that faults lithify and strengthen heal during the interseismic period of the earthquake cycle we report on experiments to investigate the influence of healing duration and temperature on the strength and healing rate of simulated faults layers of m sized quartz powder were used to simulate granular fault gouge gouge layers were sheared within sioux quartzite in a triaxial pressure vessel at elevated pressures p c 250 mpa elevated temperatures 230 636 c and in the presence of water p h 2 o 75 mpa we performed hold slide experiments in which samples were subjected to a period of healing under hydrostatic load followed by shear deformation healing times ranged from a few hundred s to 10 5 s to isolate the effects of lithification and temperature on friction we ran two types of hold slide experiments 1 samples were subjected to healing and shear deformation at elevated temperature and 2 following healing at elevated temperature temperature was reduced prior to shear we also ran slide hold slide experiments in which samples were healed under shear load at elevated temperature 636 c experiments in which deformation was carried out at a lower temperature than healing show that both the static and sliding coefficient of friction increase with heal time samples healed and deformed at higher temperature showed lower peak strengths and within the scatter of our data did not exhibit time dependent strengthening these data are interpreted to result from enhanced lithification rates at elevated temperature samples healed under shear load exhibited a log linear decrease in friction with hold time modeling using rate and state dependent friction laws indicates velocity strengthening behavior with friction a b values of 0 05 to 0 08 our data indicate that at high temperature the effective state evolution term b is negative moreover the data indicate the rate of frictional strengthening varies significantly for hydrostatic and non hydrostatic load conditions our measurements of healing are consistent with seismic estimates of fault healing rates if stress drop is a fraction of the total shear stress and effective fault normal stress is 60 to 100 mpa

the use of the stream length gradient index in morphotectonic analysis of small catchments a case study from central italy abstract the aim of this work is to test an integrated quantitative geomorphic approach based on stream length gradient index sl index analysis within the small catchment of the tarugo river in the northern marchean apennines central italy the tarugo river basin 92 km 2 wide strikes sw ne across the marchean ridge and the western sector of marchean piedmont the area is characterized by a series of nw se trending ne verging thrust folds affecting the meso cenozoic bedrock that pass upward from dominantly carbonate to dominantly terrigenous rocks the area investigated has been affected since the pliocene by extensional tectonics accompanying a regional uplift decreasing in rate north eastwards in this work the sl index analysis has been integrated with the spatial analysis of the amplitude of relief a r and compared to geological and geomorphological field data results of this work indicate that the sl index is a valid tool to detect the long wavelength structural effect on topography as well as the incipient local response to regional processes i e regional uplift that is often undetectable by other morphotectonic parameters in contrast the sl index analysis seems not be a valid tool for discriminating the local lithological influence from the tectonic one

geomorphometric characteristics of new zealand landslide dams abstract this study presents results from a quantitative analysis of a new inventory of n 232 landslide dam occurrences in new zealand previously published data were expanded by documentation of recent events and evidence from a regional air photo reconnaissance focused on the upland regions of southwestern south island additional geomorphometric data on landslide dams associated lakes and contributing catchment characteristics were extracted from a 25 m digital elevation model dem augmented by limited ground truthing and compiled in a gis based inventory the new zealand case examples fall into the global trend although they contain both two extremely large features in terms of landslide dam volume vd and lake volume vl analysis suggests that landslide dam height hd landslide dam volume vd lake volume vl contributing catchment area ac and local relief hr are key variables for assessing landslide dam stability independently from other catchment parameters such as lithology climate or dam sedimentology they may be provisionally used as representative characteristics of landslide dams irrespective of environmental boundary conditions such as climate geology or site specific valley geomorphometry three newly proposed dimensionless indices i e the backstow index is basin index ia and relief index ir based on landslide dam height hd allow limited yet promising preliminary assessments of landslide dam stability compared with worldwide examples they also demonstrate a much narrower conditional range for the formation of stable landslide dams in new zealand catchment parameters such as maximum elevation emax upstream relief hr contributing catchment area ac and relief ratio rr are significantly different at sites of former and existing landslide dammed lakes and may be used as independent variables in future terrain based classification schemes generally data are incomplete with underreporting of small and ephemeral landslide dams and over representation of earthquake case studies nonparametric correlation highlights the statistical interdependence between geomorphometric variables as an artefact of initial data calculation while varying accuracy poses a significant drawback for complex multivariate statistical techniques such as principal component cluster or discriminant analyses

3d dem investigation on the morphology and structure of landslide dams formed by dry granular flows abstract large scale landslide dams triggered by earthquakes or rainfall can cause disasters due to inundation upstream and outburst floods downstream after dam failure landslide dams formed by rock debris avalanches are loose in structure and have a lack of stability thus they are more susceptible to breaking the morphological and structural features of landslide dams directly depend on the formation process and greatly affect the dam stability as well as the dam failure modes this study presents the transportation and deposition characteristics of dry granular flows with grains of mixed sizes during the formation of landslide dams via 3d discrete element method dem simulations mainly taking into consideration of the influence of the sliding area length angle and roughness the results show reverse segregation during grain transportation and deposition processes the position of the particles forming the initial deposited layers was also reversed it was found that when the sliding area angle was larger the crest surface frontal angle and deposit width increased with the increment of the sliding area length for lower sliding area angles the deposit width and crest surface frontal angle showed little change the increase of sliding length and base friction coefficient as well as the decrease of the sliding area angle will enhance the size segregation as the slope angle increases the dominant direction of the force chains shifts significantly and the sliding length mainly influences the magnitude of the normal contact force in the other directions these considerations can contribute to a better understanding of the landslide dam morphology and structure after their formation

time dependent friction of granite implications for precursory slip on faults frictional forces were measured during sliding between saw cut cylinders of barre granite deformed in a servo controlled triaxial loading machine two different effects occur depending on the type of loading when steady shortening of a stably sliding sample is halted suddenly slip continues at a diminishing rate which depends on the logarithm of the initial sliding velocity thus the frictional strength of the surface is decreasing with time when shortening at a constant rate resumes after the holding period however the frictional resistance temporarily rises to a peak proportional to the logarithm of time of no driving showing a well known increase in friction with time the subsequent decrease in resistance from this peak is continuous the observed frictional resistance of a surface thus results from the interaction of several processes and is not a constant in general but depends on the immediate and preceding deformation when shortening is resumed after a period of holding slip rate across the friction surface temporarily accelerates above the driving rate the slip rate can then either decrease to the driving rate and remain stable or accelerate further and lead to stick slip motion at stress levels below the peak value there is no apparent difference in the frictional resistance until the unloading rate of the loading machine is exceeded between slip episodes which settle stably to the constant driving rate and those which become unstable and result in stick slip the stick slip failure criterion is not a peak stress but rather loss of strength more rapidly that the unloading rate of the loading machine the evidence that accelerating motion before stick slip is due to the time variable strength of rock suggests that accelerating slip will occur before earthquakes unfortunately for easy observation experiments indicate that slip need not be uniform over a fault surface also to be established is whether slip will be sufficiently large in the earth to be detectable nevertheless a plausible mechanism for generating observable phenomena prior to earthquakes is suggested by the laboratory observations

strain rate effect on fault slip and rupture evolution insight from meter scale rock friction experiments abstract we conduct meter scale rock friction experiments to study strain rate effect on fault slip and rupture evolution two rock samples made of indian metagabbro with a nominal contact dimension of 1 5 m long and 0 1 m wide are juxtaposed and loaded in a direct shear configuration to simulate the fault motion a series of experimental tests under constant loading rates ranging from 0 01 mm s to 1 mm s and under a fixed normal stress of 6 7 mpa are performed to simulate conditions with changing strain rates load cells and displacement transducers are utilized to examine the macroscopic fault behavior while high density arrays of strain gauges close to the fault are used to investigate the local fault behavior the observations show that the macroscopic peak strength strength drop and the rate of strength drop can increase with increasing loading rate at the local scale the observations reveal that slow loading rates favor generation of characteristic ruptures that always nucleate in the form of slow slip at about the same location in contrast fast loading rates can promote very abrupt rupture nucleation and along strike scatter of hypocenter locations at a given propagation distance rupture speed tends to increase with increasing loading rate we propose that a strain rate dependent fault fragmentation process can enhance the efficiency of fault healing during the stick period which together with healing time controls the recovery of fault strength in addition a strain rate dependent weakening mechanism can be activated during the slip period which together with strain energy selects the modes of fault slip and rupture propagation the results help to understand the spectrum of fault slip and rock deformation modes in nature and emphasize the role of heterogeneity in tuning fault behavior under different strain rates

the formation and impact of landslide dams state of the art abstract the blocking of river courses by mass movements is very common in mountainous areas with deep and narrow valleys landslide dams may pose serious threats to people and their livelihoods downstream in the case of abrupt dam failure since the publication of benchmark reviews of costa and schuster 1988 and korup 2002 there is a growing number of studies focusing on the formation stability and short term impacts of landslide dams this review combines the insights of all these studies builds on current concepts of landslide dams and suggests ways to unify terminologies and classifications we furthermore present a new worldwide database compiled from literature data it contains 410 landslide dams 1 million m3 in volume that were formed since 1900 since these have the most complete data entries these data show that dam longevity is among other factors correlated with the type of landslide forming the dam those formed by rock debris avalanches and rockslides have longest lifespans however the influence of landslide type or material on dam longevity decreases with time after dam formation to ensure consistency in the next database generation we suggest guidelines for data collection to provide a solid basis for evaluating dam stability and governing factors a preliminary classification matrix for landslide dam stability that combines topographic setting and the internal structure of the dam body is another outcome of our review furthermore an evaluation of the various geomorphic stability indices proposed in the literature regarding their suitability and limitations in assessing dam formation and stability shows that they predict the probability of dam formation reasonably well but that their application to longevity estimates requires further assessment the geomorphic impacts of landslide dams in the short medium and long term are summarized and illustrated with key examples finally for a better understanding of the factors controlling dam stability we recommend to 1 include dam composition and sedimentary structures in future case studies 2 maintain and update the worldwide database for sound statistical analyses 3 refine landslide dam stability indices and test them for different landslide types and 4 study hazard cascades related to multiple dams in one watershed for long term landscape evolution studies we suggest to 5 quantify terrestrial sediment flux related to landslide dams 6 detect ancient landslide dams in river profiles and 7 further exploit the sediment archives in former impoundment areas

frictional slip of granite at hydrothermal conditions sliding on faults in much of the continental crust likely occurs at hydrothermal conditions i e at elevated temperature and elevated pressure of aqueous pore fluids yet there have been few relevant laboratory studies to measure the strength sliding behavior and friction constitutive properties of faults at hydrothermal conditions we slid laboratory granite faults containing a layer of granite powder simulated gouge velocity stepping experiments were performed at temperatures of 23 to 600 c pore fluid pressures ph2o of 0 dry and 100 mpa wet effective normal stress of 400 mpa and sliding velocities v of 0 01 to 1 m s 0 32 to 32 m yr conditions were similar to those in earlier tests on dry granite to 845 c by lockner et al 1986 the mechanical results define two regimes the first regime includes dry granite up to at least 845 and wet granite below 250 c in this regime the coefficient of friction is high 0 7 to 0 8 and depends only modestly on temperature slip rate and ph2o the second regime includes wet granite above 350 c in this regime friction decreases considerably with increasing temperature temperature weakening and with decreasing slip rate velocity strengthening these regimes correspond well to those identified in sliding tests on ultrafine quartz we infer that one or more fluid assisted deformation mechanisms are activated in the second hydrothermal regime and operate concurrently with cataclastic flow slip in the first cool and or dry regime is characterized by pervasive shearing and particle size reduction slip in the second hot and wet regime is localized primarily onto narrow shear bands adjacent to the gouge rock interfaces weakness of these boundary shears may result either from an abundance of phyllosilicates preferentially aligned for easy dislocation glide or from a dependence of strength on gouge particle size major features of the granite data set can be fit reasonably well by a rate and temperature dependent three regime friction constitutive model chester this issue we extrapolate the experimental data and model fit in order to estimate steady state shear strength versus depth along natural slipping faults for sliding rates as low as 31 mm yr we do this for two end member cases in the first case pore pressure is assumed hydrostatic at all depths shallow crustal strength in this case is similar to that calculated in previous work from room temperature friction data while at depths below about 9 13 km depending on slip rate strength becomes less sensitive to depth but sensitive to slip rate in the second case pore pressure is assumed to be near lithostatic at depths below 5 km strength is low at all depths in this case 20 mpa in agreement with observations of weak faults such as the san andreas the predicted depth of transition from velocity weakening to velocity strengthening lies at about 13 km depth for a slip rate of 31 mm yr in rough agreement with the seismic aseismic transition depth observed on mature continental faults these results highlight the importance of fluid assisted deformation processes active in faults at depth and the need for laboratory studies on the roles of additional factors such as fluid chemistry large displacements higher concentrations of phyllosilicates and time dependent fault healing

the magnitude frequency distribution of earthquakes recorded with deep seismometers at cajon pass southern california abstract the cumulative b value the slope of the gutenberg richter relationship between earthquake occurrence rate and magnitude is commonly found to be constant 1 network catalogues however reveal a decrease at small magnitudes b value is not just an artifact of catalogue incompleteness but that small earthquakes are really not as numerous as a constant b value extrapolated from larger events would predict in the cajon pass area southern california the b value of seismicity recorded by the local network scsn appears to decrease below about m l 1 6 in order to investigate whether this decrease is real or simply represents the network detection threshold we use seismicity recorded by the deep 1 5 and 2 5 km seismometers deployed in the cajon pass scientific drillhole between april 1992 and october 1994 the maximum amplitudes recorded downhole are compared to scsn magnitudes for events recorded by the network to determine the relationship between amplitude and m l as a function of hypocentral distance from the borehole magnitudes are then calculated for 1300 earthquakes which occurred within 40 km of the borehole magnitude frequency curves are calculated for those events within 18 km of the borehole and a constant b value is observed to m l 0 5

dem and gis analysis of the stream gradient index to evaluate effects of tectonics the normandy intraplate area nw france computer based geomorphometry using a dem digital elevation model allows the analysis of the three dimensional properties of landscape this methodology is particularly useful in an intraplate region like western europe where the simple visual inspection of the topography cannot resolve the evolutionary trends of landforms in these domains the morphologies of the topographic surface may be controlled mainly by climate under a low rate of tectonic deformation among the geomorphometric parameters the stream length index sl has been used to characterize fluvial systems in relation to tectonics movements this work develops an algorithm to derive and map the sl index using a dem and gis to investigate its spatial variations in a broad area the algorithm is applied to a zone of weak intraplate deformation the coastal lowlands of normandy france the obtained spatial distributions of sl point to anomalous zones with high sl values these zones are adjacent to mapped fault scarps and characterized by changes in flow direction a kruskal wallis test shows that the bedrock lithology has no impact on the sl value therefore the sl variations can be related mainly to a differential uplift due to quaternary tectonic forcing quaternary sea level fluctuations may also be responsible for high sl values in a part of the coastal lowland

emergence and disappearance of interplate repeating earthquakes following the 2011 m9 0 tohoku oki earthquake slip behavior transition between seismic and aseismic depending on the loading rate we investigated spatiotemporal change in the interplate seismic activity following the 2011 tohoku oki earthquake m9 0 in the region where interseismic interplate coupling was relatively weak and large postseismic slip was observed we classified earthquakes by their focal mechanisms to identify the interplate events and conducted hypocenter relocation to examine the detailed spatiotemporal distribution of interplate earthquakes in the mostly creeping area the results show that many interplate earthquakes including m 6 events emerged immediately after the tohoku oki earthquake in areas where very few interplate earthquakes had been observed in the 88 previous years the emergent earthquakes include repeating sequences and the extremely long quiescence of small to moderate earthquakes before the tohoku oki earthquake suggests that the source areas for the post m9 events slipped aseismically during the quiescence the repeaters magnitudes decayed over time following the tohoku oki earthquake and some sequences disappeared within a year the emergence of interplate earthquakes suggests that areas where aseismic slip had been dominant before the tohoku oki earthquake started to cause seismic slip after the earthquake probably due to the increased loading rate from the afterslip the magnitude decrease and disappearance of repeaters can be interpreted as shrinkage in seismic areas around the repeaters sources as the loading rate decreased due to the afterslip decay over time these observations suggest that changes in the loading rate can cause slip behavior transition between seismic and aseismic this indicates that such loading rate dependent slip behavior plays an important role in the spatiotemporal distribution of earthquakes in interplate seismogenic zones

on behaviour and scaling of small repeating earthquakes in rate and state fault models with abundant seismic data for small repeating earthquakes it is important to construct a dynamic model that can explain various aspects of related observations in this work we study small repeating earthquakes on a fault governed by rate and state dependent friction laws the earthquakes occur on a velocity weakening patch surrounded by a much larger velocity strengthening region the whole fault is subject to long term tectonic loading the model with a circular patch and the aging form of rate and state dependent friction laws has been shown to reproduce the scaling of recurrence time versus seismic moment for small repeating earthquakes in a previous study here we investigate the behaviour of small repeating earthquakes in related models under different scenarios including several forms of the state evolution equations in rate and state dependent friction laws rectangular velocity weakening patch geometries quasi dynamic versus fully dynamic representation of inertial effects and 2 d versus 3 d simulations we find that the simulated scalings between the recurrence time and seismic moment for these different scenarios is similar while differences do exist we propose a theoretical consideration for the scaling between the recurrence time and seismic moment of small repeating earthquakes for patch radii smaller than or comparable to the full nucleation size the scaling is explained by the increase of seismic to aseismic slip ratio with magnitude for patch radii larger than the full nucleation size the scaling is explained by the model in which the recurrence time is determined by the earthquake nucleation time which is in turn determined by the time for aseismic slip to penetrate the distance of the full nucleation size into the patch the obtained theoretical insight is used to find the combinations of fault properties that allow the model to fit the observed scaling and range of the seismic moment and recurrence time

damage to the shallow landers fault from the nearby hector mine earthquake crustal faults have long been identified as sites where localized sliding motion occurs during earthquakes which allows for the relative motion between adjacent crustal blocks although there is a growing awareness that we must understand the evolution of fault systems on many timescales to relate present day crustal stresses and fault motions to geological structures formed in the past fault zone damage and healing have been documented quantitatively in only a few cases we have been monitoring the healing of damage on the shallow johnson valley fault after its rupture in the 1992 magnitude 7 3 landers earthquake and here we report that this healing was interrupted in 1999 by the magnitude 7 1 hector mine earthquake rupture which occurred 20 30 km away the hector mine earthquake both strongly shook and permanently strained the johnson valley fault adding damage discernible as a temporary reversal of the healing process the fault has since resumed the trend of strength recovery that it showed after the landers earthquake these observations lead us to speculate that fault damage caused by strong seismic waves may help to explain earthquake clustering and seismicity triggering by shaking and may be involved in friction reduction during faulting

velocity contrast along the calaveras fault from analysis of fault zone head waves generated by repeating earthquakes 1 we systematically investigate the velocity contrast along the calaveras fault that ruptured during the 1984 morgan hill earthquake using fault zone head waves fzhw that refract along the fault interface we stack waveforms in 353 sets of repeating clusters and align the peaks or troughs of the direct p waves assuming rightlateral strike slip focal mechanisms the obtained velocity contrasts are 2 3 and 12 14 nw and se of station cco respectively the fzhw and the fault plane outlined by the relocated seismicity se of cco are more complicated than those nw of cco the results can be explained by a relatively simple and sharp fault interface in the nw and a complicated fault structure with a presence of a low velocity zone in the se the along strike variations in the strength of the velocity contrast are consistent with surface geological mapping and recent 3d tomography studies in this region citation zhao p and z peng 2008 velocity contrast along the calaveras fault from analysis of fault zone head waves generated by repeating earthquakes geophys res lett 35 l01303 doi 10 1029 2007gl031810

observations of changes in waveform character induced by the 1999 m w7 6 chi chi earthquake 1 we observe changes in the waveforms of repeating earthquakes in eastern taiwan following the 1999 mw7 6 chi chi earthquake while their recurrence intervals appear to be unaffected there is a clear reduction in waveform similarity and velocity changes indicated by delayed phases at the time of the chi chi event these changes are limited to stations in and paths that cross the 70 100 km region surrounding the chi chi source area the area where seismic intensity and co seismic surface displacements were largest this suggests that damage at the near surface is responsible for the observed waveform changes delays are largest in the late s wave coda reaching approximately 120 ms this corresponds to a path averagedswave velocity reduction of approximately 1 there is also evidence that damage in the fault zone caused changes in waveform character at sites in the footwall where source receiver paths propagate either along or across the rupture the reduction in waveform similarity persists through the most recent repeating event in our study november 15 2007 indicating that the subsurface damage induced by the chi chi earthquake did not fully heal within the first 8 years following the chi chi earthquake

detailed spatiotemporal evolution of microseismicity and repeating earthquakes following the 2012 mw 7 6 nicoya earthquake we apply a waveform matching technique to obtain a detailed earthquake catalog around the rupture zone of the 5 september 2012 moment magnitude 7 6 nicoya earthquake with emphasis on its aftershock sequence starting from a preliminary catalog we relocate 7900 events using tomodd to better quantify their spatiotemporal behavior relocated aftershocks are mostly clustered in two groups the first is immediately above the major coseismic slip patch partially overlapping with shallow afterslip the second one is 50 km se to the main shock nucleation point and near the terminus of coseismic rupture in a zone that exhibited little resolvable afterslip using the relocated events as templates we scan through the continuous recording from 29 june 2012 to 30 december 2012 detecting approximately 17 times more than template events we find 190 aftershocks in the first half hour following the main shock mostly along the plate interface later events become more scattered in location showing moderate expansion in both along trench and downdip directions from the detected catalog we identify 53 repeating aftershock clusters with mean cross correlation values larger than 0 9 and indistinguishably intracluster event locations suggesting slip on the same fault patch most repeating clusters occurred within the first major aftershock group very few repeating clusters were found in the aftershock grouping along the southern edge of the peninsula which is not associated with substantial afterslip our observations suggest that loading from nearby afterslip along the plate interface drives spatiotemporal evolution of aftershocks just above the main shock rupture patch while aftershocks in the se group are to the se of the observed updip afterslip and poorly constrained

systematic variations in recurrence interval and moment of repeating aftershocks 1 the recurrence intervals for 194 repeating clusters on the calaveras fault follow a power law decay relation with elapsed time after the 1984 m6 2 morgan hill california mainshock the decay rates of repeating aftershocks in the immediate vicinity of a high slip patch that failed during the mainshock systematically exceed those that are farther away the trend between relative moment and recurrence interval which is a measure of the fault healing rate varies systematically with depth and changes from negative to positive value as the distance between the repeating aftershock and the mainshock slip patch increases we speculate that high strain rate in the early postseismic period may cause transient embrittlement and strengthening of the deep repeating clusters in the areas adjacent to the mainshock slip patch resulting in large moments that decrease with time as the strain rate diminishes our observations suggest that systematic behavior of repeating aftershocks reflect variations in the fault zone rheology

downstream variation in stream power abstract stream power has a significant influence on many form and process attributes of the fluvial system using a similar approach to that suggested by d m lawler in 1992 and 1995 a model is developed to explore how stream power might vary in the downstream direction based on the assumption that the longitudinal profile of the river has an exponential form no particular discharge is necessarily specified but near bankfull flows are regarded as significant morphologically and one such discharge is the focus here total stream power per unit channel length qs is predicted to peak at an intermediate location the position of which depends on the ratio b where b and are the downstream rates of change of discharge and slope respectively if b is a relatively conservative quantity then the form of the longitudinal profile and in particular its degree of concavity will have the major influence on the position of maximum stream power specific stream power w is even more sensitive to and is expected to peak closer to the headwaters about half way between source and the location of the stream power maximum although this will depend on how channel width w varies with distance from source the model is tested along three connected streams of different size in the catchment of the river trent taking advantage of a relationship between mean annual flood and link magnitude which enables this near bankfull discharge to be estimated at any point within the network the model is verified in so far as stream power does attain a mid basin maximum but the observed and predicted locations of the maxima do not always correspond largely because of the distinctive variation in discharge and especially slope along individual pathways for example maximum power lies far downstream along the trent because of the large increase in mid basin discharge associated with a series of large closely spaced tributaries the importance of slope is borne out by the near headwater locations for specific power maxima which tend to be further upstream than predicted along all three rivers as a result of the steepness of upper reaches the variety of geomorphic settings produces deviations from expectation which has implications for the movement and storage of material in the fluvial system

remote triggering of fault strength changes on the san andreas fault at parkfield a 20 year seismological record of from the parkfield area of the san andreas fault has been used to identify two occasions when long term changes in fault strength seem to have been induced remotely by large seismic events the 2004 sumatra andaman and the 1992 landers earthquakes in both cases two changes occurred that are consistent with variations in fault strength variation in the properties of seismic scatterers with time reflecting stress induced migration of fluids and systematic variation in the characteristics of repeating earthquake sequences these findings suggest that the largest earthquakes have a global influence on the strength of the earth s fault systems in support of that hypothesis an unusually large number of m 8 earthquakes occurred in the three years following the 2004 sumatra andaman earthquake changes in fault strength over time can increase or decrease the likelihood of failure and the ultimate triggering of seismic events observation of the parkfield area at the san andreas fault over the years 1987 2008 now reveals two occasions the 2004 sumatra andaman earthquake and the 1992 landers earthquake where long term changes in fault strength have probably been induced remotely by large seismic events fault strength is a fundamental property of seismogenic zones and its temporal changes can increase or decrease the likelihood of failure and the ultimate triggering of seismic events although changes in fault strength have been suggested to explain various phenomena such as the remote triggering of seismicity1 there has been no means of actually monitoring this important property in situ here we argue that 20 years of observation 1987 2008 of the parkfield area at the san andreas fault have revealed a means of monitoring fault strength we have identified two occasions where long term changes in fault strength have been most probably induced remotely by large seismic events namely the 2004 magnitude m 9 1 sumatra andaman earthquake and the earlier 1992 m 7 3 landers earthquake in both cases the change possessed two manifestations temporal variations in the properties of seismic scatterers probably reflecting the stress induced migration of fluids and systematic temporal variations in the characteristics of repeating earthquake sequences that are most consistent with changes in fault strength in the case of the 1992 landers earthquake a period of reduced strength probably triggered the 1993 parkfield aseismic transient2 3 4 5 as well as the accompanying cluster of four m 4 earthquakes at parkfield the fault strength changes produced by the distant 2004 sumatra andaman earthquake are especially important as they suggest that the very largest earthquakes may have a global influence on the strength of the earth s fault systems as such a perturbation would bring many fault zones closer to failure it should lead to temporal clustering of global seismicity this hypothesis seems to be supported by the unusually high number of m 8 earthquakes occurring in the few years following the 2004 sumatra andaman earthquake

depth extent of damage zones around the central calaveras fault from waveform analysis of repeating earthquakes summary we systematically investigate spatial variations of temporal changes and depth extent of damage zones along the calaveras fault that ruptured during the 1984 morgan hill earthquake by the waveform analysis of 333 sets of repeating earthquakes we use a sliding window waveform cross correlation technique to measure traveltime changes in waveforms generated by each repeating cluster we find clear traveltime delays in the s and early s coda waves for events immediately after the morgan hill main shock the amplitudes of the time delays decrease logarithmically with time since the main shock indicating a time dependent recovery healing process following the abrupt coseismic temporal changes the largest temporal changes are observed at station cco that is the closest to the rupture zone of the morgan hill main shock the time delays at this station are larger for clusters in the top 6 km and decrease systematically at larger depth in comparison the time delays observed at other five stations are much smaller and do not show clear relationship with hypocentral depth we suggest that the temporal changes at these five stations mostly occur in the top few hundred metres of the near surface layers while the temporal changes at station cco are likely associated with the damage zone around the calaveras fault that is well developed in the top few kilometres of the upper crust our results are consistent with the inference of a widespread damage and non linearity in the near surface layers associated with strong ground motions of nearby large earthquakes and localized damages and flower type structures around active faults based on previous studies of fault zone structures and recent 3 d numerical simulations

fluvial response to large rock slope failures examples from the himalayas the tien shan and the southern alps in new zealand we describe remnants of large 10 7 10 10 m 3 late pleistocene to holocene rockslides and rock avalanches that block ed rivers and are preserved in the himalayas the tien shan and the new zealand southern alps despite rates of uplift and erosion of up to 10 mm year 1 these natural dams control fluvial response on 10 1 10 4 year timescales by a storing and releasing sediment during forced alluviation and fluvial re incision b relocating river channels through diversion or seepage c inhibiting river erosion into bedrock d formingpersistentlong profileknickpointsandknickslopesassociatedwithsteephigh energy n10 3 wm 2 breachand epigenetic bypass gorges and fluvial hanging valleys and e shaping valley floor morphology sediments indicate that rockslidedammed lakes may persist up to 10 4 years before being drained or infilled several short lived 10 0 10 2 year historical rockslide dams in the indian and nepal himalayas and the southern alps have had marked volumetric impacts on catchment sediment budgets shortly following failure therefore we caution against the linear extrapolation of sediment delivery from prehistoric rockslide dams through time as a response variable we find reach scale changes to channel gradient to be prominent and persistent indicators of fluvial response to large rock slope failures 2006 elsevier b v all rights reserved

recurrence time and frequency slip statistics of slip events on the creeping section of the san andreas fault in central california summary an important question in seismic hazard assessments is the frequency size and recurrence interval statistics at a point on a fault does a point on a fault obey the same statistics as earthquakes in a region do this is a difficult question to answer because the number of repetitive earthquakes on a particular fault that have been observed is small in order to overcome this difficulty we consider slip events on the creeping section of the san andreas fault in central california sequences of up to 100 events are obtained from creepmeter records we compare the statistical distribution of recurrence times with the brownian passage time lognormal and weibull distributions and using goodness of fit tests find that the weibull is the preferred distribution we also consider the frequency amplitude distribution of slip events we find that the data clearly do not obey a gutenberg richter distribution instead there is a uniform distribution of event sizes for a large fraction of events

spatial temporal distribution of early aftershocks following the 2016 ms 6 4 menyuan qinghai china earthquake abstract the lenglongling fault located in the north qilian fold zone along the northeastern margin of the tibetan plateau plays an important role in accommodating the tectonic deformation between the tibetan plateau and the alxa block on 21 january 2016 the ms 6 4 menyuan earthquake occurred near the lenglongling fault in this study we utilize the waveform matched filter technique and double difference earthquake location algorithm to examine the spatial temporal evolution of aftershocks following the menyuan mainshock events from both china earthquake networks center cenc routine catalog and relocated catalog are used as templates to scan through the continuous waveform data 21 january 2016 to 31 december 2016 we identify three and eleven times more events than listed in cenc routine catalog and relocated catalog respectively we find that the earliest aftershocks e g in the first 10 min or so mostly illuminated a steeply dipping plane while aftershocks at later times outlined a near vertical dipping plane with mostly strike slip focal mechanisms the relocated aftershocks also suggest that the menyuan mainshock occurred in a secondary fault rather than the major lenglongling fault which is consistent with geodetic and geological observations moreover we find that aftershocks systematically expand with time along the fault strike and 16 repeating earthquake clusters occur in the rupture zone which are likely driven by afterslip of the mainshock

gis morphometric indicators for the analysis of sediment dynamics in mountain basins watershed management and headwater reconstruction programs require a reliable knowledge of sediment dynamics geographical information systems gis provide the framework for the implementation of different complex techniques for the assessment of shallow landsliding and erosion processes in mountain basins this paper presents some morphometric indicators aimed at erosion and sediment delivery analysis the proposed indicators can be easily derived from medium to fine resolution digital elevation models dem applications conducted in eastern italian alps have shown the adequateness of the proposed approach to address erosion and sediment related problems the analysis considered the classification of sediment source areas with regard to their activity the comparison between drainage basins having different morphological characteristics and the topographic control on sediment transport capacity with a particular attention to the identification of channel reaches characterised by a low sediment transport capacity

frictional heterogeneities on carbonate bearing normal faults insights from the monte maggio fault italy observations of heterogeneous and complex fault slip are often attributed to the complexity of fault structure and or spatial heterogeneity of fault frictional behavior such complex slip patterns have been observed for earthquakes on normal faults throughout central italy where many of the mw 6 to 7 earthquakes in the apennines nucleate at depths where the lithology is dominated by carbonate rocks to explore the relationship between fault structure and heterogeneous frictional properties we studied the exhumed monte maggio fault located in the northern apennines we collected intact specimens of the fault zone including the principal slip surface and hanging wall cataclasite and performed experiments at a normal stress of 10 mpa under saturated conditions experiments designed to reactivate slip between the cemented principal slip surface and cataclasite show a 3 mpa stress drop as the fault surface fails then velocity neutral frictional behavior and significant frictional healing overall our results suggest that 1 earthquakes may readily nucleate in areas of the fault where the slip surface separates massive limestone and are likely to propagate in areas where fault gouge is in contact with the slip surface 2 postseismic slip is more likely to occur in areas of the fault where gouge is present and 3 high rates of frictional healing and low creep relaxation observed between solid fault surfaces could lead to significant aftershocks in areas of low stress drop

fault healing inferred from time dependent variations in source properties of repeating earthquakes we analyze two sets of repeating earthquakes on the calaveras fault to estimate in situ rates of fault strengthening healing earthquake recurrence intervals tr range from 3 to 803 days variations in relative moment and duration are combined to study changes in stress drop rupture dimension rupture veloc ity and particle velocity as a function of t healing rates and source variations are compared with predictions of laboratory derived friction laws two interpretations of event duration z are used one in which is given by the ratio of slip to particle ve locity and one in which it scales as rupture dimension divided by rupture velocity our data indicate that faults strengthen during the interseismic period we infer that source dimension de creases with t r due to aseismic creep within the region surround ing the repeating events stress drop increases 1 3mpa per dec ade increase in twhich represents an increase of a factor of 2 3 relative to events with tbetween 10 and 100 days this rate of fault healing is consistent with extrapolations of laboratory meas urements of healing rates if fault strength is high on order of 60mpa and stress drop is roughly 10 of this value

scaling relations of strike slip earthquakes with different slip rate dependent properties at depth abstract empirical observations suggest that earthquake stress drop is generally constant to investigate the effect of rupture width on earthquake scaling relations we analyze synthetic seismicity produced by a 3d vertical strike slip fault model using two different profiles of frictional slip rate behavior below the seismogenic zone within the rate and state framework a relatively abrupt transition of the a b profile from velocity weakening to strengthening at the base of the seismogenic crust produces increasing slip and stress drop with increasing event size choosing a smoother transition allows large earthquakes to propagate deeper leading to similar slip length scaling but constant stress drop scaling our numerical experiments support the idea that the maintenance of constant stress drop across the entire range of observed earthquake magnitudes may be achieved by allowing coseismic slip to rupture to depths below the seismogenic layer

quasi dynamic modeling of seismicity on a fault with depth variable rate and state dependent friction 1 neither the omori type of clustering prior to and following large earthquakes nor the gutenberg richter distribution are reproducible by present continuous models discrete models on the other hand give rise to more complex and closer to realistic earthquake clustering the objective of this study is twofold to explore the consequences of spatial discreteness on the distribution in time and space of earthquake activity on a fault governed by rate and state friction and to examine the effect of interaction between seismic slip and aseismic creep on aftershock sequences to that end we model a long vertical two dimensional strike slip fault that is governed by rate and state dependent friction and is embedded in a three dimensional elastic half space quasi dynamic motion on the fault is driven by steady displacement applied below the fault and at distance w 2 on either side of the fault plane the model is said to be spatially discrete in that the computational cells are oversized with respect to the critical length scale that is implied by the friction law the model reproduces some of the characteristics of natural seismicity including the nonperiodic recurrence times and the omori type of clustering prior to and following large earthquakes it also produces a wide range of earthquake magnitudes but with a ratio of small to large earthquakes that is in excess with respect to what is inferred form natural catalogs we examined the effect of a stress step applied on the creeping portions of the model and confirmed that aftershock sequences resulting from stress relaxation on creeping segments decay asymptotically to 1 time finally we discuss fundamental differences between seismicity models employing rate and state friction and those employing static kinetic friction

landslide erosion controlled by hillslope material landslide erosion is a primary control of landscape relief a wide ranging analysis of landslide geometry shows that soil based landslides are generally less voluminous than landslides that involve the failure of bedrock and provides refined metrics for estimating the volume of a landslide from the area of the failure

the effect of loading rate on static friction and the rate of fault healing during the earthquake cycle the seismic cycle requires that faults strengthen heal between earthquakes and the rate of this healing process plays a key role in determining earthquake stress drop1 2 3 4 rupture characteristics5 6 and seismic scaling relations2 3 4 7 frictional healing as evidenced by increasing static friction during quasi stationary contact between two surfaces1 8 9 10 11 12 is considered the mechanism most likely to be responsible for fault strengthening2 3 13 14 previous studies however have shown a large discrepancy between laboratory and seismic field estimates of the healing rate2 3 4 14 15 in the laboratory rock friction changes by only a few per cent per order of magnitude change in slip rate whereas seismic stress drop increases by a factor of 2 to 5 per order of magnitude increase in earthquake recurrence interval but in such comparisons it is assumed that healing and static friction are independent of loading rate here i summarize laboratory measurements showing that static friction and healing vary with loading rate and time as expected from friction theory16 17 18 applying these results to seismic faulting and accounting for differences in laboratory seismic and tectonic slip rates i demonstrate that post seismic healing is expected to be retardedfor a period of several hundred days following an earthquake in agreement with recent findings from repeating earthquakes13 14 19 20

geologic constraints on bedrock river incision using the stream power law denudation rate in unextended terranes is limited by the rate of bedrock channel incision often modeled as work rate on the channel bed by water and sediment or stream power the latter can be generalized as ka m s n where k represents the channel bed s resistance to lowenng whose variation with lithology is unknown a is drainage area a surrogate for discharge s is local slope and m and n are exponents whose values are debated we address these uncertainties by simulating the lowering of ancient river profiles using the finite difference method we vary m n and k to match the evolved profile as closely as possible to the corresponding modern river profile over a time period constrained by the age of the mapped paleoprofiles we find at least two end member incision laws ka 0 3 0 5 s for australian rivers with stable base levels and k f a 0 1 0 2 s n for rivers in kauai subject to abrupt base level change the long term lowering rate on the latter expression is a function of the frequency and magnitude of knickpoint erosion characterized by k f incision patterns from japan and california could follow either expression if they follow the first expression with m 0 4 k varies from 10 7 10 6 m 0 2 yr for granite and metamorphic rocks to 10 5 10 4 m 0 2 yr for volcaniclastic rocks and 10 4 10 2 m 0 2 yr for mudstones this potentially large variation in k with lithology could drive strong variability in the rate of long term landscape change including denudation rate and sediment yield

laboratory scale investigation of the 3 d geometry of landslide dams in a u shaped valley abstract landslide dams form when a landslide obstructs narrow and steep valleys in mountainous areas since these dams may fail over a short time and cause secondary geological disasters in the downstream area the stability of such dams must be assessed in an accurate and timely manner the three dimensional 3 d geometry of a landslide dam which is one of the essential indices for stability analyses is highly influenced by the landslide dam formation conditions including the sliding surface dip angle and the valley topography however few studies have focused on the correlation between the 3 d geometry and formation conditions of a landslide dam a photogrammetric system was used to develop a laboratory apparatus to simulate the formation process of a landslide dam and construct a digital model for the 3 d geometry of a landslide dam in a u shaped valley then a series of experiments were designed to systematically investigate the formation process and the 3 d geometry of landslide dams under different combinations of valley bed inclinations 0 4 8 and 12 and sliding surface dip angles 30 45 60 and 75 the results indicate that the sliding surface dip angle has a significant effect on the length and height of a landslide dam whereas the valley bed inclination has a limited effect on the length and height compared with its effect on the relative angles of a landslide dam in addition the cross sectional profiles of landslide dams can be classified into three categories namely symmetric asymmetric and flat shapes and these profiles are predominantly affected by the sliding surface dip angle instead of the valley bed inclination subsequently a mathematical model for predicting the 3 d geometry of a landslide dam was presented according to the experimental results and it was verified by the experimental data and 42 historical cases of landslide dams based on the proposed model the predicted 3 d geometry of the tangjiashan landslide dam triggered by the wenchuan earthquake of 2008 was consistent with its actual geometry which confirmed the reliability of the prediction model in practical applications the findings of our study contribute to the establishment of evidence based disaster prevention and mitigation measures for landslide dams

does aftershock duration scale with mainshock size 1 it has been claimed that aftershock duration scales with the mainshock recurrence interval dieterich 1994 this implies a scaling between aftershock duration and mainshock magnitude to see if such a scaling exist we compare properties of aftershock sequences associated with mainshocks whose size span several magnitude units earthquake properties were examined along two northern california fault segments one is the calaveras fault another is a northern segment of the san andreas fault the first study area contains the rupture area of the m6 2 1984 morgan hill and the latter is adjacent the southern end of the m7 1 1989 loma prieta rupture both the morgan hill and the loma prieta aftershock activities lasted 1 3 108 seconds on the other hand aftershock activities of small to moderate mainshocks lasted about 1 2 106 seconds nevertheless there is no evidence for scaling between mainshock size and aftershock duration for moderate to small mainshocks it thus seems that large earthquakes because they break the entire seismogenic depth and interact with deeper parts of the crust trigger a relaxation mechanism that is inactive during aftershock activity due to moderate to small quakes and whose characteristic relaxation time is much longer than that of the brittle crust current seismicity models do not provide explanation for these observations

slope area relationships and sediment dynamics in two alpine streams the paper focuses on the channel network of alpine basins attempting to interpret channel reaches in terms of response to erosion and deposition processes two basins in the dolomites north eastern italy were considered the rio cordon 5 km2 and the upper boite river 163 km2 the channel network was extracted from raster type digital elevation models dem using a slope area threshold criterion a contribution area index cai which combines drainage area a and local slope s cai a0 5s was used to identify channel heads the channel network extracted from the dem was then analysed to recognize cells showing a value of cai lower than the threshold adopted for channel initiation contiguous cells with low values of cai define channel reaches with low transport efficiency field surveys carried out for some selected cases showed a good agreement between prevailing sediment deposition predicted by the analysis of the channel network and observed channel morphological features sediment sources mapped in two study basins were also analysed in relation to the location of channels with high potential for sediment deposition this made it possible to classify the potential role of different types of sediment sources with regard to basin sediment yield topographic characteristics of the channel network expressed by cai were compared with a classification of channel morphology in the rio cordon it was found that cells with low values of cai frequently occur in the riffle pool reaches whereas the percentage significantly decreases in step pool and bedrock channels copyright 2003 john wiley sons ltd

fixed recurrence and slip models better predict earthquake behavior than the time and slip predictable models 1 repeating earthquakes 1 the behavior of individual events in repeating earthquake sequences in california taiwan and japan is better predicted by a model with fixed inter event time or fixed slip than it is by the time and slip predictable models for earthquake occurrence given that repeating earthquakes are highly regular in both inter event time and seismic moment the time and slip predictable models seem ideally suited to explain their behavior taken together with evidence from the companion manuscript that shows similar results for laboratory experiments we conclude that the short term predictions of the time and slip predictable models should be rejected in favor of earthquake models that assume either fixed slip or fixed recurrence interval this implies that the elastic rebound model underlying the time and slip predictable models offers no additional value in describing earthquake behavior in an event to event sense but its value in a long term sense cannot be determined these models likely fail because they rely on assumptions that oversimplify the earthquake cycle we note that the time and slip of these events is predicted quite well by fixed slip and fixed recurrence models so in some sense they are time and slip predictable while fixed recurrence and slip models better predict repeating earthquake behavior than the time and slip predictable models we observe a correlation between slip and the preceding recurrence time for many repeating earthquake sequences in parkfield california this correlation is not found in other regions and the sequences with the correlative slip predictable behavior are not distinguishable from nearby earthquake sequences that do not exhibit this behavior

similar microearthquakes observed in western nagano japan and implications for rupture mechanics 1 we have applied a waveform cross correlation technique to study the similarity and the repeatability of more than 21 000 microearthquakes 0 m 4 5 in the aftershock zone of the 1984 western nagano earthquake in central japan we find that the seismicity in this particular intraplate fault essentially consists of no repeating earthquakes that occurred on the same patch of the fault in a quasiperiodic manner in the study period between 1995 and 2001 on the other hand we identify a total of 278 doublets and 62 multiplets 807 events that occurred consecutively within seconds to days on the basis of the relative arrival times of the p and s waves we have obtained precise relative locations of these consecutive events with an error between several meters to a few tens of meters there is a clear lower bound on the distances measured between these consecutive events and the lower bound appears to be proportional to the size of the first events this feature is consistent with what rubin and gillard 2000 have observed near the san juan bautista section of the san andreas fault shear stress increases at the edge of an earthquake rupture and the rupture edge becomes the most likely place where the second events are initiated the observed minimum distance thus reflects the rupture size of the first events the minimum distance corresponds to the rupture size calculated from a circular fault model with a stress drop of 10 mpa we found that using different time windows results in a slight difference in the delay time estimates and the subsequent projection locations which may reflect the finite size nature of earthquake ruptures

numerical simulation of the kamaishi repeating earthquake sequence change in magnitude due to the 2011 tohoku oki earthquake abstract we conducted numerical simulations of a repeating earthquake sequence on the plate boundary off the shore of kamaishi northeastern japan assuming rate and state dependent friction laws uchida et al 2014 reported that the kamaishi repeating earthquakes showed an increase in magnitude and a decrease in recurrence interval after the 2011 tohoku oki earthquake m 9 but an approximately constant magnitude m 4 9 and a regular recurrence interval 5 5 years before the tohoku oki earthquake a m 5 9 event occurred just after the m 9 event and was followed by a m 5 5 event we considered a fault patch of velocity weakening friction with frictional parameters leading to seismic slip confined in its central part of the patch afterslip due to the m 9 event was involved in the model to increase the loading rate on the patch the simulation successfully reproduced increasing magnitude and decreasing recurrence time caused by the afterslip a m 6 class event in which seismic slip spread over the entire area of the patch occurred just after the m 9 event for the aging law and the nagata law when we assumed the aging law with frictional parameters which lie near the boundary between leading to slip on the entire patch and slip confined in its central part the m6 class event was followed by a m 5 5 class event furthermore we examined a conditionally stable large patch that contained a small unstable patch this model also reproduced a m 6 class event after the m 9 event in these models stress outside the confined area of the path is released before a dynamic event under a constant low loading rate whereas the stress perturbation due to afterslip within the seismic cycle induces a dynamic event on the entire patch

repeating aftershocks of the great 2004 sumatra and 2005 nias earthquakes abstract we investigate repeating aftershocks associated with the great 2004 sumatra andaman mw 9 2 and 2005 nias simeulue mw 8 6 earthquakes by cross correlating waveforms recorded by the regional seismographic station psi and teleseismic stations we identify 10 and 18 correlated aftershock sequences associated with the great 2004 sumatra and 2005 nias earthquakes respectively the majority of the correlated aftershock sequences are located near the down dip end of a large afterslip patch we determine the precise relative locations of event pairs among these sequences and estimate the source rupture areas the correlated event pairs identified are appropriately referred to as repeating aftershocks in that the source rupture areas are comparable and significantly overlap within a sequence we use the repeating aftershocks to estimate afterslip based on the slip seismic moment scaling relationship and to infer the temporal decay rate of the recurrence interval the estimated afterslip resembles that measured from the near field geodetic data to the first order the decay rate of repeating aftershocks as a function of lapse time t follows a power law decay 1 t p with the exponent p in the range 0 8 1 1 both types of observations indicate that repeating aftershocks are governed by post seismic afterslip

geomorphic indexing of landslide dams evolution abstract landslide dams are rather common events in hilly and mountainous areas and they occur when a landslide reaches a valley floor closing the riverbed if they form a lake basin unstable landslide dams can have catastrophic consequences when they occur in upstream of populated regions landslide dam behavior is not completely understood yet however several studies suggested implementing geomorphological index in order to assess their formation and evolution these indexes result from the composition of two or more morphological attributes that characterize the landslide e g landslide volume or length and the involved river valley e g valley width the objective of this work is the definition of a procedure based on the joint use of different indexes to assess landslide dams evolution over large areas e g entire river catchment or even a region or a nation and in short times in order to be used for emergency response or for planning activities about 300 landslide dam events collected in italy were analyzed and some state of the art geomorphological indexes were applied to characterize the damming phenomena at the national scale to overcome some limitations of the aforementioned indexes we introduce two new indexes the morphological obstruction index and the hydromorphological dam stability index the former combines the river width and the landslide volume and it can be used to identify the conditions associated to dam formation discriminating between circumstances where a landslide dam is formed and circumstances where it is not the latter uses a simplified stream power formulation combining the upstream catchment area and the local slope gradient to account for the river energy this index allows evaluating the stability of a dam in near real time as soon as it occurs and can be used to discriminate between stable and unstable dams if compared with the reviewed state of the art indexes the newly proposed ones show an improvement in the forecasting effectiveness and have the advantage of being based on morphometric input parameters that can be easily and quickly assessed on a distributed way even over large areas we propose a tool that is based on the joint use of the newly proposed indexes and that can be used to provide fast and effective assessment on landslide dam formation and stability during emergency or planning activities

location performance of a sparse regional network a key element in successful seismic verification of a nuclear test ban treaty is the capability of a sparse network of seismic stations to accurately locate regional events we have investigated the regional location accuracy of the regional seismic test network rstn a five element three component network in eastern north america using 62 events varying in size from magnitude 3 0 to 5 1 applying an algorithm which allows inclusion of back azimuth estimates as well as travel times we determined a median location error of 23 km for the data set relative to the pde locations considering the large station spacing 1500 km and a few data used in the locations 2 to 4 stations the rstn location accuracy is remarkably good the results imply that a widely spaced network of single three component stations could reliably locate regional seismic events copyright american geophysical union 1989

postseismic response of repeating aftershocks the recurrence intervals of repeating earthquakes on the san andreas fault in the loma prieta aftershock zone follow the characteristic 1 t decay of omori s law a model in which these earthquakes occur on isolated patches of the fault that fail in stick slip with creep around them can explain this observation in this model the recurrence interval is inversely proportional to the loading rate due to creep logarithmic velocity strengthening friction predicts 1 t decay in creep rate following the mainshock the time dependence of recurrence is inconsistent with a simple viscous constitutive relationship which predicts an exponential decay of loading rate thus our observations imply postseismic slip at seismogenic depth under a power law rheology the time dependence of postseismic deformation measured geodetically may be diagnostic of whether postseismic deformation is caused by creep or possible viscoelastic deformation at greater depths

variations in rupture process with recurrence interval in a repeated small earthquake in theory and in laboratory experiments friction on sliding surfaces such as rock glass and metal increases with time since the previous episode of slip1 this time dependence is a central pillar of the friction laws widely used to model earthquake phenomena2 3 on natural faults other properties such as rupture velocity4 5 porosity and fluid pressure6 11 may also vary with the recurrence interval eighteen repetitions of the same small earthquake separated by intervals ranging from a few days to several years allow us to test these laboratory predictions in situ the events with the longest time since the previous earthquake tend to have about 15 larger seismic moment than those with the shortest intervals although this trend is weak in addition the rupture durations of the events with the longest recurrence intervals are more than a factor of two shorter than for the events with the shortest intervals both decreased duration and increased friction are consistent with progressive fault healing during the time of stationary contact

radiography of a normal fault system by 64 000 high precision earthquake locations the 2009 l aquila central italy case study 1 we studied the anatomy of the fault system where the 2009 l aquila earthquake mw 6 1 nucleated by means of 64 k high precision earthquake locations spanning 1 year data were analyzed by combining an automatic picking procedure for p and s waves together with cross correlation and double difference location methods reaching a completeness magnitude for the catalogue equal to 0 7 including 425 clusters of similar earthquakes the fault system is composed by two major faults the high angle l aquila fault and the listric campotosto fault both located in the first 10 km of the upper crust we detect an extraordinary degree of detail in the anatomy of the single fault segments resembling the degree of complexity observed by field geologists on fault outcrops we observe multiple antithetic and synthetic fault segments tens of meters long in both the hanging wall and footwall along with bends and cross fault intersections along the main fault and fault splays the width of the l aquila fault zone varies along strike from 0 3 km where the fault exhibits the simplest geometry and experienced peaks in the slip distribution up to 1 5 km at the fault tips with an increase in the geometrical complexity these characteristics similar to damage zone properties of natural faults underline the key role of aftershocks in fault growth and co seismic rupture propagation processes additionally we interpret the persistent nucleation of similar events at the seismicity cutoff depth as the presence of a rheological i e creeping discontinuity explaining how normal faults detach at depth