model test study on monitoring dynamic process of slope failure through spatial sensor network landslides represent a major type of natural hazards worldwide for development of risk mitigation capabilities an effective system for monitoring dynamic process of slope failure capable of gathering spatially distributed information before during and after a landslide occurrence at real time manner is essential a spatial sensor network ssn which integrates the real time communication infrastructure and observations from in situ sensors and remote sensing platforms offers an efficient and effective approach for such purpose in this paper a ssn based landslide monitoring system was designed and evaluated through a model test study conducted at tongji university china this system munold multi sensor network for observing landslide disaster has been designed as a comprehensive monitoring framework including sensor observations multi channel wireless communication remote data storage visualization data processing and data analysis in this model test study initial experimentation demonstrated the capabilities of the munold system for collecting real time information about the dynamic process and propagation of slope failure innovatively generated from the high speed stereo images the sequential surface deformation vector field can be created and may exhibit the dynamic process during the extremely critical and short period of the slope failure after this model test study the munold system is going to be further improved and extended in a landslide prone region in sichuan province china

deep structure of northern mississippi embayment in september 1980 the u s geological survey conducted a seismic refraction investigation of the northern mississippi embayment during the investigation 34 shots from nine shotpoints were recorded along a series of profiles the profiles were parallel to and across an inferred precambrian rift zone which is outlined by a series of magnetic anomalies and covers an area at least 200 km 125 mi long and 70 km 45 mi wide along the northeast southwest trending axis of the rift a 0 7 to 1 1 km 2 297 to 3 609 ft thick 1 8 km sec layer representing the unconsolidated tertiary and cretaceous sediments overlies a 2 km 6 562 ft thick 5 95 km sec layer representing a paleozoic carbonate sequence beneath the carbonates is a 3 km 9 843 ft thick low velocity layer which probably consists of late precambrian clastics the presence of this low velocity layer is indicated on the seismic profiles by an abrupt cutoff of the 5 95 km sec arrivals at about 20 km 12 mi from the shotpoints this cutoff is followed by a 30 to 40 km 20 to 25 mi long zone of no arrivals beyond which are seen delayed arrivals from a 6 2 km sec crystalline basement the 11 km 6 8 mi thick 6 2 km sec basement overlies a lower crus composed of a 6 6 km sec layer whose thickness decreases to the northeast owing to its replacement by an anomalous high velocity 7 3 km sec basal layer the base of the crust ranges from a 39 km 24 mi depth at the southern end of the profile to a 46 km 29 mi depth at the northern end where the 7 3 km sec layer is 20 km 12 mi thick below the base of the crust moho the upper mantle has a velocity of 8 0 km sec the velocity structure beneath the west flank of the embayment is simpler than that of the axis 5 95 6 2 6 6 7 3 and 8 0 km sec the low velocity layer is absent and the anomalous 7 3 km sec layer is thinner than along the axial profile the profiles perpendicular to the rift show that the low velocity layer is restricted to the axial zone and that the anomalous 7 3 km sec basal crustal layer reaches maximum thickness there the tectonic model proposed to explain the origin of this embayment velocity structure includes a late precambrian mantle plume that intruded the lower crust of the northern embayment causing uplift and or crustal stretching and subsequent rifting of the axial area this was followed by erosion subsidence and subsequent deposition of sediments in the resulting trough

the significance of channel recharge rates for estimating debris flow magnitude and frequency the quantification of debris flow hazard requires estimates of debris flow frequency and magnitude several methods have been proposed to determine the probable volume of future debris flows from a given basin but most have neglected to account for debris recharge rates over time which may lead to underestimation of debris flow volumes in basins with rare debris flows this paper deals with the determination of debris recharge rates in debris flow channels based on knowledge of debris storage and the elapsed time since the last debris flow data are obtained from coastal british columbia and a relation is obtained across a sample of basins with similar terrain and climatic conditions for rennell sound on the west coast of the queen charlotte islands the power law relation for area normalized recharge rate rt versus elapsed time te was rt 0 23te 0 58 with an explained variance of 75 per cent a difference in recharge rates may exist between creeks in logged and unlogged forested terrain the power function for undisturbed terrain was rt 0 20te 0 49 while the function for logged areas was rt 0 30te 0 77 this result suggests that for the same elapsed time since the last debris flow clearcut gullies tend to recharge at a slower rate than creeks in old growth forest this finding requires verification particularly for longer elapsed times since debris flow but would have important implications for forest resource management in steep coastal terrain this study demonstrates that commonly used encounter probability equations are inappropriate for recharge limited debris flow channels copyright 2005 john wiley sons ltd

the potential impact of climate change on typhoon triggered landslides in taiwan 2010 2099 abstract in the western north pacific including taiwan typhoons tropical cyclones and rainfall rates are predicted to intensify as a result of climate change because typhoons are the major triggers of shallow landslides in taiwan landslide activity is expected to increase as global warming continues to assess the worst scenario of landslide occurrence in a mountainous watershed till the end of the century this study developed a method to select a global climate model gcm from 21 available gcms and correct its monthly precipitation data before downscaling annual maximum 24 h rainfall from the corrected gcm data as input to the factor of safety model for landslide prediction average annual maximum rainfall is expected to increase from 322 mm in 1960 2008 to 371 mm in 2010 2099 average total unstable area is expected to increase from 1135 ha in 1960 2008 to 1280 ha in 2010 2099 a 12 increase as a first attempt to assess landslide activity due to global warming this study is useful as a reference for watershed management in taiwan the results must be evaluated in light of uncertainties caused by the correction and downscaling of gcm data and the input parameters to the slope stability model

local earthquake wave propagation through mississippi embayment sediments part ii influence of local site velocity structure on qp qs determinations elastic near surface structure and receiver depth effects are seen to control body wave amplitude spectra in the band from 2 to 50 hz for local earthquake observations in the new madrid seismic zone p and s wave spectral peaks are created by resonance in shallow low velocity zones and spectral nulls are created by interference of direct and free surface reflections due to receiver depth these wave propagation effects dominate sp s spectral ratios and mimic anelastic attenuation effects by making it appear that s waves are deficient in higher frequencies relative to sp waves there is no evidence from sp s spectral ratios that unconsolidated sediments of the mississippi embayment are highly attenuating dominance of p and s wave resonance suggests that the unconsolidated sediments amplify rather than attenuate seismic waves at high frequency this has important implications for estimating hazards from strong ground motions in the area in the absence of any identifiable anelastic attenuation effect in the spectral ratio the only allowable q p q s relationship for embayment sediments is that q s 3 q p based on consideration of wave travel times manuscript received 11 march 2003

rainfall characteristics for anisotropic conductivity of unsaturated soil slopes the purpose of this study was to investigate the effects of the anisotropic ratio on the stability of slopes using the reliability index approach a numerical analysis of the relationship between the three rainfall patterns advanced normal and delayed and the anisotropic ratios was designed this study also considered three different soil properties sand silt and clay to simulate rain infiltration in this study probability analysis was used to evaluate the stability of unsaturated soil slopes the finite element computer program geo studio was used to simulate the process of rainwater infiltrating a slope the pore water pressure results evaluated from seepage analysis seep w were imported into the slope stability program slope w results for the anisotropic ratio of hydraulic conductivity indicate that when the anisotropic ratios become higher the reduction in the reliability index is insignificant in addition the simulation results indicated that when saturated hydraulic conductivity ks was less than rainfall intensities i the percentage probability of the occurrence of a landslide was larger than when ks was greater than i finally in the cases of anisotropic ks stability of the high ratio soil slopes was not found to be sensitive to the reliability index variation during the simulation period moreover when ks was greater than i slope stability decreased earlier than was the case in the opposite situation

local earthquake wave propagation through mississippi embayment sediments part i body wave phases and local site responses p and s body waves from microearthquakes in the new madrid seismic zone nmsz are investigated at selected sites in an effort to understand wave propagation from future large earthquakes earthquake body waveforms display distinctive features that constrain the nature of p and s wave local site responses and wave propagation within the unconsolidated mississippi embayment sediments modeling of the waveforms demonstrates that a near surface low velocity zone is characteristic of structure within the upper 60 m of the sedimentary column and produces large p and s wave resonance effects that can be used to infer near site conditions site resonance effects change because of velocity heterogeneity between individual receivers but imply that embayment sediments will substantially amplify ground motions at high frequencies site resonance affects p and s wave amplitude spectra and can bias estimates of source and anelastic attenuation parameters travel times of observed body wave phases such as p ppphp the first p wave reverberation within the entire sedimentary column ps sp s and ssphp can be used to estimate the average wave slownesses and poisson s ratio within the embayment sediments an average poisson s ratio of 0 44 is obtained for the central nmsz under station pebm detailed s wave velocities are derived for a nafe drake sediment model using acoustic well logs and the travel time constraints of observed seismic phases v p v s ratios vary from 5 5 near the surface to approximately 2 4 at the base of the sediments use of the well log data in wave calculations also explains much of the nature of p and s wave coda within the waveforms and shows that 1d heterogeneity is a first order influence on seismic wave propagation within the mississippi embayment manuscript received 11 march 2003

climate change effects on landslides along the southwest coast of british columbia abstract antecedent rainfall and short term intense rainfall both contribute to the temporal occurrence of landslides in british columbia these two quantities can be extracted from the precipitation regimes simulated by climate models this makes such models an attractive tool for use in the investigation of the effect of global warming on landslide frequencies in order to provide some measure of the reliability of models used to address the landslide question the present day simulation of the antecedent precipitation and short term rainfall using the daily data from the canadian centre for climate modelling and analysis model cgcm is compared to observations along the south coast of british columbia this evaluation showed that the model was reasonably successful in simulating statistics of the antecedent rainfall but was less successful in simulating the short term rainfall the monthly mean precipitation data from an ensemble of 19 of the world s global climate models were available to study potential changes in landslide frequencies with global warming most of the models were used to produce simulations with three scenarios with different levels of prescribed greenhouse gas concentrations during the twenty first century the changes in the antecedent precipitation were computed from the resulting monthly and seasonal means in order to deal with models suspected difficulties in simulating the short term precipitation and lack of daily data a statistical procedure was used to relate the short term precipitation to the monthly means the qualitative model results agree reasonably well and when averaged over all models and the three scenarios the change in the antecedent precipitation is predicted to be about 10 and the change in the short term precipitation about 6 because the antecedent precipitation and the short term precipitation contribute to the occurrence of landslides the results of this study support the prediction of increased landslide frequency along the british columbia south coast during the twenty first century

the role of debris supply conditions in predicting debris flow activity debris flow frequency and magnitude were determined for 33 basins in southwest british columbia basins were first classifiedaseitherweathering limitedortransport limitedusingadiscriminantfunctionbasedondebris contributingarea an area weighted terrain stability number and drainage density multiple regression was used to predict magnitude peak discharge frequency and activity frequency times magnitude within each group of basins model performance was improved by stratifying the total sample of debris flow basins into weathering and transport limited groups explained varianceincreasedbyanaverageof15percentinthetransport limitedsample indicatingthatsedimentsupplyconditionsin themoreactivebasinsarefundamentalinpredictingdebrisflowactivity anindependenttestoftheregressionmodelswith 11basinsyieldedgenerallygoodresultsfordebrisflowmagnitudeandpeakdischarge predictionofdebrisflowfrequency provedproblematicalinweathering limitedbasins themethodsdevelopedhereprovideestimatesofdebrisflowattributes in basins for which few data on past events are available copyright 1999 john wiley sons ltd

analysis of climatic influences on slope microseismic activity and rockfalls case study of the matterhorn peak northwestern alps abstractrock instability and rockfalls are commonly preceded by the initiation and propagation of cracks this process is accompanied by the release of microseismic energy which can be detected by means of an appropriate monitoring system because an increase in rockfall events have been observed in the matterhorn peak area since 2003 in 2007 a microseismic monitoring system and a thermometric monitoring system were installed on the italian side of the matterhorn peak close to the j a carrel hut as part of the interreg iiia alcotra permadataroc project the objective of the installation was to determine whether this instability increase was connected to climatic fluctuations detailed analysis of the recorded microseismic data shows a spatial concentration of microseismic activity on the western side of the investigated slope and a correlation of these data with thermal information shows that the temporal concentration of the microseismic activity could be traced back to the transitions from warm

microtremor observations of deep sediment resonance in metropolitan memphis tennessee we measured site resonance periods throughout metropolitan memphis tennessee the site resonance was derived from recordings of ambient microtremor and is a direct measurement of seismic ground shaking in the memphis metropolitan area the period t0 in s is predicted by the empirical relation t0 0 39899 7 8922 10 3h 3 0634 10 6h2 350 h 1100 m where h is the thickness in m of the unconsolidated sediments that overly hard paleozoic rocks assuming that a quarter wavelength relationship governs the relationship between resonant period sediment thickness and average shear wave speed we estimate the average shear wave speed of unconsolidated sediments as a function of sediment thicknesses vs 521 15 0 37459h 350 h 1100 m the scatter in the observations and discordance with earlier work suggests that caution is warranted in applying these values of wave speed indiscriminately to sites in the absence of further detailed work

qp qs relations in the sedimentary basin of the upper mississippi embayment using converted phases abstract three component digital seismograms recorded by the 40 panda portable array for numerical data acquisition stations in the new madrid seismic zone were analyzed to study seismic wave attenuation in the sedimentary basin using the spectral ratio method a prominent s to p s p converted phase was generated at the boundary between the uppermost sedimentary basin and the underlying paleozoic rocks the direct s wave on the horizontal component is characterized by a lower frequency content than that of the converted s p wave on the vertical component the differences in frequency content between the direct s and the s p converted waves can be attributed to the different attenuation effects between p and s waves in the unconsolidated sediments the spectral ratio between the low frequency s wave and the high frequency converted s p wave from the bottom of the sediments can be used to yield a relationship between q p and q s in the sediments results from panda stations with well constrained spectral ratios in the frequency range from 2 to 25 hz give the q p value ranging from 25 to 60 and q s from 25 to 30 for the sedimentary basin in the upper mississippi embayment

without power landslide inventories in the face of climate change projected scenarios of climate change involve general predictions about the likely changes to the magnitude and frequency of landslides particularly as a consequence of altered precipitation and temperature regimes whether such landslide response to contemporary or past climate change may be captured in differing scaling statistics of landslide size distributions and the erosion rates derived thereof remains debated we test this notion with simple monte carlo and bootstrap simulations of statistical models commonly used to characterize empirical landslide size distributions our results show that significant changes to total volumes contained in such inventories may be masked by statistically indistinguishable scaling parameters critically depending on among others the size of the largest of landslides recorded conversely comparable model parameter values may obscure significant i e more than twofold changes to landslide occurrence and thus inferred rates of hillslope denudation and sediment delivery to drainage networks a time series of some of earth s largest mass movements reveals clustering near and partly before the last glacial interglacial transition and a distinct step over from white noise to temporal clustering around this period however elucidating whether this is a distinct signal of first order climate change impact on slope stability or simply coincides with a transition from short term statistical noise to long term steady state conditions remains an important research challenge copyright 2011 john wiley sons ltd

regional wave propagation in tanzania east africa 1 crust and upper mantle structure under tanzania east africa is investigated using broadband waveforms and phase travel times collected from regional events recorded by the 1994 1995 tanzania broadband seismic experiment broadband displacement waveforms from the ml 5 9 rukwa graben earthquake 18 august 1994 are modeled using a wave number integration algorithm and a new phase time inversion technique to infer a very simple crustal and upper mantle model that can be used for waveform studies of other regional earthquakes in the area displacement amplitudes for all phases in the data are predicted quite well using source parameters determined from a previous study of teleseismic waveforms the crust is parameterized by a linear gradient in velocity defined by surface and moho p velocities poisson s ratio and crustal thickness this simple parameterization is sufficient to explain arrival times and waveshapes of the three component waveforms recorded between 200 and 800 km at stations located on the craton and mozambique belt the s wave train consists of sn multiple sn and critically reflected s wave multiples in the crustal waveguide in addition to the fundamental mode rayleigh wave high phase velocity critical s wave reflections are seen to form the low group velocity lg phase prominent sp depth phases are seen in the regional waveform data which can be used to infer accurate source depths for events in the region the tanzania craton and adjacent mozambique belt crustal structure is simple and laterally homogeneous showing few effects of rift disruption high wave velocities in the uppermost mantle suggest little thermal modification from rifting processes of the east african rift

a hydroclimatic threshold for landslide initiation on the north shore mountains of vancouver british columbia landslides triggered by rainfall are the cause of thousands of deaths worldwide every year one possible approach to limit the socioeconomic consequences of such events is the development of climatic thresholds for landslide initiation in this paper we propose a method that incorporates antecedent rainfall and streamflow data to develop a landslide initiation threshold for the north shore mountains of vancouver british columbia hydroclimatic data were gathered for 18 storms that triggered landslides and 18 storms that did not discriminant function analysis separated the landslide triggering storms from those storms that did not trigger landslides and selected the most meaningful variables that allow this separation discriminant functions were also developed for the landslide triggering and nonlandslide triggering storms the difference of the discriminant scores cs for both groups is a measure of landslide susceptibility during a storm the variables identified that optimize the separation of the two storm groups are 4 week rainfall prior to a significant storm 6 h rainfall during a storm and the number of hours 1 m3 s discharge was exceeded at mackay creek during a storm three thresholds were identified the landslide warning threshold lwt is reached when cs is 1 the conditional landslide initiation threshold ctli is reached when cs is zero and it implies that landslides are likely if 4 mm h rainfall intensity is exceeded at which point the imminent landslide initiation threshold itli is reached the lwt allows time for the issuance of a landslide advisory and to move personnel out of hazardous areas the methodology proposed in this paper can be transferred to other regions worldwide where type and quality of data are appropriate for this type of analysis

frequency and magnitude of debris flows on cheekye river british columbia abstract natural hazard and risk assessments are predicated on a detailed understanding of the relationship between frequency and magnitude of the hazardous process under investigation when information is sought from the deep past i e several thousand years continuous event records do not exist and the researcher has to rely on proxy data to develop the frequency magnitude f m model such work is often prohibitively expensive and few well researched examples for mass movement are available worldwide the cheekye fan is a desirable location for land development and has a depth and breadth of previous research unprecedented on any debris flow fan in canada we pursued two principal strains of research to formulate a reliable f m relationship the first focuses on stratigraphic analyses combined with radiometric dating and dendrochronology to reconstruct a comprehensive picture of holocene debris flow activity the second approach examines hydrological limitations of rock avalanche evolution into debris flows through either entrainment of saturated sediments or by failure of a landslide generated dam and upstream impoundment we thus hypothesize that debris flows from cheekye river can be separated into two quasi homogenous populations those that are typically triggered by relatively small debris avalanches slumps or rock falls or simply by progressive bulking of in stream erodible sediments and those that are thought to result from transformation of rock avalanches our work suggests that debris flows exceeding some 3 million m3 in volume are unlikely to reach the cheekye fan as a result of limited water available to fully fluidize a rock avalanche this analysis has also demonstrated that in order to arrive at reasonable estimates for the frequency and magnitude of debris flows on a complex alluvial fan significant multidisciplinary efforts are required without the significant precursor investigations and the additional efforts of this study life and property may be jeopardized or the design of debris flow mitigation may be subject to considerable and unquantifiable error

characteristics of short period wave propagation in regions of fennoscandia with emphasis on lg abstract wave propagation of crustal phases in particular lg near the arcess array in northern norway is examined and compared to propagation characteristics near the noress array in southern norway relying on array analysis we show that ray theory explanations of arrivals in local and regional seismograms are very useful in deducing the composition of the crustal wave trains frequency wavenumber analysis is applied to the array data to identify the arrivals then a composite of array beams is used to approximate each event record sections of composite seismograms are constructed for different directions from arcess to study propagational characteristics with distance and azimuth and then compared to composite seismogram record sections from noress to study different regional characteristics to model the observed character of lg and rg synthetic record sections are constructed by wavenumber integration in velocity models representative of structure in the different regions the results show that rg propagation distance varies significantly between regions and that the velocity gradient in the lower crust is the dominant factor in specifying lg characteristics in the baltic shield region lg is dominated by several discrete arrivals representing multiple moho reflections or by multiple moho reflections and turning waves with each multiple confined to a small distance range so that only one multiple set dominates at each distance furthermore we demonstrate that incomplete knowledge of the propagation characteristics leads to mislocations of local and regional events and inhibits source depth discrimination of events we identify three earthquakes in the arcess data set based on source depths these are constrained by phase velocities and depth phases none of which were properly identified by the automatic array detection software

unexpected values of qs in the unconsolidated sediments of the mississippi embayment we studied the attenuation of shear waves at three sites in the mississippi embayment using data recorded in boreholes drilled to depths of up to 60 m the source was a highly repeatable compressed air driven hammer to estimate attenuation we used a spectral ratio technique for fixed depth and variable frequency the best fit line for each depth z gives a measure of the cumulative attenuation indicated by z then we fit a straight line to z for a range of values of z the slope of this line gives an estimate of the average attenuation per distance and was used to determine an average q s for one of the sites newport northeastern arkansas q s ranges between 34 1 5 m z 44 2 m and 44 1 5 m z 51 8 m these values are significantly higher than the more typical value of about 10 determined for unconsolidated sediments by other authors in addition these high values correspond to sediments with low average shear wave velocity about 300 m sec in contrast average q s and velocity for sediments in shelby forest near memphis tennessee are 22 and 348 m sec 22 6 m z 60 1 m respectively therefore these results go against the conventional wisdom that low velocity implies low q for the third site marked tree northeastern arkansas average q s and velocity are 18 and 251 m sec 9 8 m z 33 6 m respectively this site is about 75 km from newport and the differences in attenuation appear related to differences in lithology manuscript received 5 april 2001

bulk sediment qp and qs in the mississippi embayment central united states we have estimated p wave ands wave anelastic attenuation coefficients for the thick unconsolidated sediments of the mississippi embayment central united states using the spectral distance decay of explosion p and rayleigh waves the sediment trapped p wave psed is observed to ranges of 80 km at 10 hz and 1 hz rayleigh waves are observed out to 130 km from a 5000 lb borehole explosion in the northern part of the embayment rayleigh waves of 4 hz are seen to distances of 3 km from a smaller 50 lb explosion analysis of the group velocity and amplitude distance decay of both waves yields an average qs of 100 and qp of 200 for embay ment sediments that are independent of frequency scatter in the q estimates comes from interference of multiple p wave reverberations and rayleigh wave modes the attenuation model is self consistent in that it is the same as obtained by the analysis of synthetic seismograms using the inferred q values inferred qp and qs values are more than three times higher than previous estimates and imply that unconsolidated sediments of the embayment do not significantly attenuate small strain earthquake ground motions these estimates represent a lower bound to q of the sediments since significant scattering is observed in the waveform data that contributes to the distance decay of wave amplitude higher q values also imply that the unconsolidated sedi ments of the embayment will form an efficient wave guide for surface waves radiated from shallow earthquakes or large earthquakes that rupture into the sediments pro ducing high amplitude long duration wave trains that should be considered in earth quake hazard assessments

shallow shear wave velocity and q structures at the el centro strong motion accelerograph array at three sites in the u s geological survey el centro strong motion accelerograph array eo5 eo6 and eo7 we have used the dispersive and attenuative properties of artificially generated rayleigh waves to infer the depth dependence of shear wave velocity and quality factor q and a site dependent equivalent elastic source spectrum this approach provides an inexpensive means for determining two important quantities and q required to estimate the response of sites to earthquakes we find that the shear velocities and the gradients in shear velocities down to depths of 100 meters at station eo6 in the wedge between the imperial and brawley faults are nearly twice those at either station eo5 and eo7 east and west respectively of the wedge also the seismogram character surface wave dispersion and shear wave velocity structure at stations eo5 and eo7 are similar to each other while they are different from eo6 these results show significant structural differences between the wedge beneath eo6 and surrounding areas the anomalously high accelerations recorded at eo6 during the 1979 imperial valley earthquake may be related to these differences

attenuation of body waves in the central new madrid seismic zone abstract data from the portable array for numerical data acquisition panda deployment in the central part of the new madrid seismic zone have been used to study the attenuation of body waves the spectral decay technique is used to analyze acceleration amplitude spectra of both p and s waves in a frequency range of 5 to 25 hz in order to obtain the high frequency attenuation parameter a multiple weighted least squares method is applied to obtain the site attenuation factor 0 at each station and to get d dr which were interpreted in terms of a two layer q structure consisting of a sedimentary layer overlying the upper crust the 0 values for s waves are stable and show a positive correlation with sediment thickness the 0 values for p waves in the sediments show significant scatter which may be due to greater sensitivity of p wave attenuation to water content of the soils than that of s waves which gave more stable 0 values consistency checks on the assumptions made in obtaining the p and s values are made by studying the source spectrum of several events and the differential sp s from the spectral ratio of the converted sp to s phases the three sets of values are found to be internally consistent but our results are limited to deep sediment sites since the complete vertical distribution of q with sediment depth is not known

ancient landslide dam events in the jishi gorge upper yellow river valley china some scholars have argued that the formation and outburst of an ancient dammed lake in the jishi gorge at ca 3700 cal yr bp resulted in the destruction of lajia the site of a famous prehistoric disaster in the guanting basin upper yellow river valley china however the cause of the dammed lake and the exact age of the dam breaching are still debated we investigated ancient landslides and evidence for the dammed lake in the jishi gorge including dating of soil from the shear zone of an ancient landslide sediments of the ancient dammed lake and loess above lacustrine sediments using radiocarbon and optically stimulated luminescence osl dating methods six radiocarbon dates and two osl dates suggested that the ancient landslides and dammed lake events in the jishi gorge probably occurred around 8100 cal yr bp and the ancient dammed lake was breached between 6780 cal yr bp and 5750 cal yr bp hence the outburst of the ancient dammed lake in the jishi gorge was unrelated to the ruin of the lajia site but likely resulted in flood disasters in the guanting basin around 6500 cal yr bp

geomorphic response of lillooet river british columbia to meander cutoffs and base level lowering abstract a detailed record of channel profiles slopes and stream discharge on lillooet river provides an opportunity to study the effects of natural and artificial channel changes that have occurred over the past century we analyze the long term effects of channel alterations that may affect flood hazard in the mid 1940s several meanders were artificially severed side channels blocked off and the level of downstream lillooet lake was lowered these measures were thought to increase hydrologic efficiency and decrease flood risk in the largely agricultural valley between 1947 and 1994 average channel width in the upper reaches decreased by 50 most of which occurred by the late 1950s between 1945 and 1969 lillooet river degraded its bed elevation by 3 4 m 12 5 to 16 7 cm a 1 in the upper reaches and up to 2 m 8 3 cm a 1 in the lower reaches this sudden and profound degradation compares to average bed elevation increases of 2 4 cm a 1 prior to the engineering works between 1969 and 1985 the cross section area increased by 22 in the upper reaches and 13 in the lower reaches and decreased to 12 and 8 respectively for the time period 1985 to 2000 the increased sediment supply that was caused by channel straightening accelerated delta advance in lillooet lake from 7 m a 1 1858 to 1948 to 30 m a 1 for the five year period following the 1948 channel works these rates have decreased over time but with a current advance rate of 10 5 m a 1 1986 2009 are still above the long term average prior to the channel changes this study demonstrates the time scale direction and magnitude of channel changes following significant artificial river alterations while the initial goal of decreasing flood risk had been achieved in the short term the lower river apparently is slowly returning to an overall aggradational phase ongoing delta advance will ultimately increase channel elevations in the lower reaches and lead to significant flood hazards for populated areas

widespread initiation reactivation and acceleration of landslides in the northern california coast ranges due to extreme rainfall episodically to continuously active slow moving landslides are driven by precipitation climate change which is altering both the frequency and magnitude of precipitation worldwide is therefore predicted to have a major impact on landslides here we examine the behavior of hundreds of slow moving landslides in northern california in response to large changes in annual precipitation that occurred between 2016 and 2018 we quantify the landslide displacement using repeat pass radar interferometry and pixel offset tracking techniques on a novel data set from the airborne nasa jpl uninhabited aerial vehicle synthetic aperture radar we found that 312 landslides were moving due to extreme rainfall during 2017 compared to 119 during 2016 which was the final year of a historic multiyear drought however with a return to below to average rainfall in 2018 only 146 landslides remained in motion the increased number of landslides during 2017 was primarily accommodated by landslides that were smaller than the landslides that remained active between 2016 and 2018 furthermore by examining a subset of 51 landslides we found that 49 had increased velocities during 2017 when compared to 2016 our results show that slow moving landslides are sensitive to large changes in annual precipitation particularly the smaller and thinner landslides that likely experience larger basal pore water pressure changes based on climate model predictions for the next century in california which include increases in average annual precipitation and increases in the frequency of dry to wet extremes we hypothesize that there will be an overall increase in landslide activity

is climate change responsible for changing landslide activity in high mountains climate change manifested by an increase in mean minimum and maximum temperatures and by more intense rainstorms is becoming more evident in many regions an important consequence of these changes may be an increase in landslides in high mountains more research however is necessary to detect changes in landslide magnitude and frequency related to contemporary climate particularly in alpine regions hosting glaciers permafrost and snow these regions not only are sensitive to changes in both temperature and precipitation but are also areas in which landslides are ubiquitous even under a stable climate we analyze a series of catastrophic slope failures that occurred in the mountains of europe the americas and the caucasus since the end of the 1990s we distinguish between rock and ice avalanches debris flows from de glaciated areas and landslides that involve dynamic interactions with glacial and river processes analysis of these events indicates several important controls on slope stability in high mountains including the non linear response of firn and ice to warming three dimensional warming of subsurface bedrock and its relation to site geology de glaciation accompanied by exposure of new sediment and combined short term effects of precipitation and temperature based on several case studies we propose that the following mechanisms can significantly alter landslide magnitude and frequency and thus hazard under warming conditions 1 positive feedbacks acting on mass movement processes that after an initial climatic stimulus may evolve independently of climate change 2 threshold behavior and tipping points in geomorphic systems 3 storage of sediment and ice involving important lag time effects

energy flux model of seismic coda separation of scattering and intrinsic attenuation a new model of seismic coda is presented based on the balance between the energy scattered from the direct wave and the energy in the seismic coda this energy flux model results in a simple formula for the amplitude and time decay of the seismic coda that explicitly differentiates between the scattering and intrinsic anelastic attenuation of the medium this formula is valid for both weak and strong scattering and implicitly includes multiple scattering the model is tested using synthetic seismograms produced in finite difference simulations of wave propagation through media with random spatial variations in seismic velocity some of the simulations also included intrinsic dissipation the energy flux model explains the coda decay and amplitude observed in the synthetics for random media with a wide range of scattering q in contrast the single scattering model commonly used in the analysis of microearthquake coda does not account for the gradual coda decay observed in the simulations for media with moderate or strong scattering attenuation scattering q less than or equal to 150 the simulations demonstrate that large differences in scattering attenuation cause only small changes in the coda decay rate as predicted by the energy flux model the coda decay rate is sensitive however more to the intrinsic q of the medium the ratio of the coda amplitude to the energy in the direct arrival is a measure of the scattering attenuation thus analysis of the decay rate and amplitude of the coda can in principle produce separate estimates for the scattering and intrinsic q values of the crust we analyze the coda from two earthquakes near anza california intrinsic q values determined from these seismograms using the energy flux model are comparable to coda q values found from the single scattering theory the results demonstrate that coda q values are at best measures of the intrinsic attenuation of the lithosphere and are unrelated to the scatteing q less

a scattering model to explain seismic q observations in the lithosphere between 1 and 30 hz observations of lithospheric q for shear waves in the range 1 30 hz reported in the literature are examined using a scattering model consisting of randomly distributed spheres for the single scattering approximation i have assumed 1 q 1 q sub i gv omega where q sub i is the intrinsic q due to anelasticity v is the velocity of shear waves omega is angular frequency and g is the turbidity g is taken as a constant in this paper since g integral n a sigmada where n a da is the number of scattering spheres of radius a unit volume and sigma is the scattering cross section for a sphere this suggests that geometrical scattering dominates this will be true for ka 1 where k is wavenumber based on this criterion and the observation that q is large i e g small at a frequency of 0 05 hz a is of the order of magnitude 1 10 km fits of observations of shear wave q from japan and central asia indicate that q sub i 2000 500 for the lithosphere of both regions g 0 01 km for the japan observations and g 0 005 km sup 1 for central asia

multiple late holocene earthquakes along the reelfoot fault central new madrid seismic zone the reelfoot fault is an east vergent reverse fault underlying the lake county uplift a low amplitude late holocene anticline bordered on the east by the 32 km long reelfoot scarp fluvial deposits across the scarp define an 8 m high east facing monocline most near surface deformation along the scarp is accommodated via folding rather than faulting we interpret the scarp as a fault propagation fold developed over a wcst dipping reverse fault interpreted from shallow seismic reflection data trench exposurcs provide evidence for three episodes of deformation along the reelfoot fault within thc past approximately 2400 years between a d 780 and 1000 between a d 1260 and 1650 and during a d 1812 our best estimate of the average recurrence interval for deformation along the scarp is 400 500 years each episode of deformation had a slightly different style the third most recent event produced a small graben a few tens of centimeters deep in the hanging wall of the reverse fault the second most recent earthquake produced about 1 3 m of throw in the graben as well as folding along the updip projection of the reverse fault and development of the scarp thesc relations suggest that graben development increased through time concomitant with growth of the monocline or that the events are of different magnitude the 1811 1812 episode of deformation produced abundant liquefaction prominent folding of fluvial strata along the scarp and minor faulting in the graben

broadband microtremor observation of basin resonance in the mississippi embayment central us we report systematic variations in the fundamental period of seismic site resonance within the mississippi embayment the resonance periods are revealed by peaks in horizontal to vertical h v spectral ratios of microtremor measurements and increase with the depth to the sediment basement interface the sediment depth varies slowly enough spatially that at any site it can be modeled as a one dimensional problem revealing structural details of the sedimentary column the strong impedance contrast and gentle dip of the base of the embayment sediments may trap seismic energy within the soft sediments increasing durations and amplitudes of strong ground motions broadband recordings of microtremor within the mississippi embayment provide a simple method to study the seismic response of the basin

non linear one dimensional seismic ground motion propagation in the mississippi embayment abstract deep unconsolidated deposits of the mississippi embayment overlie the new madrid seismic zone considered the most seismically active zone in the eastern us the deposits range in thickness from less than 100 m in the st louis area to about 1 km in the memphis area and consist of silts clays and sands the influence of these deposits on propagation of seismic waves remains a major source of uncertainty for site response analysis this paper describes the development of a new non linear one dimensional site response analysis model for vertical propagation of horizontal shear waves in deep soil deposits soil response is modeled using a modified hyperbolic model with extended masing criteria to represent hysteretic loading and unloading of soil the new soil model accounts for the influence of large confining pressures on strain dependent modulus degradation and damping of soil the model is calibrated using measured shear modulus degradation and damping data from resonant column tests on sand samples under confining pressures up to 3 5 mpa the new model is used to estimate ground motion amplification and attenuation for three soil columns 100 500 and 1000 m thick representative of soil thickness variability within the embayment the new model shows that some high frequency components of ground motion are transmitted through these deep deposits these components are usually filtered out using conventional wave propagation methods longer period waves develop in deposits of 500 1000 m thickness spectral amplification factors of deep deposits are greater than unity and can be as large as 5 in the longer period range of 2 10 s preliminary evaluation of model results show that computed surface response spectra in the period range of 0 5 2 s are larger than the 1997 nehrp recommended design response spectrum the proposed model highlights the need to account for depth dependence of modulus and damping properties of soils in seismic wave propagation through deep soils

seismic ground motions from a bolide shock wave 1 an intensely brilliant bolide accompanied by an audible sonic boom occurred on the night of 3 november 2003 2150 lt or 4 november 2003 0350 ut in northeastern arkansas the sonic boom was well recorded by 22 three component stations of the center for earthquake research and information cooperative seismic network arrival times and wave polarizations were used to reconstruct the acoustic wave front propagating across the network and to estimate trajectory parameters of the bolide a grid search location technique constrains the trajectory and gives a reference height of 50 100 km above the southern edge of the network an azimuth of propagation of 270 290 toward the northwest and a plunge of 38 48 downward the trajectory and date of the bolide event are consistent with a taurid shower meteor transient ground motions from the sonic boom were studied using plane wave cagniard dehoop and propagator matrix theory for an incident pressure pulse impinging on a layered elastic earth model general characteristics of the vertical and radial polarization and wave frequency content require acoustic coupling within a thin 10 m near surface layer with low p wave 0 25 km s and s wave 0 125 km s velocities ground motions are generally confined to this near surface layer are not sensitive to deeper earth structure within the mississippi embayment unconsolidated sediments and display both leaky mode pl a type of dispersed p type seismic wave and locked mode rayleigh wave propagation acoustic wave ground motion coupling studies may be a useful way to analyze near surface site responses to determine velocity structure in earthquake shaking hazard studies