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

spatial distribution of landslides triggered by the 2008 ms 8 0 wenchuan earthquake china abstract the ms 8 0 wenchuan earthquake of may 12 2008 is one of the most disastrous earthquakes in china the earthquake triggered tens of thousands of landslides over a broad area including shallow disrupted landslides rock falls deep seated landslides and rock avalanches some of which buried large sections of some towns and dammed the rivers the purpose of this study is to investigate correlations between the occurrence of landslides with geologic and geomorphologic conditions and seismic parameters over 56 000 earthquake triggered landslides with a total area of 811 km 2 are interpreted using aerial photographs and remote sensing images taken following the earthquake the spatial distribution of these landslides is analyzed statistically using both landslide point density lpd defined as the number of landslides per square kilometer and landslide area density lad the percentage of the area affected by landslides to determine how the occurrence of landslides correlates with distance from the epicenter distance from the major surface rupture seismic intensity and peak ground acceleration pga slope angle slope aspect elevation and lithology it is found that both lad and lpd have strong positive correlations with slope steepness distance from the major surface rupture and seismic intensity and that pre sinian schist and cambrian sandstone and siltstone intercalated with slate have the most concentrated landslide activities followed by the permian limestone intercalated with shale and devonian limestone statistical analyses also indicate that the major surface rupture has influence on the spatial distribution of landslides because lad and lpd are relatively higher on the hanging wall than on the footwall however the correlation between the occurrence of landslides with distance from the epicenter of the earthquake is complicated rather than a relatively simple negative correlation as found from other reported cases of earthquakes this is possibly due to complicated rupture processes of the earthquake

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

distribution pattern of earthquake induced landslides triggered by the 12 may 2008 wenchuan earthquake abstract this paper presents the preliminary results of an extensive study of the mapping the distribution of landslides triggered by the wenchuan earthquake in sichuan province china on 12 may 2008 an extensive landslide interpretation was carried out using a large set of optical high resolution satellite images e g aster alos cartosat 1 spot 5 and ikonos as well as air photos for both the pre and post earthquake situation landslide scarps were mapped as points using multi temporal visual image interpretation taking into account shape tone texture pattern elevation and ridge and valley orientation nearly 60 000 individual landslide scarps were mapped the landslide distribution map was compared with the inventory map that was prepared directly after the earthquake which contains about 11 000 individual landslide points through the calculation of normalized landslide isopleths maps remarkable differences were observed as the earlier inventory mapping did not consider the pre earthquake situation and did not consider all individual landslides as part of the landslide inventory landslides were identified that had blocked the drainage and had formed landslide dams the landslide distribution was compared with a number of aspects such as the seismic parameters distance to epicenter distance to fault rupture co seismic fault geometry and co seismic slip distribution and geology the most remarkable correlation found was with the co seismic slip distribution and the fault geometry landslide distribution in the section of the fault that had mainly a thrust component with low angle fault plane was found to be much higher than the sections that had steeper fault angles and a major strike slip component

silicified conifer forests and potential mining problems in seam m2 of the gore lignite measures miocene southland new zealand abstract silicified conifer podocarpus cf hallii stumps up to 0 8 m in diameter are present at two levels in seam m2 of the miocene gore lignite measures mataura coalfield eastern southland the in situ stumps are believed to be the remains of forests which grew during pauses in peat accumulation when groundwater levels were depressed as a result of climatic change or local basinal processes growth ring measurements show the trees increased in radius between 0 16 and 1 mm per year in two of six specimens the growth rates halved during their final 30 40 years of life rising water levels may have resulted in less favourable growth conditions within the stumps much of the wood structure is well preserved progressive diagenesis involved impregnation of the cell walls by silica infilling of the cell lumens with length slow chalcedony and opaline silica and deposition of opal length fast chalcedony and minor siderite in fractures radial and axial parenchyma contain coalified organic material and minor chalcedony filaments of wood rotting fungi and probable root masses of epiphytes are present in some fossil wood however by analogy with modern podocarpus hallii we maintain the stumps were preserved for later silicification because the wood was highly resistant to fungal and bacterial decay the stumps presumably functioned as conduits to ascending silica saturated meteoric groundwater and water released during compaction because of the contrasts in permeability between the vertical stumps and the surrounding peat

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

discriminant analysis of the geomorphic characteristics and stability of landslide dams article i nfo landslides can cause the formation of dams but these dams often fail soon after lake formation thus rapidly evaluating the stability of a landslide dam is crucial for effective hazard mitigation this study utilizes discriminant analysis based on a japanese dataset consisting of 43 well documented landslide dams to determine the significant variables including log transformed peak flow or catchment area and log transformed dam height width and length in hierarchical order which affect the stability of a landslide dam the high overall prediction power 88 4 of the 43 training cases are correctly classified and the high cross validation accuracy 86 demonstrate the robustness of the proposed discriminant models phwl with variables including log transformed peak flow and log transformed dam height width and length and ahwl with variables including log transformed catchment area and log transformed dam height width and length compared to a previously proposed dbi index based graphic approach the discriminant model ahv which uses the log transformed catchment area dam height and dam volume as relevant variables shows better ability to evaluate the stability of landslide dams although these discriminant models are established using a japanese dataset only the present multivariate statistical approach can be applied for an expanded dataset without any difficulty when more completely documented worldwide landslide dam data are available

coal petrological and xylotomical characterization of miocene lignites and in situ fossil tree stumps and trunks from lusatia region germany palaeoenvironment and taphonomy assessment abstract the present paper investigates rank and composition of coal as well as depositional and hydrogeological settings persisting during the stage of peat accumulation and evaluates taphonomy and conditions for the in situ preservation of outstanding fossilized stump and trunks using coal petrological and xylotomical analyses the obtained results are further interpreted and compared with existing literature records lignite samples and fossil wood specimens were collected from the 2nd mfh 2nd miocene seam horizon or its equivalent present at meuro piskowitz and welzow sud open cast mines located in lusatia germany the examined lignite samples indicate low rank coals at lignite or subbituminous rank stage and are characterised by slight dominance of attrinite over textinite ulminite suberinite cutinite porigelinite resinite and corpohuminite macerals waterlogged conditions prevailing in the mire are associated with peat accumulation under anoxic conditions accompanied by low decomposition rates the determined facies indicators suggest a moderate to high as well as low gelification of the organic matter for the meuro and piskowitz open cast mines respectively in meuro open cast mine the prevalence of herbaceous plant in a mire or a bacterial fungal degradation of woody plant tissues can be envisaged whereas in the piskowitz open cast mine it is suggested that peat formed in a wet forest mire environment with a limited oxygen supply and a relatively low bacterial fungal degradation the studied fossil wood specimens revealed the presence of quasisequoioxylon piskowitzense preserved as an in situ fossilized stump as well as taxodioxylon cryptomerioides and sciadopityoxylon wettsteinii species preserved as fossilized trunks the examined species belong to the families of cupressacea sciadopityaceae and cupressaceae li sensu lato the taphonomy of the in situ fossilized stump and trunks can be explained by nutrient and oxygen poor oligotrophic mires distinguished as raised bogs and suggesting generally anoxic conditions during middle to late miocene climate transition

landslides triggered by the 8 october 2005 kashmir earthquake abstract the 8 october 2005 kashmir earthquake triggered several thousand landslides these were mainly rock falls and debris falls although translational rock and debris slides also occurred in addition a sturzstrom debris avalanche comprising 80 million m3 buried four villages and blocked streams to create two lakes although landsliding occurred throughout the region covering an area of 7500 km2 the failures were highly concentrated associated with six geomorphic geologic anthropogenic settings including natural failures in 1 highly fractured carbonate rocks comprising the lowest beds in the hanging wall of the likely earthquake fault 2 tertiary siliciclastic rocks along antecedent drainages that traverse the hazara kashmir syntaxis 3 steep 50 slopes comprising precambrian and lower paleozoic rocks 4 very steep 50 lower slopes of fluvially undercut quaternary valley fills and 5 ridges and spur crests the sixth setting was associated with road construction extensive fissuring in many of the valley slopes together with the freshly mobilized landslide debris constitutes a potential hazard in the coming snowmelt and monsoon seasons this study supports the view that earthquake triggered landslides are highly concentrated in specific zones associated with the lithology structure geomorphology topography and human presence

statistical approach to earthquake induced landslide susceptibility susceptibility analysis for predicting earthquake induced landslides has most frequently been done using deterministic methods multivariate statistical methods have not previously been applied in this study however we introduce a statistical methodology that uses the intensity of earthquake shaking as a landslide triggering factor this methodology is applied in a study of shallow earthquake induced landslides in central western taiwan the results show that we can accurately interpret landslide distribution in the study area and predict the occurrence of landslides in neighboring regions this susceptibility model is capable of predicting shallow landslides induced during an earthquake scenario with similar range of ground shaking without requiring the use of geotechnical groundwater or failure depth data

the maximum discharge of outburst floods caused by the breaching of man made and natural dams the sudden release of water impounded in natural and man made reservoirs has been responsible for some major disasters in mountainous regions of the world recent natural damming events and failures of natural dams have illustrated the need to examine the nature and magnitude of outburst floods and the behaviour of debris dams in general an empirical relationship between maximum discharge qmax and volume of water released during the outburst event vmax is established qmax 0 72vmax0 53 for man made dams and the relationship is thought applicable to the breaching of natural debris dams landslides and moraines this relationship allows a first order estimate to be made of qmax in the vicinity of the breach for a given vmax during the failure of a man made dam or a natural debris dam key words outburst floods man made dams natural dams landslide dam failure

the characteristics of the landslides triggered by the wenchuan ms 8 0 earthquake from anxian to beichuan abstract this paper presents a quantitative analysis of the number and area of the landslides triggered by the wenchuan ms 8 0 earthquake from anxian to beichuan in this study the controlling factors of landslides are obtained from geological maps relief amplitude slope and topographic roughness calculated from dem data in arcgis 9 2 a total of 4134 landslides are identified from digital aero image of 1 m resolution covering 19 7 km2 that accounts for 6 4 of the study area the number of landslides with areas less than 5000 m2 is up to 85 22 the smallest landslide is 6 m2 and the largest 1515 000 m2 the number of landslides which have occurred is 1 6 times more prevalent at hanging walls as opposed to foot walls also the relationship between the numbers of landslides and the distances to an earthquake rupture at a hanging wall is linear but exponential at a footwall these results prove that landslide activity is more severe at hanging walls than at foot walls the outcrop area of geologic unit is proportional to the number of landslides except the jurassic triassic and quaternary units r2 0 952 in the study area and landslide density is 19 meanwhile the area of a landslide is linearly proportional to outcrop area of geologic unit except jurassic lower cambrian and quaternary unit r2 0 8279 in the study area and appear to indicate that the lithology does not play an important role in landslides in the study area earthquake triggered landslides tend to be concentrated in specific zones associated with the event controlling parameters such as reliefs slopes and topographic roughness the landslides occurred particularly in the range of 600 1293 m relief amplitudes and the number in this range amounts to 90 of total slides in the studied region moreover landslides easily occurred in the curvature 1 15 with slope between 5 and 55 in addition landslides also usually occurred in the range of 1 1 5 topographic roughness therefore these correlations provide a way to assess regional landslide hazards and are of great significance to regional geohazard planning and prediction

controls on the channel width of rivers implications for modeling fluvial incision of bedrock on the basis of the manning equation and basic mass conser vation principles we derive an expression for scaling the steady state width w of river channels as a function of discharge q channel slope s roughness n and width to depth ratio a w 5 a a1 2 2 3 3 8 q 3 8 s 23 16 n 3 8 we propose that channel width to depth ratio in addition to roughness is a function of the material in which the channel is developed and that where a river is con fined to a given material width to depth ratio and roughness can be assumed constant given these simplifications the expression emulates traditional width discharge relationships for rivers incis ing bedrock with uniformly concave fluvial long profiles more sig nificantly this relationship describes river width trends in terrain with spatially nonuniform rock uplift rates where conventional discharge based width scaling laws are inadequate we suggest that much of observed channel width variability in river channels confined by bedrock is a simple consequence of the tendency for water to flow faster in steeper reaches and therefore occupy smaller channel cross sections we demonstrate that using conventional scaling relationships for channel width can result in underestima tion of stream power variability in channels incising bedrock and that our model improves estimates of spatial patterns of bedrock incision rates

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

bedrock channel adjustment to tectonic forcing implications for predicting river incision rates we present detailed data of channel morphology for a river undergoing a transient response to active normal faulting where excellent constraints exist on spatial and temporal variations in fault slip rates we show that traditional hydraulic scaling laws break down in this situation and that channel widths become decoupled from drainage area upstream of the fault unit stream powers are 4 times higher than those predicted by current scaling paradigms and imply that incision rates for rivers responding to active tectonics may be significantly higher than those heretofore modeled the loss of hydraulic scaling cannot be explained by increasing channel roughness and is an intrinsic response to tectonic forcing we show that channel aspect ratio is a strongly nonlinear function of local slope and demonstrate that fault induced adjustment of channel geometries has reset hillslope gradients the results give new insight into how rivers maintain their course in the face of tectonic uplift and illustrate the first order control the fluvial system exerts on the locus and magnitude of sediment supply to basins

distribution of active rock uplift along the eastern margin of the tibetan plateau inferences from bedrock channel longitudinal profiles 1 current models of long term river incision into bedrock suggest that the local rate of differential rock uplift should exert a primary control on the gradient of channel longitudinal profiles however discrimination of this effect from the influence of variations in substrate erodibility sediment flux precipitation and transient changes in profile shape has proved difficult in practice here we investigate the controls on the spatial distribution of bedrock channel gradients adjacent to the sichuan basin in an effort to assess the degree and nature of active deformation along this margin of the tibetan plateau analysis of river longitudinal profiles utilizing a channel steepness index a measure of profile gradient normalized for drainage area reveals a zone of anomalously steep channels adjacent to the topographic front of the plateau margin channel profiles are systematically less steep in their headwater reaches on the plateau and in their lower reaches east of the plateau margin comparison of steepness indices to mapped lithologic variations reveals that lithology has only a limited influence on channel gradient in this field area we observe no systematic relationship between steepness indices and upstream drainage area channels of all size are steeper near the plateau margin we argue that these systematic changes are not readily explained as a consequence of increased sediment flux or of orographic precipitation we are led to conclude that steep channel profiles along the topographic front of the plateau reflect active differential rock uplift between this region and the foreland

topographic development of the southern alps recorded by the isotopic composition of authigenic clay minerals south island new zealand abstract the southern alps are developing as a consequence of oblique collision between the pacific and australian plates the southern alps lie on the west side of the south island of new zealand and create a massive rain shadow where greater than 12 m year of rain falls on the west coast and semiarid conditions exist to the east the rain out effect across the mountains causes precipitation west of the southern alps to have d and 18 o values averaging 30 and 5 5 whereas precipitation in the rain shadow to the east is isotopically lighter d 72 and 18 o 9 8 such large differences in the isotopic composition of precipitation would not have existed prior to the development of significant topography we have examined the topographic evolution of the southern alps using oxygen isotope analyses of authigenic kaolinites formed in the rain shadow to the east of the mountains between the cretaceous low topography and the pleistocene changes in the isotopic composition of authigenic clay minerals forming in equilibrium with meteoric water in the stratigraphic sequence record the development of southern alps topography and the resultant rain shadow our oxygen isotope analyses of authigenic kaolinites show a 5 6 decrease in the early pliocene from 18 2 in older rocks to 12 3 in younger rocks in addition smectite is abundant in all samples from the late miocene to recent but is conspicuously absent in most older rocks suggesting a change to a generally drier climate roughly coincident with the isotopic shift in kaolinites this method may be useful in unraveling timing of development of mountain belts elsewhere in the world

evaluation of factors controlling earthquake induced landslides caused by chi chi earthquake and comparison with the northridge and loma prieta events over 10 000 landslides were triggered by the september 21 1999 chi chi earthquake a large number of these landslides have been mapped from spot images and a smaller number were described in a detailed field investigation geographic information systems gis was used to conduct a spatial characterization of the slope failures including distribution of type size slope angle bedrock geology ground motion and distance from earthquake source the most abundant landslides were shallow disaggregated rock and soil slides landslides occurred primarily in tertiary sedimentary rocks which are well known for their susceptibility to landsliding in many parts of the world landslide concentration values diminish beyond epicentral distances of 40 and 70 km from the epicenter and the surface projection of the fault plane respectively ground motion was found to be the most significant factor in triggering the shallow landslides in the chi chi earthquake overall 74 of all slope failures occurred in regions with vertical ground motions greater than 0 2g and 81 of all slope failures occurred in the region with mean horizontal peak ground accelerations pga greater than 0 15g these factors were used to compare landslides generated by the chi chi earthquake to the landslides triggered by the 1989 loma prieta earthquake and the 1994 northridge earthquake the major difference in distribution of landslides between the chi chi earthquake and the two california earthquakes was the distribution of slope angles in the chi chi earthquake 90 of the failures occurred on slopes steeper than 45 while more than 80 of failures occurred on slopes less than 50 in california apparently reflecting much steeper and tectonically more active geologic setting in taiwan

fossil wood from the middle cretaceous moreno hill formation unique expressions of wood mineralization and implications for the processes of wood preservation abstract the cretaceous turonian moreno hill formation of west central new mexico provides an opportune isotaphonomic setting to study wood preservation because both carbonized and mineralized wood are commonly found within the same sediments and often within individual specimens petrographic reflectance maceral and chemical analyses were used to compare and characterize mineralized and carbonized wood from the study site to investigate biases which influence mode of preservation coal in the form of coal inclusions is the most common form of fossil wood and mineralized wood is also widespread in the formation two striking specimens of in situ coalified stumps are particularly informative because each includes a mineralized ring that appears to represent the former location of sapwood most of the mineralized samples are primarily composed of quartz but a few specimens are predominantly mineralized with apatite calcite is present in charcoal samples where it permineralized but never replaced organic carbon this study points to two key factors that influence mineralization wood permeability and the chemical alteration of the wood prior to incorporation into the sediment the patterns of mineralization are consistent with hypothesized microbial involvement in the mineralization process the coexistence of coal and mineralized tissues in some samples suggests that the processes of silicification and phosphatization co occurred with coalification and that these processes are competitive within individual pieces of wood as such various stages of wood degradation have been preserved in mineralized samples from the moreno hill formation the study suggests that coal inclusions and mineralized wood coal associations may also be common in other ancient sediments even though weathering may obscure their presence such information is important for paleoecological and paleoenvironmental studies which utilize the occurrence of fossil wood to help reconstruct floral composition or climatic conditions

slip maxima at fault junctions and rupturing of barriers during the 2008 wenchuan earthquake the devastating wenchuan earthquake in 2008 struck along a fault zone that showed low rates of deformation analysis of gps and insar data suggests that as structural barriers failed during a single earthquake the rupture cascaded across multiple fault segments which may explain the high magnitude of the event

burial of trees by eruptions of mount st helens washington implications for the interpretation of fossil forests lahars and fluvial sediments which buried trees following the 18 may 1980 eruption of mount st helens were investigated during august of 1982 trees buried in older mudflows dated at a d 1885 a d 1450 1550 and 36000 years b p also were examined although many logs clearly were transported large numbers of trees were buried in growth position burial by lahars generally resulted in the death of trees whereas some trees survived burial by fluvial sediments scanning electron microscope studies show that trees buried in lahars are well preserved pre 1885 buried woods show incipient silicification and woods buried 36000 years b p show silica impregnation of cell walls features of in situ and allochthonous burial very similar to those seen in southern washington are found also in eocene silicified forests in yellowstone national park wyoming u s a and in cretaceous fossil forests in southeastern alexander island antarctica observations of recent wood from volcaniclastic deposits of mount st helens provide valuable insights into processes of burial and silicification of fossil forests of various ages around the world

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

co seismic thrusting rupture and slip distribution produced by the 2008 mw 7 9 wenchuan earthquake china field investigations reveal that the mw 7 9 wenchuan china earthquake of 12 may 2008 produced a 285 km long surface rupture zone with dominantly thrusting slip accompanied by a right lateral component along the central northern segments of the zone and left lateral component along the southern segment along the longmen shan thrust belt eastern margin of the tibetan plateau the co seismic ruptures mainly occurred along the pre existing yingxiu beichuan guanxian anxian and qingchuan faults which are the main faults of the longmen shan thrust belt the displacements measured in the field are approximately 0 5 6 5 m in the vertical typically 1 3 m accompanied by an average left lateral component of 2 m along the 50 km long southernmost segment of the rupture zone and an average right lateral component of 1 m along the 150 km long central northern segments the maximum thrust slip amount is estimated to be 10 m accompanied by 9 m of shortening across the rupture zone this finding is consistent with estimates based on seismic data the rupture length and maximum vertical displacement are the largest among all intracontinental thrust type earthquakes reported to date our findings demonstrate that i the wenchuan earthquake occurred upon pre existing active faults of the longmen shan thrust belt thereby controlling the spatial distribution of co seismic surface rupture and displacement and the rupture processes of the earthquake ii the long rupture length and large thrusting slip resulted from compressive stress associated with eastward extrusion of the tibet plateau as it accommodates the ongoing penetration of the indian plate into the eurasian plate and iii present day shortening strain upon the eastern margin of the tibetan plateau is mostly released by seismic slip along thrust faults within the longmen shan thrust belt

earthquake dammed lakes in new zealand eleven small lakes were formed by landslides caused by the 1929 buller earthquake four others were formed by other historic earthquakes in new zealand at least nine other new zealand lakes are also dammed by landslides and were probably formed by prehistoric earthquakes when recognized by morphology synchronous age and areal distribution earthquake dammed lakes could provide an estimate of paleoseismicity for the past few hundred or thousand years

coseismic reverse and oblique slip surface faulting generated by the 2008 mw 7 9 wenchuan earthquake china the mw 7 9 wenchuan china earthquake ruptured two large thrust faults along the long menshan thrust belt at the eastern margin of the tibetan plateau this earthquake generated a 240 km long surface rupture zone along the beichuan fault and an additional 72 km long surface rupture zone along the pengguan fault maximum vertical and horizontal offsets of 6 5 m and 4 9 m respectively were measured along the beichuan fault a maximum vertical offset of 3 5 m was measured along the pengguan fault coseismic surface ruptures integrated with aftershocks and industry seismic profiles show that two imbricate structures have ruptured simultaneously resulting in the largest continental thrust event ever documented large oblique thrusting observed during this earthquake indicates that crustal shortening is an important process responsible for the high topography in the region as everywhere along the edge of tibetan plateau

variable source depth acquisition for improved marine broadband seismic data in marine seismic data acquisition varying the source depth along a sail line gives diversity in sequential shot gather frequency spectra undesired alterations of the frequency spectra are created by the source ghost and by air gun bubble oscillations by deliberately varying the source depth along a sail line it is possible to obtain a seismic data set that will have energy more evenly distributed within the main frequency band of the source output this is obtained when data acquired with different source depths are stacked in imaging we formulated a simple inverse problem that seeks to find the optimal distribution of source depths over a sequential series of shots that shape the amplitude spectrum of the final image into a desired shape we assumed that the data are receiver side deghosted that designature could be applied to each shot gather and that the shot gathers could be redatumed to a common datum prior to imaging

a method for producing digital probabilistic seismic landslide hazard maps abstract the 1994 northridge california earthquake is the first earthquake for which we have all of the data sets needed to conduct a rigorous regional analysis of seismic slope instability these data sets include 1 a comprehensive inventory of triggered landslides 2 about 200 strong motion records of the mainshock 3 1 24 000 scale geologic mapping of the region 4 extensive data on engineering properties of geologic units and 5 high resolution digital elevation models of the topography all of these data sets have been digitized and rasterized at 10 m grid spacing using arc info gis software on a unix computer combining these data sets in a dynamic model based on newmark s permanent deformation sliding block analysis yields estimates of coseismic landslide displacement in each grid cell from the northridge earthquake the modeled displacements are then compared with the digital inventory of landslides triggered by the northridge earthquake to construct a probability curve relating predicted displacement to probability of failure this probability function can be applied to predict and map the spatial variability in failure probability in any ground shaking conditions of interest we anticipate that this mapping procedure will be used to construct seismic landslide hazard maps that will assist in emergency preparedness planning and in making rational decisions regarding development and construction in areas susceptible to seismic slope failure

landslides induced by the 2008 wenchuan earthquake sichuan china the 2008 wenchuan earthquake with a magnitude of mw 7 9 induced numerous slope movements on the hanging walls of fault surface ruptures and on steep inner valleys along the minjiang river landslide moving directions showed preferred orientations normal to the fault ruptures indicating the effect of the directivity of the seismic wave the most common landslides were of carbonate rocks which are easily dissolved and decrease the contact surfaces the largest non volcanic landslide in history was induced in bedded dolomite by the earthquake and was preceded by gravitational deformation with ridge top depressions valley fill materials were mobilized at 36 locations probably by pore water pressure build up

petrifaction of wood by silica minerals abstract seventy five woods of australian origin have been examined by means of x ray diffraction optical and scanning electron microscopy and differential thermal analysis the silica is in one or other of the following forms opal a opal ct chalcedony quartz quartz chalcedony opal chalcedony more than half of them consist of opal ct or chalcedony the results indicate that petrifaction by silica involves penetration of the wood via splits or checks permeation of cell walls via a reticulated system of micropores enlargement of the micropore system as cell wall components break down and continuing deposition of silica ata rate and in a manner consistent with maintaining the dimensional stability of the wood deposition of silica in cell lumina and intercellular voids may be sometimes but not always a separate and later event the final stages of lithification involve loss of water and perhaps transformation of one form of silica into another

gis based landslide susceptibility mapping for the 2005 kashmir earthquake region abstract the m w 7 6 october 8 2005 kashmir earthquake triggered several thousand landslides throughout the himalaya of northern pakistan and india these were concentrated in six different geomorphic geologic anthropogenic settings a spatial database which included 2252 landslides was developed and analyzed using aster satellite imagery and geographical information system gis technology a multi criterion evaluation was applied to determine the significance of event controlling parameters in triggering the landslides the parameters included lithology faults slope gradient slope aspect elevation land cover rivers and roads the results showed four classes of landslide susceptibility furthermore they indicated that lithology had the strongest influence on landsliding particularly when the rock is highly fractured such as in shale slate clastic sediments and limestone and dolomite moreover the proximity of the landslides to faults rivers and roads was also an important factor in helping to initiate failures in addition landslides occurred particularly in moderate elevations on south facing slopes shrub land grassland and also agricultural land were highly susceptible to failures while forested slopes had few landslides one third of the study area was highly or very highly susceptible to future landsliding and requires immediate mitigation action the rest of the region had a low or moderate susceptibility to landsliding and remains relatively stable this study supports the view that 1 earthquake triggered landslides are concentrated in specific zones associated with event controlling parameters and 2 in the western himalaya deforestation and road construction contributed significantly to landsliding during and shortly after earthquakes

diagenetic quartz and amorphous silica in new zealand coals new zealand coal seams late cretaceous miocene lignite semi anthracite contain numerous and varied occurrences of diagenetic quartz and amorphous silica early diagenetic silicifications include sub horizontal and laterally extensive quartz mineralized bands micro and megascopic euhedral quartz crystals dispersed or concentrated in layers and silicified in situ tree stumps late diagenetic forms include sub horizontal quartz mineralized bands mostly 1 m in length and fracture infillings the origins of the silica remain uncertain but leached basement rocks and coal measure sediments and siliceous phytoliths within the coal forming plants are possible sources the silicification of coal seams may have significant implications for exploration mining and geological studies

coseismic surface ruptures and crustal deformations of the 2008 wenchuan earthquake mw7 9 china 1 the irregularly distributed surface fault ruptures of the wenchuan earthquake spanned over 200 km along the longmen shan lms fault zone through field investigations we found over 10 coseismic surface ruptures with maximum vertical displacements of approximately 6 m on the yingxiu beichuan fault and 2 m on the guanxian anxian fault however the entire fault rupture movement was still not clearly understood since high topographic areas were inaccessible thus we used interferometric synthetic aperture radar insar satellite observations to capture whole coseismic surface ruptures and crustal deformations across the lms faults we created a novel bi fault slip model to invert fault slips using insar information which yielded that thrust fault slips were dominant at yingxiu houshenggou and bajiaomiao in the near epicenter segment while the dextral fault slips were dominant at pingtong and nanba along the northeast segment the combination of field investigations and simulations suggested that the two coseismic fault zones ruptured with an irregular surface distribution accompanied by crustal deformations

methods for predicting peak discharge of floods caused by failure of natural and constructed earthen dams floods from failures of natural and constructed dams constitute a widespread hazard to people and property expeditious means of assessing flood hazards are necessary particularly in the case of natural dams which may form suddenly and unexpectedly we revise statistical relations derived from data for past constructed and natural dam failures between peak discharge qp and water volume released v0 or drop in lake level d but assert that such relations even when cast into a dimensionless form are of limited utility because they fail to portray the effect of breach formation rate we then analyze a simple physically based model of dam breach formation to show that the hydrograph at the breach depends primarily on a dimensionless parameter kv0 gl 2d7 2 where k is the mean erosion rate of the breach and g is acceleration due to gravity the functional relationship between qp and takes asymptotically distinct forms depending on whether 1 relatively slow breach formation or small lake volume or 1 relatively fast breach formation or large lake volume theoretical predictions agree well with data from dam failures for which k and thus can be estimated the theory thus provides a rapid means of predicting the plausible range of values of peak discharge at the breach in an earthen dam as long as the impounded water volume and the water depth at the dam face can be estimated

petrographic and coalification variations in the eastern southland lignites new zealand abstract the upper oligocene to lower miocene gore lignite measures of eastern southland accumulated in humid temperature to subtropical wet forest swamps in a coastal delta plain paleoenvironment the lignites have relatively low ash and low sulphur contents they are xylitic contain abundant resinite and range from poorly to strongly gelified petrographically they are relatively uniform and dominated by humic macerals the eastern southland lignite field can be divided into a southern lower rank and a northern higher rank area the lower rank lignites have bed moisture contents of 55 61 whereas the higher rank lignites have bed moistures of 42 46 in both areas the lignite seams are within 200 m of the surface but are probably separated by faults and have undergone separate burial and tectonic histories burial depths are believed to range from 250 m for lower rank to 1100 m for higher rank lignites the rank increase from south to north is largely the result of compaction induced reduction in porosity and consequent dewatering and is not accompanied by any notable increase in gelification for these lignites there is a linear relationship between bed moisture and fixed carbon but a significant shift away from the linear relationship between volatile matter and specific energy and bed moisture also the higher rank northern lignites have higher h c and lower o c atomic ratios than the southern lower rank lignites these geochemical changes are heat and depth related and represent changes in functional group composition that are independent of observed gelification