effects of dem resolution on the calculation of topographical indices twi and its components summary a variety of landscape properties have been modelled successfully using topographic indices such as the topographic wetness index twi defined as ln a tan where a is the specific upslope area and is the surface slope previous studies have shown the influence of scale on twi values when converting standard resolution dems to coarser resolutions in this study a high resolution digital elevation model dem with a 5 m grid size derived from lidar light detection and ranging data was used to investigate the scale dependency of twi values when converting from high resolution elevation data to standard resolution dems first a set of dems was generated from an initial dem by thinning to resolutions of 10 25 and 50 m grid sizes to study the effects of lower grid size and decreased information content next to investigate the impact of different information content on dems with the same grid size the three lower resolution dems were all interpolated to the original 5 m grid size in addition to comparing index distribution functions a second objective was to evaluate differences in spatial patterns thus the values of twi and its components as computed for the seven different dems were compared in three different ways 1 distribution functions and their statistics 2 cell by cell comparison of four dems with the same resolution but different information content and 3 comparison of blocks of cells within different resolution dems with different information content like previous twi studies the computed specific upstream area decreased on average for higher resolution dems while computed slope values followed a narrower distribution twi variation between neighbouring cells in 50 50 m areas decreased largely with increasing grid size a cell by cell comparison of the twi values of the four 5 m dems with different information content showed a clear decrease in correlation with the twi based on the original dem with decreasing information content the results showed considerable differences between topographic indices computed for dems of different grid resolution interpolating the dems to a higher resolution i e a smaller grid size provided more similar twi distributions but the pixel by pixel comparison showed that different information contents caused clearly different twi maps

volcanic coseismic and seasonal changes detected at white island whakaari volcano new zealand using seismic ambient noise ambient noise interferometry is becoming increasingly popular for studying seismic velocity changes such changes contain information on the structural and mechanical properties of earth systems application to monitoring however is complicated by the large number of processes capable of inducing crustal velocity changes we demonstrate this at white island volcano over a 10 year period containing multiple well documented eruptions using individual seismic stations we detect velocity perturbations that we ascribe to volcanic activity large earthquakes and seasonality distant seismic stations capture widespread nonvolcanic changes that are also present at the volcano comparison between velocity changes recorded by distant and local stations then allows us to distinguish volcanic phenomena from seasonality through this we resolve distinct features in ambient noise derived velocity changes that relate to volcanic unrest and a phreatic eruption illustrating the strength of the approach plain language summary detecting small changes in physical properties at volcanoes is important toward effectively forecasting volcanic eruptions one approach is to monitor the speed of seismic waves at the earth s surface which are sensitive to changes in the rock they pass through at volcanoes such changes may manifest through subsurface pressure increases preceding eruptions correctly interpreting these changes however is complicated many other nonvolcanic processes are also capable of producing similar wave speed perturbations at white island volcano new zealand we detect changes associated with volcanic activity large earthquakes and weather related processes using seismometers located on the volcano we demonstrate that volcanic and nonvolcanic features can be distinguished by comparing changes recorded at the volcano with those recorded at large distances where volcanic changes are not expected to be observed through this we resolve distinct differences that can be related to volcanic activity illustrating the strength of this approach

the relation between site amplification factor and surficial geology in central california abstract site amplification factors at frequencies of 1 5 3 6 and 12 hz were determined for 132 stations of the usgs seismic network in central california from coda waves of 185 local earthquakes in this area using a recursive stochastic inversion method we found that the site amplification at a station is systematically related to the geology underlying that station the site amplification is high for young quaternary sediments and decreases with increasing geologic age at all frequencies between 1 5 and 12 hz the rate of decrease varies with frequency where site amplification at low frequencies shows a faster rate of decrease with age than at higher frequencies to quantify the relation between site amplification factor and site geology the surface geology of station sites was classified into five groups namely 1 quaternary sediments 2 pliocene sediments 3 miocene through cretaceous sediments 4 franciscan formation and mesozoic granitic rocks and 5 pre cretaceous metamorphic rocks the station site amplification factors for each group were logarithmically averaged and the mean value was assigned to the median geologic age of that group a smooth power law relation was found between the mean site amplification and the median geologic age this relation provides a simple way of estimating site effect at a specific site with known surficial geology our site amplification factors were compared with magnitude station residuals determined by eaton 1990 for the same network a remarkable linear correlation was found between the logarithmic coda amplification factor and the magnitude station residual value confirming that the coda method provides an effective means of estimating site amplification factor comparison of our site amplification factor with strong motion results obtained from the loma prieta earthquake boore et al 1989 maley et al 1989 shakal et al 1989 chin and aki 1991 suggests that weak and strong motion site amplification factors correlate well in the region outside the epicentral source region beyond epicentral distances of about 50 km within the epicentral source region however the weak motion amplification factors estimated from coda waves do not agree with the observed for strong ground motion suggesting a nonlinear behavior at sediment sites these results together with studies on the correlation between weak motion site amplification and earthquake intensity borcherdt 1970 borcherdt and gibbs 1976 chavez garcia et al 1990 king et al 1990 demonstrate the importance of in situ determination of weak motion site amplification for seismic zonation

damage and ground shaking in the town of nocera umbra during umbria marche central italy earthquakes the special effect of a fault zone on 26 september 1997 the town of nocera umbra central italy was strongly hit by two nearby m l 5 6 and 5 8 earthquakes the effects were particularly heavy in the historical part of the town on the top of a 120 m high hill however also modern zones along the topino valley suffered severe damage with many partial collapse episodes aftershock recordings in different zones stressed the occurrence of large variations of the ground motion strength within the town these observations suggest that the spatially heterogeneous distribution of damage in nocera umbra should have been a combination of variations of both building vulnerability and ground shaking intensity within the town we have identified six microzones characterized by different vulnerability and or varying geological and topographical conditions in each of them the number of damaged houses is computed for vulnerability types a b and c according to the european macroseismic scale 1998 ems 98 this procedure yields a macroseismic intensity of vii viii on the hill in the historical part of the town in this zone the topography amplification has a limited extent while the quality of the construction materials is poor the diffuse damage is then interpreted as an effect of the higher vulnerability of buildings in the historical zone the other urbanized zones of nocera umbra are composed of more recent less vulnerable buildings in spite of the almost homogeneous building vulnerability the observed damage grades show significant variations between the remaining five microzones in particular damage grades related to intensity as low as vi vii were assessed for undisturbed mesozoic limestone and stiff cenozoic mesozoic marly sandstone zones where aftershock seismograms show the smallest relative amplitudes the highest damage grades related to intensity viii were estimated for two zones on the soft sediment deposits in the topino river valley and on the fractured marly sandstone terrains within a 200 m wide fault zone crossing the town of nocera umbra such an increment of one to two degrees in ems intensity corresponds to a maximum spectral amplification of horizontal ground motion around 4 hz that is as large as 20 on the soft sediment deposits and even larger within the fault zone

surface rupture during the 2010 mw 7 1 darfield canterbury earthquake implications for fault rupture dynamics and seismic hazard analysis the september 2010 m w 7 1 darfield canterbury earthquake in new zealand is one of the best recorded earthquakes of this magnitude the earthquake occurred on a previously unidentified fault system and generated a 29 5 0 5 km long surface rupture across a low relief agricultural landscape high accuracy measurements of coseismic displacements were obtained at over 100 localities along the greendale fault maximum net displacement d max 5 3 0 5 m and average net displacement d avg 2 5 0 1 m are anomalously large for an earthquake of this m w d max surface rupture length srl and d avg srl ratios are among the largest ever recorded for a continental strike slip earthquake geologically derived estimates of moment magnitude m w g are less than the seismologically derived m w derived using widely employed srl m w scaling regressions m w g is greater than m w using d max and d avg m w regressions the geologically derived static stress drop of 13 9 3 7 mpa provides a context with which to compare this earthquake rupture to interplate and intraplate ruptures of similar m w this data set provides fundamental information on fault rupture processes relevant to seismic hazard modeling in this region and analogous settings globally

ambient noise cross correlation observations of fundamental and higher mode rayleigh wave propagation governed by basement resonance measurement of basement seismic resonance frequencies can elucidate shallow velocity structure an important factor in earthquake hazard estimation ambient noise cross correlation which is well suited to studying shallow earth structure is commonly used to analyze fundamental mode rayleigh waves and increasingly love waves here we show via multicomponent ambient noise cross correlation that the basement resonance frequency in the canterbury region of new zealand can be straightforwardly determined based on the horizontal to vertical amplitude ratio h v ratio of the first higher mode rayleigh waves at periods of 1 3 s the first higher mode is evident on the radial radial cross correlation functions but almost absent in the vertical vertical cross correlation functions implying longitudinal motion and a high h v ratio a one dimensional regional velocity model incorporating a 1 5 km thick sedimentary layer fits both the observed h v ratio and rayleigh wave group velocity similar analysis may enable resonance characteristics of other sedimentary basins to be determined

cloudiness and marine boundary layer dynamics in the astex lagrangian experiments part i synoptic setting and vertical structure abstract a goal of the atlantic stratocumulus transition experiment astex southeast of the azores islands in the east central atlantic ocean during june 1992 was to examine the coupled evolution of cloud dynamical and thermodynamical vertical structure in a marine boundary layer mbl air mass as it advected from cold to warm water in the trade winds in two lagrangian observation periods during astex an unprecedentedly complete view of mbl and cloud evolution was achieved by nearly continuous aircraft coverage of such an air mass for 36 48 hours using three boundary layer aircraft supplemented by satellite ship and balloon observations during the first lagrangian period an accelerated stratocumulus to trade cumulus transition occurred in a clean marine air mass in the second lagrangian period a 200 hpa deep decoupled modified continental mbl persisted with almost no change in structure cumulus rising into intermittent stratocumulus were observed throughout the period the two contrasting a

high resolution relocation of aftershocks of the mw 7 1 darfield new zealand earthquake and implications for fault activity 1 low slip rate regions often represent under recognized hazards and understanding the progression of seismicity when faults in such areas rupture will help us to better understand earthquake rupture patterns the 3 september 2010 utc mw 7 1 darfield earthquake revealed a formerly unrecognized set of faults in the canterbury region of new zealand an area that had previously been mapped as one of the lower hazard areas in the country in this study we analyze the first four months of its aftershock sequence to identify active faults and temporal changes in seismicity along them we jointly invert for three dimensional p wave and s wave velocities and hypocentral locations using data for 2840 aftershocks recorded at 36 temporary and permanent seismic stations within 70 km of the main shock epicenter these relocations delineate eight individual faults active prior to the 22 february 2011 mw 6 3 christchurch earthquake the largest aftershock of the darfield earthquake two of these faults are in the christchurch region one of which corresponds to geodetically determined rupture planes of the christchurch earthquake using focal mechanisms calculated from first motion polarities we find mainly strike slip faulting events with some reverse and normal faulting events as well we compare the orientations of these faults to the prevailing regional stress directions to identify which faults may have been active prior to the darfield earthquake and which may be newly developed

shear wave velocity changes induced by earthquakes and rainfall at the rotokawa and ngatamariki geothermal fields taupō volcanic zone new zealand

temporal evolution of surface rupture deduced from coseismic multi mode secondary fractures insights from the october 8 2005 mw 7 6 kashmir earthquake nw himalaya abstract detailed rupture fracture analyses of some of the well studied earthquakes have revealed that the geometrical arrangement of secondary faults and fractures can be used as a geological tool to understand the temporal evolution of slip produced during the mainshock the october 8 2005 mw 7 6 kashmir earthquake nw himalaya surface rupture provides an opportunity to study a complex network of secondary fractures developed on the hanging wall of the fault scarp the main fault scarp is clearly thrust type rupture length is 75 5 km and the overall trend of the rupture is nw se we present the results of our detailed structural mapping of secondary faults and fractures at 1 100 scale on the hanging wall of the southern end of the rupture in the vicinity of the sar pain secondary ruptures can be broadly classified as two main types 1 normal faults and 2 right lateral strike slip riedel fractures the secondary normal faults are nw se striking with a maximum 3 3 meter vertical displacement and 2 5 meter horizontal displacement estimated total horizontal extension across the secondary normal faults is 3 1 3 5 we propose that the bending moment and coseismic stress relaxation can explain the formation of secondary normal faults on the hanging wall of the thrust fault the strike slip riedel fractures form distinct sets of tension t and shear fractures r r y with right lateral displacement field observations revealed that the riedel fractures t cut the secondary normal faults in addition there is kinematic incompatibility and magnitude mismatch between the secondary normal faults and strike slip riedel fractures the cross cutting relationship geometric and magnitude incoherence implies a temporal evolution of slip from dip to strike slip during the mainshock faulting the interpretation is consistent with the thrust fault plane solution with minor right lateral strike slip component

comparison of methods for predicting regolith thickness in previously glaciated terrain stockholm sweden abstract knowledge about regolith thickness is important in several civil and environmental engineering fields however subsurface characteristics such as regolith thickness are difficult to determine through surface investigations and maps at regional scales this paper presents four methods for estimating regolith thickness in a gis environment for previously glaciated terrain with high frequency of rock outcrops linear regression lr using topographical covariates inverse distance weighting idw interpolation of regolith thickness point data from well drillings a trigonometrical approach ta developed for this study which uses outcrop slopes and distance between outcrops and a simplified regolith model srm the srm is a model modified from ta which estimates the regolith thickness based on outcrops slopes and the distance to outcrops in eight directions the methods were compared for three study areas tyreso vallentuna and osteraker in stockholm county sweden based on the results in this paper lr proved to be the most accurate method for regolith thickness estimation measured through root mean square error values whereas idw was the most accurate method in terms of error within 2 m which would make it a suitable model if and when large datasets of regolith point data are available when drilling data is scarce then both the ta and srm methods can be used for regolith estimations however the srm proved to be a more accurate regolith thickness model compared to ta srm shows promising results and could be used at a preliminary stage in engineering projects where little or no data is available prior to detailed field investigations in previously glaciated terrain

mapping the distribution of weathered pleistocene wadi deposits in southern jordan using aster spot 5 data and laboratory spectroscopic analysis abstract in the arid regions of the levant ancient wadi fills act as a terrestrial sedimentary archive with a high potential for preserving archaeological findings this current study combines remote sensing with laboratory vis spectroscopy to investigate the spatial distribution of alluvial wadi fills in a small catchment in southern jordan due to its homogeneous sandstone geology the composition of the alluvial sediments is highly influenced by the local bedrock whilst fluvial relocation and surface weathering processes initiated a secondary alteration of dominant iron oxides fe 3 the differences in mineralogical composition of the sediments enable the detection and mapping of wadi deposits by remote sensing using different spectral combinations of aster and spot 5 satellite images additionally laboratory measurements of reflectance spectra were applied on selected surface samples and soil sections from the study area in order to verify the information derived from remote sensing and to quantify the degree of surface weathering and pedogenic processes the results show that an initial transformation from hematite to goethite is the dominant process related to the recent arid conditions in the study area furthermore it is possible to predict potential new archaeological finding areas using remote sensing techniques

geophysical and remote sensing based approach to model regolith thickness in a data sparse environment abstract mapping regolith thickness to bedrock is important for environmental modeling in general and for seismic hazard assessment in particular however regolith thickness is often ignored in such studies because of its presumed difficulty of mapping in many terrains to overcome this limitation we developed a generic remote sensing and geophysics based approach to model regolith thickness for areas with limited possibility of direct field observations the approach was tested in a seismically active and depositional landscape in northern pakistan regolith thickness was sampled at exposed bedrock outcrops along the river bed and scarps at unexposed sites the regolith bedrock interface was identified through electrical resistivity survey thus providing an indirect measurement of regolith thickness a geomorphic classification of landforms and topographic attributes were derived from a remote sensing based aster digital elevation model and spot 5 satellite imagery landform was the most important predictor adjusted r2 72 1 showing the importance of geomorphic interpretation a multivariate linear model based on landform elevation and distance to stream was able to predict the regolith thickness adjusted r2 91 7 including field observed abrupt changes at landform boundaries

seismic velocity changes in the epicentral region of the 2008 wenchuan earthquake measured from three component ambient noise correlation techniques 1 we investigate temporal changes of seismic velocity in the epicentral region of the 12 may 2008 mw 7 9 wenchuan earthquake using three component continuous waveforms recorded by a seven station small aperture array we use an ambient noise cross correlation technique to compute the empirical green s function between station pairs from august 2004 to september 2011 our results show no obvious precursory change immediately before the main shock clear coseismic reduction of seismic velocity of up to 0 2 and initial postseismic recovery followed by a long lived velocity reduction the coseismic and postseismic velocity changes are most prominent in the period band of 2 4 s approximate depth of 1 4 km and the velocity changes are smaller in other period bands the seismic velocity in the period band of 1 2 s i e top 2 km correlates well with the water level change of the zipingpu reservoir the observed temporal changes likely reflect damage and healing processes with possible permanent deformation in the upper crust associated with the wenchuan main shock

regolith modeling and its relation to earthquake induced building damage a remote sensing approach regolith thickness is known as a major factor in influencing the intensity of earthquake induced ground shaking and consequently building damages it is however often simplified or ignored due to its variable and complex nature to evaluate the role of regolith thickness on earthquake induced building damage a remote sensing based methodology is developed to model the spatial variation of regolith thickness based on dem derived topographic attributes and geology regolith thickness samples were evenly collected in geological formations at representative sites of topographic attributes topographic attributes elevation slope twi distance from stream computed from the aster derived dem and a geology map were used to explore their role in spatial variation of regolith thickness stepwise regression was used to model the spatial variation of regolith thickness in erosional landscape of the study area topographic attributes and geology explain 60 of regolith thickness variation in the study area to test if the modeled regolith can be used for prediction of seismic induced building damages it is compared with the 2005 kashmir earthquake induced building damages derived from high resolution remote sensing images and field data the comparison shows that the structural damages increase with increasing regolith thickness the predicted regolith thickness can be used for demarcating site prone to amplified seismic response

depth variable crustal anisotropy patterns of crustal weakness and destructive earthquakes in canterbury new zealand abstract low strain rate areas of the earth are often host to long recurrence but damaging earthquake cycles in many cases these events occur on reactivated and previously unrecognized faults noise based imaging of seismic anisotropy is capable of revealing the seismic fabric of inherited structures as well as the preferred orientation of pervasive cracking in the upper crust both features with a potential relationship to failure on faults causing catastrophic earthquakes by understanding the orientation of seismic weaknesses seismic hazard in areas of low strain rate can be better understood the geometric relation of crustal anisotropy and the 3 d crustal stress tensor has the potential to qualitatively inform us of the location and or orientation of large crustal earthquakes in regions with little previously recorded seismicity but known tectonic loading directions in this study noise cross correlation techniques were used to measure surface wave dispersion these measurements were inverted to solve for azimuthal anisotropy of fundamental mode rayleigh waves in the canterbury region of the south island of new zealand the results of passive imaging show a distinct difference in magnitude and azimuth of surface wave anisotropy at different depths within the crust across the region we suggest that the approximately east west fast axis orientation at upper crustal depths reflects the cretaceous faulting of the impacting chatham rise and the approximately northeast southwest fast axis orientation at lower crustal depths reflects the present plate boundary strain direction the upper crust fast axis parallels the surface rupturing greendale fault which gave rise to the ongoing destructive canterbury earthquake sequence we suggest that the upper crust azimuthal anisotropy measured using ambient noise is capable of revealing dominant patterns of crustal weaknesses in regions like canterbury which are prone to low recurrence but highly damaging earthquakes

monitoring a temporal change of seismic velocity in a volcano application to the 1992 eruption of mt merapi indonesia multiplets i e events with similar waveforms are selected from shallow earthquakes recorded on merapi volcano indonesia before the eruption of february 2nd 1992 two multiplet families are found with their sources close to the summit their seismograms are analyzed using the moving window cross spectrum technique which measures the precise time delay between seismic phases in the entire seismogram for both families of multiplets a gradual decrease in the arrival times of coda waves is observed as a function of the date prior to the eruption coda waves are becoming progressively faster up to 1 2 per cent as the time interval to the eruption shortens this observation is interpreted as the consequence of an increase in the seismic velocity inside the volcano the increase in velocity started in may 1991 and was observed until september 1991 4 months before the eruption this velocity increase may be related to an increase in pressure in the magma chamber or in the conduits and to the resulting closure of the surrounding cracks

effects of realistic surface topography on seismic ground motion in the yangminshan region of taiwan based upon the spectral element method and lidar dtm we combine light detection and ranging lidar digital terrain model dtm data and an improved mesh implementation to investigate the effects of high resolution surface topography on seismic ground motion based upon the spectral element method in general topography increases the amplitude of shaking at mountain tops and ridges whereas valleys usually have reduced ground motion as has been observed in both records from past earthquakes and numerical simulations however the effects of realistic topography on ground motion have not often been clearly characterized in numerical simulations especially the seismic response of the true ground surface here we use lidar dtm data which provide two meter reso lution at the free surface and a spectral element method to simulate three dimensional 3d seismic wave propagation in the yangminshan region in taiwan incorporating the effects of realistic topography a smoothed topographic map is employed beneath the model surface in order to decrease mesh distortions due to steep ground surfaces numerical simulations show that seismic shaking in mountainous areas is strongly affected by topography and source frequency content the amplification of ground motion mainly occurs at the tops of hills and ridges whilst the valleys and flat topped hills experience lower levels of ground shaking interaction between small scale to pographic features and high frequency surface waves can produce unusually strong shaking we demonstrate that topographic variations can change peak ground accel eration pga values by 50 in mountainous areas and the relative change in pga between a valley and a ridge can be as high as a factor of 2 compared to a flat surface response this suggests that high resolution realistic topographic features should be taken into account in seismic hazard analysis especially for densely populated moun tainous areas

fundamental and higher mode rayleigh wave characteristics of ambient seismic noise in new zealand 1 in order to use ambient seismic noise for mapping earth s structure it is important to understand the spatiotemporal characteristics of the noise field this study uses data collected during four austral winter months of 2002 to investigate new zealand s ambient seismic noise field in the double ocean wave frequency range 0 1 0 3 hz it is shown via beamforming analysis that there are two distinct dispersive waves in the data these waves can be separated their estimated phase velocities 2 5 2 and 4 3 km s in the frequency range 0 14 0 25 hz match well with fundamental and higher mode rayleigh dispersion curves studies of double wave frequency microseisms elsewhere generally show the rayleigh noise fields to be dominated by fundamental mode waves the reason why higher mode signals are observed here may reflect a combination of long ocean wave periods large waveheights the direct deep water approach to narrow continental margins and the proximity of the seismograph array to the source regions citation brooks l a j townend p gerstoft s bannister and l carter 2009 fundamental and higher mode rayleigh wave characteristics of ambient seismic noise in new zealand geophys res lett 36 l23303 doi 10 1029 2009gl040434

an overview of local site effects and the associated building damage in adapazari during the 17 august 1999 izmit earthquake two major earthquakes occurred in turkey along the north anatolian fault in 1999 the first one which occurred on 17 august 1999 had a moment magnitude of 7 4 and ruptured the 140 km segment of the fault in the marmara region adapazari a city with a population of 190 000 which is mostly located on a deep alluvial basin in the near field of the ruptured fault was among the worst affected urban areas in the earthquake affected region the distribution of damage over the city was highly nonuniform indicating the variability of the ground response to the strong motion five to six story buildings located over deep alluvial soils were most adversely affected by the earthquake geotechnical characteristics of the alluvial basin of adapazari are evaluated using the deep and shallow borehole logs and the measured parameters from the field and laboratory this data is used for developing representative one dimensional site response models for various depths of alluvium and for liquefaction assessment in saturated surface soils recorded data from several aftershocks are utilized for model calibration the results of soil response studies are found to be highly correlated with the general trends in the intensity and distribution of building damage based on in situ tests soil liquefaction is determined to have occurred extensively in adapazari which is in conformity with the postearthquake observations of widespread liquefaction induced foundation displacements evidently liquefied soil layers served as passive isolation mechanism for numerous buildings some of which were subjected to excessive foundation displacements of various forms without signs of significant structural damage manuscript received 30 august 2000

amplification of seismic waves by the seattle basin washington state recordings of the 1999 m w 7 6 chi chi taiwan earthquake two local earthquakes and five blasts show seismic wave amplification over a large sedimentary basin in the u s pacific northwest for weak ground motions from the chi chi earthquake the seattle basin amplified 0 2 to 0 8 hz waves by factors of 8 to 16 relative to bedrock sites west of the basin the amplification and peak frequency change during the chi chi coda the initial s wave arrivals 0 30 sec had maximum amplifications of 12 at 0 5 0 8 hz whereas later arrivals 35 65 sec reached amplifications of 16 at 0 3 0 5 hz analysis of local events in the 1 0 to 10 0 hz frequency range show fourfold amplifications for 1 0 hz weak ground motion over the seattle basin amplifications decrease as frequencies increase above 1 0 hz with frequencies above 7 hz showing lower amplitudes over the basin than at bedrock sites modeling shows that resonance in low impedance deposits forming the upper 550 m of the basin beneath our profile could cause most of the observed amplification and the larger amplification at later arrival times suggests surface waves also play a substantial role these results emphasize the importance of shallow deposits in determining ground motions over large basins

temporal changes of surface wave velocity associated with major sumatra earthquakes from ambient noise correlation abstract detecting temporal changes of the medium associated with major earthquakes has implications for understanding earthquake genesis here we report temporal changes of surface wave velocity over a large area associated with 3 major sumatra earthquakes in 2004 2005 and 2007 we use ambient noise correlation to retrieve empirical green s function egf of surface waves between stations because the process is completely repeatable the technique is powerful in detecting possible temporal change of medium we find that 1 excellent station pair psi in indonesia and chto in thailand shows significant time shifts up to 1 44 s after the 2004 and 2005 events in the rayleigh waves at 10 20 s but not in the love waves suggesting that the rayleigh time shifts are not from clock error the time shifts are frequency dependent with the largest shifts at the period band of 11 16 s we also observe an unusual excursion 1 month before the 2004 event we obtain a total of 17 pairs for june 2007 to june 2008 which allow us to examine the temporal and spatial variation of the time shifts we observed strong anomalies up to 0 68 s near the epicenter after the 2007 event but not in the region further away from the source or before the event or 3 months after the event the observations are interpreted as stress changes and subsequent relaxation in upper mid crust in the immediate vicinity of the rupture and the broad area near the fault zone

localized damage caused by topographic amplification during the 2010 m 7 0 haiti earthquake microzonation maps use local geological conditions to characterize seismic hazard but do not generally consider topography ground motions during the haiti earthquake are found to have been significantly amplified along a high topographic ridge which caused substantial structural damage indicating that topography can play an important role in seismic hazard local geological conditions including both near surface sedimentary layers1 2 3 4 and topographic features5 6 7 8 9 are known to significantly influence ground motions caused by earthquakes microzonation maps use local geological conditions to characterize seismic hazard but commonly incorporate the effect of only sedimentary layers10 11 12 microzonation does not take into account local topography because significant topographic amplification is assumed to be rare here we show that although the extent of structural damage in the 2010 haiti earthquake was primarily due to poor construction topographic amplification contributed significantly to damage in the district of petionville south of central port au prince a large number of substantial relatively well built structures situated along a foothill ridge in this district sustained serious damage or collapse using recordings of aftershocks we calculate the ground motion response at two seismic stations along the topographic ridge and at two stations in the adjacent valley ground motions on the ridge are amplified relative to both sites in the valley and a hard rock reference site and thus cannot be explained by sediment induced amplification instead the amplitude and predominant frequencies of ground motion indicate the amplification of seismic waves by a narrow steep ridge we suggest that microzonation maps can potentially be significantly improved by incorporation of topographic effects

evaluation of remote sensing based seismic site characterization using earthquake damage data terra nova 24 123 129 2012 abstract preparing seismic site characterization maps requires extensive geological and geotechnical data collection and interpretation this study evaluates a remote sensing based method to generate seismic site characterization map at 30 m spatial resolution geographical object based image analysis was applied to topographic attributes computed from an advance spaceborne thermal emission and reflection radiometer digital elevation model to demarcate terrane units of mountains piedmonts and basins classified terrane units were verified through a field based landform map resulting in an accuracy of 70 to evaluate the importance of classified terrane units for seismic site characterization and their role in earthquake induced building damage the classified terrane units were compared with 2005 kashmir earthquake damage data derived from field visits and spot 5 imagery this shows that 81 of the less moderate and severe damage intensity zones correspond with mountains piedmonts and basins respectively classified terrane units were assigned vs30 to generate a seismic site characterization map

a review of the 2005 kashmir earthquake induced landslides from a remote sensing prospective abstract the 8th october 2005 kashmir earthquake in northern pakistan has triggered thousands of landslides which was the second major factor in the destruction of the build up environment after earthquake induced ground shaking subsequent to the earthquake several researchers from home and abroad applied a variety of remote sensing techniques supported with field observations to develop inventories of the earthquake triggered landslides analyzed their spatial distribution and subsequently developed landslide susceptibility maps earthquake causative fault rupture geology anthropogenic activities and remote sensing derived topographic attributes were observed to have major influence on the spatial distribution of landslides these were subsequently used to develop a landslide susceptibility map thereby demarcating the areas prone to landsliding temporal studies monitoring the earthquake induced landslides shows that the earthquake induced landslides are stabilized contrary to earlier belief directly after the earthquake the biggest landslide induced dam as a result of the massive hattian bala landslide is still posing a threat to the surrounding communities it is observed that remote sensing data is effectively and efficiently used to assess the landslides triggered by the kashmir earthquake however there is still a need of more research to understand the mechanism of intensity and distribution of landslides and their continuous monitoring using remote sensing data at a regional scale this paper provides an overview of remote sensing and gis applications for the kashmir earthquake triggered landslides derived outputs and discusses the lessons learnt advantages limitations and recommendations for future research

the impact of vertical resolution upon gcm simulations of marine stratocumulus the impact of increased vertical resolution in the hadley centre climate model upon the simulation of stratocumulus is investigated in experiments using single column scm and general circulation gcm model configurations a threefold enhancement of vertical resolution in the boundary layer leads to improvements in the vertical structure of the cloud topped boundary layer produced by the scm and gcm in both well mixed and decoupled situations however single and decoupled mixed layers in the marine stratocumulus subsidence regions are still too shallow and despite increasing layer cloud amounts remain generally too low moreover closer examination of gcm data and scm timeseries reveals an underlying sensitivity to vertical resolution in model interactions between boundary layer and convection processes which appears unrealistic stratocumulus simulation is thus unlikely to improve significantly as a result of enhanced resolution alone and further work is being undertaken to improve the hadley centre model s boundary layer scheme and in particular its interaction with the convection scheme nevertheless this study shows that the full benefit of an improved boundary layer scheme will not be realized if the boundary layer structure is constrained by the rather poor lower troposphere resolution of the standard 19 level climate model future hadley centre model versions will seek to combine the added flexibility of a better resolved structure with improvements to the subgrid boundary layer parametrizations

numerical simulations and a conceptual model of the stratocumulus to trade cumulus transition abstract a two dimensional eddy resolving model is used to study the transition from the stratocumulus topped boundary layer to the trade cumulus boundary layer the 10 day simulations use an idealized lagrangian trajectory representative of summertime climatological conditions in the subtropical northeastern pacific the sea surface temperature is increased steadily at 1 5 k day 1 reflecting the southwestward advection of the subtropical marine boundary layer by the trade winds while the free tropospheric temperature remains unchanged results from simulations with both a fixed diurnally averaged shortwave radiative forcing and a diurnally varying shortwave forcing are presented a two stage model for the boundary layer evolution consistent with these simulations is proposed in the first stage decoupling is induced by increased latent heat fluxes in the deepening boundary layer after decoupling cloud cover remains high but the cloudiness regime changes from a single stratocumulus layer to sporadic

groundwater responses to the recent canterbury earthquakes a comparison summary the recent canterbury christchurch earthquakes and aftershocks generated groundwater level responses throughout new zealand however the greater part of damage has been sustained by the city of christchurch which is built on a layered sequence of artesian aquifers in this paper we focus on responses in these coastal aquifers we quantify groundwater responses with a simple model which differentiates between immediate earthquake induced response spike and post seismic change offset the most significant feature of our analysis is the consistent pattern of groundwater response to the earthquakes deeper wells correlate with negative offset and shallower wells correlate with positive offset this is consistent with the upwards vertical movement of water we consider the hydrological and engineering consequences

observations of the interaction between cumulus clouds and warm stratocumulus clouds in the marine boundary layer during astex abstract decoupling of the marine boundary layer beneath stratocumulus clouds and the formation of cumulus clouds at the top of a surface based mixed layer sml have frequently been observed and modeled when such cumulus clouds penetrate the overlying stratocumulus layer the cloud microphysics and hence the radiative properties of the cloud are altered locally observations made during a series of lagrangian experiments in the azores as part of the atlantic stratocumulus transition experiment astex june 1992 have been analyzed to ascertain how the properties of a stratocumulus layer with which cumulus clouds are interacting differ from those of an unaffected cloud layer the results suggest that in regions where cumulus clouds penetrate the cloud layer the stratocumulus is thickened as the cumuli spread out into its base transport of air from the sml into the cloud by convective updrafts is observed and the increase in available moisture within the penetrating cumulus clouds results in increased

extracting damages caused by the 2008 ms 8 0 wenchuan earthquake from sar remote sensing data abstract bad weather conditions usually limit the acquisition of optical remote sensing images while all day and all weather synthetic aperture radar sar shows the ability of providing timely remote sensing data for emergency response and rescue works after earthquake because sar is sensitive to the surface changes caused by earthquake the modified electromagnetic behaviour by geological disasters and the collapse of buildings can be recorded in sar images as backscattering intensity changes absolute radiometric calibration was performed to sar products to derive backscattering coefficient sigma nought from image digital number dn based on change detection methods advanced land observing satellite alos phased array type l band synthetic aperture radar palsar data and terrasar x data acquired for the ms 8 0 wenchuan earthquake were used to extract earthquake damage information this study revealed that landslides showed stronger backscattering and barrier lakes showed lower backscattering in post earthquake 10 m alos palsar images comparing to pre earthquake and collapsed buildings showed lower backscattering compared to un collapsed buildings in 1 m terrasar x image results showed that sar data with different spatial resolutions are useful for different earthquake damage information extraction medium spatial resolution sar data e g 10 m alos palsar data were efficient for secondary geological disaster extraction high resolution sar data e g 1 m terrasar x data with the help of ancillary gis data or high resolution optical data could be used to extract building collapse information in urban areas this study indicates that sar remote sensing data can provide earthquake damage information at early emergency stage and assist the field surveying further damage assessment and post earthquake reconstruction

strong motion from surface waves in deep sedimentary basins it is widely recognized that long period surface waves generated by conversion of body waves at the boundaries of deep sedimentary basins make an important contribution to strong ground motion the factors controlling the amplitude of such motion however are not widely understood a study of pseudovelocity response spectra of strong motion records from the los angeles basin shows that late arriving surface waves with group velocities of about 1 km sec dominate the ground motion for periods of 3 sec and longer the rate of amplitude decay for these waves is less than for the body waves and depends significantly on period with smaller decay for longer periods the amplitude can be modeled by the equation batchmode documentclass fleqn 10pt legalpaper article usepackage amssymb usepackage amsfonts usepackage amsmath pagestyle empty begin document mathrm log y f mathbf m r mathrm e c br mathrm b end document where y is the pseudovelocity response f m r e is an attenuation relation based on a general strong motion data set m is moment magnitude r e is the distance from the source to the edge of the basin r b is the distance from the edge of the basin to the recording site and b and c are parameters fit to the data the equation gives values larger by as much as a factor of 3 than given by the attenuation relationships based on general strong motion data sets for the same source site distance it is clear that surface waves need to be taken into account in the design of long period structures in deep sedimentary basins the ground motion levels specified by the earthquake provisions of current building codes in california at least accommodate the long period ground motions from basin edge generated surface waves for periods of 5 sec and less and earthquakes with moment magnitudes of 7 5 or less located more than 20 km outside the basin there may be problems at longer periods and for earthquakes located closer to the basin edge the results of this study suggest that anelastic attenuation may need to be included in attempts to model long period motion in deep sedimentary basins to obtain better data on surface waves in the future operators of strong motion networks should take special care for the faithful recording of the long period components of ground motion it will also be necessary to insure that at least some selected recorders once triggered continue to operate for a time sufficient for the surface waves to traverse the basin with velocities of about 1 km sec that time will be as long as 100 sec for a basin the size of the los angeles basin

shear velocity structure of the northland peninsula new zealand inferred from ambient noise correlations 1 ambient noise correlation has been successfully applied in several cases to regions with dense seismic networks whose geometries are well suited to tomographic imaging the utility of ambient noise correlation based methods of seismic imaging where either network or noise field characteristics are less ideal has yet to be fully demonstrated in this study we focus on the northland peninsula of new zealand using data from five seismographs deployed in a linear pattern parallel to the direction from which most of the ambient noise arrives shear wave velocity profiles computed from rayleigh and love wave dispersion curves using the neighborhood algorithm are in good agreement with the results of a previous active source refraction experiment and a teleseismic receiver function and surface wave analysis in particular we compute a path averaged moho depth of 28 km along a 250 km profile the use of both rayleigh and love wave measurements enables us to estimate the degree of radial anisotropy in the crust yielding values of 2 15 these results demonstrate that ambient noise correlation methods provide useful geophysical constraints on lithospheric structure even for nonoptimal network geometries and noise field characteristics

diurnal evolution of the cloud topped marine boundary layer part i nocturnal stratocumulus development abstract the structure and evolution of the extratropical marine atmosphere boundary layer mabl depend largely on the variability of stratus and stratocumulus clouds stratus clouds are generally associated with a well mixed mabl whereas daytime observations of stratocumulus topped boundary layers generally indicate that the cloud and subcloud layers are decoupled in the atlantic stratocumulus transition experiment aircraft measurements show a surface based mixed layer separated from the base of the stratocumulus by a layer that is stable to dry turbulent mixing this layer forms due to shortwave heating of the stratocumulus clouds cumulus clouds often develop in this transition layer and they play a fundamental role in the redistribution of heat in the decoupled stratcumulus capped boundary layer they are however very sensitive to small changes in the heat and moisture in the boundary layer and are generally transient features that depend directly on the surface sensible and latent heat fluxes

assessment of resolution and accuracy of the moving window cross spectral technique for monitoring crustal temporal variations using ambient seismic noise summary temporal variations in the elastic behaviour of the earth s crust can be monitored through the analysis of the earth s seismic response and its evolution with time this kind of analysis is particularly interesting when combined with the reconstruction of seismic green s functions from the cross correlation of ambient seismic noise which circumvents the limitations imposed by a dependence on the occurrence of seismic events in fact because seismic noise is recorded continuously and does not depend on earthquake sources these cross correlation functions can be considered analogously to records from continuously repeating doublet sources placed at each station and can be used to extract observations of variations in seismic velocities these variations however are typically very small of the order of 0 1 per cent such accuracy can be only achieved through the analysis of the full reconstructed waveforms including later scattered arrivals we focus on the method known as moving window cross spectral analysis that has the advantage of operating in the frequency domain where the bandwidth of coherent signal in the correlation function can be clearly defined we investigate the sensitivity of this method by applying it to microseismic noise cross correlations which have been perturbed by small synthetic velocity variations and which have been randomly contaminated we propose threshold signal to noise ratios above which these perturbations can be reliably observed such values are a proxy for cross correlation convergence and so can be used as a guideline when determining the length of microseismic noise records that are required before they can be used for monitoring with the moving window cross spectral technique

estimation of nonlinear soil behavior during the 1999 chi chi taiwan earthquake the 1999 chi chi taiwan earthquake mw 7 6 was one of the strongest earthquakes in recent years recorded by a large number of strong motion devices though only surface records are available the obtained strong motion database indicates the variety of ground responses in the near fault zones in this study accelerograms of the chi chi earthquake were simulated at rock and soil sites and models of soil behavior were constructed at seven soil sites tcu065 tcu072 tcu138 chy026 chy104 chy074 and chy015 for which parameters of the soil profiles are known down to depths of at least 70 m and at 24 other soil sites for which parameters of the soil profiles are known down to 30 40 m all the sites were located within 50 km from the fault for reconstructing stresses and strains in the soil layers we used a method similar to that developed for the estimation of soil behavior based on vertical array records as input for the soil layers acceleration time histories simulated by stochastic finite fault modelling with a prescribed slip distribution over the fault plane were taken in spite of the largeness of the earthquake s magnitude and the proximity of the studied soil sites to the fault plane the soil behavior at these sites was relatively simple i e a fairly good agreement between the spectra of the observed and simulated accelerograms and between their waveforms was obtained even in cases where a single stress strain relation was used to describe the behavior of whole soil thickness down to 70 80 m during strong motion obviously this is due to homogeneity in the characteristics of soil layers in depth at all the studied sites resonant phenomena in soil layers down to 40 60 m and nonlinearity of soil response were the main factors defining soil behavior at tcu065 tcu110 tcu115 chy101 chy036 and chy039 liquefaction phenomena occurred in the upper soil layers estimated strains achieved 0 6 0 8 at other stations maximum strains in the soil layers were as high as 0 1 0 4 according to our estimates thus valuable data on the in situ soil behavior during the chi chi earthquake was obtained similarity in the behavior of similar soils during the 1995 kobe 2000 tottori japan and chi chi taiwan earthquakes was found indicating the possibility of forecasting soil behavior in future earthquakes in the near fault zones of the three earthquakes hard type soil behavior and resonant phenomena in the upper surface layers prevail both leading to high acceleration amplitudes on the surface

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

the 2005 mw 7 6 kashmir earthquake sub pixel correlation of aster images and seismic waveforms analysis we analyze the m w 7 6 kashmir earthquake of october 8 2005 using sub pixel correlation of aster images to measure ground deformation and modeling seismic waveforms the surface rupture is continuous over a distance of 75 km and cuts across the hazara syntaxis reactivating the tanda and the muzaffarabad faults north of muzaffarabad the surface rupture coincides approximately with the mbt on the southwestern flank of the syntaxis although the two faults have opposite dip angles the rupture terminates abruptly at the hairpin turn of the mbt showing a strong structural control the fault offset is 4 m on average and peaks to 7 m northwest of muzaffarabad the rupture lasted about 25 s and propagated updip and bi laterally 2 km s with a rise time of 2 5 s the shallowness and compactness of the rupture both in time and space provide an explanation for the intensity of destructions this kind of analysis could be achieved as soon as a post earthquake image is available and would provide key information for early assessment of damages the study sheds some light on seismic hazard in the himalaya and raises concern regarding the possibility of a repetition of the 1555 event which presumably ruptured the himalayan front south of the kashmir basin and may have reached a magnitude m w 8

monitoring seismic velocity change caused by the 2011 tohoku oki earthquake using ambient noise records 1 we estimated the changes in seismic velocity in the southern tohoku district of japan during the six month period centered on the 11 march 2011 tohoku oki earthquake using scattered waves retrieved by autocorrelation of ambient seismic noise the estimated velocity decrease after the earthquake and after two large aftershocks in the study area was as great as 1 5 in the area nearest to the mainshock the velocity changes displayed gradual healing the spatial distribution of the velocity change showed a correlation with both the changes in static strain derived from gps records and the peak particle velocity experienced during the three earthquakes derived from strong motion records therefore our results show that velocity changes possibly contain information from deep in the crust bearing on coseismic stress release in addition to shallower effects due to strong ground motion

coseismic and postseismic elastic wave velocity variations caused by the 2008 iwate miyagi nairiku earthquake japan 1 we analyze coseismic and postseismic velocity variations caused by the june 13 2008 iwate miyagi nairiku earthquake mw 6 9 using passive image interferometry pii seismic noise is correlated in order to reconstruct the green s function between two sensors shear wave velocity changes are determined by relating the coda parts of the daily green s functions to a long term reference green s function our study extends from january 2008 to august 2010 and includes the correlations for 190 station pairs in three different frequency ranges from 0 125 to 1 0 hz we show that combining the 9 different component cross correlation functions stabilizes the velocity change estimation and increases analysis resolution the observed velocity change curves can be fitted by model time series consisting of a coseismic velocity drop followed by logarithmic postseismic recovery and seasonal velocity variations the coseismic velocity drops are stronger at higher frequencies and are concentrated in the southern part of the fault zone a tomography algorithm was developed to reproject the observed velocity variations of the different sensor pairs onto the single sensors the depth distribution of coseismic changes was modeled for the three stations with the largest velocity drops at two stations the coseismic velocity changes are located in the upper several hundred meters the third station shows indications for deeper changes in the order of kilometers postseismic recovery takes significantly longer than the analyzed two year period seasonal velocity variations with periods of one year are observed at all analyzed frequencies for most station pairs

constraining depth range of s wave velocity decrease after large earthquakes near parkfield california we use noise correlation and surface wave inversion to measure the s wave velocity changes at different depths near parkfield california after the 2003 san simeon and 2004 parkfield earthquakes we process continuous seismic recordings from 13 stations to obtain the noise cross correlation functions and measure the rayleigh wave phase velocity changes over six frequency bands we then invert the rayleigh wave phase velocity changes using a series of sensitivity kernels to obtain the s wave velocity changes at different depths our results indicate that the s wave velocity decreases caused by the san simeon earthquake are relatively small similar to 0 02 and access depths of at least 2 3 km the s wave velocity decreases caused by the parkfield earthquake are larger similar to 0 2 and access depths of at least 1 2 km our observations can be best explained by material damage and healing resulting mainly from the dynamic stress perturbations of the two large earthquakes

ambient noise rayleigh wave tomography of new zealand summary we present the first new zealand wide study of surface wave dispersion using ambient noise observed at 42 broad band stations in the national seismic network geonet and the global seismic network gsn year long vertical component time series recorded between 2005 april 1 and 2006 march 31 have been correlated with one another to yield estimated fundamental mode rayleigh wave green s functions we filter these green s functions to compute rayleigh wave group dispersion curves at periods of 5 50 s using a phase matched filter frequency time analysis technique the uncertainties of the measurements are estimated based on the temporal variation of the dispersion curves revealed by 12 overlapping 3 month stacks after selecting the highest quality dispersion curve measurements we compute group velocity maps from 7 to 25 s period these maps and 1 d shear wave velocity models at four selected locations exhibit clear correlations with major geological structures including the taranaki and canterbury basins the hikurangi accretionary prism and previously reported basement terrane boundaries

a process based model for colluvial soil depth and shallow landsliding using digital elevation data a model is proposed for predicting the spatial variation in colluvial soil depth the results of which are used in a separate model to examine the effects of root strength and vertically varying saturated conductivity on slope stability the soil depth model solves for the mass balance between soil production from underlying bedrock and the divergence of diffusive soil transport this model is applied using high resolution digital elevation data of a well studied site in northern california and the evolving soil depth is solved using a finite difference model under varying initial conditions the field data support an exponential decline of soil production with increasing soil depth and a diffusivity of about 50 cm 2 yr the predicted pattern of thick and thin colluvium corresponds well with field observations soil thickness on ridges rapidly obtain an equilibrium depth which suggests that detailed field observations relating soil depth to local topographic curvature could further test this model bedrock emerges where the curvature causes divergent transport to exceed the soil production rate hence the spatial pattern of bedrock outcrops places constraints on the production law the infinite slope stability model uses the predicted soil depth to estimate the effects of root cohesion and vertically varying saturated conductivity low cohesion soils overlying low conductivity bedrock are shown to be least stable the model may be most useful in analyses of slope instability associated with vegetation changes from either land use or climate change although practical applications may be limited by the need to assign values to several spatially varying parameters although both the soil depth and slope stability models offer local mechanistic predictions that can be applied to large areas representation of the finest scale valleys in the digital terrain model significantly influences local model predictions this argues for preserving fine scale topographic detail and using relatively fine grid sizes even in analyses of large catchments