late quaternary deformation of the toppenish ridge uplift in south central washington mapping of quaternary sedimentary rocks and miocene basalts on toppenish ridge a fold in south central washington reveals a 32 km long zone of nearly 100 surface ruptures the ruptures indicate renewed movement on miocene structures in latest quaternary time the ruptures probably formed in response to regional compressive stress between 500 and 13 000 yr ago these ruptures are interpreted to represent the most recent surface deformation in central washington

structural analysis and interpretation of the surface deformations of the el asnam earthquake of october 10 1980 the el asnam earthquake of october 10 1980 represents the major seismotectonic event of these last decades in the west mediterranean area it has induced a large amount of surface breaks this earthquake reveals the importance of compressional phenomena that characterize nowadays the tectonics of north africa the tectonic analysis of surface rupture shows the complexity of the deformation mechanism the principal mechanism consists of the activation of a nw se trending thrust fault accompanied with a left lateral motion and with an intense deformation of the northwestern overthrusting block an accurate description of these deformations shows that for a large part the breaks geometry depends closely on the substratum structure finally the analysis of the dislocations on irrigation ducts just above the fault traces allowed a quantitative study of the deformation

source and origin of roxana silt and middle wisconsinan midcontinent glacial activity abstract thick roxana silt middle wisconsinan in central and southwestern illinois traditionally has been interpreted as loess derived from valley train deposits in the ancient mississippi river valley winters et al h a winters j j alford and r l rieck quaternary research 29 25 35 1988 recently suggested that the roxana was not directly related to glacial activity but was derived from sediment produced by increased shoreline and spillway erosion associated with a fluctuating ancestral lake michigan because 1 paleoenvironmental and paleohydrologic conditions inferred in the hypothesis are unlikely for a loess depositional system and 2 loess did not accumulate during late wisconsinan deglaciation under conditions similar to those hypothesized we suggest the hypothesis should be rejected roxana distribution suggests the major source was drainage from the upper mississippi river valley and variations in loess thickness in illinois can be explained by consideration of valley width depth orientation and postdepositional erosion tills in the headwaters region of the ancient mississippi drainage system in minnesota and wisconsin occur in the appropriate stratigraphic position and have colors and mineralogic compositions that suggest they could be the parent till of the roxana we believe a valley train source for thick roxana is most probable and urge continued consideration of middle wisconsinan glaciation in the upper great lakes area

dynamic characteristics of a ground fissure site abstract the seismic response of an active ground fissure site was simulated by a shaking table test and a flac3d numerical simulation model coupled dynamic ground motions of earthquake and fissure activity were loaded on the model the characteristics of the fissure site that is the movement of the hidden fissure the uneven subsidence the acceleration and the lateral and vertical soil pressures were monitored and analyzed the following observations were made from this study the subsidence of the hanging wall was greater than that of the footwall the stretch caused by the uneven subsidence led to the appearance of the hidden fissure and the gradual widening of the fissure the peak acceleration in the hanging wall was larger than that of the footwall the pga increased with the height of the site the magnification coefficient of the pga had the largest value in the fissure and the magnification coefficient of the pga decreased with earthquake intensity the increments of lateral and vertical soil pressure also increased with earthquake intensity the vertical soil pressure at the location of the fissure was the largest these dynamic characteristics are vital to the safety design of underground structures in a fissure site

postseismic relaxation following the 1989 ms7 1 loma prieta earthquake central california 1 the postseismic relaxation postseismic displacement less displacement that would have occurred at the preseismic rate measured by gps and leveling following the 1989 ms7 1 loma prieta earthquake is reexamined the temporal dependence of the relaxation over the first 1200 days postseismic is well described by 1 e t where 414 92 days quoted uncertainties are standard deviations that temporal dependence appears to be a linear function of the cumulative number of m 2 5 aftershocks that have occurred the relaxation is attributed to afterslip 1 56 0 20 m dextral strike slip and 0 60 0 04 m reverse slip on the downdip extension depth 16 21 km of the coseismic rupture plus a collapse 0 11 0 02 m fault normal displacement of the rupture zone depth 5 16 km because the postseismic uplift was determined by leveling over a route with relief in excess of 1000 m an allowance 18 2 ppm of height above the base elevation for excess beyond corrections already applied height dependent error in the measured uplift was estimated simultaneously with the afterslip and collapse parameters this new solution for afterslip and collapse on the plane of the rupture provides an alternative explanation to the suggestion by burgmann et al 1997 that the postseismic deformation was due to afterslip on the coseismic rupture and on a nearby shallow 30 dipping thrust

relations between surface deformation fault geometry seismicity and rupture characteristics during the el asnam algeria earthquake of 10 october 1980 abstract the el asnam earthquake of october 10 1980 ms 7 3 produced surface faulting on a northeast trending thrust fault of 30 km length with displacements of up to 6 5 m though average displacements were about 3 m in addition widespread tensional features were formed some in clear association with folding above the thrust and others in an area beyond the exposure of the thrust at the surface which may be related to buried reverse faults the observed thrust fault is split into southern central and northern segments local and teleseismic data are examined to show that the main shock nucleated at the southwest end of the fault and propagated 12 km northeast where a second rupture of approximately equal moment occurred continuing the faulting a further 12 km northeast along the central segment both ruptures nucleated at about 8 10 km depth displacements were largest on the central segment where they were probably enlarged by aftershocks including one of mb 6 1 three hours after the main shock the northern segment was much shorter than the other two and showed smaller displacement the junctions between fault segments are marked by distinct geomorphological characteristics and a change in strike of the faulting as well as a sudden drop in the observed displacement it appears that the rupture development is influenced by the changes in fault geometry between segments and that such junctions or barriers have persisted through much of the late quaternary

paleoliquefaction study of the clarendon linden fault system western new york state abstract the lack of earthquake induced liquefaction features in late wisconsin and holocene sediments in genesee wyoming and allegany counties suggests that the clarendon linden fault system clf did not generate large moment magnitude m 6 earthquakes during the past 12 000 years given that it was the likely source of the 1929 m 4 9 attica earthquake however the clarenden linden fault system probably is capable of producing future m 5 events during this study we reviewed newspaper accounts of the 1929 attica earthquake searched for earthquake induced liquefaction features in sand and gravel pits and along tens of kilometers of river cutbanks evaluated numerous soft sediment deformation structures compiled geotechnical data and performed liquefaction potential analysis of saturated sandy sediments we found that the 1929 m 4 9 attica earthquake probably did not induce liquefaction in its epicentral area and may have been generated by the western branch of the clarendon linden fault system most soft sediment deformation structures found during reconnaissance did not resemble earthquake induced liquefaction features and even the few that did could be attributed to non seismic processes our analysis suggests that the magnitude threshold for liquefaction is between m 5 2 and 6 that a large m 6 earthquake would liquefy sediments at many sites in the area and that a moderate earthquake m 5 5 9 would liquefy sediments at some sites but perhaps not at enough sites to have been found during reconnaissance we conclude that the clarendon linden fault system could have produced small and moderate earthquakes but probably not large events during the late wisconsin and holocene

seismic response of a hill the example of tarzana california the northridge california earthquake that strongly shook the city of los angeles in january 1994 produced one of the highest ground accelerations ever recorded in an earthquake at a site located on top of a small hill in tarzana about 6 km south of the epicenter the subsequent study of aftershock recordings obtained by a dense seismic array deployed on the hill a few days after the earthquake showed the existence of a strong amplification at stations located at the top of the hill relative to stations near the base spudich et al 1996 resonances and polarization rotations were also observed we investigate in this study the role that the topography of the site played on the observed ground motions and accelerations to this aim we perform numerical simulations and study the response of the three dimensional topography of the site to incident shear waves polarized in different directions the method used is a boundary integral equation scheme in which the green s functions are calculated by the discrete wavenumber method the results obtained show that the topography of the site though quite gentle the hill is less than 20 m high strongly affects the ground motions in the frequency range between 2 and 15 hz many of the observed characteristics of the seismic response at tarzana are explained in part by its topography the consistent amplification of ground motion at and near the top of the hill the directional seismic response of the hill that results in a strong amplification of the ground motion transverse to the direction of elongation of the hill the existence of a fundamental transverse oscillatory resonance mode of the hill at 3 to 5 hz the rotation of the polarization of ground motion and the spatial variation of amplification over the hill at the fundamental resonance mode the seismic response of the topography however does not fully explain the amplitude of the effects observed the three dimensional geological structure of the site must in some way amplify the effect of the topography to produce the observed seismic response in spite of not being as strong as the observed effect the topographic effect of the site is considerable the ground motion is amplified by factors ranging from 30 to 100 at some locations in the frequency range from 2 to 15 hz rapid spatial variations of ground shaking intensities can take place over distance scales of a few tens of meters at high frequency finally the results of the simulation indicate that the topography of the site amplified the large east west accelerations recorded there during the northridge mainshock by 30 to 40

structure of the 1999 chi chi earthquake rupture and interaction of thrust faults in the active fold belt of western taiwan abstract we summarize the structural characteristics of the surface ruptures of the 1999 mw 7 6 chi chi earthquake in western taiwan and discuss the geological interaction of the chelungpu fault with adjacent faults based on geological investigations seismological analyses and gps measurements of surface co seismic displacements we describe the regional 3 d fault plane and slip distribution of the chi chi earthquake and compare these to the geological features of the chelungpu fault we find that one key feature of the chelungpu fault is the stratigraphy controlled slip surface at the level of the uppermost few kilometers the chelungpu fault slip plane generally follows the bedding plane of the pliocene chinshui shale the second key feature of the chelungpu fault is the difference in structurally geometric configuration between its northern and southern segments the northern fengyuan segment shows a bedding parallel thrust fault within east dipping strata in both footwall and hanging wall in contrast the southern tsaotun segment exhibits east dipping strata are overthrust onto flat lying recent alluvial deposits these two features not only explain a hinterland imbricate thrusting on the hanging wall of the fengyuan segment but also explain the change in strike of the chi chi surface ruptures at the northern end the southern end of the 1999 chi chi rupture is interpreted to be linked to a series of nw trending strike slip faults in particular we propose that the luliao strike slip fault served as the lateral ramp of the chelungpu fault and the gukeng strike slip fault acted as a barrier to end the southern propagation of the 1999 rupture geomorphic features and paleoseismological data indicate that the range front chelungpu fault has generated large earthquakes during the last several thousand years alternatively in the miaoli area to the north and the chiayi area to south historical earthquakes as well as active geomorphic features are not restricted on the range front thrust faults instead more complicated structures including tightly spaced folds duplex structures and strike slip faults are involved in seismogenic processes a more detailed investigation of regional structural characteristics is needed for mitigation against the seismic hazards in the 300 km long active fold belt in western taiwan where several damaging large earthquakes have been documented during the last century

paleoseismic investigations in the santa cruz mountains california implications for recurrence of large magnitude earthquakes on the san andreas fault trenching microgeomorphic mapping and tree ring analysis provide information on timing of paleoearthquakes and behavior of the san andreas fault in the santa cruz mountains at the grizzly flat site alluvial units dated at 1640 1659 a d 1679 1894 a d 1668 1893 a d and the present ground surface are displaced by a single event this was the 1906 surface rupture combined trench dates and tree ring analysis suggest that the penultimate event occurred in the mid 1600 s possibly in an interval as narrow as 1632 1659 a d there is no direct evidence in the trenches for the 1838 or 1865 earthquakes which have been proposed as occurring on this part of the fault zone in a minimum time of about 340 years only one large surface faulting event 1906 occurred at grizzly flat in contrast to previous recurrence estimates of 95 110 years for the santa cruz mountains segment comparison with dates of the penultimate san andreas earthquake at sites north of san francisco suggests that the san andreas fault between point arena and the santa cruz mountains may have failed either as a sequence of closely timed earthquakes on adjacent segments or as a single long rupture similar in length to the 1906 rupture around the mid 1600 s the 1906 coseismic geodetic slip and the late holocene geologic slip rate on the san francisco peninsula and southward are about 50 70 and 70 of their values north of san francisco respectively the slip gradient along the 1906 rupture section of the san andreas reflects partitioning of plate boundary slip onto the san gregorio sargent and other faults south of the golden gate if a mid 1600 s event ruptured the same section of the fault that failed in 1906 it supports the concept that long strike slip faults can contain master rupture segments that repeat in both length and slip distribution recognition of a persistent slip rate gradient along the northern san andreas fault and the concept of a master segment remove the requirement that lower slip sections of large events such as 1906 must fill in on a periodic basis with smaller and more frequent earthquakes

seismic activity of the san francisco bay region moment magnitude m with objective confidence level uncertainties are estimated for felt san francisco bay region earthquakes using bakun and went worth s 1997 analysis strategy for seismic intensity observations the frequency magnitude distribution is well described for m 5 5 events since 1850 by a gutenberg richter relation with a b value of 0 90 the seismic moment rate m yr since 1836 is 2 68 1018 n m yr 95 confidence range 1 29 1018 n m yr to 4 07 1018 n m yr the seismic moment rate since 1850 is nearly the same m yr in the 56 years before 1906 is about 10 times that in the 70 years after 1906 in contrast m yr since 1977 is about equal that in the 56 years before 1906 80 1 14 of the plate motion moment accumulation rate is available for release in earthquakes the historical m yr and the portion of the plate motion moment accumulation rate available for release in earthquakes are used in a seismic cycle model to estimate the rate of seismic activity in the twenty first century high and low rates of future seismic activity are both permissible given the range of possible seismic cycle recurrence times t and the uncertainties in the historical m and in the percentage of plate motion available for release in earthquakes if the historical seismic moment rate is not greater than the estimated 2 68 1018 n m yr and the percentage of the plate motion moment accumulation available for release in earthquakes is not less than the estimated 80 then for all t the rate of seismic moment release from now until the next 1906 sized shock will be comparable to the rate from 1836 to 1905 when m 6 1 2 shocks occurred every 15 to 20 years

rapid late quaternary slip repeated prehistoric earthquake rupture and widespread landsliding associated with the karakudzhur thrust central kyrgyz tien shan field studies have shown that active faulting in the sw tien shan is distributed across a series of e w reverse faults along the range fronts and within basin interiors with summed shortening rates that are consistent with gps measurements in contrast few field studies have been undertaken to determine the distribution and the average slip rates of faults in the central and eastern parts of the tien shan in this paper we use remote and field based observations to characterize the active faulting and tectonic geomorphology of the karakudzhur basin in the central tien shan of kyrgyzstan we use radiocarbon luminescence and uranium series dating to provide ages on three fluvial terraces that are vertically displaced across the basin bounding reverse fault and estimate fault slip rates using a 20 s dipping fault exposure we find that the fault has a slip rate of 2 4 5 9 mm year averaged over the holocene indicating that it accommodates a major part of the shortening measured by gps in contrast to the relatively uniform distribution of n s shortening in the sw tien shan significant shortening may instead be concentrated at present on a few active faults in the northern part of the central tien shan the fresh geomorphic expression of the karakudzhur fault suggests that it has ruptured in recent prehistory in a large magnitude mw 7 earthquake from palaeoseismic trenching we show that two significant surface rupturing earthquakes have occurred since 2 4 ka the most recent earthquake was potentially accompanied by widespread landsliding and faulting in the surrounding highlands

the 1989 loma prieta earthquake imaged from inversion of geodetic data we invert geodetic measurements of coseismic deformation from the 1989 ms7 1 loma prieta earthquake to determine the geometry of the fault and the distribution of slip on the fault plane the data include electronic distance measurements global positioning system and very long baseline interferometry vectors and elevation changes derived from spirit leveling the fault is modeled as a rectangular dislocation surface in a homogeneous elastic half space first we assume that the slip on the fault is uniform and estimate the position orientation and size of the fault plane using a nonlinear quasi newton algorithm the best fitting dislocation strikes n48 4 w and dips 76 9 sw consistent with the trend of the aftershock zone and moment tensor solutions bootstrap resampling of the data is used to graphically illustrate the uncertainty in the location of the rupture plane the 95 confidence envelope overlaps the aftershock zone arguing that there is not a significant discrepancy between the geodetic data and the aftershock locations second we estimate the slip distribution using the best fitting uniform slip fault orientation but increase the fault length to 40 km and the downdip width to 18 km the fault is divided into 162 subfaults 18 along strike and 9 along dip each subfault is allowed to have constant right lateral and reverse components of slip we then solve for the slip on each subfault that minimizes a linear combination of the norm of the weighted data residual and the roughness of the slip distribution the smoothing parameter which determines the relative weight put on fitting the data versus smoothing the slip distribution is chosen by cross validation simulations indicate that cross validation estimates of the smoothing parameter are nearly optimal the preferred slip distribution is very heterogeneous with maximum strike slip and dip slip of about 5 and 8 m respectively located roughly 10 km north of the hypocenter there is insignificant dip slip in the southeastern most part of the fault causing the rake to vary from nearly pure right lateral in the southeast to oblique right reverse in the northwest the change in rake is consistent with a uniform stress field if the fault dip increases by about 10 toward the southeast as indicated by the aftershock locations there was little slip above 4 km depth consistent with the observation that there was little if any surface rupture

aftershock slip behavior of the 1989 loma prieta california earthquake an analysis of 745 aftershocks of the m7 1 loma prieta earthquake of 17 october 1989 reveals a wide variety of focal mechanisms at the northwestern end of the aftershock zone earthquakes that apparently occurred off the main rupture plane exhibit mechanisms with predominantly reverse slip on planes nearly parallel to the san andreas fault at the southeastern end the mechanisms exhibit right lateral motion on near vertical planes suggesting that these aftershocks involve slip on the san andreas fault few of the aftershock mechanisms in the central zone resemble the main shock mechanism strike n130 degree e dip 70 degree sw rake 104 degree but instead exhibit reverse right lateral left lateral and normal motion on planes subparallel to the main shock rupture plane the dip of the aftershock zone is parallel to the main shock slip plane and includes the main shock hypocenter however the lack of agreement between the main shock and the aftershock mechanisms suggests that few of the aftershocks occurred on the main shock slip plane this behavior is consistent with observations of aftershock sequences for other dip slip events and also with studies indicating that main shock rupture zones are at all other times mostly aseismic if the stress drop for the main shock relievedmore most of the tectonic stress the mechanisms could reflect the heterogeneity of the near field stress redistribution alternatively the variety of the aftershock mechanisms may reflect deformation by block motion within a narrow zone adjacent to the main shock rupture plane less

surface displacements in the 1906 san francisco and 1989 loma prieta earthquakes the horizontal displacements accompanying the 1906 san francisco earthquake and the 1989 loma prieta earthquake are computed from geodetic survey measurements the 1906 earthquake displacement field is entirely consistent with right lateral strike slip on the san andreas fault in contrast the 1989 loma prieta earthquake exhibited subequal components of strike slip and reverse faulting this result together with other seismic and geologic data may indicate that the two earthquakes occurred on two different fault planes

discovery controls and hazards of widespread deep seated gravitational slope deformation in the etsumi mountains central japan deep seated gravitational slope deformation dsgsd is a largely unnoticed but important long term mass wasting process that may result in catastrophic failure of mountain slopes manifested by small topographic irregularities such as ridge parallel scarps and linear depressions it has been predominantly reported in alpine landscapes above timber lines on the basis of area wide high resolution topographic data acquired by light detection and ranging lidar surveys we here show that 96 of existing gravitational scarps have been hidden under forest canopies in the etsumi mountains central japan the scarps are surprisingly widespread over the mountains with a mean line density of as large as 0 87 km km2 our analyses of the scarp distribution suggest that uphill facing scarps are primary geomorphic signals of dsgsd with a destabilized rock mass larger than 105 m2 whereas downhill facing scarps principally occur in response to more localized slope deformation in terms of controls topography is by far the most influential factor in triggering and promoting dsgsd despite the m 7 5 earthquake in 1891 impact of large local earthquakes proves to be not very strong comparison with preexisting landslide maps further suggests that dsgsd and large scale landslide are not different slope processes but represent different stages of the same process our results highlight limitation of aerial photograph interpretation in forest covered mountains and the need for lidar assisted mapping for deeper understanding of this long term process and interactions between surface and tectonic processes

an idealized semi empirical framework for modeling the madden julian oscillation abstractthe authors present a simple semi empirical model to explore the hypothesis that the madden julian oscillation can be represented as a moisture mode destabilized by surface flux and cloud radiative feedbacks the model is one dimensional in longitude the vertical and meridional structure is entirely implicit the only prognostic variable is column water vapor w the zonal wind field is an instantaneous diagnostic function of the precipitation field the linearized version of the model has only westward propagating relative to the mean flow unstable modes because wind induced surface latent heat flux anomalies occur to the west of precipitation anomalies the maximum growth rate occurs at the wavelength at which the correlation between precipitation and surface latent heat flux is maximized this wavelength lies in the synoptic to planetary scale range and is proportional to the horizontal scale associated with the assumed diagnostic wind response to precipitation anomalies the nonlinear version

pre wisconsinan glacial stratigraphy chronology and paleomagnetics of west central wisconsin detailed evaluation of pedogenic geologic and paleomagnetic properties has enabled the identification of several pre wisconsinan stratigraphic units in west central wisconsin the older unit is the pierce formation consisting of the hersey member which contains gray calcareous loam textured till and the kinnickinnic member which contains rhythmically bedded lacustrine sediments deposited in a complex network of proglacial lakes paleomagnetic and pedogenic data from the pierce formation suggest that the hersey member was deposited during either the emperor reversed event or the matuyama reversed polarity epoch and that deposition of the kinnickinnic member spanned either the emperor brunhes or the matuyama brunhes boundary 460 000 or 730 000 b p during pre illinoian time the younger pre wisconsinan unit is the river falls formation which contains a reddish brown sandy clay loam textured till and associated sand and gravel soil profile development and regional correlation indicate that this unit is illinoian in age these results contradict previously published studies which suggested that tills of the hersey member and the river falls formation were deposited by the same wisconsinan ice advance and that no pre wisconsinan sediment is present in western wisconsin

eolian sand and loess deposits indicate west northwest paleowinds during the late pleistocene in western wisconsin usa our study adds to the quaternary history of eolian systems and deposits in western wisconsin usa primarily within the lower chippewa river valley thickness and textural patterns of loess deposits in the region indicate transport by west northwesterly and westerly winds loess is thickest and coarsest on the southeastern flanks of large bedrock ridges and uplands similar in some ways to shadow dunes in many areas sand was transported up and onto the western flanks of bedrock ridges as sand ramps presumably as loess was deposited in their lee long linear dunes common on the sandy lowlands of the chippewa valley also trend to the east southeast small depressional blowouts are widespread here as well and often lie immediately upwind of small parabolic dunes finally in areas where sediment was being exposed by erosion along cutbanks of the chippewa river sand appears to have been transported up and onto the terrace treads forming cliff top dunes luminescence data indicate that this activity has continued throughout the latest pleistocene and into the mid holocene together these landforms and sediments paint a picture of a locally destabilized landscape with widespread eolian activity throughout much of the postglacial period

evolution of the northern santa cruz mountains by advection of crust past a san andreas fault bend the late quaternary marine terraces near santa cruz california reflect uplift associated with the nearby restraining bend on the san andreas fault excellent correspondence of the coseismic vertical displacement field caused by the 17 october 1989 magnitude 7 1 loma prieta earthquake and the present elevations of these terraces allows calculation of maximum long term uplift rates 1 to 2 kilometers west of the san andreas fault of 0 8 millimeters per year over several million years this uplift in concert with the right lateral translation of the resulting topography and with continual attack by geomorphic processes can account for the general topography of the northern santa cruz mountains

optical ages on loess derived from outwash surfaces constrain the advance of the laurentide ice sheet out of the lake superior basin usa abstract we present textural and thickness data on loess from 125 upland sites in west central wisconsin which confirm that most of this loess was derived from the sandy outwash surfaces of the chippewa river and its tributaries which drained the chippewa lobe of the laurentide front during the wisconsin glaciation mis 2 on bedrock uplands southeast of the widest outwash surfaces in the chippewa river valley this loess attains thicknesses 5 m osl ages on this loess constrain the advance of the laurentide ice from the lake superior basin and into west central wisconsin at which time its meltwater started flowing down the chippewa drainage the oldest mar osl age 23 8 ka from basal loess on bedrock agrees with the established but otherwise weakly constrained regional glacial chronology basal ages from four other sites range from 13 2 to 18 5 ka pointing to the likelihood that these sites remained geomorphically unstable and did not accumulate loess until considerably later in the loess depositional interval other osl ages from this loess taken higher in the stratigraphic column but below the depth of pedoturbation range to nearly 13 ka suggesting that the chippewa river valley may have remained a loess source for several millennia

the recent fault scarps of the western alps france tectonic surface ruptures or gravitational sackung scarps a combined mapping geomorphic levelling and 10be dating approach abstract in the western alps some recent scarps were previously interpreted as surface ruptures of tectonic reverse and normal faults that agree with microseismicity and gps measurements our analysis shows that in fact there are hundreds of recent scarps up to 30 m high and 2 1 km long with only pure normal motions they share the same characteristics as typical sackung scarps the scarps are mainly uphill facing parallel to the ridge crests and the contour lines they are relatively short less than 2 1 km with respect to tectonic fault ruptures and organized in swarms they cut screes and relict rock glaciers with a slow commonly 1 mm year average slip rate in the aiguilles grives massif these sackung scarps clearly express the gravitational toppling of sub vertical bedding planes in hard rocks in contrast the belledonne outer crystalline massif exhibits scarps that stem from the gravitational reactivation of conjugate tectonic faults the recent faults extend to about 1600 m beneath the rognier ridge crest but are always above the valley floor the main scarp swarm is 9 2 km long and constitutes the largest sackung ever described in the western alps 10 be dating of a scarp and offset surfaces shows that 4 m slip may have occurred rapidly in less than 3800 years sometimes between the end of the glaciation and 8800 1900 years ago this dating together with the location of some faults far from the deep glacial valleys suggests that sagging might have been triggered by strong earthquakes during a post glacial period of probably enhanced seismicity the belledonne and synclinal median faults just beneath the rognier sackung could have been the sources of this seismicity

near source modeling of the loma prieta earthquake evidence for heterogeneous slip and implications for earthquake hazard i have analyzed records from 20 strong motion instruments that recorded the 1989 loma prieta earthquake ml 6 9 to determine the spatial and temporal distribution of slip using a tomographic back projection technique i find that the earthquake ruptured bilaterally at approximately 80 of the local shear wave velocity over a distance of slightly more than 30 km from 13 km northwest to 20 km southeast of the hypocenter slip within the rupture zone was highly variable both in magnitude and direction slip at the hypocenter and immediately up dip was relatively low about 1 m there were two main areas of concentrated slip one centered 7 km northwest of the hypocenter at a depth of 14 km and the other centered 6 km southeast of the hypocenter at a depth of 12 km peak slip amplitude on these high slip patches exceeded 4 5 m a surprising aspect of the rupture model is that rake varies from being predominately strike slip to the southeast of the hypocenter to being predominately reverse slip to the northwest despite this variation in rake the average rake determined from the strong motion data is in agreement with that determined teleseismically there is a correlation between areas of high slip and areas of low aftershock activity a simple model to explain this observation is that the areas of high slip are also areas of high strength which slip only during infrequent large mainshocks other areas of the fault are weaker and may slip both seismically and aseismically most of the slip in the loma prieta earthquake occurred between 9 and 16 km depth on a structure that dips to the southwest and runs underneath the surface trace of the san andreas fault at a depth of 8 to 10 km this observation complicates the assessment of seismic hazard on the southern santa cruz mountains segment of the san andreas fault

low frequency modes in an equatorial shallow water model with moisture gradients motivated by observations of the mean state of tropical precipitable water pw a moist first baroclinic mode shallow water system on an equatorial plane with a background saturation profile that depends on latitude and longitude is studied in the presence of a latitudinal moisture gradient linear analysis of the non rotating problem reveals large scale symmetric eastward and westward propagating unstable modes the introduction of a zonal moisture gradient breaks the east west symmetry of the unstable modes the effects of rotation are then included by numerically solving the resulting eigenvalue problem on an equatorial plane with a purely meridional moisture gradient the system supports large scale low frequency eastward and westward moving neutral modes some of the similarities and some of the discrepancies of these modes with intraseasonal tropical waves are pointed out finally a zonal moisture gradient in the presence of rotation renders some of the aforementioned neutral modes unstable in particular according to observations of large scale low frequency tropical variability it is seen that regions where the background saturation profile increases decreases to the east favour eastward westward moving moist modes

rupture history of the 1989 loma prieta california earthquake strong motion records of the 1989 loma prieta earthquake are inverted to determine a model of the rupture history uncorrected horizontal and vertical accelerograms are integrated to particle velocity time histories for 38 stations within an epicentral range of 75 km the time histories are bandpassed filtered with corners at 0 05 and 1 0 hz these bandpassed time histories are inverted using a nonlinear method to solve for the distribution of slip amplitudes and rupture times at specified locations on the fault plane the fault plane is specified a priori 38 km long and 17 km wide extending from 3 to 19 km depth at a constant dip of 70 starting models have rupture times based on constant rupture velocities of 2 5 2 8 and 3 0 km sec and uniform slip with rise times of 0 5 1 0 1 5 and 3 0 sec the waveform inversion results show the strike slip displacement is concentrated at the southern end of the rupture rake 156 and the dip slip displacement is concentrated at the northern end of the rupture rake 115 the average total slip is partitioned almost equally between strike slip and dip slip rake 137 the hypocentral area has an unusually small amount of slip with almost no slip in a region just to the north and up dip from the hypocenter the rupture front is complex propagating up dip to the south faster than it propagates to the north the region of maximum strike slip to the southeast radiates simultaneously with the region of maximum dip slip to the northwest the average rupture velocity is 3 0 km sec approximately 0 83 times the local shear wave speed the calculated seismic moment is 3 5 0 5 1026 dyne cm

gravity tectonics of topographic ridges halokinesis and gravitational spreading in the western ogaden ethiopia the cenozoic history of the western ogaden region of ethiopia between the ethiopian rift and the south afar margin is marked by uplift and incision of the ogaden plateau down to the gorrahei formation an upper cretaceous evaporite formation debuttressing of this and the overlying sedimentary formations resulted in widespread and spectacular gravitational spreading landforms over a minimum surface area of 15 000 km2 most of which remains unstudied after clearing up some misconceptions about the surface geology of the study area the kebenawa ridge in the audo range observations are reported that point to a tectonic style controlled by halokinesis and subsequently gravitational spreading the role of diapirism and karstification in the observed halokinesis is discussed as well as the influence of halokinesis on gravitational spreading spreading is in part akin to sackung in that ridge deformation features include a crestal graben and basal ridge topography extrusion and deformation was triggered by lateral ridge debuttressing ridge spreading also presents analogy with gravitational spreading of the canyonlands grabens in the needles district canyonlands national park utah the scale and the mechanisms are found to be basically similar but two differences are noted first incision by the drainage network in response to plateau uplift in ethiopia has debuttressed the topography along two parallel rivers instead of a single river the colorado river in utah secondly incision proceeded to the base of the evaporite layer in the ogaden whereas incision has not exceeded the top of the evaporite layer in utah these differences may have influenced the details of the spreading mechanisms in ways that remain to be investigated overall in ethiopia association of halokinesis and a transitional mode of gravitational spreading at the interface between narrow ridge spreading sackung and plateau spreading canyonlands type illustrates a fascinating and unusual ridge evolution style

an experimental approach for estimating seismic amplification effects at the top of a ridge and the implication for ground motion predictions the case of narni central italy abstract from march to september 2009 a velocimetric network was installed in narni central italy a village on the top of a limestone ridge the aim was to investigate local site effects due to the 220 m high ridge which is characterized by slopes ranging from 22 to 35 to investigate amplification without and with a reference site three stations were installed at the base of the hill and seven at the crest the network recorded 702 earthquakes many of them from the 2009 l aquila sequence to determine the dependence of amplification on the morphological features the spectra were computed for horizontal components rotated into a range of azimuths both the ratio of the horizontal to vertical component spectra and the ratio of the spectra at the ridge crest with respect to a reference station at the base of the ridge showed amplification by a factor of circa 4 5 for frequencies between 4 hz and 5 hz the highest amplifications were seen for the directions of the ground motion perpendicular to the main elongation of the ridge finally considering events with an epicentral distance less than 30 km empirical ground motion models were calibrated for maximum horizontal peak ground acceleration pga velocity and acceleration response spectra 5 damping up to 1 s to estimate the site corrective coefficients for topographic amplification the data show corrective coefficients between 0 35 and 0 48 log 10 scale amplification 2 2 3 0 for the spectral ordinates between 0 2 s and 0 3 s

longitudinal localization of tropical intraseasonal variability intraseasonal time scales play an important role in tropical variability two modes that contribute significantly to tropical intraseasonal variability isv are the eastward propagating maddenjulian oscillation mjo and westward moving moist equatorial rossby waves this note reports on a correspondence between the longitudinal gradient of mean tropical precipitable water pw and the geographical regions of genesis and convective activity of both these large scale tropical systems our finding is based on an analysis of pw from the merra reanalysis product the data indicate that the mean tropical pw has a dominant wavenumber two three structure in longitude in the northern southern hemisphere departures from a longitudinally homogeneous state are attributed to the influence of subtropical anticyclones and are accentuated by monsoonal regions of both hemispheres this mean structure results in a sharply localized longitudinal gradient of pw remarkably regions with positive gradients such as the northern and southern hemisphere western indian ocean i e they have larger pw to the east are the very zones that are implicated in the formation and show high levels of convective activity of the eastward moving mjo on the other hand regions with negative gradients such as the southern hemisphere central pacific are the very regions where genesis and maxima in variance of westward moving moist equatorial rossby waves are known to occur apart from providing a first order longitudinal footprint of the convective phase of these systems this correspondence reinforces the role of the mean climatic state in tropical isv copyright c 2012 royal meteorological society

fault geometries and structures associated with the rupture endpoints of the 2008 mw 7 9 wenchuan earthquake eastern tibet plateau china

geodetic estimate of coseismic slip during the 1989 loma prieta california earthquake offsets in the relative positions of geodetic stations resulting from the loma prieta earthquake can be explained with a dislocation model that includes buried oblique slip on a rupture surface extending 37 km along the strike of the san andreas fault dipping 70 degree to the sw and extending from a depth of about 5 to 17 5 km assuming uniform slip on a rectangular surface the mean values for a range of reasonable fault geometries are 1 6 plus minus 0 3 m right lateral strike slip and 1 2 plus minus 0 3 m reverse slip slip on an adjacent extension of the rupture to the southeast recorded in the aftershock sequence is not well constrained by the geodetic data the geodetic data clearly preclude rupture extending near the surface

faulting geometry and slip from co seismic elevation changes the 18 october 1989 loma prieta california earthquake abstract leveling surveys conducted before and after the loma prieta earthquake provide observations of the co seismic elevation changes these data are used to determine the faulting geometry and distribution of slip considering planar listric and negatively listric fault shapes both the planar and nonplanar models produce elevation changes consistent with the observations most of the observed elevation changes can be modeled with a rupture surface that extends from 4 to 15 km depth if the rupture surface is planar the observations require 2 4 m of right lateral strike slip and 1 7 m of reverse slip on a 34 km long plane that dips 60 sw the best fitting model faults lie above and to the southwest of the aftershock zone a significantly better fit to the observations is obtained when these fault geometries are allowed to have two rake values with a larger thrust component northwest of the epicenter and a larger strike slip component southeast of the epicenter when a low modulus layer over a half space is used for consistency with the seismic p wave velocity structure the fault deepens coming within 3 km of the hypocenter but still locates several kilometers southwest of most aftershocks

re evaluation of 1906 surface faulting geomorphic expression and seismic hazard along the san andreas fault in the southern santa cruz mountains the lack of through going right lateral surface rupture accompanying the loma prieta earthquake has raised questions about the behavior of the san andreas fault in the southern santa cruz mountains we re evaluated previously published reports of ground deformation due to the 1906 earthquake in this region to determine if san andreas fault surface rupture accompanied this event and whether any of the reported values of offset are reliable in addition our search for historical data has brought to light new information about the 1906 earthquake in the southern santa cruz mountains none of the reports provides indisputable evidence for 1906 san andreas fault surface rupture however taken together with a study of the geomorphology of the fault zone and relationships exposed in excavations across the fault they do provide a basis for believing that surface rupture extended through the region in 1906 none of the reported values for 1906 offset is a reliable measurement however calling into question current and pre 1989 seismic hazard assessments for the loma prieta area the geologic and geomorphic relationships indicate that shallow right lateral crustal strain is typically expressed as surface rupture across a narrow san andreas fault zone in contrast to the 1989 loma prieta earthquake

10be ages reveal 12 ka of gravitational movement in a major sackung of the western alps france abstract the rognier sackung which extends ne sw for more than 9 km is a major gravitational morpho structure located in the western alps we used the 10 be cosmic ray exposure dating method on 23 samples to unravel its history and better understand its genetic mechanism we found that the average slip rate on sackung faults varies from 0 3 to 3 2 mm yr 1 conjugate sackung faults are contemporaneous in agreement with a model in which the whole mountain ridge is involved in the gravitational deformation 600 m thick multiple samples on single faults suggest that the development of this sackung started before 12 ka and that it is still active we cannot exclude the possibility that the dissolution of the underlying triassic evaporites participated in the sagging of mt rognier however the age of this sackung and the presence of the lauziere sackung on the other side of the arcs valley support glacial erosion and debuttressing following the retreat of the valley glacier as the main causes of these large gravitational structures the long and permanent activity of the rognier sackung contrasts with that of the neighbouring arcs sackung which we previously dated using the same method and showed that it is a result of flexural toppling along with the proximity of the rognier sackung to the belledonne border active fault its long history suggests that earthquake shaking contributed to maintain its activity additionally two ages confirm that in the western alps rock glaciers formed mainly during the younger dryas this study allowed the determination of the best sampling strategy for future cre dating of these types of gravitational structures

resolution of fault slip along the 470 km long rupture of the great 1906 san francisco earthquake and its implications data from all available triangulation networks affected by the 1906 earthquake have been combined to assess the trade off between slip resolution and its uncertainty and to construct a conservative image of coseismic slip along the rupture because of varying network aperture and station density slip resolution is very uneven although slip is determined within uncertainties of 1 0 m along 60 of the fault constraints are poor on the remaining mostly offshore portions of the rupture slip decreases from maxima of 8 6 and 7 5 m at shelter cove and tomales bay to 4 5 m near mount tamalpais and 2 7 m at loma prieta the geodetically derived slip distribution is in poor agreement with estimates based on analysis of s wave seismograms probably because these waves register only 20 30 of the total seismic moment obtained from longer period surface waves consideration of a range of fault geometries for 1906 slip near loma prieta indicates right lateral motions lie between 2 3 and 3 1 m these values are considerably greater than the 1 5 m of measured surface slip on which several assessments of high earthquake hazard for this fault segment were based this factor along with the absence of 1989 slippage where 1906 surface slip was used to make the forecasts casts doubt on some claims of success in predicting the 1989 m 6 9 loma prieta earthquake

autogenic incision and terrace formation resulting from abrupt late glacial base level fall lower chippewa river wisconsin usa abstract a paucity of research exists regarding the millennial scale response of inland alluvial streams to abrupt base level fall studies of modern systems indicate that over short time scales the response is a diffusion like process of upstream propagating incision in contrast evidence from the lower chippewa river lcr located in the upper midwest of the usa suggests that autogenic controls operating over time scales of several millennia can overwhelm diffusion resulting in incision that is prolonged and episodic during the last glacial maximum the lcr drained the chippewa lobe of the laurentide ice sheet to the glacial upper mississippi river umr as a meltwater stream it aggraded and filled its valley with glacial outwash as did its largest tributaries which were also meltwater streams its nonglacial tributaries aggraded too filling their valleys with locally derived sediment during deglaciation the umr incised at least twice abruptly lowering the lcr s base level 15 m at 16 ka or earlier and an additional 40 m at ca 13 4 ka each of these base level falls initiated incision of the lcr led by upstream migrating knickpoints the propagation of incision has however been a lengthy process the optically stimulated luminescence osl ages of terrace alluvium indicate that by 13 5 ka incision had advanced up the lcr only 15 km and by 9 ka only 55 km the process has also been episodic resulting in the formation of fill cut terraces inferred from gpr surveys and exposures of terrace alluvium that are younger and more numerous in the upstream direction autogenic increases in sediment load and autogenic bed armoring the result of periodic tributary stream rejuvenation and preferential winnowing of fines by the incising river may have periodically caused knickpoint migration and incision to slow and possibly stop allowing lateral erosion and floodplain formation to dominate a decline in sediment flux from stabilizing incised tributary stream systems would have led to renewed knickpoint migration and incision when floods of sufficient magnitude to breach the channel armor occurred minimal floodplain development along the upper section of the present day lcr along with the channel morphology of an unstable wandering gravel bed river immediately downstream from it suggest that the river is still responding to the base level falls that happened many millennia ago the autogenic controls on the lcr s response to umr incision are a direct consequence of the thick fills of noncohesive sediment that accumulated in its valley and the valleys of its tributary streams during the late wisconsinan making the lcr a prime example of a former proglacial river that remains a paraglacial fluvial system

on large scale circulations in convecting atmospheres the dominant thinking about the interaction between large scale atmospheric circulations and moist convection holds that convection acts as a heat source for the large scale circulations while the latter supply water vapour to the convection we show that this idea has led to fundamental misconceptions about this interaction and offer an alternative paradigm based on the idea that convection is nearly in statistical equilibrium with its environment according to the alternative paradigm the vertical temperature profile itself rather than the heating is controlled by the convection which ties the temperature directly to the subcloud layer entropy the understanding of large scale circulations in convecting atmospheres can therefore be regarded as a problem of understanding the distribution in space and time of the subcloud layer entropy we show that the subcloud layer entropy is controlled by the sea surface temperature the surface wind speed and the large scale vertical velocity in the convecting layer and demonstrate how the recognition of this control leads to a simple physically consistent view of large scale flows ranging from the hadley and walker circulations to the 30 50 day oscillation in particular we argue that the direct effect of convection on large scale circulations is to reduce by roughly an order of magnitude the effective static stability felt by such circulations and to damp all of them

a climatology of waves in the equatorial region abstract propagating anomalies of moisture and moist deep convection in the tropics are organized into a variety of large scale modes these include but are not limited to the so called intraseasonal oscillations convectively coupled waves similar to those predicted by shallow water theory on the equatorial beta plane and tropical depression type disturbances along with the annual and diurnal cycles these modes act and interact to control much of the variance of tropical convection analyses of 10 yr of outgoing longwave radiation olr and precipitable water pw data are carried out to develop comparative climatologies of these wavelike modes the analysis relaxes the commonly used cross equatorial symmetry constraints which allows study of the portions of the wavelike processes that are asymmetric across the equator mean background states are found for olr and for pw as functions of day of the year examination of anomalies together with the background reveals much about how the waves are affec

initial investigation of site and topographic effects at robinwood ridge california abstract following the 1989 loma prieta earthquake a dense array of seven digitally recorded three component seismograph stations was deployed on robinwood ridge 7 3 km northwest of the epicenter the purpose of this array was to investigate the cause of high levels of structural damage and ground cracking observed on the ridge crest aftershocks recorded by the array allow a comparison of ground motion up the slope of the ridge from the base to the crest the data present an extremely complicated pattern of ground motion that demonstrates the importance of the three dimensionality of the problem slowness analysis of p wave trains show initial arrivals propagating away from the source with small angles of incidence and large apparent velocities consistent with direct arrivals after 0 5 sec propagation azimuths become more random and apparent velocities drop indicating nearly horizontal wave propagation and multiply reflected and diffracted phases within the ridge slowness analysis and particle motion diagrams of horizontal components of motion show dramatic variations in ground motion with changes in azimuth of the source and a complicated interaction between body waves and rayleigh and love waves results suggest that the larger amplitude more coherent arrivals at the array stations favor a propagation direction parallel to the ridge axis an amplification factor of from 1 5 to 4 5 is seen for frequencies from 1 0 to 3 0 hz with wavelengths comparable to the base of the ridge part of which may be caused by local site effects and part by topographic amplification in addition amplifications of up to a factor of 5 are seen at higher frequencies and are attributed to local site effects these effects are most notable from 4 to 8 hz on the vertical components and from 6 to 9 hz on the horizontal components the entire robinwood ridge area may also have been situated in a region of heightened mainshock ground motion due to source directivity and radiation pattern effects

the october 17 1989 loma prieta california earthquake and its aftershocks geometry of the sequence from high resolution locations hypocenters of the loma prieta sequence form a dipping zone that rises from the mainshock hypocenter and is parallel to the mainshock nodal plane most aftershocks cluster around the perimeter of the zone surrounding a relatively aseismic center which approximates the region of mainshock rupture at its southeastern end the dipping aftershock zone warps into a vertical surface that corresponds to the san andreas fault in the central and northwestern parts of the zone at depths above 10 km the aftershocks define numerous disjoint fault structures the large component of reverse slip observed in this event agrees with a simple model for slip on a dipping plane within a compressional fault bend we do not believe that the loma prieta earthquake occurred on the sargent fault however we are unable to conclude whether it ruptured the principal plate boundary fault or a less frequently active fault

topographic effects on the hill of nocera umbra central italy summary during the m w 5 7 and 6 0 umbria marche earthquakes of 1997 september 26 the historical centre of nocera umbra suffered mcs intensity vii viii the zone is located on the top of a hill a condition potentially favourable to ground motion amplification however also vulnerability is higher on the hill because of the ancient age of buildings a temporary array of eight seismological stations was installed across the hill to quantify the amplification effect due to topography waveforms of 14 aftershocks 2 6 m l 4 1 are selected for the analysis during each earthquake the largest amplitudes are observed on the hilltop spectral ratios are computed using rotated horizontal components to search for directional effects amplifications are found in two separate frequency bands one in the range 2 4 hz where the increase of amplitude is moderate never exceeding a factor of 4 and the polarization is transversal to the hill major axis the second above 10 hz where amplifications are larger and reach values as high as 25 hz high frequency polarization varies for different sites and frequencies suggesting that smaller scale complexities control the high frequency response synthetic seismograms of 2 d models confirm the occurrence of amplification although not all details are fit by numerical simulations and the agreement between observations and models is significant only in terms of the fundamental resonance frequency around 3 hz in the models amplifications are much smaller than the observed ones we conclude that topography could have been responsible for a small increase of damage in the hill zone but the most significant role on damage was played by the locally higher vulnerability

differentiating between gravitational and tectonic faults by means of geomorphological mapping trenching and geophysical surveys the case of the zenzano fault iberian chain n spain abstract the zenzano fault scarp has been developed on the top of a 475 m high erosional escarpment underlain by an upper brittle sequence and a lower halite bearing evaporitic formation the 1850 m long fault with a maximum displacement of 45 m and parallel to the escarpment has offset the back of a dip slope generating an antislope scarp with prominent triangular facets up to 38 m high and obstructing consequent transverse drainages defeated streams both gravitational and tectonic interpretations were previously proposed for this active surface rupture the fault scarp has been investigated by detailed geological and geomorphological mapping geophysical surveys gpr and ert and two trenches excavated across the fault in disrupted drainages the geophysical profiles clearly imaged the fault helping to site the trenches and roughly estimate the thickness of the deposits accumulated in the downthrown block although the maximum displacement to length ratio dmax l of the fault fall within the range of tectonic faults of similar length according to the world database the geological and geomorphological context together with several parameters reveal that this structure corresponds to a gravitational failure 1 anomalously high vertical displacement per event 1 4 m 2 high apparent vertical slip rate 0 6 mm year and 3 short recurrence interval of faulting events the negligible horizontal displacement component on the dip slip fault as well as the presence of very large caprock collapse sinkholes and saline springs strongly suggest that interstratal karstification of the halite bearing evaporites has played a primary role in the development of the gravitational failure the formation of this morphostructure has been favoured by pre existing tectonic faults erosional unloading related to the removal of an overburden ca 800 m thick and enhanced groundwater recharge due to the blockage of the drainage this work illustrates that the proposed multidisciplinary approach allows the identification of features and calculation of parameters that may help to elucidate whether an active failure has a gravitational or a tectonic origin

convectively coupled equatorial waves 1 convectively coupled equatorial waves ccews control a substantial fraction of tropical rainfall variability their horizontal structures and dispersion characteristics correspond to matsuno s 1966 solutions of the shallow water equations on an equatorial beta plane namely kelvin equatorial rossby mixed rossby gravity and inertio gravity waves because of moist processes the tilted vertical structures of ccews are complex and their scales do not correspond to that expected from the linear theory of dry waves the dynamical structures and cloud morphology of ccews display a large degree of self similarity over a surprisingly wide range of scales with shallow convection at their leading edge followed by deep convection and then stratiform precipitation mirroring that of individual mesoscale convective complexes ccews have broad impacts within the tropics and their simulation in general circulation models is still problematic although progress has been made using simpler models a complete understanding of ccews remains a challenge in tropical meteorology

are sackungen diagnostic features of de glaciated mountains abstract deep seated gravitational slope deformations dsgsds with characteristic sackung landforms e g double crests trenches uphill facing scarps and toe bulging are considered by some researchers to be diagnostic features indicating past mountain glaciations however an extensive literature review on sackung features throughout the world reveals that in some regions paraglacial processes are not the causes of such phenomena sackungen occur across a diverse spectrum of mountain types with different morphoclimatic histories including regions that have never experienced glaciation to reinforce that sackungen may originate independently of glaciation we also include two case studies from the western carpathians czech republic and slovakia which are supported by detailed geomorphic mapping trenching and absolute dating 10 be 14 c and osl on the ond ejnik ridge outer western carpathians czech republic sackungen occur in the mid holocene in the medium high mountains which are beyond the pleistocene glacial limits on the salatin mt tatra mts slovakia the sackungen which occur in formerly glaciated terrain date between 7 5 and 4 2 ka bp representing a 4 ka time lag after the disappearance of glaciers this suggests that the direct link between the ice retreat and the onset of sackung formation is not obvious even in the case of the once glaciated mountain range although paraglacial stress release is undoubtedly one of the crucial causes of sackung genesis in many mountain regions it is not the only important mechanism therefore despite occurring in numerous de glaciated mountains sackung features cannot be considered as proof of past mountain glaciations e g during analysis of extra terrestrial settings

role of the atmospheric mean state on the initiation of the madden julian oscillation in a tropical channel model tropical channel models defined as models that are global in the zonal direction but bounded in the meridional direction are particularly useful for simulating the madden julian oscillation mjo and understanding its physical and dynamical basis influences from the extratropics through the lateral boundaries have been found to be essential to the reproduction of the initiation of certain mjo events this led to a hypothesis that multi year simulations using a tropical channel model would reproduce reasonable mjo statistics under the influence of prescribed lateral boundary conditions derived from global reanalyses interestingly the mjo statistics in such a multi year simulation by a high resolution tropical channel model are not better than those from global climate models the error in the atmospheric mean state is found to be a possible reason for the poor mjo statistics in the simulation nevertheless even with a large error in the mean state the multi year simulation captures two mjo events previously found to be initiated by extratropical influences however the model does not reproduce a third event whose initiation is not directly influenced by the extratropics this implies that in the absence of dynamical interactions between the mjo and the lateral boundary conditions the error in the mean state could be sufficient to prevent the mjo initiation to explore this third mjo event further a series of sensitivity tests are conducted these tests show that the simulation of this event is neither critically influenced by the cumulus parameterization employed nor the initial conditions when the model is integrated 2 weeks prior to the mjo initiation the model captures this event when the mjo signal is already present in the initial conditions the use of high resolution sea surface temperature does not improve the simulation of the third mjo event a higher resolution nested domain covering the indo pacific warm pool region and including a cloud system resolving domain over the indonesian maritime continent has little effect on the mjo initiation over the indian ocean in 2 weeks the error in the simulation is comparable to the climate error the role of the simulated mjo on the mean state is also explored implications and limitations of these results are discussed

off fault ground ruptures in the santa cruz mountains california ridge top spreading versus tectonic extension during the 1989 loma prieta earthquake the ms 7 1 loma prieta earthquake of 18 october 1989 produced abundant ground ruptures in an 8 by 4 km area along summit road and skyland ridge in the santa cruz mountains predominantly extensional fissures formed a left stepping crudely en echelon pattern along ridges of the hanging wall block southwest of the san andreas fault about 12 km northwest of the epicenter the fissures are subparallel to the san andreas fault and appear to be controlled by bedding planes faults joints and other weak zones in the underlying tertiary sedimentary strata of the hanging wall block the pattern of extensional fissures is generally consistent with tectonic extension across the crest of the uplifted hanging wall block also many displacements in laurel creek canyon and along the san andreas and sargent faults are consistent with right lateral reverse faulting inferred for the mainshock additional small tensile failures along the axis of the laurel anticline may reflect growth of the fold during deep seated compression however the larger ridge top fissures commonly have displacements that are parallel to the north northeast regional slope directions and appear inconsistent with east northeast extension expected from this earthquake measured cumulative displacements across the ridge crests are at least 35 times larger than that predicted by the geodetically determined surface deformation these fissures also occur in association with ubiquitous landslide complexes that were reactivated by the earthquake to produce the largest concentration of co seismic slope failures in the epicentral region the anomalously large displacements and the apparent slope control of the geometry and displacement of many co seismic surface ruptures lead us to conclude that gravity is an important driving force in the formation of the ridge top fissures shaking induced gravitational spreading of ridges and downslope movement may account for 90 or more of the observed displacements on the linear fissures similar fissures occurred in the same area and elsewhere near the san andreas fault during the predominantly right lateral 1906 san francisco earthquake and suggest that the loma prieta ground ruptures may in large part be independent of fault kinematics

elastic stress relaxation a mechanism for opposite sense of secondary faulting with respect to a major fault abstract the motion along a major fault perturbs the local stress field and produces numerous secondary fractures among these the secondary fractures that have the opposite sense of motion with respect to the main fault are particularly intriguing for example the right lateral reverse motion of the ms 7 1 loma prieta earthquake of 18 october 1989 produced a series of left lateral normal fractures located in a narrow zone about 1 km in widt subparallel to the trace of the san andreas fault through a rigorous inversion of geodetic data associated with the earthquake that allowed the slip to vary on the rupture surface we studied the origin of the left lateral normal fractures by comparing the location orientation and slip sense of the observed fractures with the perturbed elastic stress field calculated from the estimated slip distribution of the earthquake the perturbed state of stress at the earth s surface is complex and the greatest principal stress changes from horizontal to vertical the area of left lateral tensile state of stress coincides with that of the observed left lateral normal fractures the magnitudes of the induced fault normal tensile stresses of 60 120 bars and left lateral fault parallel shear stresses of 0 4 bars in the area are large enough to produce the ground failures thus the observed left lateral normal fractures adjacent to the san andreas fault are interpreted to be related to coseismic elastic stress relaxation the same mechanism can also be used to explain the normal faulting in the upthrown blocks of the thrust faults which produced the 1980 el asnam algeria and the 1968 tokachi oki japan earthquakes

characteristics and mechanism of the longyao ground fissure on north china plain china abstract among more than 1000 ground fissures developed over the past 30 years having induced severe geohazards in the north china plain the longyao ground fissure in hebei province is famous for its longest length and causing the worst damage and widest influence in this region in order to reveal the origin of its formation the geological background developmental characteristics and genetic mode of the longyao ground fissure were investigated in detail by geological surveys measurements trenching drilling and seismic exploration this fissure has a total length of 39 km and is characterized by normal fault extension left lateral slip and dominant along polyline distribution these characteristics are well consistent with its underlying fault the nei jv fault the fissure causes the damage to buildings structures along a polyline and in the form of a horizontal tensile crack subsidence and shear failure according to the trenching drilling and shallow seismic profiling this fissure possesses the characteristics of synsedimentary faults reflecting the historical stages of fissure activities regarding its genesis this fissure was generated under the coupling action of multiple factors which took shape after the earthquake and was enlarged under the action of groundwater pumping the regional extension first caused a fracture system in the surface strata and then the action of seismic activities started to control the fracture and finally the pumping action of excessive groundwater and other influential factors promoted the formation of the current ground fissure

coseismic deformation of the wrights tunnel during the 1906 san francisco earthquake a key to understanding 1906 fault slip and 1989 surface ruptures in the southern santa cruz mountains california the wrights tunnel is an abandoned railroad tunnel that crosses the san andreas fault in the southern santa cruz mountains in the vicinity of the 1989 loma prieta earthquake the tunnel was damaged and deformed during the 1906 san francisco earthquake and a plot showing postearthquake measurements made in the tunnel is given by lawson 1908 the amount of offset shown on this plot 1 5 m has been used in several studies as being representative of the amount of fault offset along this segment of the san andreas fault in 1906 our historical research shows that different observers reported different amounts of fault offset in the tunnel and that the 1 5 m given on the plot is not a surveyed measurement in addition the plot of the tunnel has been interpreted in several previous studies as evidence of a broad 1 5 km zone of faulting beneath summit ridge our analysis shows that this plot need not indicate a broad zone of deformation our historical research and modeling of the tunnel measurements indicate that faulting was confined to a zone less than 400 m wide and that 60 85 of the coseismic slip occurred across a single fault plane there is no evidence for offset across a second shear zone beneath summit ridge in 1906 this implies that surface fractures reported on summit ridge in 1906 were not associated with significant deformation of the tunnel implying that they were shallow surficial features by analogy the very similar fractures that occurred on summit ridge in 1989 were also probably the result of shallow gravitational rather than deep seated tectonic processes our modeling also indicates that total coseismic near surface slip across the san andreas fault zone in the wrights tunnel in 1906 was at least 1 7 1 8 m

near fault measurement of postseismic slip associated with the 1989 loma prieta california earthquake five small aperture 0 5 to 7 7 m quadrilaterals were installed across the san andreas fault and newly formed extensional cracks shortly after the october 17 1989 loma prieta m7 1 earthquake two quadrilaterals were installed across the san andreas fault near the southeast and northwest ends of the 1989 rupture and three were installed across dominantly extensional cracks in the summit road area near the main shock epicenter and off the san andreas fault measurements of line length changes from as early as 4 d up to 184 d after the earthquake in the nail quadrilaterals indicate a small amount of right lateral postseismic slip on the san andreas fault the site near the southeast end of the 1989 afterstock zone on the san andreas fault showed about 5 2 mm of postseismic right lateral component of slip in addition to 23 mm of right lateral coseismic movement the site near the northwest end of aftershocks likewise showed about 5 2 mm of postseismic slip but after only 5 mm of coseismic slip measurements at sites across extensional cracks indicate possible minor left lateral postseismic slips and possible extensional contractional motion no measurements were made of possible vertical movements sites on extensional cracks showed similarly small amounts of possible postscismic lateral slip from 2 to 10 mm even though coseismic lateral slips were much greater up to 410 mm than on the surface trace of the san andreas fault the small slip values in spite of uncertainties clearly show that the lack of coseismic surface slip associated with the earthquake was not followed by large postseismic slip

synchronized gravitational slope deformation and active faulting a case study on and around the neodani fault central japan abstract earthquakes are considered to be important triggers of deep seated gravitational slope deformation dgsd in seismically active regions and if that is the case dgsd features could be candidates for off fault paleoseismology investigations on the basis of pit excavations and sediment cores at an off fault dgsd site and a trench excavation across the active neodani fault at a nearby site we examined the records of dgsd and surface rupturing paleoearthquakes of the neodani fault the four most recent dgsd events were dated at after 240 cal bp 1710 340 cal bp 4730 3970 cal bp and 5570 5340 cal bp the four most recent surface rupturing earthquakes were dated at 1891 ce the nobi earthquake 2010 1220 cal bp 7180 2110 cal bp and before 9540 cal bp we conclude that the ages of the four dgsd events are consistent with surface rupturing earthquakes on the adjacent neodani fault we infer that static crustal strain from repeated seismogenic faulting plays an important role in the occurrence of dgsd events at least in the immediate vicinity of active faults although coseismic severe shaking would have at least some effect on them our case study suggests that off fault dgsds can be used to reconstruct or refine the paleoseismic history of a nearby active fault we propose that an ideal dgsd for that purpose would be located in an area of concentrated strain near a termination bend or stepover of the target fault

surface rupture at a fault bend the 28 june 1992 landers california earthquake mapping of surface rupture associated with the 28 june 1992 landers earthquake along a portion of the north central emerson fault permits us to characterize the fractures and to interpret them in terms of a contractional bend in the fault trace the main rupture exhibits right lateral and reverse slip and is localized in a zone about 50 m wide along the present day trace of the emerson fault the surface deformation within its northeastern block the hanging wall is accommodated by a dome structure about 2 km long and 0 5 km wide and a complex assemblage of fractures the complexity of the fracture pattern around the fault bend results in part from 1 interaction between the main rupture and many shorter subparallel faults 2 the initiation and propagation of fractures at geometric complexities such as fault segment tips and fault bends and 3 bedding plane faulting both geological data and rupture kinematics indicate that uplift and shortening are associated with the fault bend the state of stress around the emerson fault bend is determined for co seismic conditions fault slip boundary conditions and interseismic conditions the remote applied stress and frictional fault boundary conditions using both displacement discontinuity boundary element and dislocation methods respectively we also investigate a possible fault propagation path at an idealized bend using the maximum distortional strain energy density criterion results of the theoretical analyses provide support for an understanding of the location and the asymmetry of the dome structure and the mechanisms for some of the observed fracture systems in terms of the state of stress and fault propagation paths around the fault bend and other smaller scale complexities along the fault trace

formation of left lateral fractures within the summit ridge shear zone 1989 loma prieta california earthquake the 1989 loma prieta california earthquake is characterized by the lack of major throughgoing coseismic right lateral faulting along strands of the san andreas fault zone in the epicentral area instead throughout the summit ridge area there are zones of tension cracks and left lateral fracture zones oriented about n45 w that is roughly parallel to the san andreas fault in this area the left lateral fractures zones are enigmatic because their left lateral slip is opposite to the right lateral sense of the relative motion between the pacific and north american plates we suggest that the enigmatic fractures can be understood if we assume that coseismic deformation was by right lateral shear across a broad zone about 0 5 km wide and 4 km long beneath summit ridge the shear zone has an orientation of about n70 w and is oblique to the san andreas fault zone which has a trend of n45 to 50 w so that right lateral shearing along with some dilation can account for the orientation of the fracture zones using an analog kinematic model of the summit ridge shear zone and the observable geometric parameters a shear zone about 0 5 km wide an acute angle of 25 between the tension cracks and the shear zone walls left lateral slip of 5 cm and spacing of about 100 m in the tension cracks we estimate that the amount of right lateral shift across the summit ridge shear zone was on the order of 1 4 m this is comparable to the amount of slip for coseismic faulting at depth 1 9 to 2 4 m as computed by several investigators thus contrary to most previous reports on the loma prieta earthquake which assert that coseismic right lateral ground rupture was restricted to considerable greater than 4 km depths in the epicentral area we find that nearly all the right lateral offset is represented at the ground surface by the summit ridge shear zone

long term seismic potential of the san andreas fault southeast of san francisco california the long term decade or longer seismic potential of the peninsular san andreas fault the 125 km long segment southeast of san francisco has been assessed by comparing the slip accompanying the 1906 mw 7 7 earthquake with the amount of this slip deficit made up since 1906 of particular importance is the longstanding factor of 2 inconsistency between 1906 surface offsets 1 5 m and geodetically determined coseismic slip 2 7 m on the southern 90 km of the peninsular san andreas in reexamining this issue we find that the discrepancy cannot be attributed to either large observational uncertainties in the geodetic data or shortcomings in fault modeling rather the problem lies in the complexity of this 90 km long fault reach where the san andreas trend changes by 6 the zone of recent deformation is 0 5 2 km wide and much of the fault is heavily vegetated and inaccessible farther northwest on the 1906 rupture where the fault geometry is much simpler evidence from deformed fences shows that right lateral coseismic slip was commonly distributed across a zone 20 600 m wide with only about 70 of the total slip occurring at the main fault trace the general importance of distributed coseismic deformation and the evidence for fault zone complexity indicate that the best estimate of 1906 slip on this 90 km fault segment is the geodetically constrained value of 2 6 0 2 m farther northwest on the peninsular san andreas the coseismic slip ranges from 3 4 to 4 4 m and geodetic slip and surface offsets show considerably better agreement following previous work we have assessed the risk posed to the southern peninsular san andreas by two broad classes of earthquakes these appraisals use the geodetic slip distribution apply a long term slip rate of 15 mm yr suggested by geologic and geodetic studies and assume the approximate correctness of the time predictable recurrence model the possibility of an m 6 1 2 earthquake on the 30 km long segment northwest of san juan bautista cannot be completely precluded but the evidence bearing on its likelihood is contradictory in contrast with several previous assessments we find that the risk of an earthquake of m 7 rupturing the southern 90 km of the peninsular san andreas during the next several decades is quite low

clouds associated with the madden julian oscillation a new perspective from cloudsat abstractthe evolution of total cloud cover and cloud types is composited across the madden julian oscillation mjo using cloudsat data for june 2006 may 2010 two approaches are used to define mjo phases 1 the local phase is determined at each longitude and time from filtered outgoing longwave radiation and 2 the global phase is defined using a popular real time multivariate mjo rmm index which assigns the tropics to an mjo phase each day in terms of local phase cloudsat results show a familiar evolution of cloud type predominance in the growing stages shallow clouds coexist with deep intense but narrow convective systems widespread cloud coverage and rainfall appear during the active phases becoming more anvil dominated with time and finally suppressed conditions return results are compared to the convectively coupled kelvin wave which has a similar life cycle to the mjo convection in the mjo tends to be modulated more by moisture variations compared to the kelvin wave in terms of globa

long term uplift of the santa cruz coastline in response to repeated earthquakes along the san andreas fault abstract the 18 october 1989 loma prieta earthquake m s 7 1 provides unprecedented insights into geomorphological processes of the santa cruz mountains region of central california in particular it inspires a simple explanation for the uplift that the area has been experiencing through its recent geological past predicted tectonic uplift from 442 oblique slip earthquakes on the loma prieta fault plane reproduces the variable elevations of 36 positions along the lowest santa cruz marine terrace within observational uncertainties an inferred formation height of 8 9 3 m ties the cutting of this terrace with the global sea level highstand at 125 kyr b p since then uplift rates between 0 13 and 0 35 mm yr have been maintained along the coast about one third as fast as previously proposed loma prieta type earthquakes recur every three to six centuries and account for less than half of the strike slip plate motion on this segment of the san andreas repetition of these characteristic events over much longer periods likely explains the deformation of the older terraces and motivates the configuration of this portion of the coastal range

structure genesis and scale selection of the tropical quasi biweekly mode the quasi biweekly mode qbm and the 30 60 day mode are two major intraseasonal oscillations isos in the tropics the qbm is known to have a major influence in determining the active and break conditions of the indian monsoon during the northern summer a westward propagating equatorial rossby wave with quasi biweekly period influences the australian monsoon during the northern winter universality between the summer and winter qbm is established through analysis of daily circulation and convection data for 10 years it is shown that the mean spatial structure of the qbm in circulation and convection resembles that of a gravest meridional mode equatorial rossby wave with wavelength of about 6000 km and westward phase speed of approximately 4 5 m s 1 however the maximum zonal wind occurs at around 5 n 5 s during the northern summer winter the wave structure appears to be translated northward southward by about 5 during the northern summer winter the relationship between outgoing long wave radiation and circulation data indicates that the mode is driven unstable by coupling with moist convection similarity in temporal and spatial characteristics of the mode during the two seasons leads us to propose that the same mechanism governs the genesis and scale selection of the mode in both the seasons an acceptable mechanism for genesis and scale selection of the qbm has been lacking in the present study a mechanism for genesis and scale selection of the observed qbm is proposed a simple 2 layer model that includes a steady ekman boundary layer bl formulation incorporating effect of entrainment mixing is constructed for the convectively coupled equatorial waves without influence of the background mean flow moist feedback in the presence of frictional bl convergence drives the gravest meridional mode equatorial rossby wave unstable with observed wavelength and period but with zonal winds symmetric about the equator potential temperature perturbation associated with the rossby wave is in phase with relative vorticity perturbation at low level the bl drives moisture convergence in phase with the relative vorticity at the top of the bl release of latent heat associated with the bl convergence enhances the potential temperature leading to a positive feedback the mean flow over the indian ocean and western pacific at low levels is such that the zero ambient absolute vorticity or the dynamic equator shifts to around 5 n 5 s during summer winter and results in a shift of the unstable rossby waves towards the north south by about 5 the resulting structure of the unstable rossby mode resembles the observed structure of the biweekly mode it is shown that neither evaporation wind feedback nor vertical shear of the mean flow is crucial for the existence of the mode however these processes marginally modify the growth rate and make the structure of the unstable wave more realistic