investigating multiple fault rupture at the salar del carmen segment of the atacama fault system northern chile fault scarp morphology and knickpoint analysis this study presents a new geomorphological approach to investigate the past activity and potential seismic hazard of upper crustal faults at the salar del carmen segment of the atacama fault system in the northern chile forearc our contribution is based on the analysis of a large set of topographic profiles and allows extrapolating fault analysis from a few selected locations to distances of kilometers along strike of the fault we detected subtle changes in the fault scarp geometry which may represent the number of paleoearthquakes experienced by the structure and extracted the cumulative and last incremental displacement along strike of the investigated scarps we also tested the potential of knickpoints in channels crossing the fault scarps as markers for repeated fault rupture and proxies for seismic displacement the number of paleoearthquakes derived from our analysis is 2 3 well in agreement with recent paleoseismological investigations which suggest 2 3 earthquakes mw 6 5 6 7 at the studied segments knickpoints record the number of events for about 55 of the analyzed profile pairs only few knickpoints represent the full seismic displacement while most retain only a fraction of the displacement the along strike displacement distributions suggest fault growth from the center toward the tips and linkage of individual ruptures our approach also improves the estimation of paleomagnitudes in case of multiple fault rupture by allowing to quantify the last increment of displacement separately paleomagnitudes calculated from total segment length and the last increment of displacement mw 6 5 7 1 are in agreement with paleoseismological results

surface ruptures and building damage of the 2003 bam iran earthquake mapped by satellite synthetic aperture radar interferometric correlation 1 we use the interferometric correlation from envisat synthetic aperture radar sar images to map the details of the surface ruptures related to the 26 december 2003 earthquake that devastated bam iran the main strike slip fault rupture south of the city of bam has a series of four segments with left steps shown by a narrow line of low correlation in the coseismic interferogram this also has a clear expression in the field because of the net extension across the fault just south of the city limits the surface strain becomes distributed over a width of about 500 m probably because of a thicker layer of soft sedimentary material another fault north of bam shows offset and low correlation over a wider zone in the interferograms but it has no discrete surface rupture possibly because of a net shortening across this fault taking the difference between the interferometric correlation for an interval including the earthquake and an interval before the earthquake separates the changes due to the earthquake from other effects in the partially vegetated city of bam we map the damage to buildings by measuring the change from high correlation to low correlation where buildings were destroyed by the earthquake

permanent deformation caused by subduction earthquakes in northern chile earth s crust is thought to eventually rebound following an earthquake so that deformation is not permanent field analysis in the atacama desert northern chile however identifies numerous large cracks in the crust implying that the crust here has been permanently deformed by thousands of earthquakes that have occurred over the past million years

distribution of slip from 11 mw 6 earthquakes in the northern chile subduction zone we use interferometric synthetic aperture radar gps and teleseismic data to constrain the relative location of coseismic slip from 11 earthquakes on the subduction interface in northern chile 23 25 s between the years 1993 and 2000 we invert body wave waveforms and geodetic data both jointly and separately for the four largest earthquakes during this time period 1993 m w 6 8 1995 m w 8 1 1996 m w 6 7 1998 m w 7 1 while the location of slip in the teleseismic only geodetic only and joint slip inversions is similar for the small earthquakes there are differences for the 1995 m w 8 1 event probably related to nonuniqueness of models that fit the teleseismic data there is a consistent mislocation of the harvard centroid moment tensor locations of many of the 6 6 earthquakes as well as three m w 7 events from the 1980s all of these earthquakes appear to rupture different portions of the fault interface and do not rerupture a limited number of asperities

surface cracks record long term seismic segmentation of the andean margin understanding the long term patterns of great earthquake rupture along a subduction zone provides a framework for assessing modern seismic hazard however evidence that can be used to infer the size and location of past earthquakes is typically erased by erosion after a few thousand years meter scale cracks that cut the surface of coastal areas in northern chile and southern peru preserve a record of earthquakes spanning several hundred thousand years owing to the hyperarid climate of the region these cracks have been observed to form during and or shortly after strong subduction earthquakes are preserved for long time periods throughout the atacama desert demonstrate evidence for multiple episodes of reactivation and show changes in orientation over spatial scales similar to the size of earthquake segments our observations and models show that crack orientations are consistent with dynamic and static stress fi elds generated by recent earthquakes while localized structural and topographic processes infl uence some cracks the strong preferred orientation over large regions indicates that cracks are primarily formed by plate boundary scale stresses namely repeated earthquakes we invert the crack based strain data for slip along the well known iquique seismic gap segment of the margin and fi nd consistency with gravity anomaly based inferences of long term earthquake slip patterns as well as the magnitude and location of the november 2007 tocopilla earthquake we suggest that the meter scale cracks can be used to map characteristic earthquake rupture segments that persist over many seismic cycles which encourages future study of cracks and other small scale structures to better constrain the persistence of asperities in other arid tectonically active regions

interseismic coupling and seismic potential along the central andes subduction zone we use about two decades of geodetic measurements to characterize interseismic strain build up along the central andes subduction zone from lima peru to antofagasta chile these measurements are modeled assuming a 3 plate model nazca andean sliver and south america craton and spatially varying interseismic coupling isc on the nazca megathrust interface we also determine slip models of the 1996 m w 7 7 nazca the 2001 m w 8 4 arequipa the 2007 m w 8 0 pisco and the m w 7 7 tocopilla earthquakes we find that the data require a highly heterogeneous isc pattern and that overall areas with large seismic slip coincide with areas which remain locked in the interseismic period with high isc offshore lima where the isc is high a m w 8 6 8 8 earthquake occurred in 1746 this area ruptured again in a sequence of four m w 8 0 earthquakes in 1940 1966 1974 and 2007 but these events released only a small fraction of the elastic strain which has built up since 1746 so that enough elastic strain might be available there to generate a m w 8 5 earthquake the region where the nazca ridge subducts appears to be mostly creeping aseismically in the interseismic period low isc and seems to act as a permanent barrier as no large earthquake ruptured through it in the last 500 years in southern peru isc is relatively high and the deficit of moment accumulated since the m w 8 8 earthquake of 1868 is equivalent to a magnitude m w 8 4 earthquake two asperities separated by a subtle aseismic creeping patch are revealed there this aseismic patch may arrest some rupture as happened during the 2001 arequipa earthquake but the larger earthquakes of 1604 and 1868 were able to rupture through it in northern chile isc is very high and the rupture of the 2007 tocopilla earthquake has released only 4 of the elastic strain that has accumulated since 1877 the deficit of moment which has accumulated there is equivalent to a magnitude m w 8 7 earthquake this study thus provides elements to assess the location size and magnitude of future large megathurst earthquakes in the central andes subduction zone caveats of this study are that interseismic strain of the forearc is assumed time invariant and entirely elastic also a major source of uncertainty is due to fact that the available data place very little constraints on interseismic coupling at shallow depth near the trench except offshore lima where sea bottom geodetic measurements have been collected suggesting strong coupling

basin centered asperities in great subduction zone earthquakes a link between slip subsidence and subduction erosion 1 published areas of high coseismic slip or asperities for 29 of the largest circum pacific megathrust earthquakes are compared to forearc structure revealed by satellite free air gravity bathymetry and seismic profiling on average 71 of an earthquake s seismic moment and 79 of its asperity area occur beneath the prominent gravity low outlining the deep sea terrace 57 of an earthquake s asperity area on average occurs beneath the forearc basins that lie within the deep sea terrace in sw japan slip in the 1923 1944 1946 and 1968 earthquakes was largely centered beneath five forearc basins whose landward edge overlies the 350 c isotherm on the plate boundary the inferred downdip limit of the locked zone basin centered coseismic slip also occurred along the aleutian mexico peru and chile subduction zones but was ambiguous for the great 1964 alaska earthquake beneath intrabasin structural highs seismic slip tends to be lower possibly due to higher temperatures and fluid pressures kilometers of late cenozoic subsidence and crustal thinning above some of the source zones are indicated by seismic profiling and drilling and are thought to be caused by basal subduction erosion the deep sea terraces and basins may evolve not just by growth of the outer arc high but also by interseismic subsidence not recovered during earthquakes basin centered asperities could indicate a link between subsidence subduction erosion and seismogenesis whatever the cause forearc basins may be useful indicators of long term seismic moment release the source zone for cascadia s 1700 a d earthquake contains five large basin centered gravity lows that may indicate potential asperities at depth the gravity gradient marking the inferred downdip limit to large coseismic slip lies offshore except in northwestern washington where the low extends landward beneath the coast transverse gravity highs between the basins suggest that the margin is seismically segmented and could produce a variety of large earthquakes

crack formation on top of propagating reverse faults of the chuculay fault system northern chile insights from field data and numerical modelling abstract reverse faults in northern chile have formed 20 300 m high scarps that contain open fractures which occur in a zone of 20 1600 m wide two dimensional numerical models were used to explore the geometrical and mechanical parameters needed to produce extension within a bulk contractional regime all of the mechanical models show the same structure as the field a concentration of cracks predominantly at the top rather than on the forelimbs of the scarps in the field case extension begins as soon as a discrete scarp forms with progressive shortening the scarp height increases producing a broadening of the zone in extension the numerical models show that this broadening stabilizes when a maximum in the scarp height is reached to produce concentration of the extension on top of the scarps the reverse fault needs to be weak 10 the models suggest that distribution of this extensional zone depends on the cross sectional geometry of the fault and on the location of the detachment at depth the main mechanism that produces extension on the top of the reverse scarp is stretching of the topographic surface by folding of the hanging wall at the tip of the fault zone

isotopic evidence for the source of ca and s in soil gypsum anhydrite and calcite in the atacama desert chile abstract the origin of pedogenic salts in the atacama desert has long been debated possible salt sources include in situ weathering at the soil site local sources such as aerosols from the adjacent pacific ocean or salt encrusted playas salars and extra local atmospheric dust to identify the origin of ca and s in atacama soil salts we determined 34 s and 87 sr 86 sr values of soil gypsum anhydrite and 87 sr 86 sr values of soil calcite along three east west trending transects our results demonstrate the strong influence of marine aerosols on soil gypsum anhydrite development in areas where marine fog penetrates inland results from an east west transect located along a breach in the coastal cordillera show that most soils within 90 km of the coast and below 1300 m in elevation are influenced by marine aerosols and that soils within 50 km and below 800 m in elevation receive 50 of ca and s from marine aerosols 34 s values 14 and 87 sr 86 sr values 0 7083 in areas where the coastal cordillera is 1200 m in elevation however coastal fog cannot penetrate inland and the contribution of marine aerosols to soils is greatly reduced most pedogenic salts from inland soils have 34 s values between 5 0 to 8 0 and 87 sr 86 sr ratios between 0 7070 and 0 7076 these values are similar to average 34 s and 87 sr 86 sr values of salts from local streams lakes and salars 5 4 2 34 s and 0 70749 0 00045 87 sr 86 sr in the andes and atacama suggesting extensive eolian reworking of salar salts onto the surrounding landscape ultimately salar salts are precipitated from evaporated ground water which has acquired its dissolved solutes from water rock interactions both high and low temperature along flowpaths from recharge areas in the andes therefore the main source for ca and s in gypsum anhydrite in non coastal soils is indirect and involves bedrock alteration not surficially on the hyperarid landscape but in the subsurface by ground water followed by eolian redistribution of ground water derived salar salts to soils the spatial distribution of high grade nitrate deposits appears to correspond with areas that receive the lowest fluxes of local marine and salar salt supporting arguments for tropospheric nitrogen as the main source for soil nitrate

subduction earthquake deformation associated with 14 november 2007 mw 7 8 tocopilla earthquake in chile results from insar and aftershocks abstract on 14 november 2007 a subduction thrust earthquake magnitude mw 7 8 occurred in the coastal region of northern chile causing substantial damage to the city of tocopilla we investigate the source fault of the earthquake slip distribution and fault interaction by integrating aftershock locations satellite interferometry data and stress model simulations aftershock measurements allow us to locate the area and geometry of the rupture plane in the coastal region between the cities of tocopilla and antofagasta combining two satellite viewing geometries acquired in envisat s wide swath and image modes we observe decimetre scale coseismic deformation the maximum line of sight displacement is found to be about 40 cm located at the mejillones peninsula slip inversions using elastic half space models with geometry constrained by aftershocks suggest rupturing of an area of 160 km by 50 km along the nazca south america convergent margin between latitudes 22 s and 23 5 s the main slip is concentrated on two asperities the largest being located in the southern part of the rupture area at a depth of approximately 30 50 km with a magnitude of about 2 5 m because aftershock distribution may also suggest a region of shallow crustal deformation activity located offshore we investigate whether the 2007 tocopilla earthquake also involved shallow crustal fault slip offshore although we find that the latter assumption is supported by coulomb stress modelling and geologic inferences our geodetic and seismic data provide insufficient constraints to resolve the exact geometry and kinematics of dislocation on this structure

megathrust earthquake swarms indicate frictional changes which delimit large earthquake ruptures abstract using a recently constructed catalog of megathrust earthquake swarms we present results that illustrate how fault slip for m w 8 5 earthquakes with a publicly available finite fault rupture model is delimited along strike by swarm regions we further investigate this relationship for all m w 7 5 subduction zone megathrust earthquakes that have occurred over the last 40 years by estimating the rupture area from early aftershocks this extended comparison shows only 2 out of 42 earthquakes propagate through regions of the megathrust that have documented recurring earthquake swarm activity while about 40 17 out of 42 are terminate on at least one side near regions with swarm activity in japan chile sumatra and alaska earthquake swarms correlate with regions of the plate interface that exhibit low interseismic strain accumulation this suggests earthquake swarms are associated with reduced plate coupling and possibly aseismic moment release however earthquakes in chile and alaska ruptured through regions of weak coupling that do not show swarm activity we propose instead that stress heterogeneity on the megathrust can best explain why large earthquake ruptures terminate in swarm regions but not in regions with weak coupling alone earthquake swarms appear to be a proxy for along strike segmentation of subduction megathrusts at least on the time scale of one seismic cycle

nature and tectonic significance of co seismic structures associated with the mw 8 8 maule earthquake central southern chile forearc abstract the mw 8 8 maule earthquake on february 27 2010 affected the central southern chilean forearc of the central andes here we show the results of field investigations of surface deformation associated with this major earthquake observations were carried out within three weeks after the seismic event mostly in the central and northern part of the forearc overlying the rupture zone we provide a detailed field record of co seismic surface deformation and examine its implications on active andean tectonics surface rupture consisted primarily of extensional cracks push up structures fissures with minor lateral displacements and a few but impressive extensional geometries similar to those observed in analogical modeling of rift systems a major group of nw wnw striking fractures representing co seismic extensional deformation is found at all localities these appear to be spatially correlated to long lived basement fault zones the nw striking normal focal mechanism of the mw 6 9 aftershock occurred on march 11 demonstrates that the basement faults were reactivated by the mw 8 8 maule earthquake the co seismic surface ruptures show patterns of distributed deformation similar to those observed in mapped basement involved structures we propose that co seismic reactivation of basement structures play a fundamental role in stress release in the upper plate during large subduction earthquakes the fundamental mechanism that promotes stress relaxation is largely driven by elastic rebound of the upper plate located right above the main rupture zone

influence of fore arc structure on the extent of great subduction zone earthquakes 1 structural features associated with fore arc basins appear to strongly influence the rupture processes of large subduction zone earthquakes recent studies demonstrated that a significant percentage of the global seismic moment release on subduction zone thrust faults is concentrated beneath the gravity lows resulting from fore arc basins to better determine the nature of this correlation and to examine its effect on rupture directivity and termination we estimated the rupture areas of a set of mw 7 5 8 7 earthquakes that occurred in circum pacific subduction zones we compare synthetic and observed seismograms by measuring frequency dependent amplitude and arrival time differences of the first orbit rayleigh waves at low frequencies the amplitude anomalies primarily result from the spatial and temporal extent of the rupture we then invert the amplitude and arrival time measurements to estimate the second moments of the slip distribution which describe the rupture length width duration and propagation velocity of each earthquake comparing the rupture areas to the trench parallel gravity anomaly tpga above each rupture we find that in 11 of the 15 events considered in this study the tpga increases between the centroid and the limits of the rupture thus local increases in tpga appear to be related to the physical conditions along the plate interface that favor rupture termination owing to the inherently long timescales required for forearc basin formation the correlation between the tpga field and rupture termination regions indicates that long lived material heterogeneity rather than short timescale stress heterogeneities are responsible for arresting most great subduction zone ruptures

a threshold in soil formation at earth s arid hyperarid transition the soils of the atacama desert in northern chile have long been known to contain large quantities of unusual salts yet the processes that form these soils are not yet fully understood we examined the morphology and geochemistry of soils on post miocene fans and stream terraces along a south to north 27 to 24 s rainfall transect that spans the arid to hyperarid transition 21 to 2 mm rain y 1 landform ages are 2 my based on cosmogenic radionuclide concentrations in surface boulders and ar isotopes in interbedded volcanic ash deposits near the driest site indicate a maximum age of 2 1 my a chemical mass balance analysis that explicitly accounts for atmospheric additions was used to quantify net changes in mass and volume as a function of rainfall in the arid 21 mm rain y 1 soil total mass loss to weathering of silicate alluvium and dust 1030 kg m 2 is offset by net addition of salts 170 kg m 2 the most hyperarid soil has accumulated 830 kg m 2 of atmospheric salts including 260 kg sulfate m 2 and 90 kg chloride m 2 resulting in unusually high volumetric expansion 120 for a soil of this age the composition of both airborne particles and atmospheric deposition in passive traps indicates that the geochemistry of the driest soil reflects accumulated atmospheric influxes coupled with limited in soil chemical transformation and loss long term rates of atmospheric solute addition were derived from the ion inventories in the driest soil divided by the landform age and compared to measured contemporary rates with decreasing rainfall the soil salt inventories increase and the retained salts are both more soluble and present at shallower depths all soils generally exhibit vertical variation in their chemistry suggesting slow and stochastic downward water movement and greater climate variability over the past 2 my than is reflected in recent 100 y rainfall averages the geochemistry of these soils shows that the transition from arid to hyperarid rainfall levels marks a fundamental geochemical threshold in wetter soils the rate and character of chemical weathering results in net mass loss and associated volumetric collapse after 105 to 106 years while continuous accumulation of atmospheric solutes in hyperarid soils over similar timescales results in dramatic volumetric expansion the specific geochemistry of hyperarid soils is a function of atmospheric sources and is expected to vary accordingly at other hyperarid sites this work identifies key processes in hyperarid soil formation that are likely to be independent of location and suggests that analogous processes may occur on mars

recently active contractile deformation in the forearc of southern peru abstract geomorphic and structural features of southern peru 14 18 s provide strong evidence for distributed crustal deformation along range sub parallel contractile structures we use in situ produced cosmogenic radionuclides in conjunction with field and remote mapping to determine the ages of geomorphic features and find 1 ancient surfaces 1 ma preserved as a result of very low surface erosion rates 2 young 30 ka low relief pediment surfaces developed during recent landscape modifications 3 active tectonic structures accommodating compressional stresses and 4 pleistocene river incision rates of 0 3 mm yr consistent with longer term rates in this region of southern peru the steep western wedge trench to arc area of the andean margin presently maintains the high topography of the altiplano through a combination of uplift and contractile deformation along steep east dipping faults and isostatic responses to the focused removal of large amounts of crustal material through canyon incision

land subsidence and caprock dolines caused by subsurface gypsum dissolution and the effect of subsidence on the fluvial system in the upper tigris basin between bismil batman turkey abstract karstification based land subsidence was found in the upper tigris basin with dimensions not seen anywhere else in turkey the area of land subsidence where there are secondary and tertiary subsidence developments reaches 140 km 2 subsidence depth ranges between 40 and 70 m the subsidence was formed as a result of subsurface gypsum dissolution in lower miocene formation although there are limestones together with gypsum and eocene limestone below them in the area a subsidence with such a large area is indicative of karstification in the gypsum the stratigraphical cross sections taken from the wells and the water analyses also verify this fact the lower miocene gypsum which shows confined aquifer features was completely dissolved by the aggressive waters injected from the top and discharged through by zellek fault this resulted in the development of subsidence and formation of caprock dolines on loosely textured upper miocene pliocene cover formations the tigris river runs through the subsidence area between batman and bismil there are four terrace levels as t1 40 m t2 30 m t3 10 m and t4 4 5 m in the tigris river valley it was also found that there were some movements of the levels of the terraces in the valley by subsidence the subsidence developed gradually throughout the quaternary however no terrace was formed purely because of subsidence

upper plate deformation and seismic barrier in front of nazca subduction zone the chololo fault system and active tectonics along the coastal cordillera southern peru abstract the south america plate boundary is one of the most active subduction zone the recent mw 8 4 arequipa 2001 earthquake ruptured the subduction plane toward the south over 400 km and stopped abruptly on the ilo peninsula in this exact region the subduction seismic crisis induced the reactivation of continental fault systems in the coastal area we studied the main reactivated fault system that trends perpendicular to the trench by detailed mapping of fault related geomorphic features also at a longer time scale a recurrent quaternary transtensive tectonic activity of the cfs is expressed by offset river gullies and alluvial fans the presence of such extensional fault systems trending orthogonal to the trench along the coastal cordillera in southern peru is interpreted to reflect a strong coupling between the two plates in this particular case stress transfer to the upper plate at least along the coastal fringe appears to have induced crustal seismic events that were initiated mainly during and after the 2001 earthquake the seafloor roughness of the subducting plate is usually thought to be a cause of segmentation along subduction zones however after comparing and discussing the role of inherited structures within the upper plate to the subduction zone segmentation in southern peru we suggest that the continental structure itself may exert some feedback control on the segmentation of the subduction zone and thus participate to define the rupture pattern of major subduction earthquakes along the southern peru continental margin

simulation of tensile crack generation by three dimensional dynamic shear rupture propagation during an earthquake 1 as there is no evidence that cracks are created directly in modes ii and iii shear cracks probably occur only along a weakness plane as in a preexisting fault mode i fracture therefore may be an important factor in crack formation during shallow earthquakes a three dimensional shear dynamic rupture process was simulated on the assumption that shear slip occurs only in a preexisting fault and the possibility of introducing new internal cracks that propagate under tensile stress as a consequence of the dynamic process of shear slip propagation the discrete element method dem was used to solve this problem because it can introduce internal tensile cracks the simple slip weakening model was used as the friction law on the preexisting fault for shear rupture propagation for new tensile cracks fracture follows classical griffith theory when the critical value for tensile fracture surface energy is reached the proposed model was used to simulate the rupture process of a strike slip shallow fault results show that the generation of new cracks is affected by rupture directivity in terms of the hypocenter and asperity location as well as by fault geometry with respect to the free surface cracks develop a flower like structure that surrounds the preexisting fault when the asperity is located at less than a certain depth the flower like structure that originates from the top of the fault reaches the free surface we consider that this is the mechanism for forming the flower structure near surface during a strike slip shallow earthquake

neogene climate change and uplift in the atacama desert chile the relationship between andean uplift and extreme desiccation of the west coast of south america is important for understanding the interplay between climate and tectonics in the central andes yet it is poorly understood here we use soil morphological char acteristics salt chemistry and mass independent fractionation anomalies 17 o values in dated paleosols to reconstruct a middle miocene climatic transition from semiaridity to extreme hyperaridity in the atacama desert paleosols along the southeastern margin of the calama basin change from calcic vertisols with root traces slickensides and gleyed horizons to an extremely mature salic gypsisol with pedogenic nitrate we interpret this transition which occurred between 19 and 13 ma to represent a change in precipitation from 200 mm yr to 20 mm yr this drastic reduction in precipitation likely resulted from uplift of the central andes to elevations 2 km the uplift blocked moisture from the south american summer monsoon from entering the atacama the mid miocene gyp sisol with pedogenic nitrate is located at elevations between 2900 and 3400 m in the cal ama basin significantly higher than modern nitrate soils which occur below 2500 m modern and quaternary soils in this elevation zone contain soil carbonate and lack ped ogenic gypsum and nitrate we infer that 900 m of local surface uplift over the past 10 m y displaced these nitrate paleosols relative to modern nitrate soils and caused a return to wetter conditions in the calama basin by decreasing local air temperatures and creating an orographic barrier to pacific air masses

variable rupture mode of the subduction zone along the ecuador colombia coast three large earthquakes occurred within the rupture zone of the 1906 colombia ecuador earthquake m w 8 8 in 1942 m s 7 9 1958 ms 7 8 and 1979 m s 7 7 we compared the size and mechanism of these earthquakes by using long period surface waves tsunami data and macroseismic data the 1979 event is a thrust event with a seismic moment of 2 9 10 28 dyne cm and represents subduction of the nazca plate beneath south america the rupture length and direction are 230 km and n40 e respectively examination of old seismograms indicates that the 1906 event is also a thrust event which ruptured in the northeast direction the seismic moment estimated from the tsunami data and the size of the rupture zone is 2 10 29 dyne cm the 1942 and 1958 events are much smaller about 1 5 to 1 10 of the 1979 event in the seismic moment than the 1979 event we conclude that the sum of the seismic moments of the 1942 1958 and 1979 events is only formula of that of the 1906 event despite the fact that the sequence of the 1942 1958 and 1979 events ruptured approximately the same segment as the 1906 event this difference could be explained by an asperity model in which the fault zone is held by a discrete distribution of asperities with weak zones in between the weak zone normally behaves aseismically but slips abruptly only when it is driven by failure of the asperities a small earthquake represents failure of one asperity and the rupture zone is pinned at both ends by adjacent asperities so that the effective width and the amount of slip are relatively small a great earthquake represents failure of more than one asperity and consequently involves much larger width and slip

pervasive cracking of the northern chilean coastal cordillera new evidence for forearc extension despite convergence across the strongly coupled seismogenic interface between the south american and nazca plates the dominant neotectonic signature in the forearc of northern chile is arc normal extension we have used 1 m resolution ikonos satellite imagery to map nearly 37 000 cracks over an area of 500 km2 near the salar grande 21 s these features which are best preserved in a ubiquitous gypcrete surface layer have both nontectonic and tectonic origins however their strong preferred orientation perpendicular to the plate convergence vector suggests that the majority owe their formation to approximate east west extension associated with plate boundary processes such as interseismic loading coseismic and postseismic strain and long term instability resulting from subduction erosion similar structures were formed during or shortly after the 1995 mw 8 0 earthquake near the city of antofagasta south of salar grande and in conjunction with the 2001 mw 8 2 8 4 arequipa peru event cracks such as these may form in other forearcs but remain largely unexposed because of vegetative cover or marked fluvial erosion factors that are absent in northern chile as a result of its hyperarid climate

u series dating of co seismic gypsum and submarine paleoseismology of active faults in northern chile 23 s abstract the convergence of the nazca and south american plates along the subduction margin of the central andes results in large subduction earthquakes and tectonic activity along major fault systems despite its relevance the paleoseismic record of this region is scarce hampering our understanding about the relationship between the andes building and earthquake occurrence in this study we used the u series disequilibrium method to obtain absolute ages of paleoearthquake events associated with normal displacements along the active mejillones and salar del carmen faults in the coastal range of the atacama desert of northern chile the 230th 234u disequilibrium ages in co seismic gypsum salts sampled along the fault traces together with marine evidences indicate that earthquakes occurred at ca 29 7 1 7 ka 11 4 ka and 2 4 0 8 ka when coupled with paleoseismic marine and radiocarbon 14c records in the nearby mejillones bay evidencing large dislocations along the mejillones fault the geochronological dataset presented here is consistent with the notion that gypsum salts formed during large earthquakes as a result of co seismic dilatancy pumping of saline waters along the major faults based on maximum observed cumulative vertical offsets in the studied faults this phenomena could have occurred episodically at a rate in the order of 1 40 to 1 50 with respect to the very large subduction earthquakes during the latest pleistocene holocene period the results presented here reveal that the u series disequilibrium method can be successfully applied to date the gypsum salts deposited along faults during seismic events and therefore directly constrain the age of large paleoearthquakes in hyperarid and seismically active zones

andean coastal uplift and active tectonics in southern peru 10be surface exposure dating of differentially uplifted marine terrace sequences san juan de marcona 15 4 s article i nfo along the san juan de marcona bay of southern peru two spectacular sequences of preserved marine terraces record net quaternary uplift previous geomorphic analysis of these paleo shorelines has revealed evidence of upper plate deformation and regional uplift however in the absence of a robust absolute dating method these studies contain substantial uncertainties concerning the numerical dating of these marine markers and thus the corresponding calculated surface uplift rates however field mapping surveying the neotectonic features and 10 be dating of abraded surfaces contained within two sequences of marine terraces along this margin should allow for the robust calculation of pleistocene uplift rates the san juan de marcona bay lies on the southern flank of the subducting and south migrating aseismic nazca ridge where the maximum rates of coastal uplift are expected in this locality we measure high uplift rates ranging from 0 4 m ka to 0 9 m ka during the pleistocene margin parallel normal faults displace several marine terraces and influence the development of bays thereby contributing to the configuration of paleo and present day coastlines the faults have relatively low slip rates b0 1 m ka over 400 ka and have been inactive for the last 80 ka the presence and activity of these normal faults can be directly linked to subduction zone processes with the release and accommodation of short term coseismic compression during megathrust subduction zone events in contrast the regional permanent uplift is probably controlled by post seismic and or interseismic strain accumulation over longer time scales due to inelastic behavior of the upper plate since at least the latest pliocene the san juan de marcona area has experienced long term regional tectonic uplift that has increased since about 800 ka due to the southward migration of the subducting nazca ridge based on migration velocity and geometry of the ridge the influence of the nazca ridge on the uplift of the forearc should account for 0 4 m ka within 145 km south of the ridge axis hence most of the post 400 ka mean uplift rate of the san juan de marcona area could be explained by the nazca ridge subduction

testing mechanisms of subduction zone segmentation and seismogenesis with slip distributions from recent andean earthquakes abstract a long standing goal of subduction zone earthquake studies is to determine whether or not there are physical processes that control seismogenesis and the along strike segmentation of the megathrust studies of individual earthquakes and global compilations of earthquakes find favorable comparison between coseismic interplate slip distributions and several different long lived forearc characteristics such as bathymetry coastline morphology crustal structure and interplate frictional properties but no single explanation seems to govern the location and slip distribution of all earthquakes one possible reason for the lack of a unifying explanation is that the inferred earthquake parameters most importantly the slip distribution calculated in some areas were inaccurate blurring correlation between earthquake and physical parameters in this paper we seek to test this possibility by comparing accurate slip distributions constrained by multiple datasets along several segments of a single subduction zone with the various physical properties that have been proposed to control or correlate with seismogenesis we examine the rupture area and slip distribution of 6 recent and historical large mw 7 earthquakes on the peru northern chile subduction zone this analysis includes a new slip distribution of the 14 november 2007 mw 7 7 earthquake offshore tocopilla chile constrained by teleseismic body wave and insar data in studying the 6 events we find that no single mechanism can explain the location or extent of rupture of all earthquakes but analysis of the forearc gravity field and its gradients shows correlation with many of the observed slip patterns as suggested by previous studies additionally large scale morphological features including the nazca ridge arica bend mejillones peninsula and transverse crustal fault systems serve as boundaries between distinct earthquake segments

geodetic teleseismic and strong motion constraints on slip from recent southern peru subduction zone earthquakes we use seismic and geodetic data both jointly and separately to constrain coseismic slip from the 12 november 1996 m w 7 7 and 23 june 2001 m w 8 5 southern peru subduction zone earthquakes as well as two large aftershocks following the 2001 earthquake on 26 june and 7 july 2001 we use all available data in our inversions gps interferometric synthetic aperture radar insar from the ers 1 ers 2 jers and radarsat 1 satellites and seismic data from teleseismic and strong motion stations our two dimensional slip models derived from only teleseismic body waves from south american subduction zone earthquakes with m w 7 5 do not reliably predict available geodetic data in particular we find significant differences in the distribution of slip for the 2001 earthquake from models that use only seismic teleseismic and two strong motion stations or geodetic insar and gps data the differences might be related to postseismic deformation or more likely the different sensitivities of the teleseismic and geodetic data to coseismic rupture properties the earthquakes studied here follow the pattern of earthquake directivity along the coast of western south america north of 5 s earthquakes rupture to the north south of about 12 s directivity is southerly and in between earthquakes are bilateral the predicted deformation at the arequipa gps station from the seismic only slip model for the 7 july 2001 aftershock is not consistent with significant preseismic motion

large trench parallel gravity variations predict seismogenic behavior in subduction zones we demonstrate that great earthquakes occur predominantly in regions with a strongly negative trench parallel gravity anomaly tpga whereas regions with strongly positive tpga are relatively aseismic these observations suggest that over time scales up to at least 1 million years spatial variations of seismogenic behavior within a given subduction zone are stationary and linked to the geological structure of the fore arc the correlations we observe are consistent with a model in which spatial variations in frictional properties on the plate interface control trench parellel variations in fore arc topography gravity and seismogenic behavior

inverting for slip on three dimensional fault surfaces using angular dislocations the increasing quality of geodetic data synthetic aperture radar interferometry insar dense global positioning system gps arrays now available to geophysicists and geologists are not fully exploited in slip inversion procedures most common methods of inversion use rectangular dislocation segments to model fault ruptures and therefore oversimplify fault geometries these geometric simplifications can lead to inconsistencies when inverting for slip on earthquake faults and they preclude a more complete understanding of the role of fault geometry in the earthquake process we have developed a new three dimensional slip inversion method based on the analytical solution for an angular dislocation in a linear elastic homogeneous isotropic half space the approach uses the boundary element code poly3d that employs a set of planar triangular elements of constant displacement discontinuity to model fault surfaces the use of triangulated surfaces as discontinuities permits one to construct fault models that better approximate curved three dimensional surfaces bounded by curved tiplines shapes that commonly are imaged by three dimensional reflection seismic data and inferred from relocated aftershock data we demonstrate the method s ability to model three dimensional rupture geometries by inverting for slip associated with the 1999 hector mine earthquake the resulting model avoids displacement anomalies associated with the overlapping rectangular dislocations used in previous models improving the fit to the geodetic data by 32 and honors the observed surface ruptures thereby allowing more direct comparisons between geologic and geodetic data on slip distributions online material hector mine input files and file format description

prolonged extension and subsidence of the peruvian forearc during the cenozoic abstract ocean continental subduction zones are commonly associated with compressional stress fields which ultimately result in regional uplift of the overriding plate this has particularly been inferred by most studies for the western margin of the peruvian andes however local geological observations have contested this idea here we present a review of existing local and international literature supplemented by new structural and geomorphic observations that suggest that nearly the entire central 15 to 11 s latitude and northern peruvian forearc 11 to 6 s latitude are under extension with a slight tendency to transtension instead of compression and that this region has experienced a prolonged period of subsidence since the middle late eocene interrupted by short pulses of uplift in contrast the southern peruvian forearc 15 to 18 s latitude has experienced trans tension from the middle late eocene until recent in combination with uplift the central and southern peruvian forearc that was influenced by the passage of the nazca ridge experienced transtension and subsidence until the middle late miocene and alternating phases of compressional and transtensional tectonics afterwards these new findings on the geodynamic development of the peruvian forearc need to be considered in future reconstructions of the mechanisms at work within this subduction zone

from decades to epochs spanning the gap between geodesy and structural geology of active mountain belts geodetic data from the global navigation satellite system gnss and from satellite interferometric radar insar are revolutionizing how we look at instantaneous tectonic deformation but the significance for long term finite strain in orogenic belts is less clear we review two different ways of analyzing geodetic data velocity gradient fields from which one can extract strain dilatation and rotation rate and elastic block modeling which assumes that deformation is not continuous but occurs primarily on networks of interconnected faults separating quasi rigid blocks these methods are complementary velocity gradients are purely kinematic and yield information about regional deformation the calculation does not take into account either faults or rigid blocks but where gnss data are dense enough active fault zones and stable blocks emerge naturally in the solution block modeling integrates known structural geometry with idealized earthquake cycle models to predict slip rates on active faults future technological advances should overcome many of today s uncertainties and provide rich new data to mine by providing denser more uniform and temporally continuous observations

invited review paper neogene to quaternary tectonics of the coastal cordillera northern chile abstract the extreme aridity of the northern chilean coastal cordillera enables the complete preservation of permanent deformation related to the coupling between nazca and south america the region between antofagasta and arica is characterized by four types of late cenozoic structures ew striking reverse faults ns striking normal faults sparse wnw and nnw striking right lateral strike slip faults and unimodal and bimodal populations of surface cracks the ew reverse faults occur only between 19 and 21 40 s latitude and have been active since at least 6 ma to present a march 2007 earthquake demonstrates that this deformation can occur during the interseismic phase of the plate boundary seismic cycle the ns normal faults are most abundant near antofagasta and mejillones and diminish in significance northward several of these faults in both the antofagasta and the salar grande area have been reactivated as reverse faults causing minor topographic inversion we suggest that normal faults move during both interseismic and coseismic deformation and are fundamentally very weak surface cracks are ubiquitous throughout the region and form by both non tectonic and tectonic mechanisms a significant proportion forms during coseismic deformation and thus may be used to identify long lived rupture segments on the plate boundary overall forearc deformation is very slow with permanent strain rates of 1 5 nstrain year and fault slip rates less than 0 5 mm year

dynamic stress variations due to shear faults in a plane layered medium summary a complete set of expressions is presented for the computation of elastic dynamic stress in plane layered media we use a discrete wavenumber reflectivity method to compute the stress field radiated by arbitrary moment tensor sources the expressions derived here represent an interesting tool for both the observational and theoretical analysis of dynamic stress changes associated with earthquake phenomena dynamic stress changes associated with a strike slip fault having unilateral rupture are shown this modelling which is similar to the 1992 landers california earthquake illustrates the effects of distance directivity and depth on transient stress changes

the giant coastal landslides of northern chile tectonic and climate interactions on a classic convergent plate margin abstract documented for the first time are an extensive suite of late neogene giant terrestrial coastal landslides along the classic convergent margin of western south america 18 to 24 south these are remarkable in terms of their unusual abundance and atypical setting such failures previously being linked with oceanic volcanic edifices or over steepened glaciated coastlines located within the hyper arid coastal cordillera of the atacama desert of northern chile we report the presence of more than 60 individual large scale landslides with individual volumes up to 9 km 3 developed over a horizontal coastline distance of some 650 km these landslides were emplaced as a combination of rock avalanches and multiple rotational failures the majority terminated directly into the pacific likely generating significant tsunami hazard to the chilean and south peruvian coastline in a region which is today considered to be part of a notorious seismic gap the proliferation and scale of these late neogene giant landslides in this actively uplifting hyperarid terrain suggests they are the main geomorphic agent for relief reduction probably triggered by megathrust earthquakes and potentially providing a unique palaeoseismic archive the temporal and spatial distribution of these giant landslides corresponds with a period of surface steepening of the forearc wedge in the central andes and south to north differential uplift associated with factors such as aseismic ridge subduction the resulting surface gradient increases combined with the persistent climatic aridity of the region have served to limit effective relief reducing geomorphic processes in this oversteepened terrain to large scale landsliding the phenomena documented here geospatially link previously recognised large scale slope failures from the off shore environment and higher altitude areas of the andean forearc suggesting that large scale landsliding is capable of transferring sediment on a regional scale to the off shore peru chile trench this has implications for the friction of the subducting nazca plate and associated seismicity and uplift

late pliocene age for the atacama desert implications for the desertification of western south america the atacama desert forms one of the major hyperarid deserts of the world previous studies suggest that desertification commenced at 14 ma during global climate desiccation sedimentologic data from middle miocene to upper pliocene successions in the modern atacama desert indicate that a semiarid climate persisted from 8 to 3 ma punctuated by a phase of increased aridity at ca 6 ma as such hyperaridity did not commence until the late pliocene implications are 1 that the rain shadow generated by the andean cordillera has had a minor influence on climate change and 2 that the upwelling north flowing cold humboldt current although important in establishing the generally arid climate of western south america did not control the shift to hyperaridity the formation of the hyperarid atacama desert in the late pliocene accompanied the development of the current phase of aridification in the sahara and namib deserts and is attributed to a phase of global climate cooling

fault behavior and characteristic earthquakes examples from the wasatch and san andreas fault zones paleoseismological data for the wasatch and san andreas fault zones have led to the formulation of the characteristic earthquake model which postulates that individual faults and fault segments tend to generate essentially same size or characteristic earthquakes having a relatively narrow range of magnitudes near the maximum analysis of scarp derived colluvium in trench exposures across the wasatch fault provides estimates of the timing and displacement associated with individual surface faulting earthquakes at all of the sites studied the displacement per event has been consistently large measured values range from 1 6 to 2 6 m and the average is about 2 m on the basis of variability in the timing of individual events as well as changes in scarp morphology and fault geometry six major segments are recognized along the wasatch fault on the basis of the most likely number of surface faulting events 18 that have occurred on segments of the wasatch fault zone during the past 8000 years an average recurrence interval of 400 666 years with a preferred average of 444 years is calculated for the entire zone geologic data on the distribution of slip associated with prehistoric earthquakes and slip rates along the south central segment of the san andreas fault suggest that the m 8 1857 earthquake is a characteristic earthquake for this segment comparisons of earthquake recurrence relationships on both the wasatch and san andreas faults based on historical seismicity data and geologic data show that a linear constant b value extrapolation of the cumulative recurrence curve from the smaller magnitudes leads to gross underestimates of the frequency of occurrence of the large or characteristic earthquakes only by assuming a low b value in the moderate magnitude range can the seismicity data on small earthquakes be reconciled with geologic data on large earthquakes the characteristic earthquake appears to be a fundamental aspect of the behavior of the wasatch and san andreas faults and may apply to many other faults as well

hidden holocene slip along the coastal el yolki fault in central chile and its possible link with megathrust earthquakes megathrust earthquakes are commonly accompanied by increased upper plate seismicity and occasionally triggered fault slip in chile crustal faults slipped during and after the 2010 maule m8 8 earthquake we studied the el yolki fault eyof a transtensional structure midways the maule rupture not triggered in 2010 we mapped a holocene coastal plain using lidar which did not reveal surface ruptures however the inner edge and shoreline angles along the coastal plain as well as 4 3 4 0 ka intertidal sediments are back tilted on the eyof footwall block documenting 10 m of vertical displacement these deformed markers imply 2 mm yr throw rate and dislocation models a slip rate of 5 6 mm yr for the eyof in a 5 m deep trench the holocene intertidal sediments onlap to five erosive steps interpreted as staircase wave cut landforms formed by discrete events of relative sea level drop we tentatively associated these steps with coseismic uplift during eyof earthquakes between 4 3 and 4 0 ka the maule earthquake rupture may be subdivided into three subsegments based on coseismic slip and gravity anomalies coulomb stress transfer models predict neutral stress changes at the eyof during the maule earthquake but positive changes for a synthetic slip distribution at the central subsegment if eyof earthquakes were triggered by megathrust events their slip distribution was probably focused in the central subsegment our study highlights the millennial variability of crustal faulting and the megathrust earthquake cycle in chile with global implications for assessing the hazards posed by hidden but potentially seismogenic coastal faults along subduction zones

off fault damage patterns due to supershear ruptures with application to the 2001 mw 8 1 kokoxili kunlun tibet earthquake 1 we extend a model of a two dimensional self healing slip pulse propagating dynamically in steady state with slip weakening failure criterion to the supershear regime in order to study the off fault stressing induced by such a slip pulse and investigate features unique to the supershear range specifically we show that there exists a nonattenuating stress field behind the mach front that radiates high stresses arbitrarily far from the fault practically this would be limited to distances comparable to the depth of the seismogenic zone thus being capable of creating fresh damage or inducing coulomb failure in known structures at large distances away from the main fault we allow for both strike slip and dip slip failure induced by such a slip pulse we show that off fault damage is controlled by the speed of the slip pulse scaled stress drop and principal stress orientation of the prestress field we apply this model to study damage features induced during the 2001 kokoxili kunlun event in tibet for which it has been suggested that much of the rupture was supershear we argue that an interval of simultaneous induced normal faulting is more likely due to a slip partitioning mechanism suggested previously than to the special features of supershear rupture however those features do provide an explanation for otherwise anomalous ground cracking at several kilometers from the main fault we also make some estimates of fracture energy which for a given net slip and dynamic stress drop is lower than for a sub rayleigh slip pulse because part of the energy fed by the far field stress is radiated back along the mach fronts

oligocene miocene age of aridity in the atacama desert revealed by exposure dating of erosion sensitive landforms the age of onset of hyperaridity in the atacama desert chile which is needed to validate geological and climatological concepts has been heretofore uncertain measurement of cosmogenic 21 ne in clasts from erosion sensitive sediment surfaces in northern chile shows that these surfaces have been barely affected by erosion since 25 ma surface exposure ages of sediment clasts give replicate values at 25 20 and 14 ma and individual values at 37 and 9 ma predominantly hyperarid conditions are required to preserve these oldest continuously exposed surfaces on earth our findings are compatible with the hypothesis that the onset of aridity in the atacama desert could be the reason for rather than the consequence of uplift of the high andes

southern peru desert shattered by the great 2001 earthquake implications for paleoseismic and paleo el nino southern oscillation records in the desert region around the coastal city of ilo the great southern peru earthquake of june 23 2001 8 2 8 4 moment magnitude produced intense and widespread ground failure effects these effects included abundant landslides pervasive ground cracking microfracturing of surficial hillslope materials collapse of drainage banks over long stretches widening of hillside rills and lengthening of first order tributary channels we have coined the term shattered landscape to describe the severity of these effects long term consequences of this landscape shattering are inferred to include increased runoff and sediment transport during postearthquake rainstorms this inference was confirmed during the first minor postearthquake rainstorm there which occurred in june and july of 2002 greater amounts of rainfall in this desert region have historically been associated with el nino events previous studies of an unusual paleoflood deposit in this region have concluded that it is the product of el nino generated precipitation falling on seismically disturbed landscapes the effects of the 2001 earthquake and 2002 rainstorm support that conclusion

the repetition of large earthquake ruptures abstract this survey of well documented repeated fault rupture confirms that some faults have exhibited a characteristic behavior during repeated large earthquakes that is the magnitude distribution and style of slip on the fault has repeated during two or more consecutive events in two cases faults exhibit slip functions that vary little from earthquake to earthquake in one other well documented case however fault lengths contrast markedly for two consecutive ruptures but the amount of offset at individual sites was similar adjacent individual patches 10 km or more in length failed singly during one event and in tandem during the other more complex cases of repetition may also represent the failure of several distinct patches the faults of the 1992 landers earthquake provide an instructive example of such complexity together these examples suggest that large earthquakes commonly result from the failure of one or more patches each characterized by a slip function that is roughly invariant through consecutive earthquake cycles the persistence of these slip patches through two or more large earthquakes indicates that some quasi invariant physical property controls the pattern and magnitude of slip these data seem incompatible with theoretical models that produce slip distributions that are highly variable in consecutive large events

seismic origin of the atacama desert boulder fields abstract extensive fields of large boulders are common around the base of hills in the atacama desert how these boulders are transported from nearby hillslopes is unclear given the lack of rainfall of the region here we document the central role of seismicity not runoff in transporting and smoothing 1 ton boulders all across the hyperarid core of the atacama desert the generally granitoid boulders emerge as corestones on hillslopes at an erosion rate of 0 1 1 m ma 1 thereafter physical and cosmogenic isotopic evidence suggests that boulders slide and bounce rather than roll down hills and onto adjacent flats in the transport process the largest boulders are split and the smaller ones are weathered to grus narrowing average boulder mass to 2 tons 3 at the base of hills the boulders bunch together and rub during the frequent earthquakes in the region producing distinctive smoothing around boulder mid sections and silt moats around the boulder bases our measurements show a strong correlation between boulder field density and rubbing and only when the density exceeds 60 70 does rubbing become common except for slow removal by rubbing the boulders seem to undergo no further erosion while in the flats exposure times for some boulders are 12 ma making them among the oldest continuously exposed features on the earth boulder rubbing is just one geologic feature among many in the atacama that underscore the role that seismicity probably plays in shaping landscapes of the waterless worlds of the solar system

desorption induced shear failure of coal bed seams during gas depletion the recovery of natural gas from coal bed seams is usually accompanied by a significant increase of permeability induced by coal matrix shrinkage and stress relaxation upon gas desorption this advantageous increase in permeability may be impaired sometimes by mechanical failure of the reservoir rock and ensuing production of coal fines near wellbore stress concentration and reduction of lateral stresses are known to promote shear failure during depletion in oil and gas reservoir formations yet conventional analyses have shown limited success in predicting coal failure since other chemo physical mechanisms may be responsible in enhancing the conditions towards mechanical failure in the coal bed reservoir rock we show a set of triaxial experiments involving gas desorption from coal cores under zero lateral strain condition radial stress measured and controlled and constant total vertical stress meant to simulate the stress path during production far from the wellbore co2 is used as surrogate fluid for ch4 the experimental data indicates that desorption can significantly help reduce lateral stress and increasing deviatoric stress until shear failure occurs the results suggest that depletion induced shear failure is much more likely to occur in coal seams than in conventional non sorbing reservoir rocks the adsorptive mechanical coupling turns out to be a key phenomenon in the process numerical simulations at the representative elementary volume scale adopting a double porosity poromechanical model support the experimental findings and permit calculating a critical gas pressure for shear failure to happen this emergent phenomenon is comparable to the outcome of other situations such as mineral dissolution or thermal contraction where shrinkage relaxes lateral stress and acts as an intensifying driver for promoting shear failure within the reservoir rock coupled numerical simulation is needed to include near wellbore effects and validate our findings with actual field observations a thorough understanding of the coupled response of coal seams is necessary to enhance reservoir management and mitigate the effects of coal failure on fines production

young displacements on the atacama fault system northern chile from field observations and cosmogenic 21ne concentrations 1 we present the first numerical age constraint for young deformation of the atacama fault system afs in northern chile the young activity of the afs is expressed by several fault scarps which affects alluvial fan sediments of the eastern side of the coastal cordillera 23 30 23 42 s detailed mapping of alluvial fans reveals a complex relationship between fault motion erosion and alluvial fan development an older group of alluvial fans became inactive prior to the scarp formation younger alluvial fans arising directly from feeder channels and entrenched in the fault scarps posts date the scarp formation the youngest slip on the afs is recorded by headward eroding channels entrenched across the scarp which are in turn displaced vertically 0 3 0 5 m by the fault quartz fragments in four sites on the older inactive fan group were analyzed for cosmogenic 21ne concentrations yielding an average age of 424 151 ka the upper limit for the recent activity of the fault combined with the height of fault scarp we calculate a 0 01 mm yr minimum vertical fault slip rate thus young displacement on the afs is quaternary in age and confined to the late pleistocene