inversion for seismic slip rate history and distribution with stabilizing constraints application to the 1986 andreanof islands earthquake we develop and present a method of inverting seismograms including their absolute amplitudes to obtain the complete seismic slip time history and distribution using the method of linear programming a rectangular fault is discretized into cells and the source duration into time steps the inversion for the slip rate distribution on the fault as a function of time reduces to the solution of a system of linear equations the influence on the solution of constraining different source parameters such as the sign of the slip rate and the seismic moment is investigated it is found that the constraint of positiveness of slip rate and the constraint that the seismic moment determined from the solution should be close to that obtained from the centroid moment tensor cmt solution are very strong constraints and are essential to obtaining a physically reasonable solution since the inverse problem is unstable instead of presenting only one particular solution we examine several solutions equally well fitting the data for all practical purposes we find that when both constraints are applied the solution becomes quite stable the method is applied to a data set consisting of the vertical component of available digitally recorded teleseismic p waves at stations within a chosen distance window for the 1986 andreanof islands earthquake mw 8 0 the preferred solution is the one in which the slip rate is constrained to be positive and the moment is set to the cmt value the average rupture speed in the 90 km segment to the east of the hypocenter was 3 2 km s and in the 190 km section to the west was 2 km s the maximum slip in the area of large moment release to the west was 5 m and the maximum slip rate which occurs in the same place as the maximum slip was 6 5 m s the slip distribution on the fault shows a corrugated pattern with the long axis in the direction of the plate convergence rather than normal to the arc which was the slip vector direction for the earthquake with most of the slip occurring pn a region of the fault to the west of the rupture nucleation zone this region continued to slip for about 55 s the total source duration being about 80 s the results of this analysis suggest that the long term motion on this portion of the aleutian arc is indeed in the direction of plate convergence

finite faults and inverse theory with applications to the 1979 imperial valley earthquake abstract using a representation theorem from elastodynamics subsurface slip on a known fault is formulated as the solution to an inverse problem in which recorded surface ground motion is the data two methods of solution are presented the least squares method which minimizes the squared differences between theory and data and the constrained least squares method which simultaneously maintains a set of linear inequalities instabilities in the solution are effectively eliminated in both methods and the sensitivity of the solution to small changes in the data is quantitatively stated the inversion methodology is applied to 77 components of near field ground acceleration recorded during the 15 october 1979 imperial valley earthquake the faulting is constrained to propagate bilaterally away from the epicenter at an average velocity of 90 per cent of the shear wave speed on a vertical fault plane extending from the surface to 10 km depth inequality constraints are used to keep the faulting sequence physically reasonable by maintaining right lateral motion and positive slip velocity the preferred solution is stable and provides a good fit to the data it is also realistic and consistent with observed surface offsets and independent estimates of seismic moment

the hongqiaocun site the earliest evidence of ancient flood sedimentation of the water conservancy facilities in the chengdu plain china abstract the earliest water conservancy facilities in the chengdu plain were found at the hongqiaocun site of about 4 0 ka before present nearly 2 000 years earlier than the world famous dujiangyan irrigation project in order to understand the background of the construction of the water conservancy project we sampled and analyzed the ancient river profile ts20w13 near the water conservancy facilities sedimentology demonstrated that the 4th to 6th layers of the ts20w13 profile were the strongest stage of hydrodynamic force in the river the zr rb and ba nb values indicated that the 4th to 7th layers might have been those layers of a time of frequent flooding in this ancient river the results of zircon psephicity analysis also showed that the psephicity of the zircon at the 4th to 6th layers were the best indicating that along this stage of the river the average transporting force was the strongest according to the osl dating results and the above analysis at around 4 0 ka bp the hongqiaocun site was in the midst of a flood prone period which was synchronous with the ancient flood records of the yangtze river and yellow river basin the increase in flooding during this period might be related to the aggravation of climatic fluctuation by about 4 0 ka bp in the context of the above environmental background the ancient people at the hongqiaocun site built water conservancy facilities to withstand floods

constraining earthquake source inversions with gps data 2 a two step approach to combine seismic and geodetic data sets 1 we present a new method to combine static and wavefield data to image earthquake ruptures our combined inversion is a two step procedure following the work of hernandez et al 1999 and takes into account the differences between the resolutions of the two data sets the first step consists of an inversion of the static field which yields a map of slip amplitude this inversion exploits a special irregular grid that takes into account the resolution of the static data the second step is an inversion of the radiated wavefield it results in the determination of the time evolution of slip on the fault in the second step the slip amplitude is constrained to resemble the static slip amplitude map inferred from the gps inversion using this combined inversion we study the source process of the 2004 m6 parkfield california earthquake we conclude that slip occurred in two main regions of the fault each of which displayed distinct rupture behaviors slip initiated at the hypocenter with a very strong bilateral burst of energy here slip was localized in a narrow area approximately 10 km long the rupture velocity was very fast 3 5 km s and slip only lasted a short period of time 1 s then the rupture proceeded to a wider region 12 20 km northwest of the hypocenter here the earthquake developed in a more moderated way the rupture velocity slowed to 3 0 km s and slip lasted longer 1 2 s the maximum slip amplitude was 0 45 m

fragile landscapes fragile civilizations how climate determined societies in the pre columbian south peruvian andes abstract this paper presents alternating periods of geo ecological fragility and stability in a highly sensitive environmental setting the desert margin area of southern peru 14 5 s there we have to state that fragility was dominantly triggered by climatic changes which induced several oscillations of the desert margin during the mid holocene the study area received the holocene maximum of precipitation soil formation occurred and the desert retreated as loess paleosoil formation documents in contrast the titicaca region further south east experienced extreme drought at that time this regional antagonism between humid and dry conditions was a result of meridional shifts in moisture transport across the andes and occurred also during pre columbian times considering a coincidence between environmental and cultural changes we state that success and decline of civilizations were dominated by hydrological oscillations triggering fertility as well as a critical loss of natural resources fragile periods i e periods of geomorphological activity occurred contemporaneous with cultural transitions in response to spatial changing resources cultural foci were shifted so the success of pre columbian civilizations was closely coupled to areas of geo ecological favorability which were directly controlled by distinct regional impacts of large scale circulation mechanisms including el nino southern oscillation enso this spatial view on non uniform environmental and cultural changes has not been thoroughly considered before therefore for the first time this paper offers geomorphological evidence for diachronous andean agri cultural development which was geographically determined

abrupt variations of indian and east asian summer monsoons during the last deglacial stadial and interstadial abstract the phase relationship between the indian summer monsoon ism and the east asian summer monsoon easm during the last deglaciation remains controversial here we reconstruct a 15 000 year plant cellulose 13 c proxy record for the ism from the yuexi peat bog in southwestern china the record shows that the ism abruptly decreases during the younger dryas yd stadial and abruptly increases during the bolling allerod ba interstadial a comparison of the yuexi record with other related proxy climate records reveals two types of phenomena first the strengths of the two asian monsoons are inversely related during the yd stadial i e the ism strength decreases and the easm increases during this period the southern chinese mainland consisted of a wide arid zone while the northern chinese mainland was much wetter the arid zone in southern china resulted from two different types of monsoon processes the abnormal northward extension of the easm rain belt leading to less rainfall in southeast china or an illusion that the easm weakened the other process is a real weakening of the ism second during the ba interstadial the strengths of both the ism and easm clearly increased however the maximum strengths appear to have occurred in the allerod period during this period the entire chinese mainland both northern and southern experienced wet conditions the abnormal climate pattern of wet in the north and dry in the south during the yd stadial occurs because of the combined effects of the strengthened easm intensified westerlies and weakened ism which could be attributed to the response to the abrupt cooling in the high northern latitudes and to the el nino like activity in the equatorial pacific the widespread wet climate during the ba interstadial may be related to an abrupt increase in the greenhouse gases ghgs concentrations in the atmosphere and to the la nina like activity in the equatorial pacific these results contribute to a better understanding of the response of the asian monsoon to global changes and present a geo historical scenario for understanding the east asian hydrological variations in the current global warming phase

the 2004 mw6 0 parkfield california earthquake inversion of near source ground motion using multiple data sets on 28 september 2004 the m w 6 0 parkfield earthquake became the most densely recorded earthquake for near source ground motion to infer the kinematic nature of this event we invert the strong motion data the non linear global inversion yields slip amplitude slip rake average rupture velocity and rise time over the fault by using subsets of the data we study the dependence of the kinematic solutions on data input the inversions reveal that the slip amplitude was less than 0 65 m and outline two major areas of slip one that laterally surrounds the hypocenter preferentially extending to its se the other 10 to 20 km nw of the hypocenter at a depth between 2 and 8 km the slip amplitude we obtain for each point on the fault varies less than 0 15 m depending on data set used the rake angle variability is less than 40 degrees

interruptions of the ancient shu civilization triggered by climate change or natural disaster environmental proxies of a stable carbon isotope total organic carbon free iron oxide and particle size distribution in sediments as well as the stable carbon and oxygen isotopes in fossil human and animal teeth were used to reconstruct the history of climate change and natural disasters near the jinsha relic site and to track their effect on the ancient shu civilization which was established in the chengdu plain of southwest china during the late holocene in general the late holocene climate in the chengdu plain demonstrated a drying and cooling trend with evident cooler events 4100 and 2700 a bp which coincided with global climate changes the ancient shu civilization was interrupted twice and it included three stages the baodun 4700 3700 a bp the sanxingdui 3700 3150 a bp and the shi erqiao 3150 2600 a bp that were slightly related to the abrupt climate changes that resulted from the collapse of the classic sanxingdui civilization which was founded in a regional warm period the abrupt increase in sand content in the sediment from the jinsha site coincided with the palaeoearthquake and palaeodam burst in the longmen mountains when the baodun and shi erqiao desisted indicating that a flood had occurred due to a dam burst and may likely have caused the ancient civilization s destruction although the warm and humid climate flat terrain and rich water resources prompted the prosperity of the ancient towns of sanxingdui and jinsha frequent natural disasters such as powerful earthquakes landslide dams and outburst floods consistently affected the ancient shu inhabitants

late holocene drought responsible for the collapse of old world civilizations is recorded in an italian cave flowstone a severe drought in parts of low latitude northeastern africa and southwestern asia 4200 yr ago caused major disruption to ancient civilizations stable isotope trace element and organic fluorescence data from a calcite flowstone collected from the well watered alpi apuane karst of central western italy indicate that the climatic event responsible for this drought was also recorded in mid latitude europe although the timing of this event coincides with an episode of increased ice rafted debris to the subpolar north atlantic the regional ocean atmosphere response seems atypical of similar holocene ice rafting events furthermore comparison of the flowstone data with other regional proxies suggests that the most extreme part of the dry spell occurred toward the end of a longer term climate anomaly

monsoon source shifts during the drying mid holocene biomarker isotope based evidence from the core monsoon zone cmz of india abstract a better understanding of past variations of the indian summer monsoon ism that plays a vital role for the still largely agro based economy in india can lead to a better assessment of its potential impact under global climate change scenarios however our knowledge of spatiotemporal patterns of ism strength is limited due to the lack of high resolution continental paleohydrological records here we reconstruct centennial scale hydrological variability during the holocene associated to changes in the intensity of the ism based on a record of lipid biomarker abundances and compound specific stable isotopic composition of a 10 m long sediment core from saline alkaline lonar lake situated in the core monsoon zone of central india we identified three main periods of distinct hydrology during the holocene in central india the period between 10 1 and 6 cal ka bp was likely the wettest during the holocene lower average chain length acl index values 29 4 28 6 and negative 13 c wax values 34 8 to 27 8 of leaf wax n alkanes indicate the dominance of woody c 3 vegetation in the catchment and negative d wax values concentration weighted average 171 to 147 suggest a wet period due to an intensified monsoon after 6 cal ka bp a gradual shift to less negative 13 c wax values particularly for the grass derived n c 31 and appearance of the triterpene lipid tetrahymanol generally considered as a marker for salinity and water column stratification mark the onset of drier conditions at 5 1 cal ka bp an increasing flux of leaf wax n alkanes along with the highest flux of tetrahymanol indicate a major lowering of the lake level between 4 8 and 4 cal ka bp we find evidence for a transition to arid conditions indicated by high and strongly variable tetrahymanol flux in addition a pronounced shift to less negative 13 c wax values in particular for n c 31 25 2 to 22 8 during this period indicates a change of dominant vegetation to c 4 grasses in agreement with other proxy data such as deposition of evaporite minerals we interpret this period to reflect the driest conditions in the region during the last 10 1 ka this transition led to protracted late holocene arid conditions after 4 ka with the presence of a permanent saline lake supported by the sustained presence of tetrahymanol and more positive average d wax values 122 to 141 a late holocene peak of cyanobacterial biomarker input at 1 3 cal ka bp might represent an event of lake eutrophication possibly due to human impact and the onset of cattle livestock farming in the catchment a unique feature of our record is the presence of a distinct transitional period between 4 8 and 4 cal ka bp which was characterized by some of the most negative d wax values during the holocene up to 180 when all other proxy data indicate the driest conditions during the holocene these negative d wax values can as such most reasonably be explained by a shift in moisture source area and or pathways or rainfall seasonality during this transitional period we hypothesize that orbital induced weakening of the summer solar insolation and associated reorganization of the general atmospheric circulation as a possible southward displacement of the tropical rainbelt led to an unstable hydroclimate in central india between 4 8 and 4 ka our findings shed light onto the sequence of changes during mean state changes of the monsoonal system once an insolation driven threshold has been passed and show that small changes in solar insolation can be associated with major hydroclimate changes on the continents a scenario that may be relevant with respect to future changes in the ism system

what the exercise of the spice source inversion validation blindtest 1 did not tell you summary uncertainties of earthquake finite fault inversions based upon strong motion data are investigated using the source inversion validation blindtest 1 exercise of the spice seismic wave propagation and imaging in complex media a european network project motivated by previous counterintuitive results the distribution of slip and the shapes of asymmetric slip rate functions are simultaneously inverted by matching 10 or 33 broad band three component velocity waveforms within the period ranging from 0 02 to 2hz using a finite fault method that carries out the waveform inversion in the wavelet domain the effects of subfault size data noise and the number of stations have been explored our results suggest 1 although there are inevitable discrepancies between the inverted model and the target model because of ignoring the spatial slip variations within individual subfaults the fault slip and rise time distributions can be well constrained even with the data including large gaussian noise 2 it is crucial for source studies to develop new inversion schemes that can properly honour the frequency and time dependent energy distribution of seismic radiation and data noise for instance inversions using the variance reduction function of velocity waveforms as the objective function have low sensitivities to the total seismic moment and peak slip 3 although the relative value of the objective function is guided in the inversion the absolute value of the objective function cannot be used to evaluate the quality of an inverted model 4 because the source inversion is based on surface observations the spatiotemporal resolution of source inversion is affected not only by the data quality but also by the earthquake itself for vertical strike slip faults the along strike resolution is better than that along the downdip direction

rupture process and energy budget of the 29 july 2008 mw 5 4 chino hills california earthquake the source model of the 2008 m w 5 4 chino hills california earthquake is constrained using near field seismic body waves recorded by the california integrated seismic network cisn finite fault inversions are preformed for the two fault models based on the nodal planes derived from the cisn moment tensor solution the northeast dipping plane strike 289 dip 62 which has a similar strike as the nearby whittier fault is chosen as the causative fault because it fits the data significantly better our inversion result indicates that the majority of the chino hills earthquake rupture occurred in a compact area in particular 48 of the total seismic moment 1 6 10 17 nm was released by the failure of a 1 8 km 2 asperity located east of the hypocenter in a short time window from 0 4 to 0 8 s after the rupture initiation the average slip is approximately 0 5 m but the maximum slip is 1 8 m the average rupture velocity is 1 9 km s the static stress drop calculated using the slip model is up to 80 mpa and the average stress drop changes from 19 to 38 mpa depending on the average schemes the weighted average slip velocity is 6 5 m s for entire rupture and is 11 m s for the east asperity the inferred available energy and radiated energy are 8 10 13 j and 2 5 10 13 j respectively radiation efficiency is then 0 31 which is moderately low compared with previous earthquakes but consistent with the inferred high average fracture energy density ranging from 6 5 to 14 8 mj m 2

nonlinear dynamic rupture inversion of the 2000 western tottori japan earthquake 1 we have developed a systematic nonlinear inversion method for estimating rupture propagation and the underlying dynamic parameters for large historical earthquakes the rupture modeling is carried out using a three dimensional finite difference method and the inversion is implemented by a neighbourhood algorithm minimizing the misfit between computed and observed near fault seismograms we test the method by estimating the stress drop within 32 regions on the causative fault for the 2000 magnitude 6 6 western tottori japan earthquake while the dynamic models show both similarities and differences with the conventional kinematic models our method provides an ensemble of physically correct models with plausible rupture propagation for the earthquake

the chemical and hydrological evolution of an ancient potash forming evaporite basin as constrained by mineral sequence fluid inclusion composition and numerical simulation the chemical evolution of the brine in a potash evaporite basin has been investigated by x ray microanalysis of frozen primary inclusions trapped in halite a computer program based on thermodynamic equilibrium and mass balance principles has been used to simulate evaporation paths the comparison between the results of calculations the observed mineralogy and mineral sequence and the solute content in fluid inclusions has placed constraints on the hydrological evolution of the basin the upper eocene basin of navarra southern pyrenees spain began as a marine basin evolving from a moderate to a high degree of restriction depositing first a basai anhydrite horizon and then a thick sequence of massive halite an additional inflow of cacl2 in the basin during seawater evaporation is proposed as the process responsible for the sulfate depletion required for sylvite instead of mg sulfates to form mixing of seawater with continental waters bacterial sulfate reduction and in situ dolomitization are discarded the basin subsequently closed to the sea and evolved with decreasing volume alternating bands of clays halite sylvite and then clays halite carnallite were deposited under the influence of seasonal continental recharge before reaching total desiccation the residual brine was diluted by continental water the basin then evolved under an endoreic regime where continental recharge and the recycling of previously formed halite led to deposition of alternating beds of clays and halite

repeating earthquake finite source models strong asperities revealed on the san andreas fault 1 we investigate the rupture process of a sequence of repeating mw 2 1 earthquakes on the san andreas fault in parkfield spanning the occurrence of the september 28 2004 mainshock by inverting seismic moment rate functions obtained from empirical green s function deconvolution the results show that these events have extremely concentrated slip patches with radii on the order of 10 20 m with peak slip between 8 4 and 11 4 cm the rupture speed and rise time are consistent with values of larger earthquakes the spatial distribution of stress drop for the events shows low average values 2 5 5 6 mpa and very large peak values of 66 7 93 9 mpa the results show that strong asperities can exist at small scales on an otherwise weak fault and helps reconcile differences between traditional spectra based and tectonic loading methods for determining the stress drop of small repeating earthquakes

holocene environmental change and its impacts on human settlement in the shanghai area east china abstract archaeological excavations and environmental archaeological studies over many years in the shanghai area have provided a wealth of information for holocene environmental changes growth and decline of human settlements and man land interaction distribution of archaeological sites between 7000 and 3000 cal yr bp indicates a regression process and a southward advance of the coastline in the study area temporal and spatial analyses of 14 c dates for archaeological sites shell ridges buried trees and peat suggest that holocene environmental changes may well have been a major cause of the rise and fall of human settlements and their civilization a relative sea level curve of the shanghai area was derived from dated shell ridges and peat and correlates well with the reconstructed sea level curves of the yangtze delta and east china the development of human settlements was interrupted at least four times in the shanghai area matching four periods of high sea level peat accumulation and increase in shell ridges after which neolithic communities moved onto the plain and reclaimed their lowlands for rice cultivation the chenier ridges played an important role in sheltering the neolithic settlers the collapse of liangzhu culture about 4000 cal yr bp was followed by the less developed maqiao culture these studies suggest that extreme environmental and hydrological conditions such as terrestrial inundation caused by sea level rise and heavy rainfall contributed to the cessation of paddy exploitation and to the social stress that led to the liangzhu culture demise

fluvial chronology in the east european plain over the last 20 ka and its palaeohydrological implications abstract a database containing 983 absolute ages of fluvial deposits was interpreted in palaeohydrological terms and 646 dates were found associated with 754 local palaeofluvial events geomorphic or sedimentological traces of changing fluvial activity combined probability density functions of high and low activity dates were used to detect time intervals of different palaeohydrological status after low fluvial activity during lgm two palaeohydrological epochs were designated extremely high activity in the end of mis 2 ca 18 11 7 ka before ce 2000 b2k and much lower activity in the holocene within the holocene two hierarchical levels of hydroclimatic variability were designated according to their duration and magnitude regional palaeohydrological phases centuries to few millennia and regional palaeofluvial episodes decades to few centuries tendency is rather clear of activity lowering in the first half and rise in the second half of the holocene extremes within the palaeohydrological phases were designated as 19 palaeofluvial episodes 7 high activity ha episodes 8 low activity stability la episodes and 4 contrast or complex ca episodes in most cases changes of fluvial activity were most likely induced by changing amounts of spring snowmelt runoff most distinct correlation of temperature and hydrological regimes was found in the late holocene high fluvial activity corresponded to cold climatic phases little ice age low activity to warm phases medieval climatic optimum current climate warming the suggested fluvial chronology was compared with independent hydroclimatic archives such as palaeosoils and lake levels correlation with soil formation alluviation epochs was found very close with some exceptions in the early holocene correspondence of fluvial activity to the caspian sea level changes is rather high in the second part of the holocene and is poor before 4 5 ka b2k which can be explained by insufficient data behind both types of reconstructions correlation of changes in fluvial activity within a west east transect over europe revealed relatively poor correlation in the early and mid holocene and much higher synchronism since 3 0 ka b2k which may indicate increasing role of westerlies in controlling european climates in the late holocene throughout the whole holocene changes of fluvial activity over eep were governed by natural climate forcing until the last few centuries when land use changes induced accelerated hillslope and gully erosion

constraining earthquake source inversions with gps data 1 resolution based removal of artifacts 1 we present a resolution analysis of an inversion of gps data from the 2004 mw 6 0 parkfield earthquake this earthquake was recorded at thirteen 1 hz gps receivers which provides for a truly coseismic data set that can be used to infer the static slip field we find that the resolution of our inverted slip model is poor at depth and near the edges of the modeled fault plane that are far from gps receivers the spatial heterogeneity of the model resolution in the static field inversion leads to artifacts in poorly resolved areas of the fault plane these artifacts look qualitatively similar to asperities commonly seen in the final slip models of earthquake source inversions but in this inversion they are caused by a surplus of free parameters the location of the artifacts depends on the station geometry and the assumed velocity structure we demonstrate that a nonuniform gridding of model parameters on the fault can remove these artifacts from the inversion we generate a nonuniform grid with a grid spacing that matches the local resolution length on the fault and show that it outperforms uniform grids which either generate spurious structure in poorly resolved regions or lose recoverable information in well resolved areas of the fault in a synthetic test the nonuniform grid correctly averages slip in poorly resolved areas of the fault while recovering small scale structure near the surface finally we present an inversion of the parkfield gps data set on the nonuniform grid and analyze the errors in the final model

holocene climate and cultural evolution in late prehistoric early historic west asia abstract the precipitation climatology and the underlying climate mechanisms of the eastern mediterranean west asia and the indian subcontinent are reviewed with emphasis on upper and middle tropospheric flow in the subtropics and its steering of precipitation holocene climate change of the region is summarized from proxy records the indian monsoon weakened during the holocene over its northernmost region the ganges and indus catchments and the western arabian sea southern regions the indian peninsula do not show a reduction but an increase of summer monsoon rain across the holocene the long term trend towards drier conditions in the eastern mediterranean can be linked to a regionally complex monsoon evolution abrupt climate change events such as the widespread droughts around 8200 5200 and 4200 cal yr bp are suggested to be the result of altered subtropical upper level flow over the eastern mediterranean and asia the abrupt climate change events of the holocene radically altered precipitation fundamental for cereal agriculture across the expanse of late prehistoric early historic cultures known from the archaeological record in these regions social adaptations to reduced agro production in both dry farming and irrigation agriculture regions are visible in the archaeological record during each abrupt climate change event in west asia chronological refinement in both the paleoclimate and archaeological records and transfer functions for both precipitation and agro production are needed to understand precisely the evident causal linkages

chemical and physical weathering in the min jiang a headwater tributary of the yangtze river abstract the min jiang is a major headwater tributary of the yangtze chang jiang its source is in the undeveloped eastern tibetan plateau but it flows through the heavily populated sichuan four rivers basin on its way to join the yangtze main channel the dissolved major element composition was determined in the tibetan headwaters at the rising stage and at four hydrologic stations in a monthly time series the min jiang is alkaline and has high dissolved load compared to other world rivers carbonate weathering dominates especially in the source region of the min jiang main channel and silicate weathering and evaporite dissolution gain some importance in the dadu he tributary the si na k ratios of the dissolved load and the clay mineralogy of the bed material suggest that silicate weathering in the watershed is superficial i e soluble cations are being preferentially leached many major elements show lower concentrations at high summer discharge but there is also additional input such that the concentration discharge relationship is not purely a result of dilution the discharge weighted total dissolved solid tds flux based on data from the three upstream monitoring stations is 10 10 6 tons year 6 of the yangtze at mouth and the chemical denudation rate as measured by tds yield is 115 tons km 2 year for the min jiang higher than the average yangtze basin 85 tons km 2 year the common extrapolation using annual average discharge and spot sampling of dissolved and suspended material during rising or falling stage can reasonably estimate chemical fluxes to 20 but seriously underestimate the physical flux sampling the peak flash flow is critical for the suspended particulate material concentrations of so 4 cl and ca are significantly elevated as the river debouches onto the populated sichuan basin

a mid late holocene flood record from the alluvial reach of the mahi river western india abstract flooding of rivers in india is linked with the peak monsoons investigating the linkage between monsoonal patterns and flood history of various rivers is therefore of fundamental importance in the indian context in the present study the slackwater deposits in the alluvial reaches of the mahi river basin western india have been documented these occur in the ravines incised during the early holocene on an alluvial surface comprising sediments of late pleistocene age the slackwater deposits occur at elevations up to 20 m from the present river level and extend to about 500 m inland the carbonate rich sediments forming the ravine cliffs have provided bank stability and the dissections in the ravines have helped in the accumulation of slackwater deposits due to backflooding of the floodwater from the main channel recent gullies have incised the sediments and exposed deposits related to major flood events the best exposures of slackwater deposits have been observed at dodka the sediment succession of the slackwater deposits is dominated by bedsets and laminasets of silt and sand separated by colluvial sediments four events of flood deposition occurred during the mid to late holocene two units of slackwater deposits swd 2 and 4 have been dated by irsl at 4 6 1 ka and 1 7 0 5 ka the stratigraphy of these deposits indicates that the first two slackwater units swd1 and swd2 have resulted due to flooding in a regime of intense monsoon the other two units however represent extreme high magnitude floods in a period of low average precipitation

spatial and temporal distribution of slip for the 1992 landers california earthquake we have determined a source rupture model for the 1992 landers earthquake m w 7 2 compatible with multiple data sets spanning a frequency range from zero to 0 5 hz geodetic survey displacements near field and regional strong motions broadband teleseismic waveforms and surface offset measurements have been used explicitly to constrain both the spatial and temporal slip variations along the model fault surface our fault parameterization involves a variable slip multiple segment finite fault model which treats the diverse data sets in a self consistent manner allowing them to be inverted both independently and in unison the high quality data available for the landers earthquake provide an unprecedented opportunity for direct comparison of rupture models determined from independent data sets that sample both a wide frequency range and a diverse spatial station orientation with respect to the earthquake slip and radiation pattern in all models consistent features include the following 1 similar overall dislocation patterns and amplitudes with seismic moments of 7 to 8 10 26 dyne cm seismic potency of 2 3 to 2 7 km 3 2 very heterogeneous unilateral strike slip distributed over a fault length of 65 km and over a width of at least 15 km though slip is limited to shallower regions in some areas 3 a total rupture duration of 24 sec and an average rupture velocity of 2 7 km sec and 4 substantial variations of slip with depth relative to measured surface offsets the extended rupture length and duration of the landers earthquake also allowed imaging of the propagating rupture front with better resolution than for those of prior shorter duration strike slip events our imaging allows visualization of the rupture evolution including local differences in slip durations and variations in rupture velocity rupture velocity decreases markedly at shallow depths as well as near regions of slip transfer from one fault segment to the next as rupture propagates northwestward along the multiply segmented fault length the rupture front slows as it reaches the northern limit of the johnson valley landers faults where slip is transferred to the southern homestead valley fault an abrupt acceleration is apparent following the transfer this process is repeated and is more pronounced as slip is again passed from the northern homestead valley fault to the emerson fault although the largest surface offsets were observed at the northern end of the rupture our modeling indicates that substantial rupture was also relatively shallow less than 10 km in this region

influence of climate change on the evolution of ancient culture from 4500 to 3700 cal yr bp in the chengdu plain upper reaches of the yangtze river china abstract numerous environmental archaeology studies have been undertaken in the middle and lower reaches of the yangtze river but limited research has been carried out in the upper reaches of the yangtze river uyr during the period of the baodun culture approximately 4500 3700 cal yr bp the inhabitants of the chengdu plain cdp in the uyr of southwestern china were confronted with a dynamic climate archaeological sites including 9 walled sites located in a relatively small region were built during the migration process this paper attempts to demonstrate the linkage between the evolutionary history of the baodun culture and paleoclimate change subsistence strategies during the baodun period such as farming tool use and food resources were investigated furthermore the spatiotemporal distribution of the archaeological sites the construction method of the sites walls and the growth of weeds were examined and assessed based on archaeological excavations and the literature the ancient water network at the baodun site was investigated based on auger surveys and borehole data by comparing multiple paleoclimatic proxies from regions mainly controlled by the indian monsoon we found that 1 the drying and cooling climate conditions were responsible for the increases of proportions of millet and supplementary food resources and for the transformation of tool assemblages during the late baodun period 2 the increasing numbers of flood events were caused by the weakening of the monsoon and the dramatic climate during the baodun period and the interconnected river networks at low elevations in the cdp exacerbated the impact of flooding which may have partially caused the frequent human migration and the construction method of the site walls 3 the baodun people that originally lived in the southwestern and western cdp were forced to gradually migrate to higher elevations in the northern and central territories because of the rapid climate change and 4 the topography and river grade also influenced human migration and settlement selection climate deterioration hindered the sustainable development of the baodun culture and eventually caused it to decline common subsistence strategies in human history such as site location migration flood control methods agricultural changes and food diversification played important roles in the baodun people s adaptation to climate change

slip history of the 2003 san simeon earthquake constrained by combining 1 hz gps strong motion and teleseismic data 1 the slip history of the 2003 san simeon earthquake is constrained by combining strong motion and teleseismic data along with gps static offsets and 1 hz gps observations comparisons of a 1 hz gps time series and a co located strong motion data are in very good agreement demonstrating a new application of gps the inversion results for this event indicate that the rupture initiated at a depth of 8 5 km and propagated southeastwards with a speed 3 0 km sec with rake vectors forming a fan structure around the hypocenter we obtained a peak slip of 2 8 m and total seismic moment of 6 2 10 18 nm we interpret the slip distribution as indicating that the hanging wall rotates relative to the footwall around the hypocenter in a sense that appears consistent with the shape of the mapped fault trace index terms 1242 geodesy and gravity seismic deformations 7205 7212 seismology earthquake ground motions and engineering 8123 tectonophysics dynamics seismotectonics citation ji c k m larson y tan k w hudnut and k choi 2004 slip history of the 2003 san simeon earthquake constrained by combining 1 hz gps strong motion and teleseismic data geophys res lett 31 l17608 doi 10 1029 2004gl020448

mid to late holocene climate change an overview the last 6000 years are of particular interest to the understanding of the earth system because the boundary conditions of the climate system did not change dramatically in comparison to larger glacial interglacial changes and because abundant detailed regional palaeoclimatic proxy records cover this period we use selected proxy based reconstructions of different climate variables together with state of the art time series of natural forcings orbital variations solar activity variations large tropical volcanic eruptions land cover and greenhouse gases underpinned by results from general circulation models gcms and earth system models of intermediate complexity emics to establish a comprehensive explanatory framework for climate changes from the mid holocene mh to pre industrial time the redistribution of solar energy due to orbital forcing on a millennial timescale was the cause of a progressive southward shift of the northern hemisphere nh summer position of the intertropical convergence zone itcz this was accompanied by a pronounced weakening of the monsoon systems in africa and asia and increasing dryness and desertification on both continents the associated summertime cooling of the nh combined with changing temperature gradients in the world oceans likely led to an increasing amplitude of the el nin o southern oscillation enso and possibly increasingly negative north atlantic oscillation nao indices up to the beginning of the last millennium on decadal to multi century timescales a worldwide coincidence between solar irradiance minima tropical volcanic eruptions and decadal to multi century scale cooling events was not found however reconstructions show that widespread decadal to multi century scale cooling events accompanied by advances of mountain glaciers occurred in the nh e g in scandinavia and the european alps this occurred namely during the little ice age lia between ad w1350 and 1850 when the lower summer insolation in the nh due to orbital forcing coincided with solar activity minima and several strong tropical volcanic eruptions the role of orbital forcing in the nh cooling the southward itcz shift and the desertifi cation of the sahara are supported by numerous model simulations other simulations have suggested that the fingerprint of solar activity variations should be strongest in the tropics but there is also evidence that changes in the ocean heat transport took place during the lia at high northern latitudes with possible additional implications for climates of the southern hemisphere sh

climate change at the 4 2 ka bp termination of the indus valley civilization and holocene south asian monsoon variability 1 planktonic oxygen isotope ratios off the indus delta reveal climate changes with a multi centennial pacing during the last 6 ka with the most prominent change recorded at 4 2 ka bp opposing isotopic trends across the northern arabian sea surface at that time indicate a reduction in indus river discharge and suggest that later cycles also reflect variations in total annual rainfall over south asia the 4 2 ka event is coherent with the termination of urban harappan civilization in the indus valley thus drought may have initiated southeastward habitat tracking within the harappan cultural domain the late holocene drought cycles following the 4 2 ka bp event vary between 200 and 800 years and are coherent with the evolution of cosmogenic 14c production rates this suggests that solar variability is one fundamental cause behind holocene rainfall changes over south asia

a high resolution absolute dated holocene and deglacial asian monsoon record from dongge cave china abstract we present a continuous record of the asian monsoon over the last 16 ka from 18o measurements of stalagmite calcite over 900 oxygen isotopic measurements providing information on shifts in monsoon precipitation are combined with a chronology from 45 precise 230th dates 18o and therefore asian monsoon intensity generally follows changes in insolation although changes in 18o are generally accommodated in abrupt shifts in contrast to smoothly varying insolation indicating that threshold effects may be important 18o decreased dramatically 3 at the start of the holocene 11 5 ka and remained low for 6 ka four positive 18o events centered at 11225 97 yr bp 1 05 10880 117 yr bp 1 15 9165 75 yr bp 1 4 and a double event centered at 8260 64 yr bp 1 1 and 8080 74 yr bp 1 0 punctuated this period of high monsoon intensity all four events correlate within error with climate changes in greenland ice cores thus the relationship between the asian monsoon and the north atlantic observed during the glacial period appears to continue into the early holocene in addition three of the four events correlate within error with outburst events from lake agassiz the decline of monsoon intensity in the mid late holocene is characterized by an abrupt positive shift in 18o which occurs at 3550 59 yr bp 1 1 in 100 yr in addition the holocene is punctuated by numerous centennial and multi decadal scale events amplitudes 0 5 to 1 up to half the amplitude of the glacial interstadial events seen in the last glacial period thus holocene centennial and multi decadal scale monsoon variability is significant although not as large as glacial millennial scale variability the monsoon shows a strong connection with northern south american hydrological changes related by changes in itcz position spectral analysis of the 18o record shows significant peaks at solar periodicities of 208 yr and 86 yr suggesting variation is influenced by solar forcing however there are numerous other significant peaks including peaks at el nino frequencies observed for high resolution portions of the record between 8110 and 8250 yr which suggest that changes in oceanic and atmospheric circulation patterns in addition to those forced by solar changes are important in controlling holocene monsoon climate in addition for this high resolution portion we observe a distinctive biennial oscillation of the asian monsoon which has been associated with the tropospheric biennial oscillation tbo

asian monsoon oscillations in the northeastern qinghai tibet plateau since the late glacial as interpreted from visible reflectance of qinghai lake sediments abstract qinghai lake is a large saline lake on the qinghai tibetan plateau of central asia that is effected by both the indian and asian monsoons we used reflectance spectroscopy to characterize the sediments in a 795 cm long core taken from the southeastern part of the lake sediment redness which is related to iron oxide content seems to monitor paleoclimatic changes in the core iron oxides appear to be eroded from nearby red beds or loess deposits and are transported by fluvial means into the lake thus redness increases at times of increased precipitation that is as monsoon strength increases our redness monsoon proxy shows climate changes on several times scales on a millennial scale it records humid conditions during the early and mid holocene from about 4200 to 2300 yr bp low redness values suggest a two millennial long dry period which in the late holocene is followed by a more humid period on a centennial scale the redness proxy records not only the little ice age but also the medieval warm period the dark ages cool period and the roman warm period time series analysis of the redness record indicates a 200 yr frequency which corresponds to the de vries solar cycle suggesting that in addition to insolation changes resulting from orbital variations solar forcing also results from cyclic changes in the sun s luminosity

holocene forcing of the indian monsoon recorded in a stalagmite from southern oman a high resolution oxygen isotope record from a thorium uranium dated stalagmite from southern oman reflects variations in the amount of monsoon precipitation for the periods from 10 3 to 2 7 and 1 4 to 0 4 thousand years before the present ky b p between 10 3 and 8 ky b p decadal to centennial variations in monsoon precipitation are in phase with temperature fluctuations recorded in greenland ice cores indicating that early holocene monsoon intensity is largely controlled by glacial boundary conditions after approximately 8 ky b p monsoon precipitation decreases gradually in response to changing northern hemisphere summer solar insolation with decadal to multidecadal variations in monsoon precipitation being linked to solar activity

slip history and dynamic implications of the 1999 chi chi taiwan earthquake we investigate the rupture process of the 1999 chi chi taiwan earthquake using extensive near source observations including three component velocity waveforms at 36 strong motion stations and 119 gps measurements a three plane fault geometry derived from our previous inversion using only static data ji et al 2001 is applied the slip amplitude rake angle rupture initiation time and risetime function are inverted simultaneously with a recently developed finite fault inverse method that combines a wavelet transform approach with a simulated annealing algorithm ji et al 2002b the inversion results are validated by the forward prediction of an independent data set the teleseismic p and sh ground velocities with notable agreement the results show that the total seismic moment release of this earthquake is 2 7 10 20 n m and that most of the slip occurred in a triangular shaped asperity involving two fault segments which is consistent with our previous static inversion the rupture front propagates with an average rupture velocity of 2 0 km s 1 and the average slip duration risetime is 7 2 s several interesting observations related to the temporal evolution of the chi chi earthquake are also investigated including 1 the strong effect of the sinuous fault plane of the chelungpu fault on spatial and temporal variations in slip history 2 the intersection of fault 1 and fault 2 not being a strong impediment to the rupture propagation and 3 the observation that the peak slip velocity near the surface is in general higher than on the deeper portion of the fault plane as predicted by dynamic modeling