detrital carbonate peaks on the labrador shelf a 13 7 ka template for freshwater forcing from the hudson strait outlet of the laurentide ice sheet into the subpolar gyre abstract the laurentide ice sheet lis was a large dynamic ice sheet in the early holocene the glacial events through hudson strait leading to its eventual demise are recorded in the well dated labrador shelf core md99 2236 from the cartwright saddle we develop a detailed history of the timing of ice sheet discharge events from the hudson strait outlet of the lis during the holocene using high resolution detrital carbonate ice rafted detritus ird 18o and sediment color data eight detrital carbonate peaks dcps associated with ird peaks and light oxygen isotope events punctuate the md99 2236 record between 11 5 and 8 0 ka we use the stratigraphy of the dcps developed from md99 2236 to select the appropriate r to calibrate the ages of recorded glacial events in hudson bay and hudson strait such that they match the dcps in md99 2236 we associate the eight dcps with h0 gold cove advance noble inlet advance initial retreat of the hudson strait ice stream hsis from hudson strait opening of the tyrrell sea and drainage of glacial lakes agassiz and ojibway the opening of foxe channel and retreat of glacial ice from foxe basin are represented by a shoulder in the carbonate data r of 350 years applied to the radiocarbon ages constraining glacial events h0 through the opening of the tyrell sea provided the best match with the md99 2236 dcps r values and ages from the literature are used for the younger events a very close age match was achieved between the 8 2 ka cold event in the greenland ice cores dcp7 8 15 ka bp and the drainage of glacial lakes agassiz and ojibway our stratigraphic comparison between the dcps in md99 2236 and the calibrated ages of hudson strait bay deglacial events shows that the retreat of the hsis the opening of the tyrell sea and the catastrophic drainage of glacial lakes agassiz and ojibway at 8 2 ka are separate events that have been combined in previous estimates of the timing of the 8 2 ka event from marine records sw iceland shelf core md99 2256 documents freshwater entrainment into the subpolar gyre from the hudson strait outlet via the labrador north atlantic and irminger currents the timing of freshwater release from the lis hudson strait outlet in md99 2236 matches evidence for freshwater forcing and lis icebergs carrying foreign minerals to the sw iceland shelf between 11 5 and 8 2 ka the congruency of these records supports the conclusion of the entrainment of freshwater from the retreat of the lis through hudson strait into the subpolar gyre and provides specific time periods when pulses of lis freshwater were present to influence climate

seismic hazard on the french riviera observations interpretations and simulations summary we present here a detailed analysis of a seismic data set recorded by a dense seismological network installed over 6 months in the southeast of france this experiment was set up at the boundary between the ligurian basin and the southern subalpine thrust belt the nice arc which is a complex tectonic region that undergoes low to moderate seismicity we recorded more than 500 microearthquakes among which 348 occurred exactly in the centre of the network during a very active seismic sequence that lasted mainly over 2 months we performed an absolute location of all of the events and calculated the magnitudes then we applied a cross correlation technique to gather similar events and to relocate relatively few of them this method revealed a very clear alignment of 19 events in a direction n120 oblique to the n20 general trend of seismicity focal mechanisms were determined for the four largest events and composite solutions for 32 smaller ones both the alignments of the earthquakes and the focal solutions revealed that two oblique segments of the fault were activated during the crisis the main segment 8 km long that was oriented nne with a left lateral strike slip movement is called the blausasc fault taking into account the tectonic evolution and the relationships between surface structures and the distribution of earthquakes and through a paleaoreconstruction of the tectonic evolution we propose that the blausasc fault is the hidden root of the peille laghet fault which has a mapped length of at least 15 km the smaller segment 0 6 km long that was activated during the crisis could be interpreted as an antithetic riedel fracture the active blausasc fault is located in a densely populated zone at only 10 km from the crowded cities of monaco and nice it is thus particularly interesting to analyse it for hazard assessment in the last section we present a simulation that is aimed at predicting what the ground motion in the city of nice would be like if an earthquake of magnitude 5 7 occurs on this fault for this we used the recordings of the largest event of the seismic sequence ml 3 2 and an empirical green s function summation scheme to simulate the ground motion at two stations situated in urban environments the values obtained show that especially on soft soil sites the effects of such an earthquake would be considerable in the city of nice

an 8000 year history of landscape climate and copper exploitation in the middle east the wadi faynan and the wadi dana national reserve in southern jordan abstract investigations of geomorphology geoarchaeology pollen palynofacies and charcoal indicate the comparative scales and significance of palaeoenvironmental changes throughout the holocene at the junction between the hyper arid hot wadi arabah desert and the front of the mediterranean belt mountains of edom in southern jordan through a series of climatic changes and episodes of intense mining and smelting of copper ores early holocene alluviation followed the impact of neolithic grazers but climate drove fluvial geomorphic change in the late holocene with a major arid episode corresponding chronologically with the little ice age causing widespread alluviation the harvesting of wood for charcoal may have been sufficiently intense and widespread to affect the capacity of intensively harvested tree species to respond to a period of greater precipitation deduced for the roman byzantine period a property that affects both taphonomic and biogeographical bases for the interpretation of palynological evidence from arid lands with substantial industrial histories studies of palynofacies have provided a record of human and climatic causes of soil erosion and the changing intensity of the use of fire over time the patterns of vegetational climatic change and geomorphic changes are set out for this area for the last 8000 years

a solar irradiance trigger for millennial scale abrupt changes in the southwest monsoon 1 marine sedimentary records of the last glacial from tropical monsoon latitudes indicate climate fluctuations comparable to rapid changes in 18o recorded in greenland synchronizing two high resolution sedimentary records from the oman and pakistan margins we resolve millennial scale reversals in sea surface temperature sst gradient sst across the arabian sea which directly correspond with the majority of dansgaard oeschger d o events for the last 65 kyr the relative amplitude of individual monsoon and d o events appears comparable suggesting coupled and at least hemispheric forcing to explore this quasi cyclic forcing we compare alkenone based geologic data with modern satellite derived sst estimates between sites interstadial conditions fall within the range of monsoons during the holocene but stadial conditions have no analogs following published associations between eurasian winter snow cover ewsc and monsoon rainfall and el nino southern oscillation enso events and anomalous ewsc we find a good correlation between the southern oscillation index soi and arabian sea sst throughout the modern data set an apparent 11 year cyclicity in the soi reveals an association between the monsoon soi and solar output variability the soi primarily tracks solar total irradiance but the soi monsoon linkage becomes nonlinear during excursions of the soi associated with el nino events strong el ninos coincide precisely with minimum solar irradiance during the solar cycle which we attribute to threshold behavior in tropical pacific ssts and associated trade wind strength we propose that both short term interannual decadal and long term centennial millennial changes in solar output are consistent with records of enso variability monsoon intensity and d o event timing

the implications of regional microseismic activities a lesson from 2008 ms 8 0 wenchuan earthquake abstract the ms 8 0 wenchuan earthquake has greatly perturbed the crustal stress in longmenshan fault zone lfz and its neighboring regions and hence significantly changed the regional seismicity pattern convectional coulomb stress change model based on half space dislocation source of layered elastic or viscoelastic crust can only provide brief reference to estimate the after shock sequences roughly in this study we apply the z test statistical method to examine the earthquake catalogue five years before and after this event to detect the changes of regional seismicity intensity and their statistical significance in lfz and its neighboring regions we analyze changes of the z values with respect to time and seismic magnitude in each region our results reveal that after the wenchuan earthquake seismicity intensity has significantly increased in eastern kunlun fault southern longmenshan fault longquanshan fault and huayingshan fault in sichuan basin but has significantly decreased in northern and central longmenshan fault vicinity of the songpan minjiang fault and fubianhe fault in bayankala block respectively seismicity rate change in northern and central anninghe zemuhe fault zone is not correlated with the wenchuan earthquake these results remain within 99 confidence level of the z test statistical method we compare our statistical analysis results with calculations of coseismic coulomb failure stress change due to the wenchuan earthquake from previous studies in most of the regions and fault zones the sign of the seismicity rate change agrees with the sign of the coulomb stress change

secondary aftershocks and their importance for aftershock forecasting the potential locations of aftershocks which can be large and damaging are often forecast by calculating where the mainshock increased stress we find however that the mainshock induced stress field is often rapidly altered by aftershock induced stresses we find that the percentage of aftershocks that are secondary aftershocks or aftershocks triggered by previous aftershocks increases with time after the mainshock if we only consider aftershock sequences in which all aftershocks are smaller than the mainshock the percentage of aftershocks that are secondary also increases with mainshock magnitude using the california earthquake catalog and monte carlo trials we estimate that on average more than 50 of aftershocks produced 8 or more days after m 5 mainshocks and more than 50 of all aftershocks produced by m 7 mainshocks that have aftershock sequences lasting at least 15 days are triggered by previous aftershocks these results suggest that previous aftershock times and locations may be important predictors for new aftershocks we find that for four large aftershock sequences in california an updated forecast method using previous aftershock data and neglecting mainshock induced stress changes can outperform forecasts made by calculating the static coulomb stress change induced solely by the mainshock manuscript received 20 november 2002

quantitative holocene climatic reconstructions for the lower yangtze region of china quantitative proxy based and high resolution palaeoclimatic datasets are scarce for the lower reaches of the yangtze river lyr basin this region is in a transitional vegetation zone which is climatologically sensitive and as a birthplace for prehistorical civilization in china it is important to understand how palaeoclimatic dynamics played a role in affecting cultural development in the region we present a pollen based and regionally averaged holocene climatic twin dataset for mean total annual precipitation pann and mean annual temperature tann covering the last 10 000 years for the lyr region this is based on the technique of weighted averaging partial least squares regression to establish robust calibration models for obtaining reliable climatic inferences the pollen based reconstructions generally show an early holocene climatic optimum with both abundant monsoonal rainfall and warm thermal conditions and a declining pattern of both pann and tann values in the middle to late holocene the main driving forces behind the holocene climatic changes in the lyr area are likely summer solar insolation associated with tropical or subtropical macro scale climatic circulations such as the intertropical convergence zone itcz western pacific subtropical high wpsh and el nino southern oscillation enso regional multi proxy comparisons indicate that the holocene variations in precipitation and temperature for the lyr region display an in phase relationship with other related proxy records from southern monsoonal china and the indian monsoon influenced regions but are inconsistent with the holocene moisture or temperature records from northern monsoonal china and the westerly dominated region in northwestern china overall our comprehensive palaeoclimatic dataset and models may be significant tools for understanding the holocene asian monsoonal evolution and for anticipating its future dynamics in eastern asia

stratigraphy and structure of the eocene memphis sand above the eastern margin of the reelfoot rift in tennessee mississippi and arkansas usa in total 1249 geophysical well logs were interpreted to map the stratigraphy and structure of the eocene memphis sand in west tennessee northwest mississippi and crittenden county arkansas where it overlies the southeastern margin of the reelfoot rift the memphis sand is a 300 m thick reworked fluvial sand deposited on a low relief subsiding plain with limited accommodation space the memphis sand has experienced syn and postdepositional faulting of four types in the region 1 west trending grabens were active during eocene claiborne deposition these grabens also appear to control modern drainage and thus may extend to the surface 2 the n33 e shelby faults pass through shelby county tennessee into northwest mississippi and extend to or near the surface they were right lateral normal faults during eocene memphis sand deposition but they became inverted reverse faults in the late eocene 3 the n67 e striking gibson faults are high angle normal and reverse faults with a component of right lateral strike slip these faults were active during memphis sand through lower cockfield deposition north of the hatchie graben and appear to be due to faulting above an outboard fault of the reelfoot rift 4 the n43 e striking lauderdale faults are high angle normal and reverse faults that reflect right lateral strike slip reactivation of the southeastern margin of the reelfoot rift the structure and stratigraphy revealed in this mapping indicate that the geology of the memphis sand is more complex than previously recognized faulting of the memphis sand and overlying sediments reveals potentially seismogenic faults in western tennessee eastern arkansas and northwestern mississippi this study provides fundamental data for future groundwater modeling and seismic hazard analysis

assessment of source probabilities for potential tsunamis affecting the u s atlantic coast abstract estimating the likelihood of tsunamis occurring along the u s atlantic coast critically depends on knowledge of tsunami source probability we review available information on both earthquake and landslide probabilities from potential sources that could generate local and transoceanic tsunamis estimating source probability includes defining both size and recurrence distributions for earthquakes and landslides for the former distribution source sizes are often distributed according to a truncated or tapered power law relationship for the latter distribution sources are often assumed to occur in time according to a poisson process simplifying the way tsunami probabilities from individual sources can be aggregated for the u s atlantic coast earthquake tsunami sources primarily occur at transoceanic distances along plate boundary faults probabilities for these sources are constrained from previous statistical studies of global seismicity for similar plate boundary types in contrast there is presently little information constraining landslide probabilities that may generate local tsunamis though there is significant uncertainty in tsunami source probabilities for the atlantic results from this study yield a comparative analysis of tsunami source recurrence rates that can form the basis for future probabilistic analyses

el nino southern oscillation extrema in the holocene and last glacial maximum 1 the el nino southern oscillation enso is the largest engine of interannual climate variability on the planet yet its past behavior and potential for future change are poorly understood and vigorously contested reconstructions of past enso are indispensable for testing climate models tasked with predicting future enso activity in a warming world but suitable geologic archives are scarce especially for the last glacial period here we reconstruct mean climate and enso variability in the holocene and last glacial maximum lgm from oxygen isotopic ratios 18o of individual foraminifera retrieved from deep sea sediments our results document coordinated adjustments of the tropical pacific enso system between two diametrically opposite states an amplified enso state in the lgm associated with a reduced zonal temperature gradient and a damped enso state in the mid holocene with enhanced gradient orbital precession provided the switch between these states and acted as the dominant external driver of the tropical pacific enso system in the past 25 000 years the linked response of the mean state and variability to orbital forcing provides an integrated framework for testing enso theory and models

holocene east asian summer monsoon records in northern china and their inconsistency with chinese stalagmite δ18o records abstract monsoon precipitation over china exhibits large spatial differences it has been found that a significantly enhanced east asian summer monsoon easm is characterized by increased rainfall in northern china and by reduced rainfall in southern china and this relationship occurs on different time scales during the holocene this study presents results from a diverse range of proxy paleoclimatic records from northern china where precipitation variability is traditionally considered as an easm proxy our aim is to evaluate the evolution of the easm during the holocene and to compare it with all of the published stalagmite 18 o records from the asian monsoon region in order to explore the potential mechanism s controlling the chinese stalagmite 18 o we found that the intensity of the easm during the holocene recorded by the traditional easm proxy of moisture or precipitation records from northern china is significantly different from the chinese stalagmite 18 o records the easm maximum occurred during the mid holocene challenging the prevailing view of an early holocene easm maximum mainly inferred from stalagmite 18 o records in eastern china in addition all of the well dated holocene stalagmite 18 o records covering a broad geographical region exhibit a remarkably similar trend of variation and are statistically well correlated on different time scales thus indicating a common signal however in contrast with the clear consistency in the 18 o values in all of the cave records both instrumental and paleoclimatic records exhibit significant spatial variations in rainfall on decadal to centennial time scales over eastern china in addition both paleoclimatic records and modeling results suggest that holocene east asian summer monsoon precipitation reached a maximum at different periods in different regions of china thus the stalagmite 18 o records from the easm region should not be regarded as a reliable indicator of the strength of the east asian summer monsoon furthermore modern observations indicate that the moisture for precipitation in the east asian monsoon region is mainly derived from the indian ocean the moisture transport route from the indian ocean to the east asian monsoon region during the holocene is almost identical to that of modern precipitation therefore the strong correlation of 18 o records in the easm and indian summer monsoon ism regions and the similarity of the pattern of latitudinal changes in 18 o values in stalagmites and in modern meteoric precipitation along the water vapor transport route further suggests that the stalagmite 18 o records from the easm region are essentially a signal of the isotopic composition of precipitation which is determined mainly by changes in the 18 o of atmospheric vapor in the upstream source region over the indian ocean and indian monsoon region via the upstream depletion mechanism finally the main trends of the stalagmite 18 o records are strongly correlated with the known evolution of the ism and therefore these records reflect the history of the ism rather than that of the easm our findings support the conclusion that easm variability is mainly controlled by northern hemisphere summer insolation and was strongly modulated by ice volume during the last deglaciation and early holocene which delayed the response of the easm maximum to peak insolation forcing

does the spatial distribution of smaller earthquakes delineate areas where larger earthquakes are likely to occur in the development of the latest generation of national seismic hazard maps one of the component models used the spatial distribution of smaller earthquakes in the eastern united states to forecast the locations of larger earthquakes frankel 1995 variations of this hypothesis that smaller earthquakes indicate where larger earthquakes are likely to occur are found throughout earthquake studies in a previous study kafka and walcott 1998 we tested this hypothesis for earthquakes in the northeastern united states neus to see how well the spatial distribution of smaller earthquakes recorded by seismic networks in the neus forecasts the locations of larger earthquakes that have already occurred the essence of our procedure is to systematically analyze how often previously occurring smaller earthquakes occurred in the vicinity of larger earthquakes the purpose of this study is to extend that investigation to other areas of the world to obtain a more global perspective on this issue here we report on an extension of that investigation to the southeastern united states the new madrid seismic zone southern california northern california israel turkey and the entire eastern united states our results to date do in fact suggest that in a variety of tectonic environments the spatial distribution of smaller earthquakes delineates areas in which larger earthquakes are likely to occur in a number of cases where locations of larger earthquakes were not forecast based on this approach we suspect that the misses are at least in part due to incompleteness and quirks in the earthquake catalogs

reconstruction of holocene monsoon history from the pearl river estuary southern china using diatoms and carbon isotope ratios this study employs a multiproxy approach in the reconstruction of holocene monsoon history from sedimentary sequences obtained from the pearl river estuary southern china a set of modern surface sediment samples were collected within and outside the estuary and a sediment core was obtained from the mouth of the estuary a range of modern environmental variables were recorded including water salinity summer winter and annual average and water depth the diatom results show a good relationship with water salinity with marine diatoms dominating the more distal samples from outside the main estuary and freshwater diatoms dominating the proximal samples influenced by higher freshwater flux this pattern is matched by the bulk organic carbon isotopes the isotope values vary between 21 1 0 3 0 for samples from the fully marine environment between 23 2 0 8 and 23 7 0 8 for samples from the mid to outer estuary brackish water environment and less than 24 7 1 3 for samples from the inner estuary close to the freshwater sources similarly the c n ratios vary from below 7 0 6 in the marine end members to over 14 8 3 0 in the freshwater end members both the diatom and carbon data from the sediment core reveal a significant increase in freshwater flux from 8500 cal yr bp resulting from the enhanced summer monsoon regime in early holocene the strength of freshwater flux reached its highest between 7500 and 6000 cal yr bp in the last 6000 years freshwater flux decreased towards present reflecting a gradual weakening of the summer monsoon

holocene vegetation history precipitation changes and indian summer monsoon evolution documented from sediments of xingyun lake south west china we present a pollen based precipitation reconstruction and multi proxy records from a 485 cm long sequence from a sediment core from xingyun lake yunnan plateau south west china which depicts the evolution of the indian summer monsoon ism during the last 8500 years pollen and other palaeoenvironmental records document several stages of vegetation history and climate change the warmest and wettest climate in the xingyun lake catchment occurred before 5500 cal a bp and subsequently the climate became gradually drier after 2000 cal a bp the regional environmental conditions became unstable and a wet medieval warm period is probably recorded our reconstruction of the ism is similar to that portrayed by holocene speleothem o 18 records from southern china but is distinctly different from the east asian summer monsoon easm evolution which features a mid holocene maximum our results support the hypothesis that the ism and easm evolved asynchronously during the holocene and imply that the chinese speleothem o 18 records from southern china may principally reflect changes in moisture source from the indian monsoon domain and thus record the history of the ism rather than the easm

detection of microearthquakes and identification of their causative structures in the eastern offshore region of south korea abstract a matched filter has been applied to continuous seismic records from the eastern offshore region of south korea to identify small earthquakes undetected by routine processing the resulting density of the regional earthquake catalog has increased by a factor of five relative to the detections reported by the korea meteorological administration high precision locations of newly identified microearthquakes and previously located earthquakes cluster into streaks that delineate structures responsible for the seismicity associated with the hupo fault offshore of the southern korean peninsula microearthquakes in the northern and southern segments of the fault zone exhibit different behaviors earthquakes in the northern segment occur at a regular temporal interval while those in the southern segment occur in bursts the identified fault system dips steeply to the west at shallow

holocene multidecadal to millennial scale variations in iceland scotland overflow and their relationship to climate the nordic seas overflows are an important part of the atlantic thermohaline circulation while there is growing evidence that the overflow of dense water changed on orbital time scales during the holocene less is known about the variability on shorter time scales beyond the instrumental record here we reconstruct the relative changes in flow strength of iceland scotland overflow water isow the eastern branch of the overflows on multidecadal millennial time scales the reconstruction is based on mean sortable silt ss from a sediment core on the gardar drift 60 19 n 23 58 w 2081 m our ss record reveals that the main variance in isow vigor occurred on millennial time scales 1 2 kyr with particularly prominent fluctuations after 8 kyr superimposed on the millennial variability there were multidecadal centennial flow speed fluctuations during the early holocene 10 9 kyr and one prominent minimum at 0 9 kyr we find a broad agreement between reconstructed isow and regional north atlantic climate where a strong weak isow is generally associated with warm cold climate we further identify the possible contribution of anomalous heat and freshwater forcing respectively related to reconstructed overflow variability we infer that ocean poleward heat transport can explain the relationship between regional climate and isow during the middle to late holocene whereas freshwater input provides a possible explanation for the reduced overflow during early holocene 8 10 kyr

concordant monsoon driven postglacial hydrological changes in peat and stalagmite records and their impacts on prehistoric cultures in central china asian monsoon records are widely documented but specific proxies of monsoonal rainfall are limited we present here two new independent proxy records from peatland and stalagmite archives that indicate a high degree of concordance between monsoon driven hydrological changes occurring since the last deglaciation in a broad region of central china the wet periods elevated the water table in the dajiuhu peatland as recorded by reduced mass accumulation rates of hopanoids biomarkers for aerobic microbes confirmed by molecular phylogenic analyses the hopanoid based reconstruction is supported by the first report of the environmental magnetism parameter arm sirm anhysteretic remanent magnetization saturation isothermal remanent magnetization ratio of fine magnetic particles to total ferrimagnetic particles in a stalagmite from heshang cave in central china heavy rainfall resulted in the enhanced transport of coarse particles to the cave and thus low arm sirm values in the stalagmite the hydrological conditions inferred from the two records reveal three relatively long wet periods in central china 13 11 5 k y ago 9 5 7 0 k y ago and 3 0 1 5 k y ago archaeological evidence for the hydrological impacts on regional populations comes from the observation that temporal shifts among six distinctive cultures of the neolithic period to the iron age in central china occurred during wet periods or flood episodes spatiotemporal distributions of 1600 prehistoric settlement sites correlate with the proxy inferred fluctuating hydrological conditions with enhanced flooding risk forcing major relocations of human settlements away from riparian zones

comparison of short term and time independent earthquake forecast models for southern california we have initially developed a time independent forecast for southern california by smoothing the locations of magnitude 2 and larger earthquakes we show that using small m 2 earthquakes gives a reasonably good prediction of m 5 earthquakes our forecast outperforms other time independent models kagan and jackson 1994 frankel et al 1997 mostly because it has higher spatial resolution we have then developed a method to estimate daily earthquake probabilities in south ern california by using the epidemic type earthquake sequence model kagan and knopoff 1987 ogata 1988 kagan and jackson 2000 the forecasted seismicity rate is the sum of a constant background seismicity proportional to our time independent model and of the aftershocks of all past earthquakes each earthquake triggers aftershocks with a rate that increases exponentially with its magnitude and decreases with time following omori s law we use an isotropic kernel to model the spatial distribution of aftershocks for small m 5 5 mainshocks for larger events we smooth the density of early aftershocks to model the density of future aftershocks the model also assumes that all earthquake magnitudes follow the gutenberg richter law with a uniform b value we use a maximum likelihood method to estimate the model parameters and test the short term and time independent forecasts a retro spective test using a daily update of the forecasts between 1 january 1985 and 10 march 2004 shows that the short term model increases the average probability of an earthquake occurrence by a factor 11 5 compared with the time independent forecast

subsurface structure and kinematics of the calaveras hayward fault stepover from three dimensional vp and seismicity san francisco bay region california the calaveras and hayward faults are major components of the san andreas fault system in the san francisco bay region dextral slip is presumed to transfer from the calaveras fault to the hayward fault in the mission hills region an area of uplift in the contractional stepover between the two faults here the estimated deep slip rates drop from 15 to 6 mm yr on the calaveras fault and slip begins on the hayward fault at an estimated 9 mm yr a lineament of microseismicity near the mission fault links the seismicity on the calaveras and hayward faults and is presumed to be related directly to this slip transfer however geologic and seismologic evidence suggest that the mission fault may not be the source of the seismicity and that the mission fault is not playing a major role in the slip transfer we perform a joint inversion for hypocenters and the 3d p wave velocity structure of the stepover region using 477 earthquakes we find strong velocity contrasts across the calaveras and hayward faults corroborated by geologic gravity and aeromagnetic data detailed examination of two seismic lineaments in conjunction with the velocity model and independent geologic and geophysical evidence suggests that they represent the southern extension of a northeasterly dipping hayward fault that splays off the calaveras fault directly accounting for the deep slip transfer the mission fault appears to be accommodating deformation within the block between the hayward and calaveras faults thus the calaveras and hayward faults need to be considered as a single system for developing rupture scenarios for seismic hazard assessments online material 3d interactive visualizations of the mission and alum rock hypocenters