evidence for the delayed oscillator mechanism for enso the observed oceanic kelvin mode in the far western pacific abstract observed surface winds from 1961 through september 1992 are used to force a reduced gravity shallow water ocean model results from the hindcast of ocean variability are found to be consistent with the results li and clarke presented in a previous study of sea level and zonal wind variability in the tropical pacific in this note the apparent discrepancies are reconciled between delayed oscillator theory and calculated lag correlations between the observationally based records of western boundary kelvin mode amplitude w and zonal wind forcing evidence for sensitivity in these delayed oscillator lag correlations is presented from a variety of sources including the hindcast data output from the standard version of the zebiak and cane coupled ocean atmosphere model and through three cases with idealized time series of enso variability the authors demonstrate that the low lag correlations for w leading the zonal wind forcing by 1 to 1 years is not inconsistent with the hypothesized rol

late quaternary earthquake related soft sediment deformation along the belgian portion of the feldbiss fault lower rhine graben system abstract trench investigations along the bree fault scarp in belgium in the framework of a first paleoseismological experience in the area of the lower rhine graben system have not only demonstrated the existence of seismogenic faults almost extending to the present ground surface but also exposed several types of soft sediment deformation affecting sandy sediments and soils of inferred late weichselian to holocene age the observed features include asymmetric folding small scale normal faulting possible sand intrusions and small water escape or load structures establishing a seismic origin for the individual features is not always possible based on their sedimentary characteristics only particularly due to the potential confusion with periglacial phenomena but their abundance the close association of different deformational styles and their vicinity to a known active fault all seem to be compatible with an earthquake induced scenario the features are to some extent comparable to those generated during the recent ms 5 3 roermond earthquake at the opposite side of the roer valley graben stratigraphical and mutual geometrical relationships suggest the occurrence of at least three distinct deformational events since probably 30 000 years and one event before that time since nothing is yet known about their regional distribution however estimating the associated paleomagnitudes from these soft sediment deformations is premature

a seismic hazard uncertainty analysis for the new madrid seismic zone abstract a review of the scientific issues relevant to characterizing earthquake sources in the new madrid seismic zone has led to the development of a logic tree of possible alternative parameters a variability analysis using monte carlo sampling of this consensus logic tree is presented and discussed the analysis shows that for 2 exceedence in 50 year hazard the best estimate seismic hazard map is similar to previously published seismic hazard maps for the area for peak ground acceleration pga and spectral acceleration at 0 2 and 1 0 s 0 2 and 1 0 s sa the coefficient of variation cov representing the knowledge based uncertainty in seismic hazard can exceed 0 6 over the new madrid seismic zone and diminishes to about 0 1 away from areas of seismic activity sensitivity analyses show that the largest contributor to pga 0 2 and 1 0 s sa seismic hazard variability is the uncertainty in the location of future 1811 1812 new madrid sized earthquakes this is followed by the variability due to the choice of ground motion attenuation relation the magnitude for the 1811 1812 new madrid earthquakes and the recurrence interval for m 6 5 events seismic hazard is not very sensitive to the variability in seismogenic width and length

rare earth element geochemistry of colour lake an acidic freshwater lake on axel heiberg island northwest territories canada a lake column profile was collected in 24 m of water from colour lake axel heiberg island northwest territories canada in early june of 1991 beneath 1 8 m of lake ice the rare earth element ree concentrations of the acidic fresh waters of colour lake were analyzed along with the major solute chemistry in order to investigate ree distribution and speciation in the low ph waters previous studies indicate the lake is dominated by ca2 mg2 and so42 and has no measurable carbonate alkalinity shale normalized ree patterns for the lake waters are all enriched in the middle ree s mree s as compared to the light ree s lree s and heavy ree s hree s dissolved ree concentrations in colour lake e g 2 3 22 nmol kg 1 for nd mean value of 20 nmol kg 1 are typically less than values obtained for the acid saline waters of the lake tyrrell playa system in australia as well as the slightly acidic groundwaters of the carnmenellis region of england but greater than ree concentrations measured in the alkaline saline waters of mono lake california u s a the speciation of the ree s in colour lake was modelled based on the major solute chemistry using a combined specific ion interaction and ion pairing model these calculations suggest that in the relatively high sulfate low ph waters of colour lake the ree s exist as either free metal so42 or f complexes our calculations indicate that so42 complexes dominate over the free metal and fluoride species for the majority of the ree s in the lake water and that in general for acidic high sulfate waters sulfate complexes with the ree s may increase the dissolved concentrations of the ree s over natural waters where relatively low sulfate concentrations prevail

high resolution seismic reflection imaging of shallow deformation beneath the northeast margin of the manila high at big lake arkansas abstract the manila high an elliptical area 19 km long n s by 6 km wide e w located west southwest of big lake arkansas has less than 3 m of topographic relief geomorphic stratigraphic and chronology data indicate that big lake formed during at least two periods of holocene uplift and subsequent damming of the south flowing little river age data of an organic mat located at the base of an upper lacustrine deposit indicates an abrupt possibly tectonic formation of the present big lake between ad 1640 and 1950 we acquired 7 km of high resolution seismic reflection data across the northeastern margin of the manila high to examine its near surface bedrock structure and possible association with underlying structures such as the blytheville arch sense of displacement and character of imaged faults support interpretations for either a northwest trending 1 5 km wide block of uplifted strata or a series of parallel northeast trending faults that bound horst and graben structures we interpret deformation of the manila high to result from faulting generated by the reactivation of right lateral strike slip fault motion along this portion of the blytheville arch the most recent uplift of the manila high may have occurred during the december 16 1811 new madrid earthquake

plate boundary earthquakes and tsunamis of the past 5500 yr sixes river estuary southern oregon eleven plate boundary earthquakes over the past 5500 yr have left a stratigraphic signature in coastal wetland sediments at the lower sixes river valley in south coastal oregon within a 1 8 km2 abandoned meander valley 10 buried wetland soils record gradual and abrupt relative sea level changes back in time to 6000 yr ago an additional youngest buried soil at the mouth of the sixes river subsided during the a d 1700 cascadia earthquake multiple lines of evidence indicate that tectonic subsidence caused soil burial including permanent relative sea level rise following burial lateral continuity of buried soil horizons over hundreds of meters diatom assemblages showing that sea level rose abruptly at least 0 5 m and sand deposits on top of buried soils demonstrating coincidence of coseismic subsidence and tsunami inundation for at least two of the buried soils liquefaction of sediment accompanied subsidence the 11 soil burial events took place between 300 and 5400 yr ago yielding an average recurrence interval of plateboundary earthquakes of 510 yr comparing paleoseismic sites in southern washington and south coastal oregon with the sixes river site for the past 3500 yr indicates that the number and timing of recorded plate boundary earthquakes are not the same at all sites in particular a sixes earthquake at 2000 yr ago lacks a likely correlative in southern washington therefore unlike the a d 1700 cascadia earthquake some cascadia plate boundary earthquakes do not rupture the entire subduction zone from southern oregon to southern washington in the lower sixes river valley the upperplate cape blanco anticline deforms sediment of late pleistocene and holocene age directly above the subduction zone differential tectonic subsidence occurred during two of the plate boundary earthquakes when a blind upper plate reverse fault for which the cape blanco anticline is the surface fold slipped coseismically with rupture of the plate boundary during these two earthquakes sites 2 km from the anticline axis subsided 0 5 m more than sites 1 km from the axis

new evidence for a large earthquake in the new madrid seismic zone between a d 1400 and 1670 in an integrated geological archaeological and geophysical study in the new madrid seismic zone of the southeastern united states we documented a prehistoric sand blow and related feeder dikes at an archaeological site near steele missouri archaeological analysis combined with radiocarbon dating suggest that the earthquake induced features formed between a d 1400 and 1670 this paleoseismic study provides the best evidence to date for a large earthquake occurring in the zone within 400 yr prior to the 1811 1812 new madrid earthquake sequence to determine an optimal location for excavating at the study site we mapped surficial artifact density and conducted geophysical surveys in doing so we were able to reveal critical relationships for constraining the age of the prehistoric earthquake with minimal impact to the archaeological site

is enso a cycle or a series of events 1 after early ideas that saw el ninos as isolated events the advent of coupled models brought the conception of enso as a cycle in which each phase led to the next in a self sustained oscillation twenty two years of observations that represent the el nino and la nina peaks east pacific sst and the memory of the system zonal mean warm water volume suggest a distinct break in the cycle in which the coupled system is able to remain in a weak la nina state for up to two years so that memory of previous influences would be lost similarly while the amplitude of anomalies persists from the onset of a warm event through its termination there is no such persistence across the la nina break these observations suggest that el ninos are in fact event like disturbances to a stable basic state requiring an initiating impulse not contained in the dynamics of the cycle itself

whangaehu river new zealand geochemistry of a river discharging from an active crater lake abstract during 3 surveys in 1992 water and sediment samples were collected from the length of the whangaehu river and above the confluence points of major tributaries the waters were analysed for major cations ca li mg na anions cl so4 metals al as cd cr cu fe hg mn ni pb and zn sio2 ph conductivity and temperature the sediments were analysed for some metals during 1992 the volcanic crater lake of mt ruapehu intermittently discharged very acid waters into the whangaehu river for example in february during an intense period of snow melt and crater lake overflow the ph of the river water was 2001 sec metal concentrations were similar in the total recoverable and dissolved metal fractions of the water at times of lower overflow

stream networks and long term surface uplift in the new madrid seismic zone stream networks are sensitive to low rates of surface uplift and can be used to decipher the history of large earthquakes even where faults do not rupture the surface as in intraplate seismic zones statistical analysis of alluvial network data from topographic maps in the new madrid seismic zone in the central united states shows that stream segment gradients deviate the most from an estimated natural stream profile where surface uplift is greatest evidence of cumulative deformation distilled from stream network patterns represents at least several meters of differential surface uplift during holocene time which suggests that more than one cycle of surface deformation occurred

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

tectonic setting of the 1971 sylmar and 1994 northridge earthquakes in the san fernando valley california the san fernando valley lies above the north dipping 1971 sylmar and south dipping 1994 northridge earthquake faults to understand the tectonic setting of these two earthquakes we mapped subsurface geology of the san fernando valley down to a depth of 3 km using industry oil well and seismic data the 1994 northridge earthquake did not rupture the surface and the south dipping aftershock zone terminated against the north dipping 1971 aftershock zone at a depth of 5 8 km however the blind northridge fault has a near surface geologic expression fault propagation folding related to the northridge fault has preserved a thick forelimb sequence of plio pleistocene saugus formation in the sylmar basin and merrick syncline which are located on the hanging wall side of north dipping reverse faults the north dipping mission hills verdugo and northridge hills reverse faults are interpreted to be potential seismic sources because fault propagation folds above these faults have tectonic geomorphic expression these north dipping reverse faults were initiated during the deposition of the saugus formation between 2 3 and 0 5 ma and have minimum dip slip rates of 0 35 to 1 1 mm yr based on the oldest possible age of the initiation of faulting the northridge hills and mission hills faults are interpreted to merge at depth and are located at the updip extension of the 1971 aftershock zone even though these faults did not rupture during the 1971 earthquake surface breaks appeared north of these faults mostly along north dipping bedding planes and are interpreted as secondary features related to flexural slip folding rather than a direct extension of the 1971 seismogenic fault surface and subsurface geology together with seismological data of the 1971 and 1994 earthquakes suggests that the north and south dipping deformation zones in the san fernando valley are divided into multiple segments separated by northeast trending structural discontinuities

late pleistocene evolution of the lower mississippi river valley southern missouri to arkansas the mississippi river served as the principal conduit for meltwaters discharging from the southern margins of north american ice sheets the northern half of the mississippi river alluvial valley in missouri and arkansas can be subdivided into two distinct channel courses the western and eastern lowlands which are separated by crowleys ridge the eastern lowlands contain two entry points the bell city oran and thebes gaps the latter is a narrow bedrock gorge that contains the modern river this paper summarizes a model for evolution of channel courses in the western and eastern lowlands during the illinoian and wisconsin glacial stages for the western lowlands stratigraphic relations between loess units and subjacent fluvial deposits show that major continuous terrace surfaces or valley trains are illinoian or late wisconsin in age investigations of tributary valley fills further show the western lowlands were deeply incised during the early to middle wisconsin stage then aggraded during the late wisconsin stage to such an extent that tributary valleys were backfilled with slackwater deposits moreover analysis of loess thinning and fining trends shows that early to middle wisconsin roxana silt and the late wisconsin peoria loess covers on western lowlands valley trains were derived from deflation of valley trains in the eastern lowlands we conclude that the western lowlands were the primary mississippi river course during illinoian deglaciation but were abandoned shortly thereafter then episodically reoccupied during the late wisconsin stage for the eastern lowlands course valley trains of early to middle wisconsin age are not preserved with the exception of a small remnant where the mississippi river broke through a gap in the southern margins of crowleys ridge and reentered the western lowlands all valley trains in the eastern lowlands are late wisconsin age a series of discontinuous terrace surfaces in the bell city oran gap represent dissected remnants of the primary late wisconsin full glacial and early late glacial course of the mississippi river or combined mississippi and ohio rivers whereas younger continuous braided stream surfaces in the bell city oran and thebes gap courses represent valley trains of latest wisconsin and earliest holocene age hence the bell city oran gap was the primary course during the entire wisconsin stage and the thebes gap was permanently occupied in earliest holocene time as much as 5 m difference in elevation between successive late wisconsin terrace surfaces of the eastern lowlands indicates that valley trains were rapidly constructed incised and abandoned in response to fluctuations in the delivery of meltwater and outwash from the former ice margin moreover a variety of data indicates that deglacial meltwater floods were commonly of sufficient magnitude to overflow from the primary course in the bell city oran gap throughout the late wisconsin substage floodwaters overflowed into the western lowlands constructed a series of secondary valley trains and filled tributary valleys with slackwater deposits during the latest wisconsin stage perhaps in association with the drainage of glacial lake agassiz floodwaters overflowed into the western lowlands and broke through the thebes gap the charleston fan represents the initial deposits of the thebes gap course following deposition of a large crevasse splay at the western lowlands entrance that course was no longer active but flow was routed through the thebes gap during periods of high magnitude flooding until the bell city oran gap was abandoned and the thebes gap course was permanently occupied during earliest holocene time

the chemical and hydrologic structure of poa s volcano costa rica comparison of the chemical characteristics of spring and river water draining the flanks of poa s volcano costa rica indicates that acid chloride sulfate springs of the northwestern flank of the volcano are derived by leakage and mixing of acid brines formed in the summit hydrothermal system with dilute flank groundwater acid chloride sulfate waters of the rio agrio drainage basin on the northwestern flank are the only waters on poa s that are affected by leakage of acid brines from the summit hydrothermal system acid sulfate waters found on the northwestern flank are produced by the interaction of surface and shallow groundwater with dry and wet acid deposition of so2 and h2so4 aerosols respectively the acid deposition is caused by a plume of acid gases that is released by a shallow magma body located beneath the active crater of poa s no evidence for a deep reservoir of neutral ph sodium chloride brine is found at poa s the lack of discharge of sodium chloride waters at poa s is attributed to two factors 1 the presence of a relatively volatile rich magma body degassing at shallow depths 1 km into a high level summit groundwater system and 2 the hydrologic structure of the volcano in which high rates of recharge combine with rapid lateral flow of shallow groundwater to prevent deep seated sodium chloride fluids from ascending to the surface the shallow depth of the volatile rich magma results in the degassing of large quantities of so2 and hcl these gases are readily hydrolyzed and quickly mix with meteoric water to form a reservoir of acid chloride sulfate brine in the summit hydrothermal system high recharge rates and steep hydraulic gradients associated with elevated topographic features of the summit region promote lateral flow of acid brines generated in the summit hydrothermal system however the same high recharge rates and steep hydraulic gradients prevent lateral flow of deep seated fluids thereby masking the presence of any sodium chloride brines that may exist in deeper parts of the volcanic edifice structural stratigraphic and topographic features of poa s volcano are critical in restricting flow of acid brines to the northwestern flank of the volcano a permeable lava lahar sequence that outcrops in the rio agrio drainage basin forms a hydraulic conduit between the crater lake and acid chloride sulfate springs spring water residence times are estimated from tritium data and indicate that flow of acid brines from the active crater to the rio agrio source springs is relatively rapid 3 to 17 years hydraulic conductivity values of the lava lahar sequence calculated from residence time estimates range from 10 5 to 10 7 m s these values are consistent with hydraulic conductivity values determined by aquifer tests of fractured and porous lava pyroclastic sequences at the base of the northwestern flank of the volcano fluxes of dissolved rock forming elements in rio agrio indicate that approximately 4300 and 1650 m3 of rock are removed annually from the northwest flank aquifer and the active crater hydrothermal system respectively over the lifetime of the hydrothermal system 100 s to 1000 s of years significant increases in aquifer porosity and permeability should occur in marked contrast to the reduction in permeability that often accompanies hydrothermal alteration in less acidic systems average fluxes of fluoride chloride and sulfur calculated from discharge and compositional data collected in the rio agrio drainage basin over the period 1988 1990 are approximately 2 38 and 30 metric tons day these fluxes should be representative of minimum volatile release rates at poa s in the last 10 to 20 years

fault slip rates in the modern new madrid seismic zone structural and geomorphic analysis of late holocene sediments in the lake county region of the new madrid seismic zone indicates that they are deformed by fault related folding above the blind reelfoot thrust fault the widths of narrow kink bands exposed in trenches were used to model the reelfoot scarp as a forelimb on a fault bend fold this coupled with the age of folded sediment yields a slip rate on the blind thrust of 6 1 0 7 mm year for the past 2300 100 years an alternative method used structural relief across the scarp and the estimated dip of the underlying blind thrust to calculate a slip rate of 4 8 0 2 mm year geometric relations suggest that the right lateral slip rate on the new madrid seismic zone is 1 8 to 2 0 mm year

earthquake signals in tree ring data from the new madrid seismic zone and implications for paleoseismicity severe ground shaking and the formation of reelfoot lake during the great new madrid earthquakes of a d 1811 1812 had a profound effect on baldcypress trees that still survive in reelfoot lake of northwestern tennessee inundation greatly increased baldcypress radial growth from 1812 to 1819 and permanently decreased wood density after 1811 ground shaking fractured the baldcypress stems that were present during the 1811 1812 event but fractures are absent in the post 1811 growth in contrast the growth of old baldcypress trees in the st francis sunkland of northeastern arkansas was severely suppressed for almost 50 yr following the 1811 1812 new madrid earthquakes thus there are two opposite but profound growth responses to the same earthquake events preserved in baldcypress trees of the new madrid seismic zone the tree ring chronology at reelfoot lake extends from a d 1682 to 1990 but the 1812 1819 growth surge was the only extreme growth anomaly in this 309 yr period the st francis sunkland chronology extends from a d 1321 to 1990 and the 1812 1857 growth suppression is the most severe and prolonged growth anomaly of this entire 670 year period thus the tree ring record indicates that there was not a great earthquake during the 129 yr prior to 1811 in the reelfoot lake basin nor during the 490 yr prior to 1811 in the st francis sunkland

liquefaction susceptibility mapping in the city of memphis and shelby county tennessee abstract earthquake induced sand dikes have been identified in cut banks of the wolf and loosahatchie rivers in the city of memphis and shelby county tennessee most of the dikes are near the mouths of these rivers within the city limits of memphis but one dike occurs 36 km upstream in the bank of the wolf river in collierville the dikes range in width from 1 to 50 cm and at some localities can be traced vertically as much as 4 m from their source bed to within 50 cm of the flood plain surface the age of the dikes is unknown but they are interpreted to be from the great 1811 1812 new madrid earthquakes because they are locally buried by historical sediments containing bricks the larger number of dikes and upstream extent of liquefaction along the wolf river suggests that liquefaction susceptibility is greater in the wolf river flood plain than in other flood plains in shelby county this greater liquefaction susceptibility of the wolf river flood plain appears to be due to the sand in its basal point bar sequence and a relatively thin overbank silt clay cap geologic and geologically based liquefaction susceptibility maps 1 24 000 were made of the memphis northwest and collierville 7 5 quadrangles of shelby county the liquefaction susceptibility maps show very high susceptibility for mississippi wolf and loosahatchie river flood plains high susceptibility in areas of artificial fill on these three flood plains moderate susceptibility along other flood plains and terraces in these quadrangles and low susceptibilities in the interfluve areas

rapid intraplate strain accumulation in the new madrid seismic zone remeasurement of a triangulation network in the southern part of the new madrid seismic zone with the global positioning system has revealed rapid crustal strain accumulation since the 1950s this area experienced three large moment magnitudes 8 earthquakes in 1811 to 1812 the orientation and sense of shear is consistent with right lateral strike slip motion along a northeast trending fault zone as indicated by current seismicity detection of crustal strain accumulation may be a useful discriminant for identifying areas where potentially damaging intraplate earthquakes may occur despite the absence of large earthquakes during historic time

impact of the alluvial style on the geoarcheology of stream valleys abstract the extensive archeological record within river valleys provides an environment long favored for study by the archeologic community this record of human occupation varies with the alluvial style of the river resulting in each river valley having a unique archeological record controlled by three factors location of occupation sites preservation of those sites and recognition of the sites if problems of site preservation and recognition in a river valley can be recognized and addressed a better insight into settlement patterns and complex human environment interactions can result this study represents a synthesis of extensive published and secondary data sets pertaining to archaeology and alluvial geomorphology of the lower missouri red and mississippi rivers to examine the relationship of prehistoric site distribution with fluvial geomorphology the archeologic data are from published literature and government agencies the geomorphic data are from a variety of published and unpublished investigations including maps of alluvial geomorphology digital elevation models aerial photographs and topographic maps the data were input into spreadsheets and a gis for qualitative and quantitative analysis prehistoric human occupation of the narrow missouri valley floor is limited with only 0 061 recorded sites km2 additional sites are likely buried by thick vertical accretion sediment on the limited prehistoric portions of the floodplain and within alluvial colluvial fans along the valley margin non random preservation patterns such as the absence of sites from the youngest cultural period are attributed to shifts in settlement patterns in comparison to the lower missouri river valley prehistoric occupation of the lower red and mississippi rivers was much more extensive and the density of occupation was 0 274 sites km2 and 0 277 sites km2 respectively significant differences do exist in the age of sites and their relationship to different floodplain depositional environments many sites along the active meander belt of the red river were likely lost due to high rates of channel migration nevertheless intense occupation of paleo indian through caddoan groups assures that many significant sites have been preserved the wide valley and high rates of sedimentation suggest that many sites are likely buried particularly along natural levees flanking an older meander belt recorded sites are also present along streams that incise the terrace along the terrace margin and along small channels that cross the backswamp the spatial and temporal site distribution along the lower mississippi valley is distinct in comparison with the red river because the mississippi valley is wider the terraces are younger and less dissected and the floodplain has more relief and is not broadly inundated by floodwater with relatively low sediment concentrations most of the significant archaic through mississippian period floodplain sites are located along the surfaces of abandoned mississippi and distributary meander belts which aggraded above the adjacent backswamp and have rarely been influenced by flood sedimentation since abandonment abundant paleo indian through mississippian period sites are also widely distributed across undissected terraces only a few significant mississippian sites are present along the active meander belt and in the backswamp where flooding was common in comparison with the red river the archaeological record of the floodplain is less likely to be influenced by burial or erosion due to the mississippi river having lower rates of overbank sedimentation and channel migration respectively the variable alluvial styles of the lower missouri river lower red river and the lower mississippi river valleys presented varying opportunities and constraints to occupation and sustained settlement and resulted in widely varying archaeological patterns that are partly dependent upon the alluvial geomorphology

a palaeoseismological and geoarchaeological investigation of the eliki fault gulf of corinth greece abstract palaeoseismological and morphotectonic analyses enable us to define a 400 m wide actively deformed zone associated with the active eliki normal fault central greece bounded on the south by a second order fault and on the north by a composite and prominent fault scarp this scarp is further analysed by trenching based on colluvium stratigraphy displacement of distinct horizons and deposition of sedimentary layers three faulting events have been identified along four fault strands affecting unconsolidated sediments in the trench the two younger events with throws of 0 93 and 1 37 m respectively the third event with a throw of 0 44 m and the penultimate 373 bc event suggest a variable seismic history the entire alluvial plain of the kerynitis and vouraikos rivers which cross the eliki fault has subsided at a rate of 1 4 mm year resulting in the burial of the late hellenistic roman occupation horizons under 3 m of fluvial and colluvial sediments in places extension in the broader area is accommodated by the seismically active eliki and egion faults structural and palaeoseismological analysis of those two faults indicates that they accommodate 1 5 mm year or about 10 of the geodetically estimated extension of up to 13 mm year

hydrogeochemistry and rare earth element behavior in a volcanically acidified watershed in patagonia argentina abstract the rio agrio watershed in northern patagonia argentina is naturally acidic due to discharges of volcanic h 2 so 4 hcl and hf at its headwaters near the summit of copahue volcano a suite of water samples was collected from the summit of the volcano to a point roughly 40 km downstream where the ph of the rio agrio rose above 6 0 this suite included a sample of the hyperacidic ph the concentrations of ree in the rio agrio decreased by several orders of magnitude through the study area as a result of dilution and chemical attenuation a subtle shift in the slope of shale normalized profiles of dissolved ree concentration was observed from being weakly positive near the source of the rio agrio to showing a weak middle ree enrichment trend in lake caviahue to being weakly negative in the lower reaches of the river the trend to a negative slope across the lanthanide series in the lower river is explained by selective partitioning of the heavier ree to hydrous oxides of fe and al suspended in the water column and accumulating on the riverbed most of the decrease in ree load occurred immediately downstream of the confluence with a tributary that increased the ph of the rio agrio from 4 3 to 6 1 although the mixed water was supersaturated with ree phosphate compounds precipitation of lnpo 4 is not believed to have been a dominant process because the predicted pattern of inter element fractionation from phosphate deposition is inconsistent with the observed trends instead ree attenuation most likely occurred from adsorption onto freshly precipitated hydrous aluminum oxide the behavior of ree in the rio agrio watershed is broadly similar to what has been observed in watersheds that owe their acidity to oxidation of sulfide minerals

late cretaceous and cenozoic geology of the new madrid seismic zone structure contour maps constructed from well seismic reflection and outcrop data of the tops of the paleozoic section upper cretaceous section paleocene midway group and eocene section illustrate the post paleozoic structure of the new madrid seismic zone region isopach maps of the late cretaceous section midway group and eocene section help constrain the timing of the structural events these maps which encompass much of the northern mississippi embayment reveal reactivation of the underlying late precambrian cambrian reelfoot rift during midway group deposition but no reactivation during late cretaceous or eocene deposition the structure contour maps also indicate a subtle south plunging depression on the tops of the paleozoic upper cretaceous and midway group along the axis of the northern mississippi embayment that we have called a trench this trench is 50 km wide has a maximum depth of 100 m and appears to have formed during the eocene the trench s western boundary coincides with the blytheville arch lake county uplift and its southeastern margin underlies memphis tennessee the blytheville arch lake county uplift is the structure responsible for the new madrid seismic zone and thus it is possible that the southeastern margin of the trench is also a fault zone northern mississippi embayment post paleozoic stratigraphy consists of sands silts and clays that thicken from 477 m at new madrid missouri to 987 m near memphis tennessee the uniformity of these sediments indicates their elastic properties and therefore seismic velocities are very similar however variations in cementation and unconformities within the section may influence seismic wave propagation manuscript received 17 june 1999

short term uplift rates and surface deformation along the reelfoot fault new madrid seismic zone abstract this study of variability in the amount and rate of deformation along the intraplate reelfoot fault of the new madrid seismic zone nmsz utilizes diverse research methods including geophysics geomorphology and fluvial sedimentology the transpressional reelfoot fault deforms late holocene mississippi river sediment into the tiptonville dome and adjacent reelfoot basin because reelfoot lake submerges a portion of the basin subbottom acoustic profiling of the lake was used to quantify the relief on the uplift at the natural levee of the abandoned tiptonville meander the most appropriate landform along the scarp for measuring cumulative structural relief a maximum relative vertical uplift of approximately 11 3 m was measured to identify spatial and temporal variability in surface deformation using geologic methods we relate fluvial sedimentation to three documented earthquake events during the past 2300 yr tuttle et al 2002 2005 which is the approximate age of the oldest deformed floodplain sediment guccione et al 2002 radiocarbon dates from organic material in fluvial and lacustrine sediment indicate that most of the uplift occurred during the last two major seismic events a minimum of 1 6 3 9 m of uplift was associated with the seismic episode at a d 1450 150 and a maximum of 5 9 8 2 m of uplift was associated with the 1812 episode we estimate a mean short term uplift rate of 1 2 cm yr 0 4 2 1 cm yr with 80 probability or a mean short term slip rate of 1 3 cm yr 0 5 2 3 cm yr with 80 probability these values are approximately 2 5 times higher than the long term rates based on the total amount of uplift averaged over the past 2300 yr mueller et al 1999 van arsdale 2000 estimating deformation rates associated with individual earthquake recurrences provides information on fluctuating activity of the nmsz

bootheel lineament a possible coseismic fault of the great new madrid earthquakes a remote sensing examination of the new madrid seismic zone has revealed a feature the bootheel lineament that may be the surface expression of one of the coseismic faults of the great new madrid earthquakes of 1811 and 1812 the lineament extends about 135 km in a north northeast direction through northeastern arkansas and southeastern missouri the morphology and pattern of the lineament suggest that it reflects a fault with strike slip displacement field data indicate that liquefied sand was injected along the lineament probably in 1811 and 1812 the bootheel lineament does not coincide with any of the major arms of new madrid seismicity possibly indicating that the current seismicity does not precisely reflect the faults that ruptured in 1811 and 1812

archeological and pedological evidence for large prehistoric earthquakes in the new madrid seismic zone central united states prehistoric liquefaction features have been identified by careful observation of their structural and stratigraphic relations to native american occupation horizons and their subtle soil characteristics the ages of these liquefaction features have been estimated from radiocarbon dating of wood associated with the features and native american artifacts found within bounding occupation horizons at three sites near blytheville arkansas in the central part of the new madrid seismic zone one sand blow crater formed between a d 800 and 1400 two sand blow deposits formed between a d 800 and 1670 and three possibly four sand dikes formed since 4035 b c where not found in association with native american occupation horizons and artifacts prehistoric liquefaction features can be difficult to distinguish from features that formed during the great new madrid earthquakes of a d 1811 and 1812 this raises the possibility that prehistoric liquefaction features may have been misinterpreted during previous studies in the area nevertheless a paleoearthquake chronology is beginning to emerge for the new madrid seismic zone our findings are consistent with paleoseismological studies in the northern part of the seismic zone and suggest a recurrence interval of hundreds of years for earthquakes large enough to induce liquefaction in this region m 6 4 by mapping the age distribution of liquefaction features a more accurate assessment of the long term earthquake potential of the region will be possible

late wisconsin to holocene deformation in the new madrid seismic zone the new madrid earthquakes of 1811 1812 produced regional deformation in northwestern tennessee southeastern missouri and northeastern arkansas landforms such as the lake county uplift reelfoot lake and the sunklands of northeast arkansas either formed or were reactivated during these great earthquakes two hundred and fifty three cores were used to construct a structure contour map of the unconformity between the eocene strata and the overlying quaternary mississippi river alluvium in the new madrid seismic zone this map reveals relief that mirrors the surface deformation and provides additional data on the distribution of regional deformation we interpret the structure contour map as a representation of the late wisconsin to the present strain field of the new madrid seismic zone this map provides constraints for future kinematic analyses of late quaternary new madrid faulting and allows forecasting of future coseismic deformation

on the modified mercalli intensities and magnitudes of the 1811 1812 new madrid earthquakes we reexamine original felt reports from the 1811 1812 new madrid earthquakes and determine revised isoseismal maps for the three principal mainshocks in many cases we interpret lower values than those assigned by earlier studies in some cases the revisions result from an interpretation of original felt reports with an appreciation for site response issues additionally earlier studies had assigned modified mercalli intensity mmi values of v vii to a substantial number of reports that we conclude do not describe damage commensurate with intensities this high we investigate several approaches to contouring the mmi values using both analytical and subjective methods for the first mainshock on 02 15 lt december 16 1811 our preferred contouring yields m 7 2 7 3 using the area moment regressions of johnston 1996 for the 08 00 lt on january 23 1812 and 03 45 lt on february 7 1812 mainshocks we obtain m 7 0 and m 7 4 7 5 respectively our magnitude for the february mainshock is consistent with the established geometry of the reelfoot fault which all evidence suggests to have been the causative structure for this event we note that the inference of lower magnitudes for the new madrid events implies that site response plays a significant role in controlling seismic hazard at alluvial sites in the central and eastern united states we also note that our results suggest that thrusting may have been the dominant mechanism of faulting associated with the 1811 1812 sequence

surface faulting of the 1954 fairview peak ms 7 2 and dixie valley ms 6 8 earthquakes central nevada abstract the 1954 fairview peak earthquake was followed 4 min and 20 sec later by the dixie valley earthquake surface ruptures were distributed among six different faults that define a complex north trending zone 100 km long and over 15 km wide the rupture sequence progressed from south to north the initial event produced a 32 km rupture of right oblique slip along the east dipping fairview fault where the components of right lateral offset and vertical separation reached 2 9 and 3 8 m respectively the northernmost ruptures occurred during the subsequent event along a 46 km portion of the east dipping dixie valley fault where the sense of slip was normal and reached a maximum vertical separation of 2 8 m average surface offset for both events is about 1 2 m the west dipping west gate louderback mountains and gold king faults also ruptured during the earthquake sequence these faults form a complex structural linkage within a 15 km left step that separates the surface traces of the fairview and dixie valley faults the west dipping faults likely played an important role in the redistribution of static stress from the fairview peak earthquake and subsequent triggering of the dixie valley earthquake right lateral offsets of more than a meter occurred along both the west gate and louder back mountains faults slip was limited to normal motion of 1 m or less along the gold king fault the change from right oblique motion along the fairview fault to pure normal motion on the dixie valley fault may reflect the transition from principally northwest extension in the south to more westerly extension in the north alternatively slip at the latitude of the dixie valley fault may be partitioned between pure normal slip along the dixie valley fault and strike slip motion on faults immediately to the west observations of fault dip provide insight to the complex three dimensional geometry of the rupture sequence of particular note a significant section of the dixie valley fault appears to be characterized by dip angles as low as 25 at the surface slip variation or earthquake endpoints do not generally appear to have been influenced by changes in bedrock type we do not observe systematic relations between slip variation and aspects of fault trace geometry such as salients and reentrants yet the relative competence of footwall bedrock appears to have influenced the long term development of large salients and reentrants along both the dixie valley and the fairview faults as well as the style of rupture along the southern portion of the dixie valley fault

using the composition of fluid seepage from the magmatic hydrothermal system of kawah ijen volcano indonesia as a monitoring tool abstract the lake waters of kawah ijen volcano are concentrated hyperacidic brines that obtain their composition from volcanic gases and water rock interaction lake water and hydrothermal fluids seep through the western flank of the volcano where they precipitate gypsum and form the hyperacid banyu pahit river in this contribution we present compositional data from bi weekly samples taken from the banyu pahit between 2015 and 2018 to evaluate whether these fluids can be used to monitor the hydrothermal system and compare the fluids to the record of variability documented by the precipitated gypsum understanding the causal links between variability of the banyu pahit and the magmatic hydrothermal processes operating in the kawah ijen system and establishing a baseline for quiescence are pre requisites to using the river for monitoring fluid samples were analysed at the ijen observatory for so4 cl ratio using baso4 turbidity and agcl gravimetry and subsequently sent for icp ms and icp oes analyses the data shows a first order seasonal variation that can be explained by variable input of neutral groundwater but is underlain by more subtle trends temporally there is a shift in the system from 2015 to 2016 to 2017 when the fluid contains a higher proportion of elements derived from rock alteration the shift occurs at the peak of the rainy season and coincides with a substantial rainfall increase in 2017 compared to 2015 2016 at the start of 2018 there is a marked increase in cu coinciding with a gas burst in march 2018 we suggest that an increased meteoric water input led to an increase in water rock interaction and dissolution of a cu sulphide phase in the hydrothermal system the variability of the fluids over the 3 year sampling period does not exceed that of the longer record preserved by the gypsum precipitates indicating that it is typical for the current style of activity

feldspar weathering as the key to understanding soil acidification monitoring data a study of acid sandy soils in the netherlands abstract monitoring activities pose special demands on the type of survey results needed in the early 1990s a soil acidification monitoring methodology was adopted in the netherlands that leaned heavily on methods developed in more fundamental research most notably the use of proton budgets consequently various controversies still not resolved in the scientific debate reflect on the current practice of soil acidity monitoring and complicate interpretation of the monitoring results in a pilot study we address the most pressing issues capacity versus intensity parameters choice of monitoring objective and natural variation in the compartment to be monitored focus is on the major source of buffering the possible usefulness of the historic approach and the regional patterns present in the sandy soils of the netherlands in a field campaign 92 locations in sandy regions all over the country were sampled at two depths the solid phase the displaced soil solution and solid phase extractions with 0 01 m cacl2 and 0 43 m hno3 for the 184 samples were analyzed by a variety of methods aluminum release is the major source of buffering and is shown to contribute substantially to acid buffering already under natural conditions the predominant al bearing phases in dutch sandy soils are feldspars and secondary al minerals feldspars are found to be the determinative phase in acid buffering application of the historic approach using the subsoil as a proxy for the initial composition of the topsoil proved feasible for this regional dataset the average depletion of the anc s of 230 mmolc kg 1 in the topsoil matches well with estimates of the total proton load since the last ice age with the anthropogenic contribution being between 20 and 50 fuzzy c means cluster analyses of the solid phase and soil solution data show a distinct regionality that was also reflected in the parameters generally used to indicate the acidity status of soils anc s and al bc ratios a combined insight into both solid phase and soil solution based on a comprehensive set of parameters proves essential for interpreting soil acidity monitoring data

neotectonics of the upper mississippi embayment abstract although the upper mississippi embayment is an area of low relief the region has been subjected to tectonic influence throughout its history and continues to be so today tectonic activity can be recognized through seismicity patterns and geological indicators of activity either those as a direct result of earthquakes or longer term geomorphic structural and sedimentological signatures the rate of seismic activity in the upper mississippi embayment is generally lower than at the margins of tectonic plates the embayment however is the most seismically active region east of the rocky mountains with activity concentrated in the new madrid seismic zone this zone produced the very large new madrid earthquakes of 1811 and 1812 geological and geophysical evidence of neotectonic activity in the upper mississippi embayment includes faulting in the benton hills and thebes gap in missouri paleoliquefaction in the western lowlands of missouri subsurface faulting beneath and tilting of crowley s ridge in northeastern arkansas and southeastern missouri subsurface faulting along the crittenden county fault zone near memphis tennessee faulting along the east flank of the tiptonville dome and numerous indicators of historic and prehistoric large earthquakes in the new madrid seismic zone paleoearthquake studies in the new madrid seismic zone have used trenching seismic reflection shallow coring pedology geomorphology archaeology and dendrochronology to identify and date faulting deposits of liquefied sand and areas of uplift and subsidence the cause of today s relatively high rate of tectonic activity in the mississippi embayment remains elusive it is also not clear whether this activity rate is a short term phenomenon or has been constant over millions of years ongoing geodetic and geological studies should provide more insight as to the precise manner in which crustal strain is accumulating and perhaps allow improved regional neotectonic models

seismic moment assessment of earthquakes in stable continental regions iii new madrid 1811 1812 charleston 1886 and lisbon 1755 summary the sizes of three major or great historical earthquakes are reassessed using the isoseismal area regression tools developed in parts i and ii of this study of stable continental region scr seismicity the earthquakes are 1811 new madrid central united states and its following sequence 1886 charleston coastal south carolina and 1755 lisbon oceanic intraplate off the continental shelf of portugal the analysis confirms the large size of these events and for the first time places constraints on the uncertainty of their seismic moment release because of the exceptionally low seismic wave attenuation of eastern north america ena a separate north american regression of seismic moment on isoseismal area was developed additionally the unknown western extents of the new madrid isoseismal areas were calibrated with the patterns of the m 6 3 6 6 1843 and 1895 earthquakes application of part ii analysis procedures with these corrections yields new madrid size estimates expressed as moment magnitude of m 8 1 0 31 for the 1811 december 16 m 7 8 0 33 for the 1812 january 23 and m 8 0 0 33 for the 1812 february 7 principal events the charleston earthquake s magnitude decreases from m 7 4 to m 7 3 0 26 after compensation for the effect of coastal plain sediments on its inner isoseismals intensity regressions for lisbon are calibrated against the isoseismal pattern of the nearly co located m 7 8 1969 st vincent earthquake which in this case increases the predicted size of lisbon from m 8 4 to m 8 7 0 39 these size estimates are supported by data from independent phenomena extent and severity of liquefaction the maximum distance of induced landslides and for lisbon tsunami wave amplitudes estimated source parameters are controlled by crustal or lithospheric temperature which governs the depth extent of brittle faulting using estimated continental and oceanic geotherms viable fault lengths are 30 80 km for charleston 120 180 km for 1811 new madrid and 180 280 km for lisbon for average displacements of 2 4 m 8 11 m and 10 14 m respectively and for average static stress and strain drops at the estimated seismic moments of this study the 1811 new madrid and the 1755 lisbon events are respectively the largest known scr and oceanic lithosphere earthquakes

the role of reversed equatorial zonal transport in terminating an enso event abstractthis study shows the sudden basinwide reversal of anomalous equatorial zonal transport above the thermocline at the peaking phase of enso triggers rapid termination of enso events the anomalous equatorial zonal transport is controlled by the concavity of anomalous thermocline meridional structure across the equator during the developing phase of enso opposite zonal transport anomalies form in the western central and central eastern equatorial pacific respectively both are driven by the equatorial thermocline anomalies in response to zonal wind anomalies over the western central equatorial ocean at this stage the anomalous zonal transport in the east enhances enso growth through zonal sst advection in the mature phase of enso off equatorial thermocline depth anomalies become more dominant in the eastern pacific because of the reflection of equatorial signals at the eastern boundary as a result the meridional concavity of the thermocline anomalies is reversed in the east this change reve

evidence for holocene displacements on the bootheel fault lineament in southeastern missouri seismotectonic implications for the new madrid region the 135 km long bootheel lineament is a zone of en echelon narrow linear bands of sand blows oriented n24 e in southeast missouri and northeast arkansas within the epicentral area of the 1811 1812 new madrid earthquakes holocene faulting along the central part of the lineament vertically displaced a 10 2 ka old pleistocene braid stream sand 3 m and dextrally displaced a ca 2 4 ka old holocene paleochannel at least 13 m the fault zone is less than 8 m wide where studied in detail these observations suggest that the bootheel lineament is a fault and we therefore suggest that it be renamed the bootheel fault the area east of the bootheel fault in our study area may have been uplifted 3 m during at least three holocene events perhaps by a compressional pop up at a 1 5 km wide left step restraining offset south of the study site the very low level of instrumental seismicity recorded near the bootheel fault suggests that it is either locked because of structural complexity or it is currently inactive though the source zones are poorly known great earthquake sequences in a d 1811 1812 a d 1450 and a d 900 have been identified in the new madrid seismic zone using the historical record and paleoseismology tuttle et al 2002 1 based on the estimated 13 m of horizontal paleochannel displacement an approximate 2 4 ka paleochannel age and a mean great earthquake recurrence interval of 500 yr cramer 2001 2 tuttle et al 2002 1 the local mean horizontal slip rate is estimated to be 3 5 m per event when displacement does occur on the bootheel fault it may subsequently load other faults accounting for past earthquake sequences in the new madrid region 1 ref 56 2 ref 7

tropical pacific variability in the ncar climate system model a 300 yr simulation with the ncar climate system model csm version 1 captured only 60 of the observed enso signal and exaggerated the interannual variability of sst in the western tropical pacific here a simulation with a new version of the csm which significantly improves the spatial and temporal patterns of tropical pacific variability is described maximum sst variability is shifted to the central and eastern pacific a better simulation of the equatorial pacific thermocline structure results in nino 3 and nino 4 statistics com parable to the observed estimates for the last century the evolution of sst and subsurface temperature anomalies is in excellent agreement with observed events the majority of events evolve as a standing mode with weak sst anomalies occurring in the northern spring in the eastern tropical pacific and maximum anomalies covering the eastern tropical pacific ocean to the date line by the following northern winter at the same time subsurface temperature anomalies spread eastward and upward along the tropical thermocline the delayed oscillator and wyrtki s buildup hypothesis are consistent with aspects of the csm simulation on the equator a westerly wind stress anomaly in the central pacific forces off equatorial upwelling anomalies which propagate westward reaching the western boundary about one half year later this upwelling signal then propagates eastward along the equator arriving 2 months before cooling in the eastern pacific basin the tropical pacific atmospheric response to warm oceanic events also agrees with observational analyses with a negative southern oscillation pattern in sea level pressure wind stress anomalies and low level convergence to the west of the maximum sst anomalies and enhanced deep convection and precipitation in the central and eastern tropical pacific

bathymetric and geochemical investigation of kawah ijen crater lake east java indonesia abstract a bathymetric survey of kawah ijen crater lake was conducted by acoustic sounding in 1996 to compare the lake morphology with those measured in 1922 1925 and 1938 and to calculate the present lake volume even though the lake experienced several hydrothermal eruptions the maximum depth became shallower 182 m than before 200 m resulting in a reduced lake volume 3 0 10 7 m 3 fifty two major and minor constituents including rare earth elements and polythionates pt of the lake waters at various depths were determined by icp aes icp ms and hplc respectively these ions except for several volatile elements are taken up by lake fringe through congruent dissolution of pyroclastics of kawah ijen volcano most ions are homogeneously distributed throughout the lake although pt showed a considerable vertical variation rare earth elements ree in the kawah ijen water as well as those from other hyper acidic crater lakes show distribution patterns likely due to the three rock dissolution preferential congruent and residual types and their logarithmic concentrations linearly depend upon the ph values of the lake waters using the pt degradation kinetics data production rates of pt injection rates of so 2 and h 2 s into the lake were estimated to be 114 86 and 30 tons day respectively also travel time of the spring water at the banyupahit riverhead from kawah ijen was estimated to be 600 1000 days through the consideration of decreasing rates of pt molten sulfur stocks containing sn cu bi sulfides and pb barite exposed on the inner crater slope were presumed to be extinct molten sulfur pools at the former lake bottom this was strongly supported by the barite precipitation temperature estimated through the consideration of the temperature dependence of pb chlorocomplex formation

future trends in paleoseismology integrated study of the seismic landscape as a vital tool in seismic hazard analyses this paper forms the introduction to this special issue of tectonophysics devoted to selected scientific research presented during events sponsored by the inqua subcommission on paleoseismicity in the past few years in this note we summarize the contents of the contributed papers and use the issues they raise to review the state of the art in paleoseismology from a quaternary geology perspective in our opinion the evolution of paleoseismological studies in the past decade clearly demonstrates that in order to properly understand the seismic potential of a region and to assess the associated hazards broad based multidisciplinary studies are necessary to take full advantage from the geological evidence of past earthquakes a major challenge in future paleoseismic research is to build detailed empirical relations between various categories of coseismic effects in the natural environment and earthquake magnitude intensity these relations should be compiled in a way that is fully representative of the wide variety of natural environments on earth in terms of climatic settings quaternary tectonic evolution rheological parameters of the seismogenic crust and stress environment for instance available data indicate that between earthquake magnitude and surface faulting parameters different scaling laws exist and they are a function of the local geodynamic setting including style of faulting typical focal depths heat flow in this regard we discuss in some detail the concept of seismic landscape which provides the necessary background for developing paleoseismological research strategies the large amount of paleoseismological data collected in recent years shows that each earthquake source creates a signature on the geology and the geomorphology of an area that is unequivocally related with the order of magnitude of its earthquake potential this signature is defined as the seismic landscape of the area e g serva l vittori e ferreli l michetti a m 1997 geology and seismic hazard in grellet b mohammadioun b hays w eds proceedings of the second france united states workshop on earthquake hazard assessment in intraplate regions central and eastern united states and western europe october 16 1995 nice france 20 24 ouest editions nantes france michetti a m hancock p l 1997 paleoseismology understanding past earthquakes using quaternary geology

paleoseismic evidence for multiple mw 6 earthquakes in the eastern tennessee seismic zone during the late quaternary abstract the eastern tennessee seismic zone etsz is the second most active seismic zone in the eastern united states but it has not generated an earthquake larger than m w 4 8 in historic time earthquakes are sourced deep in autochthonous basement and there are no known faults originating at this depth that break the surface as a result until recently there has been virtually no fieldwork to identify quaternary paleoseismic features in the etsz we present new results from paleoseismic investigations of coseismic features that indicate the etsz generated m w 6 earthquakes during the late quaternary detailed geologic mapping and trenching near dandridge tennessee record a northeast trending zone of seismically generated features optically stimulated luminescence ages delimit timing for the formation of paleoseismic features crosscutting quaternary alluvium and alluvium filled fissures including a thrust fault with 1 m displacement collectively this zone of faults and fissures provides significant evidence that the etsz has produced at least three large earthquakes during the late pleistocene and at least one that exceeded m w 6

an assessment of differences in enso mechanisms in a coupled gcm simulation abstract this study investigates the physical mechanisms involved in the generation and decay of el nino southern oscillation episodes in a coupled gcm simulation warm and cold events found in a 100 yr long record are separated into groups by means of a clustering technique that objectively discriminates common features in the evolution of the tropical pacific heat content anomalies leading to the event s peak through an analysis of the composites obtained from this classification insight is gained as to the processes responsible for the presence of different behaviors three classes of warm events were identified the first is characterized by the westward propagation of warm heat content anomalies north of the equator before the onset of the episode this propagation characteristic of the delayed oscillator paradigm appears weakened in the decay of the episode in the second class local development of heat content anomalies in the northwest tropical pacific associated with overlying wind stress cur

response of alluvial rivers to slow active tectonic movement alluvial rivers respond to valley slope deformation caused by active tectonics in various ways depending on the rate and amount of surficial deformation and on the type of river on the basis of experimental results and field examples hypothetical models of river response to anticlinal uplift and synclinal subsidence were developed for different types of alluvial rivers an experimental braided channel responded to anticlinal uplift across the channel with degradation and terrace formation in the central part of the uplift with subsidence aggradation in the central reach was the main response transverse bars developed downstream of the subsidence axis an experimental meandering channel responded to slope steepening with a sinuosity increase bank erosion and point bar growth occurred downstream of the anticlinal axis and upstream of the synclinal axis upstream of the uplift axis and downstream of the subsidence axis where the slope was flattened water flooded over bars local convexity in longitudinal profiles of the middle rio grande new mexico is considered to be formed by a domal uplift local aggradation and degradation could be explained by the effect of uplift the san joaquin river california which is now highly controlled does not show clear adjustment to the rapid subsidence due to ground water withdrawal it shows however a channel pattern adjustment to active tectonic subsidence that has been occurring for a long time the san antonio and guadalupe rivers in texas both increase their sinuosity significantly where monoclinal movements steepen valley slopes

paleoseismology of the johnson valley kickapoo and homestead valley faults clustering of earthquakes in the eastern california shear zone paleoseismic data from 11 trenches at seven sites excavated across the southern johnson valley kickapoo and homestead valley faults that ruptured in the 1992 landers earthquake as well as the northern johnson valley fault which did not fail in 1992 indicate that the return period for large surface rupturing events in this part of the eastern california shear zone is in the range of 5 15 ka the inferred slip rates based on their respective recurrence intervals are in the range of 0 2 0 6 mm yr for each of the faults studied a previous large earthquake ruptured the southern johnson valley and kickapoo faults about 5 ka b p the northern johnson valley fault also failed at about this time at 5 8 ka b p and may have been part of the same rupture in contrast the penultimate large earthquake that we identify on the homestead valley fault occurred about 15 ka b p much earlier than other faults involved in the 1992 rupture from these observations combined with paleoseismic work by others after the 1992 earth quake it appears that previous events along the southern johnson valley and kick apoo faults were different than those of 1992 and may have involved other fault segments it has been over 5 ka since the most recent rupture on the northern johnson valley fault therefore it is surprising that it did not fail in the 1992 rupture from our observations dextral shear appears to be distributed across the entire eastern california shear zone with individual faults taking only a small proportion of the overall slip release of this regional strain appears to occur in temporal clusters of large earthquakes with the 1992 event apparently the most recent of a sequence of late holocene 0 1 ka earthquakes that have ruptured the nine faults we have trenched in the southwestern mojave desert previous clusters of earthquake activity occurred in the early 8 9 ka and middle 5 6 ka holocene and possibly the latest pleistocene 15 ka

evidence for earthquake induced subsidence about 1100 yr ago in coastal marshes of southern puget sound washington buried forest and high marsh soils indicate abrupt changes in relative sea level at four coastal localities in southern puget sound at little skookum inlet and red salmon creek douglas fir stumps in growth position are buried by salt marsh peat at localities along mcallister creek and the nisqually river high marsh soils are buried by tidal flat mud localized liquefaction coincided with submergence of the high marsh soil at mcallister creek dramatic changes in seed and diatom assemblages across these contacts confirm rapid submergence at little skookum inlet and red salmon creek salt marsh peat immediately above a buried forest soil contains diatoms indicative of low marsh and tidal flat environments at mcallister creek and nisqually river low marsh and tidal flat diatoms are abundant in laminated mud directly over high marsh peat inferences from modern analogs indicate at least 1 m of subsidence at each site and possibly up to 3 m at skookum inlet abrupt burial of lowland soils in southern puget sound is best explained by coseismic subsidence some of the submergence may be the result of coseismic compaction and postearthquake settlement widespread buried soils large amounts of subsidence coeval submergence across a wide area and ground shaking at the time of subsidence all point to a large earthquake between 1150 and 1010 cal yr b p in southern puget sound as the most likely cause of subsidence

origin and age of the manila high and associated big lake sunklands in the new madrid seismic zone northeastern arkansas uplift of the manila high and subsidence of the south flowing little river during the great new madrid earthquakes of 1811 1812 formed the present lake in big lake basin of northern arkansas this is the most recent deformation of the 19 km long manila high that began between 11 000 and 5400 yr ago and is time transgressive toward the south at least 4 m of holocene uplift occurred on the northern portion of the manila high prior to initiation of the little river distributary in mid holocene time the distributary is deflected around the high and overbank sediment derived from it thins and is locally absent across the northern highest portion of the high deformation along the southern end of the high began between 3500 and 2000 yr ago since 3500 yr b p 2 m of uplift appears to have caused a reduction in gradient anastomosing upstream of the uplift and incision of the little river across the uplift north of the manila high in the big lake basin the little river has an increased aggradation rate 10 times that of the preuplift rate cores collected in and adjacent to big lake indicate that the little river was ponded twice apparently in response to deformation in 1811 1812 and between 90 b c and a d 1640

alluvial river response to neotectonic deformation in louisiana and mississippi repeat geodetic surveys show uplift of the monroe and wiggins anticlines in louisiana and mississippi there are deformed quaternary terraces which indicate long term deformation in the valleys of the alluvial rivers that cross these structures and there are floodplain and channel convexities that provide evidence of modern deformation in addition the channels show significant variations of morphology sinuosity gradient and depth and behavior appropriate to reaches of increased and decreased valley slope these alluvial rivers are adjusting to modern deformation and their adjustment confirms two geodetic leveling anomalies

geometry numerical models and revised slip rate for the reelfoot fault and trishear fault propagation fold new madrid seismic zone abstract the geometry and structural relief of late holocene sediments folded across the reelfoot scarp are characterized with trench excavations shallow borings a digital elevation model dem of topography and reelfoot lake rl bathymetry results suggest the scarp forms by heterogeneous shear in the forelimb of a fault propagation fold seismic data and the accompanying structural analysis support the argument that the reelfoot fault does not offset the surface and that the reelfoot scarp is a fold limb structural relief measured across the reelfoot scarp is slightly higher than previous determinations and varies from 7 to 11 m along the western shoreline of rl numerical models based on trishear kinematics constrain growth of the reelfoot monocline and indicate that the underlying reelfoot thrust fault is steeply dipping the shallowest portion of the central reelfoot thrust segment dips 75 where the fault tip has propagated upward from 911 m to its current location 465 m beneath the surface the models indicate that the shallowest section of the southern thrust segment in the reelfoot thrust system dips even more steeply at 80 but has propagated upward only a few tens of meters to its present location 1016 m beneath the surface the thrust is flatter at deeper levels based on the location of earthquake hypocenters strain across the reelfoot scarp is partitioned into two or three separate fold scarps that collectively record a late holocene fault slip rate of 3 9 0 1 mm yr the slip rate is based on 9 m of structural relief the 2290 60 ybp age of folded sediment and a 75 dip for the fault this implies a rate of horizontal contraction in the seismic zone of 1 0 mm yr this rate is strongly dependent on the dip of the thrust calculated by the structural analysis the numerical models argue for reactivation of faults that previously offset paleozoic strata

displacement history and slip rate on the reelfoot fault of the new madrid seismic zone abstract a displacement history and slip rates were determined for the reelfoot fault in the new madrid seismic zone from a seismic reflection profile and trench data based on calculations from the seismic reflection line the average slip rate over the last 80 million years is 0 0009 mm year 1 slip rate during the late cretaceous was 0 0007 mm year 1 0 002 mm year 1 during the paleocene midway group 0 001 mm year 1 during paleocene eocene wilcox formation time 0 0003 mm year 1 during the post wilcox pre holocene period and a holocene slip rate of 1 8 mm year 1 based on trench data slip rate on the reelfoot fault has been 4 4 mm year 1 over the last 2400 years and a maximum of 6 2 mm year 1 during the two most recent earthquake cycles between ad 900 and ad 1812 the holocene slip rate is at least four orders of magnitude higher than the average late cretaceous and cenozoic slip rates for the reelfoot fault it would appear that there has been a quaternary change in the stress field in the central united states or the reelfoot fault is experiencing a short lived burst of seismic activity

stratigraphic evidence for millennial scale temporal clustering of earthquakes on a continental interior fault holocene mississippi river floodplain deposits new madrid seismic zone usa abstract the earthquake cycles that characterize continental interior areas that are far from active plate boundaries have proven highly cryptic and difficult to resolve we used a novel paleoseismic proxy to address this issue namely we reconstructed holocene mississippi river channels from maps of floodplain strata in order to identify channel perturbations reflective of major displacement events on the high hazard and mid plate reelfoot thrust fault new madrid seismic zone u s a only three discrete slip events are currently documented for the reelfoot fault ad 900 ad 1450 and ad 1812 this study extends this record and thus illustrates the utility of stratigraphic proxies as paleoseismic tools we concurrently offer here some of the first quantified response times for tectonically induced channel pattern changes in large alluvial rivers we identified at least two cycles of pervasive meandering that were interrupted by channel straightening responses occurring upstream of the reelfoot fault scarp these straightening responses initiated at 2244 bc 269 to 1620 bc 220 and ad 900 respectively and each records initiation of a period of reelfoot fault slip after millennia of relative tectonic quiescence the second or new madrid straightening response was triggered by the previously known ad 900 fault slip event and this initial low sinuosity has been protracted until the modern day by the latter ad 1450 and ad 1812 events the first or bondurant straightening response began a period of several hundred to 1400 years of low river sinuosity which evidences a similar period of multiple recurrent displacement events on the reelfoot fault these bondurant events predate the existing paleoseismic record for the reelfoot fault these data offer initial evidence that slip events on the reelfoot fault were temporally clustered on millennial scales and thus offers the first direct evidence for millennial scale clustering of earthquakes on a continental interior fault this carries additional ramifications namely faults that have been quiescent and non hazardous for millennia could re enter an enduring period of recurrent hazardous earthquakes with little warning likewise the reelfoot fault also reveals evidence of temporal clustering of earthquakes on short term cycles months as well as evidence for longer term reactivation cycles 10 4 10 6 years this introduces the possibility that temporal clustering could be hierarchical on some continental interior faults

geologic evidence of earthquakes at the snohomish delta washington in the past 1200 yr exposed channel banks along distributaries of the lower snohomish delta in the puget lowland of washington reveal evidence of at least three episodes of liquefaction at least one event of abrupt subsidence and at least one tsunami since ca a d 800 the 45 measured stratigraphic sections consist mostly of 2 4 m of olivegray intertidal mud containing abundant marsh plant rhizomes the most distinctive stratigraphic unit is a couplet comprising a 0 523 cm thick laminated fining upward tsunami laid sand bed overlain by 2210 cm of gray clay we correlated the couplet which is generally 2 m below the modern marsh surface across an 20 km2 area sand dikes and sand filled cracks to 1 m wide which terminate upward at the couplet and sand volcanoes preserved at the level of the sand bed record liquefaction at the same time as couplet deposition differences in the type and abundance of marsh plant rhizomes across the couplet horizon as well as the gray clay layer suggest that compaction during this liquefaction led to abrupt local lowering of the marsh surface by as much as 50 75 cm radiocarbon ages show that the tsunami and liquefaction date from ca a d 800 to 980 similar to the age of a large earthquake on the seattle fault 50 km to the south we have found evidence for at least two and possibly as many as five other earthquakes in the measured sections at two or more stratigraphic levels above the couplet sand dikes locally feed sand volcanoes radiocarbon ages and stratigraphic position gov suggest that one set of these dikes formed ca a d 910 990 radiocarbon ages on a younger set indicate a limiting maximum age of a d 1400 1640 we also interpret a sharp lithologic change from olive gray rhizome rich mud to grayer rhizome poor mud 1 m above the couplet to indicate a second abrupt lowering of the marsh surface during an earthquake ca a d 1040 1400 but no conclusive liquefaction structures have been identified at this horizon two distinctive coarse sand laminae 30 80 cm below the couplet may record tsunamis older than a d 800 thus study shows that in the past 1200 yr this part of washington s puget lowland has been subjected to stronger ground shaking than in historic times since ca 1870

geomorphic indicators of active fold growth south mountain oak ridge anticline ventura basin southern california south mountain oak ridge near ventura california is an asymmetric anticlinal uplift forming at the present time above the active buried oak ridge reverse fault shortening along the oak ridge fault accumulated largely in quaternary time and is responsible for the growth and present topography of the westernmost 15 km of the ridge during the past 0 5 m y tectonic geomorphic analysis using several indices of active tectonics provides information concerning fold growth stream gradient indices are relatively high in the northern eroded fold scarp of the ridge a pattern consistent with the existence of active rapid slip on the oak ridge fault mountain front sinuosity along the northern slope of the anticlinal ridge roughly decreases from 2 to 1 toward the westernmost 10 km of observed surface folding valley floor width to valley height ratios along the northern flank of the ridge generally decrease westward from 1 5 to 0 5 values of the hypsometric integral along the northern flank increase significantly from 0 35 to 0 4 maximum 0 55 from east to west drainage density varies from 4 to 6 km km2 along both flanks of the south mountain oak ridge anticline entrenchment of streams into the southern backlimb of the fold along the westernmost 9 km of the structure decreases from 20 m to 1 m from east to west apparent backlimb rotation as measured by dip of strata along the westernmost 7 km of the fold decreases from east to west from 35 to 20 fold growth of the south mountain oak ridge anticline occurred during the past 0 5 ma following deposition of the saugus formation lateral and vertical fold growth were likely produced by westward decrease in fault slip along the buried oak ridge fault

stress drop slip type earthquake magnitude and seismic hazard care must be taken to provide reliable antiseismic protection in earthquake prone areas where the impact of a large earthquake in megacities with industrial facilities as well as in ordinary buildings is liable to cause massive loss of human life and to cripple the nation s economy this protection needs to take into account not only vibratory ground motion but also permanent ground failure and notably surface faulting hazard a fact tragically illustrated during the recent events of turkey and taiwan the purpose of this contribution is to conduct a survey of our current state of knowledge concerning theoretical relationships between earthquake source parameters such as moment magnitude m m w surface wave magnitude m s seismic moment m o stress drop rupture length l and displacement on the fault d a relationship is proposed that links m s to l and m s 2 log l 1 33 log 1 66 using a simple rupture model earthquake data from all over the world for which the parameters of rupture length fault width w fault displacement and surface wave magnitude are available have enabled stress drop values to be computed for each event using both geological observation 1 and the previously proposed equation 2 the results obtained tend to indicate that stress drop values increase versus fault width depth up to approximately 15 km corresponding perhaps to the brittle ductile boundary this increase is more pronounced in the case of reverse faults than it is for those with strike slip or normal mechanisms an equation of the type kw n has been used to fit the data and preliminary values for k and n have been supplied for the three slip types for depths in excess of 15 km the data do not display significant variation 100 bars these results are in agreement with certain laboratory models of the continental lithosphere although more data particularly in the large magnitude range are needed to ascertain whether it is the w or the l model that better describes earthquake scaling laws stress drop does not appear to be fault length dependent thus being supportive of the l model the risk of surface faulting is dependent on the dynamic environment of the fault that is the stress drop the rupture length and the fault width although statistics show that surface faulting appears in most instances at magnitudes of at least 6 1 data from certain regions indicate that seismicity at superficial depths is under certain conditions accompanied by significant surface faulting even for magnitudes as small as 5 5 suggesting a change in scaling law the threshold magnitude for surface faulting is accordingly seen to depend on the rheology of materials in the fault area and on the stress environment manuscript received 31 may 2000

an optical age chronology of late pleistocene fluvial deposits in the northern lower mississippi valley the lower mississippi valley lmv contains many large braided channel belts that are preserved west of the holocene floodplain previous efforts to establish geochronologic control on channel belt construction have been hindered by the lack of organic material for radiocarbon dating luminescence techniques provide a burial date for the sediment itself and may prove useful in this context samples from three channel belts in the northern lmv were analyzed using the single aliquot regenerative technique on 90 125mm quartz optical ages 19 7 17 8 16 1 15 0 and 12 5 12 1 ka are consistent with geomorphic relationships and indicate that channel belts were formed in the late pleistocene under glacial conditions these optical ages provide the first detailed chronology of lmv channel belt formation and are the first step towards developing a chronology for the entire lmv r 2003 elsevier science ltd all rights reserved

enso simulated by intermediate coupled models and evaluated with observations over 1970 98 part i role of the off equatorial variability enso simulations are investigated in 30 yr integrations of various intermediate coupled models and compared with observed sst wind and thermocline depth anomalies over the tropical pacific the cane and zebiak model simulates warm events with a period close to the observations but with westerlies that are located 30 8 east of them and thermocline anomalies in the western pacific that are much shallower between two warm events the model simulates a series of three weak and short cold sst peaks and hardly ever simulates easterlies the sst in the eastern equatorial pacific is not sensitive to thermocline depth anomalies but to the anomalous downwelling of surface currents induced by ekman shear the model simulates a pair of very strong cyclonic wind stress curl anomalies on both sides of the equator in the eastern off equatorial domain between 78 and 158 lat these are necessary to maintain the oscillatory regime so are the ocean meridional rossby modes higher than 5 the thermocline zonal slopes required to balance the off equatorial curl anomalies are about three times steeper than the ones required to balance the zonal stress along the equator thus the off equator exerts an excess of zonal pressure which by continuity affects the equatorial ocean and plays a crucial role in reversing and triggering the growing events six months after the warm peaks the whole ocean between 158s and 158n is significantly upwelled the equatorial oceanic heat content is recharged from the south prior to a warm event contrary to simulations when the model is driven by observed wind anomalies increasing the friction in the baroclinic ocean does not decrease the off equatorial variability but significantly alters the low frequency oscillations that are no longer enso like introducing the parameterization of subsurface temperature derived from hydrographic profiles in the ocean component does not allow the coupled model to recover cold events as in a forced context introducing the parameterization of convection derived from high cloud temperature measurements is the most effective improvement but results still poorly agree with observations and are in contrast with the simulations driven by observed sst biased toward westerlies in the central pacific upwelled thermocline in the west and warm sst in the east thus modifying the ocean component only or the atmosphere only does not have the same impact on simulations as in a forced context the coupling allows new mechanisms to grow and govern the model behavior one of them is the slow meridional oceanic mass adjusment in quasi sverdrup balance with the winds

impact of acid effluent from kawah ijen crater lake on irrigated agricultural soils soil chemical processes and plant uptake abstract volcanogenic contamination of irrigation water caused by effluent from the hyperacid ijen crater lake has severely affected the properties of agricultural soils in east java indonesia from a comparison of acidified topsoil with subsoil and with top and subsoil in a reference area we identified processes responsible for changes in soil and soil solution chemistry induced by acid irrigation water with emphasis on the nutrients ca mg fe and mn and on al which may become phytotoxic under acid conditions in soils compositional data for bulk soil composition and selective extractions with 1 m kcl and 0 2 m acid ammonium oxalate are used in a mass balance approach to specify element fluxes including uptake by rice plants the results show that input via irrigation water has produced an increase in the total aluminum content in the affected topsoil which is of the same order of magnitude as the increase in labile al high bioavailability of al as reflected by concentrations in kcl extracts is consistent with elevated concentrations observed in rice plants in contrast and despite the high input via irrigation water ca and mg concentrations have decreased in all measured soil fractions through dissolution of amorphous phases and minerals and through competition of al for adsorption sites on the exchange complex and plant roots strong leaching is also evident for fe and especially mn in terms of the overall mass balance of the topsoil plant uptake of al ca fe mg and mn is negligible if the use of acid irrigation would be stopped and the soil ph were to increase to values above 4 5 the observed phytotoxicity of al will be halted however crops may then become fully dependent on the input from irrigation water or fertilizer for essential elements due to the previous removal from the topsoil through leaching

geochemistry mineralogy and chemical modeling of the acid crater lake of kawah ijen volcano indonesia the kawah ijen volcano with a record of phreatic eruptions has its 1000 m wide crater filled with a lake that has existed for at least one century at present the lake waters are hot t 37 c strongly mineralized tds 105 g l and extremely acidic ph 0 4 by its volume the javanese lake is probably the largest accumulation in the world of such acidic waters mineralogy of the suspended solids within the lake waters suggests that concentrations of si ca ti and ba are controlled by precipitation of silica gypsum anatase and barite lake sediment is composed of chemical precipitates with composition similar to the suspended solids thermodynamic calculations predict that the lake waters have reached equilibrium with respect to cristobalite barite gypsum anglesite celestite and amorphous silica in agreement with the analytical observations significant concentrations of ferric iron suggest that the current lake waters are fairly oxidized sulfides are absent in the water column but are always present in the native s spherules that form porous aggregates which float on the lake the presence of native s provides direct evidence of more reduced conditions at the lake floor where h 2 s is probably being injected into the lake with progressive addition of h 2 s to the acid waters native s pyrite and enargite are theoretically predicted to be saturated reactions between upward streaming h 2 s bearing gases discharged by subaqueous fumaroles and metals dissolved in the acidic waters could initiate precipitation of these sulfides a model of direct absorption of hot magmatic gases into cool water accounts for the extreme acidity of the crater lake results show that strongly acidic sulfate rich solutions are formed under oxidizing conditions at high gas water ratios reactions between the acidic fluids and the ijen andesite were modeled to account for elevated cation concentrations in lake water current concentrations of conservative rockforming elements are produced by dissolution of approximately 60 g of andesite per kg of acid solution complete neutralization of the acid lake waters by reaction with the wallrock produces a theoretical alteration assemblage equivalent to that observed in volcano hosted acid sulfate epithermal ore deposits

downstream composition changes of acidic volcanic waters discharged into the banyupahit stream ijen caldera indonesia abstract the crater lake of kawah ijen volcano contains extremely low ph we discuss the downstream composition changes affecting the banyupahit waters by using stable isotope chemical and mineralogical data collected from sites along the stream length the saturation of the stream waters with respect to minerals was evaluated with solveq and wateq4f and compared with the geochemical observations an aluminous mineralogy alunogen pickeringite tamarugite and kalinite develops in the upper part of the banyupahit due to concentration of the headwaters by evaporation downstream attenuation of dissolved element concentrations results principally from dilution and from mineral precipitation the stream ph changes from 0 at the source to 4 close to the mouth the d and 18o values and the relative so4 cl f contents of the banyupahit waters indicate that the tributaries are mostly meteoric dissolved so4 in the acidic stream come only from the crater lake seepages and are not involved later in microbially mediated reactions as shown by their 34s and 18o values re equilibration of the stream so4 oxygen isotope composition with h2o from tributaries does not occur calcium sio2 al fe k and so4 behave non conservatively in the stream waters gypsum silica amorphous or poorly ordered a basic aluminum hydroxysulfate basaluminite k jarosite and amorphous ferric hydroxide may exert a solubility control on these elements along the entire stream length or in certain stream sections consistent with the thermochemical model results downstream concentration trends and mineral saturation levels suggest that precipitation of sr pb rich barite and celestite consume ba sr and pb whereas dissolved cu pb and zn may adsorb onto solid particles especially after the junctions of the acidic stream with non acidic rivers we calculated that significant fluxes of so4 f cl al sio2 ti mn and cu may reach the irrigation system possibly causing serious environmental impacts such as soil acidification and induration

the earthquake potential of the new madrid seismic zone the fault system responsible for new madrid seismicity has generated temporally clustered very large earthquakes in a d 900 100 years and a d 1450 150 years as well as in 1811 1812 given the uncertainties in dating liquefaction features the time between the past three new madrid events may be as short as 200 years and as long as 800 years with an average of 500 years this advance in understanding the late holocene history of the new madrid seismic zone and thus the contemporary tectonic behavior of the associated fault system was made through studies of hundreds of earthquake induced liquefaction features at more than 250 sites across the new madrid region we have found evidence that prehistoric sand blows like those that formed during the 1811 1812 earthquakes are probably com pound structures resulting from multiple earthquakes closely clustered in time or earthquake sequences from the spatial distribution and size of sand blows and their sedimentary units we infer the source zones and estimate the magnitudes of earth quakes within each sequence and thereby characterize the detailed behavior of the fault system it appears that fault rupture was complex and that the central branch of the seismic zone produced very large earthquakes during the a d 900 and a d 1450 events as well as in 1811 1812 on the basis of a minimum recurrence rate of 200 years we are now entering the period during which the next 1811 1812 type event could occur

recognition of earthquake related damage in archaeological sites examples from the dead sea fault zone abstract archaeological structures that exhibit seismogenic damage expand our knowledge of temporal and spatial distribution of earthquakes afford independent examination of historical accounts provide information on local earthquake intensities and enable the delineation of macroseismic zones they also illustrate what might happen in future earthquakes in order to recover this information we should be able to distinguish earthquake damage from anthropogenic damage and from other natural processes of wear and tear the present paper reviews several types of damage that can be attributed with high certainty to earthquakes and discusses associated caveats in the rare cases where faults intersect with archaeological sites offset structures enable precise determination of sense and size of slip and constrain its time among the characteristic off fault damage types i consider horizontal shifting of large building blocks downward sliding of one or several blocks from masonry arches collapse of heavy stably built walls chipping of corners of building blocks and aligned falling of walls and columns other damage features are less conclusive and require additional evidence e g fractures that cut across several structures leaning walls and columns warps and bulges in walls circumstantial evidence for catastrophic earthquake related destruction includes contemporaneous damage in many sites in the same area absence of weapons or other anthropogenic damage stratigraphic data on collapse of walls and ceilings onto floors and other living horizons and burial of valuable artifacts as well as associated geological palaeoseismic phenomena such as liquefaction land and rock slides and fault ruptures additional support may be found in reliable historical accounts special care must be taken in order to avoid circular reasoning by maintaining the independence of data acquisition methods

multiple late holocene earthquakes along the reelfoot fault central new madrid seismic zone the reelfoot fault is an east vergent reverse fault underlying the lake county uplift a low amplitude late holocene anticline bordered on the east by the 32 km long reelfoot scarp fluvial deposits across the scarp define an 8 m high east facing monocline most near surface deformation along the scarp is accommodated via folding rather than faulting we interpret the scarp as a fault propagation fold developed over a wcst dipping reverse fault interpreted from shallow seismic reflection data trench exposurcs provide evidence for three episodes of deformation along the reelfoot fault within thc past approximately 2400 years between a d 780 and 1000 between a d 1260 and 1650 and during a d 1812 our best estimate of the average recurrence interval for deformation along the scarp is 400 500 years each episode of deformation had a slightly different style the third most recent event produced a small graben a few tens of centimeters deep in the hanging wall of the reverse fault the second most recent earthquake produced about 1 3 m of throw in the graben as well as folding along the updip projection of the reverse fault and development of the scarp thesc relations suggest that graben development increased through time concomitant with growth of the monocline or that the events are of different magnitude the 1811 1812 episode of deformation produced abundant liquefaction prominent folding of fluvial strata along the scarp and minor faulting in the graben

triggering of el nino by westerly wind events in a coupled general circulation model two ten members ensemble experiments using a coupled ocean atmosphere general circulation model are performed to study the dynamical response to a strong westerly wind event wwe when the tropical pacific has initial conditions favourable to the development of a warm event in the reference ensemble cref no wind perturbation is introduced whereas a strong westerly wind event anomaly is introduced in boreal winter over the western pacific in the perturbed ensemble cwwe our results demonstrate that an intense wwe is capable of establishing the conditions under which a strong el nino event can occur first it generates a strong downwelling kelvin wave that generates a positive sea surface temperature sst anomaly in the central eastern pacific amplified through a coupled ocean atmosphere interaction this anomaly can be as large as 2 5 c 60 days after the wwe secondly this wwe also initiates an eastward displacement of the warm pool that promotes the occurrence of subsequent wwes in the following months these events reinforce the initial warming through the generation of additional kelvin waves and generate intense surface jets at the eastern edge of the warm pool that act to further shift warm waters eastward the use of a ten members ensemble however reveals substantial differences in the coupled response to a wwe whereas four members of cwwe ensemble develop into intense el nino warming as described above four others display a moderate warming and two remains in neutral conditions this diversity between the members appears to be due to the internal atmospheric variability during and following the inserted wwe in the four moderate warm cases the warm pool is initially shifted eastward following the inserted wwe but the subsequent weak wwe activity when compared to the strong warming cases prevents to further shift the warm pool eastwards the seasonal strengthening of trade winds in june july can therefore act to shift warm waters back into the western pacific reducing the central eastern pacific warming this strong sensitivity of the coupled response to wwes may therefore limit the predictability of el nino events as the high frequency wind variability over the warm pool region remains largely unpredictable even at short time lead

structure of the lake county uplift new madrid seismic zone abstract the central segment of the new madrid seismic zone lies within a left step over zone between two northeast striking right lateral strike slip fault systems within this compressional step over zone is the topographically and structurally high lake county uplift which includes the tiptonville dome and ridgely ridge we believe these structures are a consequence of deformation in the hanging wall above the northwest striking southwest dipping reelfoot reverse fault reelfoot fault dips 73 from the surface to the top of the precambrian at a depth of approximately 4 km from 4 to 12 km depth the fault dips 32 and is seismically active based on a fault bend fold model we believe that the reelfoot fault becomes horizontal and aseismic at the top of the quartz brittle ductile transition zone at approximately 12 km depth our data indicate that the western margin of the tiptonville dome ridgely ridge and the western margin of the lake county uplift are bounded by east dipping kink bands backthrusts recent work suggests that the reelfoot fault is responsible for the 7 february 1812 m 8 new madrid earthquake however the reelfoot fault has a surface area that is less than that necessary for an m 8 earthquake a possible solution to this discrepancy between magnitude and fault plane area is that the associated backthrusts are seismogenic

reconciling short recurrence intervals with minor deformation in the new madrid seismic zone at least three great earthquakes occurred in the new madrid seismic zone in 1811 and 1812 estimates of present day strain rates suggest that such events may have a repeat time of 1000 years or less paleoseismological data also indicate that earthquakes large enough to cause soil liquefaction have occurred several times in the past 5000 years however pervasive crustal deformation expected from such a high frequency of large earthquakes is not observed this suggests that the seismic zone is a young feature possibly as young as several tens of thousands of years old and no more than a few million years old

geoarchaeological evidence of strong prehistoric earthquakes in the new madrid missouri seismic zone sand blows and fissures that cover 10 500 km sup 2 in northeastern arkansas and southeastern missouri attest to the severity of the 1811 1812 earthquake series in the new madrid seismic zone however except for one occurence near new madrid missouri the region has been devoid of any evidence of other major shocks for at least 1 3 ka prior to 1811 and possibly for 9 ka stratigraphic relations and radiocarbon dating at a recently excavated archaeological site near east prairie missouri have revealed liquifaction phenomena attributable to a shock dated to within about 100 yr prior to a d 539 and a probable second one dated between about a d 539 and 991

evidence of boundary reflection of kelvin and first mode rossby waves from topex poseidon sea level data the topex poseidon sea level data lead to new opportunities to investigate some theoretical mechanisms suggested to be involved in the el nino southern oscillation phenomenon in the tropical pacific ocean in particular we are interested in studying the western boundary reflection a process crucial for the delayed action oscillator theory by using the topex poseidon data from november 1992 to may 1995 we first projected the sea level data onto kelvin and first mode rossby waves then we estimated the contribution of wind forcing to these waves by using a single baroclinic mode simple wave model forced by the ers 1 wind data wave propagation was clearly observed with amplitudes well explained by the wind forcing in the ocean interior evidence of wave reflection was detected at both the western and eastern boundaries of the tropical pacific ocean at the eastern boundary kelvin waves were seen to reflect as first mode rossby waves during the entire period the reflection efficiency in terms of wave amplitude of the south american coasts was estimated to be 80 of that of an infinite meridional wall at the western boundary reflection was observed in april august 1993 in january june 1994 and later in december 1994 to february 1995 although the general roles of these reflection events in the variability observed in the equatorial pacific ocean are not clear the data suggest that the reflections in january june 1994 have played a role in the onset of the warm conditions observed in late 1994 to early 1995 indeed during the january june 1994 period as strong downwelling first mode rossby waves reflected into downwelling kelvin waves easterly wind and cold sea surface temperature anomalies located near the date line weakened and eventually reversed in june july 1994 the presence of the warm anomalies near the date line then favored convection and westerly wind anomalies that triggered strong downwelling kelvin waves propagating throughout the basin simultaneously with the beginning of the 1994 1995 warm conditions

stream response to repeated coseismic folding tiptonville dome new madrid seismic zone abstract fluvial response to tectonic deformation is dependent on the amount and style of surface deformation and the relative size of the stream active folding in the new madrid seismic zone nmsz forms the tiptonville dome a 15 km long and 5 km wide surface fold with up to 11 m of late holocene structural relief the fold is crossed by streams of varying size from the mississippi river to small flood plain streams fluvial response of these streams to repeated coseismic folding has only been preserved for the past 2 3 ka since the tiptonville meander of the mississippi river migrated across the area forming the present flood plain this surface comprises a sandy point bar deposit locally overlain by clayey overbank and silty sand crevasse splay deposits an abandoned chute channel infilled with laminated sandy silt and silty clay and an abandoned neck cutoff filled with a sandy cutoff bar and silty clay oxbow lake deposits dating various stream responses to coseismic folding has more tightly constrained the timing of earthquake events in the central nmsz and provides a means of partitioning the deformation amount into individual seismic events three earthquakes have been dated in the reelfoot lake area ca a d 900 1470 and 1812 the latter two earthquakes had large local coseismic deformation both of these events were responsible for numerous stream responses such as shifting depocenters modification of mississippi river channel geometry and derangement of small streams overbank sedimentation ceased on the dome as it was uplifted above the normal flood stage and sedimentation of crevasse splay deposits from the mississippi river colluvium from the scarp and lacustrine sediment accumulated in the adjacent reelfoot basin the much larger mississippi river channel responded to uplift by increasing its sinuosity across the uplift relative to both upstream and downstream increasing its width depth ratio across and downstream of the uplift and decreasing the width depth ratio upstream of the uplift despite the size of the mississippi river it has not yet attained equilibrium since the latest uplift 190 years ago small channels that could not downcut through the uplift were filled locally reversed flow direction or formed a lake where they were dammed uplift and stream response to folding along the tiptonville dome is less dramatic between 2 3 and 0 53 ka during this interval abandoned channel fill and overbank deposition across the dome suggests that it was not a high relief feature one earthquake event occurred during this interval ca a d 900 but coseismic stream response was probably limited to a slight aggradation of a small flood plain stream