seismicity rate change before the irpinia m 6 9 1980 earthquake the stability of seismicity rate in central and southern italy was examined in two data sets from 1975 0 to 1995 0 with m 3 4 and from 1987 5 to 1996 0 with m 2 5 these are the approximate minimum magnitudes of complete reporting for the respective periods the first set was used to evaluate the possibility that the 23 november 1980 irpinia m 6 9 earthquake was preceded by precursory seismic quiescence the second was used to evaluate the conditions under which a current seismic quiescence could be detected in central or southern italy during the years before the irpinia earthquake the seismicity rate in the northern half of the rupture area and north of it was low whether this was a case of precursory quiescence or not is subject to interpretation because the background rate cannot be established for the years before 1975 if we accept the relatively constant seismicity rate in the irpinia volume during the decade after the mainshock as representative for the background rate we have a clear case of precursory quiescence lasting at least 1 3 yr up to the mainshock alternatively it can be postulated that the seismicity rate during the decade following this shock was elevated regionally because of the stress redistribution and that the low rates seen before it represent the normal background rate even if this reasoning is accepted the fact remains that a volume including the northern part of the rupture produced no m 3 4 earthquakes during 1 3 yr before the irpinia earthquake but produced 10 earthquakes during the 4 7 previous yr given these facts we favor the interpretation that the irpinia 1980 earthquake was preceded by precursory seismic quiescence in the entire data set there are three other cases of quiescence of higher significance without a mainshock following since no other mainshock with m 6 exists in the data set no missed event exists we propose that in italy precursory seismic quiescence may precede mainshocks and that it may be detected in the future by the improved catalog of the modern data set beginning in 1987 5 major magnitude scale changes give the mistaken appearance that fewer large magnitude earthquakes occur in italy now than in years before 1987 we postulate that the rate of earthquakes has not changed and that the magnitude scale should be adjusted

uranium series ages of travertines and timing of the last glaciation in the northern yellowstone area wyoming montana uranium series age determinations by mass spectrometric methods were done for travertines and associated carbonate veins related to clastic deposits of the last glaciation pinedale in the northern yellowstone area dramatic variations in the hydrologic head are inferred from variations in the elevation of travertine deposition with time and are consistent with the expected hydrologic effects of glaciation we determine the following chronology of the pinedale glaciation with the key assumption that travertine deposits and associated carbonate veins perched high above present thermal springs were deposited when glaciers filled the valley below these perched deposits 1 the early pinedale outlet glacier advanced well downvalley between 47 000 and 34 000 yr b p 2 the outlet glacier receded to an interstadial position between 34 000 and 30 000 yr b p 3 an extensive pinedale ice advance occurred between 30 000 and 22 500 yr b p 4 a major recession occurred between 22 500 and 19 500 yr b p 5 a minor readvance deckard flats culminated after 19 500 yr b p and 6 recession from the deckard flats position was completed before 15 500 yr b p this chronology is consistent with the general trend of climatic changes in the northern hemisphere as revealed by recent high resolution ice core records from the greenland ice sheet

simulation of historic glacier variations with a simple climate glacier model glacier variations during the last few centuries have shown a marked coherence over the globe characteristic features are the maximum stand somewhere in the middle of the nineteenth century and the steady retreat afterwards with some minor interrruptions depending on the particular region in many papers qualitative statements have been made about the causes of these fluctuations lower temperatures associated with solar variability and or volcanic activity are the most popular explanations in particular the statistical relation between glacier activity and major volcanic eruptions appears to be strong in this paper an attempt is made to simulate recent glacier fluctations with a physics based model a simple climate model calculating perturbations of surface radiation balance and air temperature not necessarily in phase is coupled to a schematic time dependent glacier model the climate model is forced by volcanic activity greenland acidity and or lamb s dust veil index and greenhouse warming solar variability was not considered because its effect on climate has still not been demonstrated in a convincing way the output is translated into variations in equilibrium line altitude driving the glacier model the simulated variations in glacier length show good agreement with the observed record but the amplitude is too small this is improved when mass balance gradients are assumed to be larger in warmer climates compared to recently published modelling studies of particular glaciers in which series of local parameters e g tree ring width and temperature were used as forcing the present simulation is better this suggests that the radiation balance is a decisive factor with regard to glacier variations on longer time scales the model experiments lend support to the results of porter 1986 who concluded from a more qualitative study that a strong relation exists between periods of increased volcanic activity and glacier advances a comparison of some selected runs shows that according to the present model the greenhouse warming would be responsible for about 50 of the glacier retreat observed over the last 100 years

marine isotope stage 3 paleotemperature inferred from reconstructing the die shan ice cap northeastern tibetan plateau glacial extent mapping and dating indicate that the local last glacial maximum llgm of the northeastern tibetan plateau occurred during mid marine isotope stage mis 3 this is asynchronous with the global last glacial maximum lgm that occurred during mis 2 the causes underlying this asynchronicity are the subject of ongoing debate and paleoclimatic reconstructions are a key to advancing understanding of the climatic influence on the spatial and temporal patterns of paleoglaciation we used multiple methods to reconstruct the equilibrium line altitude ela of the die shan paleo ice cap on the northeastern tibetan plateau and to infer past temperature for ice maximum positions believed to be mid mis 3 in age based on regional correlation geomorphic ela reconstructions combined with an energy and mass balance model yield a paleo ela of 4117 31 m asl 786 m lower than present with temperature depressions of 3 8 to similar to 4 6 degrees c compared to the present this is less than the lgm reconstruction of temperature depression inferred from other climatic proxy records on the tibetan plateau and suggests that the llgm glacial advance was a product of lower temperatures and slightly reduced precipitation compared to present whereas the lgm was a more restricted advance in which much colder conditions were combined with much lower precipitation

1 fβ fluctuations and self similarity in earthquake dynamics observational evidences in southern italy abstract recently it has been determined that many statistical features of earthquakes are scale invariant with universal values for exponents the analysis of scaling laws has led to the development of a wide variety of physical models of seismogenesis involving nonlinear dynamics and it can be used to better characterize the seismicity pattern in this work the presence of scale invariance properties in the seismicity of a selected area of the southern appennine chain is revealed 1 f fluctuations are detected from the analysis of earthquake sequences using the counting statistics and at the spatial scale a self similar structure in the epicentre aggregate is determined by the estimation of its fractal dimension finally correlations between temporal exponent fractal dimension and b value variations are described

last glacial maximum equilibrium line altitudes and paleoclimate northern uinta mountains utah u s a nineteen former valley glaciers were reconstructed for their last glacial maximum lgm extents in the northern uinta mountains utah u s a mean equilibrium line altitudes elas calculated by four methods accumulation area ratio toe headwall altitude ratio lateral moraines and cirque floors range from 3050 to 3300 m a s l modern mean summer temperatures t s at the elas range from 8 7 to 11 2 c while modern winter precipitation p ranges from 354 to 590 mm snow water equivalent swe based on the difference in elevation of mean elas across the range lgm p values must have ranged from 940 to 3040 mm swe assuming the modern summer lapse rate was the same during the lgm a t s depression of 5 5 c is required for these precipitation values to plot in the range of modern ela values the reconstructed increase in p at the western end of the range is 10 times the modern increase reflecting the influence of pluvial lake bonneville assuming ela depression ela resulted from this p increase and a uniform 5 5 c t s decrease the regional lgm ela was approximately 900 m

reporting history of the central aleutians seismograph network and the quiescence preceding the 1986 andreanof island earthquake the earthquake catalog of the central aleutian seismic network casn was searched systematically for significant rate changes in the period from 1976 through 1985 the magnitude signatures for the nine changes were modeled by synthetic signatures by this method six of the rate changes could be identified as artificial based on the criteria that the rate change was confined to small magnitude events and that magnitude shifts were present for each of these changes an artificial cause existed that affected the network within one to two months of the time of change as estimated from the catalog analysis one of these cases was a rate decrease by a factor of 2 associated with a storm that had put out of operation two thirds of the network another change coincided with the introduction of digital data processing the four remaining cases were artificial reporting rate increases due to installation of several new stations or to repair of several stations that had failed the three rate changes that could not be identified unambiguously as artificial or natural on the basis of magnitude signatures were all rate decreases by factors of approximately 2 two of these were clearly due to disasters that had put out of operation more than half of the network the third was the proposed precursory quiescence to the 1986 andreanof island m 7 9 earthquake from this we conclude that without knowledge of the network history many of the artificial reporting rate changes in earthquake catalogs can be identified as artificial and that their onset time can be estimated to within one to two months an earthquake count independent from the adak catalog was obtained from the helicorder records of the station adak for the years 1978 through 1985 for the vicinity of adak island of a total of 1831 events 335 were not in the adak catalog and 981 were located within the 1986 aftershock area the helicorder earthquake count showed a pronounced decrease by about 50 per cent similar in amount to that in the adak catalog however the decrease started in 1980 at a time when in the central subregion covered by the adak catalog only m 2 9 events decreased while the smaller magnitude bands show a maximum decrease in 1982 we conclude that the possibility could not be ruled out that electronics changes contributed to the reporting rate decrease starting in the years 1980 to 1982 however it seems very unlikely that a network that was at its healthiest during the precursor time would be reduced by an improvement in the electronics to a detection level approximately equal to that in two short periods when only one third of the stations were operating therefore the seismic quiescence reported and interpreted as a precursor by kisslinger et al 1985 was most likely a natural phenomenon

precursory seismic quiescence seventeen cases of precursory seismic quiescence to mainshocks with magnitudes fromml 4 7 toms 8 0 are summarized the amount of rate decrease ranges from 45 to 90 the significance of these changes varies between 90 and 99 99 the assumption that the background rate is approximately constant is fulfilled in most crustal volumes studied all quiescence anomalies seem to have abrupt beginnings and the rate during the anomalous period is fairly constant the duration of the precursors ranges from 15 to 75 months and it is not clear what factors determine that time at least three successful predictions have been based on seismic quiescence these cases have shown that mainshocks can be predicted based on quiescence but they have also shown that the interpretation of the data in real time is difficult and nonunique if a false alarm is defined as a period of quiescence with a significance level larger than a precursory quiescence in the same tectonic area then we estimate based on searches in four areas that the false alarm rate may be on the order of 50 failure to predict may be expected in perhaps 50 of mainshocks even in carefully monitored areas quiescence cannot be used as a precursor in tectonic environments with low seismic activity most characteristics of the phenomenon are still poorly defined but data exist which probably permit at least a doubling of the presently available data on case histories

new data for late pleistocene pinedale alpine glaciation from southwestern colorado abstract new cosmogenic surface exposure ages of moraine crest boulders from southwestern colorado are compared with published surface exposure ages of boulders from moraine complexes in north central colorado and in west central fremont lake basin wyoming 10be data sets from the three areas were scaled to a single 10be production rate of 5 4 at g yr at sea level and high latitude slhl which represents the average 10be production rate for two high altitude mid latitude sites in the western united states us and austria multiple nuclide ages on single boulders indicate that this 10be production rate yields ages comparable to those calculated with a commonly used 36cl production scheme the average age and age range of moraine crest boulders on terminal moraines at the southwestern colorado and wyoming sites are similar indicating a retreat from their positions 16 8 36cl ka cosmogenic ages in this paper are labeled 10be or 36cl ka or just ka when both 10be or 36cl ages are being discussed radiocarbon ages are labeled 14c ka calibrated radiocarbon are labeled cal ka and calendar ages are labeled calendar ka errors 1 associated with ages are shown in tables radiocarbon ages were calibrated using the data of hughen et al science 303 2004 202 this suggests a near synchronous retreat of pinedale glaciers across a 470 km latitudinal range in the middle and southern rocky mountains hypothetical corrections for snow shielding and rock surface erosion shifts the time of retreat to between 17 2 and 17 5 10be ka at pinedale wyoming and between 16 3 and 17 3 36cl ka at hogback mountain colorado

climatic interpretation of alpine snowline variations on millennial time scales abstract the depression of snowlines or equilibrium line altitudes of alpine glaciers is often used by glacial geologists to infer variations in mass balance the climatic interpretation of snowline depression however is complicated by the number of factors that control glacier mass balance the simple lapse rate method of temperature interpretation ignores the effects of changes in radiation and snow accumulation the statistical approach to temperature interpretation which regresses precipitation and temperature against snowline altitude neglects the effect of radiation the most comprehensive approach for the climatic interpretation of snowline depression couples the heat and mass balances of a glacier surface a sensitivity analysis that utilizes the coupled heat and mass balance approach indicates that the 1000 m variation in snowline of alpine glaciers on glacial to interglacial time scales could be a result of significant changes in temperature and to a lesser extent changes in insolation snowline variations are sensitive only to relatively large changes in annual accumulation which should also be evident in other proxy records of moisture change the approaches outlined here provide glacial geologists with a summary of how various climatic forcings associated with glaciation may be quantified from snowline data

a 2 d numerical model of snow ice energy balance and ice flow for paleoclimatic interpretation of glacial geomorphic features abstract standard methods of interpreting the paleoclimates recorded in alpine glacial geomorphic features rely on estimates of paleoglacier shape commonly assume that relationships between mass balance gradient and equilibrium line altitude of modern glaciers apply equally well to glaciers of in many cases dramatically different climates and do not account for the varying influence of topography on glacial extent while those methods may be adequate for many studies there are an increasing number of areas in which that level of analysis does not match the level of detail of the glacial chronologies being developed as an alternative we present a physically based 2 d glacier model that can be used to determine steady state glacier shapes and distributions for a wide range of climatic conditions the model requires only a modest amount of data beyond that which would be required for simpler methods and includes a relatively accurate representation of the effects of topography on the largest component of the surface energy balance shortwave radiation it calculates 2 d in the horizontal plane distribution of snow accumulation using a surface mass and energy balance approach and calculates the resultant glacier shapes with a 2 d flow model in addition to offering a potentially more accurate reconstruction of paleoclimatic conditions the model provides a means of performing detailed sensitivity analysis establishing relationships between similar deposits in basins of different shape and aspect and of predicting glacier shape terminus position in areas not yet explored

the probable importance of snow and sediment shielding on cosmogenic ages of north central colorado pinedale and pre pinedale moraines abstract eight uncorrected 36 cl ages for pinedale boulders in north central colorado fall in the range 16 5 to 20 9 kyr 10 be age determinations on four of five boulders are in close agreement 6 difference with 36 cl determinations hypothetical corrections for snow shielding increased the 36 cl ages of pinedale boulder surfaces by an average of 12 most ages for pre pinedale bull lake boulders fall within marine isotope stage mis 5 a time when continental and sierran ice accumulations were small or nonexistent under the assumption that these boulders were deposited on moraines that formed before the end of mis 6 140 kyr bp calculations indicated that rock surface erosion rates would have had to range from 5 9 to 10 7 mm kyr 1 to produce the observed 36 cl values when compared to rates that have been documented for the past 20 kyr these erosion rates are extremely high snow shielding accounts for 0 48 of the additional years needed to shift pre pinedale dates to mis 6 this suggests that some combination of snow shielding sediment shielding or 36 cl leakage has greatly decreased the apparent ages of most pre pinedale boulders inability to account for the effects of these processes seriously hinders the use of cosmogenic ages of pre pinedale boulders as estimators of the timing of alpine glaciation

numerical modeling of the snowmass creek paleoglacier colorado and climate in the rocky mountains during the bull lake glaciation mis 6 abstract well preserved moraines from the penultimate or bull lake glaciation of snowmass creek valley in the elk range of colorado usa present an opportunity to examine the character of the high altitude climate in the rocky mountains during marine oxygen isotope stage 6 this study employs a 2 d coupled mass energy balance and flow model to assess the magnitudes of temperature and precipitation change that could have sustained the glacier in mass balance equilibrium at its maximum extent during the bull lake glaciation variable substrate effects on glacier flow and ice thickness make the modeling somewhat more complex than in geologically simpler settings model results indicate that a temperature depression of about 6 7 c compared with the present 1971 2000 ad would have been necessary to sustain the snowmass creek glacier in mass balance equilibrium during the bull lake glaciation assuming no change in precipitation amount or seasonality a 50 increase or decrease from modern precipitation would have been coupled with 5 2 c and 9 1 c bull lake temperature depressions respectively uncertainty in these modeled temperature depressions is about 1 c

mid mis3 climate inferred from reconstructing the dalijia shan ice cap north eastern tibetan plateau the local last glacial maximum lgml on dalijia shan occurred during mid marine isotope stage 3 mis3 which is consistent with some tibetan plateau records but asynchronous with the mis2 global last glacial maximum lgmg paleoclimatic reconstructions are key to advancing understanding such spatial and temporal patterns of paleoglaciation using multiple methods we reconstructed mid mis3 equilibrium line altitude ela on dalijia shan and inferred temperature depressions geomorphic ela reconstructions combined with empirical data on current ela temperature and precipitation yield a mid mis3 ela of 4000 78 m a s l 618 851 m lower than current and a temperature depression of 3 3 6 8 c independent glacial modeling using the degree day approach suggests a mid mis3 ela between 3971 and 4024 m a s l and a temperature depression of 4 2 5 6 c the consistency of these results indicate that mid mis3 temperature depressions in the dalijia shan region were 3 3 6 8 c which is less than the lgmg temperature depression inferred from regional climatic proxy data combined with other proxy data this suggests that the lgml glacial advance in dalijia shan resulted from lower temperatures and slightly reduced precipitation compared with present whereas the lgmg advance was more restricted because much colder conditions were combined with much lower precipitation

paleoclimate simulations for north america over the past 21 000 years features of the simulated climate and comparisons with paleoenvironmental data maps of upper level and surface winds and of surface temperature and precipitation illustrate the results of a sequence of global paleoclimatic simulations spanning the past 21 000 years for north america we review a the large scale features of circulation temperature and precipitation that appear in the simulations from the ncar community climate model version 1 ccm 1 b the implications of the simulated climate for the past continental scale distributions of three plant taxa picea spp pseudotsuga menziesii and artemisia tridentata which are broadly representative of the vegetation across the continent and c the potential explanations in terms of atmospheric circulation or surface energy and water balance processes for mismatches between the simulations and observations most of the broad scale features of previous paleoclimatic simulations with the ncar ccm 0 for north america are present in the current simulations many of the elements of a conceptual model based on previous climate simulations that describes the controls of paleoclimatic variations across north america during the past 21 000 years are found in simulations reviewed here these include 1 displacement of the jet stream by the laurentide ice sheet to the south of its present position in both winter and summer 2 generation of a glacial anticyclone over the ice sheet at the lgm and the consequent induction of large scale sinking motions induced over eastern north america 3 changes in the strength of surface atmospheric circulation features through time including weakening of the aleutian low in winter and strengthening of the eastern pacific and bermuda high pressure systems in summer as the ice sheet decreased in size 4 development of a heat low at the surface and a strengthened ridge in the upper atmosphere over the continent at the time of the maximum summer insolation anomaly 5 increases in summer temperature earlier in regions remote from the ice sheet these increases appear earlier in the present ccm 1 simulations than in the previous ccm 0 ones however and 6 continuation of negative winter temperature anomalies into the middle holocene in general simulated surface conditions that are discordant with paleoenvironmental observations can be attributed to the simulation of particular atmospheric circulation patterns e g those that suppress precipitation or advect warm air into a region with these mismatches amplified in beringia and the southeastern united states by surface energy and water balance processes

inadvertent changes in magnitude reported in earthquake catalogs their evaluation through b value estimates a simple procedure is presented for analyzing magnitudes and seismicity rates reported in earthquake catalogs in order to discriminate between inadvertently introduced changes in magnitude and real seismicity changes we assume that the rate and the frequency magnitude relation of the independent background seismicity do not change with time observed differences in the frequency magnitude relation a and b values between data from two periods are modeled as due to a transformation of the magnitude scale the transformation equation is found by a least squares fitting process based on the seismicity data for earthquakes large enough to be reported completely and by comparing the linear relation of one period to the other for smaller events an additional factor accounting for increased decreased detection is allowed this fitting technique is tested on a data set from parkfield for which two types of magnitudes amplitude and duration were computed for each earthquake we found that the b value fitting technique yielded virtually the same result as a linear regression assuming the same errors in the two magnitudes the technique is also applied to interpret the nature of reporting rate changes in a local guerrero mexico and a regional italy earthquake catalog in guerrero a magnitude change in 1991 37 can be modeled about equally well by m new m old 0 5 or by m new 1 02 m old 0 38 but residuals with the latter transformation are smaller in italy a magnitude change in 1980 21 cannot be modeled satisfactorily by a simple magnitude shift but is well described by a compression of the magnitude scale given by m new 0 67 m old 1 03 the proposed b slope fitting method provides a means to interpret quantitatively and in some cases correct for artificial reporting rate changes in earthquake catalogs

seismic quiescence before the landers m 7 5 and big bear m 6 5 1992 earthquakes the landers earthquake of 28 june 1992 was preceded by a seismicity rate decrease of 75 in a volume approximately 11 by 23 by 15 km located adjacent to and north of the epicenter this anomaly started for all magnitude bands in january 1988 lasting 4 5 yr up to the mainshock a smaller volume 7 by 14 by 15 km to the south of the epicenter showed a seismicity rate decrease of 75 starting in november 1989 the big bear earthquake of the same day was preceded by a 100 decrease of the seismicity rate within a volume of approximately 13 by 22 by 15 km around the hypocenter this volume contained 192 earthquakes of m 1 6 during the background period of 9 yr but none during the 1 6 yr from december 1990 to 27 june 1992 the standard deviate z values characterizing these rate changes are very high 6 3 and 12 3 respectively and the anomalies are unique not surpassed in significance by any other rate decrease in portion of the southern california earthquake catalog examined 117 06 w to 115 40 w and 33 45 n to 35 10 n no seismicity rate change was found in the vicinity of the m 6 1 joshua tree earthquake of 23 april 1992 based on magnitude signatures and frequency magnitude analyses we conclude that the two quiescence anomalies could not have been due to a shift or a compression of the magnitude scale and we interpret them as precursor anomalies this analysis was carried out using the declustered earthquake catalog for the landers area with corrections of 0 2 and 0 1 august 1985 and may 1990 for two suspected magnitude shifts with a new visualization technique we can investigate the stability and changes of the seismicity rate as a function of time and space by mapping z values for rate changes at every time interval and in volumes centered on a dense grid of points latitude longitude this computer code furnishes an almost continuous sequence of smooth contour maps of the degree of rate changes any anomalies artificial or real may thus be defined accurately

coda q in the kachchh basin western india using aftershocks of the bhuj earthquake of january 26 2001 q c estimates of kachchh basin in western india have been obtained in a high frequency range from 1 5 to 24 0 hz using the aftershock data of bhuj earthquake of january 26 2001 recorded within an epicentral distance of 80 km the decay of coda waves of 30 sec window from 186 seismograms has been analysed in four lapse time windows adopting the single backscattering model the study shows that q c is a function of frequency and increases as frequency increases the frequency dependent q c relations obtained for four lapse time windows are q c 82 f1 17 20 50 sec q c 106 f1 11 30 60 sec q c 126f1 03 40 70 sec and q c 122f1 02 50 80 sec these empirical relations represent the average attenuation properties of a zone covering the surface area of about 11 000 20 000 28 000 and 38 000 square km and a depth extent of about 60 80 95 110 km respectively with increasing window length the degree of frequency dependence n decreases marginally from 1 17 to 1 02 whereas q0 increases significantly from 82 to 122 at lower frequencies up to 6 hz q c 1 of kachchh basin is in agreement with other regions of the world whereas at higher frequencies from 12 to 24 hz it is found to be low

a non stationary epidemic type aftershock sequence model for seismicity prior to the december 26 2004 m 9 1 sumatra andaman islands mega earthquake 1 we study temporal changes in seismicity in sumatra andaman islands region before the m 9 1 earthquake of december 26 2004 we applied the epidemic type aftershock sequence etas models to the seismicity the two stage non stationary etas model with a single change point provides a better statistical fit to the seismicity data than the stationary etas model throughout the whole period we made further change point analysis of data sets by dividing into two sub regions the best fitted models suggest that the seismic activation relative to the etas rates started in the middle of july 2000 about 4 5 years before the m 9 1 earthquake this includes an increase in the background seismicity rates particularly in the southern part of the seismogenic zone near the epicenter a space time etas model also suggests that the background seismicity throughout the entire sumatra andaman islands area had increased after the change point time

variable responses of western u s glaciers during the last deglaciation cosmogenic 10 be exposure ages from moraines in the wallowa mountains oregon identify two maximal late pleistocene glaciations at 21 1 6 0 4 ka and 17 0 6 0 3 ka and a minor glacial event at 10 2 6 0 6 ka our new high resolution chronology integrated with other well dated glacial records from the western united states demonstrates sub stantial differences in the synoptic responses of western u s glaciers to climate forcing associated with the global last glacial maximum and subsequent millennial scale events originating in the north atlantic region these variable synoptic glacier responses identify large changes in the relative contributions of regional to global controls on the climate of the western united states that accompanied the deglaciation

cosmogenic 3he and 10be chronologies of the late pinedale northern yellowstone ice cap montana usa cosmogenic 3 he and 10 be ages measured on surface boulders from the moraine sequence deposited by the northern outlet glacier of the yellowstone ice cap indicate that the outlet glacier reached its terminal position at 16 5 6 0 4 3 he ka and 16 2 6 0 3 10 be ka respectively concordance of these ages supports the scaled production rates used for 3 he 118 6 6 6 6 atoms g 21 y r 21 and 10 be 5 1 6 0 3 atoms g 21 y r 21 62s at high latitudes at sea level two recessional moraines upvalley from the terminal moraine have mean ages of 15 7 6 0 5 10 be ka and 14 0 6 0 4 10 be ka respectively and a late glacial flood bar was deposited at 13 7 6 0 5 10 be ka these cosmogenic chronologies identify a late pinedale glacial maximum in northern yellowstone that is significantly younger than previously thought and they suggest deglaciation of the yellowstone plateau by 14 10 be ka

cosmogenic exposure age chronologies of pinedale and bull lake glaciations in greater yellowstone and the teton range usa abstract we have obtained 69 new cosmogenic 10be surface exposure ages from boulders on moraines deposited by glaciers of the greater yellowstone glacial system and teton range during the middle and late pleistocene these new data combined with 43 previously obtained 3he and 10be ages from deposits of the northern yellowstone outlet glacier establish a high resolution chronology for the yellowstone teton mountain glacier complexes boulders deposited at the southern limit of the penultimate ice advance of the yellowstone glacial system yield a mean age of 136 13 10be ka and oldest ages of 151 157 10be ka these ages support a correlation with the bull lake of west yellowstone with the type bull lake of the wind river range and with marine isotope stage mis 6 end moraines marking the maximum pinedale positions of outlet glaciers around the periphery of the yellowstone glacial system range in age from 18 8 0 9 to 16 5 1 4 10be ka and possibly as young as 14 6 0 7 10be ka suggesting differences in response times of the various ice cap source regions moreover all dated pinedale terminal moraines in the greater yellowstone glacial system post date the pinedale maximum in the wind river range by 4 6 kyr indicating a significant phase relationship between glacial maxima in these adjacent ranges boulders on the outermost set and an inner set of pinedale end moraines enclosing jenny lake on the eastern teton front yield mean ages of 14 6 0 7 and 13 5 1 1 10be ka respectively the outer jenny lake moraines are partially buried by outwash from ice on the yellowstone plateau hence their age indicates a major standstill of an expanded valley glacier in the teton range prior to the younger dryas followed closely by deglaciation of the yellowstone plateau these new glacial chronologies are indicative of spatially variable regional climate forcing and temporally complex patterns of glacier responses in this region of the rocky mountains during the pleistocene

last glacial maximum climate inferences from cosmogenic dating and glacier modeling of the western uinta ice field uinta mountains utah abstract during the last glacial maximum lgm the western uinta mountains of northeastern utah were occupied by the western uinta ice field cosmogenic 10 be surface exposure ages from the terminal moraine in the north fork provo valley and paired 26 al and 10 be ages from striated bedrock at bald mountain pass set limits on the timing of the local lgm moraine boulder ages suggest that ice reached its maximum extent by 17 4 0 5 ka 2 10 be and 26 al measurements on striated bedrock from bald mountain pass situated near the former center of the ice field yield a mean 26 al 10 be ratio of 5 7 0 8 and a mean exposure age of 14 0 0 5 ka which places a minimum limiting age on when the ice field melted completely we also applied a mass energy balance and ice flow model to investigate the lgm climate of the western uinta mountains results suggest that temperatures were likely 5 to 7 c cooler than present and precipitation was 2 to 3 5 times greater than modern and the western most glaciers in the range generally received more precipitation when expanding to their maximum extent than glaciers farther east this scenario is consistent with the hypothesis that precipitation in the western uintas was enhanced by pluvial lake bonneville during the last glaciation

climate during the last glacial maximum in the wasatch and southern uinta mountains inferred from glacier modeling abstract recent improvements in understanding glacial extents and chronologies in the wasatch and uinta mountains and other mountain ranges in the western u s call for a more detailed approach to using glacier reconstructions to infer paleoclimates than commonly applied aar ela at methods a coupled 2 d mass balance and ice flow numerical modeling approach developed by plummer m a phillips f m 2003 a 2 d numerical model of snow ice energy balance and ice flow for paleoclimatic interpretation of glacial geomorphic features quaternary science reviews 22 1389 1406 allows exploration of the combined effects of temperature precipitation shortwave radiation and many secondary parameters on past ice extents in alpine settings we apply this approach to the little cottonwood canyon in the wasatch mountains and the lake fork and yellowstone canyons in the south central uinta mountains results of modeling experiments indicate that the little cottonwood glacier required more precipitation during the local last glacial maximum lgm than glaciers in the uinta mountains assuming lapse rates were similar to modern model results suggest that if temperatures in the wasatch mountains and uinta mountains were 6 c to 7 c colder than modern corresponding precipitation changes were 3 to 2 modern in little cottonwood canyon and 2 to 1 modern in lake fork and yellowstone canyons greater amounts of precipitation in the little cottonwood canyon likely reflect moisture derived from the surface of lake bonneville and the lake may have also affected the mass balance of glaciers in the uinta mountains

seismic quiescence before the m 7 1988 spitak earthquake armenia a detailed analysis of the 35 yr of seismicity between 1962 and 1997 using a gridding technique shows that the m7 spitak earthquake of 1988 december 7 was preceded by a quiescence anomaly that started at approximately 1984 0 5 and lasted about 5 0 5 yr up to the main shock this quiescence anomaly had a radius of about 20 3 km estimated from circular areas with 75 per cent rate decrease centred at the point of maximum significance of the anomaly the quiescence was clearly present in the aftershock volume during the 5 yr before the 1988 main shock but its statistically strongest expression was located 30 km nw of the epicentre this anomaly fulfills the association rules between precursory quiescence anomalies and main shocks even for a tight definition and is therefore proposed as a case of precursory quiescence the largest value of the standard deviate z found by random selection of samples by gridding was z 14 for a time window of tw 3 yr using a sample size of n 300 events this makes this anomaly the strongest observed so far and it is the first documented in an environment of continental collision there are no false alarms exceeding in significance the precursor the armenian earthquake catalogue used for this study had 4600 earthquakes with m mmin 2 2 in the area bounded by 39 5 to 42 n 42 5 to 47 e from the point of view of homogeneous reporting this is the best catalogue we have analysed so far the limits of the data used and the density of the grid are dictated by the data and have no influence on the results the choice of free parameters does not influence the results significantly within the following limits 100 n 500 2 tw 7 2 2 mmin 2 8

a seismic quiescence before the 2017 mw 7 3 sarpol zahab iran earthquake detection and analysis by improved rtl method abstract a major earthquake with magnitude mw 7 3 struck sarpol zahab kermanshah province iran on november 12 2017 causing extended damage and casualties the epicenter was located in the northwestern part of the zagros mountain range an active belt originated by the arabia eurasia collision we explore seismicity preceding this earthquake by using the iranian seismological center instrumental earthquake catalog igtu with the aim to identify possible anomalies in background seismicity that can be related with this and other future large events for this purpose we used a method for intermediate term forecasts of large earthquakes namely the region time length rtl algorithm which analyzes declustered catalogs and is sensitive to quiescences that may precede major earthquakes rtl has been progressively refined and has been applied in several regions worldwide during the last decades to decluster the earthquake catalog we used a quite novel approach based on the nearest neigbour distances between events in the space time energy domain a method that preserves the background seismicity while removing the clustered component the retrospective application of rtl algorithm to the area surrounding the mainshock epicenter highlights two significant quiescences one preceding the sarpol zahab mw 7 3 earthquake and the other occurring before a mw 5 7 earthquake which struck the same region on november 2013 the quiescences duration ranges from few months to one year and is compatible with earlier results from different regions of the world in addition we applied an enhanced variant of rtl algorithm which allows us drawing maps for the whole study region and that shows only quiescences consistently detected for different choices of the free parameters and hence more stable the resulting map for northwestern iran calculated for the time span 1 june 2017 11 november 2017 evidences two broad quiescence regions oriented nw se along the zagros belt one located to the north evidences a significant seismic anomaly corresponding to the sarpol zahab earthquake which disappeares immediately after the event the second one located in the southeastern part of the study region persists up to the end of the available catalog october 4 2018

precise cosmogenic 10be measurements in western north america support for a global younger dryas cooling event the inner titcomb lakes moraine in the wind river mountains wyoming has been dated with a precision of 5 using accelerator mass spectrometric measurements of cosmogenic 10be in surface samples from nine boulders resting on its crest the age of this moraine is 11 4 0 5 to 13 8 0 6 ka the range in age is due to the uncertainty in the 10be production rate and uncertainties in rock erosion rate and shielding of cosmic rays by snow additional exposure ages on bedrock and boulder surfaces that are stratigraphically younger and older than the inner titcomb lakes moraine conform with this age the exposure ages of the inner titcomb lakes moraine overlap the north atlantic younger dryas event 12 8 0 2 to 11 5 0 3 ka

latest pleistocene alpine glacier advances in the sawtooth mountains idaho usa reflections of midlatitude moisture transport at the close of the last glaciation mountain glaciers in the sawtooth mountains responded strongly to reinvigorated atmospheric moisture transport following the last ice sheet maximum the glaciers constructed an extensive moraine belt in the southeastern sawtooth mountains allowing determination of a detailed radiocarbon chronology from lake and marsh cores moraine morphometry and soil data indicate construction of seven to nine moraines in each of four valleys during two main late pleistocene ice advances a basal radiocarbon date from marsh cores in the alturas valley documents that the maximum advance during marine oxygen isotope stage 2 occurred shortly before ca 16 900 calibrated cal yr b p minimum limiting dates on glacial lacustrine sediment in lake and marsh cores from three valleys clustered around 13 950 cal yr b p document the maintenance or reestablishment of extensive ice volume during early late glacial time the ca 16 900 cal yr b p advance postdates the last ice sheet maximum by 4000 yr and is broadly correlative with maximum advances of the north yellowstone outlet glacier and the puget lobe of the cordilleran ice sheet and a near maximum advance of wallowa mountain glaciers these synchronous advances indicate response of a variety of ice systems to reinvigorated moisture transport following the ice sheet maximum as does the subsequent sawtooth advance during early late glacial time together these responses indicate strong sensitivity of certain ice systems to moisture delivery fluctuations

amino acid paleothermometry of quaternary ostracodes from the bonneville basin utah abstract unlike many other proxy climate recorders temperature dependent chemical reactions that take place in fossils are independent of paleoprecipitation changes and therefore allow paleotemperatures to be calculated uniquely in this study i use the extent of amino acid racemization in fossil ostracode shells to reconstruct the temperature history of the bonneville basin utah the enantiomeric composition d l ratios of 64 ostracode samples each comprising an average of 18 subsamples from 25 sites were analyzed by reverse phase hplc the effective diagenetic temperature edt for five intervals of the quaternary including the last full glacial period was calculated for two amino acids aspartic and glutamic acids errors associated with the edt calculations were derived using a monte carlo procedure age control was provided by both new and previously published ams 14 c luminescence tephra and amino acid geochronology the edt for the southern bonneville basin during the middle pleistocene interval from 620 150 ka oxygen isotope stages ois 16 6 was 5 7 1 5 c this compares with an edt of 10 9 1 3 c for the late holocene last 5 8 cal ka and a current mean annual temperature of about 9 4 c at nearby sites 40 n latitude the edt then decreased to 3 3 1 3 c for the interval from ois 6 2 150 12 cal ka during the last full glacial period 24 12 cal ka ois 2 the edt was 1 1 2 5 c or about 10 3 c lower than during the late holocene paleotemperatures this low suggest that reduced evaporation rather than increased precipitation could have accounted for the increased effective moisture and the growth of lake bonneville

mapping seismic quiescence in california the decrease of microearthquake activity is a controversial possible precursor for mainshock prediction the calculation of seismic quiescence is a convenient tool to quantify this decrease however the actual size of an anomaly significantly depends on the calculation parameters the necessary averaging over space and time acts as 3d lowpass filter the sliding statistics windows introduce highpass behavior and the magnitude threshold shall ensure catalog completeness but also biases the data selection to argue on any claimed anomaly the only conclusive solution would be an exhaustive search over all parameters over an area significantly larger than just the epicenter region and against a test of the null hypothesis qmap is a new mapping approach to process full catalogs that is some twenty years of data for areas of one million km 2 with one fixed set of parameters it utilizes fractil statistics to avoid errors otherwise induced by clusters of aftershock series qmap features two different scaling modes one to display absolute decrease and a second for weighted anomalies by erosion filtering applied to california one can recognize quiescence anomalies of regional scale prior to the coalinga and loma prieta earthquakes but there are more and greater anomalies distributed all along the san andreas fault system without further criteria to understand these patterns the additional anomalies degrade seismic quiescence to an observation with high false alarm rate for earthquake prediction

late pleistocene glacial equilibrium line altitudes in the colorado front range a comparison of methods abstract six methods for approximating late pleistocene pinedale equilibrium line altitudes elas are compared for rapidity of data collection and error rmse from first order trend surfaces using the colorado front range trend surfaces computed from rapidly applied techniques such as glaciation threshold median altitude of small reconstructed glaciers and altitude of lowest cirque floors have relatively high rmses 97 186 m because they are subjectively derived and are based on small glaciers sensitive to microclimatic variability surfaces computed for accumulation area ratios aars and toe to headwall altitude ratios thars of large reconstructed glaciers show that an aar of 0 65 and a thar of 0 40 have the lowest rmses about 80 m and provide the same mean ela estimate about 3160 m as that of the more subjectively derived maximum altitudes of pinedale lateral moraines rmse 149 m second order trend surfaces demonstrate low elas in the latitudinal center of the front range perhaps due to higher winter accumulation there the mountains do not presently reach the ela for large glaciers and small front range cirque glaciers are not comparable to small glaciers existing during pinedale time therefore pleistocene ela depression and consequent temperature depression cannot reliably be ascertained from the calculated ela surfaces

beryllium 10 dating of the duration and retreat of the last pinedale glacial sequence accurate terrestrial glacial chronologies are needed for comparison with the marine record to establish the dynamics of global climate change during transitions from glacial to interglacial regimes cosmogenic beryllium 10 measurements in the wind river range indicate that the last glacial maximum marine oxygen isotope stage 2 was achieved there by 21 700 700 beryllium 10 years and lasted 5900 years ages of a sequence of recessional moraines and striated bedrock surfaces show that the initial deglaciation was rapid and that the entire glacial system retreated 33 kilometers to the cirque basin by 12 100 500 beryllium 10 years

steering of westerly storms over western north america at the last glacial maximum the last glacial maximum hydroclimate over western north america differed from the modern climate a proxy model comparison suggests that the glacial storm track was squeezed and steered by atmospheric high pressure systems

last glacial maximum climate based on cosmogenic 10be exposure ages and glacier modeling for the head of tashkurgan valley northwest tibetan plateau abstract fully understanding the timing and climate of last glacial maximum lgm is still lack in the head of the tashkurgan valley northwest tibetan plateau tp the recent improvements in cosmogenic 10 be exposure dating and glacier modeling present an opportunity to estimate the lgm climatic conditions in the paper we investigated the moraines and used the 10 be exposure dating on the moraine boulders to constrain the timing of the lgm the kuzigun glacial stage in the head of the tashkurgan valley then we used a coupled mass balance and ice flow model to quantify the paleoclimate from past glacier extents constrained by mapped and dated kuzigun glacial moraines in the area we showed that the glaciers terminated at an elevation of 4100 4200 m asl during the kuzigun glacial stage and the glacial stage occurred during or slightly before 15 23 ka corresponding to the timing of the global lgm the modeled mass balances indicated that present day equilibrium line altitude ela ranges from 5150 to 5250 m asl and lgm ela is between 4550 and 4600 m asl in the area suggesting an ela lowering of 600 m during the lgm model results suggested that the temperature during the lgm in the head of the tashkurgan valley is 5 8 c colder than today considering a 30 70 reduction in precipitation compared to today the paleoclimate estimates are generally consistence with previous studies that showed the lgm climate was colder and drier than today on the tp

two current seismic quiescences within 40 km of tokyo summary two highly significant seismic quiescence anomalies that started in 1993 0 exist currently within about 40 km of tokyo they are located in central saitama province at 35 99 n 139 56 e and in tokyo bay south of funabashi at 35 59 n l39 94 e the radii of the anomalous volumes are approximately 15 km centred at about 25 and 20 km depth respectively the seismicity rate during the quiescence was less than 10 per cent background rate in both cases the significance of these quiescences measured by the standard deviate z test comparing the rate of the last three years to the backgound rate is higher than for any other rate changes present in the catalogue zmax 7 5 and 7 2 respectively however episodes of highly significant quiescences which could have been interpreted as precursors but were not followed by main shocks also exist in the data set a third seismic quiescence was found to be in progress since 1993 3 0 5 in nw saitama province at 36 18 n 139 22 e it has a radius of 14 km and is less significant than the other two anomalies zmax 6 8 in a polygon that covers the areas of all three quiescences defined above the seismicity rate since 1994 is only 30 per cent of the previous background rate i e 100 earthquakes that would normally have occurred did not this analysis is based on the earthquake catalogue of the national institute for earth science and disaster prevention for the years 1980 1996 2 and mmin 1 0 as well as for the years 1986 2 1996 2 with mmin 0 1 the anomalies are equally clear in the clustered and in the full catalogues to avoid contamination by explosions only nighttime data 19 00 to 7 00 hours local time were used the frequency magnitude distributions in the quiescent volumes at central saitama nw saitama and funabashi have b values of 1 3 1 5 and 1 1 respectively based on the hypothesis that crustal volumes with high b values may not be capable of m6 earthquakes these three quiescent volumes may be ruled out as source volumes for main shocks of these magnitudes using lilt seismic quiescence hypothesis alone it is a reasonable interpretation to suggest that m 6 5 0 5 earthquakes are expected to terminate each of the three quiescences within 1 year 1 year from now with a 50 per cent probability each the interpretation that all three quiet volumes could rupture together in a large earthquake seems less likely however based on the information that the quiescences are located in volumes with b values above the average b 0 8 it can be argued that the three current quiescences are false alarms the fact that these two lines of evidence allow opposing interpretations in these cases shows that neither hypothesis is sufficiently tested thus the quiescence hypothesis is not advanced enough for issuing earthquake predictions nevertheless it is important that scientific tests of prediction scenarios are formulated in real time so we can learn how to modify our hypotheses to make them useful for prediction in the future

quantitative mapping of a precursory seismic quiescence to the izu oshima 1990 m6 5 earthquake japan a highly significant seismic quiescence with a standard deviate z 10 1 corresponding to a 99 per cent confidence level lasted from 1987 7 up to the 1990 february 20 izu oshima m 6 5 earthquake the quiescent volume had dimensions of 30 km n s and 10 km e w and was centred below 14 km depth within the recently upgraded seismograph network of the earthquake research institute eri this main shock was the only one with a magnitude m 5 8 in the upper 30 km of the crust for which the precursory quiescence hypothesis could be tested within a radius of 50 km and during the observation period 1983 5 1995 9 there were no other 1 5 yr or longer periods of quiescence that were rated z 6 5 in the declustered earthquake catalogue except one that was associated with volcanic activity the total space time covered by alarms including the volcanic one was less than 1 per cent at the z 6 5 level the rarity of highly significant episodes of quiescence and the correlation in space and time suggest that a precursory seismic quiescence started 2 5 yr before the izu oshima 1990 earthquake in its source volume and to the north of it and that it can be recognized with an alarm level of z 6 0 generating no false alarms during the 1 5 yr quiescence window only 10 earthquakes occurred in the quiet volume whereas 50 events were expected based on the rate seen at other times in randomly selected volumes containing 50 100 and 200 events the anomaly scored z 6 1 to 10 1 on the basis of the data from may 1983 to 1995 there is no highly significant quiescence currently present in the izu oshima area

an analysis of the process of acceleration of seismic energy emission in laboratory experiments on destruction of rocks and before strong earthquakes on kamchatka and in italy abstract the time to failure model is a technique in which a failure function is fitted to a time series of accumulated benioff strain before a large earthquake we analyze the relation of the time to failure model to the hypothesis of fractal structure of seismicity a power law failure function varnes 1989 bufe and varnes 1993 and its log periodic generalization sornette and sammis 1995 are discussed the results of application of the log periodic time to failure model to the analysis of the process of acceleration of seismic energy emission in the laboratory experiments on rock destruction and before strong earthquakes on kamchatka and in italy are presented

second order moment of central california seismicity 1969 1982 the second order moment cross correlation function of earthquakes in the u s geological survey central california catalog between 1969 and 1982 was calculated with respect to a magnitude threshold m 4 0 over interevent distances up to 80 km and interevent times up to 320 days the statistical procedure results in a representation of the spatial temporal structure of the catalog associated with m 4 0 earthquakes and is capable of revealing patterns too weak to be detected in the space time distribution of seismicity for individual earthquake sequences a method is introduced for identifying aftershocks based on a physical two parameter model of the earthquake interaction process the results show that the aftershock process dominates the second order moment and may even obscure the statistical expression of a precursory process a concentration of foreshocks within 15 km and 3 days of m 4 0 main shocks exhibits an apparent migration toward the main shock loci with velocity 2 6 5 3 km d this concentration may be related to an observed tendency for m 4 0 events to cluster auto correlate over this interevent range with the identified aftershocks removed the residual catalog is poissonion in space and time when two m 4 0 earthquakes occur within 80 km and 40 days of each other aftershock productivity appears to be relatively enhanced in the earlier sequence this suggests that aftershock populations are not solely dependent on their main shocks and that unusually productive aftershock sequences may be predictors of future moderate earthquakes

climates during late quaternary glacier advances glacier climate modeling in the yingpu valley eastern tibetan plateau abstract the last glacial maximum lgm featured a major cooling of earth s climate after which the climate evolved in the largest reconfiguration of the past 100 ka despite its significance full understanding of the climate history during and since the lgm is still lacking on the eastern tibetan plateau recent improvements in understanding glacial extents and chronologies in the yingpu valley eastern tibetan plateau present an opportunity to estimate the glacial climatic conditions during and since the lgm using a relatively new glacier climate model this study reconstructs glacier advances in the yingpu valley and quantifies the related climate conditions during the lgm lateglacial and late holocene glacial stages the model results show that the yingpu valley contained ice volumes of 1 65 km3 1 03 km3 and 0 29 km3 with equilibrium line altitude ela lowering values of 500 m 410 m and 150 m in the three successive glacial stages respectively by examining other independent paleoclimatic reconstructions it is concluded that the temperature decreased by 4 0 5 9 c 3 4 3 7 c 0 3 0 6 c with the precipitation amounts being 40 80 80 100 and 100 110 of modern values during the lgm lateglacial and late holocene glacial stages respectively the climate estimates for the three glacial stages are generally in agreement with other climatic proxy records on the tibetan plateau and atmospheric circulation modeling results

lake bonneville fluctuations and global climate change lake bonneville the largest late pleistocene closed basin lake in the north american great basin fluctuated widely in response to changes in climate the geochemistry and mineralogy of endogenic calcium carbonate deposited in deep water and stratigraphic studies of shore zone deposits provide evidence of millennial scale lake level fluctuations that had amplitudes of about 50 m between 30 and 10 ka falling lake events occurred at 21 18 5 19 17 5 16 15 5 14 13 and 10 ka radiocarbon years synchronously with the terminations of heinrich events h1 and h2 and other smaller scale iceberg rafting events a b c and younger dryas in the north atlantic ocean the lake bonneville results thus support other climate records that suggest that late pleistocene millennial scale climate change was global in extent the size and shape of the northern hemisphere ice sheets which determined the mean positions of storm tracks may have been the primary control on late pleistocene water budgets of great basin lakes

seismicity rate variations and systematic changes in magnitudes in teleseismic catalogs abstract seismicity rate variations are commonplace in teleseismic catalogs these changes have two possible causes they could be real or they could be related to changes in the networks used to detect the events it is clearly important to differentiate between these two possibilities we demonstrate a technique for making this differentiation using uniform data generated with known rates and magnitude shifts we then apply this technique to data from large regions of the world all of these regions show significant variations in seismicity rates for sets with magnitude cutoffs of 5 0 and 5 5 we show that most of these changes have distributions in the magnitude domain which are consistent with systematic changes in magnitudes of between 0 1 and 0 2 units these results suggest that most observed rate variations in teleseismic sets with high magnitude cutoffs are related to systematic changes in magnitudes and are therefore not real this result has important implications for earthquake prediction and tectonic studies which interpret these variations

seismic quiescence preceding the 2016 central italy earthquakes abstract a complex multiple mainshocks sequence 24 08 2016 mw 6 0 26 10 2016 mw 5 4 and 5 9 30 10 2016 mw 6 5 occurred in central italy causing the death of nearly 300 people and widespread destruction of entire villages the region time length rtl method is used to analyze the seismicity preceding the first mw 6 0 amatrice mainshock this analysis is performed using the earthquake catalogue maintained by the istituto nazionale di geofisica e vulcanologia ingv after a preprocessing which includes the declustering of aftershocks a well evident quiescence that preceded the sequence was detected the quiescence extended throughout a broad region north of the epicenter the largest event of the sequence and the aftershocks covered most of the quiescence region except for a small area to the west the quiescence started from the beginning of september 2015 and lasted for approximately 1 year up to the amatrice mainshock

teleseismic detection in the aleutian island arc recently it has become apparent that teleseismic detection has decreased substantially in many regions of the world the major decrease was related to the closure of the vela arrays in the united states during the late 1960 s this detection decrease has been recognized in south and central america mexico the kuriles the caribbean tonga and the new hebrides in this paper the effect of the closure of these arrays on the reporting of events in the aleutian island arc is examined in the aleutians the detection history is complicated by the short term installation of a local network on and near amchitka island during the early 1970 s the temporal coincidence of the installation of this network and the closure of the vela arrays delayed the detection decrease in the central aleutians until the amchitka network was closed in early 1973 reporting in the eastern aleutians was unaffected by the installation of the amchitka network in that region the detection decreased between 1968 and 1970 the time of the closure of the vela arrays new techniques have been developed which make it possible to determine the effect of station installation or closure on the reporting in some regions these techniques rely on plots which show the distribution of an observed seismicity rate change in the magnitude domain these plots make it possible to recognize probable detection changes and to determine quantitatively magnitude cutoffs which avoid these changes the magnitude level at which these cutoffs are made is termed the minimum magnitude of homogeneity mmin h the reporting of events with mb 4 6 in the aleutians decreased substantially during the mid 1970 s so mmin h in this region is 4 7 this is different from the magnitude of completeness mmin c which is mb 5 0 0 1 if one is interested in examining seismicity rates for changes which may be precursors to earthquakes then awareness of detection related changes and magnitude cutoffs which avoid these changes are essential for meaningful results

simulation of the historical variations in length of unterer grindelwaldgletscher switzerland the historical length variations in unterer grindelwaldgletscher have been simulated by coupling a numerical mass balance model to a dynamic ice flow model as forcing functions we used partly reconstructed local climatic records which were transformed by the mass balance model into a mass balance history the ice flow model then computes the length variations that have occurred over the course of time in a model run from ad 1530 to the present with both seasonal temperature and precipitation variations as forcing functions the observed maximum length of the glacier around ad 1860 and the subsequent retreat are simulated the observed ad 1600 maximum however does not show up in the simulation this is probably due to an incorrect reconstruction of the mass balance for this period as detailed climatic data are available only since 1865 the root mean square difference between the simulated and the observed front positions is 0 28 km the simulated glacier geometry for 1987 fits the observed geometry for that year reasonably well because of the success of the historical simulation an attempt is made to predict future glacier retreat on the basis of two different greenhouse gas scenarios for a business asusual scenario only 29 of the 1990 volume would remain in ad 2100

a reevaluation of cosmogenic 36cl production rates in terrestrial rocks we have measured 36cl in a suite of 33 rock samples having well constrained exposure histories and ages the 36cl production parameters were estimated by minimizing the squared deviations between the 36cl and independent ages yielding the following production parameters spallation and muon production from ca 2940 200 atoms 36cl mole ca 1 yr 1 spallation from k 6020 400 atoms 36cl mole k 1 yr 1 and neutron production in air 586 40 fast neutrons g air 1 yr 1 the new production constants for spallation on ca and thermal neutron activation are in good agreement with previous results but that for spallation on k is about 50 larger the past decade has seen a rapid growth in the application of terrestrial cosmogenic nuclides produced by cosmic ray particles within rocks at the earth surface nuclear cross sections particularly for reactions initiated by neutrons and muons are not known with sufficient accuracy so production rates for these nuclides must be empirically calibrated using independently dated geological samples direct production estimates for 36cl were first obtained by zreda et al 1991 who measured 36c1 in mineral separates from granitic boulders on moraine crests at chiatovitch creek in the eastern white mountains of california and nevada this data set was the best available at the time but since then several factors have prompted a reevaluation of the 36cl production rates one is that zreda et al 1994 have shown that there can be significant scatter of the cosmogenic ages of individual glacial boulders toward ages younger than that of the moraine due to soil erosion a second factor is that a much wider range of samples is now available for this purpose finally recent theoretical advances in calculating production by thermal neutron absorption liu et al 1994 now permit more realistic calibration of this reaction

26al and10be dating of late pleistocene and holocene fill terraces a record of fluvial deposition and incision colorado front range cosmogenic 26al 10be and 14c dating of fluvial fill terraces in steep canyons of the colorado front range provides a temporal framework for analysing episodic aggradation and incision results from boulder canyon show that terrace heights above the modern channel grade can be divided into 1 bull lake 100 ka 20 15 m above grade 2 pinedale 32 10 ka 15 4 m above grade and 3 holocene age 15 m above grade record bull lake deposition well preserved terraces of pinedale age suggest that the range of terrace height above grade reflects short term fluctuations in the river profile during periods of rapidly changing stream load and power net river incision apparently occurred during transitions to interglacial periods soil development and stratigraphic position along with limited cosmogenic and 14c dating suggest that 130 ka terraces in boulder canyon correlate with the louviers alluvium and that 32 to 10 ka fills in the canyon correlate with the broadway alluvium on the adjacent high plains late pleistocene incision rates 0 15 m ka 1 along boulder canyon exceed pre late pleistocene incision rates and are higher than middle to late pleistocene incision rates 0 04 m ka 1 on the high plains this study provides an example of how modern geochronologic techniques allow us to understand better rivers that drain glaciated catchments copyright 2002 john wiley sons ltd