relationships between dinoflagellate cyst assemblages in surface sediment and hydrographic conditions in the bering and chukchi seas palynological analyses were performed on 52 surface sediment samples from the eastern part of the bering sea and chukchi sea in order to document the regional distribution of dinoflagellate cyst assemblages and their relationship with sea surface conditions the assemblages present a relatively high species diversity 20 taxa are recovered routinely especially in the bering sea where they are dominated by operculodinium centrocarpum and the cyst of pentapharsodinium dalei accompanied mainly by spiniferites elongatus s l spiniferites ramosus impagidinium pallidum brigantedinium spp islandinium minutum selenopemphix quanta selenopemphix nephroides quinquecuspis concreta and the cyst of polykrikos kofoidii the percentages of the main taxa vary with latitude and principal component analysis shows that the distribution of assemblages is closely related to hydrographic conditions notably the seasonal duration of sea ice cover and the sea surface temperature in february the dinoflagellate cyst assemblages from the bering sea differ significantly from those of subarctic seas of the north atlantic with respect to their species composition and relationships with sea surface conditions in particular the occurrence of the cyst of polykrikos kofoidii and quinquecuspis concreta and the positive correlation between the percentages of operculodinium centrocarpum and the extent of sea ice constitute peculiar features in the bering sea assemblages copyright 2001 john wiley sons ltd journal of quaternary science

regionalized primary paleoproduction variability in the sea of okhotsk during late pleistocene and holocene abstract in order to reconstruct the history of primary paleoproductivity changes during the last 160 kyr in the okhotsk sea os the high resolution down core analyses of chlorin content were performed on 11 sediment cores obtained from various part of the studied area with wide ranged depths spatial and temporal distributions of the marine phytoplankton paleoproductivity depend on sea ice condition and nutrient supply the observed discrepancies among the reconstructed records allow us to separate out three main regions with specific environmental conditions during glacial stages the paleoproductivity was depressed and vice versa productivity in the central region is low comparing to other regions due to nutrient limitation increased paleoproductivity in the southeastern area was affected by influence of nutrient rich pacific waters

mixed layer evolution in the sea of okhotsk observed with profiling floats and its relation to sea ice formation 1 the time evolution of the ocean mixed layer in the seasonal sea ice zone of the okhotsk sea has been observed with profiling floats the heat storage rate in the mixed layer estimated from the float data well coincides with the surface heat flux mixed layer deepening and the onset of ice formation can be well reproduced by a bulk mixed layer model suggesting that onset of ice formation can be predicted by local atmospheric conditions this explains the remarkably high correlation of the onset day of sea ice formation with the surface heat loss in the preceding fall the anomalously large heat loss in the fall of 2000 led to the anomalously early ice formation strong stratification due to the amur river fresh water flux is indispensable for ice formation through suppression of deep convection

orbital scale changes of sea ice conditions of sea of okhotsk during the last glaciation and the holocene mis 4 mis 1 abstract in this paper 5 schemes for reconstructing the sea ice conditions in the sea of okhotsk the so during the last 74 kyr are presented these schemes were constructed based on calculations of the ice rafted debris ird fluxes in 16 sediment cores and the available published mineralogical data derkachev et al 2004 we obtained new data on the orbital scale changes of the ird fluxes in the studied area for the last four marine isotopic stages mis as a result the key areas of sea ice formation and general direction of sea ice drift and in turn dominate direction of geostrophic wind in the so were established for each of the investigated miss it allows us to suppose the positions of siberian high and aleutian low during the individual miss at that the sea ice was of predominantly seasonal for studied period except for the northwestern and western parts of sea where perennial sea ice fields were preserved over a period of several years during mis 2 the variations of sea ice conditions attest to a particular type of atmospheric pressure field prevailing over the so during individual miss the secondary sea ice drift directions points out that the predominant atmospheric pressure field during individual miss were inconstant except the mis 2

simulations of chlorofluorocarbons in and around the sea of okhotsk effects of tidal mixing and brine rejection on the ventilation 1 ventilation of waters in and around the sea of okhotsk was investigated using simulations of chlorofluorocarbons cfcs in the northwestern north pacific we used an ocean general circulation model coupled with a sea ice model the model reproduces the distributions of cfcs similar to observed values and indicates the importance of tidal mixing along the kuril islands and brine rejection to ventilation of waters in and around the sea of okhotsk to clarify the role of each process numerical experiments excluding one of the two processes were carried out results show that brine rejection transports cfcs into the intermediate layer as deep as 200 400 m along the path of dense shelf water in the western sea of okhotsk but hardly to other areas and layers on the other hand tidal mixing transports cfcs into the intermediate and deeper layers throughout the sea of okhotsk we conclude that the tidal mixing has a greater influence than brine rejection on the ventilation of layers below the winter mixed layer

wind driven ice drift in a shallow sea the free drift equations are solved for ice floes in a shallow sea of neutral stratification typical of many high latitude continental shelves solutions for ice drift and current velocity are obtained as a function of wind stress ice thickness and water depth the ocean is modeled by second order closure which allows continuous solutions from 5 m total depth to deep water results are presented with drag coefficients for the air ice ice water and water bottom interfaces specified from recent surveys from the bering sea shelf a region with broad areas of water depths between 20 and 50 m the solution shows little dependence on water depth for depths greater than 30 m this occurs because turbulent mixing is a decreasing function of water depth and offsets other influences of finite depth however for water depths less than 30 m ice velocities can change rapidly with wind speed and water depth and the presence of turbulence from tidal shear is very important for coupling wind driven ice drift to the bottom for the deep water limit the second order closure solution confirms analytic solutions that indicate an increase of 20 in the ratio of ice speed to wind speed as the wind speed increases from 10 to 25 m s

small aperture array translational and rotational seismograms from distant sources an example of the jan mayen mw 6 8 of 30 august 2012 earthquake abstract we present the seismic rotation rate due to the earthquake of mw 6 7 at the jan mayen island obtained from broad band seismograms at a distance of about 2740 km the order of magnitude of the rotation rate amplitude is only 10 9 rad s in this case it is studied with a focus on rotation to translation relations a joint analysis of the rotational and translational data allowed us to determine the true backazimuth and phase velocity of s and rayleigh waves for the surface waves we studied the frequency dependence of both the backazimuth and phase velocity wave dispersion the results are independently confirmed by a method based on time delays between translational records within a small aperture array both methods revealed an unusual velocity drop in the dispersion curve between the periods of 18 and 22 s this feature may be an indication of a low velocity zone in the lower crust

processes controlling the advance and retreat of sea ice in the sea of okhotsk using defense meteorological satellite program dmsp special sensor microwave imager ssm i sea ice data and meteorological data we investigate processes controlling the advance and retreat of sea ice in the sea of okhotsk for this investigation we apply a new algorithm to the ssm i data which is capable of calculating ice concentration and distinguishing sea ice types this algorithm is confirmed by comparison with national oceanic and atmospheric administration noaa advanced very high resolution radiometer avhrr imagery our investigations show that there exists a locality for the areas of new ice formation and the ice formation near the ice edge always occurs as a recovery after sea ice has retreated suddenly we also reveal that the speed of ice edge advance fairly coincides with that predicted by 2 of the geostrophic wind furthermore there exists a good correspondence between the times when the overall advance and retreat of ice cover begin and the decrease and increase of air temperature begin we conclude that the advance of the ice cover in the sea of okhotsk occurs primarily through ice advection by wind and that the interannual variation in the maximum sea ice extent can be interpreted by that in wind and air temperature conditions

dynamic and thermodynamic characteristics of atmospheric response to anomalous sea ice extent in the sea of okhotsk abstract influence of sea ice extent anomalies within the sea of okhotsk on the large scale atmospheric circulation is investigated through an analysis of the dynamic and thermodynamic characteristics of the response in an atmospheric general circulation model to specified anomalous sea ice cover significant response appears not only around the sea of okhotsk but also downstream over the bering sea alaska and north america in the form of a stationary wave train in the troposphere this remote response associated with wave activity flux emanating from the okhotsk area to the downstream is regarded as a stationary rossby wave generated thermally by the anomalous turbulent heat fluxes from the ocean surface as a result of the anomalous sea ice cover the pacific storm track in the model that extends zonally at 35 n is located too far south of the sea of okhotsk to exert substantial feedback forcing on the local and remote response since a similar stationary wave train is identified in the composite di

reinterpretation of the exposed record of the last two cycles of lake bonneville western united states a substantially modified history of the last two cycles of lake bonneville is proposed the bonneville lake cycle began prior to 26 000 yr b p the lake reached the bonneville shoreline about 16 000 yr b p poor dating control limits our knowledge of the timing of subsequent events lake level was maintained at the bonneville shoreline until about 15 000 yr b p or somewhat later when catastrophic downcutting of the outlet caused a rapid drop of 100 m the provo shoreline was formed as rates of isostatic uplift due to this unloading slowed by 13 000 yr b p the lake had fallen below the provo level and reached one close to that of great salt lake by 11 000 yr b p deposits of the little valley lake cycle are identified by their position below a marked unconformity and by amino acid ratios of their fossil gastropods the maximum level of the little valley lake was well below the bonneville shoreline based on degree of soil development and other evidence the little valley lake cycle may be equivalent in age to marine oxygenisotope stage 6 the proposed lake history has climatic implications for the region first because the fluctuations of lake bonneville and lake lahontan during the last cycle of each were apparently out of phase there may have been significant local differences in the timing and character of late pleistocene climate changes in the great basin second although the bonneville and little valley lake cycles were broadly synchronous with maximum episodes of glaciation environmental conditions necessary to generate large lakes did not exist during early wisconsin time

observed interaction between pacific sea ice and the western pacific pattern on intraseasonal time scales the relationship between north pacific sea ice and the western pacific wp pattern is examined using wintertime observational data between 1978 and 2008 weekly averaged data are chosen to capture the characteristically short time scale of the wp a clear relationship is found between the wp and sea ice concentrations in the bering sea where the positive polarity of the wp is accompanied by increasing sea ice concentrations and the negative wp by decreasing sea ice concentrations sea ice concentrations in the sea of okhotsk however are shown to be largely insensitive to the strength of the wp feedback of bering sea sea ice concentrations onto the wp is tested by fitting weekly averaged observations to a vector autoregressive var model results from the var model indicate that feedback of bering sea sea ice onto the wp plays a significant role in the dynamics of the wp and that this feedback is positive that is wp induced changes in bering sea sea ice concentrations help sustain existing wp conditions thereby lengthening the time scale of variability of the wp

observations of frazil ice formation and upward sediment transport in the sea of okhotsk a possible mechanism of iron supply to sea ice in the sea of okhotsk sediment incorporation transport and release by sea ice potentially plays important roles in the bio related material such as iron cycle and ecosystem the backscatter strength data of bottom mounted acoustic doppler current profilers have suggested signals of frazil ice down to 30 m depth and signals of upward sediment transport throughout the water column simultaneously in the region northeast of sakhalin with a water depth of 100 m such events occurred under turbulent conditions with strong winds of 10 20 m s 1 during such events newly formed ice was present near the observational sites shown by satellite microwave imagery sediment dispersion from the bottom occurred in association with strong currents of 1 0 1 5 m s 1 during these events the mixed layer reaches near the bottom due to wind induced stirring inferred from the high frequency component of vertical velocity thus the winter time turbulent mixing brings re suspended sediment up to near the ocean surface this study provides the first observational evidence of a series of processes on the incorporation of sedimentary materials into sea ice sedimentary particles are dispersed by the strong bottom current subsequently brought up to near the surface by winter time mixing and finally incorporated into sea ice through underwater interaction with frazil ice and or flooding of sea ice floes this wintertime incorporation of bottom sediment into sea ice is a possible mechanism of iron supply to sea ice which melts in spring and releases bio reactive iron into the ocean

variability of north pacific sea ice and east asia north pacific winter climate abstract sea ice variability in the north pacific and its associations with the east asia north pacific winter climate were investigated using observational data two dominant modes of sea ice variability in the north pacific were identified the first mode features a dipole pattern between the sea of okhotsk and the bering sea the second mode is characterized by more uniform ice changes throughout the north pacific using the principal components of the two dominant modes as the indices pc1 and pc2 analyses show that the positive phases of pc1 feature a local warming cooling in the sea of okhotsk the bering sea which is associated with the formation of the anomalous anticyclone extending from the northern pacific to siberia accompanied by a weakening of the east asian jet stream and trough the associated anomalous southeasterlies easterlies reduce the climatological northwesterlies westerlies leading to warm and wet conditions in northeast china and central siberia the positive phases of pc2

on the relationship between atmospheric circulation and the fluctuations in the sea ice extents of the bering and okhotsk seas monthly and 3 day averaged nimbus 5 electrically scanning microwave radiometer sea ice data have been analyzed to document the fluctuations of the bering sea and sea of okhotsk ice covers for the four winters 1972 1973 through 1975 1976 on the short term seasonal and interannual time scales and to define those periods for which there is an out of phase relationship between the fluctuations of the two sea ice covers the sea ice fluctuations are shown to be related to changes in the position and intensity of quasi stationary high and low pressure systems associated with large scale standing wave patterns in the atmosphere through a comparison of the areal changes in ice cover with changes in the amplitude and phase of zonal harmonics 1 2 and 3 of the sea level pressure field on the seasonal time scale the sea level pressure for december the month of most rapid seasonal sea ice growth for both the bering and okhotsk seas is dominated by harmonic 2 which explains almost 60 of the total sea level pressure variance on average over the four winters the phase of harmonic 2 which is associated with the position of the aleutian low shifts from 156 e in 1972 1973 to 190 e in 1975 1976 thus providing a connection between the increasingly heavy bering sea ice cover over these four winters and the general circulation of the atmosphere on the short term episodes of midwinter bering sea ice retreat are generally preceded by or coincident with the breakdown of harmonic 1 and the intensification of harmonics 2 and 3 these episodes are also related to the coincidence of the phases of harmonics 2 and 3 with a mean position of 165 e this result is in excellent agreement with a study of the north pacific oscillation showing that the two modes of the oscillation are associated with the longitudinal position of the aleutian low it is suggested here that these two modes result from changes in the amplitudes and phases of atmospheric long waves 1 2 and 3 evidence is also presented indicating that the interaction of standing and transient components of wave 1 may play an important role in these fluctuations finally these results establish an observational connection relating climate dynamics to changes in ice covers in seasonal sea ice zones

geoarchaeological dating of holocene stream terraces along the san pedro river southeastern arizona usa three pleistocene and four holocene floodplain terraces were differentiated along the san pedro river in southeastern arizona during a geological mapping project conducted by the arizona geological survey we used archaeological chronometric data to refine age estimates for the holocene surfaces that had been initially based on only geomorphic and pedologic criteria eight archaeological sites deeply buried in the fill of the most extensive holocene terrace map unit qy2r yielded 10 radiocarbon dates and temporally diagnostic san pedro complex 3150 1900 cal bp artifacts twenty sites recorded on the surface of qy2r terrace treads contained numerous temporally diagnostic hohokam 1950 500 cal bp ceramic sherds and features the age constraints provided by these archaeological materials suggest that the qy2r terrace fill was deposited primarily between 4500 and 1000 cal bp with only a thin veneer of flood deposits added between 1000 and 100 cal bp this late holocene to historical 4500 100 cal bp age estimate is consistent with other alluvial histories in the greater gila river drainage basin and supplants our initial geologically based latest holocene to historical 2000 cal bp qy2r age estimate the archaeologically derived maximum age estimate for qy2r also provides a minimum age for the topographically higher and older qy1r terrace prompting us to revise our original early to late holocene age estimate for qy1r to an early to middle holocene age range of 11 500 4500 cal bp the post a d 1850 historical age we originally proposed for the qy3r terrace deposits inset into qy2r however is consistent with the presence of four historical period surface sites and a concordant absence of surface and buried prehistoric sites

sediment provenance variations in the southern okhotsk sea over the last 180 ka evidence from light and heavy minerals in this study we investigate light and heavy minerals in sediment core os03 1 located at the academy of sciences rise of the southern okhotsk sea to determine their distributions and sources over the last 180 ka thousand years the sediment mainly consists of terrigenous and volcanic detritus ubiquitous drop stones and volcanic detritus throughout the core and high detrital input suggest that sea ice driven by wind and kamchatka current was the main transport agent of detrital materials to the southern okhotsk sea the ternary diagram of heavy minerals hornblende hypersthene epidote shows an expansion of detritus provenance from the eastern in cold periods to the northeastern in warm intervals of the okhotsk sea it mainly relates to the shift of aleutian low combined with previous records accumulation rates of quartz indicated a maximum extent but not perennial sea ice coverage during the glacial periods

reemergence mechanisms for north pacific sea ice revealed through nonlinear laplacian spectral analysis abstractthis paper studies spatiotemporal modes of variability of sea ice concentration and sea surface temperature sst in the north pacific sector in a comprehensive climate model and observations these modes are obtained via nonlinear laplacian spectral analysis nlsa a recently developed data analysis technique for high dimensional nonlinear datasets the existing nlsa algorithm is modified to allow for a scale invariant coupled analysis of multiple variables in different physical units the coupled nlsa modes are utilized to investigate north pacific sea ice reemergence a process in which sea ice anomalies originating in the melt season spring are positively correlated with anomalies in the growth season fall despite a loss of correlation in the intervening summer months it is found that a low dimensional family of nlsa modes is able to reproduce the lagged correlations observed in sea ice data from the north pacific ocean this mode family exists in both model output and observations and i

soil catena development on fault scarps of different ages eastern escarpment of the sierra nevada california abstract in quaternary tectonic studies soils are useful for estimating the ages of both faulted surficial deposits and colluvial wedges on the fault scarp slopes soil development on sloped landforms such as fault scarps varies with position on the slope thus an understanding of catenary relations is needed to interpret the fault scarp soils discussed here are some aspects of soil catena development on fault scarps formed by late quaternary normal faulting along the eastern escarpment of the sierra nevada between bishop and lake crowley california the fault scarps are multiple event scarps formed in pleistocene glacial and fluvial deposits composed mostly of granitic clasts and vegetated primarily with the great basin sagebrush community eolian additions to the soils are minor fault scarps formed since the tioga glaciation about 10 25 ka are high 6 26 m of vertical surface offset and steep 26 38 these fault scarps have probably been ruptured by faulting at least once during the holocene the upper parts of the post tioga fault scarps are bouldery and at the lower slope positions a finer grained colluvial wedge has accumulated in contrast to the post tioga fault scarps an old fault scarp mostly formed 100 ka ago and not ruptured by faulting in at least 15 22 ka has been degraded to a more gentle slope 17 and few boulders are exposed on the surface of the fault scarp on both age groups of fault scarps some soil properties and vegetation patterns suggest that there is more available moisture at the lower slope positions than elsewhere in the fault scarp catenas soils associated with the post tioga fault scarps are generally weakly developed a bw cox profiles that become cumulative at the lower slope positions in most places the difference in soil development between the original surface and the fault scarp is small and thus is a poor indicator of the age spread between the two surfaces in contrast to the post tioga soils soils on the old fault scarp are moderately developed a bt cox profiles that are better developed on the fault scarp slope than on the original surface increased soil development on the slope may reflect higher available moisture on the slope and erosion of the original surface through time on both the post tioga and the older fault scarps buried soils within the colluvium were rarely encountered the lack of buried soils may be due to a combination of low regional rates of soil development short interseismic time intervals for events forming the scarps and on the old fault scarp overprinting of soils by subsequent weathering and soil development a comparison of soil catena development on the two age groups of fault scarps suggests that after faulting ceases pedogenesis becomes the dominant process of the fault scarp although slope processes may continue to modify the fault scarp slope they proceed at rates that are lower than the rate of soil development

greenland sea sea ice variability over 1979 2007 and its link to the surface atmosphere 1 mean winter arctic sea ice concentration based on passive microwave observations for the period 1979 2007 are analyzed to examine the variability of the western nordic seas marginal ice zone miz a principal component analysis performed on this regional domain shows that the interannual variability is dominated by a mode which captures more than 70 of the total variance and shows only moderate correlation with the leading mode of global northern hemisphere sea ice variability this mode appears to be related to a pattern of sea level pressure slp anomaly centered on the miz with large scale signature resembling the canonical pattern of the north atlantic oscillation nao still this leading mode of sic variability shows a weak temporal correlation with the nao index taking into account the intrinsic spatial asymmetry found between the two phases of the nao based on a weather regimes analysis composite sic fields are constructed which indeed suggest a preferential response of the greenland sea sic variability to negative nao like patterns of slp the slp pattern is consistent with a response of the sea ice margin to the strength of the northerly winds along eastern greenland a weak pattern of surface air temperature anomalies also emerges in the central greenland sea which occurs at least partly as a response of the surface atmosphere to sea ice concentrations changes higher order modes of winter sic variability emerge based on a shorter winter season one mode has much resemblance with the odden nordbukta pattern while another one exhibits a significant signature in the center of the greenland sea convective gyre the odden nordbukta mode shows a more symmetric relation to the nao than the leading sic mode linear regression analysis consistently suggests some link between this mode and the ice area flux through fram strait

relation of material exchange between sea ice and water to a coupled ice ocean ecosystem at the hokkaido coastal region of the okhotsk sea 1 in this paper the material exchange between the sea ice and the water just below the ice and its relation to the lower trophic ice system are examined using field observations in the hokkaido coastal region of the okhotsk sea and a coupled ice ocean ecosystem model which in detail formulates the material exchange between the ice and the water the accuracy of the model is confirmed by a comparison of the results of the numerical computation with the observations the estimation of the transport of the organic carbon and nutrients based on the computation demonstrates that the physical coupling effect between the ice and water plays a prominent role in supplying the nutrients from the water to the ice ecosystem and in efficiently releasing the organic matter produced by the primary producer in the ice ice algae as a result this study quantitatively clarifies that the physical coupling effect tidal mixing and biological activity in the ice drive the material cycle in the ice and water under the ice

estimates of vertical crystal strain rates along the western margins of the colorado plateau dating of basalts of late cenozoic age that have been displaced by recurrent movement along fault systems of the western colorado plateau indicates that perennial streams downcut quickly after uplifts the rate of downcutting of the offset basalts upstream from a fault is largely a function of the amount of uplift minimum uplift rates can be estimated by comparing present stream profiles to the profiles that existed before extrusion of the lava flows a preliminary study of the valleys of the virgin river and adjacent drainage systems indicates that the eastern margin of the basin and range province has been rising in relative altitude at roughly 25 m m y in the grand wash area at least 90 m m y in the block between the grand wash and hurricane faults and 390 m m y in the block east of the hurricane fault

the contribution of alaskan siberian and canadian coastal polynyas to the cold halocline layer of the arctic ocean numerous arctic ocean circulation and geochemical studies suggest that ice growth in polynyas over the alaskan siberian and canadian continental shelves is a source of cold saline water which contributes to the maintenance of the arctic ocean halocline the purpose of this study is to estimate for the 1978 1987 winters the contributions of arctic coastal polynyas to the cold halocline layer of the arctic ocean the study uses a combination of satellite oceanographic and weather data to calculate the brine fluxes from the polynyas then an oceanic box model is used to calculate their contributions to the cold halocline layer of the arctic ocean this study complements and corrects a previous study of dense water production by coastal polynyas in the barents kara and laptev seas recurrent polynyas form on the canadian and alaskan coasts from banks island to the bering strait and on the siberian coast from the bering strait to the new siberian islands in the bering sea polynyas form in norton sound south and west of st lawrence island and in the gulf of anadyr two regions that account for almost 50 of the total dense water production are the siberian coastal polynyas in the adjacent regions of the gulf of anadyr and anadyr strait and the alaskan coastal polynyas which occur along the coast from cape lisburne to point barrow for all of the western arctic coastal regions examined the mean annual total brine flux is 0 5 0 2 sv combination of this flux with the contribution from the barents kara and laptev seas which is recalculated from data in the earlier study shows that over the entire arctic coastal polynyas generate about 0 7 1 2 sv of dense water this compares well with the theoretical estimates of 1 1 5 sv because an unknown fraction of the barents kara and laptev brine flux must go to the eurasian basin deep water the coastal polynyas alone cannot renew the halocline layer other potential brine generation mechanisms include overall freezing on the shelves and the response of the ice to infrequent violent storms for example during february 1982 an intense storm generated a large region of low ice concentration in the eastern chukchi sea over barrow canyon the refreezing of the region was followed by the flow of a dense plume down barrow canyon although the ocean dynamical response to this refreezing needs to be established the possible response of a barrow canyon flow to this refreezing event suggests that the overall refreezing in response to infrequent violent storms may be a potential source of the additional brine needed to maintain the arctic ocean halocline

seasonal and regional manifestation of arctic sea ice loss abstractthe arctic ocean is currently on a fast track toward seasonally ice free conditions although most attention has been on the accelerating summer sea ice decline large changes are also occu

degradation of selected terrestrial and martian impact craters degraded craters on mars record the cumulative effects of the complex interplay between erosion transport and deposition by competing intermittent processes fortunately impact craters are instantaneous landforms common to both the earth and mars that are characterized by similar topography and local lithofacies deconvolving the signatures of individual degradation processes around young craters on earth e g drainage scale and density changing wall slope deflation features allows calibrating degradation signatures around craters on mars and places first order limits on controlling processes and perhaps past climates such comparisons are valid despite differences in vegetation cover and time scales over which activity occurs on the two planets analysis of degradation at meteor crater lonar crater and talemzane crater reveals a terrestrial sequence of advancing degradation by fluvial eolian and mass wasting processes at meteor crater fluvial processes currently dominate primary erosion however combined deflation from the ejecta and both alluvium and colluvium make eolian processes most important in overall ejecta degradation lonar and talemzane reveal that advancing fluvial degradation is characterized by larger drainages and decreasing wall slopes at talemzane interior drainages breach the rim crest and pirate headward regions of exterior drainage basins when comparable degradation signatures resolvable at viking resolutions are used in selected areas on mars important differences from the terrestrial sequence are revealed all morphologies of craters in southern ismenius lacus sil are typically incised by small valleys with low drainage densities display rare alluvial deposits possess walls sloped at the angle of repose and are sometimes partially covered by airfall deposit remnants analogy with the terrestrial craters indicates signatures associated with advancing fluvial degradation should be readily detected on mars together with other differences between degraded craters on the two planets the paucity of fluvial signatures in sil implies that mass wasting and eolian activity predominated degradation of martian craters preserved since the hesperian crater statistics for sil indicate most craters were degraded during geologically brief intervals in the noachian and mid hesperian therefore fluvial signatures preserved in sil imply any runoff since the hesperian was short lived locally debouched and unrelated to rainfall

frequency and size of quaternary surface ruptures of the pitaycachi fault northeastern sonora mexico movements along the pitaycachi fault since the miocene juxtaposed different alluvial units and created 2 to 45 m high fault scarps downslope from a pedimented mountain front prior to 1887 in 1887 a major earthquake formed a 75 km long 1 2 to 4 m high scarp along the trace of prehistoric surface ruptures diverse evidence from many study sites indicates that about 200 000 yr elapsed between the prior youngest pleistocene event and the 1887 surface rupture cumulative displacements of pliocene to mid pleistocene alluvial fans and stream terraces decrease with decreasing age the trace of the prior rupture was largely buried by sheets of late pleistocene and holocene piedmont alluvium late pleistocene soils are offset about the same amount as the height of the 1887 scarp valleys that are as much as 40 m deep and 0 5 to 0 9 km wide have been eroded since the prior event they contain multiple late pleistocene and holocene stream terraces that were not faulted until 1887 pre 1887 alluvial fault scarps were degraded to 2 to 9 slopes before the 1887 event even in resistant materials such as clay rich soil horizons with unweathered rhyolite cobbles and calcrete scarp height maximum slope regressions and diffusion equation analyses for reconstructed pre 1887 scarp profiles indicate that the prior event occurred more than 100 000 yr ago acceleration of scarp degradation rates during the holocene and or relatively resistant materials exposed in the scarps would increase the age estimates to 200 000 yr or more very long recurrence intervals are the characteristic style of movement on the pitaycachi fault at one site six ages of diverse valley fills were inset into pedimented granodiorite upslope from the fault between the prior and 1887 events only 3 m of relief remained before the 1887 rupture increased the scarp height from 3 to 6 m some hillslopes have triangular talus facets of carbonatecemented colluvium that resulted from infrequent fault movements and intervening periods of erosion smooth hillsides of resistant volcanic rocks between the facets show that virtually all of the prior surface rupture event scarps had been removed by prolonged slope degradation

mechanisms for the variation of sea ice extent in the northern hemisphere using daily sea ice data derived from satellite borne sensors and atmospheric data we examined processes controlling the variation of sea ice extent in the northern hemisphere the daily ice motion field was computed from imagery of the defense meteorological satellite program dmsp special sensor microwave imager ssm i for seven winters december to april from 1991 1992 to 1997 1998 by employing the maximum cross correlation method in order to examine mechanisms of the temporal variation of the ice extent we analyzed 50 specified lines across the daily ice edge although a high correlation between the ice motion and the geostrophic wind speed was observed in all the ice edge areas the degree for correlation between the speed of the ice edge displacement and the wind speed varied with region the degree for response of the ice edge speed to the wind speed largely depended upon that of the ice edge speed to the ice motion the following mechanisms controlling the variation of ice extent for regions in the northern hemisphere were anticipated in the barents sea bering sea and the sea of okhotsk the ice extent advances by wind driven ice advection and the daily scale variation of the ice extent were also controlled by the variation in wind speed in contrast the ice extent in the labrador sea and the greenland sea seemed to be considerably affected by oceanographic factors such as the location of the thermal front and was not related to the variation in wind speed the regional difference of the variation mechanism was also reflected in the interannual variation in maximum ice extent

dating quaternary fault scarps formed in alluvium using morphologic parameters abstract ages of fault scarps as well as those other types of transport limited slopes can be estimated by comparing their morphology with the morphology of scarps of known age age estimates are derived by fitting the scarp profiles to synthetic profiles generated using a diffusion equation or alternatively by classification using a linear discriminant function the usefulness of morphology derived age estimates depends on the relative importance of non age related morphologic variation data from more than 200 scarp profiles demonstrate that morphologic variation not related to scarp age can introduce significant uncertainties into morphology derived age estimates

coherent sea level variation in and around the sea of okhotsk abstract we investigated the seasonal and interannual variations of the sea level in and around the sea of okhotsk and their causes based on tide gauge and satellite altimeter data the sea level all along the coastal region of the sea of okhotsk is found to be dominated by the seasonal variation with a maximum in winter and a minimum in summer which cannot be explained by the annual cycle of atmospheric heat flux and pressure this sea level variation appears to reflect ocean current variations both the arrested topographic waves atws caused by alongshore wind stress and the sverdrup transport by wind stress curl show corresponding seasonal variations seasonal amplitude of the sea level is relatively large along sakhalin island with a tendency of a larger amplitude toward the south this meridional dependence is consistent with the atws but not with the sverdrup transport in the sea of okhotsk seasonal variation of the geostrophic current velocity expected from the sea level variation is comparable to that of the observed nearshore current and is consistent with the theoretical atw transport it is also revealed that on an interannual timescale the wintertime sea level fluctuates quite coherently all around the sea of okhotsk and further along the east kamchatka and oyashio coasts in the north pacific the altimeter data clearly show that this coherent sea level variation is trapped over the coastal and continental shelf regions with depths shallower than 1000 m the wintertime sea levels have a higher correlation with the atw transport than with the sverdrup transport in the sea of okhotsk and the upstream east kamchatka coast all these suggest that the interannual sea level variation along the coastal and shelf regions in winter as well as the seasonal variation is mainly caused by the atws coastal trapped current forced by the alongshore wind stress the wintertime sverdrup transport raised by the previous studies is the secondary contributor to these variations

on the seasonal sea ice cover of the sea of okhotsk free of ice 4 months of the year the sea of okhotsk begins to freeze over in a few coastal locations in november attains its maximum ice coverage usually in mid march and by june retains ice in only a few coastal regions this sequence is well recorded by satellite imagery from the electrically scanning microwave radiometer esmr on board nimbus 5 four years of esmr data reveal significant interannual variations in the maximum ice cover and in the smoothness of the growth and retreat periods of the years 1973 1976 the heaviest ice cover occurred in 1973 and the growth period most interrupted by temporary ice edge retreats was in 1974 comparison of the general features of the cycle of sea ice distribution with basic oceanographic factors shows that ice forms first in cold shallow low salinity waters and then seems to drift in a direction approximating the okhotsk kuril current system two basic patterns of ice edge positioning which occur frequently in the esmr data are identified as a rectangular structure and a wedge structure each of these is strongly correlated with the bathymetry of the region and with the known current system suggesting that convective depth and ocean currents play an important role in determining ice patterns certain major interannual variations in the ice extents are accounted for by interannual contrasts in the atmospheric pressure fields

dynamic strains at regional and teleseismic distances abstract we develop formulas for the size of dynamic strains caused by seismic waves from an earthquake of given magnitude and distance these formulas include peak strain peak dissipated power and total dissipated energy and they are applicable at regional and teleseismic distances the formulas are fits to data from 89 large 6 5 m w 9 0 shallow earthquakes with source distances between 500 and 16 000 km recorded between 1977 and 2013 by three long base laser strainmeters at pinon flat observatory in southern california these strainmeters provide uniquely well calibrated measurements of tensor strain the residuals to the fits suggest that strain values can usually be predicted to within a factor of 2 these data also show that the strain tensor can be substantially different from that expected for plane waves in particular the extension perpendicular to the back azimuth which should be zero is always 20 or more of the extension along that azimuth how much the strains resemble those for plane waves depends on their path perhaps because inhomogeneities along different paths produce different amounts of multipathing the observed strains are systematically 10 30 larger at nearby laser strainmeter sites in the salton trough suggesting local amplification from inhomogeneous crustal structure online material tables of earthquake catalogs and dynamic strain analysis and figures of earthquake magnitude distance distributions and time delays of maximum strain

influence of okhotsk sea ice extent on atmospheric circulation an atmospheric general circulation model was used to investigate the influence of okhotsk sea ice on large scale atmospheric circulation significant differences in the model responses between heavy and light ice cover are evident not only around the sea of okhotsk but also downstream towards north america in the form of a stationary wavetrain in the troposphere because the wave activity flux associated with the wavetrain emanates downstream from the sea of okhotsk this remote response is regarded as a stationary rossby wave excited thermally through an anomalous surface heat flux over the sea of okhotsk the wavetrain is thermally reinforced downstream by the anomalous heat flux associated with wind anomalies over the ocean surface which are induced by the wavetrain itself

estimation of sea ice production in the bering sea from amsr e and amsr2 data with special emphasis on the anadyr polynya

satellite passive microwave studies of the sea of okhotsk ice cover and its relation to oceanic processes 1978 1982 this paper describes the use of the nimbus 7 scanning multichannel microwave radiometer smmr satellite data to study the ice cover in the sea of okhotsk during the four winters of 1978 1982 the ice concentration estimates obtained from smmr are used to study two different polynyas one over the kashevarova bank and the other over the northwest continental shelf for the kashevarova polynya this study shows that the polynya which may be related to the upwelling observed in historic summer cruises occurs directly over the bank for the continental shelf which because of strong offshore winds and cold temperatures is a region of high ice production the polynya areas are combined with heat flux estimates from weather station data to yield the production rates of ice salt and dense shelf water as a previous study by kitani 1973 shows the mixing of this dense shelf water with pacific water yields a water mass unique to the okhotsk which is the layer of cold low salinity intermediate water between depths of 150 and 800 m from our calculations we estimate that the dense shelf water is produced at an annual rate of about 0 5 sv and that the intermediate water is produced at a rate of 1 2 sv which yields a renewal time for this layer of 10 40 years

evolution of the bonneville shoreline scarp in west central utah comparison of scarp analysis methods and implications for the diffusion model of hillslope evolution abstract wave cut pluvial shoreline scarps are ideal natural experiments in hillslope evolution because the ages of these scarps are often precisely known and because they form with a range of heights alluvial textures and microclimates i e orientation previous work using midpoint slope methods on pluvial scarps in the basin and range concluded that scarp evolution is nonlinear and microclimatically controlled the purpose of this study was to further examine the influence of scarp height texture and microclimate in an attempt to calibrate a nonlinear model of scarp evolution to do this over 150 profiles of the bonneville shoreline in the adjacent snake and tule valleys west central utah were collected and analyzed by fitting the entire scarp profile to diffusion equation solutions taking into account uncertainty in the initial scarp angle in contrast to previous studies this analysis revealed no evidence for nonlinearity or microclimatic control to understand the reason for this discrepancy we undertook a systematic study of the accuracy of each scarp analysis method the midpoint slope inverse method was found to yield biased results with systematically higher diffusion ages for young tall scarps the slope offset method is unbiased but has limited resolution because it requires many scarp profiles to yield a single diffusion age a method that incorporates the full scarp profile and uncertainty in the initial scarp angle was found to be the most accurate technique the application of the full scarp method to the bonneville shoreline supports the use of a linear diffusion model for scarps up to 20 m in height scarp orientation had no discernable effect on diffusivity values soil texture was found to have a weak but significant inverse relationship with diffusivity values

multiyear sea ice variability in the eastern bering sea an update time series of sea surface temperature sst percent ice cover degree day and surface wind anomalies are updated from niebauer 1980 for the period 1974 1982 from the eastern bering sea these data are used to provide further documentation of the recent short term 1977 present climatic warming trend in the region of the eastern bering sea the data analysis indicates that the warming trend is statistically significant and that it ended in 1979 details of the anomalies in sst ice and surface and 700 mbar winds are updated for the individual winters of 1979 82 are compared and contrasted to the recent multiyear warming trend and are discussed in relation to longer term studies of air ice sea interactions in this region

on the association between spring arctic sea ice concentration and chinese summer rainfall 1 a statistical relationship between spring arctic sea ice concentration sic and chinese summer rainfall is identified using singular value decomposition svd results show that decreased increased spring sic in the arctic ocean and the greenland sea corresponds to increased decreased summer rainfall in northeast china and central china between the yangtze river and the yellow river 28 36 n and decreased increased rainfall in south china corresponding summer 500 hpa height anomalies show a eurasian wave train structure which originates in northern europe and extends southeastwards to northeast china and a south north dipole structure over east asia south to lake baikal such a spatial distribution of 500 hpa height anomalies and corresponding summer rainfall anomalies cannot be entirely attributed to the impact of east asian summer monsoon easm variability the spring arctic sic provides a complementary precursor for chinese summer rainfall variability the combined impacts of both spring arctic sic and eurasian snow cover on the eurasian wave train may explain their statistical linkage

the accuracy of seismic estimates of dynamic strains an evaluation using strainmeter and seismometer data from pinon flat observatory california abstract the dynamic strains associated with seismic waves may play a significant role in earthquake triggering hydrological and magmatic changes earthquake damage and ground failure we determine how accurately dynamic strains may be estimated from seismometer data and elastic wave theory by comparing such estimated strains with strains measured on a three component long base strainmeter system at pinon flat california we quantify the uncertainties and errors through cross spectral analysis of data from three regional earthquakes the m 0 4 10 17 n m st george utah m 0 4 10 17 n m little skull mountain nevada and m 0 1 10 19 n m northridge california events at distances of 470 345 and 206 km respectively our analysis indicates that in most cases the phase of the estimated strain matches that of the observed strain quite well to within the uncertainties which are about 0 1 to 0 2 cycles however the amplitudes are often systematically off at levels exceeding the uncertainties about 20 in one case the predicted strain amplitudes are nearly twice those observed we also observe significant strains tangential direction which should be zero theoretically in the worst case the rms strain exceeds the other nonzero components these nonzero strains cannot be caused by deviations of the surface wave propagation paths from the expected azimuth or by departures from the plane wave approximation we believe that distortion of the strain field by topography or material heterogeneities give rise to these complexities

debris flows as geomorphic agents in the huachuca mountains of southeastern arizona abstract numerous debris flows occurred in the huachuca mountains of southeastern arizona during the summer rainy season of 1988 in areas that were burned by a forest fire earlier in the summer debris flows occurred following a major forest fire in 1977 as well suggesting a causal link between fires and debris flows abundant evidence of older debris flows preserved along channels and in mountain front fans indicates that debris flows have occurred repeteadly during the late quaternary in this environment soil development in sequences of debris flow deposits indicates that debris flows probably recur over time intervals of several hundred to a thousand years in individual drainage basins in the study area surface runoff in the steep drainage basins of the huachuca mountains is greatly enhanced following forest fires as the hillslopes are denuded of their vegetative cover water and sediment eroded from the hillslope regolith are rapidly introduced into the upper reaches of tributary channels by widespread rilling and slope wash during rainfall events this influx of water and sediment destabilizes regolith previously accumulated in the channel triggering debris flows that scour the channel to bedrock in the upper reaches following a debris flow the scoured trapezoidally shaped channel gradually assumes a swale shape and the percentage of exposed bedrock declines as material is introduced from the slopes debris flows do a tremendous amount of work in a very short time however and are the major channel forming events where the tributary channels enter larger trunk channels the debris flows serve as the main source of very coarse sediment the local slope and coarse particle distribution of the trunk channel depend on the competence of water flows in the channel to transport the material introduced by debris flows where the smaller channels drain directly to the mountain front debris flows create extensive alluvial fans which dominate the morphology of the basin range boundary time intervals between debris flows in the drainage basins of the huachuca mountains are probably controlled by complex interactions among climate forest fires and slope processes fires destroy the protective vegetation that stabilizes the upper catchment slopes and inhibits erosion however not every fire that burns a catchment causes debris flows because sufficient weathered material must accumulate in the upper channel reaches to initiate a large debris flow if such accumulation has not occurred the material introduced to a channel following a forest fire will move only a short distance down the channel thus the episodic nature of debris flows probably depends on rates of slope weathering and erosion which are in turn controlled by climate both directly and through vegetation and forest fires

thermohaline effects of the seasonal sea ice cover in the sea of okhotsk 1 by using a coupled ice ocean model the seasonal extent of the sea ice cover in the sea of okhotsk was examined the model results show that the sea ice at the ice edge is advected southward along sakhalin island with a mean velocity of 0 31m s into ocean water with temperatures above freezing as a result even in mid winter a large amount of ice melting occurs around the edge it results in temperature decrease in the surface mixed water during the 1993 1994 winter the total volume ratio of ice melting to ice production is estimated at 0 76 the negative latent heat flux from the ice melting is nearly comparable to the total atmospheric heat flux around the ice edge furthermore the meltwater supply to the surface layer is estimated to be approximately 3 5 times the annual amur river inflow thus it is concluded that the ice melting around the extending ice edge is a significant factor for the heat and salt balance between the sea ice and the surface mixed layer and plays an important role in the maintenance of the large seasonal sea ice extent in the sea of okhotsk

the sea ice extent anomaly in the north pacific and its impact on the east asian summer monsoon rainfall the relationship between extreme anomalies of the spring sea ice extent over the bering sea and the sea of okhotsk and rainfall variability in the east asian summer monsoon was examined through an analysis of observed data and modeling experiments the results show that reduced sea ice extent leads to an enhanced summer monsoon rainfall in southeastern china this relationship is well supported by the background atmospheric circulation changes and the stationary wave dynamics a difference in the 500 hpa geopotential height composed from the ncep ncar reanalysis data and model output between the light and heavy sea ice cases shows an anomalous high in the east asian summer which favors the invasion of a cold air mass into southern china and prevents the east asian summer monsoon from advancing northward hence the mei yu front and its associated rainfall intensify and stay in southeastern china the generation of the summer anomalous high and its interseasonal link to the spring sea ice extent anomalies can be accounted for by the stationary wave dynamics and the land surface process in spring the decrease in sea ice extent forces eastward propagating wave activity flux and causes an anomalous high in europe along with a decrease in precipitation the decreased soil water content results in a higher land surface temperature and more sensible heat flux in summer and this strengthens summer stationary wave activities in europe the eastward propagation of the wave energy and its intensification in east asia are responsible for the anomalous high in the east asian summer in this process the european land surface acts as a bridge linking the spring sea ice extent anomalies with the east asian summer monsoon

the long lasting aftershock series of the 3 may 1887 mw 7 5 sonora earthquake in the mexican basin and range province we study local and regional body wave arrival times from several seis mic networks to better define the active regional fault pattern in the epicentral region of the 3 may 1887 mw 7 5 sonora mexico southern basin and range province earthquake we determine hypocenter coordinates of earthquakes that originated between 2003 and 2007 from arrival times recorded by the local network resnes red sismica del noreste de sonora and stations of the network of autonomously recording seismographs nars baja array for events between april and december 2007 we also incorporated arrival times from usarray stations located within 150 km of the united states mexico border we first obtained preliminary earthquake loca tions with the hypoinverse program klein 2002 and then relocated these initial hypocenter coordinates with the source specific station term ssst method lin and shearer 2005 most relocated epicenters cluster in the upper crust near the faults that ruptured during the 1887 earthquake and can be interpreted to be part of its long lasting series of aftershocks the region of aftershock activity extends along the same fault zone 40 50 km south of the documented southern tip of the 1887 rupture and includes faults in the epicentral region of the 17 may 1913 imax viii mi 5 0 0 4 and 18 december 1923 imax ix mi 5 7 0 4 granados huasabas sonora earthquakes which themselves are likely to be aftershocks of the 1887 event the long aftershock duration can be explained by the unusually large magnitude of the mainshock and by the low slip rates and long mainshock recurrence times of the faults that ruptured in 1887

the santa rita fault zone evidence for large magnitude earthquakes with very long recurrence intervals basin and range province of southeastern arizona a discontinuous zone of subdued west facing fault scarps offset quaternary alluvium along 58 km of the western piedmont of the santa rita mountains south of tucson arizona scarps trend ne to n s and are 1 to 6 km basinward from the deeply embayed mountain front scarp heights range from 1 to 7 m and maximum scarp slope angles range from 3 to 9 5 a 6 m deep trench excavated in middle pleistocene and younger deposits exposed a high angle fault zone with about 3 5 m of total displacement estimated ages of faulted and unfaulted surfaces extent of degradation of piedmont scarps and stratigraphic relations exposed in the trench suggest an age of about 100 ka for the most recent surface rupture event units having well developed relict soils of late pleistocene age and older are faulted whereas units having weakly to moderately developed soils of latest pleistocene and holocene age are not offset morphologic fault scarp analyses suggest an age of 60 to 100 ka earthquake magnitude estimates derived using minimum and maximum seismic source moment calculations range from 6 4 to 7 3 one or more earlier surface rupture events are implied by significantly high scarp heights on mid pleistocene than on late pleistocene surfaces scarp heights on middle and early pleistocene surfaces are similar restricting faulting to post middle pleistocene time 200 to 300 ka stratigraphic relationships observed in the trench also suggest two fault displacement events tectonic landform analysis of the mountain front piedmont area implies several m y of inactivity along the range bounding fault system prior to these late quaternary displacements extremely long recurrent intervals between displacement events and reactivation of faulting after an interval of tectonic quiescence are typical of late quaternary fault behavior in southeastern arizona

the arctic winter sea ice quadrupole revisited abstractthe dominant mode of arctic sea ice variability in winter is often maintained to be represented by a quadrupole structure comprising poles of one sign in the okhotsk greenland and barents seas and of opposing sign in the labrador and bering seas forced by the north atlantic oscillation this study revisits this large scale winter mode of sea ice variability using microwave satellite and reanalysis data it is found that the quadrupole structure does not describe a significant covariance relationship among all four component poles the first empirical orthogonal mode explaining covariability in the sea ice of the barents greenland and okhotsk seas is linked to the siberian high while the north atlantic oscillation only exhibits a significant relationship with the labrador sea ice which varies independently as the second mode the principal components are characterized by a strong low frequency signal because the satellite record is still short these results suggest that statistical anal

the north pacific oscillation west pacific teleconnection pattern mature phase structure and winter impacts abstract the north pacific oscillation npo in sea level pressure and its upper air geopotential height signature the west pacific wp teleconnection pattern constitute a prominent mode of winter midlatitude variability the npo wp its mature phase expression is identified from principal component analysis of monthly sea level pressure variability as the second leading mode just behind the pacific north american variability pattern npo wp variability primarily on subseasonal time scales is characterized by a large scale meridional dipole in slp and geopotential height over the pacific and is linked to meridional movements of the asian pacific jet and pacific storm track modulation the hemispheric height anomalies at upper levels resemble the climatological stationary wave pattern attributed to transient eddy forcing the npo wp divergent circulation is thermal wind restoring pointing to independent forcing of jet fluctuations intercomparison of sea level pressure geopotential height and zonal

introduction to the special issue on rotational seismology and engineering applications rotational seismology is an emerging field for studying all aspects of ro tational ground motions induced by earthquakes explosions and ambient vibrations it is of interest to a wide range of geophysical disciplines including strong motion seismology broadband seismology earthquake engineering earthquake physics seis mic instrumentation seismic hazards seismotectonics and geodesy as well as to physicists using earth based observatories for detecting gravitational waves generated by astronomical sources predicted by einstein in 1916 in this introduction to the bssa special issue on rotational seismology and engineering applications we will include 1 some background information 2 a summary of the recent events that led to this special issue and 3 an overview of its 51 papers 27 articles 11 short notes 4 reviews 6 tutorials and 3 supplementary articles our comments on these 51 papers are very brief and give just a hint of what the papers are about papers in this special issue demonstrate that earthquake monitoring cannot be limited to measuring only the three components of translational motion we also need to simultaneously measure the three components of rotational motion and the many components of strains a golden opportunity to improve our understanding of earth quakes lies in the near field of large earthquakes within about 25 km of the earthquake ruptures where nonlinear rock and soil response influences ground motions in a com plicated way

along strike upper plate deformation in response to metamorphic core complex emplacement se arizona abstract metamorphic core complexes represent concentrated zones of crustal extension universally the hanging walls of these systems are extensively fractured attesting to the significant horizontal extension above the evolving detachment zone recent analysis of a large grid of 2 d seismic reflection lines within the tucson basin of southeastern arizona has facilitated a nearly three dimensional interpretation of subsurface features related to cenozoic crustal extension within the northern tucson basin the catalina detachment fault dips 23 35 to the southwest from the western flank of the catalina rincon metamorphic core complex in the southern portion of the basin the ne trending santa rita normal fault dips 15 20 to the northwest from the western flank of the santa rita mountains and is cut by the catalina detachment beneath the central tucson basin the orientation of the santa rita fault is problematical in that its orientation is nearly perpendicular to extension directions in the region while geologic and seismic reflection evidence indicates that the catalina detachment and santa rita fault were active synchronously one possible explanation is that the santa rita fault is accommodating along strike upper plate deformation in response to core complex emplacement to test this we employed a finite element modeling approach a two dimensional model consisting of a homogenous elastic material undergoing uniform extension is used to study changes in stresses and displacements in proximity to a zone of weakness representing a detachment fault in the upper crust away from the detachment fault primary principal stresses are oriented parallel to the regional extension direction as expected near the detachment extension in the system produces a rotation of the primary principal stresses of nearly 60 with respect to the regional stress field around the end of the fault additionally the model predicts mechanical failure of the upper plate of the detachment system to the south of the catalina core complex this model supports our interpretation that the orientation and early displacement noted on the santa rita fault is the result of a perturbation in the regional stress field caused by the catalina detachment and the associated brittle failure of the upper plate from the extreme crustal extension associated with core complex emplacement

cyclone climatology of the bering sea and its relation to sea ice extent abstract a monthly storm track climatology is derived from monthly maps of cyclone tracks for the winter season october through march averaged over 23 years 1957 58 1979 80 for a 2 latitude 4 longitude grid bounded by 51 n 65 n 157 w and 171 e there is a decrease in the number of cyclones with latitude in all months and division into two storm tracks one propagating north northeast along the siberian peninsula and one entering the southern bering sea on a northeasterly course and either curving northward into the central bering sea or continuing parallel to the aleutian island chain monthly average ice extents are established for february and march 1958 80 along a line from norton sound southwest toward the ice edge perpendicular to the average maximum extent comparison of composite cyclone charts summed over the winter season and over the five heaviest and five lightest ice years shows a shift in cyclone centers toward the west in light ice years the correlation between maximum seasonal ice

seismicity in the epicentral region of the 1887 northeastern sonoran earthquake mexico the 1887 sonoran earthquake in northeastern sonora mexico has an 80 km rupture length with an average 3 m displacement and an assumed 16 km depth of rupture this corresponds to a seismic moment of 1 27 x 1027 dyne cm and an ms of 7 4 seven to ten portable seismographs with an average spacing of 10 km were operated in a 2800 km 2 region surrounding the 1887 fault scarp thirtythree earthquakes were detected during 30 days of usable recording for all events 1 3 m 2 the most accurate locations horizontal error 5 km define a west dipping normal range bounding fault all events occurred within 15 km of the surface the name pitaycachi fault after the most prominent peak of the horst block is proposed for this zone of active faulting seismicity along the zone terminates abruptly 13 km north of the fault scarp and extends to the south for at least 32 km beyond the southern a composite focal mechanism from events at the southern end of the 1887 scarp indicates a normal fault striking n35 e and dipping 72 to the northwest

present day motion and deformation of the colorado plateau 1 we analyze data from continuous gps stations in the southwestern united states and present the first observations of a systematic motion of the colorado plateau region relative to a north america fixed reference frame westward velocities increase rapidly across the wasatch fault system which comprises the plateau s northwestern margin but increase more gradually between the great plains and the mojave desert province we detect no significant extension across most of the rio grande rift but extension could be as high as 0 5 mm yr 1 along its southernmost portion we suggest that the motion between the plateau and stable continent may partly be accommodated instead across the jemez lineament only when we consider gps velocities within the plateau s center do the data support a rigid body rotation of 0 103 ma 1 around a pole in the northern rocky mountains we conclude that active extension has encroached into the plateau from both the east and west

reconstruction of mid cenozoic extension in the rincon mountains area southeastern arizona usa and geodynamic implications nsf ear 1649254 u s geological survey national cooperative geologic mapping program under statemap grant 03hqag0114 statemap grant 06hqag0051 g09ac00199

effect of far field slope on morphologic dating of scarplike landforms the principal finding of this paper is that the far field slope has a first order effect on model age determinations of scarplike landforms in weakly consolidated terrains observationally this can be demonstrated in two ways using the lake bonneville and lahontan shoreline scarps as separate and combined data sets use of the reduced scarp slope tan theta sub s minus b where theta sub s is the maximum scarp angle and b is the far field or fan slope instead of tan theta sub s alone as the measure of scarp slope measurably reduces separation between the two data sets induced by different average fan slopes for the two data sets and significantly reduces scatter in the slope offset plot for both the separate and combined data sets theoretically the argument can be put even more strongly at least within the range of linear and nonlinear diffusion models that the authors consider here together with a mathematical transformation of the empirical approach of r c bucknam and r e anderson when one correctly takes into account the far field slope one will basically get the same age determination no matter which of these models one uses conversely without accounting properly for the effect of far field slope one is virtuallymore guaranteed to get an erroneous age determination no matter which model is used less

the atmospheric response to realistic arctic sea ice anomalies in an agcm during winter abstract the influence of realistic arctic sea ice anomalies on the atmosphere during winter is investigated with version 3 6 of the community climate model ccm3 6 model experiments are performed for the winters with the most 1982 83 and least 1995 96 arctic ice coverage during 1979 99 when ice concentration estimates were available from satellites the experiments consist of 50 member ensembles using large ensembles proved critical to distinguish the signal from noise the local response to ice anomalies over the subpolar seas of both the atlantic and pacific is robust and generally shallow with large upward surface heat fluxes 100 w m 2 near surface warming enhanced precipitation and below normal sea level pressure where sea ice receded and the reverse where the ice expanded the large scale response to reduced enhanced ice extent to the east west of greenland during 1982 83 resembles the negative phase of the arctic oscillation north atlantic oscillation ao nao with a ridge over t

effects of el nino southern oscillation and north pacific weather patterns on interannual variability in the subarctic bering sea extraordinary interannual variability in ice cover air and sea surface temperatures sst and surface winds in the eastern bering sea have been observed over recent years to investigate the causes of this interannual variability long term 20 30 years time series of air ocean and ice parameters from the bering sea were cross correlated with the southern oscillation index soi an index of el nino southern oscillation enso events in the tropical southern hemisphere as well as with an index of pacific north american pna events in the north pacific five to thirty percent of the interannual variability linear regression with various smoothing in the bering sea data sets with the exception of surface winds is explained by the soi when the bering sea data lags the soi for comparison 29 52 of the variability in the sst off south america can be explained by the soi the signs of the correlations all suggest that warming in the bering sea follows negative anomalies in the soi that is enso events positive anomalies in the soi which tend to precede el nino events were found to precede cooling in the bering sea significant correlation persists for 18 20 months higher order polynomial regressions between the soi and bering sea data can explain up to 40 of the bering sea variability the mechanism for the connection between enso events and bering sea interannual variability appears to be of atmospheric nature and is associated with the winter position and intensity of the aleutian low the aleutian low is intensified and eastward of normal in association with el nino i e warm events but is weaker and westward of normal during cool events it is the regional winds associated with the variable position of the aleutian low that cause the regional warming and cooling events this seesaw in the aleutian low is also used to explain the out of phase ice conditions between the bering sea and the sea of okhotsk pna events are also associated with an intensified aleutian low as well as 700 mbar ridging over northwestern north america causing southerly flow over alaska however while correlation between enso events and pna was significant the correlation between the bering sea and pna was marginal except for surface winds here surface winds from the north were significantly correlated with the pna this apparent inconsistency as well as the lack of correlation of surface winds with the soi is explained by the lack of preferred site of the aleutian low during enso events this lack of preferred site helps explain why the major el nino event of 1982 1983 had little apparent effect on the bering sea

toward a single station approach for microzonation using vertical rotation rate to estimate love wave dispersion curves and direction finding abstract microzonation the estimation of shear wave velocity profiles of the upper few 100 m in dense 2d profiles is one of the key methods for understanding the variation in seismic damage caused by ground shaking events and thus for mitigating the risk of damage in the future in this article we present a novel method for estimating the love wave phase velocity dispersion using ambient noise recordings we use the vertical component of rotational motions inherently present in ambient noise and the established relation to simultaneous recordings of transverse acceleration in which the phase velocity of a plane sh or love type wave acts as a proportionality factor we demonstrate that the developed inversion technique shows comparable results to more classical array based methods furthermore we demonstrate that if portable weak motion rotational motion sensors are available and the installation of a seismic network or array is not possible a single point multicomponent approach for estimating the dominant direction of the incident wavefield and the local velocity structure will be feasible with similar performance compared to more classical techniques

rotational motions of seismic surface waves in a laterally heterogeneous earth a number of recent studies have analyzed seismic rotational data using a relationship between transverse acceleration and rotation rate derived for a homogeneous full space in this study we explore this relationship further theoretically by presenting a full ray theory frt method to simulate rotational motions of fundamental mode seismic surface waves in smooth laterally heterogeneous earth models in the ray picture of wave propagation the vertical component of the rotational rate motion of fundamental mode love waves is obtained by dividing the transverse component of ground acceleration by the love wave local phase velocity beneath the seismic recording station we illustrate the method with examples of theoretical calculations of t 40 sec rotational rate ground motions of fundamental love waves using the crust model crust2 0 combined with the mantle model s20rts for the 25 september 2003 m 8 1 tokachi oki earthquake japan frt rotation synthetics match complete calculations using the spectral element method very well and fit real data reasonably well furthermore we show that the effect of realistic local structure beneath receivers on rotational motions is strong enough to be observable frt calculations could potentially help to determine love wave local dispersion curves and thus to estimate the 1d local shear velocity structure beneath seismic stations from point measurements of rotational rate and acceleration ground motions

inferring earth structure from combined measurements of rotational and translational ground motions we introduce a novel variant of seismic tomography that is based on colocated measurements of rotational and translational ground motions our aim is to assess whether rotations may be incorporated successfully into seismic inverse problems to produce better resolved and more realistic tomographic images our methodology is based on the definition of apparent s wave speed as the ratio of rms velocity and rotation amplitudes the principal advantages of this definition are that 1 no traveltimes measurements are needed and 2 the apparent s wave speed is independent of source magnitude and source timing we derive finite frequency kernels for apparent s wave speed by using a combination of the adjoint method and ray approximation the properties of these kernels as a function of frequency bandwidth can be illustrated along with their usefulness for seismic tomography in multifrequency synthetic inversions we consider local crosshole tomography and regional scale earthquake tomography our results indicate that s wave speed variations can be retrieved accurately from colocated rotation and translation measurements suggesting that our methodology is a promising extension of conventional seismic tomography further apparent s wave speed can be used to increase vertical resolution in teleseismic tomography for local structures

rupture of the pitaycachi fault in the 1887 mw 7 5 sonora mexico earthquake southern basin and range province rupture kinematics and epicenter inferred from rupture branching patterns during the 3 may 1887 mw 7 5 sonora earthquake surface rupture end to end length 101 8 km an array of three north south striking basin and range province faults from north to south pitaycachi teras and otates slipped sequentially along the western margin of the sierra madre occidental plateau this detailed field survey of the 1887 earthquake rupture zone along the pitaycachi fault includes mapping the rupture scarp and measurements of surface deformation the surface rupture has an endpoint to endpoint length of 41 0 km dips 70 w and is characterized by normal left lateral extension the maximum surface offset is 487 cm and the mean offset 260 cm the rupture trace shows a complex pattern of second order segmentation however this segmentation is not expressed in the 1887 along rupture surface offset profile which indicates that the secondary segments are linked at depth into a single coherent fault surface the pitaycachi surface rupture shows a well developed bipolar branching pattern suggesting that the rupture originated in its central part where the polarity of the rupture bifurcations changes most likely the rupture first propagated bilaterally along the pitaycachi fault the southern rupture front likely jumped across a step over to the teras fault and from there across a major relay zone to the otates fault branching probably resulted from the lateral propagation of the rupture after breaching the seismogenic part of the crust given that the much shorter ruptures of the otates and teras segments did not develop branches

observations of rayleigh wave phase velocity and coseismic deformation using an optical fiber interferometric vertical strainmeter at the safod borehole california we present observations from a vertical optical fiber interferometric strainmeter in the san andreas fault observatory at depth borehole near parkfield california the sensor detects both teleseismic earthquakes and local events along with coseismic strain steps consistent with theoretical dislocation models for teleseismic events we investigate the possibility of determining local rayleigh wave phase velocities beneath the borehole by comparing the ratio of vertical ground acceleration from a nearby seismometer to vertical strain while similar studies have used horizontal components and rotations this is the first such attempt utilizing vertical measurements we show that at periods from around 16 40 seconds we can recover general dispersion characteristics that are within a few percent of models of realistic local structure