the evolution of oceanic and atmospheric anomalies in the northeast pacific during the el nino and la nina events of 1995 2001 abstract from late 1995 through early 2001 three major interannual climate events occurred in the tropical pacific the 1995 97 la nina ln 1997 98 el nino en and 1998 2001 ln we analyze atmospheric and upper oceanic anomalies in the northeast pacific nep during these events and compare them to anomalies both elsewhere in the north and tropical pacific and to typical en and ln anomaly patterns the atmospheric and oceanic anomalies varied strongly on intraseasonal and interannual scales during the 1995 97 ln and 1997 98 en the northeast pacific was dominated by negative slp and cyclonic wind anomalies and by upper ocean temperature and sea surface height ssh anomalies the latter were positive along the north american west coast and in the nep thermal anomaly pool between hawaii vancouver island and baja california and negative in the central north pacific this atmospheric oceanic anomaly pattern is typical of en an eastward shift in the atmospheric teleconnection from east asia created en like anomalies in the nep during the 1995 97 ln well before the 1997 98 en had begun the persistence of negative sea level pressure slp and cyclonic wind anomalies in the nep during the 1997 98 en intensified pre existing upper oceanic anomalies atmospheric anomalies were shifted eastward during late 1996 early 1998 leading to a similar onshore shift of oceanic anomalies this produced exceptionally strong positive upper ocean temperature and ssh anomalies along the west coast during the 1997 98 en and explains the unusual coastal occurrences of several species of large pelagic warm water fishes the growth and eastward shift of these pre existing anomalies does not appear to have been linked to tropical pacific en anomalies until late 1997 when a clear atmospheric teleconnection between the two regions developed prior to this remote atmospheric impacts on the nep were primarily from east asia as the 1998 2001 ln developed nep anomalies began reversing toward the typical ln pattern this led to predominantly negative slp and cyclonic wind anomalies in the nep and upper ocean temperature and ssh anomalies that were mainly negative along the west coast and positive in the central north pacific the persistence of these anomalies into mid 2001 and a number of concurrent biological changes in the nep suggest that a decadal climate shift may have occurred in late 1998 during 1995 2001 nep oceanic anomalies tracked the overlying atmospheric anomalies as indicated by the maintenance of a characteristic spatial relationship between these anomalies in particular wind stress curl and ssh anomalies in the nep maintained an inverse relationship that strengthened and shifted eastward toward the west coast during late 1996 early 1998 this consistent relationship indicates that anomalous ekman transport driven by regional atmospheric forcing was an important contributor to temperature and ssh anomalies in the nep and ccs during the 1997 98 en other studies have shown that coastal propagations originating from the tropical pacific also may have contributed to coastal nep anomalies during this en our results indicate that at least some of this coastal anomaly signal may have been generated by regional atmospheric forcing within the nep

3 d inhomogeneities in the upper mantle abstract the method developed by aki christofferson and husebye for determining a 3 d seismic image of the earth s interior from the travel time data obtained at a 2 d array has been applied to seventeen arrays around the world by various authors the most outstanding results from these works are that small scale lateral velocity anomalies exist in the lower crust and upper mantle everywhere studied the reality of these deep seated anomalies is supported by 1 1 significant reduction of residual variance 2 2 resolution analysis for decoupling from shallower anomalies and 3 3 error analysis for the significance of anomalies in this paper we try to strengthen the credibility of these deep seated anomalies by drawing attention to those found where they were expected namely low velocity bodies under several geothermal areas and high velocity anomalies associated with the subducting plate

stress slip and earthquakes in models of complex single fault systems incorporating brittle and creep deformations numerical simulations of slip evolution along a cellular vertical strike slip fault in an elastic half space are performed for several models representing discrete fault systems embedded in three dimensional elastic continua the geometry and imposed boundary conditions correspond approximately to the central san andreas fault the simulations incorporate brittle and creep deformations in series the net fault zone deformation rate is the sum of creep rate and frictional slip rate brittle fault properties are given by various distributions of earthquake stress drops on failing segments numerical cells the assumed distributions represent two idealized situations corresponding to different extreme states along an evolutionary path of a fault 1 a strongly disordered state characterized by a wide range of size scales representing immature fault zones and extended spatial domains and 2 a relatively regular state having a narrow range of size scales representing mature highly slipped faults the assumed creep properties are identical in all cases these are prescribed in terms of coefficients characterizing a power law dependency of creep slip rate on stress the combined brittle creep process and employed parameters lead to an overall pine tree stress depth profile with a brittle ductile transition depth of about 12 5 km and variable stress along strike profiles with brittle creep transition around 65 km nw of the 1857 rupture the spatial patterns of simulated hypocenters are statistically similar to observed data the results indicate that the range of size scales characterizing strong fault zone heterogeneities has important manifestations on the seismic response of a fault system a narrow range of size scales leads to frequency size statistics of earthquakes resembling the characteristic earthquake distribution and quasi periodic temporal distribution of large events as in the seismic gap hypothesis on the other hand a wide range of size scales leads to gutenberg richter power law frequency size statistics and random or clustered temporal distribution of large events the simulations demonstrate that treatment of the various observed forms of frequency size and temporal statistics of earthquakes can be unified through the concept of range of size scales characterizing fault zone heterogeneities this has a clear physical interpretation in terms of structural properties of a given fault zone or broad lithospheric domain and is supported by observed earthquake and fault data in some simulated cases the frequency size statistics of small earthquakes fall sharply below the self similar gutenberg richter line the results indicate that small earthquakes prepare the fault for the occurrence of a large event by smoothing during gradual tectonic loading the long wavelength components of stress on the fault this is done through short wavelength stress roughening associated with the numerous ruptures of the small events the above pattern of smoothing roughening of long short wavelengths of stress on the fault is reversed during large scale ruptures of the big events

self similar earthquake triggering bath s law and foreshock aftershock magnitudes simulations theory and results for southern california 1 bath s law the observation that the largest aftershock is on average 1 2 magnitudes smaller than its main shock independent of main shock size suggests some degree of self similarity in earthquake triggering this behavior can largely be explained with triggering models in which the increased triggering caused by larger magnitude events is exactly compensated for by their decreased numbers and these models can account for many features of real seismicity catalogs the bath s law magnitude difference of 1 2 places a useful constraint on aftershock productivity in these models a more general test of triggering self similarity is to plot foreshock and aftershock rates as a function of magnitude m relative to the main shock magnitude mmax of the largest event in the sequence both computer simulations and theory show that these dn dm curves should be nearly coincident regardless of main shock magnitude the aftershock dn dm curves have the same gutenberg richter b value as the underlying distribution but the foreshock dn dm curves have the same b value only for foreshock magnitudes less than about mmax 3 for larger foreshock values the dn dm curve flattens and converges with the aftershock dn dm curve at m mmax this effect can explain observations of anomalously low b values in some foreshock sequences and the decrease in apparent aftershock to foreshock ratios for small magnitude main shocks observed apparent foreshock and aftershock dn dm curves for events close in space and time to m 2 5 to 5 5 main shocks in southern california appear roughly self similar but differ from triggering simulations is several key respects 1 the aftershock b values are significantly lower than that of the complete catalog 2 the number of aftershocks is too large to be consistent with bath s law and 3 the foreshock to aftershock ratio is too large to be consistent with bath s law these observations indicate for southern california that triggering self similarity is not obeyed for these small main shocks or that the space time clustering is not primarily caused by earthquake to earthquake triggering

variability of intraseasonal kelvin waves in the equatorial pacific ocean abstract previous observational work has demonstrated that the phase speed of oceanic equatorial kelvin waves forced by the madden julian oscillation mjo appears to vary substantially processes that are responsible for systematic changes in the phase speed of these waves are examined using an ocean general circulation model the model was integrated for 26 yr with daily wind stress derived from the ncep ncar reanalysis the model is able to reproduce observed systematic changes of kelvin wave phase speed reasonably well providing a tool for the analysis of their dynamics the relative importance of the upper ocean background state and atmospheric forcing for phase speed changes is determined based on a series of model experiments with various surface forcings systematic changes in phase speed are evident in all model experiments that have different slowly varying basic states showing that variations of the upper ocean background state are not the primary cause of the changes the model experiments t

circulation and low frequency variability near the chilean coast remotely forced fluctuations during the 1991 92 el nino results are reported from the first long recording current meter observations over the slope off chile these observations at 308s during the 1991 92 el nino event are analyzed together with observations of currents at a local deep sea site local wind and sea level sea level from the peru and chile coasts and wind temperature and currents from the equatorial pacific mean poleward flow of 12 cm s21 was observed within the peru chile undercurrent over the slope mean flow in the depth range of antarctic intermediate water was not distinguishable from zero in the presence of strong low frequency lf variability which dominated slope currents at all depths the strongest lf fluctuations had periods of about 50 days but periods of 10 and about 5 days were also observed significant local wind forcing of slope currents was only found in the period band 6 10 days and may be related to coastal trapped waves in the atmosphere our analysis shows that free coastal trapped waves in the ocean arriving from the north dominated the lf variability over the shelf and slope off northern and central chile during the 1991 92 el nino event strong 50 day period fluctuations there started their journey about two months earlier and 15 000 km farther up the coastal equatorial waveguide near the date line in the equatorial pacific as equatorial kelvin waves forced by westerly wind events of similar period upon reaching the south american coast these waves forced coastal trapped waves which propagated along the peru coast into the study region likewise a scenario of equatorial trapped waves forcing coastal trapped waves may explain 10 day as well as 6 day and 4 5 day period coastal trapped waves off chile stemming from mixed rossby gravity and inertia gravity waves trapped at the equator since the large 50 day period coastal trapped waves may strongly modify coastal upwelling source water such remotely forced waves may have a significant influence on the pelagic ecosystem off chile at least during el nino events

the tectonic crustal stress field and style of faulting along the pacific north america plate boundary in southern california we invert for the state of stress in the southern california crust using a catalogue of high quality earthquake focal mechanisms 1981 2010 the stress field is best resolved where seismicity rates are high and sufficient data are available to constrain the stress field across most of the region from the stress field we determine the maximum horizontal compressive stress s hmax orientations and the style of faulting across southern california the trend of s hmax exhibits significant regional and local spatial heterogeneities the regional trend of s hmax varies from north along the san andreas system to nne to the east in the eastern california shear zone as well as to the west within the continental borderland and the western transverse ranges the transition zones from one state of stress to the other occur over a distance of only a few kilometres following a trend from yucca valley to imperial valley to the east and the western edge of the peninsular ranges to the west the local scale heterogeneities in the s hmax trend include nnw trends along the san andreas fault near cajon pass tejon pass and the cucapah range as well as nne trends near the northern san jacinto fault and the wheeler ridge area the style of faulting exhibits similar complexity ranging from predominantly normal faulting in the high sierra nevada to strike slip faulting along the san andreas system to three consecutive bands of thrust faulting in the wheeler ridge area and the western transverse ranges the local variations in the style of faulting include normal faulting at the north end of the san jacinto fault and scattered areas of thrust faulting the regional variations in the shmax trends are very similar to the pattern of the gps measured maximum shortening axes of the surface strain rate tensor field although the strain field tends to be smoother and appears to capture some of the upper mantle deformation field the mean trend of s hmax departs about approximately 14 to the east from the trend of the maximum shortening directions derived from anisotropy in the upper mantle

sea level variations in the tropical pacific ocean and the madden julian oscillation abstract satellite observations of sea level and surface wind from the tropical pacific ocean and their relationship to the madden julian oscillation mjo are analyzed using a combination of statistical techniques and a simple physically based model wavenumber frequency analysis reveals that sea level variations at the equator contain prominent eastward propagating signals as the intraseasonal kelvin waves the component of sea level variation that is coherent with the mjo mjo is concentrated in a narrow strip along the equator between 150 e and 110 w to explain the physical forcing of mjo the component of zonal wind stress that is coherent with the mjo is also calculated it is shown that is strongest in the western pacific but the mjo accounts for a higher percentage of the wind variance in the central equatorial pacific a simple linear model of the kelvin waves based on a first order wave equation forced by and with a linear damping term included successfully reproduces mjo it is also

earthquake clusters in southern california i identification and stability 1 we use recent results on statistical analysis of seismicity to present a robust method for comprehensive detection and analysis of earthquake clusters the method is based on nearest neighbor distances of events in space time energy domain the method is applied to a 1981 2011 relocated seismicity catalog of southern california having 111 981 events with magnitudes m 2 and corresponding synthetic catalogs produced by the epidemic type aftershock sequence etas model analysis of the etas model demonstrates that the cluster detection results are accurate and stable with respect to 1 three numerical parameters of the method 2 variations of the minimal reported magnitude 3 catalog incompleteness and 4 location errors application of the method to the observed catalog separates the 111 981 examined earthquakes into 41 393 statistically significant clusters comprised of foreshocks mainshocks and aftershocks the results reproduce the essential known statistical properties of earthquake clusters which provide overall support for the proposed technique in addition systematic analysis with our method allows us to detect several new features of seismicity that include 1 existence of a significant population of single event clusters 2 existence of foreshock activity in natural seismicity that exceeds expectation based on the etas model and 3 dependence of all cluster properties except area on the magnitude difference of events from mainshocks but not on their absolute values the classification of detected clusters into several major types generally corresponding to singles burst like and swarm like sequences and correlations between different cluster types and geographic locations is addressed in a companion paper

crustal structure and seismicity distribution adjacent to the pacific and north america plate boundary in southern california new three dimensional 3 d v p and v p v s models are determined for southern california using p and s p travel times from local earthquakes and controlled sources these models confirm existing tectonic interpretations and provide new insights into the configuration of geological structures at the pacific north america plate boundary the models extend from the u s mexico border in the south to the southernmost coast ranges and sierra nevada in the north and have a 15 km horizontal grid spacing and an average vertical grid spacing of 4 km down to 22 km depth the heterogeneity of the crustal structure as imaged by v p and v p v s models is larger within the pacific plate than the north american plate similarly the relocated seismicity deepens and shows more complex 3 d distribution in areas of the pacific plate exhibiting compressional tectonics the models reflect mapped changes in the lithology across major geological terranes such as the mojave desert the peninsular ranges and the transverse ranges the interface between the shallow mono of the continental borderland and the deep moho of onshore california forms a broad zone to the north beneath the western transverse ranges ventura basin and the los angeles basin and a narrow zone to the south along the peninsular ranges the near surface increase in velocity from the surface to up to 8 km depth is rapid and has a logarithmic shape for stable blocks and mountain ranges but is slow with a linear shape for sedimentary basins at midcrustal depths a rapid increase in v p is imaged beneath the sediments of the large sedimentary basins while beneath the adjacent mountain ranges the increase is small or absent

earthquake monitoring in southern california for seventy seven years 1932 2008 the southern california seismic network scsn has produced the scsn earthquake catalog from 1932 to the present a period of more than 77 yrs this catalog consists of phase picks hypocenters and magnitudes we present the history of the scsn and the evolution of the catalog to facilitate user understanding of its limitations and strengths hypocenters and magnitudes have improved in quality with time as the number of stations has increased gradually from 7 to 400 and the data acquisition and measuring procedures have become more sophisticated the magnitude of completeness m c of the network has improved from m c 3 25 in the early years to m c 1 8 at present or better in the most densely instrumented areas mainshock aftershock and swarm sequences and scattered individual background earthquakes characterize the seismicity of more than 470 000 events the earthquake frequency size distribution has an average b value of 1 0 with m 6 0 events occurring approximately every 3 yrs the three largest earthquakes recorded were 1952 m w 7 5 kern county 1992 m w 7 3 landers and 1999 m w 7 1 hector mine sequences and the three most damaging earthquakes were the 1933 m w 6 4 long beach 1971 m w 6 7 san fernando and 1994 m w 6 7 northridge earthquakes all of these events ruptured slow slipping faults located away from the main plate boundary fault the san andreas fault their aftershock sequences constitute about a third of the events in the catalog the fast slipping southern san andreas fault is relatively quiet at the microseismic level and has not had an m 6 earthquake since 1932 in contrast the slower san jacinto fault has the highest level of seismicity including several m 6 events thus the spatial and temporal seismicity patterns exhibit a complex relationship with the plate tectonic crustal deformation

determination of stress from slip data faults and folds a new technique is derived to invert slickenside data for the stress field that caused the faulting episode this inversion is simplified by the assumption that the magnitude of the tangential traction on the various fault planes at the time of rupture is similar study of three normal faulting regimes shows that the inversion derived with this assumption yields results that closely match older inversions that did not include the assumption hence the assumption may be valid and is shown to be justified by analyzing a simple fracture criterion application of slip data inversions is extended from faulting regimes to the slip on bedding plane faults in folding regimes comparison of the inversion results with the geometry of the folds shows this application to be successful greatly increasing the number of data sets that can be used to find the paleostress field

seasonal and interannual variability in along slope oceanic properties off the us west coast inferences from a high resolution regional model a 6 year 2009 2014 simulation using a 2 km horizontal resolution ocean circulation model of the northeast pacific coast is analyzed with focus on seasonal and interannual variability in along slope subsurface oceanic properties specifically the fields are sampled on the isopycnal surface 26 5 kg m 3 that is found between depths of 150 and 300 m below the ocean surface over the continental slope the fields analyzed include the depth z26 5 temperature t26 5 along slope currents 26 5 and the average potential vorticity pv between 26 5 and 26 25 kg m 3 each field is averaged in the cross shore direction over the continental slope and presented as a function of the alongshore coordinate and time the seasonal cycle in z26 5 shows a coherent upwelling downwelling pattern from mexico to canada propagating to the north with a speed of 0 5 m s 1 the anomalously deep 20 m z26 5 displacement in spring summer 2014 is forced by the southern boundary condition at 24 n as a manifestation of an emerging strong el nino the seasonal cycle in t26 5 is most pronounced between 36 53 n indicating that subarctic waters are replaced by warmer californian waters in summer with the speed close 0 15 m s 1 which is consistent with earlier estimates of the undercurrent speed and also present 26 5 analyses the seasonal patterns and anomalies in z26 5 and t26 5 find confirmation in available long term glider and ship borne observations the pv seasonality over the slope is qualitatively different to the south and north of the southern edge of heceta bank 43 9 n

bath s law derived from the gutenberg richter law and from aftershock properties 1 the empirical bath s law states that the average difference in magnitude between a mainshock and its largest aftershock is 1 2 regardless of the mainshock magnitude following vere jones 1969 and console et al 2003 we show that the origin of bath s law is to be found in the selection procedure used to define mainshocks and aftershocks rather than in any difference in the mechanisms controlling the magnitude of the mainshock and of the aftershocks we use the etas model of seismicity which provides a more realistic model of aftershocks based on i a universal gutenberg richter gr law for all earthquakes and on ii the increase of the number of aftershocks with the mainshock magnitude using numerical simulations of the etas model we show that this model is in good agreement with bath s law in a certain range of the model parameters

dynamics of remotely forced intraseasonal oscillations off the western coast of south america abstract six years of sea level observations at six locations along the south american coast from peru to chile were analyzed at intraseasonal frequencies periodicity 1 2 months a high resolution low frequency numerical coastal model having realistic shelf and slope topography and bottom friction and forced by an equatorial signal was used to analyze the intraseasonal coastal dynamics at these latitudes the following results were obtained lagged correlations between sea level stations imply a sea level poleward propagation of 250 km day 1 the frictionless vertical wall theory poleward phase speed was considerably less at 216 km day 1 model runs with realistic bottom friction and shelf and slope bottom topography gave poleward phase speeds much closer to that observed for typical parameters the phase speed was 253 km day 1 both bottom friction and topography significantly affect the propagation speed past work has shown that the sea level amplitude should grow alongshore like f f coriolis

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

nonseasonal sea level variations in the japan east sea from satellite altimeter data 1 a merged topex poseidon and ers 1 2 altimeter data set is used to estimate nonseasonal variations of sea surface height ssh in the japan east sea jes from october 1992 through february 2002 the altimeter data have a good correlation 0 95 with tide gauge data in the western jes the nonseasonal variability of the ssh is higher in the southern warm region than in the northern cold region the root mean square value of the nonseasonal ssh is 5 10 cm in the southern area whereas it is about 4 cm in the northern area empirical orthogonal function analysis of the nonseasonal ssh shows the first mode to be related to intraseasonal oscillations over the entire jes and the second mode to interannual path variations of the tsushima warm current twc the path change of the twc is responsible for the high variability of ssh in the southern region

crustal earthquake bursts in california and japan their patterns and relation to volcanoes 1 we analyze 153 bursts of earthquakes in southern california and japan the burst patterns are similar in southern california and japan they fill a spectrum between swarm like sequences without obvious mainshocks and mainshocks with omori law abiding aftershocks in agreement with our previous work the swarm like sequences in japan have more events are more voluminous and tend to expand with time when compared to mainshock aftershock type sequences in both regions we find that the sequences starting with their largest events tend to be much shorter in duration bursts within 50 km of volcanoes are similar in character to those elsewhere except they tend to have longer duration we hypothesize that swarminess is a proxy for fluid pressure redistribution and or aseismic slip driving the seismicity bursts and conversely the mainshock aftershock style sequences have end member behavior that results solely from a cascade of elastic failures the complexity of the spatial seismicity distribution does not correlate with the style of swarm observed indicating that fluid conditions and composition are likely more influential than geometry in determining the patterns we observe

subtidal sea level fluctuations in a large fjord system a cross spectral analysis is made of subtidal 0 01 0 5 cpd sea level ssl atmospheric pressure and wind fluctuations observed during 1966 1988 in the southern reaches of the fjord system formed by the straits of juan de fuca georgia and puget sound it shows that observed ssl can be largely explained by quasi steady inverse barometer compensation to atmospheric pressure and the propagation of adjusted sea level fluctuations from the nearby continental shelf with some local weather forcing in summer variations in coherence amplitudes and relative phase between seasons locations and frequencies support previous work that both barotropic and baroclinic processes have important influences in ssl within the fjord system

the association of the evolution of intraseasonal oscillations to enso phase abstract the pacific ocean intraseasonal kelvin wave is a leading oceanic mode that links intraseasonal tropical atmospheric variations with interannual variations in the coupled ocean atmosphere system this study considers the premise that these waves may evolve differently with their associated weather patterns during different phases of el nino southern oscillation enso if atmospheric and oceanic intraseasonal modes interact and evolve differently during various stages of enso this result may provide useful information with regard to the role of these intraseasonal processes in enso evolution this work utilizes signals of the oceanic kelvin wave as a statistical basis for a simple composite averaging technique that is applied during different phases of enso to objectively analyze the evolution of oceanic and the associated portions of atmospheric intraseasonal oscillations results confirm the above premise and suggest that coupling between kelvin waves and atmospheric convection evolves differen

effect of coastal trapped waves and wind on currents and transport in the gulf of california subsurface pressure ssp observations from stations inside and outside of the gulf of california gc are used to analyze the relationship between low frequency currents temperature and transport inside the gc and intraseasonal coastal trapped waves ctws which propagate poleward along the coast toward the gc correlation functions and coherences of ssp stations were consistent with intraseasonal ctws splitting in two at the mouth of the gulf one part enters the gulf propagates around the gulf and eventually toward the mouth and another part that appears to jump the mouth of the gulf and travels poleward along the west coast of the peninsula the correlation and coherence estimates of ssp at manzanillo with currents showed that downwelling ctws generated along gulf current anomalies toward the head of the gulf at the mainland shelf of the mouth whereas at ballenas channel sill san lorenzo sill these waves generated current anomalies toward the mouth near the surface bottom at the san lorenzo sl sill downwelling ctws increased the near bottom 400 m temperature and reduced the bottom transport of deep fresher and colder water that flows toward the head of the gulf cross calibrated multiplatform winds were used to investigate their relationship with currents the first empirical orthogonal function of the along gulf wind stress showed that wind blowing toward the head of the gulf generated a reduction of bottom transport toward the head of the gulf through the sl sill and intensified surface geostrophic current fluctuations toward the head of the gulf there was also significant correlation between inflow bottom transport and outflow surface geostrophic velocities averaged across the gulf consistent with the exchange pattern for the northern gulf

properties of aftershock sequences in southern california the temporal behavior of 39 aftershock sequences in southern california 1933 1988 was modeled by the modified omori relation minimum magnitudes for completeness of each sequence catalog were determined and the maximum likelihood estimates of the parameters k p and c with the standard errors on each were determined by the ogata algorithm the b value of each sequence was also calculated many of the active faults in the region both strike slip and thrust were sampled the p values were graded in terms of the size of the standard error relative to the p value itself most of the sequences were modeled well by the omori relation many of the sequences had p values close to the mean of the whole data set 1 11 0 25 but values significantly different from the mean as low as 0 7 and as high as 1 8 exist no correlation of p with either the b value of the sequence or the mainshock magnitude was found the results suggest a direct correlation of p values is with surface heat flow with high values in the salton trough high heat flow and one low value in the san bernardino mountains and on the edge of the ventura basin both low heat flow the large fraction of the sequences with p values near the mean are at locations where the heat flow is near the regional mean 74 mw m2 if the hypothesis that aftershock decay rate is controlled by temperature at depth is valid the effects of other factors such as heterogeneity of the fault zone properties are superimposed on the background rate determined by temperature surface heat flow is taken as an indicator of crustal temperature at hypocentral depths but the effects on heat flow of convective heat transport and variations in near surface thermal conductivity invalidate any simple association of local variations in heat flow with details of the subsurface temperature distribution the interpretation is that higher temperatures in the aftershock source volume caused shortened stress relaxation times in the fault zone materials leading to a faster decay rate higher p value in 1967 mogi proposed such a relation on the basis of japanese data seismic velocity distributions published for southern california generally support the hypothesis with low velocities higher temperatures corresponding to high p values and vice versa

geodetic slip rates in the southern san andreas fault system effects of elastic heterogeneity and fault geometry 1 we use high resolution interferometric synthetic aperture radar and gps measurements of crustal motion across the southern san andreas fault system to investigate the effects of elastic heterogeneity and fault geometry on inferred slip rates and locking depths geodetically measured strain rates are asymmetric with respect to the mapped traces of both the southern san andreas and san jacinto faults two possibilities have been proposed to explain this observation large contrasts in crustal rigidity across the faults or an alternate fault geometry such as a dipping san andreas fault or a blind segment of the san jacinto fault we evaluate these possibilities using a two dimensional elastic model accounting for heterogeneous structure computed from the southern california earthquake center crustal velocity model cvm h 6 3 the results demonstrate that moderate variations in elastic properties of the crust do not produce a significant strain rate asymmetry and have only a minor effect on the inferred slip rates however we find that small changes in the location of faults at depth can strongly impact the results our preferred model includes a san andreas fault dipping northeast at 60 and two active branches of the san jacinto fault zone in this case we infer nearly equal slip rates of 18 1 and 19 2mm yr for the san andreas and san jacinto fault zones respectively these values are in good agreement with geologic measurements representing average slip rates over the last 10 10 years implying steady long term motion on these faults

exchange of momentum among atmosphere ocean and solid earth associated with the madden julian oscillation we investigate coherences among time series of tropical zonal winds total atmospheric angular momentum m the length of day of earth rotation lod and near equatorial sea level all of which exhibit a broad intraseasonal spectral density peak we seek to ascertain how the wavy eastward propagating 40 50 day or madden julian oscillation mjo in near equatorial zonal winds is related to intraseasonal fluctuations of the zonally averaged zonal wind in the tropics u and global momentum m it is found that 40 50 day upper tropospheric zonal wind fluctuations at western pacific stations where the mjo signal is pronounced are mostly incoherent with fluctuations of m and u in the tropics but lower tropospheric fluctuations at the same stations are significantly coherent the observed phase lags between variations of near surface wind and m are consistent with the hypothesis that fluctuations of surface stress on the pacific ocean associated with the mjo are the primary agent for deposition and removal of momentum into and out of the atmosphere we then examine whether equatorial sea level variability at the south american coast represents a continental torque coupling the ocean and solid earth on the 40 50 day time scale thereby accounting for the high coherence observed between m and lod coherence between sea level and lod is not significant however suggesting that oceanic baroclinic wave activity which is the primary cause of 40 50 day sea level fluctuations does not contribute significantly to the exchange of momentum between the ocean and solid earth on the other hand the results support the conjecture that barotropic ocean waves provide the required transport and exchange of momentum and the potential importance of such waves is briefly discussed

application of wavelet transform in the study of coastal trapped waves off the west coast of south america 1 wavelet transform and cross wavelet transform were applied for analyzing long time series of sea level and alongshore wind stress to identify intraseasonal variability off western south america and the relations with remote and local forcings hydrographic data were used to estimate properties of coastal trapped waves with a theoretical model for el nino years we found the existence of intraseasonal oscillations with periods 20 90 days between 2s and 27s at the peak of 91 92 and 97 98 el ninos we found perturbations in the northern region probably associated with remotely forced internal kelvin waves with periods 6 11 days and phase velocities 160 260 km day between 12s and 15s during two el nino events our calculations show perturbations which appear to be barotropic shelf waves propagating southward with velocities between 110 and 150 km day and periods between 30 and 50 days

local and remote forcing of sea surface temperature in the coastal upwelling system off chile an analysis is presented of records of sea surface temperature sst sea level and winds collected during the period 1991 1995 along the coast of northern and central chile sea level also from the peru coast in 1991 1994 and of sst from remote sensing during the austral summers of 1991 and 1992 off northern chile large interannual fluctuations of sst and sea level off northern chile are linked to vertical displacements of the equatorial thermocline during el nino la nina events in the intraseasonal 50 day band sst and sea level are intimately related all along the coast whereby sst anomalies lag sea level perturbations by about 12 days such sea level fluctuations are due to free coastal trapped waves ultimately forced via equatorial kelvin waves by 50 day wind events in the western and central tropical pacific these results and those of the remote sensing analysis suggest significant remote forcing of sst fluctuations in the coastal zone off chile by the action of the coastal trapped waves off central chile sst is also related to local wind stress in the intraseasonal band simulations with a simple local wind driven upwelling entrainment model capture rather well observed synoptic and intraseasonal oscillations of sst there off northern chile however this simple model is not successful in simulating observed sst an attempt to include effects of coastal trapped waves into this simple one dimensional model did not improve model fit to data at either location an explanation for the apparent strong influence of these waves on sst along this coast should therefore be sought in other effects not considered by this model such as cross shelf and alongshore advection

25 day period large scale oscillations in the argentine basin revealed by the topex poseidon altimeter the measurement of the global sea surface height made by the topex poseidon satellite has provided the first synoptic view of large scale oceanic variability at intraseasonal scales from weeks to months areas of significant intraseasonal variability were found primarily in the tropics and the high latitude oceans the southern ocean in particular the focus of the paper is the finding of large scale oscillations at a period of 25 days in the argentine basin of the south atlantic ocean these oscillations exhibit a dipole pattern of counterclockwise rotational propagation centered at 458s 3178e over the zapiola rise the scale of the dipole is about 1000 km the peak to trough amplitude is on the order of 10 cm the amplitude of these oscillations has large seasonalto interannual variations these oscillations are shown to be associated with a free barotropic mode of the basin as a solution to a linearized barotropic vorticity equation closed f h contours provide a mechanism for the confinement of the waves to the topographic feature of the zapiola rise results from a numerical model simulation reproduced the patterns of the observed oscillations the resultant mass transport variability is on the order of 50 sv sv 106 m3 s21 deep current meters in the argentine basin reveal signals consistent with the altimetry observations

spatiotemporal patterns in the energy release of great earthquakes for the past 80 years the energy released in great strike slip and thrust earthquakes has occurred in alternating cycles of 20 to 30 years this pattern suggests that a global transfer mechanism from poloidal to toroidal components of tectonic plate motions is operating on time scales of several decades the increase in seismic activity in california in recent years may be related to an acceleration of global strike slip moment release as regions of shear deformation mature after being reached by stresses that have propagated away from regions of great subduction decoupling earthquakes in the 1960s

the intraseasonal oscillation in eastern pacific sea levels how is it forced abstract daily sea level and surface winds at eastern pacific shore locations and equatorial islands together with gridded five day averages of 850 mb winds have been analyzed for the 1979 84 period to determine how the 40 60 day intraseasonal oscillation of eastern pacific sea levels is forced as described by spillane et al for 1971 75 the oscillation was also present in 1980 84 from callao peru to san francisco with maximum energy near 52 57 days and band limits of 43 and 65 days during 1980 84 there was no evidence for forcing of the large scale oscillation in the eastern pacific although a local contribution of forcing was superimposed on the remote signal at the california stations interannual fluctuations in amplitude were evident in the sea level time series consistent with those of the corresponding wind oscillation in the western equatorial pacific the oscillation was best developed in both variables in 1980 82 and became weak or nonexistent during the recovery phase of the 1982 83 e

influence of oceanic intraseasonal kelvin waves on eastern pacific hurricane activity abstractrecent studies have highlighted the role of subsurface ocean dynamics in modulating eastern pacific epac hurricane activity on interannual time scales in particular the well known el nino southern oscillation enso recharge discharge mechanism has been suggested to provide a good understanding of the year to year variability of hurricane activity in this region this paper investigates the influence of equatorial subsurface subannual and intraseasonal oceanic variability on tropical cyclone tc activity in the epac that is to say it examines previously unexplored time scales shorter than interannual in an attempt to explain the variability not related to enso using ocean reanalysis products and tc best track archive the role of subannual and intraseasonal equatorial kelvin waves ekw in modulating hurricane intensity in the epac is examined it is shown first that these planetary waves have a clear control on the subannual and intraseasonal variability of thermocline depth in the epac

cross shore transport variability in the california current ekman upwelling vs eddy dynamics abstract the low frequency dynamics of coastal upwelling and cross shelf transport in the central and southern california current system ccs are investigated using the regional ocean modeling system roms over the period 1965 2008 an ensemble of passive tracers released in the numerical model is used to characterize the effects of linear ekman upwelling and non linear mesoscale eddies circulation dynamics on the statistics of advection of coastal waters the statistics of passive tracers released in the subsurface show that the low frequency variability of coastal upwelling and cross shelf transport of the upwelled water mass are strongly correlated with the alongshore wind stress and are coherent between the central and southern ccs however the offshore transport of tracers released at the surface is not coherent between the two regions and is modulated by intrinsic mesoscale eddy activity in particular cyclonic eddies the transport of cyclonic eddies extends with depth and entrains water masses of southern origin advected by the poleward california undercurrent cuc the cuc water masses are not only entrained by eddies but also constitute a source for the central california upwelling system the interplay between intrinsic eddy activity and deterministic ekman upwelling dynamics in controlling the cross shelf exchanges in the ccs may provide an improved framework to understand and interpret nutrients and ecosystem variability

the madden julian oscillation and the angular momentum balance in a barotropic ocean model surface wind stresses associated with the madden julian oscillation transfer angular momentum between the atmosphere and the underlying ocean the resulting anomalies in oceanic angular momentum related to either changes in zonal currents or latitudinal redistribution of mass and the torques coupling the ocean and the solid earth are examined for simple zonal stress patterns representing idealized 40 to 50 day fluctuations of pacific winds because the contribution of baroclinic variability to the angular momentum budget is in general small when vertically integrated quantities are considered ponte 1990 only the barotropic response is studied numerical solutions of the shallow water equations with linear bottom friction are found for a constant depth basin centered on the equator and extending over 140 in longitude the angular momentum exchanges between the ocean and solid earth in the model involve the continental torque i e body forces on eastern and western walls due to coastal sea level anomalies and the bottom friction torque solutions yield a dominant balance between the wind and continental torques with the bottom friction torque being negligible the amplitude of the total torque acting on the ocean and the corresponding angular momentum fluctuations are very small compared with the amplitude of the applied wind torque the ocean delivers to the solid earth with no significant time delays the angular momentum anomalies received from the atmosphere in general sea level anomalies are nearly uniform along the eastern boundary and the respective meridionally integrated torque is much larger than the one exerted on the western wall solutions also suggest that coastal barotropic sea level fluctuations as small as 0 5 1 5 cm are sufficient to cause variations in the length of day comparable to observed values in the 40 to 50 day band

the source of 90 day oscillations at wake island energetic 90 day oscillations of sea level have been intermittently observed at wake island in the western tropical pacific during the past 2 decades the oscillations tend to occur about 1 5 years after el nino southern oscillation events to have amplitudes of 10 15 cm and to persist for about 1 year sea surface heights from the geosat altimeter are used to establish that these signals take the form of rossby waves and have an energy source near the big island of hawaii which lies 40 of longitude to the east sea level and upper layer currents from an eddy resolving numerical model are examined and suggest that the energy source is eddies generated off the big island of hawaii these eddies appear to be associated with westward currents that intermittently impinge on the island several alternate hypotheses are also discussed and rejected

revisiting mjo kelvin waves and el nino relationships using a simple ocean model mechanisms governing interactions between the madden julian oscillation mjo kelvin wave activity and el nino development are reexamined using the oceanic component of the zebiak cane zcocn model of the pacific basin prescribed wind stress from a free run of the super parameterized community climate system model version 4 sp ccsm4 is used to force zcocn and the simulated el nino events are analyzed with respect to their relationship with the mjo wind forcing composites of el nino events strongly influenced by the mjo show the earlier onset of a flattened el nino like state of the thermocline in contrast the composites of el nino events not influenced by the mjo winds show a later onset and are dominated by a transient like thermocline along with periods of upwelling kelvin wave activity sensitivity experiments performed to identify whether modifying mjo wind stress and oceanic kelvin wave activity influences these features show that although mjo contributes to the development of these features it is not necessarily the primary driver the relative phasing between mjo and oceanic kelvin wave activity seems to be the most important factor governing the influence of mjo on el nino when in phase and collocated with kelvin wave activity mjo westerly wind stress contributes to the amplification of preexisting downwelling kelvin waves leading to earlier onset and greater strength of the resulting el nino events the out of phase interactions between mjo and oceanic kelvin waves explain the observed lack of influence of mjo onto some el nino events

equatorially forced intraseasonal propagations along the peru chile coast and their relation with the nearshore eddy activity in 1992 2000 a modeling study 1 a regional eddy resolving oceanic model spanning the 1992 2000 period is used to study the influence of 50 to 80 day intraseasonal equatorial kelvin waves iekw on mesoscale eddy activity off the west coast of peru and northern and central chile the model is shown to realistically simulate nearshore intraseasonal sea level variability poleward propagation of equatorially forced coastal trapped waves along the coastal waveguide and offshore variability related to mesoscale eddies and rossby waves rw in agreement with linear theory rw are confined equatorward of 12 s in the 50 80 days period range south of that critical latitude westward propagation is dominated by energetic mesoscale signals resulting mainly from coastal flow instability sensitivity experiments to the open boundary conditions are then used to estimate to what extent eddy activity is impacted by the remote equatorial forcing a coastal increase in eddy kinetic energy related to the energetic 60 day iekw activity present in the open boundary forcing is evidenced and is largest off northern peru whereas no major changes are observed offshore additional regional simulations with different open boundary conditions corroborate our findings and suggest that this limited effect of iekw on the offshore eddy kinetic energy may be a robust feature citation belmadani a v echevin b dewitte and f colas 2012 equatorially forced intraseasonal propagations along the peru chile coast and their relation with the nearshore eddy activity in 1992 2000 a modeling study j geophys res 117 c04025 doi 10 1029 2011jc007848

comparison of etas parameter estimates across different global tectonic zones abstract branching point process models such as the epidemic type aftershock sequence etas models introduced by ogata 1988 1998 are often used in the description characterization simulation and declustering of modern earthquake catalogs the present work investigates how the parameters in these models vary across different tectonic zones after considering divisions of the surface of the earth into several zones based on the plate boundary model of bird 2003 etas models are fit to the occurrence times and locations of shallow earthquakes within each zone computationally the expectation maximization em type algorithm of veen and schoenberg 2008 is employed for the purpose of model fitting the fits and variations in parameter estimates for distinct zones are compared and seismological implications are discussed in particular we find that estimated background seismicity rates range by a factor of nearly 500 for interplate and trench events respectively the estimated productivity parameter governing the relationship between the magnitude of an earthquake and its expected number of direct aftershocks ranges by a factor of more than five from events in the slow moving zone to events in active continental areas suggesting a much higher rate of swarming in the ridges than in the trenches and active continental zones despite the pronounced differences between the seismicity patterns and parameter estimates in the different zones the etas model with few parameters and with the same functional form seems to fit reasonably well to the seismicity in each zone

observed relationships between oceanic kelvin waves and atmospheric forcing abstract the madden julian oscillation mjo has been implicated as a major source of the wind stress variability that generates basin scale kelvin waves in the equatorial pacific one source of debate concerning this relationship is the apparent difference in the frequencies of the two processes this work utilizes data from the tropical atmosphere ocean tao array of moored buoys along with outgoing longwave radiation data to show by means of a multiple linear regression model and case studies that the frequency discrepancy is due to a systematic decrease in the phase speeds of the kelvin waves and an increase in the period of the waves toward the east as conditions adjust toward el nino among the potential contributing factors to this phase speed decrease is an apparent air sea interaction that enhances the wind forcing of some of the kelvin waves allowing them to continue to amplify because the propagating wind stress anomaly decelerates to the speed of the developing kelvin wave instead of the sig

accelerated seismic release and related aspects of seismicity patterns on earthquake faults observational studies indicate that large earthquakes are sometimes preceded by phases of accelerated seismic release asr characterized by cumulative benioff strain following a power law timeto failure relation with a term tf t m where tr is the failure time of the large event and observed values of m are close to 0 3 we discuss properties of asr and related aspects of seismicity patterns associated with several theoretical frameworks the subcritical crack growth approach developed to describe deformation on a crack prior to the occurrence of dynamic rupture predicts great variability and low asymptotic values of the exponent m that are not compatible with observed asr phases statistical physics studies assuming that system size failures in a deforming region correspond to critical phase transitions predict establishment of long range correlations of dynamic variables and power law statistics before large events using stress and earthquake histories simulated by the model of ben zion 1996 for a discrete fault with quenched heterogeneities in a 3 d elastic half space we show that large model earthquakes are associated with nonrepeating cyclical establishment and destruction of long range stress correlations accompanied by nonstationary cumulative benioff strain release we then analyze results associated with a regional lithospheric model consisting of a seismogenic upper crust governed by the damage rheology of lyakhovsky et al 39 over a viscoelastic substrate we demonstrate analytically for a simplified 1 d case that the employed damage rheology leads to a singular power law equation for strain proportional to t f t 1 3 and a nonsingular power law relation for cumulative benioff strain proportional to t f t 1 3 a simple approximate generalization of the latter for regional cumulative benioff strain is obtained by adding to the result a linear function of time representing a stationary background release to go beyond the analytical expectations we examine results generated by various realizations of the regional lithospheric model producing seismicity following the characteristic frequency size statistics gutenberg richter power law distribution and mode switching activity we find that phases of asr exist only when the seismicity preceding a given large event has broad frequency size statistics in such cases the simulated asr phases can be fitted well by the singular analytical relation with m 1 3 the nonsingular equation with m 0 2 and the generalized version of the latter including a linear term with m 1 3 the obtained good fits with all three relations highlight the difficulty of deriving reliable information on functional forms and parameter values from such data sets the activation process in the simulated asr phases is found to be accommodated both by increasing rates of moderate events and increasing average event size with the former starting a few years earlier than the latter the lack of asr in portions of the seismicity not having broad frequency size statistics may explain why some large earthquakes are preceded by asr and other are not the results suggest that observations of moderate and large events contain two complementary end member predictive signals on the time of future large earthquakes in portions of seismicity following the characteristic earthquake distribution such information exists directly in the associated quasi periodic temporal distribution of large events in portions of seismicity having broad frequency size statistics withrandom or clustered temporal distribution of large events the asr phases have predictive information the extent to which natural seismicity may be understood in terms of these end member cases remains to be clarified continuing studies of evolving stress and other dynamic variables in model calculations combined with advanced analyses of simulated and observed seismicity patterns may lead to improvements in existing forecasting strategies

are aftershocks of large californian earthquakes diffusing we analyze 21 aftershock sequences of california to test for evidence of space time diffusion aftershock diffusion may result from stress diffusion and is also predicted by any mechanism of stress weakening here we test an alternative mechanism to explain aftershock diffusion based on multiple cascades of triggering in order to characterize aftershock diffusion we develop two methods one based on a suitable time and space windowing the other using a wavelet transform adapted to the removal of background seismicity both methods confirm that diffusion of seismic activity is very weak much weaker than reported in previous studies a possible mechanism explaining the weakness of observed diffusion is the effect of geometry including the localization of aftershocks on a fractal fault network and the impact of extended rupture lengths which control the typical distances of interaction between earthquakes

indications for a successively triggered rupture growth underlying the 2000 earthquake swarm in vogtland nw bohemia 1 the characteristics of earthquake swarms can neither be described by simple laws nor are the underlying mechanisms presently understood swarm activity is often assumed to be caused by an intrusion of fluids into the seismogenic zone we have studied the earthquake catalog of the large earthquake swarm that occurred in the year 2000 in vogtland se germany and nw bohemia an area well known for its episodic swarm generation we observe a significant decrease of the gutenberg richter b value during the swarm evolution as well as a fractal temporal clustering of the earthquakes the spatial spreading of the swarm s activity which is approximately confined to one plane cannot simply be explained by a process of fluid diffusion instead we observe a simple relationship between the spatial spreading and the seismic moment release which is in good agreement with empirical relationships derived for tectonically driven earthquakes and theoretical crack growth models this observation points to a progressively growing main fracture underlying the swarm activity in addition we find that the swarm earthquakes themselves trigger aftershocks near the border of their rupture area the stick slip behavior of the rupture propagation can be explained by stress transfers and induced fluid flows due to earthquakes in a fluid permeated critically loaded fault zone however during the first phase the temporal behavior is found to be different pointing to intrusion of fluids initiating the swarm activity

slow growing and extended duration seismicity swarms reactivating joints or foliations in the cahuilla valley pluton central peninsular ranges southern california three prolific earthquake swarms and numerous smaller ones have occurred since 1980 in the mesozoic igneous plutonic rocks of the perris block of the peninsular ranges southern california the major swarms occurred in 1980 1981 1983 1984 and 2016 2018 with the latest swarm still ongoing these swarms have no clear mainshock with the largest events of m l 3 6 m l 3 7 and m w 4 4 each successive swarm had larger cumulative seismic moment release with about 314 and 411 events of m 1 5 while the third swarm has produced about 451 events of m 1 5 as of september 2018 the concurrent strike slip faulting occurred on north to northwest striking planes but with no orthogonal northeast trending seismicity alignments these shallow swarms are probably driven by intrablock pacific north america plate boundary stress loading of the two bounding major late quaternary strike slip faults the elsinore and san jacinto faults the state of stress within the cahuilla valley pluton has a 40 angle between the maximum principal stress and the average trend of the swarms suggesting that migrating pore fluid pressures aid in the formation and growth of zones of weakness these swarms which last more than 600 days each exhibit clear bilateral spatial migration for distances of up to 7 8 km and reach their full length in about 20 months the slow spatial temporal development of the swarms corresponds to a fluid diffusivity of 0 006 to 0 01 m2 s consistent with very low permeability rocks as expected for this block there is no geodetic or other evidence for a slow slip event driving the swarms

attenuation models qp and qs in three dimensions of the southern california crust inferred fluid saturation at seismogenic depths we analyze high dynamic range waveform spectra to determine t values for both p and s waves from earthquakes in southern california we invert the t values for three dimensional 3 d frequency independent q p and q s regional models of the crust the models have 15 km horizontal grid spacing and an average vertical grid spacing of 4 km down to 22 km depth and extend from the u s mexico border to the coast ranges in the south and sierra nevada in the north in general qp and qs increase rapidly with depth consistent with crustal densities and velocities the 3 d q p and q s models image the major tectonic structures and to a much lesser extent the thermal structure of the southern california crust the near surface low q p and q s zones coincide with major sedimentary basins such as the san bernardino chino san gabriel valley los angeles ventura and santa maria basins and the salton trough in contrast at shallow depths beneath the peninsular ranges southern mojave desert and southern sierras we image high q p and q s zones which correspond to the dense and high velocity rocks of the mountain ranges several clear transition zones of rapidly varying q p and q s coincide with major late quaternary faults and connect regions of high and low q p and q s at midcrustal depths the q p and q s exhibit modest variation in slightly higher and lower qp or qs zones which is consistent with reported crustal reflectivity in general for the southern california crust q s q p is greater than 1 0 suggesting partially fluid saturated crust a few limited regions of q s q p less than 1 0 correspond to areas mostly outside the major sedimentary basins including areas around the san jacinto fault suggesting a larger reduction in the shear modulus compared to the bulk modulus or almost complete fluid saturation

the rio tinto basin spain mineralogy sedimentary geobiology and implications for interpretation of outcrop rocks at meridiani planum mars abstract exploration by the nasa rover opportunity has revealed sulfate and hematite rich sedimentary rocks exposed in craters and other surface features of meridiani planum mars modern holocene and plio pleistocene deposits of the rio tinto southwestern spain provide at least a partial environmental analog to meridiani planum rocks facilitating our understanding of meridiani mineral precipitation and diagenesis while informing considerations of martian astrobiology oxidation thought to be biologically mediated of pyritic ore bodies by groundwaters in the source area of the rio tinto generates headwaters enriched in sulfuric acid and ferric iron seasonal evaporation of river water drives precipitation of hydronium jarosite and schwertmannite while mg al fe3 copiapite coquimbite gypsum and other sulfate minerals precipitate nearby as efflorescences where locally variable source waters are brought to the surface by capillary action during the wet season hydrolysis of sulfate salts results in the precipitation of nanophase goethite holocene and plio pleistocene terraces show increasing goethite crystallinity and then replacement of goethite with hematite through time hematite in meridiani spherules also formed during diagenesis although whether these replaced precursor goethite or precipitated directly from groundwaters is not known the retention of jarosite and other soluble sulfate salts suggests that water limited the diagenesis of meridiani rocks diverse prokaryotic and eukaryotic microorganisms inhabit acidic and seasonally dry rio tinto environments organic matter does not persist in rio tinto sediments but biosignatures imparted to sedimentary rocks as macroscopic textures of coated microbial streamers surface blisters formed by biogenic gas and microfossils preserved as casts and molds in iron oxides help to shape strategies for astrobiological investigation of meridiani outcrops

thermal mechanical controls on seismicity depth distributions in the san andreas fault zone earthquake depth distributions in continental crust can be related to factors which determine the depth of the transition from brittle to ductile failure these factors include temperature strain rate and lithology the san andreas fault zone of northern and central california is an ideal place to test the relative importance of these factors since there is abundant earthquake data and our understanding of the tectonic interaction of the pacific and north american plates provides constraints for several parameters in the san andreas fault zone we have found an approximately 3 km increase from northern to central california of the median depth of events and the depth above which 90 of events occur in addition depth distributions of earthquakes vary systematically from northern to central california both the maximum depth of earthquakes and the depth of the peak of seismic activity are shallower in northern california utilizing critical strength envelopes we have found that unlike the oceanic case this variation is not thermally controlled rather a combination of low strain rate and low stress level cause the seismicity in northern california to be shallow relative to central california

observations of the dispersion characteristics and meridional sea level structure of equatorial waves in the pacific ocean spectral techniques applied to altimetry data are used to examine the dispersion relation and meridional sea level structure of wavelike variability with periods of about 20 to 200 days in the equatorial pacific ocean zonal wavenumber frequency power spectra of sea surface height when averaged over about 7 s 7 n exhibit spectral peaks near the theoretical dispersion curves of first baroclinic mode equatorial kelvin and rossby waves there are distinct statistically significant ridges of power near the first and second meridional mode rossby wave dispersion curves sea level variability near the theoretical kelvin wave and first meridional mode rossby wave dispersion curves is dominantly but not perfectly symmetric about the equator while variability near the theoretical second meridional mode rossby wave dispersion curve is dominantly antisymmetric these results are qualitatively consistent with expectations from classical or shear modified theories of equatorial waves the meridional structures of these modes resemble the meridional modes of equatorial wave theory but there are some robust features of the meridional profiles that were not anticipated the meridional sea level structure in the intraseasonal kelvin wave band closely resembles the theoretically expected gaussian profile but sea level variability coherent with that at the equator is detected as far away as 11 75 s possibly as a result of the forced nature of these kelvin waves both first and second meridional mode rossby waves have larger amplitude in the northern hemisphere the meridional sea level structure of tropical instability waves closely resembles that predicted by lyman et al using a model linearized about a realistic equatorial zonal current system

comprehensive analysis of earthquake source spectra in southern california we compute and analyze p wave spectra from earthquakes in southern california between 1989 and 2001 using a method that isolates source receiver and path dependent terms we correct observed source spectra for attenuation using both fixed and spatially varying empirical green s function methods estimated brune type stress drops for over 60 000 m l 1 5 to 3 1 earthquakes range from 0 2 to 20 mpa with no dependence on moment or local b value median computed stress drop increases with depth in the upper crust from about 0 6 mpa at the surface to about 2 2 mpa at 8 km where it levels off and remains nearly constant in the midcrust down to about 20 km however the results at shallow depths could also be explained as reduced rupture velocities near the surface rather than a change in stress drop spatially coherent variations in median stress drop are observed with generally low values for the imperial valley and northridge aftershocks and higher values for the eastern transverse ranges and the north end of the san jacinto fault we find no correlation between observed stress drop and distance from the san andreas and other major faults significant along strike variations in stress drop exist for aftershocks of the 1992 landers earthquake which may correlate with differences in main shock slip

variability in the eastern equatorial pacific ocean during 1986 1988 we examine variability in the eastern equatorial pacific during 1986 1988 using conductivity temperature depth data velocity and temperature data from equatorial moorings between 110 w and 140 w and wind data from a basin scale zonal array of islands and moorings between 110 w and 165 e the period studied coincides with the el nino southern oscillation enso event of 1986 1987 and a subsequent cold event in 1988 weak warm sea surface temperature anomalies first appeared in the eastern equatorial pacific in mid 1986 and increased to 1 c in september november 1986 in association with a 30 cm s 1 weakening of the south equatorial current and a 20 to 40 m depression of the thermocline these warm anomalies lasted until early 1988 after which a large scale shoaling of the thermocline led to sea surface temperatures more than 3 c colder than climatology year to year fluctuations in the eastern pacific were related primarily to zonal wind variations in the central and western pacific westerly wind stress anomalies of 0 02 0 05 n m 2 were observed between 140 w and 165 e from the latter half of 1986 until the end of 1987 these were replaced by easterly wind anomalies of similar magnitude between 157 w and 165 e in 1988 energetic intraseasonal fluctuations with periods of 2 3 months were also prominent in zonal current temperature and dynamic height time series these fluctuations propagate eastward at approximately first baroclinic mode kelvin wave phase speeds and are forced west of the date line by episodes of westerly winds extrema in several oceanic variables occurred in association with these waves though their precise dynamical link to the enso cycle is unclear from our data sea surface temperature and thermocline depth anomalies at 0 110 w were less pronounced during the 1986 87 enso than during the 1982 1983 enso the equatorial undercurrent though weaker than normal in early 1987 did not disappear as it did in early 1983

mainshocks are aftershocks of conditional foreshocks how do foreshock statistical properties emerge from aftershock laws 1 the inverse omori law for foreshocks discovered in the 1970s states that the rate of earthquakes prior to a mainshock increases on average as a power law 1 tc t p of the time to the mainshock occurring at tc here we show that this law results from the direct omori law for aftershocks describing the power law decay 1 t tc p of seismicity after an earthquake provided that any earthquake can trigger its suit of aftershocks in this picture the seismic activity at any time is the sum of the spontaneous tectonic loading and of the activity triggered by all preceding events weighted by their corresponding omori law the inverse omori law then emerges as the expected in a statistical sense trajectory of seismicity conditioned on the fact that it leads to the burst of seismic activity accompanying the mainshock in particular we predict and verify by numerical simulations on the epidemic type aftershock sequence etas model that p is always smaller than or equal to p and a function of p of the b value of the gutenberg richter law gr and of a parameter quantifying the number of direct aftershocks as a function of the magnitude of the mainshock the often documented apparent decrease of the b value of the gr law at the approach to the mainshock results straightforwardly from the conditioning of the path of seismic activity culminating at the mainshock however we predict that the gr law is not modified simply by a change of b value but that a more accurate statement is that the gr law gets an additive or deviatoric power law contribution with exponent smaller than b and with an amplitude growing as a power law of the time to the mainshock in the space domain we predict that the phenomenon of aftershock diffusion must have its mirror process reflected into an inward migration of foreshocks toward the mainshock in this model foreshock sequences are special aftershock sequences which are modified by the condition to end up in a burst of seismicity associated with the mainshock foreshocks are not just statistical creatures but are genuine forerunners of large shocks as shown by the large prediction gains obtained using several of their qualifiers

the 2003 2004 seismic swarm in the western corinth rift evidence for a multiscale pore pressure diffusion process along a permeable fault system microseismic multiplets occurring in the western corinth rift greece during a large swarm are analyzed to retrieve their spatiotemporal characteristics these multiplets activated small subfaults at depth 7 km up to 1 km long at the root of two parallel active normal faults the swarm migrates westward nearly horizontally over 10 km at an average velocity of 50 m d with a diffusivity of 0 5 m2 s 1 it successively activates the aigion fault a relay zone in its hanging wall and the fassouleika fault within each multiplet hypocenters also migrate with diffusivities ranging from 0 001 to 0 4 m2 s 1 the largest internal diffusivities appear at the core of the layer defined by the clusters these results are interpreted as a hydroshear process caused by pore pressure migration within permeable corridors resulting from the intersection of the major faults with a brittle geological layer inherited from the hellenic nappe stack

the magnitude distribution of declustered earthquakes in southern california abstract the binned distribution densities of magnitudes in both the complete and the declustered catalogs of earthquakes in the southern california region have two significantly different branches with crossover magnitude near m 4 8 in the case of declustered earthquakes the b values on the two branches differ significantly from each other by a factor of about two the absence of self similarity across a broad range of magnitudes in the distribution of declustered earthquakes is an argument against the application of an assumption of scale independence to models of main shock earthquake occurrence and in turn to the use of such models to justify the assertion that earthquakes are unpredictable the presumption of scale independence for complete local earthquake catalogs is attributable not to a universal process of self organization leading to future large earthquakes but to the universality of the process that produces aftershocks which dominate complete catalogs

waveform relocated earthquake catalog for southern california 1981 to june 2011 we determine a new relocated catalog hys catalog 2011 for southern california from 1981 through june 2011 about 75 3 of the hypocenters are calculated with absolute and differential travel time picks and 24 7 could be relocated only by using absolute travel time picks with 3d or 1d velocity models the total catalog consists of more than 502 000 earthquakes in the region extending from baja california in the south to coalinga and owens valley in the north the catalog consists of three m 7 1 m 7 2 and m 7 3 mainshocks their foreshocks and aftershocks and background seismicity caused by tectonic and other processes in the southern california crust hypocenters in the new relocated catalog exhibit tighter spatial clustering of seismicity than does the routinely generated catalog and the depth distribution is tighter and reflects the thickness of the seismogenic zone more accurately compared to the standard catalog the relocated hypocenters are more easily related to other data sets such as mapped late quaternary faults

oceanic impetus for convective onset of the madden julian oscillation in the western indian ocean abstracta theory for intraseasonal atmosphere ocean atmosphere feedback is supported whereby oceanic equatorial rossby waves are partly forced in the eastern indian ocean by the madden julian oscillation mjo reemerge in the western indian ocean 70 days later and force large scale convergence in the atmospheric boundary layer that precedes mjo deep convection downwelling equatorial rossby waves permit high sea surface temperature sst and enhance meridional and zonal sst gradients that generate convergent circulations in the atmospheric boundary layer the magnitude of the sst and sst gradient increases are 0 25 c and 1 5 c mm 1 1 megameter is equal to 1000 km respectively the atmospheric circulations driven by the sst gradient are estimated to be responsible for up to 45 of the intraseasonal boundary layer convergence observed in the western indian ocean the sst induced boundary layer convergence maximizes 3 4 days prior to the convective maximum and is hypothesized to serve as a trigger for

sea level response to enso along the central california coast how the 1997 1998 event compares with the historic record abstract long term monthly sea level and sea surface temperature sst anomalies from central california show that during winter months positive anomalies are associated with el nino events and the negative ones with la nina events there is no significant impact on monthly mean anomalies associated with pacific decadal oscillations although there is a tendency for more extreme events and greater variance during positive decadal oscillations the very strong 1997 1998 el nino was analyzed with respect to the long term historic record to assess the forcing mechanisms for sea level and sst beginning in the spring of 1997 we observed several long period 30 days fluctuations in daily sea level with amplitudes of over 10 cm at san francisco california fluctuations of poleward long period alongshore wind stress anomalies awsa are coherent with the sea level anomalies however the wind stress cannot entirely account for the observed sea level signals the sea level fluctuations are also correlated with sea level fluctuations observed further south at los angeles and tumaco columbia which showed a poleward phase propagation of the sea level signal we suggest that the sea level fluctuations were to a greater degree forced by the passage of remotely generated and coastally trapped waves that were generated along the equator and propagated to the north along the west coast of north america however both local and remote awsa can significantly modulate the sea level signals the arrival of coastally trapped waves began in the spring of 1997 which is earlier than previous strong el nino events such as the 1982 1983 event

analysis of a reconstructed oceanic kelvin wave dynamic height dataset for the period 1974 2005 abstract intraseasonal oceanic kelvin waves are the dominant mode of variability in the thermocline of the equatorial pacific dynamic height data from the tropical atmosphere ocean tao array of buoys moored in the tropical pacific offer a convenient grid on which to study the waves but can only be effectively applied to study basinwide wave activity since about 1988 because of insufficient data at earlier times kelvin wave signals are also present in sea level data from island and coastal sites from the university of hawaii sea level center some of which are available from before 1970 and up to 2003 this work describes a technique for reconstructing equatorial dynamic height data back to 1974 by utilizing regression relationships between the tao data and daily sea level time series from 11 stations in the tropical pacific the reconstructed data are analyzed for skill in approximating kelvin wave signals when tao data are available reconstructed kelvin wave signals prior to the tao period are then

interannual variability of tehuantepec eddies 1 topex poseidon satellite altimeter observations and the naval research laboratory layered ocean model simulations show interannual variability in the number and intensity of tehuantepec eddies off the mexican southwest coast analysis of the results illustrates that downwelling coastally trapped waves which are generated in the equatorial pacific play a crucial role in the modulation and generation of tehuantepec eddies and a dominant role in tehuantepec eddy interannual variability this introduces a new paradigm in which the generation and modulation of tehuantepec eddies is not exclusively explained in terms of the strong and intermittent tehuantepec wind events in fact the results show anticyclonic eddy formation during periods of calm tehuantepec winds that is specifically exemplified by the formation of two anticyclonic tehuantepec eddies during a 5 month period of weak gulf of tehuantepec winds during summer of 1997 furthermore the satellite observed and nlom simulated proliferation of tehuantepec eddies during el nino years is explained by the corresponding increase in downwelling coastally trapped waves and a lack of increase in the number and strength of tehuantepec wind events during el nino years

monitoring the 1979 1985 equatorial pacific current transports with expendable bathythermograph data geostrophic transports of the major equatorial currents including the equatorial undercurrent and the south equatorial current have been estimated on a bimonthly basis in the central and western pacific over the 1979 1985 period this was made possible by a collection of carefully checked expendable bathythermograph xbt data and a few hydrocast and conductivity temperature depth data this collection considerably improved the number and quality of temperature profiles of the original institut francais de recherche scientifique pour le developpement en cooperation orstom scripps institute of oceanography tropical pacific xbt ship of opportunity program the temperature profiles were first grouped independently of longitude in regions around mean xbt tracks dynamic heights were then calculated relative to 400 db through a t s relationship deduced from the climatological levitus file geostrophic currents were calculated along the roughly south north oriented fiji hawaii and new caledonia japan mean xbt tracks using a specific technique this technique which combines fourier filtering in the meridional direction and in time also ensures the continuity across the equator between geostrophic currents deduced from the first and second derivatives of the meridional pressure field the filter coefficients in the meridional direction were determined through an adjustment of geostrophic currents to directly measured currents using the mean of data collected along 165 e during six tropical ocean and global atmosphere toga orstom cruises finally transports of the main equatorial currents were computed in a subjective way between 20 n and 20 s 0 400 m using monthly charts of geostrophic currents along the two mean xbt tracks the transports in the central pacific were compared to the transports derived from the semicontinuous direct current measurements taken during the hawaii tahiti shuttle experiment in 1979 1980 and during the line island profiling project pacific equatorial ocean dynamics experiment in 1982 1983 reasonable agreement demonstrates that it is possible to use xbt data for transport indexes of the major equatorial currents in the central and western pacific

extending earthquakes reach through cascading earthquakes whatever their size can trigger other earthquakes mainshocks cause aftershocks to occur which in turn activate their own local aftershock sequences resulting in a cascade of triggering that extends the reach of the initial mainshock a long lasting difficulty is to determine which earthquakes are connected either directly or indirectly here we show that this causal structure can be found probabilistically with no a priori model nor parameterization large regional earthquakes are found to have a short direct influence in comparison to the overall aftershock sequence duration relative to these large mainshocks small earthquakes collectively have a greater effect on triggering hence cascade triggering is a key component in earthquake interactions

modeling the seasonal and interannual variability of the northern gulf of california salinity 1 the 7 years 2003 2009 of output from a regional version of the hybrid coordinate ocean model hycom nested in global hycom are used to study the seasonal and interannual variability of the salinity in the northern gulf of california ngoc previous studies illustrate that the ngoc is characterized by an annual evaporation of 0 9 m yr this evaporation generates high sea surface salinity sss water which reaches a maxima in the ngoc 37 and decreases to 35 toward the entrance of the gulf of california the ngoc surface water is interannually modulated by fluctuations in evaporation and by fluctuations in the low salinity water transported into the region by poleward eastern boundary currents the fluctuations in the transport of low salinity water are linked to the arrival of equatorially originated coastally trapped waves the crucial role of the transport of low salinity water for the interannual variability of sss is illustrated by the 2006 and 2008 fall seasons which include the lowest simulated salinity of the period 2003 2009 the lowest salinity in 2006 and 2008 cannot be explained solely by evaporation because 2006 was characterized by the largest evaporation of the period 2003 2009 however the presence of the lowest salinity environment can be attributed to the evaporation in conjunction with the largest upper ocean transport of low salinity water carried to the ngoc by the 2006 and 2008 coastally trapped waves intensified poleward eastern boundary currents

earthquake failure sequences along a cellular fault zone in a three dimensional elastic solid containing asperity and nonasperity regions numerical simulations of earthquake failure sequences along a discrete cellular fault zone are performed for a three dimensional 3 d model representing approximately the central san andreas fault the model consists of an upper crust overlying a lower crust and mantle region together defining an elastic half space with a vertical half plane fault the fault contains a region where slip is calculated on a uniform grid of cells governed by a static kinetic friction law and regions where slip is prescribed so as to represent tectonic loading aseismic fault creep and adjacent great earthquakes the computational region models a 70 km long and 17 5 km deep section of the san andreas fault to the nw of the great 1857 rupture zone different distributions of stress drops on failing computational cells are used to model asperity parkfield asperity and nonasperity fault regions the model is inherently discrete and corresponds to a situation in which a characteristic size of geometric disorder within the fault i e cell size here a few hundreds of meters is much larger than the nucleation size of the order of tens of centimeters to tens of meters based on slip weakening or state evolution slip distances the computational grid is loaded by a constant plate motion imposed at the lower crust upper mantle and creeping fault regions and by a staircase slip history imposed at the 1857 and 1906 rupture zones stress transfer along and outside the fault due to the imposed loadings and failure episodes along the computational grid is calculated using 3 d elastic dislocation theory the resulting displacement field in the computational region is compatible with geodetic and seismological observations only when the asperity and nonasperity regions are characterized by significantly different average stress drops the frequency magnitude statistics of the simulated failure episodes are approximately self similar for small events with b 1 2 the b value of statistics based on rupture area ba is about 1 but are strongly enhanced with respect to self similarity for events larger than a critical size this is interpreted as a direct manifestation of our 3 d elastic stress transfer calculations beyond certain rupture area and potency seismic moment divided by rigidity release values the event is usually unstoppable and it continues to grow to a size limited by a characteristic model dimension this effect is not accounted for by cellular automata and block spring models in which the adopted simplified stress transfer laws fail to scale properly with increasing rupture size the simulations suggest that local maxima in observed frequency magnitude statistics correspond to dimensions of coherent brittle zones such as the width of the seismogenic layer or the length of a fault segment bounded by barriers the analysis indicates that a single cell size representing approximately a single scale of geometric disorder cannot induce self similarity in a 3 d elastic model over a broad range of magnitudes a representation of geometric disorder covering a range of scales may thus be required to generate a wide domain of self similar gutenberg richter statistics our simulations show a great diversity in the mode of failure of the parkfield asperity the earthquakes themselves define an irregular sequence of events the modeling like many other discrete fault models suggests that expectations for periodic parkfield earthquakes and or simple precursory patterns repeating from one event to the other are unrealistic

computing a large refined catalog of focal mechanisms for southern california 1981 2010 temporal stability of the style of faulting using the method developed by hardebeck and shearer 2002 2003 termed the hash method we calculate focal mechanisms for earthquakes that occurred in the southern california region from 1981 to 2010 when available we use hypocenters refined with differential travel times from waveform cross correlation using both the p wave first motion polarities and the s p amplitude ratios computed from three component seismograms we determine mechanisms for more than 480 000 earthquakes and analyze the statistical features of the whole catalog we filter the preliminary catalog with criteria associated with mean nodal plane uncertainty and azimuthal gap and obtain a high quality catalog with approximately 179 000 focal mechanisms as more s p amplitude ratios become available after 2000 the average nodal plane uncertainty decreases significantly compared with mechanisms that include only p wave polarities in general the parameters of the focal mechanisms have been stable during the three decades the dominant style of faulting is high angle strike slip faulting with the most likely p axis centered at n5 e for earthquakes of m 2 5 events using the 210 moment tensor solutions in tape et al 2010 as benchmarks we compare the focal plane rotation angles of common events in the catalog seventy percent of common earthquakes match well with rotation angles less than the typical nodal plane uncertainty the common events with relatively large rotation angles are either located around the edge of the scsn network or poorly recorded

asymmetric distribution of aftershocks on large faults in california summary we examine the relations between spatial symmetry properties of earthquake patterns along faults in california ca and local velocity structure images to test the hypothesis that ruptures on bimaterial faults have statistically preferred propagation directions the analysis employs seismic catalogues for 25 fault zones in ca we distinguish between clustered and homogeneous parts of each catalogue using a recently introduced earthquake cluster analysis and examine asymmetry of offspring with respect to parent events within the clustered portion of each catalogue the results indicate strong asymmetric patterns along large faults with prominent bimaterial interfaces e g sections of the san andreas fault with enhanced activities in the directions predicted for the local velocity contrasts and absence of significant asymmetry along most other faults assuming the observed asymmetric properties of seismicity reflect the properties of the parent earthquake ruptures the discussed methodology and results can be used to develop refined estimates of seismic shaking hazard associated with individual fault zones

predictive modeling of the seismic cycle of the greater san francisco bay region the seismic cycle for the san francisco bay region is synthesized by a model combining the pre and post 1906 seismic histories the long term acceleration of seismic release seismic moment benioff strain release or event count in the seismic cycle and the shorter term accelerations preceding the larger earthquakes within that cycle are modeled using an empirical predictive technique called time to failure analysis in which rate of seismic release is proportional to an inverse power of the remaining time to failure the exponent of time to failure in the accelerating sequences appears to be scale invariant and the length of the full cycle is estimated at 269 50 years the 1989 loma prieta earthquake which is the culmination of the first subcycle in the present long term seismic cycle should have been predictable with an uncertainty of 2 years in time and 0 5 in magnitude although the specific location at loma prieta was not predictable by this technique if our model is correct and if the loma prieta earthquake is the culmination of a subcycle the san francisco bay region should be entering a relatively long 20 50 years period of seismic quiescence above magnitude 6 a great earthquake such as the 1906 san francisco event would appear to be more than a century in the future

detection of the fast kelvin wave teleconnection due to el nino southern oscillation previous analyses of the ocean state along the western american coast have often indicated unexpectedly slow and limited propagation of coastally trapped kelvin waves associated with the e1 nifio southern oscillation in contrast theoretical and numerical ocean models demonstrate that these kelvin waves are a rapid and long range teleconnection between the low and high latitude pacific ocean strongly impacting both the surface coastal currents and nutrient upwelling sea level variations along the western coast of north america are reexamined under the assumption that tropically forced kelvin waves are produced in bursts of several months duration a cross correlation analysis restricted to mid 1982 to mid 1983 is performed between galapagos island and stations along western central and north america a coastally trapped kelvin wave is revealed to propagate at a speed of 2 3 m s from the tropical pacific to the aleutian island chain the observed phase speed agrees with the estimated speed of a kelvin wave based on the average density profile of the ocean near the coast weakere1 nifio events in 1986 1987 and 1991 1992 appear to contain a combination of this remotsignal and local wind forcing the wave propagation speed calculated from the spectrhl phase is shown to be sensitive to the presence of other noise processes in the observations this is demonstrated through an analysis of a synthetic sea level data set that contains many of the essential features of the real sea level data a relatively small level of red noise can give a 100 expected error in the estimated propagation speed this suggests a new explanation for this important inconsistency within dynamical oceanography

wind forced intraseasonal sea level variability of the extratropical oceans abstract seven years worth of sea level observations from the topex poseidon altimeters and wind observations from the european remote sensing satellites ers 1 2 scatterometers were used to investigate the dynamics of large scale intraseasonal sea level variability at mid and high latitudes coherent patterns of sea level variability with spatial scales of 1000 km and timescales of 20 days to 1 year are identified in three particular regions the bellingshausen basin west of drake passage the australian antarctic basin and the central north pacific ocean 30 50 n near the date line significant coherence is found between wind stress curl and the sea level variability a simple barotropic vorticity equation in which the time rate of relative vorticity variation is balanced by the wind stress curl and a damping term is used to simulate the sea level anomalies with a significant degree of correlation with the observations although the coherence between the simulation and the observation is signifi

the fractal description of seismicity summary the stable estimation of multifractal characteristics of seismicity is considered the data are world and accessible regional catalogues of m 2 4 events our attention is focused on the range of scales in which the renyi functionals admit of scale invariant behaviour we find that the stable fractal analysis of hypocentres is generally difficult as to epicentres we have carried out a stable analysis for seven regions worldwide in the range of scales 1 1 7 decades the estimates of generalized dimensions admit of tectonic interpretation

in situ evidence for an ancient aqueous environment at meridiani planum mars sedimentary rocks at eagle crater in meridiani planum are composed of fine grained siliciclastic materials derived from weathering of basaltic rocks sulfate minerals including magnesium sulfate and jarosite that constitute several tens of percent of the rock by weight and hematite cross stratification observed in rock outcrops indicates eolian and aqueous transport diagenetic features include hematite rich concretions and crystal mold vugs we interpret the rocks to be a mixture of chemical and siliciclastic sediments with a complex diagenetic history the environmental conditions that they record include episodic inundation by shallow surface water evaporation and desiccation the geologic record at meridiani planum suggests that conditions were suitable for biological activity for a period of time in martian history

complex spatiotemporal evolution of the 2008 mw 4 9 mogul earthquake swarm reno nevada interplay of fluid and faulting after approximately two months of swarm like earthquakes in the mogul neighborhood of west reno nv seismicity rates and event magnitudes increased over several days culminating in an mw 4 9 dextral strike slip earthquake on 26 april 2008 although very shallow the mw 4 9 mainshock had a different sense of slip than locally mapped dip slip surface faults we relocate 7 549 earthquakes calculate 1 082 focal mechanisms and statistically cluster the relocated earthquake catalog to understand the character and interaction of active structures throughout the mogul nv earthquake sequence rapid temporary instrument deployment provides high resolution coverage of microseismicity enabling a detailed analysis of swarm behavior and faulting geometry relocations reveal an internally clustered sequence in which foreshocks evolved on multiple structures surrounding the eventual mainshock rupture the relocated seismicity defines a fault fracture mesh and detailed fault structure from approximately 2 6 km depth on the previously unknown mogul fault that may be an evolving incipient strike slip fault zone the seismicity volume expands before the mainshock consistent with pore pressure diffusion and the aftershock volume is much larger than is typical for an mw 4 9 earthquake we group events into clusters using space time magnitude nearest neighbor distances between events and develop a cluster criterion through randomization of the relocated catalog identified clusters are largely mainshock aftershock sequences without evidence for migration occurring within the diffuse background seismicity the migration rate of the largest foreshock cluster and simultaneous background events is consistent with it having triggered or having been triggered by an aseismic slip event