seismogeodetic p wave amplitude no evidence for strong determinism whether the final properties of large earthquakes can be inferred from initial observations of rupture deterministic rupture is valuable for understanding earthquake source processes and is critical for operational earthquake and tsunami early warning initial p wave characteristics of small to moderate earthquakes scale with magnitude yet observations of large to great earthquakes saturate resulting in magnitude underestimation whether saturation is inherent to earthquake dynamics or rather is due to unreliable observation of long period signals with inertial seismic instrumentation is unclear seismogeodetic methods are better suited for broadband observation of large events in the near field in this study we investigate the deterministic potential of seismogeodetically derived p wave amplitude using a dataset of 14 medium to great earthquakes around japan our results indicate that seismogeodetic p wave amplitude is not a reliable predictor of magnitude opposing the notion of strong determinism in the first few seconds of rupture

linking so2 emission rates and seismicity by continuous wavelet transform implications for volcanic surveillance at san cristobal volcano nicaragua san cristobal volcano is the highest and one of the most active volcanoes in nicaragua its persistently high activity during the past decade is characterized by strong degassing and almost annual vei 1 2 explosions which present a threat to the local communities following an eruption on 8 september 2012 the intervals between eruptions decreased significantly which we interpret as the start of a new eruptive phase we present here the results of semi continuous so2 flux measurements covering a period of 18 months obtained by two scanning uv doas instruments installed as a part of the network for observation of volcanic and atmospheric change project and the results of real time seismic amplitude measurements rsam data our data comprise a series of small to moderately explosive events in december 2012 june 2013 and february 2014 which were accompanied by increased gas emissions and seismicity in order to approach an early warning strategy we present a statistical method for the joint analysis of gas flux and seismic data by using continuous wavelet transform and cross wavelet transform xwt methods this analysis shows that the xwt coefficients of so2 flux and rsam are in good agreement with the occurrence of eruptive events and thus may be used to indicate magma ascent into the volcano edifice such multi parameter surveillance efforts can be useful for the interpretation and surveillance of possible eruptive events and could thus be used by local institutions for the prediction of upcoming volcanic unrest

changes in el nino southern oscillation enso conditions during the greenland stadial 1 gs 1 chronozone revealed by new zealand tree rings the warming trend at the end of the last glacial was disrupted by rapid cooling clearly identified in greenland greenland stadial 1 or gs 1 and europe younger dryas stadial or yd this reversal to glacial like conditions is one of the best known examples of abrupt change but the exact timing and global spatial extent remain uncertain whilst the wider atlantic region has a network of high resolution proxy records spanning gs 1 the pacific ocean suffers from a scarcity of sub decadally resolved sequences here we report the results from an investigation into a tree ring chronology from northern new zealand aimed at addressing the paucity of data the conifer tree species kauri agathis australis is known from contemporary studies to be sensitive to regional climate changes an analysis of a historic 452 year kauri chronology confirms a tropical pacific teleconnection via the el nino southern oscillation enso we then focus our study on a 1010 year sub fossil kauri chronology that has been precisely dated by comprehensive radiocarbon dating and contains a striking ring width downturn between 12 500 and 12 380 cal bp within gs 1 wavelet analysis shows a marked increase in enso like periodicities occurring after the downturn event comparison to low and mid latitude pacific records suggests a coherency with enso and southern hemisphere atmospheric circulation change during this period the driver s for this climate event remain unclear but may be related to solar changes that subsequently led to establishment and or increased expression of enso across the mid latitudes of the pacific seemingly independent of the atlantic and polar regions

the modal evolution of the southern oscillation abstract the implementation of a progressive fourier transform applied to time series representative of the el nino southern oscillation enso provides a visual review of the frequency modes that have dominated throughout the available time series record the modal evolution maps constructed from the progressive fourier transform demonstrate that the enso is largely composed of a discrete number of low frequency modes and that these dominant modes demonstrate a localized influence in a temporal sense persisting for periods of years before showing deviations in characteristic frequency in support of other research significant energy is maintained in the quasi biennial and quasi quadrennial period modes throughout the length of available southern oscillation index soi record evident through the most recent record of both the soi and nino region sea surface temperature sst time series is the emergence of energy in the quasi decadal period modes the presence of a quasi decadal mode has also bee

interdecadal changes of 30 yr sst normals during 1871 2000 abstract sst predictions are usually issued in terms of anomalies and standardized anomalies relative to a 30 yr normal climatological mean cm and standard deviation sd the world meteorological organization wmo suggests updating the 30 yr normal every 10 yr in complying with the wmo s suggestion a new 30 yr normal for the 1971 2000 base period is constructed to put the new 30 yr normal in historical perspective all the 30 yr normals since 1871 are investigated starting from the beginning of each decade 1871 1900 1881 1910 1971 2000 using the extended reconstructed sea surface temperature ersst on a 2 grid for 1854 2000 and the hadley centre sea ice and sst dataset hadisst on a 1 grid for 1870 1999 eleven 30 yr normals are calculated and the interdecadal changes of seasonal cm seasonal sd and seasonal persistence p are discussed the interdecadal changes of seasonal cm are prominent 0 3 0 6 in the tropical indian ocean the midlatitude north pacific the midlatitude no

time frequency variability of enso and stochastic simulations abstract the time frequency spectral structure of el nino southern oscillation enso time series holds much information about the physical dynamics of the enso system the authors have analyzed changes of the spectrum with time of three enso indices the conventional southern oscillation index soi nino3 sea surface temperatures and a tropical pacific rain index over the period 1871 1995 three methods of time frequency analysis windowed fourier transform wavelet analysis and windowed prony s method were used and the results are in good agreement the time frequency spectra of all the series show strong multidecadal variations over the past century in particular there was reduced activity of enso in the 2 3 yr periodicity range during the period 1920 60 compared with both the earlier and later periods the dominant frequencies in the spectra do not appear to be constrained to certain frequency bands and there is no evidence that the enso system has fixed modes of oscillation the qualitative b

improved rapid magnitude estimation for a community based low cost mems accelerometer network immediately following the m w 7 2 darfield new zealand earthquake over 180 quake catcher network qcn low cost micro electro mechanical systems accelerometers were deployed in the canterbury region using data recorded by this dense network from 2010 to 2013 we significantly improved the qcn rapid magnitude estimation relationship the previous scaling relationship lawrence et al 2014 did not accurately estimate the magnitudes of nearby 35 km events the new scaling relationship estimates earthquake magnitudes within 1 magnitude unit of the gns science geonet earthquake catalog magnitudes for 99 of the events tested within 0 5 magnitude units for 90 of the events and within 0 25 magnitude units for 57 of the events these magnitudes are reliably estimated within 3 s of the initial trigger recorded on at least seven stations in this report we present the methods used to calculate a new scaling relationship and demonstrate the accuracy of the revised magnitude estimates using a program that is able to retrospectively estimate event magnitudes using archived data online material table of magnitude estimates for quake catcher network detected events and figures clarifying the linear fitting technique used to calculate the chung et al revised scaling relationship

the fast climate fluctuations during the stadial and interstadial climate states rapid climate changes during the last glacial period were first observed in ice core records dansgaard and others 1982 these shifts between interstadials called dansgaard oeschger d o events and stadials or deep glaciation were later seen in atlantic sediment records bond and others 1993 pointing to the ocean circulation as a strong component in the dynamics of these shifts wright and stocker 1991 the interstadial states are observed to have a characteristic sawtooth shape indicating a gradual drift of the stable interstadial state toward the stable stadial state in order to contrast the two climate states we have separated the 18o signal from the greenland icecore project ice core into periods corresponding to the two states the climate variability in the two different climatic states is different johnsen and others 1997 we find that the standard deviation is significantly larger in the stadial than in the interstadial state both states are found to have a larger standard deviation than the holocene part of the record the correlation times in the different states are difficult to obtain because of limited data resolution and diffusion of the isotopic signal however using a statistical technique we have estimated the correlation times we do not find significant differences in the correlation times which are of the order of months in the different climatic states these findings are interpreted in the context of a simple linear stochastic model which provides information about the relative roles of the climatic forcing and the stability of the climate state governing the climate variability

the salinity signature of the cross shelf exchanges in the southwestern atlantic ocean satellite observations satellite derived sea surface salinity sss data from aquarius and smos are used to study the shelf open ocean exchanges in the western south atlantic near 35 s away from the tropics these exchanges cause the largest sss variability throughout the south atlantic the data reveal a well defined seasonal pattern of sss during the analyzed period and of the location of the export of low salinity shelf waters in spring and summer low salinity waters over the shelf expand offshore and are transferred to the open ocean primarily southeast of the river mouth from 36 s to 37 30 s in contrast in fall and winter low salinity waters extend along a coastal plume and the export path to the open ocean distributes along the offshore edge of the plume the strong seasonal sss pattern is modulated by the seasonality of the along shelf component of the wind stress over the shelf however the combined analysis of sss satellite derived sea surface elevation and surface velocity data suggest that the precise location of the export of shelf waters depends on offshore circulation patterns such as the location of the brazil malvinas confluence and mesoscale eddies and meanders of the brazil current the satellite data indicate that in summer mixtures of low salinity shelf waters are swiftly driven toward the ocean interior along the axis of the brazil malvinas confluence in winter episodic wind reversals force the low salinity coastal plume offshore where they mix with tropical waters within the brazil current and create a warmer variety of low salinity waters in the open ocean

carbon dioxide precedes temperature change during short term pauses in multi millennial palaeoclimate records abstract in antarctica ice core temperature has traditionally been regarded as a leading variable to carbon dioxide co2 during the last 400 000 years before present b p this finding is in contrast to most reports on global mean surface temperature and atmospheric co2 for the last 150 years however previous techniques for establishing leading or lagging ll relations between paired global warming variables have required that the time series show constant frequency stationarity herein we show that on orbital and multi millennial time scales the vostok antarctic ice core displays 9 periods of 8 7 kyr 5 kyr during which co2 becomes a leading variable to temperature six of the 9 periods were associated with short term pauses occurring during 4 major glaciation deglaciation periods we find that co2 also leads temperature during short pauses in the major cyclic pattern of the greenland time series in the latter series there are also two contrasting cycle developments in the first contrasting cycle developments lasting from 103 5 to 79 ka there is an in phase relation between co2 and temperature with a slope of 0 75 in the second contrasting cycle developments lasting from 61 5 to 43 5 ka there is an out of phase relation with a slope of 0 67 in addition the latter shows a see saw pattern between arctic and antarctic temperatures

magnitude determination using initial p waves a single station approach 1 prompted by recent success in the research and application of earthquake early warning systems we conducted an investigation into the relationship between the magnitudes of earthquakes and the properties of the first three seconds of the p waves at a single station using waveforms at station nacb of the broadband array in taiwan for seismology from 46 earthquakes within 100 km epicentral distance we found a linear correlation between the magnitudes and the logarithmic characteristic periods of the initial p waves for earthquakes up to magnitude 6 5 we also detected a deterministic relationship between the magnitudes and the peak amplitudes of the initial p waves for earthquakes of magnitude m 6 5 while further study needs to be done on the behavior of the initial p wave peak amplitudes from larger earthquakes we propose here that the characteristic periods and peak amplitudes of the first three seconds of the p waves be used jointly in onsite single station earthquake early warning operations

magnitude scaling relations from p waves in southern california 1 we derive empirical magnitude scaling relationships for southern california using a dataset of 59 past earthquakes recorded in southern california by the southern california seismic network scsn between 1992 and 2003 the events range in magnitude from 3 0 to 7 3 we use the maximum predominant period pmax and the peak displacement amplitude pd measured from the first 4 seconds of p wave arrivals to determine period magnitude and amplitude magnitude scaling relationships respectively our calibration study shows that the scaling relationships are similar to those derived for northern california the average error in magnitude estimates is 0 2 magnitude units for events with magnitudes smaller than 4 5 m 6 5

time varying spectral characteristics of enso over the last millennium the characteristics of el nino southern oscillation enso spectra over the last millennium are examined to characterise variability over past centuries seven published palaeo enso reconstructions and nino3 4 from six coupled model intercomparison project phase 5 and paleoclimate modelling intercomparison project phase 3 cmip5 pmip3 last millennium simulations were analysed the corresponding historical and pre industrial control cmip5 pmip3 simulations were also considered the post 1850 spectrum of each modelled or reconstructed enso series captures aspects of the observed spectrum to varying degrees we note that no single model or enso reconstruction completely reproduces the instrumental spectral characteristics the spectral power across the 2 3 years near biennial 3 8 years classical enso and 8 25 years decadal periodicity bands was calculated in a sliding 50 year window revealing temporal variability in the spectra there was strong temporal variability in the spectral power of each periodicity band in observed nino3 4 and soi and for all reconstructions and simulations of enso significant peaks in spectral power such as observed in recent decades also occur in some of the reconstructed palaeo enso around 1600 the early 1700s and 1900 and modelled series around the major volcanic eruptions of 1258 and 1452 while the recent increase in spectral power might be in response to enhanced greenhouse gas levels the increase lies within the range of variability across the suite of enso reconstructions and simulations examined here this study demonstrates that the analysis of a suite of enso reconstructions and model simulations can build a broader understanding of the time varying nature of enso spectra and how the nature of the past spectra of enso is to some extent dependant on the climate model or palaeo enso reconstruction chosen

earthquake early warning shakealert in the pacific northwest we evaluate the performance of earthquake early warning algorithm elarms 2 earthquake alarm system v 2 in the pacific northwest real time and prerecorded seismic data from oregon california and washington in the united states and british columbia in canada are used the earthquakes tested range up to moment magnitude 7 2 the limit for which the elarms 2 magnitude method is accurate elarms 2 reliably detects catalog magnitude 3 and larger earthquakes within the network but the cut off magnitude for accurate event recognition is higher for events offshore and on the edges of the network we have made several adjustments that make the elarms 2 algorithm less likely to falsely report multiple alerts for earthquakes replaying of past earthquakes shows that the new settings improve the algorithm s behavior for edge cases while not degrading previously well constrained solutions within the dense part of the network we expect few false alerts none that would predict significant shaking anywhere in our region even though elarms 2 assumes a fixed earthquake depth the epicenter and magnitude estimates are accurate enough to provide good predictions of shaking intensities online material tables listing parameters of 31 calibration earthquakes elarms 2 real time detections and comparison of elarms 2 performance for calibration events before and after adjusting configuration

a numerical study of the southwestern atlantic shelf circulation stratified ocean response to local and offshore forcing 1 this article discusses the results of a suite of numerical simulations of the oceanic circulation in the southwestern atlantic shelf region that are aimed to characterize its mean circulation and seasonal variability and to determine the dynamical mechanisms controlling them our experiments indicate that south of 40s the mean circulation is dominated by a general northeastward flow in the southern portion of the shelf which is controlled by the discharges from the magellan straits tidal mixing wind forcing and the offshore influence of the malvinas current farther north the region from 40 st o 33s presents the highest seasonal variability with intrusions of cold sub antarctic waters

multiscale temporal variability of warm season precipitation over north america statistical analysis of radar measurements directionally averaged time series of precipitation rates for eight warm seasons 1996 2003 over the continental united states derived from next generation weather radar nexrad measurements are analyzed using spectral decomposition methods for the latitudinally averaged data in addition to previously identified diurnal and semidiurnal cycles the temporal spectra show cross scale self similarity and periodicity this property is revealed by a power law scaling with an exponent of 4 3 for the frequency band higher than semidiurnal and 3 4 for the 1 3 day band for the longitudinally averaged series the scaling exponent for the frequency band higher than semidiurnal changes from 4 3 to 5 3 revealing anisotropic properties the dominant periods and propagation speeds display temporal variability on about 1 2 1 4 11 and 25 days composite patterns describing periods of 5 days display the eastward propagation characteristic of classical mesoscale convective organization the lower frequency 5 days patterns propagate westward suggesting the influence of large scale waves and both dominant periods and propagation speeds show marked interannual variability the implied dependence between propagation and mean flow for 5 days is consistent with the macrophysics of warm season convective organization and extends known dynamical mechanisms to a statistical framework

real time earthquake detection and hazard assessment by elarms across california 1 elarms is a network based methodology for rapid earthquake detection location and hazard assessment in the form of magnitude estimation and peak ground motion prediction the methodology is currently being tested as part of the real time seismic system in california leveraging the resources of the california integrated seismic network cisn and the advanced national seismic system a total of 603 velocity and acceleration sensors at 383 sites across the state stream waveform data to elarms processing modules at three network processing centers where waveforms are reduced to a few parameters these parameters are then collected and processed at uc berkeley to provide a single statewide prediction of future ground shaking that is updated every second the system successfully detected the mw 5 4 alum rock earthquake in northern california for which it generated an accurate hazard prediction before peak shaking began in san francisco it also detected the mw 5 4 chino hills earthquake in southern california the median system latency is currently 11 8 sec the median waveform data latency is 6 5 sec

air sea heat fluxes associated to mesoscale eddies in the southwestern atlantic ocean and their dependence on different regional conditions heat fluxes between the ocean and the atmosphere largely represent the link between the two media a possible mechanism of interaction is generated by mesoscale ocean eddies in this work we evaluate if eddies in southwestern atlantic swa ocean may significantly affect flows between the ocean and the atmosphere atmospherics conditions associated with eddies were examined using data of sea surface temperature sst sensible shf and latent heat flux lhf from ncep cfsr reanalysis on average we found that ncep cfsr reanalysis adequately reflects the variability expected from eddies in the swa considering the classical eddy pumping theory anticyclonic cyclonic eddies cause maximum positive negative anomalies with maximum mean anomalies of 0 5 c 0 5 c in sst 6 w m2 4 w m2 in shf and 12 w m2 9 w m2 in lhf however a regional dependence of heat fluxes associated to mesoscale cyclonic eddies was found in the turbulent brazil malvinas confluence bmc region they are related with positive heat flux anomaly ocean heat loss while in the rest of the swa they behave as expected ocean heat gain we argue that eddy pumping do not cool enough the center of the cyclonic eddies in the bmc region simply because most of them trapped very warm waters when they originate in the subtropics the article therefore concludes that in the swa 1 a robust link exists between the sst anomalies generated by eddies and the local anomalous heat flow between the ocean and the atmosphere 2 in the bmc region cyclonic eddies are related with positive heat anomalies contrary to what is expected

multi year predictability in a coupled general circulation model multi year to decadal variability in a 100 year integration of a bmrc coupled atmosphere ocean general circulation model cgcm is examined the fractional contribution made by the decadal component generally increases with depth and latitude away from surface waters in the equatorial indo pacific ocean the relative importance of decadal variability is enhanced in off equatorial wings in the subtropical eastern pacific the model and observations exhibit enso like decadal patterns analytic results are derived which show that the patterns can in theory occur in the absence of any predictability beyond enso time scales in practice however modification to this stochastic view is needed to account for robust differences between enso like decadal patterns and their interannual counterparts an analysis of variability in the cgcm a wind forced shallow water model and a simple mixed layer model together with existing and new theoretical results are used to improve upon this stochastic paradigm and to provide a new theory for the origin of decadal enso like patterns like the interdecadal pacific oscillation and pacific decadal oscillation in this theory enso driven wind stress variability forces internal equatorially trapped kelvin waves that propagate towards the eastern boundary kelvin waves can excite reflected internal westward propagating equatorially trapped rossby waves rws and coastally trapped waves ctws ctws have no impact on the off equatorial sub surface ocean outside the coastal wave guide whereas the rws do if the frequency of the incident wave is too high then only ctws are excited at lower frequencies both ctws and rws can be excited the lower the frequency the greater the fraction of energy transmitted to rws this lowers the characteristic frequency reddens the spectrum of variability off the equator relative to its equatorial counterpart at low frequencies dissipation acts as an additional low pass filter that becomes more effective as latitude increases at the same time enso driven off equatorial surface heating anomalies drive mixed layer temperature responses in both hemispheres both the eastern boundary interactions and the accumulation of surface heat fluxes by the surface mixed layer act to low pass filter the enso forcing the resulting off equatorial variability is therefore more coherent with low pass filtered decadal enso indices e g nino3 sea surface temperature sst than with unfiltered enso indices consequently large correlations between variability and nino3 extend further poleward on decadal time scales than they do on interannual time scales this explains why decadal enso like patterns have a broader meridional structure than their interannual counterparts this difference in appearance can occur even if enso indices do not have any predictability beyond interannual time scales the wings around 15 20 s and sub surface variability at many other locations are predictable on interannual and multi year time scales this includes westward propagating internal rws within about 25 of the equator the slowest of these take up to 4 years to reach the western boundary this sub surface predictability has significant oceanographic interest however it is linked to only low levels of sst variability consequently extrapolation of delayed action oscillator theory to decadal time scales might not be justified

a global approach to provide magnitude estimates for earthquake early warning alerts 1 we examine five different methods to estimate an earthquake s magnitude using only p wave data for use in earthquake early warning systems we test two input parameters the maximum predominant period of the p wave pmax and the displacement amplitude of the p wave s vertical component pd we apply our algorithms to 174 earthquakes 3 0 m 8 0 from california and japan that have also been used in previous calibration studies we also apply them to 1992 0 2 m 5 7 earthquakes that were processed by the real time earthquake alarm systems in california we find that pmax does not scale with magnitude for small earthquakes m 3 and is less accurate for large magnitude earthquakes than using pd alone we derive a global scaling relation between pd and magnitude and conclude that this global relationship provides the most accurate and robust magnitude estimate this relationship could be applied in earthquake source zones around the world

the salinity signature of the cross shelf exchanges in the southwestern atlantic ocean numerical simulations a high resolution model is used to characterize the dominant patterns of sea surface salinity sss variability generated by the freshwater discharges of the rio de la plata rdlp and the patos mirim lagoon in the southwestern atlantic region we identify three dominant modes of sss variability the first two which have been discussed in previous studies represent the seasonal and the interannual variations of the freshwater plumes over the continental shelf the third mode of sss variability which has not been discussed hitherto represents the salinity exchanges between the shelf and the deep ocean a diagnostic study using floats and passive tracers identifies the pathways taken by the freshwater plumes during the austral winter jja the plumes leave the shelf region north of the bmc during the austral summer djf the plumes are entrained more directly into the bmc a sensitivity study indicates that the high frequency component of the wind stress forcing controls the vertical structure of the plumes while the low frequency component of the wind stress forcing and the interannual variations of the rdlp discharge controls the horizontal structure of the plumes dynamical analysis reveals that the cross shelf flow has a dominant barotropic structure and therefore the sss anomalies detected by aquarius represent net mass exchanges between the shelf and the deep ocean the net cross shelf volume flux is 1 21 sv this outflow is largely compensated by an inflow from the patagonian shelf

wavelet analysis of simulated tropical convective cloud systems part i basic analysis abstract a wavelet analysis of a three dimensional 7 day explicit simulation of the tropical cloud systems in the global atmosphere research programme garp atlantic tropical experiment phase iii is performed three physically distinct regimes squall line nonsquall cloud cluster and scattered convection in a doubly periodic domain are analyzed using discrete meyer wavelets these wavelets are complete and facilitate the inversion of the decomposed modes the full wavelet spectra well characterize the spatial localization of each physical variable in particular the vertical velocity and the condensate fields the probability distribution of the wavelet coefficients is non gaussian despite the horizontal winds the temperature and humidity being closely gaussian in physical space this demonstrates the effectiveness of the wavelet basis for analyzing cloud system organization the full wavelet spectrum also selects a preferred spatial orientation of the convective organization in physical space a p

altimeter derived seasonal circulation on the southwest atlantic shelf 27 43 s altimeter sea surface height ssh fields are analyzed to define and discuss the seasonal circulation over the wide continental shelf in the sw atlantic ocean 27 43 s during 2001 2012 seasonal variability is low south of the rio de la plata rdlp where winds and currents remain equatorward for most of the year winds and currents in the central and northern parts of our domain are also equatorward during autumn and winter but reverse to become poleward during spring and summer transports of shelf water to the deep ocean are strongest during summer offshore and to the southeast of the rdlp details of the flow are discussed using mean monthly seasonal cycles of winds heights and currents along with analyses of empirical orthogonal functions principle estimator patterns bring out the patterns of wind forcing and ocean response the largest part of the seasonal variability in ssh signals is due to changes in the wind forcing described above and changes in the strong boundary currents that flow along the eastern boundary of the shelf the rest of the variability contains a smaller component due to heating and expansion of the water column concentrated in the southern part of the region next to the coast our results compare well to previous studies using in situ data and to results from realistic numerical models of the regional circulation

the influence of the plata river discharge on the western south atlantic shelf 1 the influence of the plata the second largest river in south america extends along a coastal strip of 1300 km historical hydrographic and wind data and numerical simulations are combined to determine the seasonal and interannual variability of the plata plume and its relationship to the magnitude of the river discharge and the intensity and direction of the wind stress our results indicate that the seasonal variability of the river plume is controlled by the alongshore component of the wind stress during el nino the effects of the wind and precipitation anomalies tend to compensate each other preventing anomalous northeastward plume extensions associated to large outflow events numerical experiments confirm this finding and indicate that during el nino the discharge from the plata river spreads offshore

toward earthquake early warning in northern california 1 earthquake early warning systems are an approach to earthquake hazard mitigation which takes advantage of the rapid availability of earthquake information to quantify the hazard associated with an earthquake and issue a prediction of impending ground motion prior to its arrival in populated or otherwise sensitive areas one such method earthquake alarm systems elarms has been under development in southern california and more recently in northern california event magnitude is estimated using the peak amplitude and the maximum predominant period of the initial p wave elarms incorporates ground motion prediction equations and algorithms from shakemap for prediction of ground motions in advance of the s wave arrival the first peak ground motion estimates are available 1 s after the first p wave trigger and are updated each second thereafter for the duration of the event the elarms methodology has been calibrated using 43 events ranging in size from ml 3 0 to mw 7 1 that occurred in northern california since 2001 we present the results of this calibration as well as the first implementation of elarms in an automated noninteractive setting and the results of 8 months of noninteractive operation in northern california between february and september 2006 elarms successfully processed 75 events between md 2 86 to mw 5 0 we find that the elarms methodology processed these events reliably and accurately in the noninteractive setting the median warning time afforded by this method is 49 s at the major population centers of the bay area for these events the magnitude estimate is within an average of 0 5 units of the network derived magnitude and the ground motion prediction from elarms is within an average of 0 1 units of the observed modified mercalli intensity