eseismic towards an ecuadorian volcano seismic repository abstract in this work we present the development description and performance evaluation of two volcano seismological datasets one containing raw seismic signals micsigv1 and another containing a set of 84 distinctive attributes or features for bench marking seisbenchv1 which was extracted from the micsigv1 dataset recorded at cotopaxi volcano in ecuador these datasets represent the first public ecuadorian volcano seismicity repository that will update publish and support the release of data to the scientific community on a continual basis each dataset contains samples of mostly long period and volcano tectonic event classes other types of events such as regional hybrid and icequakes were also included despite their minor presence in the datasets these datasets will serve to provide an important resource for research in signal processing feature calculation feature selection feature space reduction seismic events detection and classification areas the datasets can be downloaded through a copyright agreement that supports the correct use of the released datasets

holocene coastal glaciation of alaska holocene uctuations of the three cirque glaciers on the seward peninsula and ve groups of tidewater and land terminating glaciers along the northernmost gulf of alaska provide a proxy record of late holocene climatic change furthermore the movements of the coastal glaciers were relevant to late holocene native american migration the earliest expansion was recorded about 6850 yr bp by hubbard glacier at the head of yakutat bay in the gulf of alaska however its down fjord advance to the bay mouth was delayed until 2700 bp similarly expansions of the icy bay bering and mccarty glaciers occurred near their present termini by 3600 3000 bp compatible with marked cooling and precipitation increases suggested by the alaskan pollen record decrease in glacier activity 2000 bp was succeeded by advances of gulf coastal glaciers between 1500 and 1300 bp correlative with early medieval expansions across the northern hemisphere a medieval optimum encompassing at least a few centuries prior to ad 1200 is recognized by general retreat of land terminating glaciers but not of all tidewater glaciers little ice age advances of land based glaciers many dated with the precision of tree ring cross dating were centered on the middle 13th or early 15th centuries the middle 17th and the last half of the 19th century a d strong synchrony of these events across coastal alaska is evident 2000 elsevier science ltd all rights reserved

applications of autoregressive models and time frequency analysis to the study of volcanic tremor and long period events volcanic tremor and long period lp events are characterized by sharp spectral peaks that generally result from resonance effects at the source and which concentrate most of the radiated energy the understanding of these seismovolcanic phenomena requires good descriptions of the distribution in time and frequency of the different spectral components included in the signals as well as a separation of the resonance effects from less energetic effects such as excitation and propagation we address the issue of extracting from individual records information as detailed as possible on the physical processes involved at the source we introduce and compare several time frequency analysis methods and we describe the application of autoregressive modeling and deconvolution methods to the characterization and separation of the main spectral components we propose a signal analysis approach based on the joint use of a set of complementary methods and we present applications to several examples of volcanic tremor and lp events the time frequency analysis of some of the lp events taken as examples reveals short duration components at the seismogram onsets with energy concentrated at frequencies either higher or lower than the main resonance frequencies these seismic phases are probably related to the excitation processes of the volcanic resonators in several cases the arrival of the main spectral peak has a delay of a few tenths of a second with respect to the first arrival the residual signals obtained by deconvolving and eliminating the main spectral components contain information about the excitation such as duration delay or frequency band the residual signals are short for lp events and continuous for volcanic tremor the autoregressive modeling of the sample records gives precise estimations of the frequency and quality factor of the main spectral peaks the measured parameters cover a wide range of values which is consistent with the great variety of fluids filling resonating cavities in volcanoes

late pleistocene and holocene paleoenvironments of the north pacific coast abstract unlike the north atlantic the north pacific ocean probably remained free of sea ice during the last glacial maximum lgm 22 000 to 17 000 bp following a eustatic low in sea level of ca 120 m at 19 000 bp a marine transgression had flooded the bering and chukchi shelves by 10 000 bp post glacial sea level history varied widely in other parts of the north pacific coastline according to the magnitude and timing of local tectonism and glacio isostatic rebound glaciers covered much of the continental shelf between the alaska peninsula and british columbia during the lgm maximum glacier extent during the lgm was out of phase between southern alaska and southern british columbia with northern glaciers reaching their outer limits earlier between 23 000 and 16 000 bp compared to 15 000 14 000 bp in the south glacier retreat was also time transgressive with glaciers retreating from the continental shelf of southern alaska before 16 000 bp but not until 14 000 13 000 bp in southwestern british columbia major climatic transitions occurred in the north pacific at 24 000 22 000 15 000 13 000 and 11 000 9000 bp rapid climate changes occurred within these intervals including a possible younger dryas episode an interval of climate warmer and drier than today occurred in the early holocene cooler and wetter conditions accompanied widespread neoglaciation beginning in some mountain ranges as early as the middle holocene but reaching full development after 3000 bp

tide gauge records of uplift along the northern pacific north american plate boundary 1937 to 2001 1 vertical crustal motions at 15 sites along the northern pacific north america plate boundary are determined using relative sea level changes from tide gauge records our analysis is based on monthly mean sea levels from which barometric pressure and seasonal effects are removed the records are corrected for common mode oceanographic variations these records are statistically examined for non linear behavior related to glacial isostatic tectonic and postseismic effects to estimate land uplift rates the local effect of global sea level rise is removed from the relative sea level rates slow rates of vertical motion are observed along the southern strike slip plate boundary the extremely rapid uplift of the northern strike slip boundary can be attributed entirely to viscoelastic postglacial rebound associated with tidewater glacier retreat in glacier bay and regional post little ice age deglaciation isostatic modeling indicates a mantle viscosity of 2 1019 5 1019 pa s similar to that found elsewhere along the pacific north america plate margin at yakutat near the transition of plate motion from strike slip to subduction complex non linear behavior is evident with a significant change in uplift rate following the 1979 st elias earthquake non linear uplift rates are predominant within the 1964 great alaskan earthquake near field rapid uplift at kodiak during a 3 5 year period starting mid 1964 totaled 47 8 cm anchorage seward and seldovia exhibited oscillatory uplift in the period immediately following the earthquake until mid 1972 since mid 1972 uplift rates have increased steadily at anchorage seward cordova and valdez during this period nikiski and kodiak show decreasing uplift rates

late holocene high resolution glacial chronologies and climate kenai mountains alaska recent retreat of outlet glaciers from the harding and grewingk yalik icefields has revealed a vast array of deposits on the eastern and western flanks of the kenai mountains that records multiple glacier advances into coastal forests during late holocene time treering dating together with radiocarbon and lichenometric analyses allows for the reconstruction of these glacial fluctuations to decadal precision over the past two thousand years the records of fluctuations are derived from 16 land terminating and seven tidewater glaciers in three fjord systems as well as two cirque glaciers three major intervals of holocene glacier expansions are evident they occurred about 3600 yr b p 600 a d and during the little ice age from 1300 to 1850 a d the earliest expansion beyond present ice margins is known only from the mccarty tidewater glacier the 600 a d event involved the simultaneous advance of land terminating and tidewater glaciers during the little ice age however tidewater glaciers were advancing several centuries prior to their land terminating neighbors those land terminating glaciers on the western mountain flank retreated from their little ice age maxima as much as two centuries before those on the eastern mountain flank land terminating tongues on the eastern more maritime mountain flank have shown more sensitivity to variations in winter precipitation during the little ice age and within recent decades than the more continental glaciers on the western flank that are affected more by summer temperatures the glacial and climatic records suggest that advances of the ice tongues from about 1420 to 1460 a d between 1640 and 1670 a d at about 1750 a d and from 1880 to 1910 a d reflected times of increased winter precipitation advances between 1440 to 1460 a d from 1650 to 1710 a d and from 1830 to 1860 a d followed intervals of lower summer temperatures

neural forecasting of seismicity and ground displacements in different volcanic areas abstract volcanic events have been up to now traditionally predicted through deterministic or probabilistic linear methods here a new non linear approach is carried out based on artificial neural networks ann a non linear physical mathematical model to interconnect data emulating animal brain behaviour being an artificial intelligence system this model is able once both the observed data records and starting values of the network s parameters have been entered to self guide itself and supply the best outputs with respect to the input parameters on varying the starting values the exit values change too the degree of improvement being measurable quantitatively this model has been applied to four different volcanoes vesuvius phlegraean fields etna hawaii with different volcanic characteristics in order to measure the effectiveness of the method as a general one for this purpose data regarding seismicity or ground displacements vertical radial tangential components were processed and predicted by means of ann the results are encouraging and in many cases in very fair agreement with the observed data

dendrochronology and late holocene history of bering piedmont glacier alaska fluctuations of the piedmont lobe of bering glacier and its sublobe steller glacier over the past two millennia are reconstructed using 34 radiocarbon dates and tree ring data from 16 sites across the glaciers forelands the general sequence of glacial activity is consistent with well dated fluctuations of tidewater and land terminating glaciers elsewhere along the gulf of alaska extensive forested areas along 25 km of the bering ice margin were inundated by glacio lacustrine and glacio fluvial sediments during a probable ice advance shortly before 500 cal yr a d regrowth of forests followed the retreating ice as early as the 7th century a d with frequent interruptions of tree growth due to outwash aggradation forests overrun by ice and buried in outwash indicate readvance about 1080 cal yr a d retreat followed with ice free conditions maintained along the distal portions of the forefield until the early 17th century after which the ice advanced to within a few kilometers of its outer neoglacial moraine ice reached this position after the mid 17th century and prior to 200 yr ago since the early 20th century glacial retreat has been punctuated by periodic surges the record from forests overrun by the nonsurging steller lobe shows that this western ice margin was advancing by 1250 a d reaching near its outer moraine after 1420 cal yr a d since the late 19th century the lobe has dominantly retreated

real time seismic amplitude measurement rsam a volcano monitoring and prediction tool seismicity is one of the most commonly monitored phenomena used to determine the state of a volcano and for the prediction of volcanic eruptions although several real time earthquake detection and data acquisition systems exist few continuously measure seismic amplitude in circumstances where individual events are difficult to recognize or where volcanic tremor is prevalent analog seismic records provide a quick visual overview of activity however continuous rapid quantitative analysis to define the intensity of seismic activity for the purpose of predicing volcanic eruptions is not always possible because of clipping that results from the limited dynamic range of analog recorders at the cascades volcano observatory an inexpensive 8 bit analog to digital system controlled by a laptop computer is used to provide 1 min average amplitude information from eight telemetered seismic stations the absolute voltage level for each station is digitized averaged and appended in near real time to a data file on a multiuser computer system raw realtime seismic amplitude measurement rsam data or transformed rsam data are then plotted on a common time base with other available volcano monitoring information such as tilt changes in earthquake activity associated with dome building episodes weather and instrumental difficulties are recognized as distinct patterns in the rsam data set rsam data for domebuilding episodes gradually develop into exponential increases that terminate just before the time of magma extrusion mount st helens crater earthquakes show up as isolated spikes on amplitude plots for crater seismic stations but seldom for more distant stations weather related noise shows up as low level long term disturbances on all seismic stations regardless of distance from the volcano implemented in mid 1985 the rsam system has proved valuable in providing up to date information on seismic activity for three mount st helens eruptive episodes from 1985 to 1986 may 1985 may 1986 and october 1986 tiltmeter data the only other telemetered geophysical information that was available for the three dome building episodes is compared to rsam data to show that the increase in rsam data was related to the transport of magma to the surface thus if tiltmeter data is not available rsam data can be used to predict future magmatic eruptions at mount st helens we also recognize the limitations of rsam data two examples of rsam data associated with phreatic or shallow phreatomagmatic explosions were not preceded by the same increases in rsam data or changes in tilt associated with the three dome building eruptions

pattern recognition applied to seismic signals of the llaima volcano chile an analysis of the events features abstract this paper proposes a computer based classifier to automatically identify four seismic event classes of the llaima volcano one of the most active volcanoes in the southern andes situated in the araucania region of chile a combination of features that provided good recognition performance in our previous papers concerning the llaima and villarica located 100 km south of llaima volcanoes is utilized in order to train the classifiers these features are extracted from the amplitude frequency and phase of the seismic signals unlike the previous works where fixed length windows were used to obtain the seismic signals this paper employs signals of variable lengths that span the entire seismic event the classifiers are implemented using support vector machines a confidence analysis is also included to improve reliability of the classification results indicate that the features used for recognition of the events of villarica volcano also provide good recognition results for the llaima volcano yielding classification exactitude of over 80

ice front variation and tidewater behavior on helheim and kangerdlugssuaq glaciers greenland we used satellite images to examine the calving behavior of helheim and kangerdlugssuaq glaciers greenland from 2001 to 2006 a period in which they retreated and sped up these data show that many large iceberg calving episodes coincided with teleseismically detected glacial earthquakes suggesting that calving related processes are the source of the seismicity for each of several events for which we have observations the ice front calved back to a large pre existing rift these rifts form where the ice has thinned to near flotation as the ice front retreats down the back side of a bathymetric high which agrees well with earlier theoretical predictions in addition to the recent retreat in a period of higher temperatures analysis of several images shows that helheim retreated in the 20th century during a warmer period and then re advanced during a subsequent cooler period this apparent sensitivity to warming suggests that higher temperatures may promote an initial retreat off a bathymetric high that is then sustained by tidewater dynamics as the ice front retreats into deeper water the cycle of frontal advance and retreat in less than a century indicates that tidewater glaciers in greenland can advance rapidly greenland s larger reservoir of inland ice and conditions that favor the formation of ice shelves likely contribute to the rapid rates of advance

a 1119 year tree ring width chronology from western prince william sound southern alaska living and subfossil trees from glacier forefields are used to develop a 1119 year long tree ringwidth chronology strong cross dating among ring width series from sites up to 60 km apart and an analysis of sample homogeneity support combination of all samples into a single regional composite chronology comparison with instrumental climate data indicates may through july temperatures of the growth year are the primary control on ring widths multidecadal length warm periods in western prince william sound during the past 800 years were centred on ad 1300 1440 and possibly 1820 multidecadal length cool periods were centred on ad 1400 1660 and 1870 this is the first tree ring chronology from the gulf of alaska region to extend into the first millennium ad

little ice age glacial activity in the mt waddington area british columbia coast mountains canada the establishment of fourteen little ice age lia glacier chronologies in the mt waddington area led to the development of an extended history of glacial activity in this portion of the southern british columbia coast mountains canada the glaciers were located within four different mountain ranges and were of varying size and aspect dendrochronological and lichenometric techniques were used to provide relative age estimates of moraines formed as glacier termini retreated from advanced positions evidence for pre lia glacial events is best preserved at tiedemann glacier where the oldest glacial advances date to a d 620 and 925 933 soil covered and well vegetated moraines built at cathedral pagoda and siva glaciers date to between a d 1203 and 1226 following this event moraines constructed at ragnarok siva and cathedral glaciers in the mid 14th century suggest glaciers in the region underwent a period of downwasting and retreat before readvancing the majority of moraines recorded in the mt waddington area describe late lia glacial events shown to have constructed moraines that date to a d 1443 1458 1506 1524 1562 1575 1597 1621 1657 1660 1767 1784 1821 1837 1871 1900 1915 1928 and 1942 1946 over the last 500 years these moraine building episodes were shown to occur on average every 65 years and suggest there has been prolonged synchronicity in the glaciological response to persistent climate forcing mechanisms nevertheless our analysis suggests that local factors such as aspect and size play an important role in individual glacial response notably ice termini of medium size glaciers facing eastwards showed a quicker response to climatically induced mass balance changes resume l historique de quatorze glaciers de vallee de la region du mont waddington sud de la chaine cotiere de colombie britannique canada durant le petit ge glaciaire pag fut evalue par l utilisation de techniques dendrochronologiques et lichenometriques procurant un ge minimum pour la formation des moraines laterales et frontales multiples les glaciers a l etude d aspect et de taille differents furent selectionnes a partir de quatre chaines de montagnes les evenements qui predatent le pag sont le mieux preserves sur le site du glacier tiedemann ou les plus vieilles avancees glaciaires date de a d 620 et 925 933 des moraines presentant une pedogenese avancee et recouvertes d une dense couverture vegetale furent datees entre a d 1203 et 1226 des moraines construites dans le milieu du 14 e siecle par les glaciers ragnarok siva et cathedral suggerent que les glaciers de la region se sont retires pour par la suite reavancer la majorite des moraines datees le furent vers la fin du pag soit en a d 1443 1458 1506 1524 1562 1575 1597 1621 1657 1660 1767 1784 1821 1837 1871 1900 1915 1928 et 1942 1946 au cours des 500 dernieres annees en moyenne 65 annees separent les differents episodes glaciaires ce qui suggerent un synchronisme des reponses glaciaires aux mecanismes climatiques des donnees preliminaires suggerent que l orientation et la taille des glaciers jouent un role important dans la reponse individualiste des glaciers en fait les terminus glaciaires des moyens glaciers d orientation est semblent repondre plus rapidement a un ajustement de volume interne glaciaire

holocene optimum events inferred from subglacial sediments at tschierva glacier eastern swiss alps abstract this study investigates the subglacial sedimentary archive at tschierva glacier eastern swiss alps subfossil wood remains found at the retreating glacier tongue indicate that their emergence results from recent transport from an upvalley basin a confluence basin like structure was found to exist by georadar measurements underneath the present glacier in combination with high resolution age determinations based on dendrochronology and radiocarbon dating it is implied that a retreated tschierva glacier allowed vegetation growth and sediment accumulation in that basin three periods of glacier recession were detected which occurred around 9200 cal yr bp from 7450 to 6650 cal yr bp and from 6200 to 5650 cal yr bp these periods are called holocene optimum events hoe accordingly an equilibrium line rise 220 m compared to the reference period from 1960 to 1985 was inferred from digital elevation models of former glacier extents since glacier mass balance depends on summer june july august temperature and precipitation an equilibrium line altitude ela rise of 220 m implies a summer temperature increase of about 1 8 c assuming unchanged precipitation during the dated hoe alternative calculations point to probable temperature increase in a broad interval between 1 0 c taking into account a precipitation change of 250 mm a to 2 5 c with 250 mm a precipitation change supporting earlier paleotemperature estimates it is proposed that higher mean summer insolation caused a stronger seasonality during the mid holocene as compared to late holocene conditions

pattern and forcing of northern hemisphere glacier variations during the last millennium time series depicting mountain glacier fluctuations in the alps display generally similar patterns over the last two centuries as do chronologies of glacier variations for the same interval from elsewhere in the northern hemisphere episodes of glacier advance consistently are associated with intervals of high average volcanic aerosol production as inferred from acidity variations in a greenland ice core advances occur whenever acidity levels rise sharply from background values to reach concentrations 1 2 equiv h kg above background a phase lag of about 10 15 yr equivalent to reported response lags of alpine glacier termini separates the beginning of acidity increases from the beginning of subsequent ice advances a similar relationship but based on limited and less reliable historical data and on lichenometric ages is found for the preceding 2 centuries calibrated radiocarbon dates related to advances of non calving and non surging glaciers during the earlier part of the little ice age display a comparable consistent pattern an interval of reduced acidity values between about 1090 and 1230 a d correlates with a time of inferred glacier contraction during the medieval optimum the observed close relation between noothern hemisphere glacier fluctuations and variations in greenland ice core acidity suggests that sulfur rich aerosols generated by volcanic eruptions are a primary forcing mechanism of glacier fluctuations and therefore of climate on a decadal scale the amount of surface cooling attributable to individual large eruptions or to episodes of eruptions is simlar to the probable average temperature reduction during culminations of little ice age alacier advances ca 0 5 1 2 c as inferred from depression of equilibrium line altitudes

classification of seismic signals at villarrica volcano chile using neural networks and genetic algorithms each volcano has its own unique seismic activity the aim of this work is to construct a system able to classify seismic signals for the villarrica volcano one of the most active volcanoes in south america since seismic signals are the result of particular processes inside the volcano s structure they can be used to forecast volcanic activity this paper describes the different kinds of seismic signals recorded at the villarrica volcano and their significance three kind of signals were considered as most representative of this volcano s activity the long period the tremor and the energetic tremor signals a classifier is implemented to read the seismic registers at 30 second intervals extract the most relevant features of each interval and classify them into one of the three kinds of signals considered as most representative of this particular volcano to do so 1033 different kinds of 30 s signals were extracted and classified by a human expert a feature extraction process was applied to obtain the main characteristics of each of them this process was developed using criteria which have been shown by others to effectively classify seismic signals based on the experience of a human expert the classifier was implemented with a multi layer perceptron mlp artificial neural network whose architecture and training process were optimized by means of a genetic algorithm this technique searched for the most adequate mlp configuration to improve the classification performance optimizing the number of hidden neurons the transfer functions of the neurons and the training algorithm the optimization process also performed a feature selection to reduce the number of signal features optimizing the number of network inputs the results show that the optimized classifier reaches more than 93 exactitude identifying the signals of each kind the amplitude of the signals is the most important feature for its classification followed by its frequency content the described methodology can be used to classify more seismic signals to improve the study of the activity of this volcano or to extend the study to other active volcanoes of the region

a deglacial and holocene record of climate variability in south central alaska from stable oxygen isotopes and plant macrofossils in peat we used stable oxygen isotopes derived from bulk peat d 18 otom in conjunction with plant macrofossils and previously published carbon accumulation records in a w14 500 cal yr bp peat core ht fen from the kenai lowlands in south central alaska to reconstruct the climate history of the area we find that patterns are broadly consistent with those from lacustrine records across the region and agree with the interpretation that major shifts in d 18 otom values indicate changes in strength and position of the aleutian low al a semi permanent low pressure cell that delivers winter moisture to the region we find decreased strength or a more westerly position of the al relatively higher d 18 otom values during the bolling allerod holocene thermal maximum htm and late holocene which also correspond to warmer climate regimes these intervals coincide with greater peat preservation and enhanced carbon c accumulation rates at the ht fen and with peatland expansion across alaska the htm in particular may have experienced greater summer precipitation as a result of an enhanced pacific subtropical high a pattern consistent with modern d 18 o values for summer precipitation the combined warm summer temperatures and greater summer precipitation helped promote the observed rapid peat accumulation a strengthened al relatively lower d 18 otom values is most evident during the younger dryas neoglaciation and the little ice age consistent with lower peat preservation and c accumulation at the ht fen suggesting less precipitation reaches the leeward side of the kenai mountains during periods of enhanced al strength the peatlands on the kenai peninsula thrive when the al is weak and the contribution of summer precipitation is higher highlighting the importance of precipitation seasonality in promoting peat accumulation this study demonstrates that d 18 otom values in peat can be applied

late holocene vegetation and climate change at moraine bog tiedemann glacier southern coast mountains british columbia moraine bog lies just outside the outermost lateral moraine of tiedemann glacier in the southern coast mountains of british columbia a sediment core taken from the wetland was analyzed for pollen magnetic susceptibility and loss on ignition to reconstruct changes in vegetation and climate during the late holocene vegetation changed little between about 3500 and 2400 14 c years bp a period of local disturbance marked by deposition of a silty clay bed and increases in alnus pollen likely reflecting cooler moister conditions coincides with an extensive holocene advance of tiedemann glacier about 2400 14 c years bp warm dry conditions between about 1900 and 1500 14 c years bp are sug gested by peak values of pseudotsuga pollen and increasing nuphar sclereids the latter suggests lowered water levels this period coincides with a time of drought and increased fire frequency in the southernmost coast mountains about 1300 14 c years bp the forest became more coastal in composition with abundant tsuga heterophylla and abies a n increase in tsuga mertensiana pollen suggests the onset of cool and wet conditions by ca 500 14 c years bp coincident with the little ice age the record of inferred climate change at moraine bog is broadly synchronous with other paleoclimate records from the coast mountains and at the centennial scale with records elsewhere in the world

a 1000 yr record of forest fire activity from eclipse icefield yukon canada a 1000 yr record of forest fire activity has been developed using three annually dated ice cores from eclipse icefield yukon canada forest fire signals were identified as nh4 residuals above a robust spline and corroborated by an empirical orthhogonal function eof analysis that identified a chemical association in the nh4 c 2o4 and k records similar to that observed in forest fire plumes these statistical techniques yielded similar records of forest fire activity although the eof analysis provides more conservative identification of forest fire signals comparison of forest fire signals in the eclipse ice cores with the record of annual area burned in alaska and the yukon demonstrates that 80 of high fire years in alaska and 79 of high fire years in the yukon are identifiable as nh4 concentration residuals in at least one core from eclipse icefield although any individual core records 36 67 of these events the eclipse ice cores record high fire activity in the ad 1760s 1780s 1840s 1860s 1880s 1890s 1920s 1940s and 1980s peak fire activity occurred in the 1890s possibly reflecting anthropogenic ignition sources associated with the large influx of people to the yukon during the klondike gold rush periods of low fire activity are evident during the 1770s 1810s 1830s 1850s 1950s and 1960s extending our proxy of fire activity to ad 1000 using annual nh4 concentrations from our one core that extends back this far provides evidence of high fire activity from 1240 to 1410 during the waning stages of the mediaeval warm period

automatic classification and a posteriori analysis of seismic event identification at soufriere hills volcano montserrat abstract seismic energy radiation at soufriere hills volcano montserrat is made up by various types of transient signals which are distinguished by the montserrat volcano observatory mvo in different classes with respect to their characteristics and or origin there are five fundamental classes i e volcano tectonic events regional events long period events hybrid events and rockfalls identification and classification of these transients which have been hitherto carried out manually by various staff members yield important information for the assessment of the state of the volcano system in the frame of the multimo project we proposed the application of artificial neural networks ann for the classification of these kind of data in order to handle large data sets and to achieve reproducible results emulating the expert s analysis using the manual routine classification as a priori information we obtained a fair performance of such an automatic processing with 70 of the automatic classifications being consistent with the original ones from an analysis of the misclassified events however we found that for most of them the original a priori classification was incorrect in this study we first revised manually the original a priori classification based on a data set of 6000 events we carried out a reanalysis of the seismic traces recorded at different seismic stations then using this new information we trained and tested the ann obtaining a successful classification in ca 80 of records particularly the automatic classification was excellent in the identification of rockfalls and volcano tectonic events among the misfits we observe the erroneous attribution of long period and hybrid events to rockfalls this may be partly explained by the fact that signals addressed to as rockfalls contain frequently contributions of various sources overall the failure in the classification between some types of transients highlights the problem of the concurrent activation and or unclear separation of distinctive sources from which the signals stem we conclude that the automatic classification with ann is a powerful tool for handling large data masses as well as for the a posterior analysis of the consistency of the classification problem

tree ring based reconstructions of north american glacier mass balance through the little ice age contemporary warming transition abstract glacier mass balance reconstructions provide a means of placing relatively short observational records into a longer term context in western north america mass balance records span four to five decades and capture a relatively narrow window of glacial behavior over an interval that was dominated by warming and ablation we use temperature and moisture sensitive tree ring series to reconstruct annual mass balance for six glaciers in the pacific northwest and alaska mass balance models rely on the climatic sensitivity of tree ring chronologies and teleconnection patterns in the north pacific the reconstructions extend through the mid to latter portions of the little ice age lia and explore the role of climate variability in forcing mass balance across multiple environmental gradients synchronous positive mass balance intervals coincide with regional moraine building and solar minima whereas differences in lia glacier behavior are related to synoptic climate forcing secular warming in the late 19th century to present corresponds with the only multi decadal intervals of negative mass balance in all glacier reconstructions this suggests that contemporary retreat in western north america is unique with respect to the last several centuries and that regional patterns of glacier variability are now dominated by global climate forcing

expansion of outlet glaciers of the juneau icefield in northwest british columbia during the past two millennia radiocarbon and dendrochronological dating of glacially overridden stumps and detrital wood indicates that two outlet glaciers of the juneau icefield advanced shortly before the little ice age tulsequah glacier advanced to within 2 4 km of its all time holocene limit between ad 865 and ad 940 llewellyn glacier one of the largest glaciers in british columbia advanced sometime between ad 300 and ad 500 and reached to within 400 m of its holocene limit between ad 1035 and ad 1210 well before the climactic classical little ice age advances of the past several centuries our data show that some glaciers in western north america were extensive and expanding at times when alpine glaciers have in the past been assumed to be restricted the evidence raises questions about how to define the time of the beginning of the little ice age and perhaps more importantly about the utility of the term

a 2000 yr long multi proxy lacustrine record from eastern baffin island arctic canada reveals first millennium ad cold period abstract we generate a multi proxy sub centennial scale reconstruction of environmental change during the past two millennia from itilliq lake baffin island arctic canada our reconstruction arises from a finely subsectioned 210pb and 14c dated surface sediment core and includes measures of organic matter e g chlorophyll a carbon nitrogen ratio and insect diptera chironomidae assemblages within the past millennium the least productive and by inference coldest conditions occurred ca ad 1700 1850 late in the little ice age the 2000 yr sediment record also reveals an episode of reduced organic matter deposition during the 6th 7th century ad combined with the few other records comparable in resolution that span this time interval from baffin island we suggest that this cold episode was experienced regionally a comparable cold climatic episode occurred in alaska and western canada at this time suggesting that the first millennium ad cold climate anomaly may have occurred throughout the arctic dramatic increases in aquatic biological productivity at multiple trophic levels are indicated by increased chlorophyll a concentrations since ad 1800 and chironomid concentrations since ad 1900 both of which have risen to levels unprecedented over the past 2000 yr

palaeohydrology of the southwest yukon territory canada based on multiproxy analyses of lake sediment cores from a depth transect lake level variations at marcella lake a small hydrologically closed lake in the southwestern yukon territory document changes in effective moisture since the early holocene former water levels driven by regional palaeohydrology were reconstructed by multiproxy analyses of sediment cores from four sites spanning shallow to deep water marcella lake today is thermally stratified being protected from wind by its position in a depression it is alkaline and undergoes bio induced calcification relative accumulations of calcium carbonate and organic matter at the sediment water interface depend on the location of the depositional site relative to the thermocline we relate lake level fluctuations to down core stratigraphic variations in composition geochemistry sedimentary structures and to the occurrence of unconformities in four cores based on observations of modern limnology and sedimentation processes twenty four ams radiocarbon dates on macrofossils and pollen provide the lake level chronology prior to 10 000 cal bp water levels were low but then they rose to 3 to 4 m below modern levels between 7500 and 5000 cal bp water levels were 5 to 6 m below modern but rose by 4000 cal bp between 4000 and 2000 cal bp they were higher than modern during the last 2000 years water levels were either near or 1 to 2 m below modern levels marcella lake water level fluctuations correspond with previously documented palaeoenvironmental and palaeoclimatic changes and provide new independent effective moisture information the improved geochronology and quantitative water level estimates are a framework for more detailed studies in the southwest yukon

identification of new events in apollo 16 lunar seismic data by hidden markov model based event detection and classification detection and identification of interesting events in single station seismic data with little prior knowledge and under tight time constraints is a typical scenario in planetary seismology the apollo lunar seismic data with the only confirmed events recorded on any extraterrestrial body yet provide a valuable test case here we present the application of a stochastic event detector and classifier to the data of station apollo 16 based on a single waveform example for each event class and some hours of background noise the system is trained to recognize deep moonquakes impacts and shallow moonquakes and performs reliably over three years of data the algorithm s demonstrated ability to detect rare events and flag previously undefined signal classes as new event types is of particular interest in the analysis of the first seismic recordings from a completely new environment we are able to classify more than 50 of previously unclassified lunar events and additionally find over 200 new events not listed in the current lunar event catalog these events include deep moonquakes as well as impacts and could be used to update studies on temporal variations in event rate or deep moonquakes stacks used in phase picking for localization no unambiguous new shallow moonquake was detected but application to data of the other apollo stations has the potential for additional new discoveries 40 years after the data were recorded besides the classification system could be useful for future seismometer missions to other planets e g the insight mission to mars

automatic identification of rockfalls and volcano tectonic earthquakes at the piton de la fournaise volcano using a random forest algorithm abstract monitoring the endogenous seismicity of volcanoes helps to forecast eruptions and prevent their related risks and also provides critical information on the eruptive processes due the high number of events recorded during pre eruptive periods by the seismic monitoring networks cataloging each event can be complex and time consuming if done by human operators automatic seismic signal processing methods are thus essential to build consistent catalogs based on objective criteria we evaluated the performance of the random forests rf machine learning algorithm for classifying seismic signals recorded at the piton de la fournaise volcano la reunion island france we focused on the discrimination of the dominant event types rockfalls and volcano tectonic earthquakes using over 19 000 events covering two time periods 2009 2011 and 2014 2015 we parametrized the seismic signals using 60 attributes that were then given to rf algorithm when the rf classifier was given enough training samples its sensitivity rate of good identification exceeded 99 and its performance remained high above 90 even with few training samples the sensitivity collapsed when using an rf classifier trained with data from 2009 to 2011 to classify data from 2014 to 2015 catalog because the physical characteristics of the rockfalls and hence their seismic signals had evolved between the two time periods the main attribute families waveform spectrum spectrogram or polarization were all found to be useful for event discrimination our work validates the performance of the rf algorithm and suggests it could be implemented at other volcanic observatories to perform automatic near real time classification of seismic events

late holocene glacial history of scimitar glacier mt waddington area british columbia coast mountains canada scimitar glacier originates below the northeast face of mt waddington in the southern british columbia coast mountains and flows 18 km down valley to calve into a proglacial lake at several locations downwasting of the glacier surface has exposed stacked till units separated by wood bearing horizons in the proximal slopes of lateral moraines flanking the glacier historical moraine collapse and erosional breaching has also revealed the remains of standing trees buried in moraine dammed lake sediments radiocarbon and tree ring dating show that scimitar glacier expanded down valley at least three times in the late holocene the earliest evidence found for ice expansion indicates scimitar glacier was advancing in 3167 2737 cal years bp in association with the regional tiedemann advance following this advance the glacier downwasted prior to expanding in 1568 1412 cal years bp during the first millennial advance a final period phase of moraine construction was initiated during late little ice age glacia

seismic folding in coastal south central chile the great mw 9 3 valdivia earthquake of may 21 22 1960 was associated with ground deformation over a distance of over 800 km parallel to the peru chile trench downwarping by as much as 2 3 m affected a belt averaging a width of 100 km which was bordered by a major upwarped zone in the west where uplift locally attained 5 7 m and a minor upwarped zone in the east the deformation has been explained by thin viscous sheet models or by dislocation models involving predominantly dip slip movement on thrust faults we show that it can be modeled by elastic buckling of the overriding south american plate without the need to invoke specific fault geometries the proposed buckling mechanism accounts for both zones of upwarping and for the exceptionally rapid uplift experienced by mocha island to the west moreover elastic relaxation provides a simple explanation for the postseismic recovery reported by observers at several sites it is also consistent with the results obtained by 14c dating of fossil shorelines within and outside the area affected by the 1960 events which show that central and northern chile has undergone little uplift during the last 30 000 years despite convergence between the south american and nazca plates at over 90 mm yr although the presence of numerous older shorelines shows that coastal uplift was very active earlier in the cenozoic

reliability of a fjord glacier s fluctuations for paleoclimatic reconstructions abstract historical observations of fjord glaciers in southern alaska suggest that their fluctuations may be asynchronous with one another and with climate possible causes for anomalous fjord glacier response to climatic changes involve the instabilities inherent in a calving terminus the interaction of fjord geometry with the extent of the calving terminus and the intersection of low lying snow line by a thickening glacier the lituya glacier system in southeast alaska is analyzed with reference to these phenomena to test the reliability of its holocene glacial deposits as paleoclimatic records this fjord glacier is shown to have been probably free of major nonclimatic responses during the holocene except for an insensitive period of up to 1000 yr that followed calving retreats the insensitive period has no functional effect on how the relatively coarse geologic record is interpreted in terms of paleoclimate however it makes impossible any inference of climatic trends from this glacier s behavior in historical times fjord glacier deposits can be dependable records of paleoclimate but each glacier requires careful scrutiny anomalous glacier responses to climate are most likely to occur in fjords of complex geometry in regions of relatively low snow line and where glaciers terminate at fjord mouths bordering the open sea

rapid uplift of southern alaska caused by recent ice loss summary extreme uplift rates and sea level changes in southern alaska have been documented by global positioning system gps surveys tide gauge measurements and studies of raised shorelines the movements detected in a network of 45 gps survey points describe a broad pattern of rapid regional uplift the majority of the study area is uplifting at a rate faster than 10 mm yr 1 with several sites uplifting more rapidly than 25 mm yr 1 new tide gauge data presented here consist of repeat occupations of 18 temporary gauge sites sea level rates at these sites agree with similar measurements in southern alaska taken 50 yr earlier and also with the pattern of uplift derived from the gps data raised shoreline studies at 14 sites document total sea level change with a maximum change in sea level of 5 7 m found in upper lynn canal the start of the ongoing uplift episode that raised these shorelines has been dated with dendrochronology and found to be coincident with the start of the collapse of the glacier bay icefield at ca 1750 ad the pattern of total sea level change is in general agreement with upliftrate measurements with greater sea level change found at the sites closest to the peak uplift rates in upper glacier bay we use a viscoelastic earth model subjected to an ice load history built upon observations of glacial change to predict uplift rates at the tide gauge and gps sites as well as the total uplift at the raised shoreline sites our modelling exercises are limited to an ice load model based on independent studies of the region s glacial history over the past 1 7 kyr to evaluate whether the uplift observations can be explained by simple earth models subjected to this load history two layer earth models consisting of an elastic crust and a low viscosity upper mantle half space can be adjusted to fit either the raised shoreline data or the combined gps and tide gauge uplift rate data but cannot fit all the data with a single set of earth model parameters however all three data sets are consistent with an approximated three layer earth model the combined model is constrained by a total of 77 uplift measurements which at the 95 per cent confidence level require a low viscosity asthenosphere a 1 4 0 3 10 19 pa s and thickness 110 20

timing and climatic controls over neoglacial expansion in the northern coast mountains british columbia canada holocene sedimentary records from two lakes in white pass british columbia show that the onset of neoglacial sedimentation began c 2 ka cal bp prior to this time the lakes accumulated organicrich sediments with properties and sedimentation rates similar to adjacent lakes that have not had glacial influences during the holocene neoglaciation at white pass was coincident with the increased delivery of exotic tsuga heterophylla western hemlock pollen these results together with regional indications for increased delivery of hemlock pollen at 2 ka bp by a deepened low pressure in the northeastern pacific ocean suggest that increased moisture was important for the expansion of glaciers in the region in addition to longer term late holocene cooling

land sea linkage of holocene paleoclimate on the southern bering continental shelf detailed diatom records within surface and core sediments from the southern bering continental shelf sbcs reveal that the holocene evolution of sea ice distribution is associated with low pressure patterns holocene sea ice distribution over the sbcs was mainly controlled by the location of the aleutian low the corresponding paleoceanographic and paleoclimate conditions can be divided into three stages 1 the early holocene before 7000 cal yr bp was characterized by extensive sea ice distribution under two low pressure cells which covered the western bering sea and the gulf of alaska respectively 2 between 3000 and 7000 cal yr bp the low pressure system over the gulf of alaska became weak causing total sea ice mass over the sbcs to retreat 3 in the past 3000 years prevailing southwesterly winds over the sbcs due to the developing aleutian low have reduced further sea ice cover on the sbcs these paleoclimatic changes were probably a response to enso variation the timings of water mass exchanges on the sbcs coincided with sea level change along the alaskan peninsula as a result subsequent morphologic alterations have also influenced the paleoceanographic condition of the sbcs the effect of the surface coastal water and bottom marine water on the sbcs intensified about 6000 cal yr bp when sea level increased

dendroglaciological reconstruction of late holocene glacier activity at white and south flat glaciers boundary range northern british columbia coast mountains canada holocene glacier activity in the northern british columbia coast mountains canada is described following investigations in the recently deglaciated forefields of white and south flat glaciers spilling from the cambria icefield glacially overridden stumps and detrital wood was radiocarbon and dendrochronologically dated to describe an advance between ad 250 and 650 expansion and thickening of white glacier by ad 765 resulted in creation of an ice dammed lake in south flat valley that persisted until ad 1080 following this the lake drained before refilling in the early little ice age prior to ad 1300 shortly thereafter white and south flat glaciers became confluent and flowed over the valley side toward white lake the characteristics of the site and the preservation of 1500 yr old deposits indicate that the two glaciers remained confluent throughout the remainder of the little ice age only separating following terminal retreat early in the 20th century the late holocene glacial history of whit

tree ring dated little ice age histories of maritime glaciers from western prince william sound alaska tree ring studies at 13 glacier forefields in western prince william sound show little ice age glacial fluctuations were strongly synchronous on decadal timescales cross dated glacially overrun trees at eight sites indicate ice margins advanced in the early late twelfth through thirteenth centuries and middle seventeenth to early eighteenth centuries little ice age tree ring dates of 22 moraines at 13 glaciers show two main periods of stabilization the earlier of these in the first decades of the eighteenth century overlaps with the second period of glaciers overrunning trees and marks culmination of this middle little ice age expansion stabilization of moraines on nine of the study forefields in the latter part of the nineteenth century delineates a third interval of little ice age glacial advance the detailed little ice age record from land terminating glaciers in western prince william sound is consistent on a timescale of decades with four other tree ring dated glacial histories from across the northern gulf of alaska this coastal northeastern pacific glacial record reveals the structure of the little ice age in the region and provides a strong basis for comparison with other proxy climate records spanning the past 1000 years

a 1500 year record of temperature and glacial response inferred from varved iceberg lake southcentral alaska we present a varve thickness chronology from glacier dammed iceberg lake in the southern alaska icefields radiogenic evidence confirms that laminations are annual and record continuous sediment deposition from a d 442 to a d 1998 varve thickness is positively correlated with northern hemisphere temperature trends and more strongly with a local 600 yr long tree ring width chronology varve thickness increases in warm summers because of higher melt runoff and sediment transport as expected but also because shrinkage of the glacier dam allows shoreline regression that concentrates sediment in the smaller lake varve thickness provides a sensitive record of relative changes in warm season temperatures relative to the entire record temperatures implied by this chronology were lowest around a d 600 warm between a d 1000 and a d 1300 cooler between a d 1500 and a d 1850 and have increased dramatically since then combined with stratigraphic evidence that contemporary jokulhlaups which began in 1999 are unprecedented since at least a d 442 this record suggests that 20th century warming is more intense and accompanied by more extensive glacier retreat than the medieval warm period or any other time in the last 1500 yr

discriminating seismic events of the llaima volcano chile based on spectrogram cross correlations abstract the surveillance of active volcanoes around the world has become a critical security issue for many countries requiring a continuous monitoring of seismic signals by analyzing such signals we intend to understand volcanic activities e g explosions eruptions and depressurization and take decisions to reduce the effects and damages to the economy and society of nearby regions active volcanoes constantly produce signals which may then be characterized as data streams making impractical the presence of specialists to monitor and label every activity to overcome this drawback we present a new and straightforward approach to discriminate volcano seismic signals using spectrogram cross correlations spcc in conjunction with the k nearest neighbors algorithm a supervised machine learning strategy experiments were performed on signals collected from the llaima volcano chile and results confirmed the ability of our approach to discriminate events with a sensitivity over 95 for three out of the five classes considered

understanding the timing of eruption end using a machine learning approach to classification of seismic time series abstract the timing and processes that govern the end of volcanic eruptions are not yet fully understood and there currently exists no systematic definition for the end of a volcanic eruption currently end of eruption is established either by generic criteria typically 90 days after the end of visual signals of eruption or criteria specific to a given volcano we explore the application of supervised machine learning classification methods support vector machine logistic regression random forest and gaussian process classifiers and define a decisiveness index d to evaluate the consistency of the classifications obtained by these models we apply these methods to seismic time series from two volcanoes chosen because they display contrasting styles of eruption telica nicaragua and nevado del ruiz colombia we find that for both volcanic systems the end date we obtain by classification of seismic data is 2 4 months later than end dates defined by the last occurrence of visual eruption such as ash emission this finding is in agreement with previous general definitions of eruption end and is consistent across models our classifications have a higher correspondence of eruptive activity with visual activity than with database records of eruption start and end we analyze the relative importance of the different features of seismic activity used in our models e g peak event amplitude daily event counts and find little consistency between the two volcanic systems in terms of the most important features which determine whether activity is eruptive or non eruptive these initial results look promising and our approach may offer a robust tool to help determine when an eruption has ended in the absence of visual confirmation

spectro temporal features applied to the automatic classification of volcanic seismic events abstract feature extraction and selection are very relevant processes in the design of automatic classifiers in the context of volcanic seismic signal classification most of the features presented in the literature have been extracted separately from a single domain such as time or frequency however spectrograms which combine time and frequency information are widely used by experts during the classification of manual seismic events this paper proposes to evaluate the performance of classifiers trained with features extracted from the spectro temporal domain individually or combined with other conventional features the parameters were extracted from the spectrogram based on a curve which combines the high energy components and the frequency bandwidth information through the duration of the event the tests were performed at the llaima volcano and seismic events were classified into four classes long period tremor volcano tectonic and tectonic using a database of signals recorded between the years 2009 and 2017 the main achievements of this study were the reduction of more than 70 of the error and false positive rates and also a reduction of approximately 30 of the number of features compared with a baseline established in previous studies thus the inclusion of spectro temporal information was considered relevant to complement the conventional features and to support classification

peat accumulation in drained thermokarst lake basins in continuous ice rich permafrost northern seward peninsula alaska thermokarst lakes and peat accumulating drained lake basins cover a substantial portion of arctic lowland landscapes yet the role of thermokarst lake drainage and ensuing peat formation in landscape scale carbon c budgets remains understudied here we use measurements of terrestrial peat thickness bulk density organic matter content and basal radiocarbon age from permafrost cores soil pits and exposures in vegetated drained lake basins to characterize regional lake drainage chronology c accumulation rates and the role of thermokarst lake cycling in carbon dynamics throughout the holocene on the northern seward peninsula alaska most detectable lake drainage events occurred within the last 4 000 years with the highest drainage frequency during the medieval climate anomaly peat accumulation rates were highest in young 50 500 years drained lake basins 35 2 g c m 2 yr 1 and decreased exponentially with time since drainage to 9 g c m 2 yr 1 in the oldest basins spatial analyses of terrestrial peat depth basal peat radiocarbon ages basin geomorphology and satellite derived land surface properties normalized difference vegetation index ndvi minimum noise fraction mnf from landsat satellite data revealed significant relationships between peat thickness and mean basin ndvi or mnf by upscaling observed relationships we infer that drained thermokarst lake basins covering 391 km2 76 of the 515 km2 study region store 6 4 6 6 tg organic c in drained lake basin terrestrial peat peat accumulation in drained lake basins likely serves to offset greenhouse gas release from thermokarst impacted landscapes and should be incorporated in landscape scale c budgets

controls on advance of tidewater glaciers results from numerical modeling applied to columbia glacier 1 a one dimensional numerical ice flow model is used to study the advance of a tidewater glacier into deep water starting with ice free conditions the model simulates glacier growth at higher elevations followed by advance on land to the head of the fjord once the terminus reaches a bed below sea level calving is initiated a series of simulations was carried out with various boundary conditions and parameterizations of the annual mass balance the results suggest that irrespective of the calving criterion and accumulation rate in the catchment area it is impossible for the glacier terminus to advance into deeper water 300 m water depth unless sedimentation at the glacier front is included the advance of columbia glacier alaska is reproduced by the model by including conveyor belt recycling of subglacial sediment and the formation of a sediment bank at the glacier terminus results indicate slow advance through the deep fjord and faster advance in shallow waters approaching the terminal moraine shoal and the mouth of the fjord

signatures of the late holocene neoglacial cold event and their marine terrestrial linkage in the northwestern pacific margin marine microfossil assemblages in core sediments from the northern east china sea ecs were investigated to understand late holocene paleoclimatic changes in the northwestern pacific margin we find a pronounced alternation of ocean condition during the late holocene characterized by an abrupt decrease in dinoflagellate cysts and kuroshio water species of planktonic foraminifera centered at ca 4000 2500 14c yr bp compilation and merger of new and previously published data show that this oceanic event corresponds with terrestrial cooling and dry episodes in the northern china the synchronicity between marine and terrestrial records is considered to be linked to a weakened kuroshio influence that is in coupled with intensified winter monsoon highlighting a significance of oceanic atmospheric dynamics in determining moisture and heat distribution over both oceanic and terrestrial domains superimposed on the late holocene the synchronicity between this particular climatic shift in the northwestern pacific and the neoglacial cold events in the northern high latitude regions is tentatively indicative of a global climate signal possibly associated with dynamics of the north pacific gyre system and the high latitude north atlantic thermohaline circulation and therefore positions of the mean latitude of the kuroshio extension

automatic detection of alpine rockslides in continuous seismic data using hidden markov models data from continuously recording permanent seismic networks can contain information about rockslide occurrence and timing complementary to eyewitness observations and thus aid in construction of robust event catalogs however detecting infrequent rockslide signals within large volumes of continuous seismic waveform data remains challenging and often requires demanding manual intervention we adapted an automatic classification method using hidden markov models to detect rockslide signals in seismic data from two stations in central switzerland we first processed 21 known rockslides with event volumes spanning 3 orders of magnitude and station event distances varying by 1 order of magnitude which resulted in 13 and 19 successfully classified events at the two stations retraining the models to incorporate seismic noise from the day of the event improved the respective results to 16 and 19 successful classifications the missed events generally had low signal to noise ratio and small to medium volumes we then processed nearly 14 years of continuous seismic data from the same two stations to detect previously unknown events after postprocessing we classified 30 new events as rockslides of which we could verify three through independent observation in particular the largest new event with estimated volume of 500 000 m3 was not generally known within the swiss landslide community highlighting the importance of regional seismic data analysis even in densely populated mountainous regions our method can be easily implemented as part of existing earthquake monitoring systems and with an average event detection rate of about two per month manual verification would not significantly increase operational workload

holocene glaciation of alaska and adjoining yukon territory canada abstract holocene glacial fluctuations between arctic central interior and southern maritime alaska are broadly synchronous this synchrony is evident from a review of work in 11 study areas with varying numbers of glaciers 3 100 glacier types subpolar cirque temperate valley tidewater surging and dating methodologies the pattern is temporally and spatially consistent with vegetation data and generally with climatic deteriorations culminating in the little ice age early holocene glacial advances are confirmed for 7 6 5 8 lichen ka bp at 4 of 97 glaciers in the brooks range advances also occurred by 5 85 and 5 7 ka bp at separate glacier tongues in the northern alaska range at least by 6 5 ka bp in lituya bay and possibly also in the malaspina and aleutian islands areas a sharp increase in glacier activity began by 4 4 ka bp in the arctic and glacier bay areas and by about 3 ka bp major glacier advances probably were initiated or well underway throughout alaska during holocene glacial maxima ice filled glacier and lituya bays as well as fjords of prince william sound and massive moraines buried forests in the northeastern st elias mountains area minor recession is recorded directly or implied in most of alaska about 2 ka bp or locally through the following millennium subsequently distinct but locally weak advances occurred by about 1 2 ka bp in most areas again followed by intervals of glacier recession most pervasive and ubiquitous were the little ice age advances initiated about 700 bp these generally culminated in two major advances between about 400 and 50 bp in the arctic those of a d 1600 dominated those of the late 1800s in the gulf of alaska those of the middle 1700s or late 1800s dominated large scale asynchronous advances and retreats of calving tidewater glaciers have been recorded during the twentieth century but most such movements are only indirectly related to climate

century scale solar variability and alaskan temperature change over the past millennium 1 correlation of geologic histories from 130 alaskan glaciers with a record of solar variation suggests that multi decadal to century scale temperature variations in the north pacific and arctic sectors have been influenced by solar forcing over the past thousand years mountain glacier fluctuations are primarily a record of summer cooling and the composite glacial history from three climatic regions across alaska shows ice expansions approximately every 200 years compatible with a solar mode of variability the modulating effects of the cold phases of the pacific decadal oscillation and the arctic oscillation may when in phase with decreased solar activity serve to amplify cooling forcing glacier advance

calendar dated early little ice age glacier advance at robson glacier british columbia canada dendrochronological studies at robson and bennington glaciers have provided the first calendar dating of an early little ice age glacier advance in north america dates derived from in situ stumps indicate that robson glacier began over riding forest between c ad 1142 and 1150 and continued until at least ad 1350 the highest rates of glacier advance c 3 8 m yr 1 occurred between ad 1214 and 1261 based on a series of kill dates from in situ stumps between c ad 1142 1214 and 1261 1350 rates were somewhat lower at c 2 2 5 m yr 1 this glacier advance terminated upvalley of the little ice age maximum position of robson glacier and there is no evidence at this site for glacial events between ad 1350 and 1783 however two smaller glaciers in the robson area and the main tongue of small river glacier have outermost little ice age moraines that date from the first decades of the ad 1700s all glaciers examined in the mount robson area have several well developed moraines dating from the period c

new perspectives on beringian quaternary paleogeography stratigraphy and glacial history abstract aspects of the paleogeography stratigraphy and glacial history of beringia have been greatly revised over the past 15 20 yr access to north east russia in particular has provided the opportunity to evaluate the beringia landscape as a contiguous subcontinent during the quaternary for the first time new research has made clearer the connection between tectonic forces and the submergence of the bering strait during the middle pliocene revisions in the regional stratigraphy of glacial and interglacial deposits in northwest alaska and northeast russia provide a new foundation for assessing the causes for differences in glacial ice extent through time the consensus of all field workers verifies that glacial ice throughout most of beringia was of very limited extent during the last glacial maximum the onset of regional glaciation during the waning stages of the last interglaciation is clearly out of phase with glaciation at lower latitudes despite the lack of much glacial activity during the early holocene alaska contains a rich record of late holocene glacial response to neoglacial cooling changes in the holocene environment of beringia likely had a profound affect on early inhabitants the curiosity driven vision and spirit of both david hopkins and the late troy pewe have had a profound influence on arctic paleoenvironmental research

late quaternary paleoenvironments of northwestern north america implications for inland versus coastal migration routes abstract although the long held normative view of new world colonization relies on entrance through an interior ice free corridor by terrestrially adapted big game hunters a recently demonstrated human presence in southern chile dating prior to the existence of the corridor route implies different colonization scenarios which must be seriously considered a renewed focus of archaeological and paleoecological research on early post glacial landscapes in northwestern north america has revitalized the ice free vs coastal corridor controversy geological findings from glacial geology and paleo sea levels support the possibility of coastal migration from beringia to the pacific northwest between about 14 000 and 10 000 bp and preliminary paleoecological data suggest that the coastal landscape was in part vegetated and probably able to support a terrestrial fauna including humans the same cannot be said about the ice free corridor

evolving force balance at columbia glacier alaska during its rapid retreat 1 changes in driving and resistive stresses play an essential role in governing the buoyancy forces that are important controls on the speed and irreversibility of tidewater glacier retreats we describe changes in geometry velocity and strain rate and present a top down force balance analysis performed over the lower reach of columbia glacier our analysis uses new measurements and estimates of basal topography and photogrammetric surface velocity measurements made between 1977 and 2001 while assuming depth independent strain sensitivity tests show that the method is robust and insensitive to small changes in the calculation parameters spatial distributions of ice speed show little correspondence with driving stress instead spatial patterns of ice speed exhibit a nonlinear correspondence with basal drag primary resistance to flow comes from basal drag but lateral drag becomes increasingly more important throughout the retreat which may account for observed increases in speed maximum basal drag is always located in a prominent constriction located 12 km upstream from the preretreat terminus once the terminus retreated into deep water off the terminal moraine marking the modern maximum extent the upstream location of this maximum basal drag helped to promote thinning and decrease effective pressure in the lower region by limiting replenishing ice flow from upstream an increase in both ice velocity and calving resulted initiating what appears to be an irreversible retreat

constraints on regional drivers of relative sea level change around cordova alaska abstract new records of paleoenvironmental change from two lakes near cordova south central alaska combined with analysis of previously reported sediment sequences from the adjacent copper river delta provide quantitative constraints on a range of earth system processes through their expression in relative sea level change basal sediment ages from upper whitshed lake indicate ice free conditions by at least 14 140 15 040 cal yr bp while upper and lower whitshed lakes provide only upper limits to relative sea level change interbedded layers of freshwater peat and intertidal silt extending more than 11 m below present sea level in copper river delta indicate net submergence over the last 6000 years and multiple earthquake deformation cycles in contrast lower whitshed lake situated just above present high tide level records only one episode of marine sedimentation commencing ad 1120 1500 that we interpret as the result of isostatic subsidence due to little ice age mass accumulation of the chugach mountain glaciers lower whitshed lake also records isostatic uplift at the end of the little ice age before the end of marine sedimentation caused by 1 5 m coseismic uplift in the great alaska earthquake of ad 1964 we successfully explain the records of relative sea level change from both copper river delta and the whitshed lakes by integrating the effects of eustatic sea level rise glacial isostasy earthquake deformation cycles sediment loading sediment compaction and late holocene changes in glacier mass into a single model this approach provides initial quantitative constraints on the individual contributions of these processes taking reasonable estimates of eustasy post last glacial maximum and neoglacial glacial isostatic adjustment and a simple earthquake deformation cycle we demonstrate that sediment loading and sediment compaction are both contributors to relative sea level rise at copper river delta together producing subsidence averaging approximately 1 2 mm yr 1 over the mid to late holocene further isolation basin studies have the potential to greatly improve our understanding of the individual contributions of these processes in this highly dynamic region

fast tidewater glaciers some iceberg calving outlet glaciers flow continuously at speeds normally associated with surging glaciers arid exhibit dramatic instability scenarios related to those suggested for marine ice sheets no temperate tidewater glaciers are known to have floating termini but many polar and subpolar tidewater glaciers do the fast flow of temperate calving glaciers is almost entirely due to basal sliding and appears to be a function of the effective pressure on the bed which may approach zero and the longitudinal back stress on the terminus the terminus boundary condition the calving relation is imperfectly known yet is vital to the dynamics of these glaciers calving relations for grounded tidewater glaciers have been suggested on empirical grounds but have not been rigorously tested the calving relations for floating termini are virtually unknown this together with the imperfect understanding of basal sliding inhibits confidence in our understanding of the stability of these glaciers columbia glacier alaska is an instructive example because observations have been made on the major changes in its geometry calving rate and dynamics that have occurred in less than 10 years the calving flux has increased more rapidly than the glacier flux causing thinning and retreat as a result the ice velocity has increased markedly the short term velocity changes relate to changes in back pressure ice recession tidal changes and the flux of water injected to the bed these results have relevance to the mechanisms of basal sliding glacier surges and the stability of marine ice streams

villarrica volcano chile characteristics of the volcanic tremor and forecasting of small explosions by means of a material failure method villarrica volcano chile 39 42 s 71 93 w is one of the most active volcanoes in the andes it shows persistent strombolian activity in a small lava lake situated at the bottom of the summit crater from september to december 2000 the volcano exhibited anomalous behaviour after a regional tectonic seismic event on 22 september the eruption of a small volume of lava apparently plugged the conduit this situation then lasted for ten days on 5 and 8 october a series of explosions reopened the system this eruption behaviour has allowed us to study the evolution of the characteristic tremor in the open and closed states of the conduit a shift in the peak frequency from 1 hz open to 2 hz closed the explosions related to the opening of the conduit were forecasted by means of a material failure method

pattern recognition applied to seismic signals of llaima volcano chile an evaluation of station dependent classifiers abstract automatic pattern recognition applied to seismic signals from volcanoes may assist seismic monitoring by reducing the workload of analysts allowing them to focus on more challenging activities such as producing reports implementing models and understanding volcanic behaviour in a previous work we proposed a structure for automatic classification of seismic events in llaima volcano one of the most active volcanoes in the southern andes located in the araucania region of chile a database of events taken from three monitoring stations on the volcano was used to create a classification structure independent of which station provided the signal the database included three types of volcanic events tremor long period and volcano tectonic and a contrast group which contains other types of seismic signals in the present work we maintain the same classification scheme but we consider separately the stations information in order to assess whether the complementary information provided by different stations improves the performance of the classifier in recognising seismic patterns this paper proposes two strategies for combining the information from the stations i combining the features extracted from the signals from each station and ii combining the classifiers of each station in the first case the features extracted from the signals from each station are combined forming the input for a single classification structure in the second a decision stage combines the results of the classifiers for each station to give a unique output the results confirm that the station dependent strategies that combine the features and the classifiers from several stations improves the classification performance and that the combination of the features provides the best performance the results show an average improvement of 9 in the classification accuracy when compared with the station independent method