possible causes for the seismic activity observed in cotopaxi volcano ecuador continuous monitoring of cotopaxi volcano from january 1989 to september 1997 shows that it is subject to a steady shallow long period lp activity lp events are concentrated in a column with a diameter of about 3 km and a height of about 12 km between an elevation of 4 km and 8 km depth they do not occur in swarms nor have there been periods of complete calm high frequency volcano tectonic vt events are mostly located on the northeastern side of the lp column with the maximum activity of both types of events coinciding in depth lp activity cannot be related to unrest of the volcano the most likely explanation for the continuous occurrence of lp events beneath cotopaxi is that they are produced by the interaction of glacier thaw water and hot material at shallow depths the relative spatial distribution of both type of events in two adjacent zones suggest that vt and lp activities are interconnected

crustal structure evolution and volcanic unrest of the alban hills central italy the alban hills a quaternary volcanic center lying west of the central apennines 15 25 km southeast of rome last erupted 19 ka and has produced approximately 290 km3 of eruptive deposits since the inception of volcanism at 580 ka earthquakes of moderate intensity have been generated there at least since the roman age modern observations show that intermittent periods of swarm activity originate primarily beneath the youngest features the phreatomagmatic craters on the west side of the volcano results from seismic tomography allow identification of a low velocity region perhaps still hot or partially molten more than 6 km beneath the youngest craters and a high velocity region probably a solidified magma body beneath the older central volcanic construct thirty centimeters of uplift measured by releveling supports the contention that high levels of seismicity during the 1980s and 1990s resulted from accumulation of magma beneath these craters the volume of magma accumulation and the amount of maximum uplift was probably at least 40 106 m3 and 40 cm respectively comparison of newer levelings with those completed in 1891 and 1927 suggests earlier episodes of uplift the magma chamber beneath the western alban hills is probably responsible for much of the past 200 ka of eruptive activity is still receiving intermittent batches of magma and is therefore continuing to generate modest levels of volcanic unrest bending of overburden is the most likely cause of the persistent earthquakes which generally have hypocenters above the 6 km deep top of the magma reservoir in this view the most recent uplift and seismicity are probably characteristic and not precursors of more intense activity

seismic features of the june 1999 tectonic swarm in the stromboli volcano region italy abstract crustal tectonic seismicity in the southern tyrrhenian sea is characterized by the high occurrence rates of earthquakes to the west of the alignment of salina lipari and vulcano islands in the aeolian archipelago only a few earthquakes affect the crustal region east of these islands whereas intermediate and deep seismicity plays a relevant role based on this evidence two aspects of the seismic swarm recorded at the aeolian island seismic network between june 6 and 17 1999 looked anomalous the first aspect concerned the number of earthquakes 78 that affected the stromboli submarine edifice in a short time interval secondly despite the low maximum magnitude md 3 2 reached the cumulative strain release was conspicuous in comparison with previous swarms in this region we localized the swarm about 6 km northeast of stromboli at a depth between 8 and 12 km the source region was identified using standard methods of hypocentral location as well as azimuth analysis it is worth noting that the volcanic activity at stromboli did not change significantly during the swarm nor throughout the following months therefore the seismic swarm had no link with volcanic activity observed at the surface most of the earthquakes shared similar waveform and frequency content and can be divided into families we identified some earthquakes with magnitude up to md 3 having relatively low frequency content at different seismic stations this anomalous feature leads us to hypothesize the presence of fluid circulation and or propagation of seismic waves in a ductile medium our hypothesis is in agreement with studies on marine geology which highlight various forms of submarine volcanism in the southern basin of the tyrrhenian sea

improved 1d velocity model and deep long period earthquakes in kanlaon volcano philippines implications for its magmatic system abstract we determined an improved 1d p wave velocity model for kanlaon volcano one of the most active volcanoes in the philippines for use in precise earthquake relocation the inversion for velocity model was conducted using the program velest which solved the coupled hypocenter velocity problem from dataset of 251 local earthquakes recorded by the kanlaon volcano seismic network from 2014 to 2017 using the improved velocity model we relocated the volcano tectonic vt earthquakes in kanlaon with hypodd resulting in better constrained hypocenter locations based on the decrease in rms and corresponding error assessment tests subsequently we relocated swarms of long period volcanic earthquakes that occurred from september 1 2017 to august 31 2018 and prompted the philippine institute of volcanology and seismology to raise the volcano s alert level these long period earthquakes had emergent arrivals hence we applied a cross correlation procedure using redpy to obtain an improved arrival time picks these improved hypocenters revealed the existence of deep long period dlp earthquakes that occurred at depths of 23 to 36 km beneath the volcano these are the first dlp events documented in kanlaon since the establishment of the kanlaon volcano observatory in 1961 they were found to belong into families based on similarity of waveforms suggesting they were produced by repetitive non destructive sources the occurrences of dlps in kanlaon reflected the pressurization of its deep seated magmatic system their identification is critical in assessing the current state of kanlaon volcano especially since its last magmatic eruption was in 1902

geochemical evidence for a magmatic co2 degassing event at mammoth mountain california september december 1997 recent time series soil co2 concentration data from monitoring stations in the vicinity of mammoth mountain california reveal strong evidence for a magmatic degassing event during the fall of 1997 lasting more than 2 months two sensors at horseshoe lake first recorded the episode on september 23 1997 followed 10 days later by a sensor on the north flank of mammoth mountain direct degassing from shallow intruding magma seems an implausible cause of the degassing event since the gas released at horseshoe lake continued to be cold and barren of other magmatic gases except for he we suggest that an increase in compressional strain on the area south of mammoth mountain driven by movement of major fault blocks in long valley caldera may have triggered an episode of increased degassing by squeezing additional accumulated co2 from a shallow gas reservoir to the surface along faults and other structures where it could be detected by the co2 monitoring network recharge of the gas reservoir by co2 emanating from the deep intrusions that probably triggered deep long period earthquakes may also have contributed to the degassing event the nature of co2 discharge at the soil air interface is influenced by the porous character of high sierra soils and by meteorological processes solar insolation is the primary source of energy for the earth atmosphere and plays a significant role in most diurnal processes at the earth surface data from this study suggest that external forcing due largely to local orographic winds influences the fine structure of the recorded co2 signals

diversity taphonomy and behavior of encrusting foraminifera on experimental shells deployed along a shelf to slope bathymetric gradient lee stocking island bahamas abstract encrusting foraminifera that settled on experimental arrays deployed for 2 years in shelf 15 m 30 m shelf edge 70 m and slope 183 253 m environments off the carbonate platform of lee stocking island bahamas were found to occur in four environmental indicator guilds each with common and unique encrusting species these guilds can be used as paleobathymetric and temporal guides indicating how long a substrate was exposed on the sea floor prior to burial taphonomic signatures of encrusting foraminifera also changed with depth resulting in four foraminiferal taphofacies that varied from corrasion dissolution and abrasion at shallow sites to pristine tests at the deepest sites the taphonomic processes for encrusting foraminifera were found to be decoupled from those reported for invertebrate hardparts in this region perhaps related to their ability to nestle within sutures or other depressions deemed taphonomic refugia on the shell substrates the shelf edge site had the highest foraminiferal diversity associated with the highest physical damage to the tests which is counter intuitive to the intermediate disturbance hypothesis idh which posits that high physical disturbance leads to low species diversity while the idh appeared true for the shallowest sites it does not completely explain the high foraminiferal diversity at the shelf edge where physical taphonomic factors were high behavioral interactions such as overgrowth interactions also varied with depth and these can be used to examine depth related paleobehavioral patterns in the past thus the often overlooked encrusting foraminifera are excellent candidates for paleocommunity and paleoenvironmental analyses

flux chamber measurements of anomalous co2 emission from the flanks of mammoth mountain california the co2 fluxes involved in the mass mortality of large stands of timber on the flanks of mammoth mountain in california s sierra nevada were measured and spatial and temporal inhomogeneities observed our estimate of the integrated flux over the total area of tree kill is on the order of 400 t day 1 small scale spatial variability most likely reflects varying degrees of shallow bedrock fracture and soil compaction temporal variability suggests a fast response to subsurface conditions such as seismically induced crack propagation degassing of intruded magma or changing groundwater soil moisture conditions

multiple ruptures for long valley microearthquakes a link to volcanic tremor despite several episodes of ground deformation and intense seismic activity starting in 1978 the long valley california volcanic area has not produced clearly recognized volcanic tremor instead a variety of atypical microearthquakes have been recorded during these episodes including events dominated by low frequency long period or mixed high and low frequency hybrid signals during a 1997 episode a number of unusual microearthquakes occurred within a temporary 40 station seismic network surrounding the casa diablo area allowing the events to be precisely located and analyzed as a function of azimuth offset and source characteristics eight prime examples lie within two 7 km deep clusters of seismicity separated by about 1 km with four events in each cluster empirical green s function deconvolution shows that these events are composed of two to three sub events the sub events consisting of ordinary single rupture double couple microearthquakes the delay times between the sub events are constant within each cluster equaling 0 092 s in one and 0 06 s in the other events from other clusters show similar delays the signal interference produced by the closely spaced sub events gives rise to modulated delay dependent source spectra the regularity of the delays suggests that the sub events are being triggered by a fixed length and or time scale process an example being the length inflation rate of a magmatic or hydrothermal flow structure with continued action of the triggering process the sub events could proliferate and evolve into observable volcanic tremors at mammoth

interhemispheric synchrony of the last deglaciation inferred from alkenone palaeothermometry the relative timings of the last deglacial warming in the southern and northern hemispheres are not well constrained but are a crucial component in understanding the mechanisms of deglaciation1 a clearer picture of the degree of interhemispheric synchrony has been obscured by a dearth of high resolution temperature records that can be tied to the absolute calendar timescale moreover the quantification of tropical temperatures during the last glacial cycle is controversial2 8 here we apply the alkenone method of sea surface temperature reconstruction9 10 to several high resolution sediment cores recovered from the tropical indian ocean between 20 n and 20 s the inferred initial sea surface temperature warming 15 000 calendar years ago at 20 s is in phase with northern hemisphere sea this study and air11 temperature changes but lags antarctic warming12 14 by several millennia this finding along with the results of recent modelling studies15 16 provides strong support for the idea that changes in the ocean s global thermohaline circulation were not the only cause of interhemispheric climate teleconnection during the last deglaciation

reliable automatic detection of long period volcanic earthquakes at long valley caldera california capturing the rare long period lp volcanic earthquakes occurring in and near long valley caldera california is important to ongoing volcanic hazards monitoring it is difficult however because lp events are weak emergent and almost devoid of energy above a few hertz automatic systems designed for tectonic earthquakes routinely fail to capture lp events we applied a pc based teleseism specific event detection computer program to capturing these events retuning the software for lp events involved only changing parameters originally designed for change in this algorithm our retuned algorithm has captured every known lp event at long valley from october 1992 through the end of 1994 we monitored up to 16 stations known to produce good records of lp events saving those events that triggered enough of these stations typically 10 of 16 within a specified time window the principal difficulty has been the algorithm s sensitivity to regional earthquakes which have waveforms similar to lp events during our test the 1992 landers 1994 northridge and 1994 double springs flat nevada earthquakes each have swamped the detector requiring careful active management of pc disk resources the efficacy of this retuned algorithm and the poor performance of tectonic earthquake detectors during some volcanic emergencies make this algorithm an attractive candidate for volcano monitoring

inversion for p and s wave attenuation structure long valley caldera california p and s wave amplitude data from digital three component seismograms of local earthquakes recorded on a temporary seismic array have been used to tomographically invert for the three dimensional attenuation structure in the upper crust of long valley caldera california differential attenuation q 1 values are obtained through the use of a spectral ratio technique that minimizes the site effect on the spectral ratios the spectral ratios are inverted for q 1 using the lsqr algorithm zones of high positive p wave q 1 greater p wave attenuation are observed at a depth of 4 5 km beneath the east flank of mammoth mountain and at 6 8 km beneath the southwestern edge of the resurgent dome a region of positive s wave q 1 is seen at 7 8 km beneath the southern edge of the resurgent dome whereas at 6 7 km the s wave results are near average the region of positive s wave q 1 at 7 8 km beneath the resurgent dome may indicate the roof of a magmatic system the positive p wave q 1 at 4 5 km beneath mammoth mountain and 6 8 km beneath the resurgent dome may be due to the presence of a compressible fluid such as supercritical water these zones may represent some of the source regions for the long valley geothermal system

microhabitats of salt marsh foraminifera st catherines island georgia usa abstract salt marsh foraminifera of st catherines island georgia occupy a range of epibenthic to deep infaunal to 30 cm micro habitats freshly collected specimens of arenoparrella mexicana from 27 to 30 cm below the marsh surface extruded pseudopodial nets and actively collected foreign material about the aperture salt marsh foraminifera may be primarily epibenthic 0 1 cm epibenthic to intermediate infaunal 0 10 cm or deep infaunal 0 30 cm most of the twelve commonly occurring species in st catherines island marshes are epibenthic to intermediate infaunal species distributional patterns differ with regard to maximum depth of infaunal occurrences infaunal microhabitat utilization in different marsh zones and environments and the presence or absence of subsurface population maxima selective preservation impacts both calcareous and agglutinated foraminifera intense bioturbation primarily by halophytes and decapod crustaceans may contribute to the deep infaunal occurrences of foraminifera in these environments

spectral analysis of earthquakes in the 1989 mammoth mountain swarm near long valley california abstract the 1989 earthquake swarm beneath mammoth mountain near long valley california was unique for the area because of the occurrence of low frequency and unusual mixed frequency events at the time of the swarm a computer based earthquake detection system with near real time location and spectral fitting capabilities was operational at long valley this system detected over 1500 earthquakes during the swarm about 64 of the events had a high frequency content 4 to 8 hz 34 had a medium frequency content

temporal and three dimensional spatial analyses of the frequency magnitude distribution near long valley caldera california summary the 3 d distribution of the b value of the frequency magnitude distribution is analysed in the seismically active parts of the crust near long valley caldera california the seismicity is sampled in spherical volumes containing n 150 earthquakes and centred at nodes of a grid separated by 0 3 km significant variations in the b value are detected with b ranging from b 0 6 to b 2 0 high b value volumes are located near the resurgent dome and at depths below 5 km at mammoth mountain b values are found to be much lower south of the long valley caldera we interpret this to indicate that an active magma body has advanced from depths below 8 km to depths of 4 to 5 km beneath mammoth mountain in 1989 and that anomalous crust either highly fractured or containing unusually high pore pressure such as is the case in the vicinity of active magma bodies exists north of the seismically active area beneath the resurgent dome at all depths we also investigate the spatial distribution of temporal variations of the frequency magnitude distribution by introducing diverential b value maps b values increased from b 0 8 to b 1 5 underneath mammoth mountain at the onset of the 1989 earthquake swarm and remained high thereafter this suggests that an intrusion permanently altered the average distribution of cracks at 5 10 km depth or that the pore pressure permanently increased we propose that high b values are a necessary but not suycient condition near a magmatic body and therefore spatial b value mapping can be used to aid in the identification of active magma bodies

a process based model of pre eruption seismicity patterns and its use for eruption forecasting at dormant stratovolcanoes abstract using long term data sets the eruptive size timing and style can typically be successfully forecast for dormant volcanoes using current monitoring data and knowledge of precursory eruptive patterns the usaid usgs volcano disaster assistance program vdap utilizes seismic data over multiple eruption cycles and across volcano types to successfully forecast eruption size style and onset times as well as changes within ongoing eruptions from millions of seismic event observations we show that seismic data a proxy for rate dependent strain changes in the magmatic system combined with a process based conceptual geologic model enables eruption forecasting especially for stratovolcanoes dormant 20 years we show that this model often works for some open systems ones that sufficiently reseal to plug the conduit and also where a deep intrusion occurs after phreatic or phreatomagmatic explosions have begun this model is divided into four seismicity and geologic stages we describe each of the four stages of seismicity in detail and how they relate to the ongoing geologic process of that stage stage 1 deep intrusion and seismicity occurring at 10 to 40 km depth below the volcanic edifice stage 2 distal vt seismicity induced at distances from 2 to 30 km laterally from the summit by magma intruding into and inflating the upper crustal magma storage region stage 3 vent clearing seismicity associated with the initial vent creation and clearing phase of eruptive activity stage 4 repetitive event seismicity associated with the final ascent of magma from 2 km to the surface we present 36 examples of this seismic progression from 26 volcanoes we believe that this progression generally correlates with the magma flux and the eventual explosivity and is invaluable for forecasting eruptions

seismic image of a co2 reservoir beneath a seismically active volcano mammoth mountain is a seismically active volcano 200 000 to 50 000 years old situated on the southwestern rim of long valley caldera california since 1989 it has shown evidence of unrest in the form of earthquake swarms hill et al 1990 volcanic long period earthquakes pitt hill 1994 increased output of magmatic 3he sorey et al 1993 and the emission of about 500 tonnes day 1 of co2 farrar et al 1995 hill 1996 m sorey personal communication 1997 which has killed trees and poses a threat to human safety local earthquake tomography shows that in mid 1989 areas of subsequent tree kill were underlain by extensive regions where the ratio of the compressional and shear elastic wave speeds vp vs was about 9 per cent lower than in the surrounding rocks theory mavko mukerji 1995 experiment ito devilbiss nur 1979 and experience at other geothermal volcanic areas julian et al 1996 and at petroleum reservoirs harris et al 1996 indicate that vp vs is sensitive to pore fluid compressibility through its effect on vp the observed vp vs anomaly is probably caused directly by co2 and seismic vp vs tomography is thus a promising tool for monitoring gas concentration and movement in volcanoes which may in turn be related to volcanic activity

holocene reef growth in the maldives evidence of a mid holocene sea level highstand in the central indian ocean radiometrically calibrated ages from three reef cores are used to develop a holocene reef growth chronostratigraphy and sea level history in the maldives central indian ocean last interglacial reef u series age 122 7 ka was encountered at 14 1 m below mean sea level an age of ca 8100 calibrated cal yr b p immediately overlying this pleistocene surface records the initiation of holocene reef growth massive in situ corals occur throughout the cores and the consistency of the three age depth plots indicate that the reef grew steadily between 8100 and 6500 cal yr b p and at a decreasing rate for the next 2 k y the position of modern sea level was first achieved ca 4500 cal yr b p and sea level reached at least 0 50 1 m higher from 4000 to 2100 cal yr b p before falling to present level emergent fossil microatolls provide evidence of this higher sea level results are significant to two long standing issues relating to maldivian sealevel history first the ambiguity of a late holocene highstand has been resolved with clear evidence of its existence reported here second the uncertainty of the regional pattern of sea level change in the central indian ocean has been clarified the maldivian results broadly agreeing with island records in the eastern rather than western indian ocean our results provide the first field evidence confirming geophysical model projections of a highstand 4 2 k y ago in the central indian ocean though the observed level 0 50 0 1 m is lower than that projected

the 1989 earthquake swarm beneath mammoth mountain california an initial look at the 4 may through 30 september activity abstract mammoth mountain is a 50 000 to 200 000 year old cumulovolcano standing on the southwestern rim of long valley in eastern california on 4 may 1989 two m 1 earthquakes beneath the south flank of the mountain marked the onset of a swarm that has continued for more than 6 months in addition to its longevity noteworthy aspects of this persistent swarm include 1 an exponential like increase in the rate of activity through the first month 2 a vertically oriented planar distribution of hypocenters at depths between 6 and 9 km with a north northeast strike roughly perpendicular to the average t axis orientation for the swarm earthquakes 3 recurring spasmodic bursts rapid fire sequences of similar sized earthquakes with overlapping coda and occasional earthquakes with enhanced low frequency energy 4 a uniform temporal distribution of the four largest m 3 events over the first 4 months of the swarm with a cumulative seismic moment for the entire sequence through 30 september corresponding to a single m 4 earthquake 5 a b value of 1 2 and 6 submicrostrain perturbations on the nearby borehole dilatometer the first of which led the onset of swarm activity by more than 2 weeks these aspects of the swarm together with its location along the southern extension of the youthful mono inyo volcanic chain which last erupted 500 to 600 years ago point to a magmatic source for the modest but persistent influx of strain energy into the crust beneath mammoth mountain

biodiversity of foraminifera from late pleistocene to holocene coral reefs south sinai egypt tropical coral reefs are among the most diverse marine ecosystems in order to better understand temporal and spatial variation in late quaternary biodiversity foraminiferal faunas of two fossil raised reef terraces at the southern sinai peninsula were studied and compared to modern coral reef faunas eleven u series dates of shell fragments of the giant clam tridacna sp indicates deposition largely during marine isotope stage 5 mis 5 77 129 kyr bp for the two raised terraces in these terraces amphistegina a lessonii and a lobifera dominates the five fossil foraminiferal associations the fossil reef flat association 1 has common gypsina plana homotrema rubra and acervulina spp and fossil reef flat association 2 consists of amphistegina spp of the three fossil fore reef associations one has abundant porcelaneous taxa including sorites amphisorus peneroplis and borelis one has a mix of porcelaneous taxa and attached arborescent taxa homotrema and placopsilina and one has abundant attached and arborescent taxa miniacina gypsina acervulina and planogypsina the modern fringing reef is dominated by porcelaneous foraminifera and three modern associations are identified these include a lagoonal association with abundant peneroplis pertusus a reef flat association dominated by sorites orbiculus and a fore reef association with porcelaneous taxa plus common h rubra amphistegina lessonii and a lobifera based on our data and including additional published information on regional biodiversity it appears that during mis 5 foraminiferal biodiversity was higher and community structure was different than within the modern reefs these data and regional paleo climate patterns indicate that oceanographic conditions in the red sea were probably closer to normal marine conditions during the last interglacial than they are today

a first look at past sea surface temperatures in the equatorial indian ocean from mg ca in foraminifera 1 sea surface temperature sst for the central equatorial indian ocean has been reconstructed over the last 137 kyr from mg ca of the planktonic foraminiferal species globigerinoides ruber according to our record the equatorial indian ocean sst was 2 1 c colder during the last glacial maximum as compared to present times the data further shows that the surface equatorial indian ocean was comparatively warmer during isotopic stage 5e than at present 29 9 vs 28 5 c comparison of the equatorial indian ocean sst with the antarctic d and greenland 18o records shows that the major high latitude cooling warming events are also present in the equatorial indian ocean sst variation record similarity between the equatorial indian ocean sst and the equatorial pacific sst suggests the possibility of a common mechanism controlling the ssts in both the equatorial indian ocean and the pacific ocean

natural and industrial analogues for leakage of co2 from storage reservoirs identification of features events and processes and lessons learned instances of gas leakage from naturally occurring co2 reservoirs and natural gas storage sites serve as analogues for the potential release of co2 from geologic storage sites this paper summarizes and compares the features events and processes that can be identified from these analogues which include both naturally occurring releases and those associated with industrial processes the following conclusions are drawn 1 carbon dioxide can accumulate beneath and be released from primary and secondary shallower reservoirs with capping units located at a wide range of depths 2 many natural releases of co2 are correlated with a specific event that triggered the release 3 unsealed fault and fracture zones may act as conduits for co2 flow from depth to the surface 4 improperly constructed or abandoned wells can rapidly release large quantities of co2 5 the types of co2 release at the surface vary widely between and within different leakage sites 6 the hazard to human health was small in most cases possibly because of implementation of post leakage public education and monitoring programs 7 while changes in groundwater chemistry were related to co2 leakage waters often remained potable lessons learned for risk assessment associated with geologic carbon sequestration are discussed

modern foraminiferal distribution and diversity in two atolls from the maldives indian ocean abstract foraminifera from the coral reef lagoons of two atolls are used to investigate the distribution and diversity of assemblages in the central indian ocean eight assemblages and 270 species of foraminifera are identified three assemblages are reefal and dominated by amphistegina and calcarina only one lagoon assemblage is present in both atolls which is characterized by abundant ammonia sp 1 and smaller miliolid foraminifera in ari atoll abundant amphistegina sp 1 operculina ammonoides amphistegina radiata and nummulites venosa characterize one lagoon assemblage and abundant neoeponides bradyi and textularia cf t cushmani characterize the other in rasdhoo atoll abundant textularia gr foliacea and spiroloculina nummiformis characterize one lagoon assemblage and abundant textularia cf t cushmani and textularia sp 5 characterize the other the assemblages compare well with sedimentological characteristics which is also reflected in their distributions species diversity in the maldives appears to be higher than the western indian ocean region due to the stronger influence of central indo pacific faunas it is not however as high as the central indo pacific region which may be due to lower habitat diversity

volcano seismology hazards assessment the last few years have seen several impressive examples of seismic monitoring at volcanoes to provide warnings that have saved lives and property changes in the rates and character of volcanic earthquakes provided precursory signs to explosive eruptions of moderate size at redoubt volcano alaska mount unzen japan mount spurr alaska and rabaul caldera papua new guinea as well as the large eruption at mount pinatubo philippines in all these cases information was successfully communicated and put to practical use through broadcasts of public warnings prior to the eruptions and evacuations were initiated for the volcanoes located in populated areas at mount pinatubo probably thousands and possibly tens of thousands of lives were saved

changes in diversity and assemblages of foraminifera through the holocene in an atoll from the maldives indian ocean abstract this study presents the first high resolution holocene records of diversity and assemblages of benthic foraminifera from tropical reef environments in the indian ocean two 3 2 m and 4 4 m long cores from the lagoon of rasdhoo atoll 4 n 73 w in the central maldives were sampled at 250 yr intervals core 16 covers most of the holocene 10 32 0 kyr bp and was taken in the deep lagoon of the atoll 35 m water depth core 19 covers the time span 7 375 0 kyr bp and is from a sublagoon 14 m water depth on the northern margin of the atoll in core 16 an early colonization phase during holocene sea level rise is characterized by an ammonia sp 1 dominated assemblage until 7 kyr bp the slowdown of sea level rise in the mid holocene 4 kyr bp marks the onset of a phase of stable environmental conditions in the deep lagoon with high diversity a shift toward lower diversity and the dominance of textularia foliacea has occurred from 4 1 kyr bp which may be explained with the intermediate disturbance hypothesis an environmental change at 1 4 kyr has caused a distinct faunal change the decrease of t foliacea and an increased recovery in diversity in core 19 a significant faunal change at 4 0 kyr bp from an ammonia sp 2 dominated fauna to a fauna with ammonia sp 1 miliolid taxa and a higher diversity might be related to the formation of a sand spit that separates the sublagoon from the main lagoonal basin the westward extension of the sand spit during the late holocene could have changed the restricted bottom water circulation in the main lagoon and caused longer residence times of water and the build up of lower oxygen and higher nutrient concentrations this study underlines the importance of the factor time on diversity and the significance of lagoon circulation and bottom water residence times on assemblages and diversity of benthic foraminifera

seismicity and stress tensor inversion in the central washington cascade mountains abstract tectonic stress in the pacific northwest washington is dominated by a n s major compressive axis 1 and a minor compressive axis 3 which varies from e w to near vertical some variations in this pattern occur in different parts of the region in this study we used 550 earthquakes in the central washington cascade mountains to study in detail the uniformity of the stress tensor in this volcanic arc earthquakes from the pacific northwest seismograph network pnsn catalog were divided into several subsets based on epicentral and depth groupings and stress tensor inversions using the gephart and forsyth technique were computed for each group as in previous similar studies the maximum compressive stress axis 1 is nearly horizontal and trending n s to nne ssw in all but one subset shallower events directly under mount rainier have a near vertical 1 for other subsets the minimum compressive stress axis 3 deviates from vertical to horizontal for different groups of events in particular events in the depth range of 10 to 14 km in the western rainier seismic zone wrsz have near vertical 3 direction whereas other depth ranges in this area show a near horizontal e w 3 orientation we hypothesize that the change in orientation of 3 in the 10 to 14 km depth range in the wrsz may be due to the influence of the nearby mount rainier magmatic system independent evidence for magma at this depth comes in the form of a few deep long period lp events

crustal structure beneath long valley caldera from modeling of teleseismic p wave polarizations and ps converted waves in this study the authors present new constraints on the nature of the low velocity zone beneath long valley caldera based on the measured propagation directions of teleseismic p waves and on modeling of p to s converted waves the low velocity body is a large asymmetrical volume which deepens to the east extending from depths of 7 to 30 km it contains lower velocities than originally proposed by earlier teleseismic studies in particular there is a tabular feature between 7 and 11 km depth that has a reduction in velocity of about 30 these low velocities imply a much greater percentage of melt in the crust beneath long valley caldera than previously estimated array analysis of large delayed arrivals identifies them to be ps converted waves from the shoulders and roof of this tabular zone these conversions bound the depth to the magma chamber roof to be within about 10 km of the surface these results are consistent with elements from several other studies and the authors present an integrated and improved model of crustal structure at long valley the concordance of the deeper low velocity zones with regional structural trends implies that the shallow low velocity feature is a cupola on topmore of an asymmetric diapiric ridge rising up from the migmatized lower crust of the basin and range the authors present two contrasting interpretations of the geometry of low velocity zones in the crust one implies a time invariant magma chamber and conduit system for long valley caldera the other implies an evolution of that system from a simple vertical regime to its current asymmetrical geometry 37 refs 19 figs 1 tab less

swarms of similar long period earthquakes in the mantle beneath mauna loa volcano abstract we present analyses of two swarms of long period lp earthquakes at 30 km depth that accompanied the geodetically observed 2002 2005 mauna loa intrusion the first lp earthquake swarm in 2002 consisted of 31 events that were precursory and preceded the start of mauna loa inflation the second lp swarm of two thousand events occurred from 2004 2005 the rate of lp earthquakes slowed significantly coincident with the occurrence of the december 26 2004 m w 9 3 sumatra earthquake suggesting that the seismic waves from this great earthquake may have had a dynamic triggering effect on the behavior of mauna loa s deep magma system using waveform cross correlation and double difference relocation we find that a large number of earthquakes in each swarm are weakly similar and can be classified into two families the relocated hypocenters for each family collapse to compact point source regions almost directly beneath the mauna loa intrusion we suggest that the observed waveform characteristics are compatible with each family being associated with the resonance of a single fluid filled vertical crack of fixed geometry with differences in waveforms between events being produced by slight variations in the trigger mechanism if these lp earthquakes are part of the primary magma system that fed the 2002 2005 intrusion as indicated by the spatial and temporal associations between mantle seismicity and surface deformation then our results raise the possibility that this magma system may be quite focused at these depths as opposed to being a diffuse network it is likely that only a few locations of mauna loa s deep magma system met the geometric and fluid dynamic conditions for generating lp earthquakes that were large enough to be recorded at the surface and that much of the deep magma transfer associated with the 2002 2005 intrusion occurred aseismically

a conceptual model of the mount spurr magmatic system from seismic and geochemical observations of the 1992 crater peak eruption sequence a conceptual model of the geometry and dynamics of the mount spurr magmatic system is developed using seismic geochemical and visual observations of the 1992 crater peak eruption sequence the basis for this model is a new classification of all located seismic events and results from prior studies of seismology geology geochemistry and geophysics of the mount spurr area significant seismic features of the 1992 eruption sequence include 1 a distinct swarm of volcano tectonic vt earthquakes in august 1991 directly beneath the crater peak vent 2 a caldera wide increase in vt earthquakes lasting 7 months which preceded the 27 june eruption 3 two shallow swarms of vt earthquakes that occurred on 5 june and 27 june the latter immediately preceding the 27 june eruption 4 a mix of vt long period lp and hybrid events at depths of 20 40 km which began coincident with the onset of seismic unrest and reached a peak after eruptive activity ended 5 a strong swarm of vt earthquakes that began as the 16 17 september eruption was ending 6 a prominent swarm of vt earthquakes on 9 10 november at depths of 1 to 4 km beneath crater peak and 7 a smaller swarm of vt earthquakes in late december 1992 which were located between 7 and 10 km depth these seismic observations combined with geological geochemical and geophysical data and observations suggest a deep magmatic source zone for crater peak andesites at depths of 20 40 km a smaller mid crustal storage zone at about 10 km depth and a conduit that extends to the surface we infer that the magmas erupted in 1992 were generated at depths of 20 40 km and rose to the mid crustal storage zone that fed all three 1992 eruptions the 1992 eruption sequence may have terminated when additional magma solidified at shallow depths

depth migration of seismovolcanic tremor sources below the klyuchevskoy volcanic group kamchatka determined from a network based analysis we present a method for automatic location of dominant sources of seismovolcanic tremor in 3 d based on the spatial coherence of the continuously recorded wavefield at a seismic network we analyze 4 5 years of records from the seismic network at the klyuchevskoy volcanic group in kamchatka russia when four volcanoes experienced tremor episodes after enhancing the tremor signal with spectral whitening we compute the daily cross correlation functions related to the dominant tremor sources from the first eigenvector of the spectral covariance matrix and infer their daily positions in 3 d we apply our technique to the tremors beneath shiveluch klyuchevskoy tolbachik and kizimen volcanoes and observe the yearlong preeruptive volcanic tremor beneath klyuchevskoy from deep to shallow parts of the plumbing system this observation of deep volcanic tremor sources demonstrates that the cross correlation based method is a very powerful tool for volcano monitoring

lagoonal facies ages and sedimentation in three atolls in the pacific abstract in order to investigate pacific atoll lagoonal facies and temporal evolution we collected and analyzed surface and core sediments from three pacific atoll lagoons of various sizes and depths kayangel of palau islands enewetak and majuro of the marshall islands the lagoons were divided into three facies calcarina facies calcarina heterostegina mixed facies and heterostegina facies these were based on the presence or absence of the tests of two larger benthic foraminifera calcarina and heterostegina as indicators of reef flat and deep lagoon environments respectively the calcarina facies is composed of allochthonous reef derived materials the calcarina heterostegina mixed facies is a mixture of reef derived and in situ lagoonal materials and the heterostegina facies is composed mainly of in situ lagoonal materials as both foraminifera are widely distributed in the western to central pacific region the facies classification presented in this study can be applicable to other pacific atolls based on the results of radiocarbon dating on samples obtained from cores at majuro lagoon the accumulation rates of the lagoonal sediments were estimated as 0 65 m kyr 1 calcium carbonate production was calculated on the basis of the accumulation rates and density of sediments to be 710 g caco 3 m 2 yr 1

precursory swarms of long period events at redoubt volcano 1989 1990 alaska their origin and use as a forecasting tool abstract during the eruption of redoubt volcano from december 1989 through april 1990 the alaska volcano observatory issued advance warnings of several tephra eruptions based on changes in seismic activity related to the occurrence of precursory swarms of long period lp seismic events dominant period of about 0 5 s the initial eruption on december 14 occurred after 23 years of quiescence and was heralded by a 23 hour swarm of lp events that ended abruptly with the eruption after a series of vent clearing explosions over the next few days dome growth began on december 21 another swarm with lp events similar to those of the first began on the 26th and ended in a major tephra eruption on january 2 eruptions continued over the next two weeks and then ceased until february 15 when a large eruption initiated a long phase of repetitive dome building and dome destroying episodes that continued into april warnings were issued before the major events on december 14 and january 2 but as the eruptive sequence continued after january 2 the energy of the swarms decreased and forecasting became more difficult a significant but less intense swarm preceded the february 15 eruption which was not forecast this eruption destroyed the only seismograph on the volcanic edifice and stymied forecasting until march 4 when the first of three new stations was installed within 3 km of the active vent from march 4 to the end of the sequence on april 21 there were eight eruptions six of which were preceded by detectable swarms of lp events although weak these swarms provided the basis for warnings issued before the eruptions on march 23 and april 6 the initial swarm on december 13 had the following features 1 short duration 23 hours 2 a rapidly accelerating rate of seismic energy release over the first 18 hours of the swarm followed by a decline of activity during the 5 hours preceding the eruption 3 a magnitude range from 0 4 to 1 6 4 nearly identical lp signatures with a dominant period near 0 5 s 5 dilatational first motions everywhere and 6 a stationary source location at a depth of 1 4 km beneath the crater this occurrence of long period events suggests a model involving the interaction of magma with groundwater in which magmatic gases steam and water drive a fixed conduit at a stationary point throughout the swarm the initiation of that sequence of events is analogous to the failure of a pressure relief valve connecting a lower supercharged magma dominated reservoir to a shallow hydrothermal system a three dimensional model of a vibrating fluid filled crack recently developed by chouet is found to be compatible with the seismic data and yields the following parameters for the lp source crack length 280 380 m crack width 140 190 m crack thickness 0 05 0 20 m crack stiffness 100 200 sound speed of fluid 0 8 1 3 km s compressional wave speed of rock 5 1 km s density ratio of fluid to rock 0 4 and ratio of bulk modulus of fluid to rigidity of rock 0 03 0 07 the fluid filled crack is excited intermittently by an impulsive pressure drop that varies in magnitude within the range of 0 4 to 40 bar such disturbance appears to be consistent with a triggering mechanism associated with choked flow conditions in the crack

helium isotope and gas discharge variations associated with crustal unrest in long valley caldera california 1989 1992 the onset of anomalous seismic activity in 1989 beneath mammoth mountain on the southwestern rim of the long valley caldera california was followed within approximately 4 months by a large increase in sup 3 he sup 4 he in vapor discharged from a fumarole on the north side of the mountain the helium isotopic ratio at this vent rose to a maximum of 6 7 r sub a in july 1990 and subsequently declined to values near 5 r sub a potential sources of the sup 3 he rich vapors include degassing of fresh magma degassing from fresh surfaces generated in newly fractured igneous rocks and volatile release from a sup 3 he rich gas chamber situated above previously emplaced intrusives the magnitude of the increase in helium isotopic composition from 3 8 to 6 7 r sub a the persistence of relatively high values 5 r sub a over a period of 3 years the increase in the flux of total he relative to gases in air saturated water and the increases in the rates of discharge of steam and gas from this fumarole indicate that magmatic intrusion did in fact begin in 1989 beneath mammoth mountain seismic activity and limited measurements of extensional deformation at the surface suggest that the depth of intrusion maymore be as shallow as 2 km consistent with the prompt appearance of increased sup 3 he sup 4 he ratios in the fumarolic gas and that the intrusive process may have persisted for approximately 1 year in contrast a similar combination of magmatic intrusion and anomalous seismic activity beneath the resurgent dome south moat region during the 1989 1991 period resulted in at most relatively small changes in sup 3 he sup 4 he in fumarolic discharge at the southern edge of the resurgent dome the more subdued response may result from a combination of greater intrusive depths and greater dilution of sup 3 he rich inputs to thermal fluid reservoirs in the shallow hydrothermal system in this area compared with mammoth mountain 60 refs 11 figs 4 tabs less

ecology of extant nummulitids and other larger benthic foraminifera applications in palaeoenvironmental analysis abstract larger benthic foraminifera lbf are important contributors to modern and ancient tropical shallow marine sediments over the past 30 years a substantial body of literature has built up on the ecology of modern lbf especially in terms of their environmentally sensitive depth distribution reproductive strategy and morphology and the symbiotic relationship between many larger foraminifera and photosynthetic algae over the same period the extinct genus nummulites which is abundant in eocene sediments of southern europe north africa and the arabian peninsula has increasingly been studied principally because significant volumes of hydrocarbons have been discovered reservoired within nummulitic limestones offshore tunisia and libya the modern ecological studies of lbf provide a powerful tool with which to develop palaeoecological models for fossil nummulites and other symbiont bearing larger foraminifera in the rock record

deep long period earthquakes west of the volcanic arc in oregon evidence of serpentine dehydration in the fore arc mantle wedge here we report on deep long period earthquakes dlps newly observed in four places in western oregon the dlps are noteworthy for their location within the subduction fore arc 40 80 km west of the volcanic arc well above the slab and near the moho these offset dlps occur near the top of the inferred stagnant mantle wedge which is likely to be serpentinized and cold the lack of fore arc dlps elsewhere along the arc suggests that localized heating may be dehydrating the serpentinized mantle wedge at these latitudes and causing dlps by dehydration embrittlement higher heat flow in this region could be introduced by anomalously hot mantle associated with the western migration of volcanism across the high lava plains of eastern oregon entrained in the corner flow proximal to the mantle wedge alternatively fluids rising from the subducting slab through the mantle wedge may be the source of offset dlps as far as we know these are among the first dlps to be observed in the fore arc of a subduction zone system

interannual and intraseasonal variations in monsoon depressions and their westward propagating predecessors abstract the majority of monsoon depressions develop from the regenesis of westward propagating residual lows from the east most of these residual lows can be traced to weather disturbances in the south china sea including tropical cyclones and 12 24 day monsoon lows hypothetically any mechanism causing a variation in the occurrence frequency of these two types of weather disturbances in the western tropical pacific south china sea wtp scs region may result in a corresponding change in the formation frequency of monsoon depressions over the bay of bengal two such possible mechanisms are interannual and intraseasonal variations of large scale summer circulation in the wtp scs region induced by 1 the interannual variation of the sea surface temperature sst in the eastern tropical pacific and 2 the northward migration of the 30 60 day monsoon trough ridge the national centers for environmental prediction national center for atmospheric research reanalysis data and the 6 hourly tropical cyclone tr

long period earthquakes in the long valley caldera region eastern california most earthquakes occurring near long valley caldera since the onset of recurring swarm activity in 1980 have the broad band signature typical of tectonic or volcano tectonic earthquakes with impulsive high frequency p and s waves with the mammoth mountain earthquake swarm in mid 1989 we began detecting occasional events with a marked deficiency in energy above 5 hz a feature typical of long period lp volcanic earthquakes these events occur beneath the southwest flank of mammoth mountain at focal depths ranging from 10 to 28 km distinctly deeper than the 2 to 10 km depth range for tectonic earthquakes in the area the lp events occur at intervals ranging from weeks to months individual occurrences typically consist of several events within 2 to 5 minutes where the largest event has never been first magnitudes range from 0 5 to 1 8 the mid crustal focal depths of the lp events are similar to occurrences at a number of areas with holocene volcanism in japan and the western united states they may indicate the movement of magmatic fluids but do not necessarily indicate an imminent volcanic eruption

tsunami sediments and their foraminiferal assemblages abstract tsunami hazard assessment begins with a compilation of past events that have affected a specific location given the inherent limitations of historical archives the geological record has the potential to provide an independent dataset useful for establishing a richer chronologically deeper time series of past events recent geological studies of tsunami are helping to improve our understanding of the nature and character of tsunami sediments wherever possible geologists should be working to improve the research tool kit available to identify past tsunami events marine foraminifera single celled heterotrophic protists have often been reported as present within tsunami deposited sediments but in reality little information about environmental conditions and by analogy the tsunami that deposited them has been reported even though foraminifera have an enormous capacity to provide meaningful palaeo environmental data here we review what foraminifera are describe their basic form and significance summarise where they have been reported in tsunami sediments and identify what can be learnt from them we review the gaps in our understanding and make recommendations to assist researchers who examine foraminiferal assemblages in order to enhance their use within tsunami geology

deep structure of the northeastern japan arc and its relationship to seismic and volcanic activity evidence for possible deep seated magmatic activity beneath northeastern japan can be obtained from seismic observations tomographic inversions of p wave velocity data show low velocity zones distributed in the crust and upper mantle beneath active volcanoes in or around these zones anomalously low frequency micro earthquakes perhaps caused by magmatic activity are found at depths of 25 40 km distinct s wave reflectors corresponding to the upper surfaces of magma bodies are found at depths of 10 18 km large crustal earthquakes also occur around the low velocity zones these observations reveal the distribution of magma reservoirs at depths and elucidate its relation with shallow seismicity beneath volcanic arcs

deformation near the long valley caldera eastern california 1982 1986 annual surveys of trilateration and leveling networks in and around long valley caldera in the 1982 1985 interval indicate that the principal sources of deformation are inflation of a magma chamber beneath the resurgent dome and right lateral strike slip on a vertical fault in the south moat of the caldera the rate of inflation of the magma chamber seems to have been roughly constant 0 02 km3 yr in the 1982 1985 interval but the slip rate on the south moat fault has decreased substantially in addition there is evidence for a shallow source of dilatation possibly dike intrusion beneath the south moat of the caldera in 1983 and less certain evidence for a deep source possibly magma chamber inflation beneath mammoth mountain in the western caldera in 1983 1985 deformation in the 1985 1986 interval as inferred from trilateration alone seems to be similar to that observed in 1984 1985

earthquake classification location and error analysis in a volcanic environment implications for the magmatic system of the 1989 1990 eruptions at redoubt volcano alaska abstract determination of the precise locations of seismic events associated with the 1989 1990 eruptions of redoubt volcano posed a number of problems including poorly known crustal velocities a sparse station distribution and an abundance of events with emergent phase onsets in addition the high relief of the volcano could not be incorporated into the hypoellipse earthquake location algorithm this algorithm was modified to allow hypocenters to be located above the elevation of the seismic stations the velocity model was calibrated on the basis of a posteruptive seismic survey in which four chemical explosions were recorded by eight stations of the permanent network supplemented with 20 temporary seismographs deployed on and around the volcanic edifice the model consists of a stack of homogeneous horizontal layers setting the top of the model at the summit allows events to be located anywhere within the volcanic edifice detailed analysis of hypocentral errors shows that the long period lp events constituting the vigorous 23 hour swarm that preceded the initial eruption on december 14 could have originated from a point 1 4 km below the crater floor a similar analysis of lp events in the swarm preceding the major eruption on january 2 shows they also could have originated from a point the location of which is shifted 0 8 km northwest and 0 7 km deeper than the source of the initial swarm we suggest this shift in lp activity reflects a northward jump in the pathway for magmatic gases caused by the sealing of the initial pathway by magma extrusion during the last half of december volcano tectonic vt earthquakes did not occur until after the initial 23 hour long swarm they began slowly just below the lp source and their rate of occurrence increased after the eruption of 01 52 ast on december 15 when they shifted to depths of 6 to 10 km after january 2 the vt activity migrated gradually northward this migration suggests northward propagating withdrawal of magma from a plexus of dikes and or sills located in the 6 to 10 km depth range precise relocations of selected events prior to january 2 clearly resolve a narrow steeply dipping pencil shaped concentration of activity in the depth range of 1 7 km which illuminates the conduit along which magma was transported to the surface a third event type named hybrid which blends the characteristics of both vt and lp events originates just below the lp source and may reflect brittle failure along a zone intersecting a fluid filled crack the distribution of hybrid events is elongated 0 2 0 4 km in an east west direction this distribution may offer constraints on the orientation and size of the fluid filled crack inferred to be the source of the lp events

tomographic image of a seismically active volcano mammoth mountain california high resolution tomographic p wave s wave and vp vs velocity structure models are derived for mammoth mountain california using phase data from the northern california seismic network and a temporary deployment of broadband seismometers an anomalous volume 5 1 109 to 5 9 1010m3 of low p and low s wave velocities is imaged beneath mammoth mountain extending from near the surface to a depth of 2 km below sea level we infer that the reduction in seismic wave velocities is due to the presence of co2 distributed in oblate spheroid pores with mean aspect ratio 1 6 10 3 to 7 9 10 3 crack like pores and mean gas volume fraction 8 1 10 4 to 3 4 10 3 the pore density parameter 3 4 na3 0 11 where n is the number of pores per cubic meter and a is the mean pore equatorial radius the total mass of co2 is estimated to be 4 6 109 to 1 9 1011 kg the local geological structure indicates that the co2 contained in the pores is delivered to the surface through fractures controlled by faults and remnant foliation of the bedrock beneath mammoth mountain the total volume of co2 contained in the reservoir suggests that given an emission rate of 500 tons day 1 the reservoir could supply the emission of co2 for 25 1040 years before depletion continued supply of co2 from an underlying magmatic system would significantly prolong the existence of the reservoir

observations of deep long period dlp seismic events beneath aleutian arc volcanoes 1989 2002 abstract between october 12 1989 and december 31 2002 the alaska volcano observatory avo located 162 deep long period dlp events beneath 11 volcanic centers in the aleutian arc these events generally occur at mid to lower crustal depths 10 45 km and are characterized by emergent phases extended codas and a strong spectral peak between 1 0 and 3 0 hz observed wave velocities and particle motions indicate that the dominant phases are p and s waves dlp epicenters often extend over broad areas 5 20 km surrounding the active volcanoes the average reduced displacement of aleutian dlps is 26 5 cm2 and the largest event has a reduced displacement of 589 cm2 or ml 2 5 aleutian dlp events occur both as solitary events and as sequences of events with several occurring over a period of 1 30 min within the sequences individual dlps are often separated by lower amplitude volcanic tremor with a similar spectral character occasionally volcano tectonic earthquakes that locate at similar depths are contained within the dlp sequences at most aleutian volcanoes dlps appear to loosely surround the main volcanic vent and occur as part of background seismicity a likely explanation is that they reflect a relatively steady state process of magma ascent over broad areas in the lower and middle portions of the crust at mount spurr dlp seismicity was initiated by the 1992 eruptions and then slowly declined until 1997 at shishaldin volcano a short lived increase in dlp seismicity occurred about 10 months prior to the april 19 1999 eruption these observations suggest a link between eruptive activity and magma flux in the mid to lower crust and uppermost mantle

spatiotemporal distribution of low frequency earthquakes in southwest japan evidence for fluid migration and magmatic activity abstract low frequency earthquakes lfes in the lower crust and uppermost mantle are widely observed in southwest japan and they occur not only along the subducting philippine sea phs slab interface but also beneath active arc volcanoes the volcanic lfes are still not well understood because of their limited quantities and less reliable hypocenter locations in this work seismic tomography is used to determine detailed three dimensional 3 d p and s wave velocity vp and vs models of the crust and upper mantle beneath southwest japan and then the obtained 3 d vp and vs models are used to relocate the volcanic lfes precisely the results show that the volcanic lfes can be classified into two types pipe like and swarm like lfes and both of them are located in or around zones of low velocity and high poisson s ratio anomalies in the crust and uppermost mantle beneath the active volcanoes the pipe like lfes may be related to the fluid migration from the lower crust or the uppermost mantle whereas the swarm like lfes may be related to local magmatic activities or small magma chambers the number of lfes sometimes increases sharply before or after a nearby large crustal earthquake which may cause cracks and fluid migration the spatiotemporal distribution of the lfes may indicate the track of migrating fluids as compared with the tectonic lfes along the phs slab interface the volcanic lfes are more sensitive to fluid migration and local magmatic activities high pore pressures play an important role in triggering both types of lfes in southwest japan

seismicity and velocity structure of loihi seamount from the 1996 earthquake swarm the largest earthquake swarm yet recorded on loihi submarine volcano took place in july and august of 1996 the swarm consisted of two phases of seismic activity and was associated with the formation of a pit crater and additional faulting of loihi s summit platform the first phase of activity was comprised of predomi nantly high frequency events scattered over the southern flanks of the volcano fol lowing a day of seismic quiescence the second phase of activity began consisting of lower frequency earthquakes with strong t phases the phase 2 events took place beneath loihi s summit presumably marking the formation of the pit crater pele s pit data obtained by an ocean bottom seismometer obs on loihi during the swarm help constrain a new velocity model for loihi the relocated earthquakes combined with other characteristics of the swarm enabled us to develop a model for the events leading up to the formation of pele s pit that includes 1 a prolonged eruption 2 a tectonic event beneath loihi s south flank and 3 the drainage of a shallow magma chamber