modelling the macroscopic behavior of strombolian explosions at erebus volcano abstract we analyze seismic signals associated with the strombolian explosion quakes at erebus volcano antarctica examining the high frequency 0 5 hz portion of the spectrum we consider recordings relative to two time periods during the years 2005 and 2006 cross correlation analysis allows us to distinguish three classes of events spectral properties and polarization analysis provide evidence of a very complex volcanic structure we conduct analyses to elucidate the macroscopic dynamic system associated with the explosions the distribution of the times between successive explosion quakes is exponential implying a poissonian process as observed at stromboli volcano but on a different time scale the sequence of the occurrence of the explosions can be described by classical intermittency a coalescence chandrasekar landau mean field model reproduces gas bubble sizes comparable with those observed at the lava lake surface finally the classical equation for the ascent of gas bubbles is generalized by adding a diffusive process this model provides ascent velocities depending on the bubble radius for gas bubbles greater than a few centimeters variation in ascent velocity due to diffusion becomes negligible and the ascent velocity appears to be governed primarily by buoyancy

fractal properties of tremor and gas piston events observed at kilauea volcano hawaii we study the fractal properties of shallow volcanic tremor and gas piston events associated with magma degassing at kilauea volcano hawaii using data from two dense short baseline arrays of seismographs deployed near the active crater of puu oo on the east rift of the volcano we found an upper bound on the fractal dimension of a strange attractor common to phase portraits of both tremor and gas piston activities in the range of 3 1 4 5 with a mean of 3 75 over a scale length of the wave field of the order of 100 m the dimension of the attractor fluctuates over the course of tremor and gas piston episodes within a range comparable to the spatial variations of fractal dimensions found in the wave field the existence of a categorically stable attractor characterizing both types of activities strongly suggests that the excitation mechanism of tremor is similar to that of gas piston events which in turn are correlated with visual observations at the volcanic vent the low value derived for the dimension of the attractor in phase space points to significant self organization in the process of generation of tremor and offers general constraints on the dimensionality of attractors derived from models of acoustic emission associated with magma flow vesiculation and degassing

self sustained oscillations at volcan de colima mexico inferred by independent component analysis we have analyzed long period lp seismic events of volcan de colima mexico recorded by four three component broad band seismometers during january 2006 frequency domain analysis shows spectra mainly peaked in the range 0 3 2 hz and characterized by a monotonic decreasing envelope as those produced in a cylindrically symmetric self oscillating cavity interacting with a confined jet independent component analysis a time series decomposition method extracts two or three nonlinear oscillation modes depending on the station with the fundamental one peaked at 0 4 0 5 hz these decomposed waves have a well defined spectral content and are self sustained oscillations with low dimensionality as shown by dynamic system reconstruction methods moreover they show radial polarization in near field and transverse polarization in far field in north west south east direction finally we hypothesize a branched plumbing system with two principal conduits having alignments orthogonal to one another

the 2010 maule chile earthquake downdip rupture limit revealed by space geodesy radar interferometry from the alos satellite captured the coseismic ground deformation associated with the 2010 mw 8 8 maule chile earthquake the alos interferograms reveal a sharp transition in fringe pattern at 150 km from the trench axis that is diagnostic of the downdip rupture limit of the maule earthquake an elastic dislocation model based on ascending and descending alos interferograms and 13 near field 3 component gps measurements reveals that the coseismic slip decreases more or less linearly from a maximum of 17 m along strike average of 6 5 m at 18 km depth to near zero at 43 48 km depth quantitatively indicating the downdip limit of the seismogenic zone the depth at which slip drops to near zero appears to be at the intersection of the subducting plate with the continental moho our model also suggests that the depth where coseismic slip vanishes is nearly uniform along the strike direction for a rupture length of 600 km the average coseismic slip vector and the interseismic velocity vector are not parallel which can be interpreted as a deficit in strike slip moment release

a reappraisal of seismicity recorded during the 1996 gjalp eruption iceland in light of the 2014 2015 barðarbunga holuhraun lateral dike intrusion this study performs a reanalysis of the seismicity recorded during the 1996 gjalp eruption that occurred at nw vatnajokull iceland the seismicity was recorded by the temporary hotspot network consisting of 30 three component broadband stations in total 301 events were identified between 29 september and 12 october and their phases were manually picked a velocity model was estimated from p phase travel times by using velest events were first located using the algorithm nonlinloc in order to obtain absolute locations precise relative locations were obtained with hypodd by utilizing catalog and cross correlation differential travel times results show that events clustered first along the sw rim of the bar arbunga caldera and later along the gjalp fissure with most hypocentral depths located between 3 and 8 km waveforms of the 10 largest events that followed the bar arbunga earthquake were inverted in order to obtain moment tensors for all events we found that the deviatoric moment tensor fits the data better than pure double couple or full moment tensor solutions events along the bar arbunga caldera exhibited reverse focal mechanisms while those at the gjalp fissure exhibited mostly strike slip faulting seismic velocity variations calculated using ambient noise interferometry point to the possibility that a small subglacial eruption occurred at bar arbunga before the main earthquake this removed melt from the magma chamber causing its roof to collapse and also resulted in the lateral migration of magma towards the gjalp fissure the 2014 2015 bar arbunga holuhraun eruption shares common characteristics with the 1996 gjalp eruption although the size of the latter was much smaller

source mechanism of volcanic tremor low frequency 10 hz volcanic earthquakes originate at a wide range of depths and occur before during and after magmatic eruptions the characteristics of these earthquakes suggest that they are not typical tectonic events physically analogous processes occur in hydraulic fracturing of rock formations low frequency icequakes in temperate glaciers and autoresonance in hydroelectric power stations we propose that unsteady fluid flow in volcanic conduits is the common source mechanism of low frequency volcanic earthquakes tremor the fluid dynamic source mechanism explains low frequency earthquakes of arbitrary duration magnitude and depth of origin as unsteady flow is independent of physical properties of the fluid and conduit fluid transients occur in both low viscosity gases and high viscosity liquids a fluid transient analysis can be formulated as generally as is warranted by knowledge of the composition and physical properties of the fluid material properties geometry and roughness of the conduit and boundary conditions to demonstrate the analytical potential of the fluid dynamic theory we consider a single phase fluid a melt of mount hood andesite at 1250 c in which significant pressure and velocity variations occur only in the longitudinal direction further simplification of the conservation of mass and momentum equations presents an eigenvalue problem that is solved to determine the natural frequencies and associated damping of flow and pressure oscillations for a simple constant pressure reservoir conduit orifice fluid system a change in orifice size can cause the source signal duration due to a single disturbance to change from several seconds to in excess of an hour fluid kinematic viscosity 0 412 m2 s is both included and neglected in the analysis to illustrate its effect upon system damping tremor magnitude is related to the magnitude of the conduit wall motion occurring in response to oscillating fluid pressures the entire volcanic fluid system does not generally experience a transient flow condition at a given time closed end and constant pressure fluid system boundaries reflect pressure waves and isolate components of the fluid system total fluid movement may not be accurately monitored by tremor data alone since steady state and slowly changing flows are aseismic

internal dynamics of a paleoaccretionary wedge insights from combined isotope tectonochronology and sandbox modelling of the south central chilean forearc forearc accretionary wedges are cyclic systems in which material is frontally and or basally accreted material cycling involves underthrusting subduction underplating exhumation erosion transfer to the trench and underthrusting again in this study we present a novel tectonochronologic approach to constrain long term exhumation rates of basally accreted wedge complexes based on isotopic dating of structural features on petrological data and sandbox analogue simulations congruence between the structural inventory in nature and structures generated in scaled sandbox experiments allows detailed insights into wedge dynamics for the present day surface material of the paleoaccretionary wedge of south central chile valdivia area 40 s published u pb ages of detrital zircon place a maximum age of 278 ma for subduction prograde metamorphism at transitional greenschist to blueschist facies conditions 420 c 8 9 kbar was immediately followed by progressive penetrative deformation associated with basal accretion dated at 250 245 ma using rb sr internal mineral isochrons the accretion process involved duplex tectonics and antiformal stacking with formation of near horizontal mylonitic shear zones at around 241 ma continuous basal accretion at depth gave rise to an extensional tectonic regime at higher structural levels both semi ductile small scale extensional shear zones and post kinematic vein mineralizations yield rb sr ages of 235 ma tension gashes representing the latest isotopically dateable stage of structural evolution were formed at 210 ma at conditions of 230 c at 1 5 3 kbar as constrained by fluid inclusion data zircon fission track data indicate final cooling to below 200 c at 186 24 ma the results suggest continuous basal accretion for at least 50 ma with long term average exhumation rates of 0 6 0 2 mm a most probably outbalanced by similar long term average erosion rates changing plate boundary conditions at about 210 200 ma terminated the accretion process as evident from a dramatic decrease of exhumation rates at that time since then the paleoaccretionary wedge remained stably in place despite its delicate geotectonic position within the andean active margin the tectonochronologic approach complements thermochronologic and geomorphologic methods of exhumation research as it provides direct constraints on mass flux rates even for high temperature increments of p t trajectories

saturated and subcooled hydrothermal boiling in groundwater flow channels as a source of harmonic tremor the potential of hydrothermal boiling in groundwater flow channels for generating harmonic tremor a relatively monochromatic ground vibration associated with volcanic activity is examined we use simple organ pipe theory of normal mode fluid vibration and fundamental energy considerations to develop a first order analytical model of a hydrothermal boiling source of harmonic tremor we use this model to estimate order of magnitude groundwater flow channel lengths and boiling heat transfer rates required to produce harmonic tremor with dominant frequencies in the range 0 5 5 hz and surface wave reduced displacements of up to 100 cm2 depending on groundwater sound speed flow channel lengths of the order of 1 1000 m are required to produce fluid vibration eigenfrequencies in the range 0 5 5 hz the boiling heat transfer rate required to produce tremor with a given surface wave reduced displacement depends on the tremor frequency and on whether saturated boiling or subcooled boiling is the cause of the tremor saturated boiling produces groundwater vibration via steam bubble growth whereas subcooled boiling produces groundwater vibration via steam bubble collapse we find that subcooled hydrothermal boiling is from 102 to 104 times more efficient than saturated boiling in converting boiling thermal power to seismic power for example the boiling heat transfer rates required to produce 1 hz tremor with reduced displacements of up to 100 cm2 via subcooled boiling are generally less than a few thousand megawatts for saturated boiling the required boiling heat transfer rates are several orders of magnitude larger than this the highest values of heat flow reported in the literature for volcanic crater lakes and terrestrial and ocean floor geothermal areas are of the order of 1000 mw taking this value as a first order estimate of an upper limit on possible boiling heat transfer rates in volcanic hydrothermal systems our results suggest that saturated hydrothermal boiling is capable of generating only low amplitude harmonic tremor with surface wave reduced displacements no higher than a few square centimeters however subcooled hydrothermal boiling could potentially generate high amplitude harmonic tremor with reduced displacements as large as several hundred square centimeters as a specific application of our model we evaluate the potential of hydrothermal boiling for generating harmonic tremor at recently active mount st helens and nevado del ruiz volcanoes we conclude that subcooled boiling likely could have produced the tremor episodes considered at both volcanoes saturated boiling also could explain the nevado del ruiz tremor but probably not the more powerful mount st helens tremor

episodic development of a convergent margin inferred from structures and processes along the southern chile margin seismic reflection data acquired in the vicinity of isla mocha across the southern coast of chile image structures formed along the continental margin and reveal an episodic history of accretion nonaccretion and possibly erosion structures formed at the toe of the continental slope suggest frontal accretion of to 1 km of trench fill seismic images also reveal that a small accretionary wedge 20 30 km wide abuts the truncated continental metamorphic basement that extends seaward from beneath the shelf the small size of the accretionary wedge on three profiles examined here is not consistent with a long history of accretion with the current deformational style as current rates of frontal accretion could have accumulated all of the existing accretionary wedge in less than 1 2 m y this is a small fraction of convergence history along this margin and the current accretionary mode has not been consistently maintained in the past the isla mocha region is located between the temperate climate of central chile and the glacial climate of southern chile and climatic conditions in this region have likely fluctuated sufficiently to cause significant variation in trench sediment supply accretionary and nonaccretionary or erosional episodes are probably linked to temporal variations in trench sediment thickness as suggested by observations along the chile margin currently thick trench sediment correlates with accretion along the southern chile margin and thin trench sediment correlates with nonaccretion tectonic erosion as near the chile ridge and from the juan fernandez ridge to northern chile the isla mocha region also lies 900 1000 km north of the chile triple junction and the chile ridge lies approximately 2000 km to the west and has not yet collided and affected the margin near isla mocha this part of the precollision zone provides an excellent reference to examine the effects of chile ridge collision in the development of the chile margin the most apparent effect of subduction of the buoyant young crust of the chile ridge is a shallow trench that is nearly devoid of sediment consequently the triple junction is undergoing nonaccretion or erosion and the accretionary complex near the triple junction remains smaller than to the north or south because the current phase of rapid accretion elsewhere in the trench has bypassed the triple junction region the interplay of subduction zone processes such as trench sedimentation and ridge collision has resulted in an episodic development of the margin and produced a discontinuous record of convergence history within the accretionary wedge

late miocene high and rapid surface uplift and its erosional response in the andes of central chile 33 35 s 1 we address the question of the late cenozoic geomorphological evolution of the central chile andes 33 35 s using uplift markers river incision previous and new ages of volcanic bodies and new fission track ages the uplift markers consist of relicts of high elevated peneplains that evidence 2 km of regional surface uplift lasting 2 ma with variable amount along an e w transect the eastern coastal cordillera was uplifted 1 5 2 1 km at 33 34 s and 2 5 at 33 45 s and 1 5 km at 34 30 s erosional response to uplift was characterized by the retreat of a sharp knickpoint with celerities between 10 and 40 mm a 1 extrapolation using a stream power law shows that uplift began shortly before 4 ma or at 10 5 4 6 ma 7 6 ma central age depending on the morphostructural units involved the first alternative implies simultaneous uplift of the continental margin the second model the most reliable one implies that the uplift affected together the eastern coastal cordillera and the principal cordillera while the rest of the western fore arc subsided this regional uplift can be mostly balanced by crustal thickening resulting from coeval shortening related to the out of sequence thrusting event in the principal cordillera and the uplift of the frontal cordillera simultaneously emplacement of the southern edge of the flat slab subduction zone might have partially contributed to this uplift event

modeling the dynamics of a phreatic eruption based on a tilt observation barrier breakage leading to the 2014 eruption of mount ontake japan although phreatic eruptions are common volcanic phenomena that sometimes result in significant disasters their dynamics are poorly understood in this study we address the dynamics of the phreatic eruption of mount ontake japan in 2014 based on analyses of a tilt change observed immediately 450 s before the eruption onset we conducted two sets of analysis a waveform inversion and a modified phase space analysis our waveform inversion of the tilt signal points to a vertical tensile crack at a depth of 1100 m our modified phase space analysis suggests that the tilt change was at first a linear function in time that then switched to exponential growth we constructed simple analytical models to explain these temporal functions the linear function was explained by the boiling of underground water controlled by a constant heat supply from a greater depth the exponential function was explained by the decompression induced boiling of water and the upward darcy flow of the water vapor through a permeable region of small cracks that were newly created in response to ongoing boiling we interpret that this region was intact prior to the start of the tilt change and thus it has acted as a permeability barrier for the upward migration of fluids it was a breakage of this barrier that led to the eruption

modification of wave cut and faulting controlled landforms from a casual observation that the form of degraded fault scarps resembles the error function this investigation proceeds through an elementary diffusion equation representation of landform evolution to the application of the resulting equations to the modern topography of scarplike landforms the morphologic observations can be analyzed either in the form of one or more cross strike elevation profiles or in the form of the slope offset plot a point plot of maximum scarp slope versus scarp offset working with either or both of these data representations for nine geologic structures which range in age from 3 to 400 ka b p and in offset from 1 to 50 m we apply analytical solutions for the vertical initial value scarp the vertical continuous offset scarp and the finite slope initial value scarp the model calculations are intrinsically ambiguous yielding as the final answer only the product t in the case of the initial value problem or the product a 1 in the case of the repeated faulting problem here t is the age of a single scarp forming event 2a is the vertical slip rate and is the mass diffusivity a single profile across three sea cliffs along the santa cruz california coast is analyzed as three separate initial value problems a reasonably constrained age for the sea cliff standing above the highway 1 platform returns 11 gkg 1 gkg 1 m2 ka with this we can date the two older sea cliffs in fact we do the converse age estimates for these two older sea cliffs based on a uniform rate of uplift both yield the same as for the lower sea cliff we treat a single profile of the raymond fault in pasadena san marino in terms of the repeated faulting problem for it the uplift rate of r crook and others yields 16 gkg the very substantial preexisting offset across the raymond fault must have been buried leveled some 230 ka b p when the modern topography began to form our analysis of the lake bonneville shoreline scarps reveals a dependence of t on 2a suggestive of nonlinear modification processes this appearance is treated with the finite slope initial value scarp model to determine 1 1 gkg for the lake bonneville shoreline scarps the suggestion of m n machette that approximately 100 000 year old meter high scarps are unobservable in weakly consolidated alluvial terranes of the basin and range and rio grande rift valley provinces can be formulated as 1 gkg the coincidence between this inequality and the lake bonneville shoreline is striking and it suggests that the value of 1 gkg may be generally applicable as a good first approximation to the modification of alluvial terranes within the semiarid regions of the western united states the lake bonneville shoreline is the basis for dating four sets of fault scarps in west central utah the drum mountains fault scarps can be modeled in several different circumstances but the most likely interpretation is that these fault scarps formed as the result of a single episode of normal faulting 3 6 to 5 7 ka b p the younger age is associated with quite low initial slope angles 25 the other three sets of fault scarps show no evidence for finite initial value slopes fault scarps along the eastern base of the fish springs range are very young 3 ka b p we estimate the age of fault scarps along the western flank of the oquirrh mountains to be 32 ka b p which meets the weak geologic constraint that they be older than the lake bonneville shoreline fault scarps along the northeastern margin of the sheeprock mountains are even older 53 ka b p an intriguing consequence of our single event analysis of these scarps is that an 11 5 m offset occurred in a single earthquake

the southern andes between 36 and 40 s latitude seismicity and average seismic velocities abstract the project issa 2000 integrated seismological experiment in the southern andes consists of a temporary seismological network and a seismic refraction profile a network of 62 seismological stations was deployed across the southern andes at 38 s three hundred thirty three local seismic events were observed in a 3 month period p and s arrival times of a subset of high quality data were inverted simultaneously for 1 d velocity structure hypocentral coordinates and station delays seismic refraction data along a transect at 39 s provide further constraints on the crustal structure low crustal velocities beneath the forearc may be either due to subducted trench sediments or serpentinized mantle material of the continental lithosphere the continental moho is not clearly observed in this region average velocities of the crust beneath the arc are higher than those beneath the forearc crustal thickness is about 40 km crustal seismicity concentrates in the forearc region along the bio bio and gastre fault zones the area between these two prominent fault zones seems to be nearly devoid of crustal seismicity but shows highest uplift and topography in the forearc region benioff seismicity is observed down to 150 km depth resulting in the first accurate image of the benioff zone in the southern andes a maximum of seismicity at 60 km depth may be caused by dehydration embrittlement

response of a volcanic conduit to step like change in magma pressure freely damped oscillations associated with strain offsets were observed by a nearby volumetric strainmeter during the 1986 izu oshima volcano eruption japan these events are interpreted as a response of the magma filled conduit to step like changes in magma pressure there were dramatic changes in the characteristic frequency of oscillation and the polarity of initial motion before and after the 6 hour interval of the enormous ground deformation due presumably to magma intrusion the frequency changed from 42 6 to 21 3 mhz and the polarity changed from contraction to expansion we propose a conceptual conduit model to explain this polarity reversal where magma is episodically supplied to the conduit before but is episodically drained back to the reservoir after an extensive magma escape away from the reservoir as dike intrusion stress caused by the dike intrusion is large enough to break the lid of the conduit thus to change a boundary condition this change in boundary condition reduces the frequency of oscillation by a factor of 2 in this model longitudinal wave speed of the magma fluid is 340 m s if the conduit length is taken to be 4 km

ice volcano interaction of the 1996 gjalp subglacial eruption vatnajokull iceland volcanic eruptions under glaciers can cause dangerous floods and lahars1 2 3 and create hyaloclastite fragmented glassy rock mountains4 5 6 7 8 but processes such as the rate of heat transfer between ice and magma edifice formation and the response of the surrounding glacier are poorly understood because of the lack of data here we present observations from the fissure eruption at vatnajokull ice cap iceland in october 1996 in the 13 days of the eruption 3 km3 of ice were melted and the erupted magma fragmented into glass forming a hyaloclastite ridge 6 7 km long and 200 300 m high under 500 750 m of ice meltwater of temperatures of 15 20 c flowed along a narrow channel at the glacier bed into the grimsvotn subglacial lake for five weeks before draining in a sudden flood or jokulhlaup subsidence and crevassing of the ice cap occurred over the eruptive fissure and the meltwater path whereas elsewhere the glacier surface remained intact suggesting that subglacial eruptions do not trigger widespread basal sliding in warm based glaciers

active tectonics of the south chilean marine fore arc 35 s 40 s the south chilean marine fore arc 35 s 40 s is separated into four tectonic segments concepcion north concepcion south nahuelbuta and tolten from north to south these are each characterized by their individual tectonic geomorphology and reflect different ways of mechanical and kinematic interaction of the convergent nazca and south american plates splay faults that cut through continental framework rock are seismically imaged in both concepcion segments and the tolten segment additionally the concepcion south segment exhibits prominent upper plate normal faults normal faults apparently relate to uplift caused by sediment underthrusting at depth this has led to oversteepening and gravitational collapse of the marine fore arc there is also evidence for sediment underthrusting and basal accretion to the overriding plate in the tolten segment there uplift of the continental slope has created a landward inclined seafloor over a latitudinal distance of 50 km in the nahuelbuta segment transpressive upper plate faults aligned oblique to the direction of plate motion control the seafloor morphology based on a unique acoustic data set including 90 of bathymetric coverage of the continental slope we are able to reveal an along strike heterogeneity of a complexly deformed marine fore arc which had escaped attention in previous studies that only considered the structure along transects normal to the plate margin

statistical analysis of the volcano seismicity during the 2007 crisis of stromboli italy 1 we analyze the volcano seismicity recorded during the pre and co eruptive regimes of the 2007 effusive crisis at stromboli volcano italy data set is composed of the continuous recordings of a three component broad band seismometer and of a sacks evertson strainmeter starting from the characterization of the non effusive phase as a stationary state of equilibrium we investigate the effusive phase as a non equilibrium state a statistical analysis reveals that the explosion occurrence is always driven by a nearly poissonian process as for the standard activity even during the effusive phase with the only difference in shortening the inter times explosion quake amplitudes are lognormally distributed until the effusive phase becoming then broader this indicates that many scales are involved a slightly different process can be advocated for the swarms of the explosions occurring during the effusive phase this suggests that the dynamics of the exsolution and or aggregation of the gas slugs should differ from the nucleation mechanism responsible of the standard strombolian activity the pre eruptive regime is characterized by a very long deformative signal that appears as a transient oscillating signal with a period of about three days that modulates the explosion amplitudes in a conceptual vibrating cavities model it is related to a chocking phenomenon induced by magma injection which in turn leads to the effusion

localized fault slip to the trench in the 2010 maule chile mw 8 8 earthquake from joint inversion of high rate gps teleseismic body waves insar campaign gps and tsunami observations the 27 february 2010 mw 8 8 maule earthquake ruptured 500 km along the plate boundary offshore central chile between 34 s and 38 5 s establishing whether coseismic fault offset extended to the trench is important for interpreting both shallow frictional behavior and potential for tsunami earthquakes in the region joint inversion of high rate gps teleseismic body waves interferometric synthetic aperture radar insar campaign gps and tsunami observations yields a kinematic rupture model with improved resolution of slip near the trench bilateral rupture expansion is resolved in our model with relatively uniform slip of 5 10 m downdip beneath the coast and two near trench high slip patches with 12 m displacements the peak slip is 17 m at a depth of 15 km on the central megathrust located 200 km north from the hypocenter and overlapping the rupture zone of the 1928 m 8 event the updip slip is 16 m near the trench another shallow near trench patch is located 150 km southwest of the hypocenter with a peak slip of 12 m checkerboard resolution tests demonstrate that correctly modeled tsunami data are critical to resolution of slip near the trench with other data sets allowing but not requiring slip far offshore large interplate aftershocks have a complementary distribution to the coseismic slip pattern filling in gaps or outlining edges of large slip zones two clusters of normal faulting events locate seaward along the plate motion direction from the localized regions of large near trench slip suggesting that proximity of slip to the trench enhanced extensional faulting in the underthrusting plate

differential uplift along the northern margin of the central anatolian plateau inferences from marine terraces abstract emerged marine terraces and paleoshorelines along plate margins are prominent geomorphic markers that can be used to quantify the rates and patterns of crustal deformation the northern margin of the central anatolian plateau has been interpreted as an actively deforming orogenic wedge between the north anatolian fault and the black sea here we use uplifted marine terraces across principal faults on the sinop peninsula at the central northern side of the pontide orogenic wedge to unravel patterns of quaternary faulting and orogenic wedge behavior we leveled the present day elevations of paleoshorelines and dated marine terrace deposits using optically stimulated luminescence osl to determine coastal uplift the elevations of the paleoshorelines vary between 4 0 2 and 67 1 4 m above sea level and osl ages suggest terrace formation episodes during interglacial periods at ca 125 190 400 and 570 ka corresponding to marine isotopic stages mis 5e 7a 11 and 15 mean apparent vertical displacement rates without eustatic correction deduced from these terraces range between 0 02 and 0 18 mm a with intermittent faster rates of up to 0 26 mm a we obtained higher rates at the eastern and southern parts of the peninsula toward the hinterland indicating non uniform uplift across the different morphotectonic segments of the peninsula our data are consistent with active on and offshore faulting across the sinop peninsula when integrated with regional tectonic observations the faulting pattern reflects shortening distributed over a broad region of the northern margin of the central anatolian plateau during the quaternary

segmentation of the 2010 maule chile earthquake rupture from a joint analysis of uplifted marine terraces and seismic cycle deformation patterns abstract the segmentation of major fault systems in subduction zones controls earthquake magnitude and location but the causes for the existence of segment boundaries and the relationships between long term deformation and the extent of earthquake rupture are poorly understood we compare permanent and seismic cycle deformation patterns along the rupture zone of the 2010 maule earthquake m8 8 which ruptured 500 km of the chile subduction margin we analyzed the morphology of mis 5 marine terraces using lidar topography and established their chronology and coeval origin with twelve luminescence ages stratigraphy and geomorphic correlation obtaining a virtually continuous distribution of uplift rates along the entire rupture zone the mean uplift rate for these terraces is 0 5 m ka this value is exceeded in three areas which have experienced rapid emergence of up to 1 6 m ka they are located at the northern central and southern sectors of the rupture zone referred to as topocalma carranza and arauco respectively the three sectors correlate with boundaries of eight great earthquakes dating back to 1730 the topocalma and arauco sectors located at the boundaries of the 2010 rupture consist of broad zones of crustal warping with wavelengths of 60 and 90 km respectively these two regions coincide with the axes of oroclinal bending of the entire andean margin and correlate with changes in curvature of the plate interface rapid uplift at carranza in turn is of shorter wavelength and associated with footwall flexure of three crustal scale normal faults the uplift rate at carranza is inversely correlated with plate coupling as well as with coseismic slip suggesting permanent deformation may accumulate interseismically we propose that the zones of upwarping at arauco and topocalma reflect changes in frictional properties of the megathrust resulting in barriers to the propagation of great earthquakes slip during the 1960 m9 5 and 2010 events overlapped with the 90 km long zone of rapid uplift at arauco similarly slip in 2010 and 1906 extended across the 60 km long section of the megathrust at topocalma but this area was completely breached by the 1730 m 9 event which propagated southward until carranza both arauco and topocalma show evidence of sustained rapid uplift since at least the middle pleistocene these two sectors might thus constitute discrete seismotectonic boundaries restraining most but not all great earthquake ruptures based on our observations such barriers might be breached during multi segment super cycle events

the 2010 mw 8 8 chile earthquake triggering on multiple segments and frequency dependent rupture behavior 1 multi frequency back projection results of the february 27 2010 mw 8 8 chile earthquake reveal that this earthquake consists of distinct subevents with different slip characteristics the subevent south of the epicenter releases its energy at low frequencies 0 05 0 1 hz implying slow slip and has a rupture speed around 0 8 km s two subevents north of the epicenter are characterized by high frequency energy 1 5 hz release the first of these subevents appears to trigger slip on the second segment to the north which has higher amplitude energy release and a fast propagation speed of about 2 9 km s in addition to these rupture details high frequency energy release is observed at the rupture front followed by lower frequency energy release this observation suggests that the rupture of large earthquakes involves dynamic weakening of faults and hence their rupture properties may not be related easily to those of small earthquakes these distinct slip behaviors point out the need to consider data from a wide range of frequencies to fully assess the rupture process and associated hazards of giant earthquakes

toward understanding tectonic control on the mw 8 8 2010 maule chile earthquake the maule earthquake of 27th february 2010 m w 8 8 affected similar to 500 km of the nazca south america plate boundary in south central chile producing spectacular crustal deformation here we present a detailed estimate of static coseismic surface offsets as measured by survey and continuous gps both in near and far field regions earthquake slip along the megathrust has been inferred from a joint inversion of our new data together with published gps insar and land level changes data using green s functions generated by a spherical finite element model with realistic subduction zone geometry the combination of the data sets provided a good resolution indicating that most of the slip was well resolved coseismic slip was concentrated north of the epicenter with up to 16 m of slip whereas to the south it reached over 10 m within two minor patches a comparison of coseismic slip with the slip deficit accumulated since the last great earthquake in 1835 suggests that the 2010 event closed a mature seismic gap slip deficit distribution shows an apparent local overshoot that highlight cycle to cycle variability which has to be taken into account when anticipating future events from interseismic observations rupture propagation was obviously not affected by bathymetric features of the incoming plate instead splay faults in the upper plate seem to have limited rupture propagation in the updip and along strike directions additionally we found that along strike gradients in slip are spatially correlated with geometrical inflections of the megathrust our study suggests that persistent tectonic features may control strain accumulation and release along subduction megathrusts c 2012 elsevier b v all rights reserved

upper plate deformation and seismic barrier in front of nazca subduction zone the chololo fault system and active tectonics along the coastal cordillera southern peru abstract the south america plate boundary is one of the most active subduction zone the recent mw 8 4 arequipa 2001 earthquake ruptured the subduction plane toward the south over 400 km and stopped abruptly on the ilo peninsula in this exact region the subduction seismic crisis induced the reactivation of continental fault systems in the coastal area we studied the main reactivated fault system that trends perpendicular to the trench by detailed mapping of fault related geomorphic features also at a longer time scale a recurrent quaternary transtensive tectonic activity of the cfs is expressed by offset river gullies and alluvial fans the presence of such extensional fault systems trending orthogonal to the trench along the coastal cordillera in southern peru is interpreted to reflect a strong coupling between the two plates in this particular case stress transfer to the upper plate at least along the coastal fringe appears to have induced crustal seismic events that were initiated mainly during and after the 2001 earthquake the seafloor roughness of the subducting plate is usually thought to be a cause of segmentation along subduction zones however after comparing and discussing the role of inherited structures within the upper plate to the subduction zone segmentation in southern peru we suggest that the continental structure itself may exert some feedback control on the segmentation of the subduction zone and thus participate to define the rupture pattern of major subduction earthquakes along the southern peru continental margin

reconstruction of paleo wave conditions during the late pleistocene from marine terrace deposits monterey bay california the santa cruz coastal terrace fringes much of the northern monterey bay region california it consists mainly of a regressive sequence of high energy barred nearshore marine sediments deposited during the last sangamonian highstand of sea level this sequence can be sub divided into several depth dependent facies on the basis of paleo current data and vertical sequence of sedimentary structures these include a lower shoreface facies deposited in 10 16 m water depth an upper shoreface facies including both a storm dominated assemblage and a surf zone assemblage deposited in 0 10 m water depth and a foreshore facies deposited in the swash zone up to 3 5 m above high tide the magnitudes of the storm events responsible for depositing these sediments were estimated by calculating paleo wave heights using a variety of criteria e g critical threshold equations breaker depths berm heights in addition the climate and paleogeography during the deposition of these sediments were essentially the same as today allowing the use of present day wave statistics to estimate the frequency of these storm events the largest storms formed offshore flowing currents e g rip wind forced and possibly storm surge ebb currents that resulted in the deposition of approximately 30 of the sediments seaward of the surf zone however the magnitude and frequency of these events are unknown the remaining 70 of the sediment beyond the surf zone was deposited in response to smaller storm waves which were on the average at least 1 6 m high such waves presently occur no more than 15 of the time sediments deposited during fairweather conditions i e the remaining 85 of the time have a low preservation potential and are generally not preserved in this facies in contrast surf zone sediments were deposited by a variety of processes associated with waves whose maximum offshore heights were probably 2 2 m such waves presently occur up to 92 of the time sediments within the swash zone were deposited by waves up to 3 m high the largest of which presently occur approximately 2 of the time most of the sediments were deposited by storms of intermediate magnitude and frequency different facies however appear to preferentially record events of different recurrence intervals in particular surf zone sediments were deposited under relatively small storm and post storm conditions whereas sediments deposited farther offshore record increasingly larger less frequent storm events relatively rare events e g the 100 or 1000 yr events do not appear to have significantly affected sedimentation in these nearshore environments

deterministic non linear source processes of volcanic tremor signals accompanying the 1996 vatnajokull eruption central iceland summary observations and theoretical considerations have cast doubt on the suggestion that volcanic tremor source processes may be modelled by a linear oscillator that is set into resonance by a sustained disturbance volcanic tremor signals that accompanied the 1996 vatnajokull subglacial eruption central iceland have been analysed using methods from the discipline of non linear dynamics in order to investigate the possibility that they originated from a non linear source the volcano seismic phenomena associated with the eruption were recorded by a permanent network equipped with broad band seismometers hotspot using a sampling rate of 20 samples s 1 the eruption was preceded by increased seismic activity for a period of 2 days which also included a large earthquake with a moment magnitude of 5 6 the tremor during the first 2 days of the eruption has a high signal to noise ratio at the nearest station to the eruption site and starts as a continuous signal later evolving to low amplitude background tremor interrupted by high amplitude cigar shaped bursts having an average duration of 250 s the phase space which describes the evolution of the behaviour of a non linear system was reconstructed from the original tremor seismograms using the delay embedding theorem suggested by takens the delay time used for the reconstruction was selected after examining the autocorrelation function which showed a first zero crossing at a timelag of 4 samples and the average mutual information that showed no minimum indicating that the tremor process may have been undersampled based also on phase space portraits for different delay times a delay time of one sample interval 0 05 s was used the sufficient embedding dimension for phase space reconstruction was selected by applying the false nearest neighbours method which revealed complete unfolding of the tremor attractor at dimensions 7 8 implying upper bounds of its fractal dimension in the range 3 5 4 0 the phase space prediction errors of different segments of the tremor time series were compared in order to check whether the attractor dynamics change substantially with time it was found that for continuous tremor there was almost no dynamic variation in contrast to the background tremor and the superposed bursts that gave a maximum prediction error when the former was used to predict the latter this difference in dynamics also had an effect on their spectra the amplitude spectrum of a burst or continuous tremor has a much sharper decay at high frequencies than that of the background tremor a possible physical mechanism that may explain these observed characteristics involves turbulent slug flow of magma in a narrow cylindrical conduit generating the different dynamic regimes as the reynolds number varies

active faulting and heterogeneous deformation across a megathrust segment boundary from gps data south central chile 36 39 s 1 this study focuses on the present day deformation mechanisms of the south central chile margin at the transition zone between two megathrust earthquake segments defined from historical data the valdivia and concepcion sectors new gps data and finite element models with complex geometries constrained by geophysical data are presented to gain insight into forearc kinematics and to address the role of upper plate faults on contemporary deformation gps vectors are heterogeneously distributed in two domains that follow these two earthquake segments we find that models which simulate only interseismic locking on the plate interface fail to reproduce surface deformation in the entire study area in the concepcion domain models that include a crustal scale fault in the upper plate better reproduce the gps observations in the valdivia domain gps data show regional scale vertical axis rotations which could reflect postseismic deformation processes at the edge of the mw 9 5 earthquake that ruptured in 1960 and or activity of another crustal fault related to motion of a forearc sliver our study suggests that upper plate faults in addition to earthquake cycle transients may exert an important control on the surface velocity of subduction zone forearcs

interseismic coupling segmentation and mechanical behavior of the central chile subduction zone global positioning system gps measurements carried out in chile over the last two decades showed that an entire portion of the nazca south america subduction zone 38 s 24 s was locked over this period of time the induced accumulation of elastic deformation in the upper plate was not released until the recent maule earthquake of 27 february 2010 mw 8 8 that ruptured the southern part of this section locking or coupling between the two plates varies both with depth and along strike here we use our own gps data an updated solution of our extended network in central chile combined with other published data sets to quantify the spatial variations of the coupling that prevailed before the maule earthquake using a simple elastic model based on the back slip assumption we show that coupling variations on the subduction plane are sufficient to explain the observed surface deformation with no need of a sliver in central chile we identify four segments characterized by higher coupling and separated by narrow areas of lower coupling this segmentation is in good agreement with historical and recent seismicity in chile in particular the narrow zones of lower coupling seem to have stopped most large seismic ruptures including maule s these zones are often associated with irregular bathymetric or coastal features fracture zones or peninsulas finally coseismic and early post seismic slip distribution of the maule earthquake occurring either in previously highly or weakly coupled zones map a complex distribution of velocity weakening and velocity strengthening patches on the subduction interface

arc segmentation and seismicity in the solomon islands arc sw pacific abstract this paper evaluates neotectonic segmentation in the solomon islands forearc and considers how it relates to regional tectonic evolution and the extent of ruptures of large megathrust earthquakes we first consider regional geomorphology and quaternary vertical displacements especially uplifted coral reef terraces then we consider geographic seismicity patterns aftershock areas and vertical displacements for large earthquakes focal mechanisms and along arc variations in seismic moment release to evaluate the relationship between neotectonically defined segments and seismicity notably one major limitation of using seismicity to evaluate arc segmentation is the matter of accurately defining earthquake rupture zones for example shoreline uplifts associated with the 1 april 2007 mw 8 1 western solomons earthquake indicate that the along arc extent of rupture was about 50 km smaller than the aftershock area thus if we had relied on aftershocks alone to identify the 2007 rupture zone as we do for most historical earthquakes we would have missed the rupture s relationship to a major morphologic feature in many cases the imprecision of defining rupture zones without surface deformation data may be largely responsible for the poor mismatches to neotectonic boundaries however when a precise paleoseismic vertical deformation history is absent aftershocks are often the best available tool for inferring rupture geometries altogether we identify 16 segments in the solomon islands these comprise three major tectonic regimes or supersegments that correspond respectively to the forearc areas of guadalcanal makira the new georgia island group and bougainville islands subduction of the young and relatively shallow and buoyant woodlark basin and spreading system distinguishes the central new georgia supersegment from the two neighboring supersegments the physiographic expression of the san cristobal trench is largely absent but bathymetric mapping of the surface trace of the interplate thrust zone defines it adequately the new georgia supersegment has smaller arc segments and more islands due to general late quaternary forearc uplift very close to the trench where vertical displacement rates tend to be faster prior to the 2007 earthquake it had much lower rates of seismic activity than the neighboring supersegments generally the mean along arc lateral extent of solomon arc segments is about 75 km somewhat smaller than the segments reported in some other island arcs such as japan 100 260 km but larger than those of the tonga 30 80 km and central new hebrides arcs 30 110 km these differences may be real but it may occur simply because the coral friendly tropical environment of the south pacific arcs numerous emerged forearc islands and high seismicity rates provide an unusually favorable situation for observing variations in vertical tectonic activity and thus for identifying segment boundaries over the past century seismic slip in the solomons as indicated by seismic moment release has corresponded to about half the plate convergence rate however there are notable variations along the arc even with the 2007 earthquake the long term moment release rate in the new georgia supersegment is relatively low and this may indicate that large earthquakes are imminent

instability in flow through elastic conduits and volcanic tremor the stability of fluid flow through a narrow conduit with elastic walls is explored treating the fluid as incompressible and viscous and the walls as semi infinite linear hookean solids instabilities analogous to roll waves occur in this system we map out the physical regime in which they are excited for elastic wave speeds much higher than the fluid speed a critical reynolds number is required for instability however that critical value depends linearly on wavenumber and so can be made arbitrarily small for long waves for smaller elastic wave speeds the critical reynolds number is reduced still further and rayleigh waves can be destabilized by the fluid even at zero reynolds number a brief discussion is given of the nonlinear dynamics of the instabilities for large elastic wave speed and the significance of the results to the phenomenon of volcanic tremor is presented although magma itself seems unlikely to generate flow induced vibrations the rapid flow through fractured rock of low viscosity fluids exsolved from magma appears to be a viable mechanism for volcanic tremor

space geodetic estimation of the nazca south america euler vector abstract gps data from four sites in the nazca plate easter island galapagos robinson crusoe and san felix islands and from five sites in the stable core of the south american plate enabled us to estimate the euler vector of the nazca plate with respect to south america the observed velocities of easter island 6 6 cm yr at 102 3 galapagos 5 1 cm yr at 90 0 robinson crusoe 6 6 cm yr at 80 1 and san felix 6 0 cm yr at 82 1 are significantly slower than the global plate model nuvel 1a velocites for those four sites our estimated euler pole is located at 48 8 n 91 7 w with a rate of 0 59 m y the nuvel 1a and earlier space geodetic studies give rotation rates that are 20 faster

nonlinear time series analysis of volcanic tremor events recorded at sangay volcano ecuador the assumption that volcanic tremor may be generated by deterministic nonlinear source processes is now supported by a number of studies at different volcanoes worldwide that clearly demonstrate the low dimensional nature of the phenomenon we applied methods based on the theory of nonlinear dynamics to volcanic tremor events recorded at sangay volcano ecuador in order to obtain more information regarding the physics of their source mechanism the data were acquired during 21 26 april 1998 and were recorded using a sampling interval of 125 samples s 1 by two broadband seismometers installed near the active vent of the volcano in a previous study johnson and lees 2000 classified the signals into three groups 1 short duration 1 min impulses generated by degassing explosions at the vent 2 extended degassing chugging events with a duration 2 5 min containing well defined integer overtones 1 5 hz and variable higher frequency content 3 extended degassing events that contain significant energy above 5 hz we selected 12 events from groups 2 and 3 for our analysis that had a duration of at least 90 s and high signal to noise ratios the phase space which describes the evolution of the behavior of a nonlinear system was reconstructed using the delay embedding theorem suggested by takens the delay time used for the reconstruction was chosen after examining the first zero crossing of the autocorrelation function and the first minimum of the average mutual information ami of the data in most cases it was found that both methods yielded a delay time of 14 18 samples 0 112 0 144 s for group 2 and 5 samples 0 04 s for group 3 events the sufficient embedding dimension was estimated using the false nearest neighbors method which had a value of 4 for events in group 2 and was in the range 5 7 for events in group 3 based on these embedding parameters it was possible to calculate the correlation dimension of the resulting attractor as well as the average divergence rate of nearby orbits given by the largest lyapunov exponent events in group 2 exhibited lower values of both the correlation dimension 1 8 2 6 and largest lyapunov exponent 0 013 0 022 in comparison with the events in group 3 where the values of these quantities were in the range 2 4 3 5 and 0 029 0 043 respectively theoretically a nonlinear oscillation described by the equation g x fcos t can generate deterministic signals with characteristics similar to those observed in groups 2 and 3 as the values of the parameters f are drifting causing instability of orbits in the phase space

coastal staircase sequences reflecting sea level oscillations and tectonic uplift during the quaternary and neogene many coasts feature sequences of quaternary and neogene shorelines that are shaped by a combination of sea level oscillations and tectonics we compiled a global synthesis of sea level changes for the following highstands mis 1 mis 3 mis 5e and mis 11 also we date the apparent onset of sequences of paleoshorelines either from published data or tentatively extrapolating an age for the uppermost purported oldest shoreline in each sequence including the most documented mis 5e benchmark we identify 926 sequences out of which 185 also feature holocene shorelines six areas are identified where elevations of the mis 3 shorelines are known and 31 feature elevation data for mis 11 shorelines genetic relationships to regional geodynamics are further explored based on the elevations of the mis 5e benchmark mean apparent uplift rates range from 0 01 0 01 mm yr hotspots to 1 47 0 08 mm yr continental collision passive margins appear as ubiquitously uplifting while tectonic segmentation is more important on active margins from the literature and our extrapolations we infer ages for the onset of formation for 180 coastal sequences sea level fingerprinting on coastal sequences started at least during mid miocene and locally as early as eocene whether due to the changes in the bulk volume of seawater or to the temporal variations in the shape of ocean basins estimates of eustasy fail to explain the magnitude of the apparent sea level drop thus vertical ground motion is invoked and we interpret the long lasting development of those paleoshore sequences as the imprint of glacial cycles on globally uplifted margins in response to continental compression the geomorphological expression of the sequences matches the amplitude and frequency of glacial cyclicity from middle pleistocene to present day moderately fast 100 000 yrs oscillating sea levels favor the development of well identified strandlines that are distinct from one another pliocene and lower pleistocene strandlines associated with faster cyclicity 40 000 yrs are more compact and easily merge into rasas whereas older cenozoic low frequency eustatic changes generally led to widespread flat lying coastal plains

age estimates and uplift rates for late pleistocene marine terraces southern oregon portion of the cascadia forearc marine terraces are prominent landforms along the southern oregon coast which forms part of the forearc region of the cascadia subduction zone interest in the cascadia subduction zone has increased because recent investigations have suggested that slip along plates at certain types of convergent margins is characteristically accompanied by large earthquakes in addition other investigations have suggested that convergent margins can be broadly classified by the magnitude of their uplift rates with these hypotheses in mind we generated new uranium series amino acid and stable isotope data for southern oregon marine terrace fossils these data along with terrace elevations and two alternative estimates of sea level at the time of terrace formation allow us to determine terrace ages and uplift rates uranium series analysis of fossil coral yields an age of 83 5 ka for the whisky run terrace at coquille point in bandon oregon a combination of amino acid and oxygen isotope data suggest ages of about 80 and 105 ka for the lowest two terraces at cape blanco these ages indicate uplift rates of 0 45 1 05 and 0 81 1 49 m kyr for coquille point and cape blanco respectively late quaternary uplift rates of marine terraces yield information about deformation in the overriding plate but it is unclear if such data vary systematically with convergent margin type in order to assess the utility of the southern oregon uplift rates for predicting the behavior of the cascadia subduction zone we compared late quaternary uplift rates derived from terrace data from subduction zones around the world on the basis of this comparison the southern oregon rates of vertical deformation are not unusually high or low furthermore late quaternary uplift rates show little relationship to the type of convergent margin these observations suggest that local structures may play a large role in uplift rate variability in addition while the type of convergent margin may place an upper limit on possible uplift rate greater upper limits serve to increase the range of possible uplift rates in the case of the southern oregon coast variability in uplift rate probably reflects local structures in the overriding plate and the rate of uplift cannot be used as a simple index of the potential for great earthquakes along the southern cascadia subduction zone

detailed investigation of long period activity at campi flegrei by convolutive independent component analysis abstract this work is devoted to the analysis of seismic signals continuously recorded at campi flegrei caldera italy during the entire year 2006 the radiation pattern associated with the long period energy release is investigated we adopt an innovative independent component analysis algorithm for convolutive seismic series adapted and improved to give automatic procedures for detecting seismic events often buried in the high level ambient noise the extracted waveforms characterized by an improved signal to noise ratio allows the recognition of long period precursors evidencing that the seismic activity accompanying the mini uplift crisis in 2006 which climaxed in the three days from 26 28 october had already started at the beginning of the month of october and lasted until mid of november hence a more complete seismic catalog is then provided which can be used to properly quantify the seismic energy release to better ground our results we first check the robustness of the method by comparing it with other blind source separation methods based on higher order statistics secondly we reconstruct the radiation patterns of the extracted long period events in order to link the individuated signals directly to the sources we take advantage from convolutive independent component analysis that provides basic signals along the three directions of motion so that a direct polarization analysis can be performed with no other filtering procedures we show that the extracted signals are mainly composed of p waves with radial polarization pointing to the seismic source of the main lp swarm i e a small area in the solfatara also in the case of the small events that both precede and follow the main activity from a dynamical point of view they can be described by two degrees of freedom indicating a low level of complexity associated with the vibrations from a superficial hydrothermal system our results allow us to move towards a full description of the complexity of the source which can be used by means of the small intensity precursors for hazard model development and forecast model testing showing an illustrative example of the applicability of the cica method to regions with low seismicity in high ambient noise

spatial correlation of interseismic coupling and coseismic rupture extent of the 2011 mw 9 0 tohoku oki earthquake 1 imaging the extent to which the rupture areas of great earthquakes coincide with regions of pre seismic interplate coupling is central to understanding patterns of strain accumulation and release through the earthquake cycle both geodetic and seismic estimates of the coseismic rupture extent for the march 11 2011 mw 8 9 9 0 earthquake tohoku oki earthquake may be spatially correlated 0 26 0 05 to 0 82 0 05 with a region estimated to be partially to fully coupled in the interseismic period preceding the earthquake though there is substantial variation in the estimated distribution and magnitude of coseismic slip the 400 km long region estimated to have slipped 4 m corresponds to an area of the subduction zone interface that was coupled at 30 of long term plate convergence rate with peak slip near a region coupled 80 the northern termination of rupture is collocated with a region of relatively low 20 interseismic coupling near the epicenter of the 1994 mw 7 6 sanriku oki earthquake and near a region of potential long term low coupling or ongoing slow slip slip on the subduction interface beneath the coastline 40 50 km depth is best constrained by the land based gps data and least constrained on the shallowest portion of the plate interface due to the 230 km distance between geodetic observations and the japan trench

crustal earthquake triggering by pre historic great earthquakes on subduction zone thrusts triggering of earthquakes on upper plate faults during and shortly after recent great m 8 0 subduction thrust earthquakes raises concerns about earthquake triggering following cascadia subduction zone earthquakes of particular regard to cascadia was the previously noted but only qualitatively identified clustering of m 6 5 crustal earthquakes in the puget sound region between about 1200 900 cal years b p and the possibility that this was triggered by a great cascadia thrust subduction thrust earthquake and therefore portends future such clusters we confirm quantitatively the extraordinary nature of the puget sound region crustal earthquake clustering between 1200 900 cal years b p at least over the last 16 000 we conclude that this cluster was not triggered by the penultimate and possibly full margin great cascadia subduction thrust earthquake however we also show that the paleoseismic record for cascadia is consistent with conclusions of our companion study of the global modern record outside cascadia that m 8 6 subduction thrust events have a high probability of triggering at least one or more m 6 5 crustal earthquakes

the 2010 mw 8 8 maule chile earthquake nucleation and rupture propagation controlled by a subducted topographic high knowledge of seismic properties in an earthquake rupture zone is essential for understanding the factors controlling rupture dynamics we use data from aftershocks following the maule earthquake to derive a three dimensional seismic velocity model of the central chile forearc at 36 s we find a high v p 7 0 km s and high v p v s 1 89 anomaly lying along the megathrust at 25 km depth which coincides with a strong forearc bouguer gravity signal we interpret this as a subducted topographic high possibly a former seamount on the nazca slab the maule earthquake nucleated at the anomaly s updip boundary yet high co seismic slip occurred where the megathrust is overlain by lower seismic velocities sparse aftershock seismicity occurs within this structure suggesting that it disrupts normal interface seismogenesis these findings imply that subducted structures can be conducive to the nucleation of large megathrust earthquakes even if they subsequently hinder co seismic slip and aftershock activity

coseismic slip distribution of the february 27 2010 mw 8 8 maule chile earthquake 1 static offsets produced by the february 27 2010 mw 8 8 maule chile earthquake as measured by gps and insar constrain coseismic slip along a section of the andean megathrust of dimensions 650 km in length 180 km in width gps data have been collected from both campaign and continuous sites sampling both the near field and far field alos palsar data from several ascending and descending tracks constrain the near field crustal deformation inversions of the geodetic data for distributed slip on the megathrust reveal a pronounced slip maximum of order 15 m at 15 25 km depth on the megathrust offshore lloca indicating that seismic slip was greatest north of the epicenter of the bilaterally propagating rupture a secondary slip maximum appears at depth 25 km on the megathrust just west of concepcion coseismic slip is negligible below 35 km depth estimates of the seismic moment based on different datasets and modeling approaches vary from 1 8 to 2 6 1022 n m our study is the first to model the static displacement field using a layered spherical earth model allowing us to incorporate both near field and far field static displacements in a consistent manner the obtained seismic moment of 1 97 1022 n m corresponding to a moment magnitude of 8 8 is similar to that obtained by previous seismic and geodetic inversions

rates and processes of soil evolution on uplifted marine terraces northern california time dependent changes in soil development have been evaluated for two flights of uplifted marine terraces with similar site characteristics and a range in terrace ages 3 9 ka to 330 ka in northern california six pedogenic properties of soils developed in unconsolidated deposits overlying bedrock marine platforms have systematic time dependent trends but each property differs in rate of change and in the time period over which its changes are useful as relative age dating or correlation tools changes in accumulated mass of organic carbon and ph are useful properties only for the youngest soils and probably for soils less than 10 20 ka in this climatic region soils on terraces older than 29 ka have nearly similar amounts of mass of organic carbon with values of about 3 6 by weight for the upper meter of the soil profile soil reaction ph in the top 20 cm of the soil profile decreases at a rapidly declining rate reaching and maintaining a value of 5 by 39 40 ka total mass of accumulated clay is an excellent indicator of relative soil age during all stages of soil development the rate of accumulation of clay is about 0 4 g cm2 soil column per thousand years so that pedons on terraces with inferred ages of about 124 ka have accumulated at least 50 g cm2 soil column of clay systematic and linear increases in accumulated mass of several forms of pedogenic iron make them very useful for chronological purposed for at least 240 ky of soil development crystalline forms of iron enable greater distinction among young soils than amorphous forms which have negligible accumulations until at least 40 ka the rate of accumulation of crystalline forms of iron fed feo is about 0 02 g cm2 soil column per thousand years so that pedons on terraces with inferred ages of about 124 ka have accumulated about 3 g cm2 soil column of crystalline forms of pedogenic iron changes with time in accumulated mass of amorphous forms of pedogenic aluminum alo are negligible within the first 29 ka then reflect a rapid increase in rate of accumulation until at least 124 ka two pedons from the same terrace inferred age 124 ka contain strikingly different amounts of pedogenic alo however and suggest that alo may be an unreliable indicator of the degree of soil development in addition to mass values of different soil substances maximum percent values were calculated soils developed on marine terraces older than 29 ka have at least 10 maximum clay older than 100 ka at least 30 maximum clay and older than 240 ka at least 40 50 maximum clay soils on terraces younger than 29 ka have less than 1 maximum fed and soils older than 240 ka at have at least 4 maximum fed these easily obtained values provide textural and chemical boundaries for separating marine terraces younger or older than about 29 100 and 240 ka in this region but are useful only as very general tools for correlation maximum percent clay is a more reliable indicator of soil age than maximum percent fed as the latter is greatly influenced by local groundwater flux and percent values of fed have a high degree of scatter

beach and sea cliff dynamics as a driver of long term rocky coastline evolution and stability we investigate rocky coastline evolution over millennial time scales using exploratory analytical and numerical models based on interactions between beaches and sea cliffs in the models wave driven sea cliff retreat is a nonlinear function of beach width where cliff retreat is maximized by sediment abrasion and minimized by either a lack of beach sediment or too much sediment which prevents waves from reaching the sea cliff as sea cliffs retreat beach sediment is produced and distributed alongshore by wave driven sediment transport and local beach widths determine future cliff retreat rates numerical experiments indicate that through such interactions rocky coastlines can reach an equilibrium configuration where headlands and embayments remain stable through time even in the absence of alongshore variations in sea cliff lithology furthermore the equilibrium coastline configuration or the alongshore proportion of rocky headland to cliff backed pocket beach can be predicted analytically initial tests suggest that predictions match well qualitatively with actual landscapes

estimating coseismic coastal uplift with an intertidal mussel calibration for the 2010 maule chile earthquake mw 8 8 abstract coseismic coastal uplift has been quantified using sessile intertidal organisms after several great earthquakes following fitzroy s pioneer measurements in 1835 a dense survey of such markers may complement space geodetic data to obtain an accurate distribution of fault slip and earthquake segmentation however uplift estimates based on diverse intertidal organisms tend to differ because of few methodological and comparative studies here we calibrate and estimate coastal uplift in the southern segment of the 2010 maule chile earthquake m w 8 8 using 1100 post earthquake elevation measurements of the sessile mussel perumytilus purpuratus this mussel is the predominant competitor for rocky shores all along the pacific coast of south america where it forms fringes or belts distinctively in the middle intertidal zone these belts are centered at mean sea level and their width should equal one third of the tidal range we measured belt widths close to this value at 40 of the sites but overall widths are highly variable due to the unevenness in belt tops belt bases in turn are rather regular belt top unevenness apparently results from locally enhanced wave splash whereas belt base evenness is controlled by predation according to our measurements made beyond the earthquake rupture the belt base is at the bottom of the middle intertidal zone and thus we propose to estimate coastal uplift using the belt base mean elevation plus one sixth of the tidal range to reach mean sea level within errors our estimates agree with gps displacements but differ from other methods comparisons of joint inversions for megathrust slip suggest combining space geodetic data with estimates from intertidal organisms may locally increase the detail of slip distributions

permanent fore arc extension and seismic segmentation insights from the 2010 maule earthquake chile 1 geologists have long known that young normal faults are an important structural element of the andean coastal cordillera but their relationship to the subduction seismic cycle is still unclear some of the largest aftershocks of the 2010 mw 8 8 maule earthquake in central chile were nucleated on upper plate normal faults including the mw 6 9 and 7 0 events of the pichilemu earthquake sequence we use the available coseismic gps displacements moment tensor sums and slip distribution models for the maule earthquake to compute the static strain and stress fields imposed on the upper plate by slip on the subduction interface the extensional strains calculated from coseismic gps and from a moment tensor sum of the pichilemu events have similar orientations and orders of magnitude the normal coulomb stress increment csi on the pichilemu fault has maximum positive stresses as high as 4 9 mpa regionally the maule event produced a semi elliptical radial pattern of static extension and deviatoric tension csi 1 5 mpa along the coastal cordillera enclosing the rupture area this elliptical pattern mimics the trends of the major upper crustal structures the static deformation field produced by a great subduction earthquake is an effective mechanism for generating permanent extension above the seismogenic zone reactivating suitably oriented long lived normal faults we suggest that the semi elliptical outline of the first order structures along the coastal cordillera may define the location of a characteristic long lived megathrust segment this observation implies a persistence at least over the quaternary of great subduction ruptures along the maule segment

inferences on the source of long period seismicity at campi flegrei from polarization analysis and reconstruction of the asymptotic dynamics in the present paper we analyse long period lp events and seismic noise recorded at campi flegrei during the uplift episode of 2004 2006 the results of a detailed polarization analysis indicate that the large number of lps detected during the seismic crisis were accompanied by a sustained activity consisting of very low energy volcanic signals these weak volcanic signals which are usually absent in ambient noise recorded in the studied area and lp events have similar properties namely they are radially polarized towards the same lp source the large dataset analysed allows us to study the statistics of the polarization leading to the extraction of the average properties of the volcanic signals an estimate of the complexity of the system can be provided by the degrees of freedom necessary to describe the asymptotic dynamics in a reconstructed phase space this analysis shows that both lps and low energy signals can be described by a low dimensional dynamical system while ambient noise unrelated to volcanic activity is higher dimensional based on these observations we interpret the phenomena observed during the seismic crisis in the framework of the theory of self oscillating systems in which lps and low energy signals represent self oscillations generated by a persistent hydrothermal source

crustal motion in the southern andes 26 36 s do the andes behave like a microplate 1 a new global positioning system gps derived velocity field for the andes mountains 26 36 s allows analysis of instantaneous partitioning between elastic and anelastic deformation at the orogen s opposing sides adding an andes microplate to the traditional description of nazca south america plate convergence provides the kinematic framework for nearly complete explanation of the observed velocity field the results suggest the oceanic nazca boundary is fully locked while the continental backarc boundary creeps continuously at 4 5 mm yr the excellent fit of model to data 1 7 mm yr rms velocity misfit and the relative aseismicity of the upper crust in the interior andean region in comparison with its boundaries supports the notion that the mountains are not currently accruing significant permanent strains additionally the model implies permanent deformation is not accumulating throughout the backarc contractional wedge but rather that the deformation is accommodated only within a narrow deformational zone in the backarc

are rupture zone limits of great subduction earthquakes controlled by upper plate structures evidence from multichannel seismic reflection data acquired across the northern ecuador southwest colombia margin 1 subduction of the nazca plate beneath the ecuador colombia margin has produced four megathrust earthquakes during the last century the 500 km long rupture zone of the 1906 mw 8 8 event was partially reactivated by three thrust events in 1942 mw 7 8 1958 mw 7 7 and 1979 mw 8 2 whose rupture zones abut one another multichannel seismic reflection and bathymetric data acquired during the sisteur cruise show evidence that the margin wedge is segmented by transverse crustal faults that potentially correlate with the limits of the earthquake coseismic slip zones the paleogene neogene jama quininde and esmeraldas crustal faults define a 200 km long margin crustal block that coincides with the 1942 earthquake rupture zone subduction of the buoyant carnegie ridge is inferred to partially lock the plate interface along central ecuador however coseismic slip during the 1942 and 1906 earthquakes may have terminated against the subducted northern flank of the ridge we report on a newly identified manglares crustal fault that cuts transversally through the margin wedge and correlates with the limit between the 1958 and 1979 rupture zones during the earthquake cycle the fault is associated with high stress concentration on the plate interface an outer basement high which bounds the margin seaward of the 1958 rupture zone may act as a deformable buttress to seaward propagation of coseismic slip along a megathrust splay fault coseismic uplift of the basement high is interpreted as the cause for the 1958 tsunami we propose a model of weak transverse faults which reduce coupling between adjacent margin segments together with a splay fault and an asperity along the plate interface as controlling the seismogenic rupture of the 1958 earthquake

the 2010 mw 8 8 maule megathrust earthquake of central chile monitored by gps large earthquakes produce crustal deformation that can be quantified by geodetic measurements allowing for the determination of the slip distribution on the fault we used data from global positioning system gps networks in central chile to infer the static deformation and the kinematics of the 2010 moment magnitude m w 8 8 maule megathrust earthquake from elastic modeling we found a total rupture length of 500 kilometers where slip up to 15 meters concentrated on two main asperities situated on both sides of the epicenter we found that rupture reached shallow depths probably extending up to the trench resolvable afterslip occurred in regions of low coseismic slip the low frequency hypocenter is relocated 40 kilometers southwest of initial estimates rupture propagated bilaterally at about 3 1 kilometers per second with possible but not fully resolved velocity variations

2010 maule earthquake slip correlates with pre seismic locking of andean subduction zone analysis of seismic data and global positioning system gps observations from the region around the site of the recent magnitude 8 8 maule earthquake in chile have been combined with modelling of the andean subduction zone to build up a detailed image of the event the earthquake occurred at a seismic gap part of the fault that has not experienced a major earthquake since 1835 and it seems to have released most of the stress accumulated since that time the observations suggest that coseismic slip heterogeneity at the scale of single asperities and therefore the seismic potential of future great earthquakes might be anticipated by geodetic observations these authors show evidence for a high coherence between the slip distribution inferred from the 2010 maule earthquake chile and the patchwork of interseismic locking distribution derived from global positioning system observations during the previous decade their work suggests that coseismic slip heterogeneity at the scale of single asperities should indicate the seismic potential of future earthquakes which thus might be anticipated by geodetic observations the magnitude 8 8 maule chile earthquake of 27 february 2010 ruptured a segment of the andean subduction zone megathrust that has been suspected to be of high seismic potential1 2 3 4 5 6 it is the largest earthquake to rupture a mature seismic gap in a subduction zone that has been monitored with a dense space geodetic network before the event this provides an image of the pre seismically locked state of the plate interface of unprecedentedly high resolution allowing for an assessment of the spatial correlation of interseismic locking with coseismic slip pre seismic locking might be used to anticipate future ruptures in many seismic gaps6 7 8 9 10 11 12 given the fundamental assumption that locking and slip are similar this hypothesis however could not be tested without the occurrence of the first gap filling earthquake here we show evidence that the 2010 maule earthquake slip distribution correlates closely with the patchwork of interseismic locking distribution as derived by inversion of global positioning system gps observations during the previous decade the earthquake nucleated in a region of high locking gradient and released most of the stresses accumulated in the area since the last major event in 1835 two regions of high seismic slip asperities appeared to be nearly fully locked before the earthquake between these asperities the rupture bridged a zone that was creeping interseismically with consistently low coseismic slip the rupture stopped in areas that were highly locked before the earthquake but where pre stress had been significantly reduced by overlapping twentieth century earthquakes our work suggests that coseismic slip heterogeneity at the scale of single asperities should indicate the seismic potential of future great earthquakes which thus might be anticipated by geodetic observations

forearc uplift rates deduced from sediment cores of two coastal lakes in south central chile abstract the present paper introduces a new approach for deriving information about local forearc tectonics and related uplift rates based on the study of lake sediments we investigated two coastal lakes at the south central chile margin lakes lanalhue and lleu lleu located south of the arauco peninsula 38 s both lakes developed within the valleys of ancient rivers that once drained to the pacific ocean being subsequently dammed by rising sills in the late pleistocene early holocene seismic profiling and sedimentological analyses of cores from both lakes revealed similar successions consisting of marine to brackish sediments covered by lacustrine deposits radiocarbon dating indicates that the marine lacustrine transition occurred at 8 ka and 8 15 ka respectively the correlation of this transition with global sea level curves allowed the calculation of local uplift rates for the holocene uplift rates for the lake basins amount to 0 42 0 71 and 0 49 0 44 mm a respectively which are consistent with rates determined from a late pleistocene marine terrace in the area however conspicuously higher though likely transient vertical movements at 8 83 2 7 mm a and 11 36 1 77 mm a respectively were calculated for the sills that block both lakes nowadays these barriers are interpreted to be the surface expression of a blind reverse fault associated to the morguilla fault system a seismically active structure that controls uplift and folding along the adjacent arauco peninsula

pre andean orogenesis in the coast ranges of central chile an intense structural metamorphic event of probable permian triassic age is inferred from petrologic and field observations of low grade schists from the coast ranges of central chile between latitudes 38 s and 43 s relict almandine rich garnet biotite and aluminous amphibole in mafic schists are replaced by a pervasive assemblage consisting of albite chlorite epidote actinolite sphene quartz stilpnomelane white mica iron oxide chemographic analysis of phase compatibilities based on electron microprobe analyses suggests a regional retrogradation from earlier upper greenschist and or epidote amphibolite to lower greenschist facies a regional northwest southeast trending fabric within the terrane was imposed during the lower greenschist metamorphism which involved widespread reintroduction of fluids into the system this major orogenic event is thought to be the culminating episode in a subduction related accretionary process along the late paleozoic margin of south america convergence may have been markedly oblique to the present north south trending continental margin

seismic and aseismic slip on the central peru megathrust slip on a subduction megathrust can be seismic or aseismic with the two modes of slip complementing each other in time and space to accommodate the long term plate motions although slip is almost purely aseismic at depths greater than about 40 km heterogeneous surface strain suggests that both modes of slip occur at shallower depths with aseismic slip resulting from steady or transient creep in the interseismic and postseismic periods thus active faults seem to comprise areas that slip mostly during earthquakes and areas that mostly slip aseismically the size location and frequency of earthquakes that a megathrust can generate thus depend on where and when aseismic creep is taking place and what fraction of the long term slip rate it accounts for here we address this issue by focusing on the central peru megathrust we show that the pisco earthquake with moment magnitude m w 8 0 ruptured two asperities within a patch that had remained locked in the interseismic period and triggered aseismic frictional afterslip on two adjacent patches the most prominent patch of afterslip coincides with the subducting nazca ridge an area also characterized by low interseismic coupling which seems to have repeatedly acted as a barrier to seismic rupture propagation in the past the seismogenic portion of the megathrust thus appears to be composed of interfingering rate weakening and rate strengthening patches the rate strengthening patches contribute to a high proportion of aseismic slip and determine the extent and frequency of large interplate earthquakes aseismic slip accounts for as much as 50 70 of the slip budget on the seismogenic portion of the megathrust in central peru and the return period of earthquakes with m w 8 0 in the pisco area is estimated to be 250 years

a spherical source model for low frequency volcanic earthquakes a resonant magma chamber is modeled by a spherically symmetric whole space consisting of a small gas filled chamber surrounded by magma which is encased in country rock source boundary conditions are specified on the cavity boundary simulating a possible sudden gas expansion in the magma the simplicity of this model leads to an analytical closed form solution for the fourier transform of radial displacement which predicts a peaked spectrum and an oscillating decaying seismogram for physically reasonable values of the rock and magma elastic properties and dimensions of the model the dominant frequency of the signal is in the range of 1 to 5 hz near the values observed for low frequency volcanic earthquakes and volcanic tremor furthermore the seismograms and spectra bear resemblance to those observed for low frequency earthquakes the fundamental mode of oscillation is a pure radial breathing mode which has markedly different properties from single cavity solutions the fundamental frequency is insensitive to the magma chamber boundary radius when both the inner and outer radii are greater than specified values this may help to explain the apparent similarity of the dominant frequency of volcanic earthquakes over a wide range of physical situations the presence of an inner effective bubble of a certain minimum size is necessary for the existence of the dominant low fundamental frequency spectral peak although highly idealized we believe that this fundamental fluid solid cavity mode may provide an explanation for the observations of tremor and low frequency volcanic earthquakes

slip distribution of the february 27 2010 mw 8 8 maule earthquake central chile from static and high rate gps insar and broadband teleseismic data 1 the shallow depth underthrust earthquake of february 27 2010 mw 8 8 ruptured the subduction plate interface in central chile between 34 s and 38 s we retrieve the spatial and temporal distribution of slip during this mega earthquake through a joint inversion of teleseismic records insar and high rate gps hrgps data additionally our model is shown to agree with broadband surface waves rupture initiated at about 32 km depth and propagated bilaterally resulting in two main slip zones located ssw and nne of the hypocenter nucleation did not take place within or at the edge of one of these main asperities but in between during the first 30s slip propagated predominantly southwards later on the rupture evolved more slowly and more symmetrically eventually the northern asperity became predominant with maximum slip reaching about 20 m most of the seismic moment was released within 110s a relatively short time explained by the bilateral propagation the overall average rupture velocity is 2 6 km s but propagation occurred initially faster towards the south 3 2 km s large slip did not reach the trench a result consistent with the moderate size of the tsunami down dip rupture stopped at about 50 km depth in agreement with the lower limit of the locked zone inferred by ruegg et al 2009 from pre seismic gps data

long period seismicity reveals magma pathways above a laterally propagating dyke during the 2014 15 barðarbunga rifting event iceland abstract the 2014 15 bar arbunga holuhraun rifting event comprised the best monitored dyke intrusion to date and the largest eruption in iceland in 230 years a huge variety of seismicity was produced including over 30 000 volcano tectonic earthquakes vts associated with the dyke propagation at 6 km depth below sea level and large magnitude earthquakes accompanying the collapse of bar arbunga caldera we here study the long period seismicity associated with the rifting event we systematically detect and locate both long period events lps and tremor during the dyke propagation phase and the first week of the eruption we identify clusters of highly similar repetitive lps which have a peak frequency of 1 hz and clear p and s phases followed by a long duration coda the source mechanisms are remarkably consistent between clusters and also fundamentally different to those of the vts we accurately locate lp clusters near each of three ice cauldrons depressions formed by basal melting that were observed on the surface of dyngjujokull glacier above the path of the dyke most events are in the vicinity of the northernmost cauldron at shallower depth than the vts associated with lateral dyke propagation at the two northerly cauldrons periods of shallow seismic tremor following the clusters of lps are also observed given that the lps occur at 4 km depth and in swarms during times of dyke stalling we infer that they result from excitation of magmatic fluid filled cavities and indicate magma ascent we suggest that the tremor is the climax of the vertical melt movement arising from either rapid repeated excitation of the same lp cavities or sub glacial eruption processes this long period seismicity therefore represents magma pathways between the depth of the dyke vt earthquakes and the surface notably we do not detect tremor associated with each cauldron despite melt reaching the base of the overlying ice cap a concern for hazard monitoring

excitation of a buried magmatic pipe a seismic source model for volcanic tremor recent observations of seismic events at various volcanoes suggest that harmonic tremor results from the sustained occurrence of so called long period or low frequency events accordingly we can view the long period volcanic event as the elementary process of tremor and interpret it as the impulse response of the tremor generating system we present a seismic model in which the source of tremor is the acoustic resonance of a fluid filled volcanic pipe triggered by excess gas pressure the model consists of three elements namely a triggering mechanism a resonator and a radiator for simplicity we assume a hemispherical trigger cylindrial resonator and circular radiator set in a vertical configuration with the trigger capping the top of the pipe and the disk shaped radiator shutting off its bottom considering the simple case of a source buried in a homogeneous half space we then apply the discrete wave number method to obtain a complete representation of the ground motion response at near and intermediate distances the results demonstrate that the displacement attributed to the pipe dominates the near field motion while that due to the disk is representative of the intermediate and far fields the trigger itself has a smaller contribution mainly limited to the field in the proximity of the source the characteristics displayed by the free surface response evolve from a strong impulsive signature in the immediate vicinity of the epicenter to a well developed harmonic wave train dominated by rayleigh waves at larger distances no clear shear arrival can be detected in the synthetic seismograms the displacement spectrum reflects the organ pipe modes of the conduit and the bandwidth associated with the dominant spectral peak of motion is controlled by the combined losses due to viscous attenuation in the fluid and elastic radiation into the solid in the case of the cylindrical magma column considered the radiation loss is proportional to the square of the pipe radius while the loss related to viscous damping is inversely proportional to the same factor indicating that the relative importance of the two loss mechanisms is critically dependent on the geometry of the magma reservoir the relative importance of the pipe and disk elements likewise is a function of the conduit cross section this suggests the possibility of determining the geometry of the source as well as the radiation loss and in situ magma viscosity from a comparison of near and far field observations

large extensional aftershocks in the continental forearc triggered by the 2010 maule earthquake chile summary the mw 8 8 maule earthquake occurred off the coast of central chile on 2010 february 27 and was the sixth largest earthquake to be recorded instrumentally this subduction zone event was followed by thousands of aftershocks both near the plate interface and in the overriding continental crust here we report on a pair of large shallow crustal earthquakes that occurred on 2010 march 11 within 15 min of each other near the town of pichilemu on the coast of the o higgins region of chile field and aerial reconnaissance following the events revealed no distinct surface rupture we infer from geodetic data spanning both events that the ruptures occurred on synthetic sw dipping normal faults the first larger rupture was followed by buried slip on a steeper fault in the hangingwall the fault locations and geometry of the two events are additionally constrained by locations of aftershock seismicity based on the international maule aftershock data set the maximum slip on the main fault is about 3 m and consistent with field results the onshore slip is close to zero near the surface satellite radar data also reveal that significant aseismic afterslip occurred following the two earthquakes coulomb stress modelling indicates that the faults were positively stressed by up to 40 bars as a result of slip on the subduction interface in the preceding megathrust event in other words the pichilemu earthquakes should be considered aftershocks of the maule earthquake the occurrence of these extensional events suggests that regional interseismic compressive stresses are small several recent large shallow crustal earthquakes in the overriding plate following the 2011 mw 9 0 tohoku oki earthquake in japan may be an analogue for the triggering process at pichilemu

inverting the source mechanism of strombolian explosions at mt yasur vanuatu using a multi parameter dataset abstract the source mechanism of strombolian explosions at mt yasur vanuatu is analyzed using a unique data set which enables us to combine different methodologies the novelty of the approach presented here lies in the combination of seismic acoustic and doppler radar data thus using infrasound and doppler radar observations we are able to provide independent estimates of the volume of the eruptive source in the following we show that a correlation exists between source volume and the maximum particle velocity of the expelled volcanic products in order to determine the source location and the associated mechanism and to compare those two methods we use time reversal imaging and moment tensor inversion while the first method also applies to extended sources the latter might be biased by its intrinsic point source approximation we show that time reversal imaging can deliver an estimate of the source depth without any a priori assumptions even in an unfavorable scenario in terms of topography and receiver setup the inverted source mechanism retrieved from moment tensor inversion is found to be largely isotropic with minor deviatoric components the inverted source location points towards an area to the north west of the active craters indicative of a common feeder system of the activity at mt yasur however it is also evident that to fully locate the source of strombolian activity at yasur location precision must be enhanced

slip distribution of the 1985 central chile earthquake abstract geodetic elevation changes record the deformation associated with the m s 7 8 march 3 1985 central chile earthquake by summing elemental point sources in a half space and employing a gradient technique with positivity constraints we resolve the slip distribution on the dislocation surface most of the fault slip is concentrated on two patches at a depth between 30 and 40 km on a plane dipping 18 e the patch containing the maximum slip is oriented parallel to the coast and is closely located to the reported hypocenter of the mainshock the overall region of maximum slip slip 2 m is more than 140 km long and oriented n s the dislocation model obtained from the static field is in remarkable agreement with the mainshock location and aftershock distribution moment release pattern from analysis of body and surface waves and location and fault geometry of the main aftershock the total moment derived from the dislocation model for the coseismic period is 1 6 10 28 dyn cm comparison of coastal uplift predicted by the model and observations associated with the previous large event in the region august 1906 m t 8 4 suggests a possible variable rupture mode of the region estimations of the future crustal readjustment due to restressing and viscoelastic relaxation indicate a general subsidence over a broader area than the coseismically uplifted region however the maximum amplitude of the predicted postseismic elevation change is less than 10 of the maximum coseismic uplift the proximity of the two patches of maximum slip to the aftershock areas of intermediate size thrust earthquakes in the region since 1971 suggests that these compressional events may represent slip prior to failure in the weaker updip region of the main asperities

the fault nature of the ms 5 4 volcanic earthquake preceding the 1996 subglacial eruption of grimsvotn volcano iceland abstract the seismic activity preceding and accompanying the september 30 1996 subglacial eruption of the grimsvotn volcano iceland developed in three stages 1 the first stage first 19 h included the main shock of magnitude m s 5 4 and its aftershocks along the northern slope of the bardarbunga volcano situated about 20 km nw from grimsvotn 2 seismic foci during the next 17 h marked a line connecting two volcanoes bardarbunga and grimsvotn this stage culminated in the opening of a fissure and the beginning of eruption 3 the third stage was observed during the eruption midnight of september 30 october 7 and included continuous seismic activity along the northern slope of the bardarbunga volcano as well as more western distributed epicenters which together had clustered the ring fault epicentral zone a finite fault broadband teleseismic p waveform inversion was applied to the main shock of september 29 the inversion showed that the rupture had developed downdip from the hypocenter in about 3 s and the main asperity was ruptured at depths between 4 and 6 km a comparison with the deep distribution of aftershocks showed that their hypocenters were situated above the destroyed asperities at the depths between 0 and 4 km these space time seismic patterns and the results of the finite fault inversion may be interpreted in the following way there was a magma chamber under bardarbunga volcano covered by the strong rocks or asperities the main shock of september 29 broke the asperity and formed a path for magma transport then a fissure was formed connecting the opened magma chamber with the feeding structures of grimsvotn volcano and magma was injected laterally to the site of eruption the continuous seismic activity during the third period was related to the collapse of rocks around the released parts of the magma chamber the role of the m s 5 4 earthquake in this sequence was decisive

three dimensional density model of the nazca plate and the andean continental margin 1 we forward modeled the bouguer anomaly in a region encompassing the pacific ocean 85 w and the andean margin 60 w between northern peru 5 s and patagonia 45 s the three dimensional density model that reproduces the gravity field is a continental scale representation of density structure to 410 km depth that characterizes the mantle and crust of the oceanic nazca plate subducted slab and continental margin with a minimum number of bodies we predefined the density of each body after studying the dependency of density on composition of crustal and mantle materials and pressure temperature conditions appropriate for the andean setting a database of independent geophysical information constrains the geometry of the top of the subducted slab locally the moho of the oceanic and continental crusts and indirectly the lithosphere asthenosphere boundary underneath the continental plate other boundaries notably the intracrustal density discontinuity separating upper from lower crust below the continent were not constrained and their geometry is the result of fitting the observed and calculated bouguer anomaly during forward modeling this contribution presents the model to the andean geoscientific community and contains some tools like a sensitivity analysis that helps potential users of the model to interpret its results we describe and discuss some of these results in order to illustrate the application of the model to the study of a wide range of phenomena e g modification of oceanic plate structure by hot spots shape of the subducted slab thermal structure of the continental lithosphere compensation mechanism and formation of orogenic relieve causes of andean segmentation

normal and reverse faulting driven by the subduction zone earthquake cycle in the northern chilean fore arc 1 despite its location in a convergent tectonic setting the coastal cordillera of northern chile between 21 s and 25 s is dominated by structures demonstrating extension in the direction of plate convergence in some locations however normal faults have been reactivated as reverse faults complicating the interpretation of long term strain in order to place these new observations in a tectonic context we model stress changes induced on these faults by the subduction earthquake cycle our simulations predict that interseismic locking on the plate boundary encourages normal slip on fore arc faults which may result from elastic rebound due to interplate earthquakes or from seismic or aseismic motion that takes place within the interseismic period conversely stress generated by strong subduction zone earthquakes such as the 1995 mw 8 1 antofagasta event provides a mechanism for the reverse reactivation we document here upper plate fault slip in response to the low magnitude stress changes induced by the subduction earthquake cycle suggests that the absolute level of stress on these faults is very low furthermore seismic hazard analysis for northern chile requires consideration of not only the plate boundary earthquake cycle but also the cycle on fore arc faults that may or may not coincide with the interplate pattern though the relationships between permanent strain and deformation calculated using elastic models remain unclear the compatibility of modeled stress fields with the distribution of fore arc faulting suggests that interseismic strain accumulation and coseismic deformation on the subduction megathrust both play significant roles in shaping structural behavior in the upper plate

estimation of arrival times from seismic waves a manifold based approach summary we propose a new method to analyse seismic time series and estimate the arrival times of seismic waves our approach combines two ingredients the time series are first lifted into a highdimensional space using time delay embedding the resulting phase space is then parametrized using a non linear method based on the eigenvectors of the graph laplacian we validate our approach using a data set of seismic events that occurred in idaho montana wyoming and utah between 2005 and 2006 our approach outperforms methods based on singular spectrum analysis wavelet analysis and short term average long term average sta lta

compressional and transpressional stress pattern for pliocene and quaternary brittle deformation in fore arc and intra arc zones andes of central and southern chile kinematic analysis of fault slip data for stress determination was carried out on late miocene to quaternary rocks from the fore arc and intra arc regions of the chilean andes between 33 and 46 south latitudes studies of neogene and quaternary infilling the central depression as well as plutonic rocks of the north patagonian batholith along the liquine ofqui fault zone have revealed various compressional and or transpressional states of stress in the pliocene the maximum compressional stress 1 was generally oriented east west during the quaternary the deformation was partitioned into two coeval distinctive states of stress in the fore arc zone the state of stress was compressional with 1 oriented in a n s to nne ssw direction in the intra arc zone the state of stress was transpressional with 1 striking ne sw along the coast in one site 37 30 s the quaternary strain deformation is extensional with an e w direction which can be explained by a co seismic crustal bending readjustment

spectral analysis of harmonic tremor signals at mt semeru volcano indonesia a detailed spectral analysis of tremor signals recorded at mt semeru volcano indonesia in october 1992 by the german indonesian volcano expedition give 92 reveals clearly harmonic spectra containing up to 11 integer harmonics the spectral features can be explained by any rhythmically pulsating source producing a temporarily stable source signal as one realisation of this concept we model the source as a resonating gas volume generating seismic signals similar to the sound generated in a recorder

pressure changes associated with the ascent and bursting of gas slugs in liquid filled vertical and inclined conduits at basaltic volcanoes the sources of long period and very long period seismicity and acoustic signals are frequently described in terms of fluid dynamic processes in particular the formation and ascent of gas slugs within the magma column and their bursting at the surface to investigate pressure changes associated with these processes two phase flow experiments have been carried out in vertical and inclined pipes with both single gas slugs and a continuously supplied gas phase the ascent of individual gas slugs is accompanied by strong dynamic pressure variations resulting from the flow of liquid around the slug these dynamic transients generate sub static pressures below the ascending slug in viscosity controlled systems and produce super static pressures when the slug reaches the surface and motion ceases in inertia dominated systems conduit inclination promotes a change of regime from bubbly to slug flow and favours an increase in size and velocity of the slugs at the expense of their frequency of occurrence during continuously supplied two phase flow the experimental pressure data support previous theoretical analyses of oscillatory sources in ascending slugs as the slugs approach the surface and burst pressure oscillations are also observed during the release of gas slugs and in their wake region

deep water deposits of the tanqua and laingsburg subbasins southwest karoo basin south africa analog for the gulf of mexico abstract the tanqua and laingsburg subbasins in south africa had near contemporaneous formation and filling and contain permian age basin floor and slope fans that display characteristics similar to deposits in the northern gulf of mexico outcrop area for each subbasin is about 650 km2 and individual fans range from 150 to 450 km2 with lateral continuity of individual fans up to 34 km with a sandstone shale ratio of 75 90 the arenaceous fans vary in thickness from 20 to 60 m with interlying shales ranging from 20 to 75m in thickness both subbasins were influenced in their formation and in the architecture of their deposits by structures and events associated with the cape fold belt having undergone little tectonic tilting the highly continuous outcrops in the tanqua subbasin expose two fans continuing from mid fan channel complexes with associated levee overbank deposits to sheet like outer fan lobes while three other fans expose outer fan depositional lobes paleocurrent directions for four of the fans are from ssw to s and a direction of w to wnw for the fifth these fans most likely had a single point source which migrated over the time of basin fill unrestricted deposition suggests an open basin depositional setting the laingsburg subbasin was strongly influenced by the tectonism associated with the cape fold belt deposition occurred in a deeper and narrower basin and the deposits except for the overlying deltaics cannot be correlated with those of the tanqua subbasin the two subbasins while associated with an active margin were likely filled at slightly different times both had a distant source area which led to deposits exhibiting characteristics of a passive margin depositional environment understanding the evolution of the subbasins and the tectonic conditions under which the submarine fans were deposited leads to the determination of the mechanisms that influenced the formation of the fans and their resulting architecture these fans permit detailed studies on their architecture necessary to 1 increase our understanding of fine grained low sandstone shale ratio fans 2 determine influences of paleostructures and tectonics on basin fill 3 carry out detailed reservoir simulation programs and 4 make predictive models of deep water sands in the northern gulf of mexico end of record last page 646

land level changes produced by the mw 8 8 2010 chilean earthquake we observed vertically displaced coastal and river markers after the 27 february 2010 chilean earthquake moment magnitude mw 8 8 land level changes range between 2 5 and 1 meters evident along an approximately 500 kilometers long segment identified here as the maximum length of coseismic rupture a hinge line located 120 kilometers from the trench separates uplifted areas to the west from subsided regions a simple elastic dislocation model fits these observations well model parameters give a similar seismic moment to seismological estimates and suggest that most of the plate convergence since the 1835 great earthquake was elastically stored and then released during this event

facies and cycle architecture of a pleistocene marine terrace crotone southern italy a sedimentary response to late quaternary high frequency glacio eustatic changes abstract cyclic late pleistocene shallow marine deposits such as those forming the sedimentary cover of some marine terraces allow a detailed study of the architecture of nearshore to offshore cycles deposited under the influence of high amplitude glacio eustatic changes the capo colonna marine terrace located near crotone southern italy is composed of two cycles recording a low frequency retrogradational trend which is thought to be the result of a generalized base level rise during a late pleistocene interglacial stage superimposed on regional uplift cycles of the capo colonna marine terrace are composed of coarse grained lags siliciclastic shoreface deposits and mostly carbonate shelf deposits and their general stratigraphic architecture evidences relatively thin transgressive and thick regressive intervals the latter can be top truncated due to wave ravinement during a subsequent erosional transgression the architectural style of the capo colonna marine terrace cycles is thought to be linked to very rapid base level rises related to the late pleistocene high amplitude glacio eustatic changes climatic variations controlling the sediment supply rate are considered less effective in the present context present results allow a comparison with other cyclic successions developed under icehouse climatic regimes showing a discrete variability in their stratal architecture

array measurements and modeling of sources of shallow volcanic tremor at kilauea volcano hawaii we show that resonances in near surface layers path effects or a combination of near surface resonances and source resonances source effects could be responsible for the sharp spectral peaks found in the records of gas piston activity and volcanic tremor recorded near puu oo crater on kilauea volcano hawaii two types of sources are found to be compatible with observations and can not be distinguished using our data in one model impulsive explosion point sources are embedded in the puu oo structure in the other model impulsive point sources of pressure excite the resonances of a fluid filled crack embedded in that structure both models require shallow sources z 100 m and display a strong dependence of the radiated spectrum on source depth over a depth range comparable to the overall thickness of the surficial layers based on these results it may be possible to track changes in source depth through temporal changes in observed spectra a potentially useful tool for monitoring volcanic activity at this site we estimate the depth and spatial extent of volcanic tremor and gas piston activity using two dense arrays with respective apertures of 800 and 120 m located near puu oo measurements of slowness ray parameter and azimuth as a function of time clearly indicate that the sources of volcanic tremor and gas piston activity are located beneath or in close proximity to the puu oo crater at depths shallower than approximately 1 km based on slowness and particle motion analyses we find that the records of volcanic tremor and gas piston events at puu oo consist of a complex combination of body and surface waves