accelerating seismic crustal deformation in the north aegean trough greece summary a recently developed algorithm has been applied to define regions of the northern aegean in which accelerating seismic crustal deformation is currently occurring an elliptical such region has been found in the western part of the north aegean accelerating deformation which started three decades ago and has been released by the generation of intermediate magnitude earthquakes m 4 5 is still occurring based on these observations we can assume that this region is now in a state pre shock deformation that will lead to a critical point main shock the estimated basic parameters of this impending main shock are 39 7 n 23 7 e for the epicentre m 6 0 for the moment magnitude and tc 2001 1 for the origin time the corresponding uncertainties are less than 100 km for the epicentre 0 4 for the magnitude and 1 5 yr for the origin time

evaluation of the results for an intermediate term prediction of the 8 january 2006 mw 6 9 cythera earthquake in the southwestern aegean during the past few decades the critical earthquake model which is based on observations concerning accelerating seismic deformation and concepts of the critical point dynamics has been proposed by various seismologists as a useful tool for intermediate term earthquake prediction a refined approach of this model has been previously applied to search for preshock critical regions in the southern aegean using all available data until the middle of 2002 a critical region corre sponding to a large mainshock had been identified papazachos et al 2002a b in the southwestern part of the aegean near the cythera island the predicted in 2002 parameters for this ensuing earthquake are u 36 5 n k 22 7 e for the epicental geographic coordinates with a model uncertainty of 120 km focal depth 100 km moment magnitude m 6 9 0 5 and origin time tc 2006 4 2 0 the generation of the strong cythera earthquake on 8 january 2006 with m 6 9 epicenter coordinates u 36 2 n and k 23 4 e and a focal depth of h 65 km satisfies this intermediate term prediction the region where significant macroseismic effects were anticipated from the predicted mainshock cythera south peloponnesus west crete and west cyclades corresponds to the area where damage by the 8 january 2006 strong earthquake has been observed the verification of this prediction is strong evidence that the intermediate term prediction of strong earthquakes is potentially feasible but additional forward testing of the model is needed to validate this result

broadband seismic experiment at merapi volcano java indonesia very long period pulses embedded in multiphase earthquakes abstract multiphase mp and low frequency lf earthquakes with spectral peak amplitudes at 3 4 and 1 hz respectively are two common types of shallow volcanic earthquakes previously recognized at merapi volcano their mechanisms are poorly understood but mps have been temporally associated with lava dome growth we conducted a seismic experiment in january february 1998 using four broadband seismographs to investigate the nature of seismic activity associated with dome growth during our experiment merapi experienced mild dome growth with low level seismic activity we compare our data to that recorded on a local short period sp network with the following preliminary results mp and lf events as recorded and classified on the short period network instruments were recognized on the broadband network frequency spectrograms revealed similar patterns in the near summit region at widely separated broadband stations higher frequency spectra than previously recognized were identified for both mp and lf events and were strongly attenuated as a function of radial distance from the source thus the spectral characteristics of these events as recorded on far field stations are not fully indicative of the source processes in particular many events classified as lf type appear to have much high frequency energy near the source this aspect of these so called lf earthquakes and their association with very long period vlp pulses suggests that many events identified in the far field as lf events are in actuality a variety of the mp event and involve similar source processes broadband records indicated that simple large amplitude vlp pulses were embedded in mp and lf wavetrains from event to event these pulses were similar in their waveforms and had periods of 4 s vlp events embedded in lf and mp earthquakes were located using particle motions the epicenters were clustered in a central region of the dome complex and preliminary source depths were within about 100 m of the dome surface suggesting a source region deep within the dome or the uppermost conduit a similar source location was established by study of mp high frequency onsets our broadband data suggests that we have recorded both elastic seismic waves and a simple embedded pulse that is interpreted to represent a surface tilt at the seismometer site the inferred tilt indicates an inflation and subsequent deflation possibly caused by a gas pressure pulse or episodic shallow magma transport with stick slip movement of the conduit wall

seismicity of the aegean and surrounding area abstract seismicity parameters based on instrumental and historical data are given for 36 seismic sources of shallow earthquakes and for 6 seismic sources of intermediate depth earthquakes in the aegean and surrounding area 34 n 43 n 18 e 30 e these parameters are of two categories parameters of the first category are useful for seismic hazard evaluation a and b values of the frequency magnitude relation maximum earthquake magnitude number of shocks larger than certain magnitude per year while parameters of the second category are proper for describing the spatial distribution of seismicity mean return period most probable magnitude in a certain time period moment rate shallow seismicity is highest along the convex side of the hellenic arc but close to the coast ionian islands south peloponnesus south of crete south of karpathos and rhodos in central greece patraikos corinthiakos evoikos gulfs thessalia and along a seismic belt which includes the northwestern anatolia fault zone the northernmost part of the aegean sea and the serbomacedonia zone the intermediate depth seismic activity is distributed in two parts of the benioff zone which dips from the convex side eastern mediterranean to the concave side aegean sea of the hellenic arc the one part shows a low dip angle and includes earthquakes with focal depths between 70 km and 100 km this part has a high seismicity earthquake magnitudes up to 8 0 and is situated below the inner slope of the sedimentary part of the hellenic arc eastern peloponnesus north of crete rhodos based on the fact that this part of the benioff zone is a continuation of the seismic zone of shallow earthquakes along the hellenic arc and that both zones have the same seismicity it is concluded that they constitute a continuous seismic belt on which coupling occurs between the subducted eastern mediterranean lithosphere and the overthrusted aegean lithosphere the other inner part of the benioff zone shows low seismicity maximum earthquake magnitude up to 7 1 with earthquakes of focal depths between 100 km and 180 km it dips at a mean angle of 38 below the volcanic arc of the southern aegean sea and is the result of the subduction of the front part of the eastern mediterranean lithosphere without coupling with the aegean lithosphere

magmatic processes revealed by textural and compositional trends in merapi dome lavas syn eruptive degassing of volcanoes may lead to syn eruptive crystallization of groundmass phases we have investigated this process using textural and compositional analysis of dome material from merapi volcano central java indonesia samples included dome lavas from the 1986 88 1992 93 1994 and 1995 effusive periods as well as pyroclastic material deposited by the november 1994 dome collapse with total crystallinities commonly in excess of 70 phenocrysts 1 microlites the liquids present in merapi andesites are highly evolved rhyolitic at the time of eruption feldspar microlites in dome rocks consist of plagioclase cores ab63an29or8 surrounded by alkali feldspar rims ab53an5or42 compositional pairs which are not in equilibrium a change in the phase relations of the ternary feldspar system caused by degassing best explains the observed transition in feldspar composition a small proportion of highly vesicular airfall tephra grains from the 1994 collapse have less evolved glass compositions than typical dome material and contain rimless plagioclase microlites suggesting that the 1994 collapse event incorporated less degassed partially liquid magma in addition to fully solidified dome rock as decompression drives volatile exsolution rates of degassing and resultant microlite crystallization may be governed by magma ascent rate microlite crystallinity is nearly identical among the 1995 dome samples an indication that similar microlite growth conditions ph2 o and temperature were achieved throughout this extrusive period however microlite number density varied by more than a factor of four in these samples and generally increased with distance from the vent low vent ward microlite number densities and greater microlite concentrations down flow probably reflect progressively decreasing rates of undercooling at the time of crystal nucleation during extrusion of the 1995 dome comparison between dome extrusion episodes indicates a correlation between lava effusion rate and microlite number density suggesting that extrusion slowed during 1995 crystal textures and compositions in the 1992 93 and 1994 domes share the range exhibited by the 1995 dome suggesting that transitions in crystallization conditions i e rates of undercooling determined by effusion rate are cyclic q 2000 elsevier science b v all rights reserved

accelerating seismic crustal deformation before the izmit nw turkey large mainshock of 1999 august 17 and the evolution of its aftershock sequence summary the large izmit nw turkey mainshock 1999 august 17 mw 7 6 followed by another large earthquake on 1999 november 12 mw 7 2 caused extensive damage and loss of life in a zone approximately 170 km long along the coastal area of the gulf of izmit and further east to adapazari and duzce on the basis of the critical earthquake concept and by applying a recently developed optimization algorithm an elliptical area surrounding the 1999 august 17 mainshock epicentre was identified in which accelerating moderate magnitude seismic activity started in 1981 and culminated in the generation of the mainshock on the other hand the space and time distribution of the aftershocks of the first mainshock 1999 august 17 and the time variations of the b value of the gutenberg richter recurrence law and the mean aftershock magnitude suggest that the second mainshock 1999 november 12 might have been anticipated

variation of seismic coupling with slab detachment and upper plate structure along the western hellenic subduction zone abstract the western hellenic subduction zone is characterized by a trenchward velocity of the upper plate in the ionian islands segment complete seismic coupling is achieved as is predicted by standard plate tectonic models in which there is no slab pull force because the slab has broken off the moderate local seismic moment rate relates to a shallow downdip limit for the seismogenic interface this characteristic may be attributed to the ductility of the lower crust of the upper plate which allows a decollement between the upper crust of the overriding plate and the subducting plate farther south a deeper downdip limit of the seismogenic interface is indicated by thrust faulting earthquakes which persist much deeper in western crete a correspondingly larger downdip width of this seismogenic zone is consistent with the suggested larger maximum magnitude of earthquakes here however since the seismic moment release rate seems to be moderate in the peloponnese and western crete like in in the ionian islands this seismically active interface cannot maintain complete seismic coupling across its larger downdip width a cause may be the lateral addition of overweight to the part of the slab still attached in crete by the free fall of its part that has broken off from the surface further north this increased slab pull reduces the compressive normal stress across the seismogenic interface and thus causes partial seismic coupling in its shallower part however the width of this part may provide an additional area contributing to slip in large earthquakes which may nucleate deeper on stick slip parts of the interface hints at anomalies in structure and seismicity which need to be resolved may relate to the present location of the edge of the tear in the slab

accelerated preshock deformation of broad regions in the aegean area twenty four regions where accelerating deformation has been observed for a few decades before corresponding strong m 6 0 7 5 mainshocks are identified in the broader aegean area to a first approximation these preshock regions have elliptical shapes and the radius r in km of a circle with an area equal to the corresponding ellipse is related to the moment magnitude m of the mainshock by the equation log r 0 42 m 0 68 the dimension of each preshock region is about seven to ten times larger than the rupture zone fault length of the corresponding mainshock the time variation of the cumulative benioff strain was satisfactorily fitted by a power law relation which is predicted by statistical physics if the mainshock to which accelerating strain rates leads is considered as a critical point the duration t in years of the accelerating benioff strain release period is given by the relation log t 5 94 0 75 log s r where s r is the mean benioff strain rate release per year for 104 km2 in the preshock region calculated by the complete available data m 5 2 for the entire instrumental period 1911 1998 the importance of identifying and investigating such regions for better understanding the dynamics of the active part of the lithosphere as well as for earthquake prediction and time dependent seismic hazard assessment is discussed

retrospective on the accelerating seismic release asr hypothesis controversy and new horizons abstract the hypothesis that large earthquakes may be preceded by a period of accelerating seismicity or accelerating seismic release asr was proposed about twenty years ago a compilation of almost one hundred peer reviewed publications on this topic since the late 1980s to the present day shows that the rate of asr studies increased gradually until 2004 but decreased afterwards this negative trend is amplified by a recent increase in the number of negative results and criticisms of the asr hypothesis the author suggests that much of the recent negativity regarding this topic is due to the formulation of this hypothesis as a power law fit to cumulative seismicity series this approach is intrinsically linked to the consensus for criticality evident from an overview of the asr literature to explain the emergence of power laws in earthquake populations the holistic view of the earth s crust as a complex system restricts seismicity pattern analyses to the study of main features such as power laws while a reductionist view would allow for more refined ones such a paradigm shift or sea change might be under way in the asr literature where in 2007 a new approach was proposed to explain the asr power law from combined concepts of elastic rebound and geometry reductionism versus holism is a fundamental problem that not only applies to the study of asr but also to the broader field of earthquake physics and earthquake predictability science

seismic activity on neighbouring faults as a long term precursor to large earthquakes in the san francisco bay area activity in moderate size earthquakes accelerated in the several decades before the large california earthquakes of 1989 1906 and 1868 this type of precursor seems to require the presence of several major faults in close enough proximity to one another that moderate size shocks are selectively triggered on surrounding faults during the latter stages of the cycle of strain buildup to large earthquakes it may be possible to use quantitative aspects of similar seismic precursors to make predictions of large earthquakes on timescales of a few years to one decade

accelerating seismic crustal deformation in the southern aegean area a region of intense accelerating seismic crustal deformation has been identified in the southwestern part of the hellenic arc broader area of cythera island the identification is performed using a detailed parametric grid search of the broader southern aegean area for accelerating energy release behavior the identified region has similar properties with past preshock critical regions which have been identified for strong mainshocks in the aegean area based on such observations which suggest that this region is at a critical state that can lead to a critical point that is to the generation of a mainshock an estimation is made of the possible epicenter coordinates magnitude and origin time of this oncoming large m 7 0 earthquake the estimation procedure is validated on the basis of retrospective analysis of strong events in the aegean area as well as by appropriate application on synthetic random catalogs these results the existence of similar observations of accelerating seismic deformation in eastern part of southern aegean and independent information on the time distribution of large earthquakes m 6 8 for the whole southern aegean indicate that the generation of strong earthquakes in this area in the next few years must be considered as very probable

a forward test of the decelerating accelerating seismic strain model to western south and central america abstract global observations show that strong mainshocks are preceded by decelerating preshocks which occur in the focal seismogenic region of the ensuing mainshock and by accelerating preshocks which occur in a broader critical region of the mainshock predictive properties of these preshocks have been expressed by empirical relations supported by theory and form the decelerating accelerating seismic strain d as model a respective algorithm has been developed which is used to identify the critical and seismogenic region and estimate predict the corresponding ensuing mainshock in the present work a forward test of this model is performed by attempting intermediate term prediction of future big m 7 7 mainshocks along the western coast of south and central america three regions of decelerating shocks and three corresponding regions of accelerating shocks have been identified the parameters origin time magnitude epicenter coordinates as well as their uncertainties have been estimated predicted for the corresponding probably ensuing three mainshocks this forward test allows an objective evaluation of the model s ability for an intermediate term prediction of strong shallow mainshocks

increased long range intermediate magnitude earthquake activity prior to strong earthquakes in california we study the space time relationships between strong earthquakes in california and the intermediate magnitude earthquakes that both precede and follow them all 11 earthquakes in california with nominal magnitudes greater than or equal to 6 8 from 1941 to 1993 were preceded by an increase in the rate of occurrence of earthquakes having magnitudes greater than 5 1 ten of the 11 earthquakes occurred when or shortly after the intermediate magnitude activity was greater than its 75th percentile three of these strong earthquakes are in a conventional space time foreshock aftershock relationship with others of the 11 strong events the precursory activity is concentrated in regions having linear dimensions of the order of a few hundred kilometers these dimensions are significantly larger than the estimated fracture lengths of the ensuing strong earthquakes the correlations are ill defined for smaller earthquakes and are almost unidentifiable for earthquakes with magnitudes less than about 4 6 the precursors to the strong earthquakes appear over a time interval of the order of 5 to 10 years before the strong earthquake although the onset was about 25 years before the san francisco earthquake in the case of the loma prieta and san francisco earthquakes the onset of increased activity appears to be relatively abrupt the increased activity is either switched off abruptly to distances of the order of hundreds of kilometers shortly after the occurrence of a strong earthquake or the strong events are themselves part of a precursory pattern of continuing high activity before a second strong earthquake that takes place soon thereafter with subsequent extinction of activity after it thus the intermediate magnitude precursors do not directly influence the time and location of the subsequent strong event but the strong event has a strong influence on the stress field in the vicinity of intermediate magnitude earthquakes to distances of the order of many times the scale size of the strong earthquake

time variation of parameters related to the accelerating preshock crustal deformation in the aegean area the time variation of two parameters related to accelerating seismic deformation before strong earthquakes in the aegean area is examined the first is the b parameter of the gutenberg richter relation and the second is the curvature parameter c which is a measure of deviation of the accelerating preshock deformation from a linear time variation of this deformation following two different procedures it was found that the b value exhibits a decreasing trend prior to the oncoming earthquake in agreement with the results of laboratory experiments and other independent observations c values also show a decreasing trend before main shocks these results indicate that such time variations of these parameters can be considered as precursory phenomena of ensuing strong earthquakes

an observational test of the origin of accelerating moment release before large earthquakes 1 a progressive increase of seismic activity distributed over a wide region around a future earthquake epicenter is termed accelerating moment release amr this phenomenon has been observed in several studies over the last 15 years although there is no consensus about the physical origin of the effect in a recent hypothesis known as the stress accumulation sa model the amr is thought to result from the last stage of loading in the earthquake cycle in this view the increasing seismicity is due to minor stress release as the whole region becomes sufficiently stressed for the major event to occur the stress accumulation model makes specific predictions about the distribution of events in an amr sequence because the amr is predicted to be a result of loading on the main fault the precursory activity should be concentrated in the positive lobes of the far field stresses calculated by a backslip dislocation model of the main shock to test this model amr is first found in optimal circular regions around the epicenters of each of the m w 6 5 earthquakes in central and southern california since 1950 a backslip dislocation model is then used to determine which of the precursory events occur in the regions predicted by stress accumulation amr is shown to occur preferentially in the lobes of the backslip stress field predicted by the stress accumulation model

probabilities of activation of seismic faults in critical regions of the aegean area summary properties of the accelerating seismic crustal deformation pattern and of the intermediateterm seismic quiescence pattern have been combined to identify faults in the aegean area 34 n 43 n 19 e 30 e that have a considerable probability of generating strong earthquakes m 6 4 during the next 5 yr period eight groups of such faults have been identified and the probability of each fault being activated during this time period has been estimated three of these groups are located in southern greece hellenic arc two in central greece east central greece ionian islands two in northwestern turkey and one in the area of the borders of albania greece and the former yugoslav republic of macedonia the importance of these results for intermediate term seismic hazard assessment is discussed

deformation and seismic precursors to dome collapse and fountain collapse nuees ardentes at merapi volcano java indonesia 1994 1998 abstract following the eruption of january 1992 episodes of lava dome growth accompanied by generation of dome collapse nuees ardentes occurred in 1994 1998 in addition nuees ardentes were generated by fountain collapse in january 1997 and the 1998 events also suggest an explosive component significant tilt and seismic precursors on varying time scales preceded these events deformation about the summit has been detected by electronic tiltmeters since november 1992 with inflation corresponding generally to lava dome growth and deflation or decreased inflation corresponding to loss of dome mass strong short term days to weeks accelerations in tilt rate and seismicity occurred prior to the major nuees ardentes episodes apart from those of 22 november 1994 which were preceded by steadily increasing tilt for over 200 days but lacked short term precursors because of the combination of populated hazardous areas and the lack of an issued warning about 100 casualties occurred in 1994 in contrast the strong precursors in 1997 and 1998 provided advance warning to observatory scientists enabled the stepped raising of alert levels and aided hazard management as a result of these factors but also the fortunate fact that the large nuees ardentes did not quite descend into populated areas no casualties occurred the nuee ardente episode of 1994 is interpreted as purely due to gravitational collapse whereas those of 1997 and 1998 were influenced by gas pressurization of the lava dome

collection and three dimensional modeling of gps and tilt data at merapi volcano java we study here the deformations associated with the november 1996 to march 1997 eruption period at mount merapi central java one of the most active volcanoes in indonesia this activity period includes a vertical explosion on january 17 and an increase of the lava dome volume by about 3 106 m3 two global positioning system gps campaigns have been carried out on a six benchmark network at the beginning and at the end of the period relative displacements with respect to the reference point show an average subsidence of 6 5 cm a multicomponent tilt station installed on the southeast flank 3 km from the summit recorded a tilt of 11 1 0 7 rad in the tangential direction and 0 9 0 4 rad in the radial direction these data are interpreted using a three dimensional 3 d elastic model based on the mixed boundary element method and a near neighbor monte carlo inversion interpretation of tilt data requires an accurate mesh for discretizing the 3 d topography the final result supports a horizontal elliptic magma source located 8 5 0 4 km below the summit and 2 0 4 km to the east of it in particular the data cannot be consistent with the location of a magma chamber determined from seismic activity analysis i e 2 km below the summit the computed depth depends strongly on the source shape and cannot be constrained properly because of the small amount of data the computed deflation of 11 2 106 m3 is about 3 times larger than the observed increase in the lava dome volume this difference is attributed to rock avalanches and pyroclastic flows on the flanks of the volcano

the 1984 nuee ardente deposits of merapi volcano central java indonesia stratigraphy textural characteristics and transport mechanisms for many centuries merapi volcano has generated hot avalanches of blocks lapilli and ashes derived from the destruction of partially solidified viscous lava domes merapi type nuees ardentes on 15 june 1984 at least four nuees ardentes came down the southwest slope of the merapi the first and the last being responsible for more than 99 of the deposits which are now exposed the first nuee ardente a merapi type nuee ardente was produced by the destruction of the dome travelled 7 km from the crater leaving a measured deposit 2 7 m thick 4 km from the crater near its upper depositional limit regularly increasing to a maximum measured thickness of 12 m at the front of the deposit the lower contact is sharp non erosive with pines still rooted in the underlying paleosol the deposit consists of 50 ash 33 lapilli and 17 blocks with two subpopulations one rosin and one normal and is finespoor with less than 4 of fine ash d finer than 4 the deposit displays reverse population grading of both vesiculated and massive clasts and of the maximum grain size the maximum size significantly increases regularly down current over most of the exposed length of unit 1 and bed thickness increases for the entire length of the deposit the deposit of the second nuee ardente is only 6 21 cm thick and of very limited lateral extent it is a normally graded coarse to fine ash with a finespoor base the third unit consists of fines poor normally graded coarse ash exposed in low amplitude 20 40 cm 12 m wavelength dunes the deposit of the fourth nuee ardente rests in sharp erosive contact on the underlying unit increasing in thickness down flow it consists of transitional coarse and fine grained strata 6 130 c cm thick dipping 5 10 down flow the deposit made up of two subpopulations one rosin and one normal is normally graded over the entire bed but coarsegrained strata are reversely graded the relative content of vesiculated clasts increases up bed in both strata types from 12 at the base to 40 at the top the characteristics of unit 1 suggest that it accumulated from a concentrated suspension of cohesionless solids exhibiting non newtonian behavior where dispersive pressure played an important role in the suspension of the clasts units 2 and 3 were probably deposited from dilute turbulent suspensions whereas the upper unit 4 is a classic example of deposition from a high density turbulent suspension leading to the formation of multiple traction carpets driven by the overlying lower density surge the horizontal distance travelled by a hot rock avalanche may be influenced by its transport mechanism debris flows are mobile on very low slopes as low as 1 whereas grain flows even density modified grain flows require relatively high slopes more than 6 at merapi to maintain their mobility if the present merapi dome were to collapse and produce a debris flow its present volume coupled with the minimal 1 5 km vertical drop could travel a distance ranging between 15 and 30 km however if transport were by grain flow mechanisms the mass could come to rest as it reaches a 5 10 slope

monitoring lava dome growth during the 2004 2008 mount st helens washington eruption using oblique terrestrial photography abstract we present an analysis of lava dome growth during the 2004 2008 eruption of mount st helens using oblique terrestrial images from a network of remotely placed cameras this underutilized monitoring tool augmented more traditional monitoring techniques and was used to provide a robust assessment of the nature pace and state of the eruption and to quantify the kinematics of dome growth eruption monitoring using terrestrial photography began with a single camera deployed at the mouth of the volcano s crater during the first year of activity analysis of those images indicates that the average lineal extrusion rate decayed approximately logarithmically from about 8 m d to about 2 m d 2 m d from november 2004 through december 2005 and suggests that the extrusion rate fluctuated on time scales of days to weeks from may 2006 through september 2007 imagery from multiple cameras deployed around the volcano allowed determination of 3 dimensional motion across the dome complex analysis of the multi camera imagery shows spatially differential but remarkably steady to gradually slowing motion from about 1 2 m d from may through october 2006 to about 0 2 1 0 m d from may through september 2007 in contrast to the fluctuations in lineal extrusion rate documented during the first year of eruption dome motion from may 2006 through september 2007 was monotonic 0 10 m d to gradually slowing on time scales of weeks to months the ability to measure spatial and temporal rates of motion of the effusing lava dome from oblique terrestrial photographs provided a significant and sometimes the sole means of identifying and quantifying dome growth during the eruption and it demonstrates the utility of using frequent long term terrestrial photography to monitor and study volcanic eruptions

nuees ardentes of 22 november 1994 at merapi volcano java indonesia nuees ardentes associated with dome collapse on 22 november 1994 at merapi volcano traveled to the south southwest as far as 6 5 km and collectively accumulated roughly 2 5 3 million cubic meters of deposits the damaged area comprises 9 5 km2 and is covered by two nuee ardente facies a conventional merapi type valley fill block and ash flow facies and a pyroclastic surge facies the proximal deposits reflect the accumulation of dozens of nuees ardentes with many subsidiary flow units the distal deposits are more simply organized as only a few individual events reached to distances 3 5 km the stratigraphic relationships north of turgo hill indicate that the surge deposits are a facies of particularly mobile nuees ardentes that also deposited channeled block and ash flow facies they further suggest that the surge facies beyond the channel margins correlate laterally with a finer grained sublayer locally developed at the base of the block and ash flow facies eyewitness reports suggest that the emplacement of the block and ash flow facies in the distal part of the boyong river may have followed by a short time interval the destruction and deposition of the surge facies at turgo village the stratigraphy is in accord with the eyewitness reports the surge facies was emplaced by a dilute surge current detached from the same dome collapse nuee ardente that as a separate flow unit subsequently emplaced the distal block and ash deposit in the boyong valley the detachment occurred at higher elevations likely at or above the slope break at about 2000 m elevation this flow separation enabled the surge current to shortcut over the landscape and to emplace its deposit even as the block and ash flow continued its tortuous southward movement in the boyong channel dome collapse nuee ardente activity formed the bulk of the eruption which was accompanied by virtually no significant vertical summit explosive activity

evolving towards a critical point a review of accelerating seismic moment energy release prior to large and great earthquakes there is growing evidence that some proportion of large and great earthquakes are preceded by a period of accelerating seismic activity of moderate sized earthquakes these moderate earthquakes occur during the years to decades prior to the occurrence of the large or great event and over a region larger than its rupture zone the size of the region in which these moderate earthquakes occur scales with the size of the ensuing mainshock at least in continental regions a number of numerical simulation studies of faults and fault systems also exhibit similar behavior the combined observational and simulation evidence suggests that the period of increased moment release in moderate earthquakes signals the establishment of long wavelength correlations in the regional stress field the central hypothesis in the critical point model for regional seismicity is that it is only during these time periods that a region of the earth s crust is truly in or near a self organized critical soc state such that small earthquakes are capable of cascading into much larger events the occurrence of a large or great earthquake appears to dissipate a sufficient proportion of the accumulated regional strain to destroy these long wavelength stress correlations and bring the region out of a soc state continued tectonic strain accumulation and stress transfer during smaller earthquakes eventually re establishes the long wavelength stress correlations that allow for the occurrence of larger events these increases in activity occur over longer periods and larger regions than quiescence which is usually observed within the rupture zone of a coming large event the two phenomena appear to have different physical bases and are not incompatible with one another

overview of the 2006 eruption of mt merapi abstract in the last part of the 20th century and the beginning of the 21st century mt merapi in central java indonesia erupted about every 2 5 years most of the eruptions were low in explosivity with vei 3 or less eruptions usually involve the formation of a lava dome either in the beginning or in the end of the eruptive episode for the 2006 eruption the precursory signal was first observed in the middle of the year 2005 with a decrease in edm slope distances to points on the rim an increase of seismicity and a possible increase of so 2 emissions those early events marked the beginning of a more continuous period of inflation which led to the eruption in total the pre eruption displacement of the southern rim reached at least 2 4 m toward the measuring station in kaliurang kal from late april until june 2006 a lava dome grew on the summit with a volume that gradually increased until it reached about 4 1 million m 3 in 38 days the total of erupted magma was about 5 3 million m 3 dense rock equivalent dre the dome subsequently collapsed in three steps from june 4 to june 14 leaving an open scar on its southeast side in this paper we detail the changes of dome morphology that were monitored by taking successive photographs from similar positions the eruption in 2006 marked a significant change in summit morphology from west southwestward opening during the 20th century to the currently southeast orientation also an mw 6 4 earthquake occurred on 26 may midway through the eruption which adds interesting questions about the relationship of the eruption and the earthquake edm data from 2006 and previous eruptions show that the summit remains inflated after each eruption i e no significant deflation occurs following eruptions the lack of post eruption deflation suggests that magma remains in the shallow parts of the edifice after the eruption as a result the complex of summit lava domes and their intrusive roots grow with time and merapi s rim and summit become progressively more unstable and prone to collapse

ground deformation at merapi volcano java indonesia distance changes june 1988 october 1995 abstract edifice deformations are reported here for the period 1988 1995 at merapi volcano one of the most active and dangerous volcanoes in indonesia the study period includes a major resumption in lava effusion in january 1992 and a major dome collapse in november 1994 the data comprise electronic distance measurements edm on a summit trilateration network slope distance changes measured to the upper flanks and other data collected from 1988 to 1995 a major consequence of this study is the documentation of a significant 4 year period of deformation precursory to the 1992 eruption cross crater strain rates accelerated from less than 3 10 6 day between 1988 and 1990 to more than 11 10 6 day just prior to the january 1992 activity representing a general asymmetric extension of the summit during high level conduit pressurization after the vent opened and effusion of lava resumed strain occurred at a much reduced rate of less than 2 10 6 day edm measurements between lower flank benchmarks and the upper edifice indicate displacements as great as 1 m per year over the four years before the 1992 eruption the gendol breach a pronounced depression formed by the juxtaposition of old lava coulees on the southeast flank functioned as a major displacement discontinuity since 1993 movements have generally not exceeded the 95 confidence limits of the summit network exceptions to this include 12 cm outward movement for the northwest crater rim in 1992 1993 probably from loading by newly erupted dome lava and movements as much as 7 cm on the south flank between november 1994 and september 1995 no short term precursors were noted before the november 1994 lava dome collapse but long term adjustments of crater geometry accompanied lava dome growth in 1994 short term 2 cm deflation of the edifice occurred following the november 1994 dome collapse

a proposed method for locating the critical region of a future earthquake using the critical earthquake concept using the critical point concept and extending bowman s idea of critical earthquake we develop an intersecting circle method to locate the critical region a simulation check shows that this method is effective in finding a given critical region we selected several real cases from new zealand and china and used this method to find the critical regions before the occurrence of large earthquakes the result shows that this method is valid for detecting a critical region and the epicenter of mainshock might be in the critical region

sequential dome collapse nuees ardentes analyzed from broadband seismic data merapi volcano indonesia abstract during the sequential dome collapse of merapi volcano on 22 november 1994 a broadband seismic station on the western slope was the only operational seismic equipment that provided continuous on scale recording of the event according to visual and seismic observations the collapse activity lasted about 10 h we divide the activity into two phases i a period with fluctuating but generally increasing seismic activity associated with 24 moderate to large dome collapse nuees ardentes lasting about 40 min and culminating with the largest event at 10 54 all times reported as local time and ii activity from 11 42 until 20 00 described by scattered clusters of individual rockfalls and 20 nuees ardentes the broadband data were evaluated using the assumption that avalanches with the same source areas and descent paths exhibit a linear relation between source volume and recorded seismic amplitude envelope area a result of the analysis is the determination of the volume of selected individual events from the field surveys the total volume of the collapsed dome lava is 2 6 mm3 discounting the volumetric influence of rockfalls the average size of the 44 nuees ardentes is therefore about 60 000 m3 the largest collapse event at 10 54 is estimated to involve 260 000 m3 based on an analysis of the seismicity the remaining 23 phase i events averaged 60 000 m3 with the total volume of all phase i events accounting for 63 of the unstable dome the 20 phase ii events comprised 37 of the total volume and averaged 47 000 m3 the methods described here can be put to practical use in real time monitoring situations broadband data were essential in this study primarily because of the wide dynamic range

historical eruptions of merapi volcano central java indonesia 1768 1998 abstract information on merapi eruptive activity is scattered and much is remotely located a concise and well documented summary of this activity has been long needed to assist researchers and hazard mitigation efforts and the aim of this paper is to synthesize information from the mid 1700s to the present a descriptive chronology is given with an abbreviated chronology in a table that summarizes events by year assigns preliminary volcanic explosivity index vei ratings and hartmann classifications and provides key references the history of volcano monitoring is also outlined the study reveals that a major difference in eruption style exists between the twentieth and nineteenth centuries although the periodicity between larger events seems about the same during the twentieth century activity has comprised mainly the effusive growth of viscous lava domes and lava tongues with occasional gravitational collapses of parts of oversteepened domes to produce the nuees ardentes commonly defined as merapi type in the 1800s however explosive eruptions of relatively large size occurred to vei 4 and some associated fountain collapse nuees ardentes were larger and farther reaching than any produced in the twentieth century these events may also be regarded as typical eruptions for merapi the nineteenth century activity is consistent with the long term pattern of one relatively large event every one or two centuries based on the long term eruptive record deduced by others from volcanic stratigraphy it is uncertain whether or not a recurrence time model continues to apply to merapi but if so merapi could soon be due for another large event and its occurrence with only modest or inadequately appreciated precursors could lead to a disaster unprecedented in merapi s history because the area around the volcano is now much more densely populated

precursory accelerating seismic crustal deformation in the northwestern anatolia fault zone abstract we present the results of a systematic search for the identification of accelerating seismic crustal deformation in the broader northern aegean area and in northwestern turkey we found that accelerating seismic deformation release expressed by the generation of intermediate magnitude earthquakes is currently observed in nw turkey on the basis of the critical earthquake model and by applying certain constraints which hold between the basic quantities involved in this phenomenon it can be expected that this accelerating seismic activity may culminate in the generation of two strong earthquakes in this area during the next few years the estimated epicenter coordinates of the larger of these probably impending earthquakes are 39 7 n 28 8 e its magnitude is 7 0 and its occurrence time tc 2003 5 the second strong event is expected to occur at tc 2002 5 with a magnitude equal to 6 4 and epicenter coordinates 40 0 n 27 4 e the uncertainties in the calculated focal parameters for these expected events are of the order of 100 km for the epicenter 0 5 for their magnitude and 1 5 years for their occurrence time

10 000 years of explosive eruptions of merapi volcano central java archaeological and modern implications abstract stratigraphy and radiocarbon dating of pyroclastic deposits at merapi volcano central java reveals 10 000 years of explosive eruptions highlights include 1 construction of an old merapi stratovolcano to the height of the present cone or slightly higher our oldest age for an explosive eruption is 9630 60 14 c y b p construction of old merapi certainly began earlier 2 collapse s of old merapi that left a somma rim high on its eastern slope and sent one or more debris avalanche s down its southern and western flanks impoundment of kali progo to form an early lake borobudur at 3400 14 c y b p hints at a possible early collapse of merapi the latest somma forming collapse occurred 1900 14 c y b p the current cone new merapi began to grow soon thereafter 3 several large and many small buddhist and hindu temples were constructed in central java between 732 and 900 a d roughly 1400 1000 14 c y b p explosive merapi eruptions occurred before during and after temple construction some temples were destroyed and or buried soon after their construction and we suspect that this destruction contributed to an abrupt shift of power and organized society to east java in 928 a d other temples sites though were occupied by caretakers for several centuries longer 4 a partial collapse of new merapi occurred 14 c y b p eruptions 700 800 14 c y b p 12 14th century a d deposited ash on the floors of still occupied candi sambisari and candi kedulan we speculate but cannot prove that these eruptions were triggered by the same partial collapse of new merapi and that the eruptions in turn ended caretaker occupation at candi sambisari and candi kedulan a new or raised lake borobudur also existed during part or all of the 12 14th centuries probably impounded by deposits from merapi 5 relatively benign lava dome extrusion and dome collapse pyroclastic flows have dominated activity of the 20th century but explosive eruptions much larger than any of this century have occurred many times during merapi s history most recently during the 19th century are the relatively small eruptions of the 20th century a new style of open vent less hazardous activity that will persist for the foreseeable future or alternatively are they merely low level background activity that could be interrupted upon relatively short notice by much larger explosive eruptions the geologic record suggests the latter which would place several hundred thousand people at risk we know of no reliable method to forecast when an explosive eruption will interrupt the present interval of low level activity this conclusion has important implications for hazard evaluation

occurrence of anomalous seismic activity preceding large to great earthquakes in northeast india region with special reference to 6 august 1988 abstract seismicity database from 1860 to 1985 of northeast india region bounded by the area 20 32 n and 82 100 e have been analyzed for the identification of precursory swarm anomalous seismic activity preceding large to great earthquakes with m 7 5 it is observed that with the exception of three earthquakes 1908 1912 and 1918 the large earthquakes of 1897 1946 1947 1950 and 1951 1952 were preceded by well developed epoch of swarm anomalous seismic activity in space and time well before their occurrence the seismicity is observed to fluctuate in the order of low high low ranging from 0 0 5 01 33 to 0 0 7 events year prior to these mainshocks during the epochs of normal background swarm anomalous and gap quiescence respectively the duration of precursory gap is observed to vary from 11 to 17 years for mainshocks of m 7 5 8 0 and from 23 to 27 years for m 8 7 and this period is dependent on the magnitude of the mainshocks using the values of magnitude of mainshock m m average magnitude of swarm m p and the precursory time gap t p the following predictive equations are established for the region m m 1 37 m p 1 40 m m 3 log t p 3 27 all the major earthquakes with m b 6 1 occurred during 1963 1988 have been investigated for their association with anomalous seismicity precursory swarms using the events with cutoff magnitude m b 4 5 eleven such events have occurred in the region during the period except one earthquake of 29 may 1976 all the remaining 10 earthquakes were associated in some forms of anomalous seismicity epochs well defined patterns of anomalous seismicity are observed prior to 1964 1965 12 august 1976 and 30 december 1984 m b 5 6 all these mainshocks are preceded by seismicity patterns in the order of low high low similar to that observed prior to the mainshocks from 1897 to 1962 the anomalous seismicity epoch is delineated with extremely high annual earthquake frequency which was preceded and followed by extremely low seismicity epochs of background and gap quiescence phases consequently seismicity rates during anomalous seismicity epoch have always been above normal 1 event year whereas it is always below normal during the preceding and the following epochs a prediction was made using the 1964 swarm based on the m p and t p values that a large earthquake with m 8 0 5 with focal depth 100 40 km could occur any time from 1986 to 1990 in an area bound by 21 25 5 n latitudes and 93 96 e longitude in arakan yoma fold belt it is interesting to note that the 6 august 1988 earthquake with magnitude 7 5 and focal depth 115 km had occurred within the delineated zone in addition three consecutive swarm activities are identified in a limited area within the eastern syntaxis and these were not followed by any mainshock till date and could be potential zone for future earthquake

currently active regions of decelerating accelerating seismic strain in central asia 1 accelerating preshock seismic strain in a broad critical region and decelerating preshock seismic strain in a narrower seismogenic region constitute a model for intermediate term prediction of strong main shocks an effort is made in the present work for a forward test of the decelerating accelerating seismic strain d as model by identifying such patterns and estimating the corresponding probably ensuing strong main shocks m 7 0 in central asia 20 n 45 n 42 e 105 e five such patterns have been identified and the origin time magnitude and epicentral geographic coordinates of each of the corresponding main shocks have been estimated predicted model uncertainties of the estimated time magnitude and space parameters of these probably ensuing main shocks as well as appropriate statistical tests against a standard gutenberg richter seismicity distribution are also presented to allow a future objective evaluation of the model s efficiency for intermediate term earthquake prediction

structure and co2 budget of merapi volcano during inter eruptive periods soil temperature and gas co2 concentration and flux have been investigated at merapi volcano indonesia during two inter eruptive periods 2002 and 2007 precise imaging of the summit crater and the spatial pattern of diffuse degassing along a gas traverse on the southern slope are interpreted in terms of summit structure and major caldera organization the summit area is characterized by decreasing co2 concentrations with distance from the 1932 crater rim down to atmospheric levels at the base of the terminal cone similar patterns are measured on any transect down the slopes of the cone the spatial distribution of soil gas anomalies suggests that soil degassing is controlled by structures identified as concentric historical caldera rims 1932 1872 and 1768 which have undergone severe hydrothermal self sealing processes that dramatically lower the permeability and porosity of soils temperature and co2 flux measurements in soils near the dome display heterogeneous distributions which are consistent with a fracture network identified by previous geophysical studies these data support the idea that the summit is made of isolated and mobile blocks whose boundaries are either sealed by depositional processes or used as pathways for significant soil degassing within this context self sealing both prevents long distance soil degassing and controls heat and volatile transfers near the dome a rough estimate of the co2 output through soils near the dome is 200 230 t day 1 i e 50 of the estimated total gas output from the volcano summit during these quiescent periods on merapi s southern slope a 2 500 m long co2 traverse shows low amplitude anomalies that fit well with a recently observed electromagnetic anomaly consistent with a faulted structure related to an ancient avalanche caldera rim sub surface soil permeability is the key parameter that controls the transfer of heat and volatiles within the volcano allowing its major tectonic architecture to be revealed by soil gas and soil temperature surveys

dome growth and coulee spreading controlled by surface morphology as determined by pixel offsets in photographs of the 2006 merapi eruption abstract at many explosive volcanoes viscous domes extrude which are destroyed by complete or partial collapses although the growth and development of silicic domes and the associated flow and collapse mechanisms are of vital importance for understanding the occurrence and scale of pyroclastic flows quantitative measurements of dome deformations are limited we report on a sequence of photographs taken of a growing and deforming dome a sequence in 2006 featuring the merapi dome taken from similar camera positions allow the application of a digital image correlation algorithm the aim being to detect and explore the temporal evolution of pixel offsets the results suggest that the dome underwent deformation in two regions between september and october 2006 i dome growth and spreading at the volcano summit and ii coulee flow through a narrow canyon the latter is associated with strain localization and flow acceleration which indicates that the displacements and flow velocities at silicic domes are governed by the topographic structure into which the flows develop the downslope motion of the distal parts of the flow and apron slumps continued during episodes of dome extrusion by gravitational spreading an analysis of the 2006 merapi dome and coulee displacement also provides insights into processes that may occur along the newly established southerly eruption direction which also may have influenced pyroclastic flows associated with the 2010 eruption

current accelerating seismic excitation along the northern boundary of the aegean microplate according to previous observations geophys res lett 27 2000 3957 the generation of large mz7 0 earthquakes in the western part of the north anatolian fault system marmara sea is followed by strong earthquakes along the northern boundary of the aegean microplate nab northwestermost anatolia northern aegean central greece ionian islands therefore it can be hypothesized that a seismic excitation along this boundary should be expected after the occurrence of the izmit 1999 earthquake m 7 6 we have applied the method of accelerating seismic crustal deformation which is based on concepts of critical point dynamics in an attempt to locate more precisely those regions along the nab where seismic excitation is more likely to occur for this reason a detailed parametric grid search of the broader nab area was performed for the identification of accelerating energy release behavior three such elliptical critical regions have been identified with centers along this boundary the first region a is centered in theeasternpartofthisboundary 40 2jn 27 2je southwestofmarmara thesecondregion b hasacenterinthemiddlepartof the boundary 38 8jn 23 4je east central greece and the third region c in the westernmost part of the boundary 38 2jn 20 9je ionian islands the study of the time variation of the cumulative benioff strain in two of the three identified regions a and b revealed that intense accelerating seismicity is observed especially after the occurrence of the 1999 izmit mainshock therefore it can be suggested that the seismic excitation at least in these two regions has been triggered by the izmit mainshock estimations of the magnitudes and origin times of the expected mainshocks in these three critical regions have also been performed assuming that the accelerating seismicity in these regions will lead to a critical point that is to the generation of mainshocks

magma eruption rates of merapi volcano central java indonesia during one century 1890 1992 the magma eruption rates of merapi volcano form 1890 to 1992 are re examined chronologically for this volcano movements of extruded lavas and domes as well as their extrusions are important because they control the modes of the subsequent activities and cause nuees ardentes and lahars the monthly eruption rates varied widely but the cumulative volume of lavas has increased linearly and is expressed as 0 1x106 m3 month the magma production rate of this volcano may have been constant for these 100 years recurrent excessive effusion of lavas is tentatively interpreted by assuming a magma reservoir the averaged eruption rate is small in comparison with other volcanoes such as nyramuragia kilauea and vesuvio however it is remarkable that the activity has been continuous for these 100 years and the total amount of lava discharged during this period reached more than 108 m3 a simple model for the formation of the 1992 lava dome is presented the viscosity of the lavas is probably between 106 and 107 p and the length of the magma conduit is probably less than 10 km

new observational information on the precursory accelerating and decelerating strain energy release recent reliable data are used to study the behavior of seismic activity before 46 strong shallow earthquakes m 6 0 which correspond to five complete samples of mainshocks these samples include 6 mainshocks m 6 0 7 1 that occurred in western mediterranean since 1980 17 mainshocks m 6 0 7 2 which occurred in the aegean greece and surrounding area since 1980 5 mainshocks m 6 4 7 5 that occurred in anatolia since 1980 12 mainshocks m 6 0 7 3 that occurred in california since 1980 and 6 mainshocks m 7 0 8 3 that occurred in japan since 1990 in all 46 cases a similar precursory seismicity pattern is observed specifically it is observed that accelerating benioff strain square root of seismic energy release caused by preshocks occurs in a broad circular region critical region with a radius about eight times larger than the fault length of the mainshock in agreement with results obtained by various research groups during the last two decades however in a much smaller circular region seismogenic region with a radius about four times the fault length the corresponding preshock strain decelerates with the time to the mainshock the time variation of the strain follows in both cases a power law but the exponent power is smaller than unit m 0 3 in the case of the accelerating preshock strain and larger than unit m 3 0 in the case of the decelerating preshock strain predictive properties of this decelerating in accelerating out strain model are expressed by empirical relations the possibility of using this model for intermediate term earthquake prediction is discussed and the relative model uncertainties are estimated

global observational properties of the critical earthquake model the preshock critical regions of 20 mainshocks with magnitudes between 6 4 and 8 3 which occurred recently since 1980 in a variety of seismotectonic regimes greece anatolia himalayas japan california were identified and investigated all these strong earthquakes were preceded by accelerating time to mainshock seismic crustal deformation benioff strain the time variation of the cumulative benioff strain follows a power law with a power value m 0 3 in very good agreement with theoretical considerations we observed that the dimension of the critical region increased with increasing mainshock magnitude and with decreasing long term seismicity rate of the region an increase of the duration of this critical preshock phenomenon with decreasing long term seismicity rate was also observed this spatial and temporal scaling expresses characteristics of the critical earthquake model which are of importance for earthquake prediction research we also showed that the critical region of an oncoming mainshock coincides with the preparing region of this shock where other precursory phenomena can be observed

an overview of the seismicity of merapi volcano java indonesia 1983 1994 abstract from 1982 to 1995 merapi volcano java indonesia experienced two main eruptive cycles from 1984 to 1986 and from 1992 to 1994 each cycle had a duration slightly larger than 2 years four major eruptive events occurred in 1984 1986 1992 and 1994 these eruptions were monitored by a telemetered seismic network we present an overview of the seismicity observed between 1983 and 1995 from seismological observations several types of characteristic events are recognised volcanotectonic earthquakes are standard microearthquakes either shallow an aseismic zone is situated between two seismic zones at a depth between 1 5 and 2 5 km below the summit we postulate that it is a small shallow magma reservoir where magma injected from below can be stored temporarily we try to relate seismic observations during both eruptive cycles to the initial injection of deep magma to the superficial magma system the first eruption in each case seems to involve magma enriched in gas that extrudes the content of the conduit and explodes the old dome a regular outflow of magma follows the initial explosion and gradually a dome is building up then it stops and a period of repose is observed later a second episode of dome growth occurs the height of the dome reaches a maximum corresponding to a state of lithostatic equilibrium the time delay of more than 2 years between the beginning and the end of a cycle may result from crystallisation in a volatile rich magma and from the building up of pressure in the superficial magma pocket some important events like the collapse of the dome on 22 november 1994 are not preceded by any seismic precursor when it reaches a large volume the dome is not stable and is likely to collapse by gravity for instance after the sudden influx of matter or gas or after a heavy rain on merapi tremors are observed but do not always precede a dangerous event

combination of a pressure source and block movement for ground deformation analysis at merapi volcano prior to the eruptions in 2006 and 2010 abstract we analyzed ground deformation prior to the eruptions in 2006 and 2010 at merapi volcano central java indonesia ground deformation was monitored by electronic distance measurement edm by measuring the slope distance toward 12 reflectors installed near the summit from five benchmarks on flanks every day a large change of slope distance csd was detected on the southeast and south baselines and a minor csd was detected on the north and northwest baselines during the pre eruptive stages of both the 2006 and 2010 eruptions we applied a block movement model to the south and southeast baselines and a spherical pressure source model to the csds on the north and northwest baselines using the finite element method fem the rates of block movement southward and the volume change of the pressure source increased on april 7 2006 and continued at constant rates until the appearance of a new lava dome on april 26 prior to the eruption in 2010 the block movement southeastward and the volume increase of the pressure source accelerated in the middle of october and acceleration continued until the first outburst on october 26 2010 temporal patterns of the block movement and the increase in the volume of the pressure source correlate well with the increase in seismicity of vt and mp earthquakes the pressure sources were obtained at a depth of 2 0 5 km below the summit and this position corresponds to the aseismic zone of vt earthquakes magma injection at the shallow part of this region causes an increase in the volume of the pressure source and inflation of the ground of the summit triggered gravitational slip southeastward or southward of the ground surface the volumes increases of the pressure sources were 9 7 1 m m 3 and 17 6 0 8 m m 3 in 2006 and 2010 respectively the volume increase is related to the scale and type of the eruption the effusive eruption in 2006 had a volcanic explosivity index vei of 2 and the explosive eruption in 2010 had a vei of 4 the directions and amounts of the block movement are strongly related to topography hydrothermally weak zone and underground gap near the summit between west and east domes

merapi central java indonesia an outline of the structural and magmatological evolution with a special emphasis to the major pyroclastic events abstract merapi volcano in the central part of java is regarded as the most active and most dangerous volcano in indonesia on the basis of field studies and geochronological data its history is divided into four periods ancient middle recent and modern merapi according to our preliminary age data the ancient period may have begun around 40 000 y bp and lasted until 14 000 y bp when the middle period begun the recent period begun around 2200 y bp and was replaced by the modern period after the eruption of 1786 during the middle merapi stage a mount st helens type edifice collapse occurred our data suggest that his event is younger than 6700 y bp and older than 2200 y bp during the recent merapi stage violent magmatic to phreatomagmatic eruptions twice interrupted the growth of the volcano the older gumuk phreatoplinian deposits cover the entire cone charcoal found within these deposits gave 14c ages of 2200 and 1470 y bp the overlying sambisari ash deposits were emplaced by violent pyroclastic surges directed towards the south i e to the present location of the town of yogyakarta they buried the shivaitic temple of sambisari at the start of the 15th century modern merapi is characterised by the persistent growth of a summit dome periodically interrupted by partial or total collapse of the dome to generate frequent merapi type nuees ardentes blocks and ash flows and associated surges or more exceptionally fall back st vincent type nuees ardentes scoria flows in contrast previous stages were characterised by effusion of long lava flows alternating with violent explosive phases generating essentially st vincent type nuees ardentes merapi lavas are calc alkaline with a compositional range between 49 5 and 60 5 wt sio2 moreover high k basaltic andesites represent about 90 of merapi lavas disequilibrium features are common in the mineralogical assemblage plagioclase orthopyroxene clinopyroxene olivine amphibole titanomagnetite scarce alkali feldspar macroscopic and microscopic textural heterogeneities are related to magma mixing that may have buffered the compositions of lavas and caused the restricted range of compositions our studies of past activity at merapi provide some insights into future activity and to related volcanic hazards it is clear that merapi has the potential of eruptions much more powerful than observed during the historic period

seismicity trends and potential for large earthquakes in the alaska aleutian region the high likelihood of a gap filling thrust earthquake in the alaska subduction zone within this decade is indicated by two independent methods analysis of historic earthquake recurrence data and time to failure analysis applied to recent decades of instrumental data recent may 1993 earthquake activity in the shumagin islands gap is consistent with previous projections of increases in seismic release indicating that this segment along with the alaska peninsula segment is approaching failure based on this pattern of accelerating seismic release we project the occurrence of one or morem 7 3 earthquakes in the shumagin alaska peninsula region during 1994 1996 different segments of the alaska aleutian seismic zone behave differently in the decade or two preceding great earthquakes some showing acceleration of seismic release type a zones while others show deceleration type d zones the largest alaska aleutian earthquakes in 1957 1964 and 1965 originated in zones that exhibit type d behavior type a zones currently showing accelerating release are the shumagin alaska peninsula delarof and kommandorski segments time to failure analysis suggests that the large earthquakes could occur in these latter zones within the next few years

miocene to recent tectonic evolution of the eastern mediterranean new pieces of the old mediterranean puzzle the mediterranean sea and its surrounding land mass fig 1 have long been recognized as an excellent bnatural laboratoryq for the study of fundamental plate tectonic processes including rifting passive margin development contraction and associated subduction ophiolite emplacement and orogenesis and as such it is one of the most extensively studied regions of the world e g hsu et al 1975 dixon and robertson 1984 kastens et al 1990 emeis et al 1996 comas et al 1996 robertson 1998 mcclusky et al 2000 the late cretaceous to holocene tectonic evolution of the eastern mediterranean region is extremely complex and controversial and several commonly conflicting hypotheses have been proposed the scope of this special issue does not permit a full discussion of these hypotheses we refer the reader to robertson 1998 for a review however there is general agreement that the eastern mediterranean evolved as a small ocean basin during the late triassic robertson and dixon 1984 robertson et al 1991 this embryonic ocean achieved its maximum

mechanical discontinuities monitoring at merapi volcano using kinematic gps merapi volcano java indonesia is in almost continuous activity with growth of an andesitic lava dome this dome frequently collapses to form potentially deadly glowing avalanches explosions and nuees ardentes to monitor the evolution of surface displacements and to model the associated magmatic sources we established a global positioning system gps network in 1993 and have measured it each year using the static gps method however the limited number of benchmarks and the geometry of the network did not allow us to precisely locate major mechanical discontinuities within the edifice precisely locating these discontinuities is of central importance because they delimit areas of potential instability and provide means to evaluate potential volumes of falling material the kinematic gps method offers a way to partially solve the problem of temporal and spatial sampling of the displacement field but its accuracy is usually insufficient to monitor small displacements we propose here a strategy of field measurements and adjustments which combines kinematic positioning 1 min and rapid static baselines 15 min to get a 1 5 cm error 95 confidence at merapi summit we have installed about 50 benchmarks covering the area around the main crater field measurements of this new network with our method take a few hours and the data processing has been automated we present the results of 8 surveys from 1999 to 2002 a period that includes a dome collapse in january 2001 our results show large horizontal displacements towards the northwest starting in july 2000 and reaching about 50 cm in amplitude in november 2000 that we interpret as precursors to the dome collapse we also locate two presently active discontinuities at the summit of the volcano this approach can be implemented easily on other active volcanoes

geochemical evolution of the rooiberg silicic lavas in the loskop dam area southeastern bushveld the rooiberg felsite is the voluminous volcanic precursor to the plutonic episodes of bushveld magmatism in the area north of the loskop dam a 3 520 m thickness of felsite is dominated by flows of dacitic and rhyodacitic lava occasional silicic andesites are developed near the base whereas true rhyolites become overwhelmingly dominant toward the top of the sequence nine major stratigraphic units of lava are present these are usually separated by and sometimes include volumetrically minor pyroclastic and sedimentary deposits whole rock chemical data on 165 lava samples embracing the entire stratigraphy suggest that nonuniform alteration processes have been most effective in the upper units nevertheless field petrographic and chemical criteria enable identification of three felsite magma types a high mg type mgo 1 7 containing low zr and y contents is present only within the lowermost 1 400 m of section a low mg type mgo 2 asymp 1 p 2 o 5 asymp 0 35 type which only occurs in the lower part of the succession the high mg lavas exhibit a systematic eruptive progression from more to less evolved compositions apparently reflecting continuous tapping of successively deeper levels of a normally zoned magma chamber during the early volcanism the low mg lavas were erupted intermittently with the high mg types probably from a separate and much larger chamber pronounced differentiation of this magma is only evident in the youngest volcanic units where several element profiles display conspicuous steplike variations across the prominent ash flow horizons the steps reflect upward enrichments in nb zr and y and corresponding incremental depletions in ti p and sc such trends imply the existence of a discontinuous but reversed compositional zonation in the evolved low mg chamber the high fe ti p lavas were also erupted from the low mg chamber this may indicate the development of an early type of chemical stratification that was markedly different from the compositional layering in the evolved system

earthquake rupture as a critical point consequences for telluric precursors abstract earthquakes are related to rupture phenomena in complex statistical systems of cracks we first review some available information suggesting that rupture in earthquakes is a critical point the consequences of this hypothesis on several phenomena are then discussed in particular we focus our attention on a simple theory of electroseismic activity based on mechano electrical transduction effects such as the piezoelectric or the pressure induced polarization effect the neighbourhood of the rupture threshold is characterized by a specific response which could correspond to telluric wave activity observed as precursors of earthquakes

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

combined seismicity pattern analysis dgps and psinsar studies in the broader area of cephalonia greece abstract ground deformation studies based on differential gps dgps measurements and permanent scatterer interferometric psi analysis have been conducted on the islands of cephalonia and ithaca covering the period 1992 to 2010 dgps measurements for the period 2001 to 2010 revealed horizontal clockwise rotation of cephalonia and velocities ranging from 3 to 8 mm yr with the largest values occurring at the western and southern parts of the island considering its vertical deformation two periods are distinguished on the basis of dgps and psi the first one 1992 to 2003 shows generally an almost linear slight subsidence around 1 mm yr which is consistent with expected neotectonic movements of the island the second one 2003 to 2010 has been tentatively attributed to dilatancy in which reversal to uplift 2 4 mm yr occurred mainly along the southern and southeastern parts of the island while larger magnitudes 4 mm yr took place at the western part these non linear high rates of uplift started at about mid 2005 and were of increasing rate at the southern part but of decreasing rate at the western part they may indicate a major regional crustal deformation process in an environment that has previously supported offshore large magnitude earthquakes parallel analysis of the observed seismicity in the broader area identified two seismically critical areas on the basis of the decelerating accelerating seismicity a major one south of cephalonia and west of zakynthos and another minor one at the nw part of peloponnese critical time estimates of the occurrence of a future strong seismic event in the above critical areas were also made based on i accelerating seismicity and ii the temporal analysis of the seismicity

a detailed tephrostratigraphic framework at merapi volcano central java indonesia implications for eruption predictions and hazard assessment abstract the upper part of merapi volcano is characterised by a summit crater breached to the southwest and occupied by an unstable lava dome episodes of dome growth have usually resulted in partial dome collapse events that have generated pyroclastic flows in recent years these have inundated the southwestern lower flanks and in the past other sectors of the volcano have been affected this recent pattern of volcanic activity since the 1880s is well known from direct observations in this study the eruptive record extending back to mid holocene times is deduced from the stratigraphy and chronology of volcaniclastic deposits this record forms an important basis from which the average periodicity of eruptions at merapi and the severity and the extent of future eruptions can be assessed the most complete record of eruptive activity from merapi volcano is found in the deeply dissected volcaniclastic fans of the lower flanks here successions of numerous coarse ash and lapilli beds are interbedded with andic soil material thin pyroclastic flow and surge deposits and a hitherto unrecognised inter regional tephra marker bed many of these tephra beds can be reliably correlated around the flanks of merapi volcano and can be distinguished on the basis of physical appearance and stratigraphic association these formations can be reliably used to correlate units around the flanks of the volcano in the deeper parts of this stratigraphic succession pyroclastic products originating from the adjacent merbabu volcano are also recognised and provide evidence of concurrent activity at both volcanoes it is clear from the stratigraphic record that relatively large magnitude eruptive volume to 3 7 108 m3 eruptions have been generated at merapi volcano these eruptive deposits are typically produced from pyroclastic flow and or pyroclastic fall events most of the fall beds are characterised by single to multiple upward fining pumiceous or scoriaeous units sometimes overlain by ash cloud surge beds isopach maps have been produced for several of these tephra beds and most of them show either west southwest south and southeast dispersion except for the ngrangkah tephra which shows no systematic direction or distribution sub plinian or plinian to vulcanian open vent styles of activity appear to have been common at merapi volcano such eruptive episodes are in contrast with the style of activity that had been occurring at merapi volcano in the last two centuries clearly the range of eruptive events likely to be experienced at merapi volcano needs to be more critically considered in any existing or future hazard assessment and contingency planning programme

the pre eruption conditions for explosive eruptions at merapi volcano as revealed by crystal texture and mineralogy abstract we analyze the textures and mineralogy of merapi tephra generated during explosive vei 3 4 eruptions over the past 2000 years and compare these data with those observed for merapi dome and flow lavas we find that the merapi pumiceous tephra and lava textures differ significantly with respect to small size crystal populations but that phenocryst textures are generally similar a similar initial phase of crystallization is indicated for tephras and lavas in mid crustal 10 km depth reservoirs subsequent textural differences are mainly affected by ascent rate and degassing during ascent and for dome lavas with temporary storage in shallower reservoirs these differences also correspond to different eruptive styles our analyses include study of pumices lava and breadcrust bomb samples including samples from some of the most recent explosive episodes prior to the 2010 eruption textural analyses of youthful breadcrust bomb samples yield insights on one type of transition between effusive and explosive eruptive styles involving pressure build up under a degassed crystalline shallow conduit plug in general comparison of the crystal size distributions and calculated residence times among the effusive and explosive eruptive styles suggests that the two main magma product types resided for similar lengths of time in a mid crustal reservoir before ascending toward the surface and either erupting explosively tephra or stagnating in a shallow magma chamber prior to extrusion lava the interpretation is supported by the occurrences of amphibole in pristine condition in tephra and in altered state in lava finally the 1872 and 2010 explosive eruptions are examined and compared with others over the past three millennia the 2010 bulk rock compositions overlap with products of other major explosive merapi eruptions such as the ngrangkah tegalsruni temusari and kepuharjo tephras the 2010 products show a gradational late stage mafic enrichment dissimilar to 1872 which showed little

time independent and time dependent seismic hazard in greece based on seismogenic sources abstract an improved procedure is followed to assess time independent andtime dependent hazard for 144 broad sites cities towns villages of greece in termsof expected macroseismic intensities at each one of these sites in this procedureseveral new results are taken into account source parameters based on new researchwork on seismicity and on other relative information new regionalization and im proved seismicity data parameters and anisotropic radiation at the seismic source anew relation for the attenuation of macroseismic intensities and the effect of localconditions site effects on the strong ground motion analytic relations and tables determined by this procedure permit the reliableassessment of time independent hazard in terms of macroseismic intensity in mmscale peak horizontal ground acceleration and velocity at each one of these 144sites and at any probability level time dependent hazard has been also assessed for these 144 broad sites in greece in terms of the probability for the occurrence of strong ground motion with macro seismic intensity i vii in mm scale at each one of these sites during the period1996 2010 comparison of the assessed time dependent hazard with observed ma croseismic intensities of the period 1950 1995 indicates that the time dependentmodel gives very reasonable results introduction