chemographic relationships of biotite and cordierite in the mcgerrigle thermal aureole gaspe quebec biotite and cordierite occur in a 1 km wide zone of pelitic hornfelses around the mcgerrigle pluton these phases display systematic changes in xfe that can be attributed to continuous reactions involving chlorite or andalusite in the system kfmash through much of the zone biotite and cordierite were products of the breakdown of chlorite close to the pluton this continuous reaction was terminated by a discontinuous reaction that introduced andalusite pelites which interdigitate with apophyses of the intrusive at the pluton margin contain assemblages that record a continuous reaction between biotite cordierite andalusite muscovite and quartz or alternatively the discontinuous breakdown of muscovite and quartz to k feldspar and andalusite the mole fraction of fe in biotite and cordierite increased significantly with the progress of the first continuous reaction and apparently decreased during the second continuous reaction the kd of fe mg between the minerals decreased and apparently increased respectively during the two reactions biotite cordierite chlorite assemblages are interpreted to have been stable at temperatures between 525 c and 615 c and biotite cordierite andalusite assemblages stable at temperatures between 615 c and 635 c the confining pressure was estimated to have been 2 kbar the results of this study suggest that the kd of fe mg between biotite and cordierite is a function of temperature the fe mg exchange characteristics of the controlling continuous reaction and non ideal mixing of fe and mg

a petrogenetic grid for pelites in the ballachulish and other scottish thermal aureoles the ballachulish granite is a composite devonian intrusive complex surrounded by a distinctive thermal aureole developed in regionally deformed and metamorphosed dalradian sediments on the w coast of scotland the most abundant rocks in the aureole are pelites which show a progression of assemblages from quartz muscovite chlorite up to a variety of high grade assemblages involving combinations of cordierite corundum spinel and rarely hypersthene and garnet metamorphic zones have been mapped around the granite which are defined by the following reactions going upgrade mu chl q cd bi v mu bi q cd kf v or mu cd q bi as v mu q as kf v q bi as cd kf v or mu cd bi as kf v mu cor kf v bi as cor kf cd v the restricted occurrences of assemblages involving spinel hypersthene and garnet do not allow higher grade zones to be mapped variations in the reaction sequence as a consequence of bulk compositional factors in particular the development of quartz bearing versus quartz absent assemblages are described details of the mineral assemblages from ballachulish are combined with high grade assemblage data from the belhelvie lochnagar and comrie aureoles to construct a comprehensive schematic petrogenetic grid the grid involves the minerals quartz chlorite muscovite biotite cordierite alumino silicate k feldspar corundum spinel hypersthene and garnet whose assemblage relationships are modelled in the system k 2 o feo mgo al 2 o 3 sio 2 h 2 o kfmash

baltic sea ice sar segmentation and classification using modified pulse coupled neural networks a method for segmentation and classification of baltic sea ice synthetic aperture radar sar images based on pulse coupled neural networks pcnns is presented also automated training which is based on decomposing the total pixel value distribution into a mixture of class distributions is presented and discussed the algorithms have been trained and tested using logarithmic scale radarsat 1 scansar wide mode images over the baltic sea ice before the decomposition into mixture of class distributions an incidence angle correction specifically designed for these baltic sea ice sar images is applied because the data distributions in the uniform areas of these images are very close to gaussian distributions the data are decomposed into a mixture of gaussian distributions using the expectation maximazation algorithm only uniform image areas are used in the decomposition phase the mixture of distributions is compared to the distributions of the baltic sea ice classes based on earlier scatterometer measurements and visual video interpretations of the sea ice classes the parameter values for the pcnn segmentation are defined based on this mixture of distributions the pcnn segmentation results are also compared to the operational sea ice information of digitized ice charts and to visual interpretation of the sea ice class

significance of the early fabric in the contact metamorphic aureole of the 590 ma ben vuirich granite perthshire scotland an early fabric is preserved in pseudomorphs of contact metamorphic cordierite and andalusite found in hornfelsed dalradian rocks at the nw margin of the ben vuirich granite as previous work had suggested that this fabric may be of regional tectonic d1 origin and taken as evidence that a pre 590 ma neoproterozoic orogenic event had affected the dalradian supergroup the textures found in the hornfelses and their porphryoblasts are illustrated and described in detail three types of hornfels are recorded unspotted cordierite and andalusite bearing cordierite was altered to mica garnet and kyanite and andalusite pseudomorphed by kyanite during the subsequent d2 regional metamorphism the early fabric is finely spaced and associated with a weak shape fabric except in the higher grade hornfelses where it is more intensely developed and formed during the deformation of irregularly shaped cross cutting granitic veinlets it is concluded that the hornfels fabric is probably bedding modified by intrusion related deformation rather than a d1 fabric parallel to bedding the implication of this finding is that intrusion of the ben vuirich granite occurred during the vendian c 650 ma rifting phase at about the time that the tayvallich lavas were being deposited and before any significant deformation of the dalradian rocks had taken place there is no unambiguous evidence to show that the early fabric in the hornfels at ben vuirich formed during a precambrian regional scale deformation of the dalradian block

fluid evolution and its role in the genesis of the granite related madeleine copper deposit gaspe quebec the madeleine copper deposit is hosted by biotite hornfels adjacent to the mcgerrigle granitic complex quebec and consists of stockwork orebodies outwardly zoned from bornite chalcopyrite to chalcopyrite pyrrhotite the mineralization predated the peak of contact metamorphism and is associated with biotite and calc silicate vein and alteration assemblages chlorite muscovite alteration and quartz carbonate veins postdated mineralization vein quartz contains low and high salinity aqueous and co 2 ch 4 aqueous and nonaqueous fluid inclusion types isochore projections suggest that the deposit formed at 400 degrees to 600 degrees c and 1 to 2 kbars low ice melting and eutectic temperatures indicate that some aqueous inclusions have high calcium contents a model has been developed for the fluid evolution in which interaction of high salinity orthomagmatic fluids with organic rich shales produced ch 4 n 2 rich fluids and caused biotite alteration locally the orthomagmatic fluids interacted with calcareous beds releasing co 2 and increasing their calcium content the latter subsequently caused calc silicate alteration chlorite muscovite alteration and quartz carbonate veining were caused by lower salinity fluids derived largely from formational waters outwardly decreasing water rock ratios which produced corresponding decreases in temperature and or cu fe and or increases in a sub h 2 s are invoked to explain the observed zonation in sulfide mineralogy

multisensor data and thermodynamic sea ice model based sea ice thickness chart with application to the kara sea arctic russia we introduce a method to construct an ice thickness chart using two satellite datasets and a one dimensional high resolution thermodynamic snow and sea ice model hightsi thin ice thickness up to 40 cm is retrieved using modis ice surface temperature data for thicker ice thickness is retrieved from a combination of sar image and background level ice thickness chart h i provided by hightsi because h i is inherently static we utilize passive microwave data based sea ice concentration charts to introduce mesoscale ice dynamics into h i in order to create the thickness chart the value of modified h i is scaled by a factor which depends on the magnitude of backscattering coefficient 0 the proposed method is effective in cold winter conditions we calculated a series of ice thickness charts covering the kara sea arctic russia during winter 2008 09 the ice thickness charts were validated against russian ice charts our method gave realistic results in the thickness range 30 120 cm and was uncertain for the detection of thinner ice areas due to the limitations in our reference dataset more validation work is needed to establish the accuracy in more detail our thickness charts can be used for operational purposes and in climate studies

spatial aftershock distribution of the 26 december 2004 great sumatra andaman earthquake in the northern sumatra area 1 in july 2005 about 6 months after the 2004 great sumatra andaman earthquake 20 ocean bottom seismometers were deployed in the northern sumatra area more than 1000 events were identified during the 12 day recording period after relocation the seismicity shows different patterns on each side of the lower splay fault east of this feature and beneath the aceh basin and fore arc the deep earthquakes outline the subduction megathrust fault west of it the aftershocks distribution is strongly influenced by the active n s oceanic fracture zones of the subducted plate two n s trending clusters of 10 to 50 km deep earthquakes observed below the lower wedge are interpreted as reactivated oceanic fracture zones the postseismic activity suggests a significant influence of the n s active fracture zones of the oceanic plate on the toe of the wedge explaining the dextral wrenching of wedge thrusts in the morphology the megathrust fault does not extend to the trench but outcrops east of these active oceanic fractures and seems to merge upward along the lower splay fault where shallow earthquakes are observed

comment on tidal synchronicity of the 26 december 2004 sumatran earthquake and its aftershocks by r g m crockett et al 1 crockett et al 2006 report a striking coincidence of some of the larger recent earthquakes around the sunda andaman java trench regions with the times of the full and new moon however it may be worth noting that the results contradict nearly all previous studies and theoretical expectations and the statistics invoked have some problems 2 two flavors of earthquake tide correlations have been sought with either the diurnal stress variations or the biweekly modulations in the amplitude of the stress envelope a correlation with both tidal periods has occasionally been noted in the case of seismicity just below the ocean floor at mid ocean ridges but in each reported case the correlation with biweekly tides was much weaker than the correlation with diurnal tides wilcock 2001 tolstoy et al 2002 extensive data on global tectonic earthquakes have sometimes shown evidence of a correlation with diurnal tides tanaka et al 2002 tsuruoka et al 1995 especially in the case of the strongest tides cochran et al 2004 however none of the studies report seeing a correlation with the biweekly tide even regional studies of far larger sets of earthquakes in the san francisco bay area mcnutt and heaton 1981 kennedy et al 2004 and the pacific northwest kennedy et al 2004 find no measurable correlation as stated by hartzell and heaton 1989 the difference in the amplitude of the biweekly tidal stress envelope is much smaller than the diurnal peak to peak stress variation with diurnal stress variation being over 5 times larger than the biweekly variation along the same vein theoretical studies predict a correlation with the diurnal but not biweekly tides due to the small overall amplitude variation of biweekly tides dieterich 1987 3 crockett et al 2006 base their conclusions on a comparison with the lunar phase only however it has been well documented for example in a review by emter 1997 that the tidal time series must be computed in relation to the focal mechanism to derive a useful correlation in addition crockett et al 2006 do not include the ocean tide component of the tidal stress in their correlation even though the ocean tide component is often an order of magnitude larger than the solid earth tide in subduction zone coastal environments depth matters as well for example tsuruoka et al 1995 show that tides calculated at the surface can be opposite in phase to tidal time series at hypocentral depths when ocean loading is taken into account 4 perhaps most importantly the statistics employed by crockett et al 2006 are somewhat problematic schuster s test is only valid for independent datasets in which events occur at random this test can produce a false positive result if the data set is not random and so should not be used for statistical tests on catalogs that include aftershocks therefore the statistics given by crockett et al 2006 for the raw clustered catalog are invalid specifically in the clustered catalog the times of aftershocks of the m9 3 megathrust dominate the sample and they are not uncorrelated in time rather they tend to occur just after the mainshock as aftershocks are prone to do 5 the most compelling statistic of crockett et al 2006 is the one derived from 13 14 declustered events happening near the quadrants of either the full or new moons an only 1 in a 100 chance of finding the result at random is cited but the paper documentation suggests the degrees of free

sea ice deformation state from synthetic aperture radar imagery part ii effects of spatial resolution and noise level c and l band airborne synthetic aperture radar sar imagery acquired at like and cross polarizations over sea ice under winter conditions is examined with the objective to study the discrimination between level ice and ice deformation features high resolution low noise data were analyzed in the first paper in this second paper the main topics are the effects of spatial resolution and signal to noise ratio airborne high resolution sar scenes are used to generate a sequence of images with increasingly coarser spatial resolution from 5 to 25 m keeping the number of looks constant the signal to noise ratio is varied between typical noise levels for airborne imagery and satellite data areal fraction of deformed ice and average deformation distance are determined for each image product at l band the retrieved values of the areal fraction get larger as the image resolution is degraded the areal fraction at c band remains constant the retrieved average distance between deformation features increases both at c and l bands as the image resolution gets coarser the influence of noise becomes noticeable if its level is equal or larger than the average intensity backscattered from the level ice the retrieval of deformation parameters using simulated images that resemble ers 2 sar envisat asar and alos palsar data products is discussed basic differences between real and simulated ers 2 sar images are analyzed

observations of sea ice thickness surface roughness and ice motion in amundsen gulf 1 ice thickness and surface roughness measurements of first year fy sea ice were collected with a fix mounted helicopter borne electromagnetic hem laser system in amundsen gulf in april to may 2004 the modal ice thickness values are in good qualitative agreement with different ice types identified in synthetic aperture radar sar imagery and shown on ice charts produced by the canadian ice service modal ice thickness values which generally represent level ice thicknesses were about 2 0 m over landfast ice a large range of modal ice thicknesses was observed in the mobile ice region with values of about 0 2 m young ice in leads where there was high radar backscatter 0 6 m thin fy ice in the polynya where there was medium to high backscatter and about 1 1 1 9 m thick fy ice elsewhere high surface roughnesses are strongly associated with high radar backscatter in sar imagery and are observed in areas of large shear the ratio of the standard deviations of ice draft and averaged roughness in an area of landfast ice is in good agreement with the ratio of the standard deviations of ice draft and ice equivalent roughness expected from isostasy with constant level ice and snow thickness however the standard deviation of ice equivalent roughness may be significantly underestimated due to differences in snow thickness between level and deformed ice and limitations of the laser processing method modal ice plus snow thicknesses measured with the hem system are within the range of historical values measured at cape parry

comment on the great sumatra andaman earthquake of 26 december 2004 lay et al research articles 20 may 2005 p 1127 estimated a 600 km length for the tsunami source region adding tide gauge data from paradip the northernmost of the indian east coast stations and therefore the most critical constraint on the northern extent of the source we estimate that its length was greater by 30

depth of emplacement fluid provenance and metallogeny in granitic terranes a comparison of western thailand with other tin belts the most important tin mineralization in thailand is associated with the late cretaceous to middle tertiary western thai granite belt a variety of deposit types are present in particular pegmatite vein and greisen styles of mineralization a feature common to most of the deposits is that they are associated with granites that were emplaced into the khang krachan group which consists of poorly sorted carbonaceous pelitic metasediments most of the deposits contain low to moderately saline aqueous fluid inclusions and aqueous carbonic inclusions with variable ch4 co2 ratios low salinity aqueous inclusions represent trapped magmatic fluid in at least one case the nong sua pegmatite based on their occurrence as primary inclusions in magmatic garnet aqueous carbonic inclusions are commonly secondary and neither the co2 nor nacl contents of these inclusions decrease in progressively younger inclusions implying that they are not magmatic in origin reduced carbon is depleted in the metasediments adjacent to granites and the d values greisen muscovites are variable but are as low as 134 per mil indicative of fluid interaction with organic graphitic material this suggests that the aqueous carbonic fluid inclusions represent fluids that were produced at least in part during contact metamorphism metasomatism by comparing the western thai belt with other sn w provinces it is evident that there is a strong correlation between fluid composition and pressure in general low to moderately saline aqueous inclusions and aqueous carbonic inclusions are characteristic of mineralization associated with relatively deep plutonic belts mineralized pegmatites are also typically of deeper plutonic belts and pegmatite hosted deposits may contain cassiterite that is magmatic crystallized from granitic melt or is orthomagmatic hydrothermal crystallized from aqueous or aqueous carbonic fluids in origin the magmatic aqueous fluids those that were exsolved from granitic melts are interpreted to have had low salinities as a consequence of the low salinities tin is partitioned in favour of the melt on vapour saturation thus with a high enough degree of fractionation the crystallization of a magmatic cassiterite or different sn phase such as wodginite is inevitable because tin is not partitioned in favour of the vapour phase upon water saturation of the granitic melts it is proposed that relatively deep vein and greisen systems tend to form by remobilization processes in addition many deeper greisen systems are hosted in part by carbonaceous pelitic metasediments and the reduced nature of the metasediments may play a key role in remobilizing tin sub volcanic systems by contrast are characterized by high temperature high salinity fluids owing to the high chlorinity tin is strongly partitioned in favour of the vapour and cassiterite mineralization can form by of orthomagmatic hydrothermal processes similar relationships between the depth of emplacement and fluid composition also appear to apply to other types of granite hosted deposits such as different types of molybdenum deposits

defining the source region of the indian ocean tsunami from gps altimeters tide gauges and tsunami models abstract to understand the role of the co seismic moment magnitude mw 9 1 9 3 sumatra andaman earthquake rupture mechanism on the severity of the indian ocean tsunami we used permanent global positioning system gps data and carried out an analysis of co seismic displacement and tsunami models tsunami modelling validated against independent jason 1 altimetry data and tsunami arrival time data as determined from tide gauges was used to analyse the results of five co seismic slip inversions using gps seismicity and or uplift data in this way we determined the most likely slip distribution characterized by slip maxima of 20 m in the south and 20 m in the north we used both the distribution and temporal evolution of the co seismic slip as derived from the gps data we show that the 9 min propagation time of the rupture led to constructive interference of waves radiating first from the south and minutes later from the north strengthening the tsunami in southern india sri lanka and thailand we conclude that the incorporation of permanent real time gps stations would represent a valuable component of future tsunami warning systems

comparison between c band synthetic aperture radar and 3 d laser scanner statistics for the baltic sea ice 1 a statistical analysis was performed for nearly simultaneously acquired c band synthetic aperture radar sar images and ice freeboard statistics the data analyzed were collected during a cryosat calibration validation campaign in march 2005 in the baltic sea the 3 d ice freeboard topography along transects with a total length about 150 km and width of 300 m was constructed from cross track scanning airborne laser scanner measurements the sar image data set consisted of two nearly coincident envisat advanced synthetic aperture radar alternating polarization precision and image mode precision images at hh polarization with their incidence angle ranges deviating about 20 the data set represents primarily low salinity thin first year ice with high ice concentration and thin snow cover under cold weather conditions the variance of the mean freeboard increased with increasing mean freeboard with the chosen window size 300 m up to the mean freeboard of 15 cm this multiplicative character of sea ice cover forms the basis by which we can expect that the c band backscattering coefficient response which depends only on the ice surface roughness and the top part of ice medium can provide information on the sea ice thickness a nonlinear regression model with three control variables the backscattering coefficient the dominant thickness of the level ice which has deformed and a variable accounting the effect of the sar incidence angle was established to predict the variation of the ice freeboard the applied bayesian approach also provided means to estimate the uncertainty range for the model fitting and the model predictions the modeled predictions were mostly in good agreement with the measured values the predictions for three different test lines accounted for 67 85 of the measured freeboard variance in 300 m scale in cold conditions with thin snow cover it was possible to estimate the degree of ice deformation and ice thickness quantitatively from c band sar images

rupture process of the 2004 sumatra andaman earthquake from tsunami waveform inversion the aim of this work is to infer the slip distribution and rupture velocity along the rupture zone of the 26 december 2004 sumatra andaman earthquake from available tide gage records of the tsunami we selected waveforms from 14 stations distributed along the coast of the indian ocean then we subdivided the fault plane into 16 subfaults both along strike and downdip following the geometry and mech anism proposed by banerjee et al 2005 and computed the corresponding green s functions by numerical solution of the shallow water equations through a finite difference method the slip distribution and rupture velocity were determined simul taneously by means of a simulated annealing technique we compared the recorded and synthetic waveforms in the time domain using a cost function that is a trade off between the l1 and l2 norms preliminary tests on a synthetic dataset together with a posteriori statistical analysis of the model ensemble enabled us to assess the ef fectiveness of the method and to quantify the model uncertainty the main finding is that the best source model features a nonuniform distribution of coseismic slip with high slip values concentrated into three main patches the first is located in the southern part of the fault off the coast of the aceh province the second between 6 5 n and 11 n and the third at depth between 11 n and 14 n furthermore we estimated that the rupture propagated at an average speed of 2 0 km sec

nucleation and triggering of earthquake slip effect of periodic stresses abstract results of stability analyses for spring and slider systems with state variable constitutive properties are applied to slip on embedded fault patches unstable slip may nucleate only if the slipping patch exceeds some minimum size subsequent to the onset of instability the earthquake slip may propagate well beyond the patch it is proposed that the seismicity of a volume of the earth s crust is determined by the distribution of initial conditions on the population of fault patches that nucleate earthquake slip and the loading history acting upon the volume patches with constitutive properties inferred from laboratory experiments are characterized by an interval of self driven accelerating slip prior to instability if initial stress exceeds a minimum threshold this delayed instability of the patches provides an explanation for the occurrence of aftershocks and foreshocks including decay of earthquake rates by time 1 a population of patches subjected to loading with a periodic component results in periodic variation of the rate of occurrence of instabilities the change of the rate of seismicity for a sinusoidal load is proportional to the amplitude of the periodic stress component and inversely proportional to both the normal stress acting on the fault patches and the constitutive parameter a 1 that controls the direct velocity dependence of fault slip values of a 1 representative of laboratory experiments indicate that in a homogeneous crust correlation of earthquake rates with earth tides should not be detectable at normal stresses in excess of about 8 mpa correlation of earthquakes with tides at higher normal stresses can be explained if there exist inhomogeneities that locally amplify the magnitude of the tidal stresses such amplification might occur near magma chambers or other soft inclusions in the crust and possibly near the ends of creeping fault segments if the creep or afterslip rates vary in response to tides observations of seismicity rate variations associated with seasonal fluctuations of reservoir levels appear to be consistent with the model

surface roughness of baltic sea ice small medium and large scale measurements of sea ice surface roughness were carried out in the baltic sea over a 3 year period a clear relationship was found between the rms height and correlation length of baltic sea ice in most cases the surface correlation function was close to exponential the logarithm of rms height showed a linear dependence on that of measured distance similarly the correlation length was in many cases linearly dependent on the measured distance this dependence on length suggests that ice surface roughness could be characterized as a fractal

c o h n salt fluids associated with contact metamorphism mcgerrigle mountains quebec a raman spectroscopic study abstract contact metamorphism and metasomatism of a sequence of cambro ordovician pelitic calcareous and psammitic metasediments in the thermal aureole of the devonian mcgerrigle pluton has resulted in the generation of a wide variety of fluid compositions which can be described by the system c o h n salt microthermometric and raman spectroscopic data on fluid inclusions trapped in quartzsulfide veins adjacent to the intrusive contact indicate that three fluid types existed in the aureole 1 h 2 o 2 h 2 o co 2 and 3 ch 2 n 2 co 2 the aqueous fluids have salinities which range from 0 to 50 eq wt nacl cacl 2 this range in fluid compositions resulted from the progressive devolatilization of a variety of lithologies and the release of waters from the intrusion the range in salinity of the aqueous fluids is attributed to variable contributions of high salinity waters from the intrusions and lower salinity dehydration and formation waters some of the co 2 may be orthomagmatic however most of it probably came from decarbonation of calcareous and possibly carbonaceous lithologies ch 4 and n 2 were generated in pelitic units during thermal metamorphism ch 4 from reactions involving bitumen and graphite and n 2 from nh 2 in silicate minerals and possibly from bitumen the restriction of high mole fractions of ch 4 and n 2 to water free fluid inclusions can be explained by fluid immiscibility within the fracture system the partitioning of co 2 between water poor and water rich fluids was less extreme and in some cases co 2 and h 2 o may have been completely miscible

development of seasonal pack ice in the beaufort sea during the winter of 1991 1992 a view from below subsea sonars moored in the beaufort sea acquired a spatial section of draft across 941 km of sea ice during the winter of 1991 1992 these observations document the development of seasonal sea ice from an open sea surface in october to an average accumulation exceeding 2 5 m draft by early april initially level ice occupied 85 of the profile but continued ridging reduced this fraction to 50 in late winter three modes of level ice were tracked that of seasonal ice whose growth was initiated at freeze up and two others created during openings of the ice field in january and in march the growth of these modes can be closely matched by calculations based on a slab model of ice formation forced using surface meteorological data initially ridge keels were small and widely spaced by midwinter an exponential dependence of keel frequency on draft was obvious e folding scale 2 16 m and the frequency and mean draft of keels had stabilized the maximum keel draft was a modest 17 4 m the low incidence of deep keels at all times is a statistically significant departure from the exponential dependence valid at lesser drafts the truncation point of the exponential relation is related to the draft of the thinnest level ice present in late winter the formation of deeper keels from thick first year ice was apparently precluded by the presence of younger thinner ice which limited the force available for ridge building through calculation of the seaward transport of ice over the sonars the total production of ice in the coastal flaw lead during 1991 1992 was determined to be about 60 of earlier indirect estimates in general the observations revealed winter ice conditions significantly less severe than those found on the periphery of the polar pack only a few tens of kilometers to the north but more so than conditions in a marginal first year ice zone at the same latitude in davis strait

reply to comment by elizabeth s cochran and john e vidale on tidal synchronicity of the 26 december 2004 sumatran earthquake and its aftershocks we are grateful to cochran and vidale for their comment which has stimulated us to clarify and reflect further upon the periodic relationships observed as well as to elaborate upon various matters that stemmed from a combination of our own understatement and the way we handled the constraints of brevity in relation to our unexpected findings nevertheless their respected comment appears to us to be often inappropriate in part or whole the comment does not appear to us to be either sufficiently convincing or powerful to invalidate either the methods or the conclusions of our paper i e that the timing of the major earthquakes during the ten month period for the study region does correlate with the lunar tidal cycles these conclusions are now further supported by our most recent and extended analysis as reported here

rafting and ridging of thin ice sheets rafting and pressure ridging are important processes in the deformation of sea ice that occur when two ice sheets are pushed together in this study a two dimensional computer model of the rafting and ridging process is used to simulate a situation in which two identical ice sheets are pushed together at constant speed each model ice sheet is composed of two thicknesses of ice the ratio of the thicknesses is varied to obtain degrees of inhomogeneity the accuracy of the simulations is assessed by comparison with a series of similar physical experiments performed in a refrigerated basin following this comparison the computer model is used to perform an extensive series of simulations to explore the effect of the thickness and the thickness inhomogeneity of the model ice sheets on the likelihood of occurrence of ridging and rafting during the simulations the energy consumption and forces are explicitly calculated the energy consumed during the simulations is used to demonstrate the smooth transition between ridging and rafting that occurs when the homogeneity of the sheets is varied

an experimental investigation of the chlorite terminal equilibrium in pelitic rocks experiments on the stability of chlorite in the presence of muscovite and quartz were performed in the system k20 mgo feo ai203 siorh20 the hydrothermal experiments were done at the quartz fayalite magnetite oxygen buffer using both natural and synthetic crystalline starting materials results of the experiments show that chlorite of intermediate fe mg is stable to higher temperatures at a given pressure than the endmember compositions chlorite is more magnesian than co existing biotite but plots to the fe side of the tie line connecting coexisting biotite and cordierite on the afm diagram magnesian chlorite breaks down in metapelitic rocks by the continuous reaction chlorite muscovite biotite cordierite h20 the assemblage chlorite biotite cordierite muscovite quartz exists stably over a narrow temperature range at a given pressure and for a very small range of rock composition

rupture process of the 2004 sumatra andaman earthquake the 26 december 2004 sumatra andaman earthquake initiated slowly with small slip and a slow rupture speed for the first 40 to 60 seconds then the rupture expanded at a speed of about 2 5 kilometers per second toward the north northwest extending 1200 to 1300 kilometers along the andaman trough peak displacements reached 15 meters along a 600 kilometer segment of the plate boundary offshore of northwestern sumatra and the southern nicobar islands slip was less in the northern 400 to 500 kilometers of the aftershock zone and at least some slip in that region may have occurred on a time scale beyond the seismic band

an approach to the validation of thermal and electromagnetic earthquake precursors effects of earth tides abstract it has been debated for years whether earth tides trigger earthquakes a recent statistical study has proven the significance of earth tides in earthquake triggering in this paper we firstly show that large earthquakes in the region of the 2004 sumatra earthquake m9 0 occur largely during a specific phase of the moon then we show that the observed thermal electromagnetic precursors of the outgoing long wave earth radiation and the vlf propagation anomaly ionospheric perturbation at the time of an earthquake are modulated by the tidal effect of the region finally we propose a model to explain the observed behaviors of the thermal electromagnetic precursors and show that tidal stress can trigger earthquakes leading also to thermal electromagnetic signatures

d anisotropy beneath southeast asia 1 earthquakes from the banda sea and flores sea region recorded at the kyrgyz network in the tien shan region show evidence for anisotropy in the lowermost mantle beneath south east asia shear wave splitting is measured for the scs phase after a receiver side correction is applied individual results show scatter in measured time lag and fast direction but stacking these gives a stable estimate of 0 8 0 04 s and 43 4 degrees this equates to a fast shear wave with a polarisation deviation from horizontal at the bounce point of around 9 degrees the simplest model to explain is a transversely isotropic medium with a slight dip to the east and an inferred anisotropy of 0 25 this is compatible with previous observations of vsh vsv for this region scenarios which might explain the observed anisotropy include sheared melt pockets or aligned post perovskite crystals associated with palaeosubduction of the pacific plate and indian plate

implications of u pb and k ar geochronology for petrogenesis and cooling history of the mcgerrigle mountains plutonic complex gaspe quebec the high level mcgerrigle mountains plutonic complex consists of a compositionally diverse gabbro to granite hybrid suite at its northern end and a relatively homogeneous granite suite in its southern half field and geochemical evidence support formation by hybridization between at least three end member magmas new u pb zircon and titanite ages from these end members indicate that intrusion of all components took place at 391 3 3 4 ma eighteen new k ar mineral ages which cover the range 370 390 ma suggest that the granite suite cooled quickly to 500 c in less than 2 ma whereas temperatures between 600 and 500 c may have been maintained over an extended period 5 15 ma within the hybrid suite the long lived thermal anomaly associated with the hybrid suite may explain the large epimetamorphic 300 c halo surrounding this suite and the existence of hydrothermal mineralization madelaine cu and candego pb zn ag deposits adjacent to it

the great sumatra andaman earthquake of 26 december 2004 the two largest earthquakes of the past 40 years ruptured a 1600 kilometer long portion of the fault boundary between the indo australian and southeastern eurasian plates on 26 december 2004 seismic moment magnitude mw 9 1 to 9 3 and 28 march 2005 mw 8 6 the first event generated a tsunami that caused more than 283 000 deaths fault slip of up to 15 meters occurred near banda aceh sumatra but to the north along the nicobar and andaman islands rapid slip was much smaller tsunami and geodetic observations indicate that additional slow slip occurred in the north over a time scale of 50 minutes or longer

top bottom multisensor remote sensing of arctic sea ice the arctic sea ice cover has been studied using near simultaneous observations by passive and active synthetic aperture radar sar microwave sensors upward looking and sidescan sonars a lidar profilometer and an infrared sensor data from two aircraft and a submarine over an approximately 100 km track of central arctic sea ice were registered and analyzed to evaluate the characteristics of the ice cover and the utility of each sensor in ice studies the results of comparative and correlation analyses are as follows the probability density functions of ice draft from sonar and elevation from lidar were found to be almost identical when isostasy is taken into account this result suggests that the basic ice thickness distribution can be derived from the surface topography measurements alone reasonable correlation was found between sar backscatter and ice draft or elevation especially when scales were adjusted such that 15 20 sar pixels were averaged however surface roughness derived directly from standard deviations in the lidar elevation data was found to be poorly correlated to the sar backscatter these results indicate that the sar values are affected more by scattering from the ice than from the snow covered surface the active and passive microwave sensors are shown to generally complement each other as the two sensors are especially sensitive to different physical properties of the sea ice undeformed first year ice showed low backscatter values but high brightness temperatures while some multiyear ice showed high backscatter values and low brightness temperature however surfaces identified as multiyear ice by the passive system have a large spread in the unaveraged sar backscatter indicating limitations when using a one channel sar for ice type identification at the highest resolution also ridged ice identified by sonar and sar data covers a large range of passive microwave emissivity suggesting considerable variability in the age and salinity of this type of ice significant variations about 0 11 in the minimum emissivity of consolidated multiyear ice are observed in different regions of the arctic using the high resolution 30 m passive microwave data this suggests that regional variations in texture and scattering characteristics of multiyear ice in the arctic are present likely influenced by different histories of formation of the ice in different regions

earth s free oscillations excited by the 26 december 2004 sumatra andaman earthquake at periods greater than 1000 seconds earth s seismic free oscillations have anomalously large amplitude when referenced to the harvard centroid moment tensor fault mechanism which is estimated from 300 to 500 second surface waves by using more realistic rupture models on a steeper fault derived from seismic body and surface waves we approximated free oscillation amplitudes with a seismic moment 6 5 10 22 newton meters that corresponds to a moment magnitude of 9 15 with a rupture duration of 600 seconds the fault rupture models represent seismic observations adequately but underpredict geodetic displacements that argue for slow fault motion beneath the nicobar and andaman islands

recovery from a large tsunami mapped over time the aceh coast sumatra this is a record of the rapid recovery of the aceh coast northwest sumatra after its destruction in the tsunami of 26 december 2004 using high resolution ikonos images and field visits we mapped the same 175 km of coastline at 1 m resolution five times 2003 before the tsunami 2004 and early 2005 immediately after the tsunami 2006 2007 and 2008 the aceh coast was eroded back for about 500 m in the tsunami except at the rocky headlands and almost the entire suite of depositional landforms of beaches low sand dunes and wetlands were removed a new coast started to appear within weeks closely resembling the pre tsunami version the new suite of depositional forms not only masked the erosional effect of the tsunami within a very brief period but also mimicked the old coast the post tsunami coast was subjected to the normal coastal processes and the new coast was formed within the constraints of the prevalent coastal environment thus resembling the old one the new beaches tend to be bigger than the old one although they have not yet reached their former seaward positions on this coast a tsunami appears to be an episodic destructive event at an interval of 500 years followed by a set of geomorphic processes that rapidly tend to remove or mask the evidence of such destruction the recovery is hindered where anthropogenic influences have modified the coastal forms and configuration we suggest that a the optimal management of coasts of this type after a tsunami is to leave it to nature and b sedimentary deposits are better indicators of past tsunamis than coastal morphology as demonstrated high resolution satellite images can be used not only for measuring changes caused by a high magnitude event but also for tracing the recovery over time this was impossible earlier except for very small areas which could be mapped on foot

on the use of lognormal statistics to simulate one and two dimensional under ice draft profiles the probability density function of one dimensional measurements of ice draft is shown to be fitted accurately by a set of lognormal distributions a technique is also described for generating synthetic ice draft data by interspersing filtered random number sequences drawn from the fitted lognormal distributions the sequences are interspersed by random selection to produce one and two dimensional model ice draft profiles the filter characteristics can be chosen so that one dimensional spectra of the model profiles agree well with measurements for features with horizontal length scales greater than 10 m realizations of ice draft data are in good visual agreement with measured profiles

titanium aluminum and interlayer cation substitutions in biotite from high grade gneisses west greenland detailed electron microprobe study pelitic to mafic metamorphic rocks from two localities higher ti k k na and possible k na similar al iv and lower al vi in granulite vs amphibolite grade samples modified journal abstract

tectonics and history of the andaman sea region abstract the andaman sea is an active backarc basin lying above and behind the sunda subduction zone where convergence between the overriding southeast asian plate and the subducting australian plate is highly oblique the effect of the oblique convergence has been formation of a sliver plate between the subduction zone and a complex right lateral fault system the late paleocene collision of greater india and asia with approximately normal convergence started clockwise rotation and bending of the northern and western sunda arc the initial sliver fault which probably started in the eocene extended through the outer arc ridge offshore from sumatra through the present region of the andaman sea into the sagaing fault with more oblique convergence due to the rotation the rate of strike slip motion increased and a series of extensional basins opened obliquely by the combination of backarc extension and the strike slip motion these basins in sequence are the mergui basin starting at 32 ma the conjoined alcock and sewell rises starting at 23 ma east basin separating the rises from the foot of the continental slope starting at 15 ma and finally at 4 ma the present plate edge was formed alcock and sewell rises were separated by formation of the central andaman basin and the faulting moved onshore from the mentawai fault to the sumatra fault system bisecting sumatra

excitation of 4 min periodic ionospheric variations following the great sumatra andaman earthquake in 2004 1 periodic variations of the ionosphere were detected by ground based gps total electron content tec measurements after the sumatra andaman earthquake in 2004 the observational data showed that the 4 min periodic tec variations occurred 1 h after the earthquake and continued for longer than 4 h at the phkt station about 30 cycles of the 4 min periodic tec variations were observed from 0230 to 0430 ut the maximum peak to peak amplitude of the variations was about 0 6 total electron content unit tecu 1 tecu 1016 el m 2 around 0320 ut the frequency of these periodic variations was 3 9 mhz they were detected by the samp station in the northern sumatra and the phkt and bnkk stations in thailand with the signal from seven gps satellites prn 8 11 13 19 23 27 and 31 they were observed in a limited area from 4 n to 15 n in latitude and from 96 e to 101 e in longitude although the western boundary was not certain because of the limit of the observational field of view the amplitude of these tec variations showed the dependence on the zenith angle of the path between the gps receiver and satellite the amplitude had a maximum when the zenith angle was the smallest this could be caused by the vertical structure of the electron density variations this also suggested that the electrons were oscillating along the geomagnetic field the 4 min periodic tec variations were interpreted to be induced by the long lasting free oscillation of the atmosphere set up by the earthquake their long duration also indicates that they were generated by a nontransient process like resonance

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

evidence for tidal triggering of earthquakes as revealed from statistical analysis of global data 1 we observe tidal triggering of earthquakes by measuring the correlation between the earth tide and earthquake occurrence we used the times locations and focal mechanisms of the 9350 globally distributed earthquakes with magnitude 5 5 or larger from the harvard centroid moment tensor catalog the tidal stress was theoretically computed by using the preliminary reference earth model and a recent ocean tide model nao 99b we considered the shear stress on the fault plane and the trace of stress tensor j1 defining the tidal phase angle at the occurrence time for each earthquake we statistically tested the phase selectivity using the schuster s method for all the earthquakes no significant correlation is found between the earth tide and earthquake occurrence both for the shear stress and for j1 by classifying the data set according to fault types however we find a high correlation with the shear stress for reverse fault type the correlation is particularly clear for shallow and smaller earthquakes of this type significant correlation with j1 also appears for larger earthquakes of reverse fault type and for shallow and larger ones of normal fault type we find no correlation for strike slip type for all the cases of high correlation earthquakes tend to occur when the tidal stress accelerates the fault slip indicating that high correlation is not coincidental but is physically justified this result strongly suggests that a small stress change due to the earth tide encourages earthquake occurrence when the stress in the future focal area is near a critical condition

plate boundary deformation associated with the great sumatra andaman earthquake the sumatra andaman earthquake of 26 december 2004 is the first giant earthquake moment magnitude m w 9 0 to have occurred since the advent of modern space based geodesy and broadband seismology it therefore provides an unprecedented opportunity to investigate the characteristics of one of these enormous and rare events here we report estimates of the ground displacement associated with this event using near field global positioning system gps surveys in northwestern sumatra combined with in situ and remote observations of the vertical motion of coral reefs these data show that the earthquake was generated by rupture of the sunda subduction megathrust over a distance of 1 500 kilometres and a width of 150 kilometres megathrust slip exceeded 20 metres offshore northern sumatra mostly at depths shallower than 30 kilometres comparison of the geodetically and seismically inferred slip distribution indicates that 30 per cent additional fault slip accrued in the 1 5 months following the 500 second long seismic rupture both seismic and aseismic slip before our re occupation of gps sites occurred on the shallow portion of the megathrust where the large aceh tsunami originated slip tapers off abruptly along strike beneath simeulue island at the southeastern edge of the rupture where the earthquake nucleated and where an m w 7 2 earthquake occurred in late 2002 this edge also abuts the northern limit of slip in the 28 march 2005 m w 8 7 nias simeulue earthquake

thin ice thickness from satellite thermal imagery sea ice thickness is an important parameter in the surface energy exchange and mass balance of the polar oceans remote sensing offers the opportunity to monitor thin ice routinely we combine measurements of surface temperature from an advanced very high resolution radiometer avhrr with a thermodynamic ice growth model to estimate thin ice and its thickness distribution during the cold season in a beaufort sea area of perennial ice we find that thin ice up to a meter thick had a concentration of 18 in december 1990 and 3 in april 1991 thin ice concentrations near the ice edge in the greenland sea range from 20 to 50 these avhrr derived estimates generally compare well with thickness observations from upward looking sonar given the uncertainties in all the model inputs estimated from avhrr such as radiative and turbulent heat flux components and surface albedo we find that ice thickness is estimated with an uncertainty of roughly 50 the uncertainty in the cumulative thickness distribution is about 3 for ice less than 20 cm thick and about 9 for ice around 1 m thick these magnitudes are significantly smaller than the variations in thin ice observed by satellite in different months and regions we conclude that avhrr is capable of resolving the regional and seasonal variations in thin ice to a level of accuracy useful both for establishing a climatology and for testing ice models

sea ice deformation state from synthetic aperture radar imagery part i comparison of c and l band and different polarization in this paper we present a quantitative comparison of l and c band airborne synthetic aperture radar imagery acquired at like and cross polarizations over deformed sea ice under winter conditions the parameters characterizing the deformation state of the ice are determined at both radar bands and at different polarizations the separation of deformed and level ice is based on a target detection technique the threshold is set such that image pixels with intensities equal to or larger than the highest 2 of the level ice intensity distribution are classified as deformed ice independent of the radar configuration and ice conditions optical imagery of sufficient quality for comparison is available only in a very few cases to characterize the deformation state the areal fraction of deformation features and the average distance between these features are evaluated the values obtained for both parameters are very sensitive to the radar frequency aeral fractions are larger and average distances are smaller at l band than at c band because of the much higher intensity contrast between the deformed and level ice at l band the differences between polarizations at one radar band are smaller but not always negligible in comparison to optical images it was observed that deformed ice areas can be distinguished from level ice over their whole length and extension at l band whereas at c band often only prominent parts are visible

deformation and slip along the sunda megathrust in the great 2005 nias simeulue earthquake seismic rupture produced spectacular tectonic deformation above a 400 kilometer strip of the sunda megathrust offshore northern sumatra in march 2005 measurements from coral microatolls and global positioning system stations reveal trench parallel belts of uplift up to 3 meters high on the outer arc islands above the rupture and a 1 meter deep subsidence trough farther from the trench surface deformation reflects more than 11 meters of fault slip under the islands and a pronounced lessening of slip trenchward a saddle in megathrust slip separates the northwestern edge of the 2005 rupture from the great 2004 sumatra andaman rupture the southeastern edge abuts a predominantly aseismic section of the megathrust near the equator

seafloor morphology of the sumatran subduction zone surface rupture during megathrust earthquakes high resolution multibeam bathymetry data from the sumatran subduction zone reveal the regional and local morphology including small scale fault related features and landslides that may be linked to earthquakes in the recent geological past the accretionary prism is steeply sloped and pervasively eroded with evidence of unusual landward vergence seaward fault dip of the frontal thrusts small scale 5 100 m height fault scarps folds and troughs are common along the seaward edge of the frontal thrust at the deformation front a model of back thrust fault slip or bending moment folding during plate boundary slip such as during the 2004 m9 2 megathrust earthquake can explain the position of these features on the seaward fold limb of a seaward dipping thrust we infer that in major sumatran and other similar settings plate boundary earthquakes coseismic surface rupture may occur at the prism toe

damage in step overs may enable large cascading earthquakes seismic hazard analysis relies on the ability to predict whether an earthquake will terminate at a fault tip or propagate onto adjacent faults cascading into a larger more devastating event while ruptures are expected to arrest at fault discontinuities larger than 4 5 km scientists are often puzzled by much larger rupture jumps here we show that material properties between faults significantly affect the ability to arrest propagating ruptures earthquake simulations accounting for fault step over zones weakened by accumulated damage provide new insights into rupture propagation revealing that lowered rigidity and material interfaces promote rupture propagation our models show for the first time that step overs as wide as 10 km may not constitute effective earthquake barriers our results call for re evaluation of seismic hazard analyses that predict rupture length and earthquake magnitude based on historic records and fault segmentation models

collision of the ganges brahmaputra delta with the burma arc implications for earthquake hazard abstract we take a fresh look at the topography structure and seismicity of the ganges brahmaputra delta gbd burma arc collision zone in order to reevaluate the nature of the accretionary prism and its seismic potential the gbd the world s largest delta has been built from sediments eroded from the himalayan collision these sediments prograded the continental margin of the indian subcontinent by 400 km forming a huge sediment pile that is now entering the burma arc subduction zone subduction of oceanic lithosphere with 20 km sediment thickness is fueling the growth of an active accretionary prism exposed on land the prism starts at an apex south of the gbd shelf edge at 18 n and widens northwards to form a broad triangle that may be up to 300 km wide at its northern limit the front of the prism is blind buried by the gbd sediments thus the deformation front extends 100 km west of the surface fold belt beneath the comilla tract which is uplifted by 3 4 m relative to the delta this accretionary prism has the lowest surface slope of any active subduction zone the gradient of the prism is only 0 1 rising to 0 5 in the forearc region to the east this low slope is consistent with the high level of overpressure found in the subsurface and indicates a very weak detachment since its onset the collision of the gbd and burma arc has expanded westward at 2 cm yr and propagated southwards at 5 cm yr seismic hazard in the gbd is largely unknown intermediate size earthquakes are associated with surface ruptures and fold growth in the external part of the prism however the possibility of large subduction ruptures has not been accounted for and may be higher than generally believed although sediment clogged systems are thought to not be able to sustain the stresses and strain weakening behavior required for great earthquakes some of the largest known earthquakes have occurred in heavily sedimented subduction zones a large earthquake in 1762 ruptured 250 km of the southern part of the gbd suggesting large earthquakes are possible there a large but poorly documented earthquake in 1548 damaged population centers at the northern and southern ends of the onshore prism and is the only known candidate for a rupture of the plate boundary along the subaerial part of the gbd burma arc collision zone

the global reach of the 26 december 2004 sumatra tsunami numerical model simulations combined with tide gauge and satellite altimetry data reveal that wave amplitudes directionality and global propagation patterns of the 26 december 2004 sumatra tsunami were primarily determined by the orientation and intensity of the offshore seismic line source and subsequently by the trapping effect of mid ocean ridge topographic waveguides

earthquake rupture stalled by a subducting fracture zone we showed that the rupture produced by the great peru earthquake moment magnitude 8 4 on 23 june 2001 propagated for 70 kilometers before encountering a 6000 square kilometer area of fault that acted as a barrier the rupture continued around this barrier which remained unbroken for 30 seconds and then began to break when the main rupture front was 200 kilometers from the epicenter the barrier had relatively low rupture speed slip and aftershock density as compared to its surroundings and the time of the main energy release in the earthquake coincided with the barrier s rupture we associate this barrier with a fracture zone feature on the subducting oceanic plate

uplift and subsidence associated with the great aceh andaman earthquake of 2004 rupture of the sunda megathrust on 26 december 2004 produced broad regions of uplift and subsidence we define the pivot line separating these regions as a first step in defining the lateral extent and the downdip limit of rupture during that great m w 9 2 earthquake in the region of the andaman and nicobar islands we rely exclusively on the interpretation of satellite imagery and a tidal model at the southern limit of the great rupture we rely principally on field measurements of emerged coral microatolls uplift extends from the middle of simeulue island sumatra at 2 5 n to preparis island myanmar burma at 14 9 n thus the rupture is 1600 km long the distance from the pivot line to the trench varies appreciably the northern and western andaman islands rose whereas the southern and eastern portion of the islands subsided the nicobar islands and the west coast of aceh province sumatra subsided tilt at the southern end of the rupture is steep the distance from 1 5 m of uplift to the pivot line is just 60 km our method of using satellite imagery to recognize changes in elevation relative to sea surface height and of using a tidal model to place quantitative bounds on coseismic uplift or subsidence is a novel approach that can be adapted to other forms of remote sensing and can be applied to other subduction zones in tropical regions

the 2004 sumatra earthquake and tsunami lessons learned in subduction zone science and emergency management for the cascadia subduction zone the 26 december 2004 mw 9 3 sumatra earthquake and tsunami was a pivotal turning point in our awareness of the dangers posed by subduction zone earthquakes and tsunamis this earthquake was the world s largest in 40 years and it produced the world s deadliest tsunami this earthquake ruptured a subduction zone that has many similarities to the cascadia subduction zone in this article i summarize lessons learned from this tragedy and make comparisons with potential rupture characteristics slip distribution deformation patterns and aftershock patterns for cascadia using theoretical modeling and interseismic observations both subduction zones are approximately 1 100 1 300 km in length both have similar convergence rates and represent oblique subduction slip along the subduction fault during the 26 december earthquake is estimated at 15 25 m similar to values estimated for cascadia the width of the rupture 80 150 km estimated from modeling seismic and geodetic data is similar to the width of the locked and transition zone estimated for cascadia coseismic subsidence of up to 2 m along the sumatra coast is also similar to that predicted for parts of northern cascadia based on paleoseismic evidence in addition to scientific lessons learned the 2004 tsunami provided many critical lessons for emergency management and preparedness as a result of that tragedy a number of preparedness initiatives are now underway to promote awareness of earthquake and tsunami hazards along the west coast of north america and plans are underway to develop prototype tsunami and earthquake warning systems along cascadia lessons learned from the great sumatra earthquake and tsunami tragedy both through scientific studies and through public education initiatives will help to reduce losses during future earthquakes in cascadia and other subduction zones of the world

kinematics and source zone properties of the 2004 sumatra andaman earthquake and tsunami nonlinear joint inversion of tide gauge satellite altimetry and gps data 1 we re analyzed the source of the 26 december 2004 sumatra andaman earthquake and tsunami through a nonlinear joint inversion of an inhomogeneous data set made up of tide gauges satellite altimetry and far field gps recordings the purpose is twofold 1 the retrieval of the main kinematics rupture parameters slip rake and rupture velocity and 2 the inference of the rigidity of the source zone we independently estimate the slip from tsunami data and the seismic moment from geodetic data to derive the rigidity our results confirm that the source of the 2004 sumatra andaman earthquake has a complex geometry constituted by three main slip patches with slip peaking at 30 m in the southern part of the source the rake direction rotates counterclockwise at the northern part of the source according to the direction of convergence along the trench the rupture velocity is higher in the deeper than in the shallower part of the source consistent with the expected increase of rigidity with depth it is also lower in the northern part consistent with known variations of the incoming plate properties and shear velocity our model features a rigidity 20 30 gpa that is lower than the preliminary reference earth model prem average for the seismogenic volume the source rigidity is one of the factors controlling the tsunami genesis for a given seismic moment the lower the rigidity the higher the induced seafloor displacement the general consistence between our source model and previous studies supports the effectiveness of our approach to the joint inversion of geodetic and tsunami data for the rigidity estimation

diagenetic and low grade metamorphic terranes of gaspe peninsula related to the geological structure of the taconian and acadian orogenic belts quebec appalachians illite crystallinity ic measurements determination of the proportion of 2m mica polytypes and organic matter reflectance measurements establish regional diagenetic low grade metamorphic trends for the taconian and acadian belts of gaspe peninsula ic varies as a function of many factors besides maximum burial temperature and heating time correlation between ic and 2m illite polytypes for the fortin group and temiscouata formation suggests i that the amount of high grade detrital mica in the samples is low and ii that ic can be used with some confidence as an estimator of regional thermal maturation levels correlation of these parameters with available organic reflectance values further supports this assumption the illites of the temiscouata and western fortin groups are mostly phengitic in composition whereas in the eastern outcrop belt they are more mg and fe rich celadonitic but generally also of lower grade and lower 2m content the d 060 values for illites measured on the unorientated 2 m fraction of samples fall between 1 502 and 1 503 a range 1 500 1 504 a indicating relatively low octahedral occupancy by mg and fe between one fifth and one third of the available spaces pyrophyllite and paragonite were not detected chlorites are fe rich and ripidolitic the ic map for the acadian belt of the peninsula displays general congruence between ic contours 2200 sample points and structural trends for the 27 000 km2 area the highest grades anchimetamorphic are associated with the oldest rocks honorat and matapedia groups exposed in the cores of major anticlines anchimetamorphic grades associated with the western outcrop belt of the lower devonian fortin group require 7 8 km of subsidence to accommodate sufficient thickness of overlying younger rocks on top of 4 5 km of fortin group deep water clastics to explain the grades in terms of burial metamorphism assuming a geothermal gradient of 30 c km 1 the lowest grade diagenetic rocks occupy a large area in the northeastern part of the peninsula smaller areas in the northwestern part of the acadian belt in the centre of chaleurs bay synclinorium and in the ordovician mictaw group the contact between the taconian and acadian belt is marked by a distinct maturation discontinuity the grand pabos fault juxtaposes rocks of contrasting maturation levels matapedia group against fortin group in the west but shows no maturation offset further east in the honorat group the fault zone limiting the fortin group in the north is also associated with a major ic jump

aftershock investigation in the andaman nicobar islands of india and its seismotectonic implications six three component short period digital seismograph four reftek and two kinemetrics stations were established in different parts of the andaman nicobar islands following the 26 december 2004 devastating sumatra andaman mainshock m w 9 3 here we analyze about 18 000 aftershocks m 3 0 recorded from 6 january to 16 march 2005 to better understand the seismotectonics of the region a sudden burst of aftershock activity with irregular trend in the month of january 2005 was observed at almost all seismograph stations the estimate of p value 0 9532 from aftershocks m 4 5 is near to normal value of 1 0 which suggests a slow decay sequence of aftershock with complex and nonuniform stress change in a fault system creep effects and history dependent stress changes the frequency magnitude relation of the aftershocks followed the power law with average b value of 0 7723 and it varies from 0 49 to 1 03 indicating the compressive stress state of the region and its heterogeneous structure with possible variations in frictional conditions along the fault the distribution of the located aftershocks by a multistation method shows a north south trending aftershock cluster in an area of about 800 300 km 2 which reflects an approximate rupture dimension of the mainshock beneath the andaman nicobar islands most of aftershocks occurred in a depth range of 5 65 km the determination of composite fault plane solutions of the best located aftershock clusters at three different depth ranges 0 15 16 30 and 31 km in the ten blocks of the region suggests that the mainshock rupture propagated through normal reverse and strike slip earthquakes the areas in the vicinity of barren and narcondum volcanic zones show a dominantly normal fault mechanism due to predominant tensional forces suggesting the facilitation of brittle failure in the weakened crust by the process of underheating the zone near baratang mud volcano is associated predominantly with thrust fault at depth of 0 30 km suggesting a high compressive force beneath the baratang that ejected a huge amount of mud and slurry materials to the surface after the 26 december 2004 sumatra andaman earthquake m w 9 3 here we propose that the relocation of our large aftershock dataset using converted sp depth phase technique for precise depth control is needed and its sharing with global earthquake data can render more information on the subduction dynamics and geodynamical processes of the region

tidal synchronicity of the 26 december 2004 sumatran earthquake and its aftershocks 1 the frequency of earthquake incidence along the andaman sunda java trench plate boundary region has been investigated for the ten lunar month period 28 october 2004 19 august 2005 encompassing the 26 december 2004 earthquake during this period variations in earthquake activity correlate with the tidal force cycles maxima in earthquake activity occur around the times of new and full moons typically lagging by 0 3 days this relationship is consistent with earthquake inducement via ocean tidal loading also during this period the earthquake incidence associated with new and full moons at the western end of the region was a 38 and b 86 higher than the period averages for the full and declustered major earthquake catalogs respectively

the fortnightly tide and the tidal triggering of earthquakes in this paper we test the southern california network earthquake catalog and the world wide earthquake catalog for a fortnightly tidal periodicity and find none in studies that test the hypothesis of tidal triggering of earthquakes it is usually necessary to resolve the tidal shear stress onto the plane of the fault and in the direction of the slip vector to determine if the stress is compatible with the fault motion heaton 1975 1982 this analysis requires accurate focal mechanisms and knowledge of the focal plane on which slip occurred for as many earthquakes as possible to improve the statistical sampling of the data set however if we consider the fortnightly tide which is a simple amplitude modulation focal mechanism information is not required our analysis assumes that we have a large data base of earthquakes with varying mechanisms the alignment of the slip vector with the tidal shear stress will vary from earthquake to earthquake however if tidal triggering of earthquakes does occur more earthquakes should be triggered out of the total population when the tidal stress is large than when it is small if the largest semi diurnal tide is normalized to an amplitude of 1 0 the fortnightly tide would have an amplitude of 0 17 on this scale and a period of about 2 weeks munk and macdonald 1960 therefore the effect on the occurrence of earthquakes by the tidal shear stress will be modulated with a 2 week period considering the fortnightly tide allows us to utilize entire catalogs of data to test the tidal triggering hypothesis without knowledge of the focal mechanisms

the size and duration of the sumatra andaman earthquake from far field static offsets the 26 december 2004 sumatra earthquake produced static offsets at continuously operating gps stations at distances of up to 4500 kilometers from the epicenter we used these displacements to model the earthquake and include consideration of the earth s shape and depth varying rigidity the results imply that the average slip was 5 meters along the full length of the rupture including the approximately 650 kilometer long andaman segment comparison of the source derived from the far field static offsets with seismically derived estimates suggests that 25 to 35 of the total moment release occurred at periods greater than 1 hour taking into consideration the strong dip dependence of moment estimates the magnitude of the earthquake did not exceed mw 9 2

characterizing winter landfast sea ice surface roughness in the canadian arctic archipelago using sentinel 1 synthetic aperture radar and the multi angle imaging spectroradiometer

a flying start then a slow slip the human tragedy caused by the sumatra andaman earthquake moment magnitude 9 3 on 26 december 2004 and its companion nias earthquake moment magnitude 8 7 on 28 march 2005 is difficult to comprehend these earthquakes the largest in 40 years have also left seismologists searching for the words and tools to describe the enormity of the geological processes involved four papers in this issue discuss aspects of a rupture process of surprising complexity the first such event to test the sensitivity and range of many new technologies a surprising feature of the earthquake is that after the initial rapid rupture subsequent slip of the plate interface occurred with decreasing speed toward the north

reduced ice thickness in arctic transpolar drift favors rapid ice retreat 1 helicopter borne electromagnetic sea ice thickness measurements were performed over the transpolar drift in late summers of 2001 2004 and 2007 continuing ground based measurements since 1991 these show an ongoing reduction of modal and mean ice thicknesses in the region of the north pole of up to 53 and 44 respectively since 2001 a buoy derived ice age model showed that the thinning was mainly due to a regime shift from predominantly multi and second year ice in earlier years to first year ice in 2007 which had modal and mean summer thicknesses of 0 9 and 1 27 m measurements of second year ice which still persisted at the north pole in april 2007 indicate a reduction of late summer second year modal and mean ice thicknesses since 2001 of 20 and 25 to 1 65 and 1 81 m respectively the regime shift to younger and thinner ice could soon result in an ice free north pole during summer