characteristic reflection patterns in the southeast canadian cordillera northern appalachians and swiss alps abstract there are some striking similarities and some differences between the seismic reflection sections recorded across the fold and thrust belts of the southeast canadian cordillera quebec maine appalachians and swiss alps in the fold and thrust belts of all three mountain ranges seismic reflection surveys have yielded high quality images of 1 nappes thin thrust sheets stacked on top of ancient continental margins 2 ramp anticlines in the hanging walls of faults that have ramp flat or listric geometries 3 back thrusts and back folds that developed during the terminal phases of orogeny and 4 tectonic wedges and regional decollements a principal result of the cordilleran and appalachian deep crustal studies has been the recognition of master decollements along which continental margin strata have been transported long distances whereas a principal result of the swiss alpine deep crustal program has been the identification of the adriatic indenter a crustal scale wedge that caused delamination of the european lithosphere significant crustal roots are observed beneath the fold and thrust belts of the alps southeast canadian cordillera and parts of the southern appalachians but such structures beneath the northern appalachians have probably been removed by post orogenic collapse and or crustal attenuation associated with the mesozoic opening of the atlantic ocean

relict non glacial surfaces in formerly glaciated landscapes abstract relict non glacial surfaces occur within many formerly glaciated landscapes and contain important information on past surface processes and long term landscape evolution relict non glacial surfaces are distinguishable from glacial surfaces by large scale morphologies including rounded summits fluvial valleys and cryoplanation terraces and pediments and the presence of tors blockfields and or saprolites preservation during glaciation occurs either through coverage by non erosive cold based ice or as nunataks although surface morphologies and denudation rates indicate a continuous non glacial surface history since preglacial times relict non glacial surfaces are dynamic features that have evolved during the quaternary depending on spatial variables such as lithology slope regolith depth and the abundance of fine matrix and water some surfaces are denuding very slowly while others display more rapid denudation high spatial variability in denudation rates results in changing surface morphologies over time denudation rates also display high temporal variability with much surface evolution having perhaps occurred soon after the initial onset of glaciation or during paraglacial phases while some parts of non glacial landscapes are currently active others may be largely inactive relicts of past higher energy regimes although non glacial surfaces are dynamic much remains to be determined regarding surface denudation rates and the magnitude of morphological changes over time

bedforms of the keewatin ice sheet canada abstract by compiling glacial bedforms on a map that covers most of one sector of the laurentide ice sheet it is possible to make some suggestions about their genesis based largely on spatial relationships it can be concluded that drumlins and ribbed moraine form at the base of actively flowing ice under similar dynamic conditions for either landform to exist however there must have been enough sediment available in the base of the glacier to leave or form a feature large enough to be recognizable the presence or absence of sufficient load is related to the geology of the glacier bed and has little to do with regionally changing dynamics of the ice water system likewise given sufficient load it is evident that whether drumlins formed or whether ribbed moraine formed in a certain area is a function of the physical nature of the load which is again related to geology of the source outcrops whether the physical characteristics come into play after the sediment has been released from the ice and is being reshaped by basal drag streamlining etc or whether the nature of the load while entrained changes the behaviour of the basal part of the ice is unclear physical characteristics of the basal sediment load have apparently promoted internal thrusting of coherent slabs of entrained debris and ice to form ribbed moraine on melting whereas drumlins may reflect moulding of plastic subglacial debris or erosional streamlining of both the unconsolidated glacial substrate and bedrock the observation that many eskers cross drumlin fields at nearly right angles to their orientation suggests that conditions producing streamlining and those pertaining to subglacial drainage are separated in time and circumstance the general occurrence of drumlins and eskers throughout the sediment rich portions of the keewatin ice sheet from zone 1 to its edge is difficult to reconcile with the restriction and intimate association of these forms with ribbed moraine almost exclusively in zone 2 because such a zonal relationship exists to some extent around other ice divides at least in labrador nouveau quebec and newfoundland it seems that some condition changed or existed in this zone throughout or at some specific time during the existence of the keewatin ice sheet possibly around the last ice divides reactivation of the ice sheet by alimentation associated with climatic deterioration may have promoted flow of thin brittle ice this may have shattered the glacier forming stacked thrust plates of ice and debris with subsequent stagnation the thrust plates may have melted out without substantial deformation

global crustal stress pattern based on the world stress map database release 2008 the world stress map wsm project is a global compilation of information on the contemporary crustal stress field from a wide range of stress indicators the wsm database release 2008 contains 21 750 stress data records that are quality ranked using an updated and refined quality ranking scheme almost 17 000 of these data records have a c quality and are considered to record the orientation of maximum horizontal compressional stress sh to within 25 as this is almost a triplication of data records compared with the first wsm database release in 1992 we reinvestigate the spatial wave length of the stress patterns with a statistical analysis on a global 0 5 grid the resulting smoothed global stress map displays both the mean sh orientation that follows from the maximum smoothing radius for which the standard deviation is b25 and a countour map that displays the wave length of the stress pattern this smoothed global map confirms that long wave length stress patterns n2000 km exist for example in north america and ne asia these have been used in earlier analyses to conclude that the global stress pattern is primarily controlled by plate boundary forces that are transmitted into the intraplate region however our analysis reveals that rather short wave length of the stress pattern b200 km are quite frequent too particularly in western europe alaska and the aleutians the southern rocky mountains basin and range province scandinavia caucasus most of the himalayas and indonesia this implies that local stress sources such as density contrasts and active fault systems in some areas have high impact in comparison to plate boundary forces and control the regional stress pattern

the sensitivity of subglacial bedform size and distribution to substrate lithological control the varied nature of a glacial substrate has often been invoked to account for the varied distribution arrangement and morphological expression of subglacial bedforms the ease and rate of sediment production from the bedrock substrate and the rheological mechanical and hydraulic properties of the resultant subglacial sediment layer have been argued in certain samples or settings to account for the local to regional distribution of bedforms and bedform types and varying morphological expression such as size shape elongation or spatial arrangement from locally coherent observations and relationships it is tempting to extrapolate such patterns to express a more fundamental lithological control on subglacial bedform properties and formation here we use a large systematically compiled dataset 30 000 subglacial bedforms inscribed by the irish ice sheet to explore potential lithological controls upon subglacial bedform distribution and morphological expression we expect any lithological control upon form size or distribution to be expressed through a spatial correlation between bedform properties and those of the bed lithology we extract bedform morphometric and distribution statistics and underlying lithology data from datasets held in a geographic information system for comparative analyses at ice sheet scale i e considering our whole bedform population we find no apparent relationship between the lithology of either bedrock or till substrate and bedform occurrence density of arrangement or size regional to local examples do in contrast exhibit some coincident changes in substrate and bedform expression these are typically manifest as an abrupt shortening or lengthening of drumlins at a lithological boundary superimposed upon more gradual regional trends however not all local variability observed in the bedform population can be attributed to a lithological driver and where it can be inferred lithological control is often in tandem with or subordinate to other drivers such as topographic setting or ice dynamics we propose a hierarchy of controls upon bedform form and distribution strongly coupled to spatial scale lithological differences can modulate local scale form and expression but bedform incidence and properties are primarily governed by ice sheet scale glaciological patterns and drivers only under certain unknown conditions at a local scale is the bedforming process sensitive to the lithological properties of the bed

sedimentary anisotropy diverges from flute trends in south east finnish lapland abstract subglacial flutes are parallel to ice flow lineations indicative of glacial streamlining yet their depositional erosional origin or sedimentary anisotropy is not fully understood the flutes aligned nw se with a flow direction to the se are superimposed on westerly oriented drumlins in kuusamo south eastern finnish lapland 65 45 n and 29 40 e and reflect ice stream flow pattern towards the younger dryas end moraines ydems in russian karelia we investigated bedform morphology flutes drumlins and crescentic troughs as well as sedimentary anisotropy of flute ridges and troughs using digital elevation models dems airborne radiometric ar data and measurements of azimuthal electrical conductivity a the dem ar revealed elongation ratios l w from 2 1 to 25 1 yet the highest ratios reached l w 48 1 flutes in the study area fan towards the east and south east whereas the drumlins on which they are superimposed show ice flow from the west 280 the a anisotropy of the flute ridges and troughs indicates sedimentation from 340 to 350 diagonal with respect to both drumlins and flutes we found erosional crescentic troughs with down flow rims indicative of both phases but failed to find evidence for subglacial meltwater boulder lags or ice flow erosional bedrock bump sticky spots we contend that the studied flutes are erosional and date to the ydem phase yet the origin of the precursory sediments may date to early weichselian

moment tensor solutions for small and moderate earthquakes in the ibero maghreb region 1 we applied time domain moment tensor inversion of local and regional waveforms to small and moderate mw 3 5 5 7 shallow earthquakes from the iberian peninsula northern morocco and northern algeria for the 6 years period from november 1995 to march 2002 and the previous network of autonomously recording seismograms nars experiment moment tensor solutions were obtained for 58 events considerably increasing the total number of available solutions in the study area for each event we performed a moment tensor inversion and a double couple grid search for simple faulting events the grid search is valuable as a quality test for its ability to reveal potential ambiguities of the solutions and to assess confidence limits of fault plane parameters or principal axes orientation the computed mechanisms show regional consistency a large part of the iberian peninsula is characterized by normal faulting mechanisms with sw ne oriented t axes thrusting and se nw compression is dominant in algeria in the alboran sea the westernmost part of the mediterranean and the transition between both regimes strike slip mechanisms dominate with approximately n s oriented p axes this pattern suggests a regional anomaly characterized by clockwise rotation of the principal horizontal stress orientations

deep lower crustal earthquakes in central india inferences from analysis of regional broadband data of the 1997 may 21 jabalpur earthquake summary the only instance of a confirmed deep lower crustal earthquake occurrence in the indian shield region has been that of the 1938 satpura earthquake m 6 3 of central india reportedly at a depth of about 40 km moment tensor inversion of regional broadband waveform data of the 1997 may 21 jabalpur earthquake mw 5 7 confirms yet another such earthquake at about 35 km depth in the central part of the narmada son lineament nsl zone the study is based on a refined velocity model obtained using a traveltime grid search method a reverse fault mechanism is obtained which for a palaeo rift valley zone indicates the possibility of reactivation of a pre existing fault under the influence of the ambient stress field due to the india eurasia plate collision forces the occurrence of earthquakes at lower crustal depths quite unusual for the indian shield region indicates a possible causative mechanism related to crust mantle interaction based on the close proximity of the two deep earthquakes and their disposition with respect to the local trend of the central part of the nsl we suggest a model of stress accumulation due to horizontally elongated or elliptical possibly serpentinized mafic intrusives in the lower crust to explain the occurrence of deep earthquakes in the heart of the indian shield

regional and local ice flow history in the vicinity of the izok lake zn cu pb ag deposit nunavut ice directional indicators were compiled from detailed field mapping at the izok lake volcanogenic massive sulphide deposit in the point lake region of western nunavut and eastern northwest territories cross cutting erosional relationships and depositional landforms indicate that the izok lake area was affected by four ice flow phases it is this new glacial history interpretation that is used to explain the gahnite indicator mineral dispersal train down ice of the izok lake deposit as being the net effect of all ice flow phases its fan shaped morphology is a function of the duration and intensity of two dominant glacial trajectories field based mapping of all glacial flow indicators are essential and must be properly interpreted to detect palimpsest dispersal trains the resultant dispersal fan serves as a model for future exploration in the glaciated terrain of the north central part of the slave province

theoretical contemporary observational and palaeo perspectives on ice sheet hydrology processes and products publisher elsevier articletitle theoretical contemporary observational and palaeo perspectives on ice sheet hydrology processes and products journaltitle earth science reviews articlelink http dx doi org 10 1016 j earscirev 2016 01 010 content type article copyright copyright 2016 elsevier b v all rights reserved

global seismicity of 2002 centroid moment tensor solutions for 1034 earthquakes abstract centroid moment tensor solutions are presented for 1034 earthquakes that occurred during 2002 the solutions are obtained using the method of dziewonski et al dziewonski a m chou t a woodhouse j h 1981 determination of earthquake source parameters from waveform data for studies of global and regional seismicity j geophys res 86 2825 2852 and applying corrections for aspherical earth structure represented by the whole mantle shear velocity model sh8 u4l8 of dziewonski and woodward dziewonski a m woodward r l acoustic imaging at the planetary scale in emert h harjes h p eds acoustical imaging vol 19 plenum press new york 1992 pp 785 797 the model of anelastic attenuation of durek and ekstrom durek j j ekstrom g 1996 a radial model of anelasticity consistent with long period surface wave attenuation bull seism soc am 86 144 158 is used to predict the decay of the waveforms the focal mechanisms of the largest or otherwise significant earthquakes of 2002 are reviewed

evolution of late glacial ice marginal lakes on the northwestern canadian shield and their influence on the location of the dubawnt lake palaeo ice stream abstract during deglaciation of the north american laurentide ice sheet large proglacial lakes developed in positions where proglacial drainage was impeded by the ice margin for some of these lakes it is known that subsequent drainage had an abrupt and widespread impact on north atlantic ocean circulation and climate but less is known about the impact that the lakes exerted on ice sheet dynamics this paper reports palaeogeographic reconstructions of the evolution of proglacial lakes during deglaciation across the northwestern canadian shield covering an area in excess of 1 000 000 km2 as the ice sheet retreated some 600 km the interactions between proglacial lakes and ice sheet flow are explored with a particular emphasis on whether the disposition of lakes may have influenced the location of the dubawnt lake ice stream this ice stream falls outside the existing paradigm for ice streams in the laurentide ice sheet because it did not operate over fined grained till or lie in a topographic trough ice margin positions and a digital elevation model are utilised to predict the geometry and depth of proglacial lakes impounded at the margin at 30 km increments during deglaciation palaeogeographic reconstructions match well with previous independent estimates of lake coverage inferred from field evidence and results suggest that the development of a deep lake in the thelon drainage basin may have been influential in initiating the ice stream by inducing calving drawing down ice and triggering fast ice flow this is the only location alongside this sector of the ice sheet where large 3000 km2 deep lakes 120 m are impounded for a significant length of time and exactly matches the location of the ice stream it is speculated that the commencement of calving at the ice sheet margin may have taken the system beyond a threshold and was sufficient to trigger rapid motion but that once initiated calving processes and losses were insignificant to the functioning of the ice stream it is thus concluded that proglacial lakes are likely to have been an important control on ice sheet dynamics during deglaciation of the laurentide ice sheet

subglacial bedform geomorphology of the irish ice sheet reveals major configuration changes during growth and decay the belated realisation that ribbed rogen moraines form such an integral part of irish geomorphology and the piecemeal approach to previous drumlin mapping is probably responsible for the highly contrasting views of palaeoflow patterns of the irish ice sheet using a high resolution 25 m digital elevation model we present morphological maps of a large part 100 100 km of the so called drumlin belt of north central ireland the landforms comprise mostly ribbed moraine much larger than found elsewhere up to 16 km in length which in places are superimposed on each other contrary to most prior assessments we find the bedform record to contain numerous and overlapping episodes of bed formation ribbed moraine drumlins and crag and tails that provide a palimpsest record of changing flow geometries these demonstrate an ice sheet with a centre of mass and flow geometry that changed during growth and decay using distinctive flow patterns and relative age relationships between them we reconstruct ice sheet evolution into four phases during a single glacial cycle in phase 1 early in the glacial cycle scottish and local ice coalesced to form a northeast centred irish ice sheet as it grew its centre of mass migrated southwards culminating in a major n s divide positioned down the east of ireland phase 2 ca last glacial maximum during retreat the centre of mass migrated at least 120 km northwards and became established in northwest ireland and at this point a dramatic bedforming event produced one of the world s largest and most contiguous ribbed moraine fields phase 3 final deglaciation is thought to be by fragmentation into many topographically controlled minor ice caps phase 4 rather than any dramatic or unexpected behaviour the reconstructed phases indicate a relatively predictable pattern of ice sheet growth and decay with changes in centres of mass and does not require major readvances or ice stream events copyright 2001 john wiley sons ltd

the composition and internal structure of drumlins complexity commonality and implications for a unifying theory of their formation investigation of drumlins is significant to both glaciology and palaeoglaciology but the sheer diversity of their composition and internal structure is often cited as a major obstacle towards a satisfactory unifying explanation of their formation this paper presents the first systematic survey of the vast literature on this subject with the aim of concisely summarising observations and identifying any emergent patterns or commonality that theories of drumlin formation should be able to explain results confirm that investigations are often limited by availability of suitable sediment exposures 40 of studies report data from 5 drumlins and 44 do not specify sample size although borehole data and geophysical techniques can alleviate this problem however it is clear that the constituents of drumlins are incredibly diverse in terms of their composition e g a range of lithologies clast shapes sizes and fabrics structure e g sediments that are sorted homogeneous surface conformable unconformable and evidence of deformation e g ranging from pervasive to non pervasive limited to absent despite this diversity our review leads us to suggest that drumlin composition can be simplified to five basic types i mainly bedrock ii part bedrock part till iii mainly till iv part till part sorted sediments and v mainly sorted sediments this is a potentially significant step in that it reduces the oft cited complexity of drumlin composition and provides a more realistic goal for theories or numerical models of drumlin formation to target the various types can occur within the same drumlin field which leaves us with two possible implications for drumlin formation 1 different types of drumlin are formed seeded by different processes despite being morphologically similar equifinality investigation of drumlin composition may therefore reveal diagnostic processes explanations for these different types of drumlin and we argue that bedrock drumlins are an example 2 a single process occurs across large parts of the ice bed interface to create drumlinised terrain in a variety of sediments investigation of drumlin composition may in this case simply reflect pre existing sediments but importantly the way in which the drumlin forming mechanism modifies is modified by them we argue that the latter simpler explanation applies to all other types of drumlin excluding purely bedrock forms and conclude that the diversity in drumlin composition is no obstacle to a single unifying theory

first geomorphological record and glacial history of an inter ice stream ridge on the west antarctic continental shelf inter ice stream areas cover significant portions of antarctica s formerly glaciated shelves but have been largely neglected in past geological studies because of overprinting by iceberg scours here we present results of the first detailed survey of an inter ice stream ridge from the west antarctic continental shelf well preserved sub and proglacial bedforms on the seafloor of the ridge in the eastern amundsen sea embayment ase provide new insights into the flow dynamics of this sector of the west antarctic ice sheet wais during the last glacial cycle multibeam swath bathymetry and parasound acoustic sub bottom profiler data acquired across a mid shelf bank between the troughs of the pine island thwaites pitpis and cosgrove palaeo ice streams copis reveal large scale ribbed moraines hill hole pairs terminal moraines and crevasse squeeze ridges together these features form an assemblage of landforms that is entirely different from that in the adjacent ice stream troughs and appears to be unique in the context of previous studies of antarctic seafloor geomorphology from this assemblage the history of ice flow and retreat from the inter ice stream ridge is reconstructed the bedforms indicate that ice flow was significantly slower on the inter ice stream ridge than in the neighbouring troughs while terminal moraines record at least two re advances or stillstands of the ice sheet during deglaciation an extensive field of crevasse squeeze ridges indicates ice stagnation subsequent to re advancing ice which deposited the field of terminal moraines in the ne the presented data suggest that the ice flow behaviour on the inter ice stream ridge was substantially different from that in the adjacent troughs however newly obtained radiocarbon ages on two sediment cores recovered from the inter ice stream ridge suggest a similar timing in the deglaciation of both areas this information closes an important gap in the understanding of past wais behaviour in the eastern ase our newly documented bedforms will also serve as an important diagnostic tool in future studies for interpreting ice sheet histories in similar inter ice stream areas

formation of mega scale glacial lineations on the dubawnt lake ice stream bed 2 sedimentology and stratigraphy mega scale glacial lineations msgls are highly elongate subglacial landforms produced beneath zones of fast flowing ice while qualitative data on their morphology have existed for several decades studies of their composition and sedimentology are comparatively rare sediment exposures along the course of the finnie river in nunavut northern canada provide a window into the internal stratigraphy and sedimentology of msgls formed by the dubawnt lake palaeo ice stream during regional deglaciation of the laurentide ice sheet stratigraphic sections record evidence for an initial advance of ice into the study area followed by ice sheet recession and deposition of glacifluvial and glacilacustrine outwash subsequently the dubawnt lake palaeo ice stream overrode and reworked this outwash subglacially forming an msgl till this till comprises a sandy red diamicton facies forming the core of the msgl ridges and containing variably deformed lenses stringers and rafts of outwash the sedimentology of this diamicton is consistent with an origin as a glacitectonite and hybrid till formed by a combination of non pervasive subglacial sediment deformation and lodgement facies variations from stratified to massive diamicton reflect in turn variations in strain and subglacial transport distance the occurrence of stratified glacifluvial sediments within these ridges and the well preserved nature of many of the sandy inclusions within the diamicton imply relatively short transport distances and incomplete mixing msgls under the dubawnt lake palaeo ice stream formed through a combination of subglacial erosion and deposition this included non pervasive subglacial sediment deformation and the reworking of pre existing sediment depocentres during streaming flow these results highlight the importance of sediment supply to msgl formation with the presence of abundant pre existing sediments which were subsequently overridden being critical to lineation formation

latest pleistocene advance and collapse of the matanuska knik glacier system anchorage lowland southern alaska abstract at the end of the last ice age glacier systems worldwide underwent dramatic retreat here we document the advance and retreat of a glacier system with adjacent marine and land based components during the latter part of the termination we utilize three lines of evidence lithologic provenance geomorphic mapping and radiocarbon ages derived from lake cores to reconstruct glacier extent and timing of advance and retreat within our study area centered at n 61 50 w 149 50 just north of anchorage alaska two glaciers sourced in the talkeetna and chugach mountains flowed down the matanuska and knik valleys forming a coalesced lobe that advanced onto the anchorage lowlands and terminated at elmendorf moraine we use the presence of lithologies unique to the matanuska catchment in glacial drift to delineate the paleoflow lines and to estimate the suture line of the two glacier systems the eastern side of the lobe attributed to ice flow from the knik valley was in contact with elevated marine waters within the knik arm fjord and thus retreat was likely dominated by calving geomorphic evidence suggests the western side of the lobe attributed to ice flow from matanuska valley retreated due to stagnation we constrain retreat of the combined matanuska and knik lobe with thirteen new radiocarbon ages in addition to previously published radiocarbon ages and with geomorphic evidence suggesting the retreat occurred in two phases retreat from the elmendorf moraine began between 16 8 and 16 4 ka bp a second faster retreat phase occurred later and was completed by 13 7 ka bp with the 140 km of total retreat occurring over 3000 years or less this pattern of glacial advance and retreats agrees well with the deglacial histories from the southern sectors of the cordilleran ice sheet as well as many other alpine glacier systems in the western u s and northern alaska this consistent behavior of glacier systems may indicate that climate oscillated over western north america early in deglaciation before it was recorded in other proxies such as ice cores furthermore the period in which we note mountain glacier collapse in northwestern north america is synchronous with the worldwide glacial termination raising questions about intrahemispheric linkages

ribbed moraines in northern manitoba canada characteristics and preservation as part of a subglacial bed mosaic near the core regions of ice sheets abstract ribbed moraines are enigmatic glacial landforms for which different models with contrasting paleoglaciologic implications have been proposed to explain their formation despite the great deal of attention this type of landform has received over the last several decades ribbed moraine fields in northern manitoba canada are among the largest in the world but have been seldom studied ribbed moraines in this part of the world overlie the low relief canadian shield are not constrained by topography and are part of a spatial subglacial landform assemblage associated with drumlinoid ridges within palimpsest and relict type glacial terrain zones field observations herein provide new insights into the characteristics of these transverse to ice flow ridges at landscape mapping and spatial analysis and landform internal structure using high resolution shear wave s wave seismic reflection surveys sedimentological characteristics clast fabric analyses scales two main types of ribbed moraine are recognized pristine high amplitude straight crested ridges and secondarily modified subdued drumlinized ridges ribbed moraine in northeast manitoba consist of massive matrix supported till at surface which is similar in matrix texture and composition to the regional till sheet though pristine moraines show a higher concentration of boulders a seismic profile reveals subparallel to surface layered stratigraphy with only minor folding and no major unconformities stacking or faulting the demonstrated fragmentary nature of ribbed moraine fields the inherited signature of the till within these fields the secondary patchy drumlinization of the ridges and the more abundant granitoid outcrops in areas of intense modification all suggest that subglacial ribbed moraine formed from pre existing sediments and were later preserved and or partially reworked through a regional mosaic of shifting subglacial bed conditions we therefore make the case that pristine unmodified moraines were preserved beneath stable sticky spots we support a link between ribbed moraine and widespread cold based and or dewatered subglacial conditions in inner core regions of ice sheets but for reasons of preservation and not necessarily formation

regional moment tensor determination in the european mediterranean area initial results the broadband seismic network in the european mediterranean area provides high quality data we invert these regional three component data for the source parameters of moderate to strong earthquakes in the entire european mediterranean area regional seismograms have a good signal to noise ratio even for moderate sized events that are too small for teleseismic analysis the magnitude threshold for source parameter determination can thus be significantly lowered the threshold depends on the average event station distances within dense broadband networks we analyze mw 3 0 earthquakes in areas far from broadband seismic stations the lower bound is mw 4 5 4 8 still considerably lower than the teleseismic analysis threshold about mw 5 0 5 3 for larger events we perform rapid moment tensor analysis using near real time data solutions are posted within hours after event occurrence in a second step we merge near real time and later available data to obtain a regional moment tensor catalog of moderate to large earthquakes for the entire european mediterranean area within less than 1 year we have analyzed 67 earthquakes ranging in size from mw 2 9 to 7 5 the solutions cover the seismically active areas of the european mediterranean area particularly important are solutions for slowly deforming regions where large earthquakes that could be analyzed with teleseismic data occur infrequently the solutions are reliable for events with independent source parameter estimates the agreement is generally high the solutions are robust variations in epicentral parameters source depth or exact choice of stations do not affect source parameter estimates strongly the moment magnitudes provide a unified estimate of earthquake size for the european mediterranean area we perform regression analyses to link our moment magnitudes with local body and surface wave magnitudes

new constraints on the intraplate stress field of the amurian plate deduced from light earthquake focal mechanisms abstract the amurian plate plays an important role for the understanding of eastern asian plate dynamics different models of rigid rotation and relative velocities with respect to adjacent plates have been proposed as few gps data and sparse stress observations have been available until today particularly for the intraplate region these models have proven hard to confirm or deny to address this we determine new focal mechanisms for this region and perform a stress inversion for selected parts of the plate in order to provide better constraints on the plate dynamics most strong earthquakes occur on active plate margins and for these events focal mechanisms are routinely calculated by moment tensor inversion using teleseismic data on a global scale away from the plate margins earthquake magnitudes are smaller and the efficiency of such automated procedures strongly depends on the number of seismic records available using the frequency sensitive moment tensor inversion allows us to determine source mechanisms of light events with a smaller number of data for the amurian plate interior we calculate 41 focal mechanisms for crustal earthquakes from 1993 to 2008 3 9 mw 5 4 we combine these data with additional solutions from the literature to perform formal stress inversions for three separate regions the reliability of the resulting stress orientations is evaluated by bootstrap analysis to show the variability of the principle stress axes for all regions the resulting stress field shows a dominant strike slip regime with an ene wsw orientation of the maximum horizontal compressional stress sh and is consistent with borehole stress data from the world stress map at the margins and in the central part of the amurian plate moreover our analysis reveals differences in both the stress ratio and the sh orientation within the plate interior while the northern part of the amurian plate might be influenced by the baikal rift in terms of a small anti clockwise rotation of sh the eastern part of the plate clearly responds to the far field plate boundary forces from the subducting pacific plate

frequency sensitive moment tensor inversion for light to moderate magnitude earthquakes in eastern africa 1 we provide a procedure for the routine determination of moment tensors from earthquakes with magnitudes as low as mw 4 4 using data recorded by only a few permanent seismic stations at regional to teleseismic distances waveforms are inverted for automatically determined frequency pass bands that depend on source receiver locations as well as the earthquake magnitude inversion results are stable against small variations in the frequency band and provide low data variances i e a good fit between observed and modelled waveform traces the total frequency band used for our procedure ranges from 10 mhz to 29 mhz periods of 35 s to 100 s this enables us to determine focal mechanisms for earthquakes that were not derived previously by routine procedures of cmt or other agencies as a case study we determine focal mechanism solutions of 38 light to moderate magnitude earthquakes in eastern africa between 1995 and 2002

structure and tectonic development of the southern rocky mountain trench the rocky mountain trench is one of the youngest most prominent and most enigmatic structures of the canadian cordillera approximately 650 km of seismic reflection data providing regional three dimensional coverage over an area of 10 000 km include six crossings of the rocky mountain trench between 49 n and 50 15 n prominent reflections from mid proterozoic moyie sills outline thrust and fold structures of a late jurassic to early cretaceous fault system that was cut by the rocky mountain trench fault in the tertiary the near basement reflections outline a 10 km high west facing basement ramp the hinge line of which spatially coincides with the rocky mountain trench in this area this ramp is part of a mid proterozoic margin upon which the belt purcell supergroup was deposited and is preserved beneath the trench during mesozoic contraction the basal detachment of the foreland belt closely followed the craton cover contact across the basement ramp thrusting ceased and extension was initiated when a culmination of thick basinal strata was juxtaposed with the basement ramp in the eocene miocene the basement ramp and the culmination above it focused stress reactivating the basal detachment and causing extensional faulting in the southern rocky mountain trench the rocky mountain trench fault may be linked via the basal detachment to the flathead fault on the east and the eocene extensional faults that flank the omineca belt on the west

glacial terrain zone analysis of a fragmented paleoglaciologic record southeast keewatin sector of the laurentide ice sheet abstract a highly fragmented subglacial landscape is recognized at the regional to sub regional scales in northeastern manitoba canada in the southeast keewatin sector a core region of the laurentide ice sheet new field based ice flow indicator measurements mapping of subglacial landforms remote sensing and aerial photograph and a re examination of previously published data from an 8100 km2 area in northeastern manitoba show that the preserved subglacial record reflects a complex and potentially long glacial history five streamlined landform flowsets are mapped a much higher degree of inheritance in the field based ice flow indicator data than previously reported allows for recognition of multiple ice flow phases analysis of the characteristics of the subglacial landscape combined with a relative age chronology established with field based indicators led to the recognition of disjoint zones with internally consistent glacial histories termed glacial terrain zones gtz these gtz were then classified as 1 relict glacial 2 palimpsest or 3 deglacial in nature our data suggest that while the southern keewatin sector was affected by regional ice divide translocation this alone cannot explain the fragmented high inheritance landscape we suggest that the subglacial landscape was continually evolving and subject to spatio temporal variations in intensity of erosion transportation and or deposition throughout multiple glacial events subglacial bed mosaic preservation of relict and palimpsest terrain likely occurred under large sticky low erosion regions these regions could have formed by at least two different mechanisms heterogeneous switch from warm based to cold based ice or within a warm based subglacial environment from wet to stiff dewatered till establishment of the regionally extensive 700 km wide by at least 500 km long dendritic esker channel system may have caused rapid spatially variable dewatering of the substrate far back under the ice sheet the gtz approach integrates all available data e g flowsets and other landform data striations to advance our interpretation of the spatio temporal evolution of subglacial dynamics in areas where the degree of landscape inheritance and overprinting is spatially highly variable this mosaic may be a characteristic net effect of landscape evolution beneath the core regions of ice sheets

rogen moraine an example of glacial reshaping of pre existing landforms abstract rogen moraine is widely distributed in the core areas of the former scandinavian and laurentide ice sheets it is generally agreed upon that these gently arched ice flow transverse ridges can be used in reconstructions of paleo ice flow patterns and that they indicate a melted bed or poly thermal basal ice regime however the processes of ridge generation have been contentious this study proposes a two stage formation of rogen moraine based on detailed sedimentological and structural investigations in excavated trenches in a rogen moraine landscape in the province of dalarna central sweden field data suggest that rogen moraine ridges are the reshaped remains of pre existing transverse moraine ridges originally deposited from ice cored moraines in an ice marginal zone due to back and down wasting of ice cores inter ridge troughs were filled with debris flow and fluvial deposits which after landscape inversion were transformed to areas of transverse and hummocky moraines it is proposed that this primary landscape formation occurred during an early weichselian deglaciation this relict landscape was later preserved beneath cold based mid to late weichselian ice sheet s which turned wet based during the preboreal deglaciation phase and re moulded the precursor landforms into rogen moraine

ribbed moraine stratigraphy and formation in southern finnish lapland characteristics of ribbed moraines the dominating moraine type in southern finnish lapland have been studied in detail the ridges are composed of several till units of which the bottommost units consist of mature basal tills and the surficial parts are enriched with local short transport rock fragments and boulders in till and at the surface of ridges as a result of this re examination a two step model of the formation process of ribbed moraines is presented in the first stage while cold based conditions prevailed both the bottommost part of the ice sheet and the frozen substrate fractured under compressive ice flow following glacial transport of fractured blocks and formation of the transverse ridge morphology erosion between the ridges continued owing to freeze thaw process under variable pressure conditions in the areas with a low pre existing till sheet the process caused quarrying of the bedrock surface and subsequent deposition of rock fragments and boulders under high pressure on the next ridge the most suitable conditions for ribbed moraine formation existed during late weichselian deglaciation after the younger dryas when the climate warmed very quickly leading to an imbalance between a warm glacier surface and a cold base copyright 2006 john wiley sons ltd

drumlins in ice sheet reconstructions with reference to the western pennines northern england abstract drumlin morphology and distribution can be used to determine the palaeoglaciological conditions under which subglacial bedforms were created by late pleistocene ice sheets detailed field mapping of part of the large drumlin fields in northern england in particular the identification of areas of superimposed drumlins has been shown to be of significance in the delimitation of the ice divide within the area the overall distribution of the subglacial bedforms has also been used to define the extent of ice streams within this part of the late devensian dimlington stadial ice sheet based on the physical principles which underlie the deformational model of drumlin formation and present day glaciological information on subglacial ice sheet conditions variations in drumlin morphology have allowed a first attempt at reconstructing areas of high 100 kpa and low

geologically and geomorphologically constrained numerical model of laurentide ice sheet inception and build up abstract the locations shapes and masses of evolving ice sheets during interglacial to glacial transitions remain elusive but need to be clarified for identification of the climatic feedbacks that amplified low amplitude insolation changes to become the major global climatic shift of the last glacial maximum the best way to explore probable spatial patterns of ice sheet inception and build up is through ice sheet modelling and validating model output against geomorphological and geological data we have modelled the 120 55 kyr bp evolution of the laurentide ice sheet focusing on the locations outline flow patterns and basal thermal regimes of its precursor ice centres for this we employed a time dependent mass balance driven finite element model forced with grip ice core oxygen isotope values calibrated to temperature the model achieves a good fit to relict ice flow systems in keewatin the interior plains and the hudson bay lowland thus our model indicates that the first coherent ice centre in north america was situated over baffin island and the melville and boothia peninsulas and expanded onto mainland canada at 90 75 kyr bp a previously unknown 200 km long moraine zone near the thlewiaza river keewatin may demarcate the marginal position of this early central arctic ice sheet cordilleran and keewatin ice merged and the hudson bay lowland was inundated from the east from quebec by 65 kyr bp

evidence of ancient continental glaciation in the martian northern plains whorled ridges spaced about 2 6 km and forming lobate patterns with lobe widths of about 150 km occur at many locations in the northern plains of mars commonly in close association with sinuous troughs that contain medial ridges these landforms resemble moraines tunnel channels and eskers found in terrestrial glacial terrains such as the midcontinent of north america some martian landscapes may have formed by disintegration of continental glaciers that covered much of the northern plains into the early amazonian i e late in martian geologic history meltwater processes apparently were important in the collapse of these hypothesized ice sheets hence the glaciers apparently were wet based in part whereas striking similarities exist among areas of the northern plains and some glaciated pleistocene terrains on earth there are also important differences notably drumlin fields such as those in many glacial landscapes on earth are rare absent or not yet resolved in images of the martian northern plains another major difference is that postglacial fluvial and other water related modifications especially erosion of pleistocene terrains are substantial but similar modifications are not observed in the northern plains a virtually complete and sudden decline in the activity of liquid surface water following glaciation in the northern plains seems to be implied the climatic implications of the hypothesized martian glaciers and their decline are unclear we investigate two possibilities alternatively involving a relatively warm paleoclimate and the modern martian climate the hypothesized ice sheets in the basins within the northern plains generally at elevations lower than 1 km suggest a relationship of these frozen bodies of water with former regional lakes or seas which may have formed in response to huge discharges of water from martian outflow channels this possible relationship has been modeled glaciers may have evolved from seas by their progressive freezing and then grounding and sublimational redistribution of sea ice the transition to glaciation may have taken several million years if the climate was very cold comparable to today s or tens of thousands of years if the climate was as warm as modern antarctica a glacierized sea may have involved an extended period of glaciolacustrine and ice shelf processes

controls on the location morphology and evolution of complex esker systems at decadal timescales breiðamerkurjokull southeast iceland this paper uses detailed mapping of eskers to address three questions which are important for reconstructing meltwater behaviour beneath contemporary and ancient ice masses what controls the morphology of simple and complex esker systems how do esker systems evolve through time and are esker patterns compatible with the groundwater controlled hydraulic spacing of esker tunnels esker crestlines and widths are mapped on the brei amerkurjokull foreland for eight time slices between 1945 and 2007 from high resolution 50 cm aerial photography permitting their long term morphological evolution to be analysed in a high level of detail we find that complex eskers develop where meltwater and sediment is abundant such that sediment clogs channels forming distributary eskers isolated eskers are simpler and smaller and reflect less abundant meltwater and sediment which is unable to clog channels eskers may take several decades to emerge from outwash deposits containing buried ice and can increase or decrease in size when ice surrounding and underlying them melts out it has been suggested that groundwater channel coupling dictates the spacing between eskers at brei amerkurjokull our results do not dispute this but suggest that the routing of sediment and meltwater through medial moraines is an additional important control on esker location and spacing these results may be used to better understand the processes surrounding esker formation in a variety of geographical settings enabling a more detailed understanding of the operation of meltwater drainage systems in sub marginal zones beneath glaciers and ice sheets this article is protected by copyright all rights reserved

superimposition of ribbed moraines on a palaeo ice stream bed implications for ice stream dynamics and shutdown the sediments and landforms preserved on palaeo ice stream beds can provide important information about their subglacial conditions and flow mechanisms and the processes accompanying their shutdown in this paper detailed observations of an intriguing subglacial landform assemblage of ribbed moraines superimposed on glacial lineations on the dubawnt lake ice stream bed north west canadian shield are presented including their morphometry internal structure from ground penetrating radar gpr surveys and from glaciogeological analysis and sedimentological characteristics from sediment architecture and lithofacies analysis the observations suggest an abrupt change in ice dynamics that correlates with two phases of glacial landform development this hypothesis is based on evidence from a deformed lodgement till which subsequently underwent brittle deformation and developed prominent thrust shear structures and tension fractures tension fractures are observed in a sediment exposure and thrust structures are observed in gpr surveys where they occur most prominently in the ribbed moraine ridge crests the presence of the fractures and their association with a population of clasts in the till that are orientated with their a axes transverse to the inferred ice flow direction suggests a compressional flow regime it is therefore inferred that the glacial lineations were formed under an extensional flow regime during ice stream activity but that at some point patches of till under the ice stream stiffened through dewatering the subsequent increase in basal shear stress resulted in compressional flow and the development of subglacial thrusting and the building of ribbed moraines we therefore suggest that ribbed moraines may form in areas of compressional flow under ice streams i e sticky spots and or at the transition between slow and fast ice flow along parts of an ice stream the general absence of ribbed moraines on most other palaeo ice stream beds suggests that either these ice streams continued operating during deglaciation or processes other than the development of localized compressional flow sticky spots led to their shutdown e g ice depletion

stress patterns in northern iraq and surrounding regions from formal stress inversion of earthquake focal mechanism solutions the collision zone between the arabian and eurasian plates is one of the most seismically active regions northern iraq represents the northeastern part of the arabian plate that has a suture zone with the turkish and iranian plates called the bitlis zagros suture zone the orientations of the principal stress axes can be estimated by the formal stress inversion of focal mechanism solutions the waveform moment tensor inversion method was used to derive a focal mechanism solution of 65 earthquakes with magnitudes range from 3 5 to 5 66 in the study area from focal mechanism solutions the direction of slip and the orientations of the moment stress axes p n and t on the causative fault surface during an earthquake were determined the dataset of the moment stress axes have been used to infer the regional principal stress axes 1 2 and 3 by the formal stress inversion method two inversion methods which are the new right dihedron and the rotational optimization methods were used the results show that six stress regime categories exist in the study area however the most common tectonic regimes are the strike slip faulting 43 94 unspecified oblique faulting 27 27 and thrust faulting 13 64 regimes in most cases the strike slip movement on the fault surfaces consists of left lateral sinistral movement the normal faulting is located in one small area and is due to a local tensional stress regime that develops in areas of strike slip displacements as pull apart basins the directions of the horizontal stress axes show that the compressional stress regime at the bitlis zagros suture zone has two directions one is perpendicular to the suture zone near the iraq iran border and the second is parallel in places as well as perpendicular in others to the suture zone near the iraq turkey border in addition the principal stress axes in the sinjar area near the iraq syria border have a e w direction these results are compatible with the tectonic setting of the arabian eurasian continental collision zone and the anticlockwise rotation of the arabian plate that is evidently responsible for the strike slip displacements on fault surfaces

lithoprobe seismic reflection imaging of rocky mountain structures east of canal flats british columbia lithroprobe seismic reflection data coupled with information from industry seismic data and surface geology image the thin skinned structures of the western rocky mountains from the main ranges to the rocky mountain trench near canal flats british columbia reprocessing of the lithoprobe seismic reflection line was conducted to improve resolution of upper crustal features careful application of conventional processing techniques significantly improved the coherence of reflections from the first 6 s a spatial semblance filter was applied to further enhance coherent signal and residual statics corrections were applied by cross correlation of unstacked data with semblance filtered pilot traces a near basement reflection zone arising from middle cambrian strata is visible on an industry reflection profile at an approximate depth of 8 km beneath the main ranges a similar reflection zone is imaged on the lithoprobe data at a depth of 11 km bsl but is interpreted as arising from proterozoic strata the

active stress field and fault kinematics of the greater caucasus abstract this work contributes to depict the current seismicity fault kinematics and state of stress in the greater caucasus territories of georgia azerbaijan and russia we merged and homogenized data from different earthquake catalogues relocated 1000 seismic events created a database of 366 selected focal mechanism solutions 239 of which are new and performed a formal stress inversion preferential alignments of crustal earthquake foci indicate that most seismic areas are located along the southern margin of the belt and in the north eastern sector this is consistent with the presence of dominant active wnw ese faults parallel to the mountain range in the entire greater caucasus a dominant nne ssw oriented greatest principal stress 1 controls the over all occurrence of earthquakes of minor and major magnitude main earthquakes are characterized by a vertical least principal stress 3 corresponding to reverse kinematics reverse slip is more common along the southwestern and north eastern foothills of the greater caucasus although in these areas there are also scattered strike slip events this suggests the presence of local stress fields with horizontal 1 and 3 in the central southern part of the mountain belt in correspondence of the local collision between the lesser and the greater caucasus 1 rotates to nnw sse the strike slip events instead dominate along the southern flank of the central eastern mountain range this is interpreted as the effect of the collision that promotes eastward escape of the tectonic blocks located to the east

seismic anisotropy and its precursory change before eruptions at piton de la fournaise volcano la reunion the piton de la fournaise volcano exhibits frequent eruptions preceded by seismic swarms and is a good target to test hypotheses about magmatically induced variations in seismic wave properties we use a permanent station network and a portable broadband network to compare seismic anisotropy measured via shear wave splitting with geodetic displacements ratios of compressional to shear velocity vp vs earthquake focal mechanisms and ambient noise correlation analysis of surface wave velocities and to examine velocity and stress changes from 2000 through 2012 fast directions align radially to the central cone and parallel to surface cracks and fissures suggesting stress controlled cracks high vp vs ratios under the summit compared with low ratios under the flank suggest spatial variations in the proportion of fluid filled versus gas filled cracks secular variations of fast directions and delay times dt between split shear waves are interpreted to sense changing crack densities and pressure delay times tend to increase while surface wave velocity decreases before eruptions rotations of may be caused by changes in either stress direction or fluid pressure these changes usually correlate with gps baseline changes changes in shear wave splitting measurements made on multiplets yield several populations with characteristic delay times measured incoming polarizations and fast directions which change their proportion as a function of time an eruption sequence on 14 october 2010 yielded over 2000 shear wave splitting measurements in a 14 h period allowing high time resolution measurements to characterize the sequence stress directions from a propagating dike model qualitatively fit the temporal change in splitting

the comoros archipelago a right lateral transform boundary between the somalia and lwandle plates abstract the origin of the comoros archipelago in the mozambique channel is the subject of a longstanding controversy this volcanic chain has been successively interpreted as a hotspot track as built on an intraplate fracture zone or a passive margin or as the northern limit of a diffuse deformation zone in the nubia somalia plate system none of these interpretations being entirely satisfactory it is also possible that the volcanism of the comoros is a branch of the east african rift system and delineates the still poorly constrained northern boundary between the lwandle and somalia plates to better understand the origin of the comoros archipelago we combined a formal stress inversion of earthquake focal mechanisms and deformation structures faults and dykes observed on three islands mayotte anjouan and moheli with a morphologic study of the repartition of onshore and offshore volcanic vents in the area earthquake focal mechanisms and field observed deformation structures both yield a generalized strike slip regime with a maximum horizontal stress oriented nw se in tandem the study of topographic and bathymetric features shows that volcanic vents follow a preferential repartition along two trends n105 10 lineaments up to 100 km long and n145 10 less than 60 km long lineaments organized in an en echelon fashion earthquakes deformation structures and volcanic vents all consistently designate the comoros archipelago as an e w elongated 150 km wide zone of right lateral tear in the lithosphere because the clockwise rotation of somalia relative to lwandle requires the existence of such a right lateral shear zone we interpret the comoros archipelago as the northern boundary between the two plates this plate boundary is still in an immature state which is why it remained undetected until now

active tectonics of central western caucasus georgia abstract this work contributes to a better knowledge of potentially seismogenic faults of the georgia greater and lesser caucasus by evaluating the distribution of earthquake foci active tectonic stress field kinematics and geometry of main fault planes we consider all the information coming from field structural geology geomorphology seismological data from historical and instrumental catalogues seismic reflection sections as well as new focal mechanism solutions these data enable recognizing some active ene wsw reverse faults in the core of the greater caucasus that are parallel to the mountain range at the southernmost front of the greater caucasus a series of main thrusts dipping towards nne are active with up to hundreds km long segments along this thrust zone a potentially locked segment is present about 90 km long the studied section of the lesser caucasus has active structures along the northern front given by south dipping thrusts as well as in the central core where strike slip and oblique faults coexist the transcaucasian depression between the two mountain ranges shows an ongoing inversion tectonics of the central part of the rioni basin where active n to ne dipping reverse faults are present accompanied by clear evidence of uplift of a wide area the data are coherent with a n s to nne ssw contraction of the central western greater caucasus and lesser caucasus although in general the seismicity decreases westward in terms of number of earthquakes and magnitude seismological and geological structural data in the rioni basin indicate here a quaternary propagation of deformation towards the west

morphological characteristics formation and glaciological significance of rogen moraine in northern scotland rogen moraine are enigmatic landforms whose exact origin is still debated we use nextmap digital surface models and aerial photographs to map the distribution of previously unreported fields of rogen moraine in the vicinity of loch shin northern scotland existing models of formation are tested against detailed morphological rogen moraine characteristics obtained from the remote sensing data and field observations detailed morphometric analyses combined with their geographical setting lead us to postulate a likely mechanism of formation rogen moraine appear to have formed in areas where there were strong basal ice flow velocity gradients thrusting by compression or fracturing by extension of preexisting partially frozen sediment probably occurred in these areas resulting in rogen moraine formation a general down ice increase in ridge crest spacing suggests that the latter process may have been dominant and is consistent with the location of rogen moraine in the lee of topographic obstructions in areas that experienced overall extensional ice flow we also suggest that at least one field of rogen moraine formed where lateral basal ice flow velocity gradients were strongest possibly in a subglacial shear margin setting given their location the landforms may be consistent with formation during headward scavenging of the moray firth palaeo ice stream into a shrinking core of cold based ice

ribbed bedforms on palaeo ice stream beds resemble regular patterns of basal shear stress traction ribs inferred from modern ice streams rapidly flowing ice streams are an important mechanism through which ice sheets lose mass and much work has been focussed on elucidating the processes that increase or decrease their velocity recent work using standard inverse methods has inferred previously unrecognised regular patterns of high basal shear stress sticky spots 200 kpa beneath a number of ice streams in antarctica and greenland termed traction ribs they appear at a scale intermediate between smaller ribbed moraines and much larger mega ribs observed on palaeo ice sheet beds but it is unclear whether they have a topographic expression at the bed here we report observations of rib like bedforms from dems along palaeo ice stream beds in western canada that resemble both the pattern and dimensions of traction ribs their identification suggests that traction ribs may have a topographic expression that lies between and partly overlaps with ribbed moraines and much larger mega ribs these intermediate sized bedforms support the notion of a ribbed bedform continuum their formation remains conjectural but our observations from palaeo ice streams coupled with those from modern ice masses suggest they are related to wave like instabilities occurring in the coupled flow of ice and till and modulated by subglacial meltwater drainage their form and pattern may also involve glaciotectonism of subglacial sediments

moment tensor inversion from mednet data 1 large worldwide earthquakes of 1990 we develop a method for the rapid determination of the moment tensor of large worldwide earthquakes by inversion of long period data recorded by the mednet regional network and we apply it to the most significant events of 1990 march 3 fiji and 25 costa rica may 12 sakhalin 20 sudan and 30 romania june 20 iran july 16 luzon and december 30 new britain the comparison with cmts and moment tensors by usgs shows that an advanced regional seismic network is capable of providing reliable and rapid control of the seismic source for worldwide seismicity

the carstairs kames lanarkshire scotland morphology sedimentology and formation the carstairs kames have been the subject of debate for over 150 yr a synthesis of previous work along with new sedimentological data is used to reappraise this classic british esker locality three morphological elements are recognised i large sinuous and anastomosing ridges ii large irregular linear mounds and iii small low and irregular mounds the main ridge system is composed of a core of boulder gravel with sand pebble gravel above and adjacent to the core the large linear mounds contain a varied facies range which include glaciolacustrine sediments deltaic sequences laminites and dropstones debris flows and glaciofluvial channel systems all the deposits both in the main ridges and in the adjacent linear mounds contain syn and post depositional subsidence structures including normal faults synclinal folds and growth faults a range of potential origins for these landforms is reviewed and it is suggested that glaciofluvial sedimentation in a supraglacial environment controlled by a topography of ice cored ridges is the most appropriate depositional model 1997 john wiley sons ltd

deep transverse basement structural control of mineral systems in the southeastern canadian cordillera1geological survey of canada contribution 20110294 intermittent reactivation of deep paleoproterozoic and archean aged transverse structures in the north american cratonic basement beneath the southeastern canadian cordillera exerted an important influence on the subsequent sedimentary intrusive deformation and mineralization history two regional crossbelt transverse structural corridors recognized by recurrent episodic changes in sediment thickness and facies and anomalous transverse structural trends occur within the thrust and fold belt palinspastic restoration of the exposed transported structural corridors showed that the northern and southern structural corridors are cover expressions of the red deer zone and vulcan low structures in the cratonic basement respectively transverse basement controlled structural corridors enhanced the mineral potential and mineralization systems along them by localization of sedimentary facies favourable for mineralization hydrothermal flow intrusions and favourable structures for mineralization greatest enhancement of hydrothermal flow and mineralization occurred near the intersection of basin parallel and transverse structures greater opportunity for mineralization and intrusion occurred not only along the exposed corridors but also in the west above their undeformed root in the basement the processes that intensified mineralization and localized intrusions along transverse basement controlled structural corridors in the southeastern canadian cordillera should have occurred in thrust and fold belts elsewhere the niobium bearing aley carbonatite complex in the eastern cordillera of northeastern british columbia may be an example of this

moment tensor inversion of recent small to moderate sized earthquakes implications for seismic hazard and active tectonics beneath the sea of marmara summary we retrieve the moment tensors of 64 small to moderate sized events that occurred mostly beneath the sea of marmara using near field data recorded at strong motion and broad band seismic stations the near field displacement records are inverted to their sources utilizing kuge s method where the best fit between the synthetic and observed seismograms is achieved through searching a centroid moment tensor cmt point in a grid scheme we also analyse the stress fields acting in the eastern and western parts of the sea of marmara by inverting the p and t axes of the focal mechanisms obtained significant biases in the stress tensors are obtained the nearly horizontal maximum compressive axis 1 in the western part is rotated 16 counter clockwise compared with 1 in the eastern part the 2 axis is close to vertical shear tectonic regime in the east and the plunge of 2 axis in the west is 36 transpressive tectonic regime changes in the 3 axis are also observed that is it is close to horizontal in the east and dips 49 in the west the spatial distribution of the focal mechanisms suggests that the stress field in the eastern part of the sea of marmara is homogenous compared with the western part and we identify five distinct subsidiary faults 1 a wnw ese striking right lateral strike slip fault located a few kilometres sw of the princes islands 2 a wsw ene striking right lateral strike slip fault named the yalova hersek fault 3 an e w striking normal fault located onshore between

african stress pattern from formal inversion of focal mechanism data abstract the kinematic models and the associated orientation of extensional stress of the east african rift system have been subjected to much debate since a long time in the past decades the proposed models relied on the interpretation of the overall rift geometry geological fault slip data and the few focal mechanisms available these models generally suffer of a poor time control and an underestimation of the possible changes in the stress field and geodynamic regime with time and space in the recent years there has been a significant increase in the number of focal mechanisms available for the entire rift system and it is now possible to estimate the present day stress field in relative detail based on seismotectonic data alone we compile 347 focal mechanism data from the global harvard cmt catalogue and various other sources and grouped 332 of them in 24 distinct regions boxes on the basis of their geographical proximity kinematic homogeneity and tectonic setting for each box and for the same data set reduced stress tensors have been obtained by formal stress inversion using both the tensor program delvaux sperner 2003 and the slick method michael 1984 1987 both inversion methods show in comparable results in terms of horizontal stress axes orientations and tectonic stress regimes which stem for the robustness of the approach the obtained stress pattern reflects a complex interaction between 1st order effects as different driving forces including plate boundary forces and 2nd and 3rd order effects as gravitational potential of topography intra lithospheric processes and the influence of structural heterogeneities of the rift structures the evidence present in the stress orientations of the 2nd and 3rd order stress pattern as the variations in the horizontal stress axes along the axis of the rift are of particular interest as they were not yet captured or shown in earlier numerical models of the stress field additional sources of tectonic forces in supplement to the gravitational potential energy forces as considered in the earlier models are necessary to explain the observed patterns

ribbed moraines in sweden distribution pattern and palaeoglaciological implications abstract a detailed map of ribbed moraines in central and northern sweden is presented they are frequent features over much of the mapped area and the distribution has well defined limits the most abundant ribbed moraines are situated in close connection to areas that are inferred to have been cold based during the retreat of the late weichselian ice sheet while outer fully warm based areas lack ribbed moraine observations have also been made on a more local scale where cold based patches grade into ribbed moraines via a zone of a broken up till cover a model of origin is presented which includes contracting of a frozen core area of a retreating ice sheet at the transition from non sliding to sliding conditions there will be high stresses resulting in local extensional flow at the base of the ice sheet a rising phase change surface frozen thawed material would cause detachment and boudinage like breaking up of a pre existing till cover thawed at the bedrock contact but still frozen to the ice sole the orientation of ice flow during the formation of the ribbed moraines closely matches the ice flow directions of the deglaciating late weichselian ice sheet thus ribbed moraines are considered to be deglaciation landforms typical of shrinking cold based zones of a retreating ice sheet

automatic regional moment tensor inversion in the european mediterranean region summary we produce fast and automatic moment tensor solutions for all moderate to strong earthquakes in the european mediterranean region the procedure automatically screens near real time earthquake alerts provided by a large number of agencies each event with magnitude m 4 7 triggers an automatic request for near real time data at several national and international data centres moment tensor inversion is performed using complete regional long period 50 100 s waveforms initially the data are inverted for a fixed depth to remove traces with a low signal tonoise ratio the remaining data are then inverted for several trial depths to find the best fitting depth solutions are produced within 90 min of an earthquake we analyse the results for the period 2000 april to 2002 april to evaluate the performance of the procedure for quality assessment we compared the results with the independent swiss regional moment tensor catalogue srmt and divided the 87 moment tensor solutions into three groups 38 a quality solutions with well resolved m w depth and focal mechanism 21 b quality solutions with wellresolved m w and 28 unreliable c quality solutions the non homogeneous station and event distributions varying noise level and inaccurate earthquake locations affected solution quality for larger events m w 5 5 we consistently obtained a quality solutions for m w 4 5 5 5 we obtained a and b quality solutions solutions that pass empirical rules mimicking the a posteriori quality for our data set are automatically disseminated

the determination of source parameters for small earthquakes from a single very broadband seismic station the installation of very broadband seismic stations makes it possible to recover the source parameters of small earthquakes 2 5 ml 5 0 which occur at local and regional distances if the gross crustal structure along the travel path is known it is possible to use the p sv and sh displacement waveforms from a single station to determine the seismic moment tensor although the details of the crustal structure strongly affect the body waveforms at regional distances the signature of the seismic source orientation on the waveform is robust at frequencies less than 1 3 hz we explore the trade offs between crustal model hypocentral depth and filtering for a linear moment tensor inversion procedure the procedure is tested on two small earthquakes which occurred in the rio grande rift and were recorded at the iris usgs station anmo the agreement between the single station moment tensor inversion fault plane parameters and those determined from local first motions is excellent

pattern recognition of lidar data and sediment anisotropy advocate a polygenetic subglacial mass flow origin for the kemijarvi hummocky moraine field in northern finland abstract object based image analysis and supervised machine learning on a digital elevation model derived from airborne laser scanning data were conducted to assess the aggregate raw material potential over the kemijarvi hummocky moraine field in finnish lapland geomorphometric analysis revealed surface stoniness to be diagnostic of moraine hummocks it was utilized to detect true moraine hummocks from among the potential hummocks delineated using object based image analysis with logistic regression of curvature features derived from the digital elevation model area under the receiver operating characteristics curve auc 0 77 based on the electrical sedimentary anisotropy data the kemijarvi moraine is polygenetic such that the ridges are diagonally and erosionally fluted from sector 280 290 on their surfaces while the ridge cores are deposited from the nw from sector 310 340 the cores are composed of infill gravels and crudely stratified diamict sequences we consider the core of the kemijarvi hummocky moraine field to represent pre existing early weichselian subglacial ridges rather than being generated through monogenetic late weichselian compressional shearing and stacking frozen bed extension or bed ribbing instability mechanisms as presented for ribbed moraines that are transverse to ice flow recently evidence has been presented of multiple slip events earthquakes with moment magnitudes mw 6 7 7 0 up ice from kemijarvi we therefore propose that the genesis of the hummocks may be associated with past early weichselian fault instability within glacio isostatic adjustment s which was able to generate subglacial water bodies possibly lakes and saturated materials that were forced towards the se based on this new geomorphological evidence from mapping using a digital elevation model derived from airborne laser scanning data and azimuthal conductivity surveys combined with the reinterpretation of previously presented geophysics and sedimentological observations we suggest the kemijarvi hummocky moraine field to be reconsidered as the kemijarvi subglacial mass flow field which holds significant potential for construction aggregate materials

the mode of deformation in the orogenic mid crust revealed by seismic attribute analysis 1 the processes and the structures within the middle and the lower crust are intimately related to the evolution of orogenies but more detailed knowledge is needed of these deep crustal processes seismic reflection data chiefly displayed in amplitude are commonly used to interpret deep crustal structures the strongest amplitude events are probably related to lithological changes and do not necessarily correspond to geological structures tectonic boundaries or deformation fabrics furthermore the detailed structures and the strain distribution between the interpreted structural boundaries remain obscure here we show an example of how seismic attributes combined with the seismic facies interpretation technique can be used to enhance 2d seismic reflection data from the palaeoproterozoic svecofennian crust of southern finland to reveal unprecedentedly detailed information about the deformation fabrics within the mid crust of a collisional orogen the images are plausibly interpreted to show that the extension lateral flow of the orogenic middle and lower crust was mainly accommodated by kilometer scale s c structures the structures form penetrative deformation fabrics which are correlated with outcrop observations the successful enhancement of the seismic data confirms the ductile extension affecting hot orogenic crust and gives new information about the strain distribution of the regional syn to late orogenic deformation the seismic attribute method and the seismic facies interpretational approach described in this paper should be applicable to other seismic datasets from the crystalline basement

glacial dispersal and flow history east arm area of great slave lake nwt canada abstract little work has been completed on paleo ice sheet flow indicators of the laurentide ice sheet west of the keewatin ice divide field mapping sampling and analysis of glaciogenic sediment 500 sample sites in a 33 000 km2 region near the east arm of great slave lake in northwestern canada provided a rare opportunity to improve understanding of sediment erosion and transport patterns glacially eroded bedrock and sedimentary landforms record east to west flow with nw and sw divergence mapped within a portion of the great slave lake flow tract transported till reflects a similar divergent flow pattern based on dispersal geometries for multiple indicators e g heavy minerals and lithic fragments which are aligned with the dominant and latest ice flow direction glaciofluvial erosion e g s forms and till removal transport and deposition mainly as esker sediment are set within 0 3 3 km wide meltwater erosional corridors spaced regularly at 10 15 km intervals transport paths and distances are comparable in till and esker sediment however distances appear to be greater 5 25 km in some esker constituents and indicator minerals are typically more concentrated in esker sediment than in till corridors form a divergent array identical to the pattern of ice flow features the congruence of ice and meltwater flow features is interpreted to be a response to a similar ice sheet gradient and close timing of events late dominant glacial ice flow and meltwater flow the similarity in glacial and glaciofluvial flow patterns has important ramifications for event reconstruction and for exploration geologists utilizing mineral and geochemical tracing methods in this region and possibly other parts of northern canada the correspondence between east arm dispersal patterns landforms and flow indicators supports interpretation of a simple and predictable single flow divergence model this is in contrast to previous multi flow models in which fan shaped geometries are often reported to result from multiple transport events compared to single flow divergence the observed widespread effects of glaciofluvial processes e g erosional corridors indicate a need to update existing terrain process models

formation of mega scale glacial lineations on the dubawnt lake ice stream bed 1 size shape and spacing from a large remote sensing dataset abstract mega scale glacial lineations msgls are the largest flow parallel bedforms produced by ice sheets and are formed beneath rapidly flowing ice streams knowledge of their characteristics and genesis is likely to result in an improved understanding of the rate at which ice and sediment are discharged by ice sheets but there is little consensus as to how they are formed and there are few quantitative datasets of their characteristics with which to formulate or test hypotheses this paper presents the results of a remote sensing survey of 46 000 bedforms on the dubawnt lake palaeo ice stream bed focussing on a central transect of 17 038 that includes highly elongate bedforms previously described as msgls within this transect lineations exceed 10 km in length max 20 km and 23 have elongation ratios 10 1 max 149 1 highly elongate features are interspersed with much shorter drumlin like features but longer bedforms are typically narrower suggesting that their length develops more quickly than or at the expense of their width bedforms are broadly symmetrical in plan form and have a preferred lateral spacing of 50 250 m which implies a regular rather than random pattern of corrugations comparison with drumlins reveals that the more attenuated msgls simply extend the tail of the distribution of data rather than plotting as a separate population taken together this supports the idea of a subglacial bedform continuum primarily controlled by ice velocity but existing hypotheses of msgl formation are either not supported or are insufficiently developed to explain our observations rather we conclude that under conditions of rapid ice flow msgls attain their great length relatively quickly decades through a probable combination of subglacial deformation which attenuates ridges and erosional processes that removes material from between them

subglacial landforms and deposits in central and northern quebec canada with emphasis on rogen moraines abstract the development of the anatomy and the morphology of a relatively simple till sheet deposited over parts of the canadian shield is discussed this is characterized by the common occurrence of well developed streamlined landforms and rogen moraines the sedimentation of the till sheet was an alternating succession of depositional and erosional or landforming events the former leading to the sedimentation of various till lithofacies the latter leading to the development of various morainic terrains this orderly sequence of subglacial events occurred during the deglaciation of central and northern quebec with the controlling factors being bed rock topography and geology ice thickness and basal ice temperatures till lithofacies include in ascending stratigraphic order lodgement till subglacial melt out till immature lodgement till and varieties of supra glacial ablation deposits morainic terrains include drumlinized and fluted ground moraine rogen moraines as well as fluted and unfluted hummocky moraine rogen moraines are formed subglacially a few kilometers behind the glacier margin as a consequence of localized compressive stresses which result in shearing and stacking of slices of near base englacial debris later deposited as a basal melt out till the moraines are believed to be a characteristic landform associated with shield type rock surfaces namely an irregular topography of asymmetric rock basins of all sizes resulting from the areal scouring of hard rocks as well the moraines are believed to be as well a characteristic landform resulting from the flattening profile of the margin of the waning ice sheet the formation of the moraines led to enhanced flow in marginal areas generating late events of streamlining and boulder plucking

global cmt analysis of moderate earthquakes mw 4 5 using intermediate period surface waves a new method for calculating centroid moment tensor cmt solutions for moderate sized earthquakes is presented and tested in the new algorithm which is a modification to the standard harvard cmt method intermediate period surface waves are included in the inversion for source parameters the dispersion of teleseismic surface waves in the period range 40 to 150 sec is predicted by interpolation of recent global phase velocity maps the method is tested on a set of 20 moderate and large 5 2 mw 7 2 earthquakes with known mechanisms the retrieved mechanisms are similar to the previous results even when noise is added to the seismograms to simulate earthquakes of a smaller magnitude mw 4 5 the inversion algorithm is applied to the 1993 klamath falls mainshock and aftershock sequence and the results compare well with earlier results a catalog of mw 4 5 focal mechanisms for greece and surrounding areas for the first six months of 1995 is derived using the new method of analysis

tunnel channels and associated landforms south central ontario their implications for ice sheet hydrology the peterborough trenton drumlin field and associated meltwater erosion marks s forms were interpreted as the products of erosion by turbulent separated flows within a catastrophically released subglacial meltwater sheet the algonquin event recent theoretical modelling of ice sheet hydrology suggests progressive channelization of meltwater during the collapse of such a sheet inductive testing of this hypothesis using observations in south central ontario forms the crux of this paper a geometric model of the interaction of rough ice base and bed surfaces gives inferred meltwater flow patterns such a rough interactive geometry is suggested as the bed is drumlinized and flows responsible for drumlins may be expected to have eroded similar forms into the ice base three landforms in south central ontario namely tunnel channels megachannels and late stage sheet flow scours are described and interpreted as evidence of progressive channelization and flow diversion processes governed by the geometri

geomorphological reconstruction of the labrador sector of the laurentide ice sheet abstract the labrador sector formed one of three major domes of the laurentide ice sheet during the last wisconsinan glaciation reconstruction of its evolution is important because it modulated atmospheric and oceanic circulation over 1 100 ka time scales this paper reports new geomorphological evidence of ice flow which is used to reconstruct glimpses of the behaviour of the labrador sector during its evolution flow evidence indicates a southern position 51 n of the labrador ice divide presumed to be the usual location when the ice sheet was close to its maximum extent a previously inferred dramatic surge of labrador ice across hudson strait and onto baffin island at 9 9 9 4 ka is verified seemingly contradictory evidence regarding deglaciation in northern quebec has been analysed and a reconstruction developed that solves this problem deglacial retreat of the labrador ice sheet was highly asymmetric with rapid retreat of the southern margin northwards migration of the centre of mass by 500 km and slow retreat along the northern margin as it shrank its thermal regime changed from cold centred to entirely cold based and it finally fragmented into many residual ice caps and glaciers this dynamic and asymmetric behaviour may be due to destabilisation of the labrador ice sheet triggered by heinrich event ice streaming through hudson strait

glacial landforms of extreme size in the keewatin sector of the laurentide ice sheet assemblages of glacial landforms of a mega scale are here identified in the keewatin sector of the laurentide ice sheet large till belts or ridges apparent only on satellite imagery and lyi

methane storms as a driver of titan s dune orientation titan s equatorial dunes propagate eastwards whereas titan s surface winds blow towards the west atmospheric simulations suggest that tropical methane storms generate strong eastward gusts that may dominate sand transport on titan s surface