the present day stress field of australia abstract the unusual present day crustal stress pattern of the australian continent has been the subject of scientific debate for over 25 years the orientation of maximum horizontal present day stress s hmax in continental australia is unlike all other major tectonic plates in that the stress pattern shows regional variability and it is not oriented sub parallel to the direction of absolute plate motion previous studies on the stress pattern of australia revealed that the complex stress pattern of the continent is controlled at a first order by the superposition of plate tectonic forces exerted at the plate boundaries however prior analysis of the contemporary australian crustal stress pattern have been unable to model or explain the stress pattern observed in most of eastern australia and has not extensively addressed the numerous smaller scale variations in stress orientation the recent development of unconventional reservoirs in australia has resulted in a greatly increased amount of new data for stress analysis in previously unstudied or poorly constrained areas in eastern australia in addition stress analysis in conventional hydrocarbon mineral and geothermal exploration in all other parts of the continent provides the opportunity to review and update the australian stress map asm this study presents the new release of the asm with a total of 2150 stress data records in australia increased from 594 data records in 2003 the 2016 asm contains 1359 data records determined from the interpretation of drilling related stress indicators 650 from earthquake focal mechanism solutions 139 from shallow engineering measurements and two from geological indicators the results reveal four distinct regional trends for the s hmax orientation in australia including a nne ssw s hmax trend in northern and northwestern australia which rotates to a prevailing e w orientation in most western and south australia the orientation of s hmax in eastern australia is primarily ene wsw and swings to nw se in southeastern australia a comparison between the new asm database and neotectonic features further confirms the role of contemporary stress in recent deformation of the australian crust the 2016 asm reveals significant discrepancies between newly observed s hmax orientations and predictions by published geomechanical numerical models for the australian continent forces generated at the boundary of indo australian plate remain the major control on the regional crustal stress pattern in continental australia however the increased data density particularly in eastern australia reveals numerous local perturbations of the stress field that were not previously clearly captured hence the key findings of the new release are that local intra plate stress sources are more significant than previously recognized particularly in eastern australian basins and cause substantial local scale rotations of the present day crustal stress pattern that have not been factored into existing australian stress models

long term behaviour of australian stable continental region scr faults abstract australia boasts arguably the richest late neogene to quaternary faulting record in stable continental region scr crust anywhere in the world variation in fault scarp length vertical displacement proximity to other faults and relationship to topography permits division of the continent according to fault character six onshore neotectonic domains are recognised with an additional offshore domain proposed by analogy with the eastern united states each domain relates to a distinct underlying crustal type and architecture broadly considered to represent cratonic non cratonic and extended environments in general greater topographic expression associated with faults occurring in extended crust relative to non extended crust suggests a higher rate of seismic activity in the former setting consistent with observations worldwide using the same reasoning non cratonic crust might be expected to have a higher rate of seismic activity than cratonic crust this distinction together with the variation in fault character between domains should be recognised in attempts to identify analogous systems worldwide a common characteristic of morphogenic earthquake occurrence in australia appears to be temporal clustering periods of earthquake activity comprising a finite number of large events are separated by much longer periods of seismic quiescence at the scale of a single fault and of proximal faults in several instances there is evidence for deformation at scales of several hundred kilometres switching on and off over the last several million years what is not clear from the limited palaeoseismological data available is whether successive active periods are comparable in terms of slip number of events magnitude of events etc regardless this apparent bimodal recurrence behaviour poses challenges for probabilistic seismic hazard assessment psha these rely on the simplifying assumption that large earthquake recurrence for long return periods is not random i e poissonian presently our ability to incorporate such time dependent models is limited by available data

rupture characteristics and bedrock structural control of the 2016 mw 6 0 intraplate earthquake in the petermann ranges australia the 20 may 2016 surface rupturing intraplate earthquake in the petermann ranges is the largest onshore earthquake to occur in the australian continent in 19 yr we use in situ and interferometric synthetic aperture radar surface observations aftershock distribution and the fitting of p wave source spectra to determine source properties of the petermann earthquake surface observations reveal a 21 km long surface rupture trace strike 294 29 with heterogeneous vertical displacements 0 015 along rupture parallel phyllosilicate rich surfaces within the host rock fabric with possible additional contributions from elevated pore fluid pressures

the environmental seismic intensity scale esi 2007 in greece addition of new events and its relationship with magnitude in greece and the mediterranean preliminary attenuation relationships abstract the environmental seismic intensity esi scale has been officially released in 2007 and is based on the quantification of earthquake environmental effects due to its quantitative nature the scale improves the process of assessing macroseismic intensities particularly in the epicentral area of those cases in which sole traditional intensity scales prove to be ineffective following a large number of publications that applied this relatively newly established scale there is some need for parametrization this is because this intensity scale can offer new insights to seismic hazard assessment and has the potential to reduce the uncertainties that stem from traditional macroseismic scales this study has three main goals firstly to enrich and compile an esi 2007 database from earthquakes in greece by adding 4 new events secondly to extract a relationship between magnitude and the esi 2007 for greece and the mediterranean thirdly to offer a preliminary estimate of how the intensity attenuates with distance after developing a code in python language to assist this process the esi 2007 scale was applied in the 1995 ms 6 6 kozani grevena earthquake the 1978 mw 6 5 thessaloniki earthquake the historic 1894 atalanti earthquake sequence m 6 4 and m 6 8 and the 365ad event in crete m 8 4 these events were selected because they have well documented and extensive co seismic effects including primary and secondary surface ruptures rockfalls landslides and liquefaction phenomena for the kozani earthquake extracted results were correlated with sar interferograms in order to provide a complete and high spatial resolution of the ground deformation both the kozani grevena and the thessaloniki events produced a maximum intensity ix on the esi 2007 scale the atalanti earthquake produced a maximum intensity x and the 365ad crete earthquake a maximum intensity xii overall the esi 2007 scale compares fairly well with the traditional macroseismic scales except for some villages in the kozani grevena epicentral area where due to the poor quality of buildings existing scales overestimated the intensity by one degree compared to the esi 2007 it is interesting to note that both for greece and the mediterranean area a strong correlation exists between mw and the esi 2007 scale in particular the following relationships between the mw and the esi scale have been extracted i for greece io esi 2007 3 1427 exp 0 1643mw and ii for the mediterranean io esi 2007 3 3543exp 0 1557mw however more events and more data regarding the intensity distributions are required to establish the intensity attenuation with distance

landscape responses to intraplate tectonism quantitative constraints from be 10 nuclide abundances cosmogenic 10 be concentrations in bedrock and alluvium combined with structural studies provide a novel approach for identifying neotectonic forcing of landscape evolution in mildly deforming continental interiors measured 10 be concentrations in the flinders ranges indicate rapid and spatially variable rates of bedrock erosion in a catchment that has incurred at least three large surface rupturing earthquakes since 67 ka 10 be derived erosion rates are lower where late quaternary neotectonic activity is reduced or absent implying that 10 be concentration may act as a tracer for disequilibrium landscapes responding to recent tectonism mechanisms for elevated erosion rates include 1 headward migration of fault generated bedrock knickpoints and resultant oversteepening of stream profiles and catchment hillslopes and 2 liberation of bedrock material from catchment hillslopes via co seismic shaking despite climatic influences on sediment production and transport this study shows that tectonism can provide a dominant control on bedrock erosion rate and relief production in unglaciated mountain belts even in intraplate settings where rates of crustal deformation are mild and earthquake activity is episodic 2007 elsevier b v all rights reserved

physical constraints on speleothem deformations caused by earthquakes seen from a new perspective implications for paleoseismology abstract fractured speleothems important earthquake environmental effects used in paleoseismological studies worldwide are particularly effective for dating here we discuss physical phenomena that can damage caves we supplement the discussion with information frequency characteristics and ground motion parameters from areas of mine openings threatened by induced seismicity as analogs of cave conduits as both from a physical point of view are underground voids affected by oscillations theoretical considerations indicate the use of bulk p wave and shear s wave moduli instead of young s modulus depending on the type of seismic wave affecting a given speleothem application of p wave and shear moduli enables the calculation of a speleothem s natural frequency based on measured p and s wave velocities as well as on the height and diameter of the speleothem the relationship between the natural frequency the acceleration causing speleothem failure and the height and diameter of speleothems has been determined moreover this acceleration value was compared to expected pga values in order to find similarities between the two acceleration values we highlight a phenomenon not previously considered in relation to cave environments i e tunnel waves which can appear in cave walls this effect significantly changes oscillation characteristics in a cave which can result in damage to speleothems which had not been expected to fail finally we present the potential for estimating the minimum magnitude required to damage a cave at a given distance from its source

rheology of the lower mantle abstract the rheology of the lower mantle of the earth is examined from the viewpoint of solid state physics recent developments in high pressure research suggest that the lower mantle contains a considerable amount of mg fe o with fe mg fe 0 2 0 3 the pressure and temperature dependences of diffusion in mg fe o are estimated by the theory of diffusion in ionic solids of the materials composing the lower mantle mg fe o may be the softest and therefore the rheology of the lower mantle may be that of mg fe o unless the framework effect is important temperatures in the lower mantle are inferred from the depths of phase transitions and the melting temperatures of the core materials a thermal boundary layer at the base of the mantle is suggested the physical mechanisms of creep are examined based on a grain size stress relation and non newtonian flow is shown to be the dominant flow mechanism in the earth s mantle the effective viscosity for the temperature models with and without the thermal boundary layer is calculated for constant stress and constant strain rate with depth for constant strain rate which may be appropriate for discussing the mechanics of descending slabs the increase in effective viscosity with depth is smaller than for the constant stress case which may be appropriate for discussing the flow induced by the surface motion of plates the relatively small depth gradient of viscosity for constant strain rate suggests that the lower mantle could also participate in convection the effective viscosity increases with depth however by at least 10 2 to 10 3 from the top to the bottom of the lower mantle for a reasonable range of activation volumes and temperatures there will be a low viscosity layer at the base of the mantle in contrast to the high viscosity layer at the top of the mantle plates if a thermal boundary layer is present the constant newtonian viscosity inferred from rebound data may be an apparent feature resulting from the difference in deformation mechanisms between isostatic rebound and large scale flow

generalized terrain topography in radar scattering models modeling of terrain topography is crucial for vegetated areas given that even small slopes impact and alter the radar wave interactions between the ground and the overlying vegetation current missions either exclude pixels with large topographic slopes or disregard the terrain topography entirely potentially accumulating substantial modeling errors and therefore impacting the retrieval performance over such sloped pixels the underlying terrain topography needs to be considered and modeled to obtain a truly general and accurate radar scattering model in this paper a flexible and modular model is developed the vegetation is considered by a multilayered multispecies vegetation model capable of representing a wide range of vegetation cover types ranging from bare soil to dense forests the ground is incorporated with the stabilized extended boundary condition method allowing the representation of an n layered soil structure with rough interfaces terrain topography is characterized by a 2 d slope with two tilt angles alpha beta simulation results for an evergreen forest show the impact of a 2 d slope for a range of tilt angles a 10 circ tilt in the plane of incidence translates to a change of up to 15 db in hh 10 db in vv and 1 5 db in hv for the total radar backscatter terrain topography is shown to be crucial for accurate forward modeling especially over forested areas

intensity estimation for the 2001 bhuj earthquake india on esi 07 scale and comparison with historical 16th june 1819 allah bund earthquake a test of esi 07 application for intraplate earthquakes abstract on 26th january 2001 an earthquake of magnitude mw 7 7 occurred near bhuj in northwestern india resulting in severe environmental effects no unequivocal primary surface rupture was observed for the earthquake but it caused widespread liquefaction and lateral spreading in the rann of kachchh and little rann after the earthquake several researchers collected field evidence of secondary surface rupture rockfall dry craters and surface manifestations of liquefaction including the formation of mud volcanoes and lateral spreads in the meizoseismal area analysis of pre and post earthquake satellite images suggests that several dry streams in the rann of kachchh began to flow due to extensive liquefaction induced by the earthquake in this present study the macroseismic intensity of the bhuj earthquake is evaluated by considering these environmental effects and applying the esi 07 intensity scale to the affected area as an outcome the epicentral intensity of the 2001 bhuj earthquake was determined to be xi according to historical records and seismic catalogs 16th june 1819 allah bund earthquake caused prominent surface rupture which was not so clear in the case of 2001 bhuj earthquake but the secondary effects were similar for both earthquakes considering the environmental effects caused by the 1819 allah bund earthquake an intensity of xi was estimated for the epicentral area for both earthquakes the esi scale yields a significant difference of one to two degrees with the traditional intensity scales the 2001 bhuj earthquake and 1819 allah bund earthquake shows similar esi 07 intensity of xi despite of different epicentral locations this implies the reliability of esi 07 scale application for different earthquakes of similar dimensions in the same geological setting this study contributes to the application of esi 07 scale for indian earthquakes especially reverse faulting events and to the future improvement of the esi scale with emphasis on its applicability to historical earthquakes on the indian subcontinent also this study may help in future land use planning in the meizoseismal area of 1919 allah bund and 2001 bhuj earthquakes

mid continental earthquakes spatiotemporal occurrences causes and hazards abstract large earthquakes in north china australia northwestern europe central and eastern united states and other mid continents show complex spatiotemporal patterns that do not fit existing earthquake models individual faults or fault zones tend to fall into long term thousands of years or longer dormancy after a cluster of ruptures whereas large earthquakes seem to roam between widespread faults these behaviors are characteristic of complex dynamic systems of interacting faults in such systems widespread faults collectively accommodate slow tectonic loading and a major fault rupture both transfers stress to the neighboring faults and perturbs loading conditions on distant faults because of the slow tectonic loading local stress variations from fault interaction or nontectonic processes or changes of fault strength could trigger mid continental earthquakes the precise spatiotemporal occurrence of large mid continental earthquakes may be unknowable an intrinsic limitation of complex dynamic systems but their qualitative system behavior may be understood by a system approach this approach would render some commonly used concepts such as seismic cycles recurrence intervals characteristic earthquakes and seismic gaps inadequate or irrelevant in mid continents and calls for rethinking of the probability estimates based on these concepts it requires a better understanding of fault interactions on multiple spatial and temporal scales rather than focusing solely on the balance of tectonic loading and yield strength of individual faults or fault segments it also indicates the need for paleoseismic and geodetic studies extending beyond areas where recent large earthquakes occurred and for hazard assessments to reduce the biasing influence of the most recent large earthquakes that tend to dominate the short and incomplete earthquake records

viscosity of the earth s mantle inference from dynamic support by flow stress abstract in this study the viscosity is estimated from a new and different point of view the plates with various dip angles and penetration depths are descending into the mantle at many locations around the world since these descending slabs are affected by viscous flow negative buoyancy forces in the slabs and other effects some information about the viscosity can be obtained through the balance of torques exerted on the slabs a model is constructed on the basis of the corner flow treatment for a given viscosity model the stress exerted normal to the slab by the flow is calculated from the balance of torques by this stress the negative buoyancy force and the bending moment the dip angles of the descending slabs are calculated by the comparison between these calculated angles and the observed angles better viscosity models are selected the viscosity distribution obtained here consists of a low viscosity layer with a thickness of about 100 km and a viscosity of about 10 20 p poises an intermediate viscosity layer with about 10 22 p viscosity and either a highly viscous 10 24 p or more layer around 700 km depth or the highly viscous lower mantle

enhanced intraplate seismicity along continental margins some causes and consequences abstract in australia much of the seismic activity is restricted to zones up to several hundred kilometres wide inboard of continental margins at high angle to the trend in maximum horizontal compression shmax intriguingly along the margin side of one such zone a near optimally oriented crustal scale structure the darling fault has no recorded historical seismicity to explain these enigmatic features we explore how the compositional and thermal structuring of continental passive margins may lead to variations in mechanical response to imposed forcing using forward modelling we show how lateral heat flow across such margins can produce increases in moho temperatures by several 10s of degrees relative to the continental interior extending up to 200 km inboard of the ocean continent transition provided the step in thermal lithosphere thickness into the continent is greater than 30 km for smaller lithospheric steps moho temperatures beneath continental margins will be cooler than beneath interiors our mechanical models show that such thermal effects can elevate strain rates along the margin by several factors relative to continental interiors when subject to far field forcing in the shallow seismogenic realm the strain rate maximum is concentrated at around 100 150 km inboard of the ocean to continent lithospheric step providing a plausible explanation for the pattern of seismicity observed in some of australia s marginal seismic zones this interpretation requires that strength changes associated with moho temperature variations of several 10s of degrees are sufficient to override the reactivation potential of near optimally oriented crustal penetrative structures with thermal processes providing an important switch controlling reactivation potential of existing structures it also provides an insight into the mechanism of formation of continental ribbons during rifting of thermally mature margins

a numerical model of coupled subcontinental and oceanic convection abstract at least two different types of convection should exist in the earth s mantle a large scale flow which is revealed by the creation and subduction of oceanic crust and a circulation of unknown scale under the continents which does not approach the surface the effects of these coexisting and interacting modes on mantle dynamics and thermal regime are investigated by means of a finite element model system of two adjacent cells which are coupled thermally and mechanically at their interface an a priori viscosity distribution is applied in such a way that the surface layer of the longer cell can move with almost uniform velocity while it is immobile on the shorter cell the results suggest that the pattern of sub oceanic convection is stabilized to some extent by the frame of the highly viscous but moving lithosphere whereas convection under continents is more complex and less stable most of the sub continental heat is transferred into the oceanic cell this causes an imbalance of surface heat flow which is well in accordance with recent determinations of global heat loss distribution furthermore the model reflects at least semiquantitatively the continent ocean differences in lithospheric thickness mean topographic level and upper mantle temperatures while the average geotherms below ocean and continent diverge by up to 400 k at moderate depth they nearly coincide below 250 km depth thus giving no support for deep reaching continent ocean differences these results refer to convection penetrating the lower mantle if the circulation is confined to moderate depth the continental upper mantle is too hot compared with the oceanic however this may be due to the strict separation of the flow on either side the model results stimulate some speculations on the possible form of whole mantle convection

stress and flow beneath island arcs summary the flow pattern stress distribution topography and gravity anomalies were computed from numerical models having density and viscosity distributions resemblant to the aleutian arc the results were compatible with the hypothesis that the excess density of the slab drives its descent and that hydrodynamic forces are responsible for topographic and gravity highs over the outer rise seaward of the trench and the frontal arc and lows over the trench in models with simple distributions of rheological parameters the force from the slab was transmitted directly upward producing a negative gravity anomaly over the arc material with low resistance to flow was needed along the fault plane above the slab or within the crust of the frontal arc and within the wedge of asthenosphere above the slab to reduce that force and to allow the horizontal lithosphere to move with the slab models with the resistance to flow thus reduced had outer rises deep trenches horizontal tension seaward of the trench horizontal compression under the trench and downdip tension in the slab free air gravity anomalies which are the sum of between deflections of the free surface due to hydrodynamic forces and direct attractions from the masses driving the flow were not fit excellently by any of the models in part because the coarse grid used precluded accurate representation of the fault zone above the slab and the frontal arc an alternate to the hypothesis that about 5 kb of stress on the fault plane is needed to produce an outer rise is offered by these models shear stress between the slab and the island arc was always below 700 bars in the more successful models if the density distribution was scaled to match the topography of the trench this is much less than the 2000 bars stresses needed if frictional heating causes island arc volcanism

on the existence of a second scale of convection in the upper mantle summary this paper is concerned with an examination of the possibility that there might exist a small scale of convective circulation beneath the oceanic lithosphere recent suggestions that this might be the case have been made in an effort to understand why the bathymetry of the sea floor deviates from the prediction of boundary layer theory for ages in excess of about 100 ma the energy source which sustains the secondary motion is supposed to be found in the steep temperature gradient near the planetary surface which is itself presumably maintained by the large scale convective circulation associated with plate creation and destruction here we investigate the extent to which the temperature dependence of viscosity may act so as to stabilize the upper boundary layer against disruption by such secondary instability if the viscosity profile is monotonie and the asymptotic upper mantle viscosity is about 1022poise as suggested by post glacial rebound data then the existence of the second scale is extremely unlikely on the other hand if a sufficiently pronounced low viscosity zone does exist under old sea floor then the development of such a second scale cannot be ruled out completely some recently obtained geophysical evidence is reviewed which suggests that this is unlikely to be the case

shear modulus and q of forsterite and dunite near partial melting from forced oscillation experiments an apparatus designed to determine the complex shear modulus of rock samples by forced torsion oscillations at high temperature and in the seismic frequency band 0 003 30 hz is briefly described measurements were performed on natural dunite from aheim norway up to 1400 c and on polycrystalline forsterite up to 1500 c at 1 atm pressure the two materials were chosen to study by comparison the effect of melt on the elasticity and anelasticity of mantle rocks between 1000 and 1200 c the absolute values of the shear modulus g are almost equal for both materials above 1200 c g for natural dunite decreases progressively with temperature and at 1400 c and 1 hz reaches 13 of its value at 1100 c in contrast g of pure forsterite depends little on temperature for petrological reasons supported by simultaneous measurements of the electric resistivity there is strong evidence that the decrease of g in dunite above 1200 c is due to melt from the lower melting components of the dunite based on different models estimates of the melt fraction are made at high temperature in both materials q 1 is characterized by a monotonic decrease with frequency according to with 0 25 an apparent activation energy of 38 5 kcal mol 1 for forsterite and 48 8 kcal mol 1 for dunite was found with no significant change in the regime of partial melting from this it is concluded that q 1 even at partial melting is dominated by solid state high temperature background absorption there is no indication from these experiments for a constant q band at low seismic frequencies or an increase of q proportional to frequency as suggested by some seismologists the present results are in good qualitative agreement with those for young s modulus obtained previously by strain retardation experiments

evaluation of the macroseismic intensities triggered by the january february 2014 cephalonia greece earthquakes based on esi 07 scale and their comparison to 1867 historical event abstract on january 26th and february 3rd 2014 two earthquakes occurred onshore the island of cephalonia inducing severe environmental effects the main types of earthquake induced failures were liquefaction and slope failures and were mainly widespread at the western and central part of the island at paliki peninsula although the fact that the generated strong motions by the second event were the highest ever recorded in greece medium severity structural damages were induced few days after the occurrence of the events two post earthquake field surveys took place in order to document the generated environmental effects by taking into account these field observations it was decided to evaluate the macroseismic intensity of the february 3rd 2014 earthquake by applying the esi 07 scale as an outcome the epicentral intensity of feb 3rd 2014 was evaluated as vii esi 07 by taking into account the total affected area furthermore as it is pointed out in primary contemporary sources and seismic catalogues similar environmental failures such as liquefaction phenomena at coastal areas and large scale rockfalls were triggered by historical earthquakes at the island of cephalonia the most accurately described effects are the ones triggered by the 1867 earthquake therefore it was decided to assess the macroseismic intensities of this historical event based on the esi 07 scale and compare it with the relevant ones of feb 3rd 2014 event as an outcome it is concluded that similar intensities were assessed for both events viii esi 07 for 1867 event and vii esi 07 for the february 2014 one despite the fact that the relevant earthquake magnitudes strongly differ outlining the results of this study it is reconfirmed the importance of the recording and documentation of earthquake environmental effects in order to maintain the consistency with the historical earthquake catalogues moreover a re evaluation of historical earthquake magnitudes at the area of cephalonia island could be realized in order to accurately update the seismic hazard

advances and limitations of the environmental seismic intensity scale esi 2007 regarding near field and far field effects from recent earthquakes in greece implications for the seismic hazard assessment the new environmental seismic intensity scale esi 2007 introduced by inqua incorporates the advances and achievements of palaeoseismology and earthquake geology and evaluates earthquake size and epicentre solely from the earthquake environmental effects eee this scale is tested and compared with traditional existing scales for the 1981 alkyonides earthquake sequence in the corinth gulf ms 6 7 ms 6 4 ms 6 3 the 1993 pyrgos event ms 5 5 and the 2006 kythira event mw 6 7 these earthquakes were of different magni tudes focal mechanisms and focal depths and produced well documented environmental effects the esi 2007 intensity values and the isoseismal pattern for the 1993 pyrgos and the 2006 kythira events are similar to those resulting from the traditional scales demonstrating that for moderate intensity levels vii and viii the esi 2007 and the traditional scales comply well in contrast the 1981 alkyonides earthquake sequence shows that there is an inconsistency between the esi 2007 and the traditional scales both in the epicentral area where higher esi 2007 intensity values have been assigned and for the far field effects the esi 2007 scale offers higher objectivity in the process of assessing macroseismic intensities particularly in the epicentral area than traditional intensity scales that are influenced by human parameters the esi 2007 scale follows the same criteria environmental effects for all events and can compare not only events from different settings but also contemporary and future earthquakes with histori cal events a reappraisal of historical earthquakes so as to constrain the esi 2007 scale may prove beneficial for seismic hazard assessment by reducing the uncertainty implied in the attenuation laws which constitute one of the most important seismic hazard parameters

effects of source model variations on coulomb stress analyses of a multi fault intraplate earthquake sequence abstract fault models are quickly produced and iteratively improved over weeks to years following a major earthquake to characterise the dynamics of rupture evaluate the role of stress transfer and contribute to earthquake forecasting we model coulomb stress transfer cfs between the largest foreshock mw 5 4 1 year prior to first mainshock and three mw 6 1 to 6 5 earthquakes that occurred in a 12 hour period on january 22 1988 in central australia tennant creek earthquake sequence to investigate the role of static stress transfer in earthquake triggering relative to progressive source model development the effects of fault model variance are studied using cfs modelling of five different fault source model sequences 27 total models using different inputs from seismic and geospatial data some initial models do not yield positive cfs changes proximal to hypocentres but in all models preceding earthquakes generate positive cfs 0 1 bar on 10 to 30 of the forthcoming receiver fault rupture areas the most refined and data integrative model reveals cfs 0 7 to 13 bars within 2 km of impending hypocentres and large 30 to 99 areas of positive cfs when compared to global compilations of threshold cfs prior to impending ruptures average 3 71 bar median 1 bar this suggests that coulomb stress change theory adequately explains the tennant creek rupture sequence in the most refined model earthquake inter event times decrease as cfs increases suggesting that higher stress magnitudes may have more rapidly within hours triggered successive events thus accounting for some temporal aspects of this sequence cfs analyses provide a useful framework for understanding the spatiotemporal aspects of some intraplate earthquakes the progressive refinement of source models using emergent data may reduce epistemic uncertainties in the role of stress transfer that result from different model inputs approaches and results

structural controls on localized intraplate deformation and seismicity in southern australia insights from local earthquake tomography of the flinders ranges data from an array of 24 seismometers are used to image the crust beneath the flinders ranges southeast australia with the goal of improving our understanding of crustal structure rheology and the mechanism responsible for the localized intraplate deformation that characterizes this region a subset of p and s wave traveltimes is inverted to jointly recover earthquake hypocenters p wave velocity structure and v p v s anomalies the p wave velocity model reveals a spatial correlation between major negative velocity perturbations and concentrations of seismicity in particular a cluster of seismicity is observed within a distinct low velocity region between the archean mesoproterozoic gawler craton and the palaeo mesoproterozoic curnamona province from 7 to 20km depth we postulate that this may be associated with a pre existing structural weakness in the crust that arises primarily from rifting between the curnamona province and the gawler craton another area characterized by a high level of seismicity overlies a major sequence of n s trending ross delamerian thrust faults which correspond to a band of low v p and particularly v p v s the lack of evidence for elevated heat flows in both of these seismogenic regions suggests that thermally induced weakness is unlikely to play a dominant role instead the dynamic behavior of this intraplate region appears to be caused by a serendipitously oriented regional stress field provided by far field forces that originate from the boundary between the pacific and australian plates which acts upon preexisting structural weaknesses in the lithosphere

application of the esi 2007 scale to two large earthquakes south island new zealand 2010 mw 7 1 and tohoku japan 2011 mw 9 0 application of the esi 2007 scale is implemented by compilation of reports and quantification of the surface effects on the geological environment i e length and width of ground fractures width of lateral spreading diameter of mud sand gravel boils during two recent large earthquakes south island new zealand 3 september 2010 m w 7 1 referred to here as the new zealand earthquake nze and tohoku japan 11 march 2011 m w 9 0 referred to here as the japan earthquake jpe these two earthquakes occurred on different types of faults and in different geological and tectonic settings the npe was oblique to the alpine fault a strike slip fault segment that is part of the tectonics between the australian and pacific plates that involves compressional regime and dextral component of motion and the jpe occurred along the subduction zone between the pacific and okhotsk plates at the latitude of the japan trench from secondary information mined from various sources including reports of reconnaissance campaigns published papers satellite imagery and photographs and local reports from the affected areas a database was compiled containing surface environmental effects of the two earthquakes to determine intensity levels and to construct preliminary isoseismal maps in the case of nze intensities reached degree xi and reports were concentrated in the surroundings of the christchurch district whereas in the case of jpe reports were distributed along the tohoku and kanto regions in northeastern honshu and intensities reached degree xii the isoseismal maps constructed based solely on the environmental effects are a good complement to other estimates of intensity for both earthquakes online material reported environmental effects from new zealand and japan earthquakes

episodic post rift deformation in the south eastern australian passive margin evidence from the lapstone structural complex identifying the influence of neotectonics on the morphology of elevated passive margins is complicated in that major morpho structural patterns might plausibly be explained by processes related to late mesozoic to early cenozoic rifting and or differential erosion induced by cenozoic epeirogenic uplift the proportional contribution of each process can vary from continent to continent and potentially even within the same passive margin in the passive margin setting of the southeast australian highlands the documented occurrence of neotectonic deformation is rare and accordingly its role in landscape evolution is difficult to establish the results of investigations within the lapstone structural complex which forms the eastern range front of the blue mountains plateau provide evidence for two periods of cenozoic neotectonic uplift in this part of the highlands the first demonstrated by seismic and structural evidence is suggested to have occurred in the paleogene and is thus unrelated to cretaceous rifting the second period demonstrated by evidence from the kurrajong fault presented herein suggests that uplift occurred in both the mio pliocene and the middle pleistocene the cumulative neogene and younger uplift of 15 m determined for the kurrajong fault is less than 10 of the 130 m of total measured throw across the fault the apparently minor contribution of neotectonism to the current elevation of the blue mountains plateau supports a predominantly erosional exhumation origin for the topographic relief at the plateau s eastern edge this finding contrasts with evidence from fault complexes associated with similar topographic relief elsewhere in the south eastern highlands indicating that present day topography cannot be directly related to relief generated by neogene and younger uplift even from relatively closely spaced 150 km structures within the same passive margin these findings have implications for understanding the spatio temporal variability of post rift faulting in continental passive margin settings and the evolution of landscapes therein commonwealth of australia earth surface processes and landforms 2014 john wiley sons ltd

the australian desert dunefields formation and evolution in an old flat dry continent a new map the first based on interpretation of satellite imagery reveals both the complexityofaustralia sdunefieldsandtheirrelationshipswithtopography climateandsubstrate of the five main sand seas the mallee strzelecki and simpson in eastern australia cover quaternary sedimentary basins whereas the great victoria and great sandy dunefields in the west are formed by reworking of valley and piedmont sediments in a non basinal landscape of low relief ridge and valley topography these dunefields cover large areas of the arid zone and semi arid zone and small areas of dunes in sub humid areas around the margins of the continent reflecting past expansion of arid climates during glacial stages of the last several glacial cycles several areas of low relief stand out as being largely dune free the limestone nullarbor plain clay plains of the georgina basin and floodplains of rivers in the carpentaria lake eyre and murray darling drainage basins where sand is rare or not transported by diminished late quaternary rivers the yilgarn block of southwestern australia is also surprisingly free of dunes possibly as a result of long deep weathering everywhere the history of climate change is evident in dune morphology and distribution including large areas where the sand dune orientations are markedly divergent from modern sand moving wind directions

phase boundaries in finite amplitude mantle convection summary phase boundaries are included in dynamical finite element models of mantle convection they are represented by point chains which act as additional sources of buoyancy forces when distorted and as additional source or sink of heat the influence of the exothermic olivine spinel transition is studied in both shallow and deep convection models the flow is only slightly enhanced by the transition the increase of temperature due to latent heat release is step like in the deep model in the case of shallow convection it is more diffuse other quantities like ocean floor topography gravity anomalies and stress distribution are no more than moderately affected in a further investigation the effect of spinel post spinel transition whether endothermic or exothermic on deep convection is examined the effect on the flow is negligibly small in both cases

tectonic geomorphology of australia the australian continent is actively deforming in response to far field stresses generated by plate boundary interactions and buoyancy forces associated with mantle dynamics on the largest scale several 10 3 km the submergence of the northern continental shelf is driven by dynamic topography caused by mantle downwelling along the indo pacific subduction system and accentuated by a regionally elevated geoid the emergence of the southern shelf is attributed to the progressive movement of australia away from a dynamic topography low on the intermediate scale several 10 2 km low amplitude c 100 200 m long wavelength c 100 300 km topographic undulations are driven by 1 anomalous smaller scale upper mantle convection and or 2 lithospheric scale buckling associated with plate boundary tectonic forcing on the smallest scale 10 1 km fault related deformation driven by partitioning of far field stresses has modified surface topography at rates of up to c 170 m ma 21 generated more than 30 50 of the contemporary topographic relief between some of australia s highlands and adjacent piedmonts and exerted a first order control on long term 10 4 10 6 a bedrock erosion although australia is often regarded as tectonically and geomorphologically quiescent neogene to recent tectonically induced landscape evolution has occurred across the continent with geomor phological expressions ranging from mild to dramatic australia is one of the lowest flattest most arid and most slowly eroding continents on earth the average elevation of the continent is only c 330 m above sea level asl maximum local topographic relief is everywhere 1500 m defined by elevation ranges with 100 km radii and two thirds of the con tinent is semi arid to arid with the exception of localized upland areas in the flinders and mt lofty ranges and the eastern highlands bedrock

glacial isostatic adjustment and the free air gravity anomaly as a constraint on deep mantle viscosity summary a gravitationally self consistent theory for relative sea level variations forced by pleistocene deglaciation events is employed to explore the extent to which rsl and free air gravity observations together constrain the viscosity of the mantle beneath the seismic discontinuity at 670 km depth a trade off is revealed between errors in the assumed deglaciation history and errors in the inferred value of the viscosity of the lower mantle taking full account of such uncertainty plausible values of the viscosity beneath the transition region are bounded above by 1023 poise cgs units the preferred value is at least a factor of 2 lower than this and is strongly constrained by the observed free air gravity anomaly over hudson bay the calculations described in detail here show for the first time that the relatively large gravity anomalies observed over sites of wurm wisconsin deglaciation do not require any pronounced increase of mantle viscosity with depth in order to explain them

the muzaffarabad pakistan earthquake of 8 october 2005 surface faulting environmental effects and macroseismic intensity the mw 7 6 muzaffarabad earthquake of 8 october 2005 occurred on a lateral equivalent of the main ramp of the hymalaia frontal thrust and is the result of the collision tectonics between the indian and eurasian plates the epicentre was located near the town of basantkot muzaffarabad and the focal depth was about 13 km the muzaffarabad earthquake provides unequivocal evidence about the localization of severe damage intense ground shaking and secondary environmental effects near the surface expression of the source fault we analyse its nature and impact on man made structures and the physical environment on the basis of a detailed survey and macroseismic study of the affected areas conducted by the micro seismic studies programme mssp team ishfaq ahmad research laboratories pakistan atomic energy commission immediately after the mainshock assisted by a careful review of the subsequent data and literature in the course of the field survey the displacement and surface expression of the causative fault and accompanying secondary environmental effects were observed at a number of places along a capable thrust fault structure we refer to this structure as the kashmir thrust kt capable fault following the terminology of local research geologists in pakistan the seismological evidence of this structure is already known in the literature as the indus kohistan seismic zone a complex clearly segmented at least 112 km long surface rupture was mapped along the kt the maximum values of vertical displacement on the order of 4 to 7 m were observed mainly between muzaffarabad and balakot along the central segment of the rupture 52 km associated with maximum slip at depth and a major portion of the energy release both the nw alai segment 38 km and se bagh segment 22 km are characterized by scattered minor surface ruptures with a few centimetres of displacement accompanied by extensive surface cracking landslides and severe damage concentrated in a narrow belt along the fault trace a maximum intensity of xi on the modified mercalli intensity mmi scale and on the environmental seismic intensity scale esi 2007 was recorded in the epicentral area between muzaffarabad and balakot extremely severe damage and very important secondary environmental effects in the hanging wall adjacent to the trace of the causative fault plane are mainly due to near fault strong motion and rupture directivity effects to our knowledge this is the first study to present field observations over the whole near field of the earthquake and to include the intensity map of the entire meizoseismal region the geological society of london 2009

on some consequences and possible causes of layered mantle convection laboratory and numerical experiments are used to study convection confined to discrete layers the laboratory experiments which use the water content of a predominantly glycerine solution as a way of establishing chemical density variations show that convection will remain confined to superimposed layers when the chemical density contrast between layers is greater than the density change associated with the greatest temperature difference within the convecting system the numerical experiments show a double thermal boundary layer at the interface between layers a feature that would result in an average temperature increase of about 500 c in the mantle near 700 km depth if the lower mantle is isolated as suggested by recent geochemical models the possible causes of a layered mantle convection system include major element chemistry variations the combined effect of major element chemistry and a phase change or a phase change alone if it has a sufficiently negative clapeyron slope

stress development in heterogenetic lithosphere insights into earthquake processes in the new madrid seismic zone abstract the new madrid seismic zone nmsz in the midwestern united states was the site of several major m 6 8 8 earthquakes in 1811 1812 and remains seismically active although this region has been investigated extensively the ultimate controls on earthquake initiation and the duration of the seismicity remain unclear in this study we develop a finite element model for the central united states to conduct a series of numerical experiments with the goal of determining the impact of heterogeneity in the upper crust the lower crust and the mantle on earthquake nucleation and rupture processes regional seismic tomography data cite are utilized to infer the viscosity structure of the lithosphere which provide an important input to the numerical models results indicate that when differential stresses build in the central united states the stresses accumulating beneath the reelfoot rift in the nmsz are highly concentrated whereas the stresses below the geologically similar midcontinent rift system are comparatively low the numerical observations coincide with the observed distribution of seismicity throughout the region by comparing the numerical results with three reference models we argue that an extensive mantle low velocity zone beneath the nmsz produces differential stress localization in the layers above furthermore the relatively strong crust in this region exhibited by high seismic velocities enables the elevated stress to extend to the base of the ancient rift system reactivating fossil rifting faults and therefore triggering earthquakes these results show that if boundary displacements are significant the nmsz is able to localize tectonic stresses which may be released when faults close to failure are triggered by external processes such as melting of the laurentide ice sheet or rapid river incision

earthquake environmental effects produced by the mw 6 1 20th may 2016 petermann earthquake australia abstract earthquake environmental effects eees identified in the source region of the 20th may 2016 intraplate moment magnitude mw 6 1 petermann earthquake in central australia are described and classified using the environmental seismic intensity esi 07 scale eees include surface rupture ground fissures and cracks vegetation damage rockfalls and displaced jumped bedrock fragments the maximum esi intensity derived from eees is x consistent with previous observations from some moderate mw crustal earthquakes maximum esi isoseismals correlate with the location of the surface rupture rather than epicentre area due to the dipping geometry of the reverse source fault esi isoseismals encompass a larger area of the hanging wall than the footwall indicating stronger ground motions on the hanging wall due to increased proximity to the rupture source and ground motion amplification effects the maximum areal extent of secondary seismic shaking induced eees 300 km2 is significantly smaller than expected using the published esi 07 scale approx 5000 km2 this relates to the low topographic relief and relatively homogeneous bedrock geology of the study region which i reduced the potential for site response amplification of strong ground motions and ii reduced the susceptibility of the landscape to eee such as landsliding and liquefaction erosional degradation of the observed eee features and decreasing confidence with which they can be uniquely attributed to a seismic origin with increasing time since the earthquake highlight challenges in using many of the natural features observed herein to characterise the locations and attributes of paleo earthquakes

laboratory convection experiments effect of lateral cooling and generation of instabilities in the horizontal boundary layers convection experiments are carried out in a tank with two isothermal heat sinks the top plate and one of the sidewalls heating is supplied either by an isothermal bottom plate or by generation within the fluid this situation is similar to that of the earth s subcontinental mantle in the presence of a neighboring subducting oceanic lithosphere there the mantle material loses heat not only to the base of the continental lithosphere but also to the cold dipping oceanic slab the thermal structure of the convective fluid is observed by a variety of techniques including differential interferometry and strioscopy two parameters characterize the observations the usual vertical rayleigh number and a newly defined lateral rayleigh number the lateral cooling induces a large roll with axis parallel to the cold wall the variation of its width relative to the values of the two rayleigh numbers has been determined an application to the earth s upper mantle would predict rolls 5 times wider than high the circulation in the large roll remains two dimensional for rayleigh numbers up to about 3 104 beyond this value boundary layer instabilities are observed within the persisting large roll their period has been determined the interferometric method is shown to be very useful for visualizing other time dependent processes such as the growth of the induced large rolls this growth is rapid enough to allow us to propose the existence of such large rolls in the earth and argue that their action could have led to continental break up

one hundred years of earthquake recording in australia abstract a comprehensive new catalog of australian earthquakes has been compiled and used to review the seismicity of australia the catalog contains 27 000 events of which 17 000 are considered to be mainshocks the catalog is complete for all australian events with a magnitude greater than m l 5 5 since 1910 m l 5 since 1960 m l 4 since 1970 and m l 3 5 since 1980 it is complete for events in southern australia above m l 3 5 since 1965 and m l 2 since 1980 before the development of local magnitude scales for australia around 1990 the richter magnitude scale was generally used at 600 km a typical hypocentral distance for much of australia the richter formula overestimates magnitude by around 0 5 units thus the results in the catalogs before and after the early 1990s are potentially discrepant most well located australian earthquakes are in the southern areas of the continent where the seismometer density is greatest in general the location uncertainty of australian earthquakes is high only 60 of events are located with an uncertainty of 10 km or less this percentage is smaller for earthquakes before 1980 and before 1960 very few events were located to within 10 km the hypocentral depths of australian earthquakes range mostly between 8 and 18 km except for the southwest corner of the continent where they are typically shallower than 5 km the seismicity in some areas of australia has been steady for at least 100 yr including the southeast corner the flinders ranges and the northwest corner in contrast seismicity in the southwest corner jumped by at least a factor of 6 in the 1940s and has been steady since then much of the rest of australia is characterized by episodic seismicity these episodes begin with a period of high activity lasting 1 10 yr and they are normally associated with a large m 6 earthquake following the large earthquake there is often a period of moderate activity lasting from a few years to several decades before and after each episode is a quiescent period of low activity lasting 0 1 10 ka during which the seismicity is more than an order of magnitude lower than during the period of high activity frequency magnitude relations were calculated using events since 1970 from the new catalog gutenberg richter a and b values were calculated on an 85 km grid and maps of the probability of an earthquake of m 4 9 occurring per year were derived these results are very similar to the global seismic hazard assessment program gshap map for australia the results were used to define four large 20 000 km 2 seismogenic zones fig 1 there are also several other small zones some of which appear to reflect recent episodes while others appear to be long lived the expected number of earthquakes m 5 and m 6 strain rate and deformation rate is given for the four large zones the remainder of australia and the whole australian continent the combined estimates of strain using seismic global positioning system gps and satellite laser ranging slr data suggest east west compressive deformation across southern australia of 0 65 2 0 mm per year likely to be in the 0 5 1 0 mm per year range

a record of stable continental region earthquakes from western australia spanning the late pleistocene insights for contemporary seismicity abstract in plate boundary regions moderate to large earthquakes are often sufficiently frequent that fundamental seismic parameters such as the recurrence intervals of large earthquakes and maximum credible earthquake mmax can be estimated with some degree of confidence the same is not true for the stable continental regions scrs of the world large earthquakes are so infrequent that the data distributions upon which recurrence and mmax estimates are based are heavily skewed towards magnitudes below m w 5 0 and so require significant extrapolation up to magnitudes for which the most damaging ground shaking might be expected the rarity of validating evidence from surface rupturing palaeo earthquakes typically limits the confidence with which these extrapolated statistical parameters may be applied herein we present a new earthquake catalogue containing in addition to the historic record of seismicity 150 palaeo earthquakes derived from 60 palaeo earthquake features spanning the last 100 ka of the history of the precambrian shield and fringing extended margin of southwest western australia from this combined dataset we show that mmax in non extended scr is m7 25 0 1 and in extended scr is m7 65 0 1 we also demonstrate that in the 230 000 km 2 area of non extended scr crust the rate of seismic activity required to build these scarps is one tenth of the contemporary seismicity in the area consistent with episodic or clustered models describing scr earthquake recurrence a dominance in the landscape of earthquake scarps reflecting multiple events suggests that the largest earthquakes are likely to occur on pre existing faults we expect these results might apply to most areas of non extended scr worldwide

steady propagation of delamination events delamination of the lithospheric thermal boundary from overlying continental crust propagates laterally from the line of initiation accelerating as the sinking slab of detached lithosphere grows longer this propagation has been numerically modeled with steady state equations in a moving reference frame by matching an interior finite element solution to flexible boundary conditions which represent the mechanical and thermal response of the surroundings the form of the solution depends on the shear coupling of intruding asthenosphere to the top of the sinking slab across a thin layer of crustal material without coupling the tip of the intrusion cools and stiffens to form a wedge dividing the crust cold mode with coupling the intrusion is forced to convect and remains ductile hot mode the cold mode can propagate at all velocities the hot mode has a lower limiting velocity of 1 2 cm year but offers less resistance at higher speeds resistance to delamination includes a constant term from the buoyant crustal downwarp plus a velocity proportional term representing viscous deformation however the proportionality constant of the latter term is only weakly dependent on crust and lithosphere viscosities matching this resistance to loading lines of 100 to 800 km slabs sinking in a mantle of 1022 p velocities of 0 3 8 0 cm year are obtained changes in viscosity affect this rate but cold mode delamination is unstoppable except at continental margins or by failure in the sinking slab the surface expression of delamination is a leading outer rise followed by a submarine trough with a large negative free air anomaly which finally evolves into a 1 km plateau if crustal viscosity and velocity are both low however there is a montonic crustal uplift with no trough thus the present lack of linear supracontinental oceans does not preclude delamination at up to 4 cm year driven by slabs up to 400 km in length

long aftershock sequences within continents and implications for earthquake hazard assessment one of the most powerful features of plate tectonics is that the known plate motions give insight into both the locations and average recurrence interval of future large earthquakes on plate boundaries plate tectonics gives no insight however into where and when earthquakes will occur within plates because the interiors of ideal plates should not deform as a result within plate interiors assessments of earthquake hazards rely heavily on the assumption that the locations of small earthquakes shown by the short historical record reflect continuing deformation that will cause future large earthquakes here however we show that many of these recent earthquakes are probably aftershocks of large earthquakes that occurred hundreds of years ago we present a simple model predicting that the length of aftershock sequences varies inversely with the rate at which faults are loaded aftershock sequences within the slowly deforming continents are predicted to be significantly longer than the decade typically observed at rapidly loaded plate boundaries these predictions are in accord with observations so the common practice of treating continental earthquakes as steady state seismicity overestimates the hazard in presently active areas and underestimates it elsewhere

estimation of the epicentral area of the 1912 acambay earthquake m 6 9 mexico determined from the earthquake archaeological effects eae and the esi07 macroseismic scale abstract earthquake environmental effects describe the geological features of an earthquake including the surface faulting ground cracks soil liquefaction and landslides among others historical large earthquakes could be classified according to the eee macroseismic geological scale esi07 with the advantage that it is possible to compare different earthquakes which have occurred in different places and estimate the parameterization of their seismogenic sources hence we have determined the esi07 scale by the eee description of the geological effects observed during the 1912 acambay earthquake which took place in the central basin of mexico additionally we have estimated the epicentral area of this earthquake the total rupture length and the potential seismicity of the acambay tixmadeje fault zone furthermore we have estimated the earthquake archaeological effects eaes of the oriented damage to do this we have modelled the s wave travelling by assuming different epicentre locations at several active fault segments and thus we have compared with the oriented damage mapped by urbina and camacho 1913 at different villages therefore we propose a model of rupture of 1912 acambay earthquake releasing a m 7 earthquake and with the epicentre located at tixmadeje this rupture model implies earthquake directivity towards east and the s wave travelling towards south the total rupture length was estimated 33 km and the maximum coseismic offset 52 cm

the earthquake potential of the new madrid seismic zone the fault system responsible for new madrid seismicity has generated temporally clustered very large earthquakes in a d 900 100 years and a d 1450 150 years as well as in 1811 1812 given the uncertainties in dating liquefaction features the time between the past three new madrid events may be as short as 200 years and as long as 800 years with an average of 500 years this advance in understanding the late holocene history of the new madrid seismic zone and thus the contemporary tectonic behavior of the associated fault system was made through studies of hundreds of earthquake induced liquefaction features at more than 250 sites across the new madrid region we have found evidence that prehistoric sand blows like those that formed during the 1811 1812 earthquakes are probably com pound structures resulting from multiple earthquakes closely clustered in time or earthquake sequences from the spatial distribution and size of sand blows and their sedimentary units we infer the source zones and estimate the magnitudes of earth quakes within each sequence and thereby characterize the detailed behavior of the fault system it appears that fault rupture was complex and that the central branch of the seismic zone produced very large earthquakes during the a d 900 and a d 1450 events as well as in 1811 1812 on the basis of a minimum recurrence rate of 200 years we are now entering the period during which the next 1811 1812 type event could occur

paleoseismicity of two historically quiescent faults in australia implications for fault behavior in stable continental regions paleoseismic studies of two historically aseismic quaternary faults in australia confirm that cratonic faults in stable continental regions scr typically have a long term behavior characterized by episodes of activity separated by quiescent intervals of at least 10 000 and commonly 100 000 years or more studies of the approximately 30 km long roopena fault in south australia and the approximately 30 km long hyden fault in western australia document multiple quaternary surface faulting events that are unevenly spaced in time the episodic clustering of events on cratonic scr faults may be related to temporal fluctuations of fault zone fluid pore pressures in a volume of strained crust the long term slip rate on cratonic scr faults is extremely low so the geomorphic expression of many cratonic scr faults is subtle and scarps may be difficult to detect because they are poorly preserved both the roopena and hyden faults are in areas of limited or no significant seismicity these and other faults that we have studied indicate that many potentially hazardous scr faults cannot be recognized solely on the basis of instrumental data or historical earthquakes although cratonic scr faults may appear to be nonhazardous because they have been historically aseismic those that are favorably oriented for movement in the current stress field can and have produced unexpected damaging earthquakes paleoseismic studies of modern and prehistoric scr faulting events provide the basis for understanding of the long term behavior of these faults and ultimately contribute to better seismic hazard assessments

localization of intraplate deformation through fluid assisted faulting in the lower crust the flinders ranges south australia abstract in this paper we present a hypothesis for localized intraplate deformation in the continental crust of south central australia that involves fluid assisted reactivation of faults in the mid to lower crust using data from a temporary seismometer deployment in the flinders ranges we show that earthquakes relocated in a 3d velocity model cluster in elongated low vp vs anomalies that extend to depths exceeding 20 km and are aligned with the axis of the flinders ranges in the northern flinders ranges these low vp vs anomalies can be interpreted as fractured neoproterozoic to cambrian sediments that separate two cratonic blocks the gawler craton to the west and the curnamona province in the east previous studies of helium isotopes in springs to the north of the area provide evidence of mantle derived fluids that may influence faulting at depth our focal mechanism and stress inversion results show a regionally compressive stress field that provides no evidence for stress concentration we also argue that mechanisms for localized faulting such as thermal weakening and isostatic rebound also fail to account for the occurrence of earthquakes at mid to lower crustal depth in this area of high heat flow and that the focused seismicity can only be explained by high pore fluid pressure in the lower crust

on the effects of the lithosphere on mantle convection and evolution abstract an idealized model is discussed for plate motion and mantle convection it consists of a numerical square box filled with a newtonian boussinesq fluid heated from below at the surface the fluid has a high viscosity i e it contains a stiff lid which may or may not be laterally decoupled by weakness zones lid stiffness and coupling were varied systematically only if the lid is effectively decoupled laterally does it move as a quasi rigid plate it is then driven by the lateral pressure differential from the rising and descending plumes in the fluid and it moves against viscous shear at its bottom gravitational sliding and sinking may also drive the plate if allowed for in the model a decoupled freely moving stiff plate effectively removes heat from the interior a strongly coupled stiff lid on the other hand or one with a very large aspect ratio inhibits heat transfer through the convecting layer if heating occurs by a given flux through the bottom or internal heat generation the internal cell temperatures become very high because the stagnant surface lid can only conduct the heat by assuming the required temperature gradient throughout its thickness since the earth is partly covered by conducting continental lids which in addition contain much of the heat sources the thermal history may be affected caution must be exercised in parameterized convection modelling in this respect the overall effect cannot easily be predicted because mantle flow and continental plates will interact the importance of mechanical decoupling for plate motion strongly calls for thorough studies of the decoupling mechanisms particularly at convergent plate boundaries bending stick slip processes and the role of volatiles

two layer mantle convection and the depletion of radioactive elements in the lower mantle only a small percentage of the mantle s total content of radioactive elements can be in the lower mantle if this region convects steadily and separately from the upper mantle recent geochemical models of a depleted upper mantle and an undepleted lower mantle are thus inconsistent with a steady thermal model involving distinct upper and lower mantle convection cells steady two layer mantle convection requires a depleted lower mantle and an undepleted upper mantle to match the observations of surface heat flow and mantle viscosity the constraint on the abundance of radioactive elements in the lower mantle depends on the existence of at least one thermal boundary layer at the upper mantle lower mantle interface with thickness comparable to that of the surface thermal boundary layer since the temperature drop across an interface boundary layer is limited by the relatively small difference between the solidus temperature and the upper mantle temperature the amount of heat which can be transferred across this layer is small compared with the surface heat flow the upper limit on the concentration of radioactive elements in the lower mantle can be relaxed only if both the lower boundary layer of the upper mantle cell and the upper boundary layer of the lower mantle cell are extremely thin or absent altogether which we consider however highly unlikely

cosmogenic exposure and erosion history of australian bedrock landforms exceptionally high activities of in situ produced 1 0 be and 2 6 al indicate that australian bedrock surfaces are some of the most stable in the world these cosmogenic nuclides demonstrate that australian granite exposed and sampled at 10 sites along a transect from the eyre peninsula 33 s to the kakadu area in the northern territory 14 s has in some places eroded only decimeters over the past million years however nuclide activities are not saturated in any of the 61 exposed samples we analyzed mandating that the surfaces we sampled are losing mass albeit slowly over time such mass loss indicates that inselbergs are dynamic landforms confounding the assignment of discreet ages to inselberg surfaces nevertheless the differential between slow rates of erosion measured on the very stable uppermost parts of these landforms and the more rapid rates measured below their flanks and below the adjacent grus covered planes suggests that the forms of many large inselbergs which stand meters to tens of meters high must be at least tertiary in age and possibly much older activities of 1 0 be and 2 6 al in 61 exposed australian samples range from 5 1 0 1 10 6 to 5 3 0 6 x 10 5 atoms g 1 and 2 1 0 1 x 10 7 to 3 4 0 5 x 10 6 atoms g 1 respectively normalized to sea level at latitudes of 60 using only neutron scaling activities of 1 0 be and 2 6 al in seven shielded samples 3 5 13 m below the surface are much lower ranging from 3 4 0 2 x 10 4 to 7 0 0 1 x 10 4 atoms g 1 and 1 6 0 1 x 10 5 to 2 8 0 2 x 10 5 atoms g 1 respectively 2 6 al 1 0 be ratios of exposed samples range from 3 89 0 19 to 6 29 0 82 if 2 uncertainty ranges and a nominal sea level high latitude 1 0 be production rate of 5 17 atoms g 1 yr 1 are considered ratio data for all but one surface sample are consistent with continuous surface or near surface exposure and or erosion rock surfaces farther north in australia where the climate is more humid have lower nuclide activities thus we infer that surface stability is inversely related to mean annual precipitation from 61 exposed samples we calculated maximum limiting single nuclide model erosion rates of 0 3 0 1 to 5 7 1 0 m m y and minimum limiting single nuclide model exposure ages of 105 16 to 1310 190 ka by assuming a sea level high latitude 1 0 be production rate of 5 17 atoms g 1 yr 1 seven shielded samples in which the nuclide inventory is muon generated also have nuclide activities consistent with similarly low rates of erosion but over even longer time scales it appears that the eyre peninsula inselbergs have been and are eroding so slowly that they may well be direct descendents of cenozoic and perhaps even mesozoic forms

earthquake hazard and the environmental seismic intensity esi scale the main objective of this paper was to introduce the environmental seismic intensity scale esi a new scale developed and tested by an interdisciplinary group of scientists geologists geophysicists and seismologists in the frame of the international union for quaternary research inqua activities to the widest community of earth scientists and engineers dealing with seismic hazard assessment this scale defines earthquake intensity by taking into consideration the occurrence size and areal distribution of earthquake environmental effects eee including surface faulting tectonic uplift and subsidence landslides rock falls liquefaction ground collapse and tsunami waves indeed eees can significantly improve the evaluation of seismic intensity which still remains a critical parameter for a realistic seismic hazard assessment allowing to compare historical and modern earthquakes moreover as shown by recent moderate to large earthquakes geological effects often cause severe damage therefore their consideration in the earthquake risk scenario is crucial for all stakeholders especially urban planners geotechnical and structural engineers hazard analysts civil protection agencies and insurance companies the paper describes background and construction principles of the scale and presents some case studies in different continents and tectonic settings to illustrate its relevant benefits esi is normally used together with traditional intensity scales which unfortunately tend to saturate in the highest degrees in this case and in unpopulated areas esi offers a unique way for assessing a reliable earthquake intensity finally yet importantly the esi scale also provides a very convenient guideline for the survey of eees in earthquake stricken areas ensuring they are catalogued in a complete and homogeneous manner

coseismic surface deformation caused by the 23 march 2012 mw 5 4 ernabella pukatja earthquake central australia implications for fault scaling relations in cratonic settings abstract on 23 march 2012 at 09 25 utc an m w 5 4 earthquake occurred in the eastern musgrave ranges of north central south australia near the community of ernabella pukatja several small communities in this remote part of central australia reported the tremor but there were no reports of injury or significant damage this was the largest earthquake recorded on mainland australia in the past 15 years and resulted in the formation of a 1 6 km long surface deformation zone that included reverse fault scarps with a maximum vertical displacement of more than 0 5 m extensive ground cracking and numerous rock falls the earthquake occurred in nonextended stable continental region scr cratonic crust more than 1900 km from the nearest plate boundary surface deformation from the ernabella earthquake provides additional constraint on relations of surface rupture length to earthquake magnitude such relations aid in interpreting australia s rich record of prehistoric seismicity and contribute to improved estimates of scr seismic hazard worldwide based upon an analysis of new and reinterpretation of existing surface rupture length data faults in nonextended stable cratonic australia appear to produce longer surface ruptures for earthquakes larger than m w 6 5 than rupture lengths estimated using existing moment to rupture length scaling relations the implication is that the estimated maximum or characteristic magnitude of paleoearthquakes in such settings may be overestimated where the estimate is based only on the length of the prehistoric fault scarp

the 2010 2011 canterbury earthquake sequence environmental effects seismic triggering thresholds and geologic legacy abstract seismic shaking and tectonic deformation during strong earthquakes can trigger widespread environmental effects the severity and extent of a given effect relates to the characteristics of the causative earthquake and the intrinsic properties of the affected media documentation of earthquake environmental effects in well instrumented historical earthquakes can enable seismologic triggering thresholds to be estimated across a spectrum of geologic topographic and hydrologic site conditions and implemented into seismic hazard assessments geotechnical engineering designs palaeoseismic interpretations and forecasts of the impacts of future earthquakes the 2010 2011 canterbury earthquake sequence ces including the moment magnitude m w 7 1 darfield earthquake and m w 6 2 6 0 5 9 and 5 8 aftershocks occurred on a suite of previously unidentified primarily blind active faults in the eastern south island of new zealand the ces is one of earth s best recorded historical earthquake sequences the location of the ces proximal to and beneath a major urban centre enabled rapid and detailed collection of vast amounts of field geospatial geotechnical hydrologic biologic and seismologic data and allowed incremental and cumulative environmental responses to seismic forcing to be documented throughout a protracted earthquake sequence the ces caused multiple instances of tectonic surface deformation 3 events surface manifestations of liquefaction 11 events lateral spreading 6 events rockfall 6 events cliff collapse 3 events subsidence 4 events and hydrological 10s of events and biological shifts 3 events the terrestrial area affected by strong shaking e g peak ground acceleration pga 0 1 0 3 g and the maximum distances between earthquake rupture and environmental response r rup both generally increased with increased earthquake m w but were also influenced by earthquake location and source characteristics however the severity of a given environmental response at any given site related predominantly to ground shaking characteristics pga peak ground velocities and site conditions water table depth soil type geomorphic and topographic setting rather than earthquake m w in most cases the most severe liquefaction rockfall cliff collapse subsidence flooding tree damage and biologic habitat changes were triggered by proximal moderate magnitude m w 6 2 earthquakes on blind faults ces environmental effects will be incompletely preserved in the geologic record and variably diagnostic of spatial and temporal earthquake clustering liquefaction feeder dikes in areas of severe and recurrent liquefaction will provide the best preserved and potentially most diagnostic ces features rockfall talus deposits and boulders will be well preserved and potentially diagnostic of the strong intensity of ces shaking but challenging to decipher in terms of single versus multiple events most other phenomena will be transient e g distal groundwater responses not uniquely diagnostic of earthquakes e g flooding or more ambiguous e g biologic changes preliminary palaeoseismic investigations in the ces region indicate recurrence of liquefaction in susceptible sediments of 100 to 300 yr recurrence of severe rockfall event s of ca 6000 to 8000 yr and recurrence of surface rupturing on the largest ces source fault of ca 20 000 to 30 000 yr these data highlight the importance of utilising multiple proxy datasets in palaeoearthquake studies the severity of environmental effects triggered during the strongest ces earthquakes was as great as or equivalent to any historic or prehistoric effects recorded in the geologic record we suggest that the shaking caused by rupture of local blind faults in the ces comprised a worst case seismic shaking scenario for parts of the christchurch urban area moderate m w blind fault earthquakes may contribute the highest proportion of seismic hazard be the most important drivers of landscape evolution and dominate the palaeoseismic record in some locations on earth including locations distal from any identified active faults a high scientific priority should be placed on improving the spatial extent and quality of off fault shaking records of strong earthquakes particularly near major urban centres