a framework for karst ecohydrology ecohydrology can be defined as the science of integrating hydrological and biological processes over varied spatial and temporal scales there exists in karst a strong and direct interaction between the circulation and storage of groundwater and surface water these fluxes in turn affect the spatial distribution of organisms in these habitats because of the fact that the appearance storage and circulation of water in karstified areas is significantly different from other more homogenous and isotropic terrains karst ecohydrology should develop original methods and approaches at the same time traditional approaches are also very useful large karst underground geomorphological patterns occur in many sizes and varieties ranging from a few meters long or deep to very large the deepest being deeper than 1km and longer than hundreds of kilometres in this article special attention is paid to ecohydrological functions of karst underground features caves pits conduits etc which play a crucial dual role in 1 hydrology and hydrogeology of water circulation and storage and 2 ecology of many rare and endangered species differences in morphology hydrology hydrogeology and climate have resulted in a range of different environments which provide the opportunity for the coexistence of different species the role of the epikarst and vadose zones as well as caves in ecohydrological processes is discussed the importance of the flood factor in karst ecology is analysed the aim of this article is to move forward the discussion among different disciplines to promote and develop a conceptual framework for karst ecohydrology

cadomian terranes wrench faulting and thrusting in the central europe variscides geophysical and geological evidence sixty five per cent of the paleozoic basement of western and central europe is hidden by a sedimen tary cover and or sea this work aims to remove that blanket to detect new structures which could used to build a more comprehensive model of the variscan or ogeny it is based on the interpretation of various forms of data a published gravity maps corrected for the ef fects of the crust mantle boundary topography and light sedimentary basins b aeromagnetic maps c measurements of densities and d induced and rema nent magnetizations on rocks from paleozoic outcrops of the upper rhenish area from the northern b ohem ian massif to the eastern paris basin the saxothurin gian is characterized by a 500 km long belt of gravity highs the most important being the kraichgau high most of the corresponding heavy bodies are buried un der a post early visdan cover they are interpreted as relics of late proterozoic terranes overlain by an early to middle paleozoic sequence equivalent to the bo hemian t errane in the bohemian massif the most probable continuation of these dense bohemian ter ranes toward the west is the southern channel north ern brittany cadomian terrane the gravity lows are correlated with variscan granites and pre and early variscan metagranites gravity and magnetic maps demonstrate large scale displacement in devonian early carboniferous times along the parallel and equidistant nw se striking vistula elbe bavarian bray and south armorican dextral wrench faults in the vosges schwarzwald and central massif the faults continue with the east west striking lalaye lubine ba den baden and marche faults and with south vergent thrusts the bavarian faults shift the kraichgau terrane by 150 km relative to the bohemian terrane whereas the offset of the north ern brittany cadomian relative to the northern vosges kraichgau terranes is estimated at 400km along the bray fault sinistral wrench faults are the ne sw striking sillon houiller rheingraben rodl vitis and diendorf faults the southern vosges schwarzwald devonian dinanti an basin is interpreted as a pull apart basin at the south easterly extremity of the bray fault the bohemian and kraichgau body form allochthonous terranes which were thrust over the saxothuringian crust thrusting to the north west was accompanied by back thrusting and led to the forma tion of pop up structures contemporaneous dextral and sinistral wrench faulting resulted in transpressive strain during collision the zonal structure of the varis cides in the sense of kossmat 1927 is relevant only to the rhenohercynian foreland belt kossmat 1927 al ready spoke of a moldanubian region because it dis plays no real zonal structure the saxothuringian zone was formed by terrane accretion their apparent zonal structure is not a pre collisional feature but only the result of accretion and collision

statistical analysis of the induced basel 2006 earthquake sequence introducing a probability based monitoring approach for enhanced geothermal systems summary geothermal energy is becoming an important clean energy source however the stimulation of a reservoir for an enhanced geothermal system egs is associated with seismic risk due to induced seismicity seismicity occurring due to the water injection at depth have to be well recorded and monitored to mitigate the seismic risk of a damaging event an appropriate alarm system needs to be in place for each individual experiment in recent experiments the so called traffic light alarm system based on public response local magnitude and peak ground velocity was used we aim to improve the pre defined alarm system by introducing a probability based approach we retrospectively model the ongoing seismicity in real time with multiple statistical forecast models and then translate the forecast to seismic hazard in terms of probabilities of exceeding a ground motion intensity level one class of models accounts for the water injection rate the main parameter that can be controlled by the operators during an experiment by translating the models into time varying probabilities of exceeding various intensity levels we provide tools which are well understood by the decision makers and can be used to determine thresholds non exceedance during a reservoir stimulation this however remains an entrepreneurial or political decision of the responsible project coordinators we introduce forecast models based on the data set of an egs experiment in the city of basel between 2006 december 2 and 8 approximately 11500 m 3 of water was injected into a 5km deep well at high pressures a six sensor borehole array was installed by the company geothermal explorers limited gel at depths between 300 and 2700 m around the well to monitor the induced seismicity the network recorded approximately 11200 events during the injection phase more than 3500 of which were located with the traffic light system actions where implemented after an ml 2 7 event the water injection was reduced and then stopped after another ml 2 5 event a few hours later an earthquake with ml 3 4 felt within the city occurred which led to bleed off of the well a risk study was later issued with the outcome that the experiment could not be resumed we analyse the statistical features of the sequence and show that the sequence is well modelled with the omori utsu law following the termination of water injection based on this model the sequence will last 31 29 14 years to reach the background level we introduce statistical models based on reasenberg and jones and epidemic type aftershock sequence etas models commonly used to model aftershock sequences we compare and test different model setups to simulate the sequences varying the number of fixed and free parameters for one class of the etas models we account for the flow rate at the injection borehole we test the models against the observed data with standard likelihood tests and find the etas model accounting for the on flow rate to perform best such a model may in future serve as a valuable tool for designing probabilistic alarm systems for egs experiments

empirical ground motion attenuation relations for the eastern alps in the magnitude range 2 5 6 3 in this paper we use a large data set of seismometric and accelerometric recordings 3168 vertical and 1402 for each of the horizontal components collected by various networks in the eastern alps to estimate empirical ground motion attenuation relations valid in the magnitude range 2 5 6 3 for distances of up to 130 km relations are developed for horizontal and vertical peak ground acceleration and velocity arias intensity response spectral acceleration and fourier amplitude for 46 periods between 0 1 and 2 sec we adopt a simple magnitude dependent attenuation model predicting closer attenuation curves and decreasing distance attenuation for increasing magnitude we use truncated regression analysis to deal with the problem of non triggering stations with respect to other approaches our solution does not require any discarding of data or the knowledge of which stations did not trigger our relations agree with others suitable for the study region for magnitudes greater than 5 8 while they have a faster attenuation for lower magnitudes in an attempt to reduce the standard deviation we have introduced soil classification into the relation as well as a characterization of sites by means of h v ratios these ratios were estimated either by earthquakes receiver function or by the background seismic noise nakamura s ratios similar to findings in other studies the improvement obtained with soil classification is negligible while h v ratios reduce the standard deviation by up to 22 finally we have investigated the implications of these new relations for seismic hazard assessment considering two sites of interest located in northeastern italy udine and gemona in both cases the difference in the hazard estimates for return periods shorter than 100 years is notable with respect to all other available relations

a 3 d study of the effects of thermomechanical loads on fracture slip in enhanced geothermal reservoirs heat extraction from enhanced geothermal systems egs can greatly affect the behavior of joints and other discontinuities in the reservoir fracture permeability can change in response to fluid injection extraction rock cooling variations of stress field and mineral dissolution precipitation the reduction in effective stress caused by pore pressure increase can cause the slippage of discontinuities thus inducing seismicity studies have shown that thermal stresses generated by cold water injection have a similar effect in order to assess the influence of thermal stresses on fracture opening and slippage a 3 d coupled heat extraction thermal stress elastic displacement discontinuity model is used in this study the effects of each mechanism on fracture slip is estimated with particular reference to the coso geothermal field the results indicate that under typical field conditions a substantial increase in fracture slip is observed when thermal stresses are taken into account the temporal evolution of the thermal stresses suggests that the rock mass deformation will not cease upon stoppage of water injection which can be a cause of delayed seismic activity

building robust models to forecast the induced seismicity related to geothermal reservoir enhancement abstract near real time seismicity forecasting is critically important for decision making during the reservoir creation phase of enhanced geothermal systems egs to compute within a probabilistic framework the seismic hazard and risk posed by induced seismicity it is necessary to calibrate robust forecast models quantitatively assess their reliability and capture the uncertainty of the process here we test the performance of three model classes each forecasting the induced seismicity observed during the failed 2006 2007 egs reservoir creation underneath basel switzerland each model class represents a logic tree branch that captures the epistemic uncertainty of the process the aleatory variability is accounted for by bootstrapping of the observed seismicity we calibrate each model using a range of updating strategies and quantitatively test the performances of the models using likelihood tests we then define a combined model based on akaike weights and show that the combined model outperforms in our pseudoprospective testing environment all of the individual models we also show that seismicity recorded during the initial one to three days of seismicity several days before the onset of felt seismicity is sufficient for deciding with confidence that the prescribed injection regime will eventually lead to unacceptably high levels of seismicity

constraints on the near distance saturation of ground motion amplitudes for small to moderate induced earthquakes abstract the accurate modeling of ground motion for induced seismicity hazard estimation is critically dependent on how amplitudes scale with distance near the hypocenter a rich database of ground motions from small events recorded at close distances in the geysers region of california has been used to constrain the near distance saturation effects that control the maximum observed ground motions and intensities for shallow induced events the results of this study support the modeling of these effects using an equivalent point source concept in which the effective source depth increases from a value near 1 km at moment magnitude m of 2 to a value near 3 km at m 4 this near distance saturation behavior can be applied to the development of ground motion models for induced seismicity in any region

little river revisited thirty five years after hack and goodlett abstract in possibly the first detailed study to relate geomorphology vegetation and hydrology at a watershed scale hack and goodlett 1960 documented variation in the eastern forest with topograhic positions of cove side slope and nose runoff identified as convergent parallel or divergent supported forest types respectively of northern hardwood oak and yellow pine the study conducted in the little river basin of northwestern virginia also described effects on landforms and vegetation of a catastrophic flood that occurred in june 1949 field investigations conducted nearly 4 decades later review selected parts of the study by hack and goodlett 1960 replicate data provide a basis to evaluate interpretations of hack and goodlett to document geomorphic change within the little river basin since the 1949 flood and to identify vegetation change in uplands and bottomlands results suggest that change to hillslope landforms has been minor since 1949 but that changes have occurred to the little river and its tributaries seemingly during flow events of 1952 1955 and 1985 change in areal extent of forest types was not detected change in the relative abundances of dominant species may have resulted from 20th century fire suppression

ground motion prediction equation for small to moderate events at short hypocentral distances with application to induced seismicity hazards abstract the evaluation of seismic hazard from induced seismicity requires the development of ground motion prediction equations gmpes that are tuned to the key magnitude distance range for such applications i use events of m 3 6 at hypocentral distances less than 40 km drawn from the next generation attenuation west 2 nga west 2 database to develop a gmpe that accounts correctly for point source scaling in both magnitude and distance space for such events the developed gmpe is in demonstrable agreement with the nga west 2 database and with the predictions of a stochastic point source simulation model the database is sparse at close distances implying epistemic uncertainty of as much as a factor of 2 in ground motion amplitudes within 10 km of the hypocenter an important conclusion from this study is that the ground motion amplitudes for moderate induced events could be much larger near the epicenter than predicted by most of the nga west 2 gmpes the potential for large motions is a consequence of the shallow depth of induced events which places the earthquake fault only a short distance beneath the epicenter

geomorphic and vegetative characteristics along three northern virginia streams geometry sediment and woody vegetation data were collected from bottomland geomorphic surfaces at valley sections along three gaged perennial streams of northern virginia the basins of the streams differ widely in topography and physiography mean discharges vary from 0 196 to 323 m3 per sec prevalent surfaces identified were the depositional bar the active channel shelf the flood plain and terraces the stages corresponding to active channel shelf levels were equivalent to flow durations of 5 to 13 stages corresponding to flood plain levels were equivalent to discharges with 1 4 to 2 0 yr recurrence intervals the discharge data and statistical tests of geomorphicsurface sediment and vegetative data suggest that the various alluvial features are formed and maintained by hydraulically controlled sorting processes analysis of woody plant and geomorphic data shows that each surface supports characteristic species some of which are nearly unique to a surface tests of sediment type with species distribution showed lower correlation than that of geomorphic surface with species it is inferred that plant distributions largely are controlled by flow frequency and intensity and that plants may help to identify geomorphic levels and potential for flood damage

the influence of magnitude range on empirical ground motion prediction a key issue in the assessment of seismic hazard in regions of low to moderate seismicity is the extent to which accelerograms obtained from small magnitude earthquakes can be used as the basis for predicting ground motions due to the larger magnitude events considered in seismic hazard analysis in essence the question is whether empirical ground motion prediction equations can be applied outside their strict range of applicability as defined by the magnitude and distance ranges covered by the datasets from which they are derived this question is explored by deriving new spectral prediction equations using an extended strong motion da taset from europe and the middle east covering the magnitude range mw 3 0 7 6 and comparing the predictions with previous equations derived using data from only mw 5 0 and above events the comparisons show that despite their complex func tional form including quadratic magnitude dependence and magnitude dependent attenuation the equations derived from larger magnitude events should not be extra polated to predict ground motions from earthquakes of small magnitude moreover the results suggest not only that ground motion prediction equations cannot be used outside the ranges of their underlying datasets but also that their applicability at the limits of these ranges may be questionable although only tested for smaller magni tudes the results could be interpreted to suggest that predictive equations also cannot be reliably extrapolated to higher magnitudes than those represented in the dataset from which they are derived a finding that has important implications for seismic hazard analysis the conclusion of the study is that empirical derivation of ground motion pre diction equations should be based on datasets extending at least one unit below the lower limit of magnitude considered in seismic hazard calculations the inclusion of small magnitude recordings results in a significant increase in the aleatory varia bility of the equations although it is yet to be established whether this is due to greater uncertainty in the associated metadata or whether ground motion variability is gen uinely dependent on earthquake magnitude

extreme rainfall and flooding from orographic thunderstorms in the central appalachians 1 the central appalachian region has experienced some of the largest rainfall accumulations in the world at time intervals less than 6 h including the 18 july 1942 smethport pennsylvania storm that produced 780 mm in less than 5 h the envelope curve of central appalachian flood peaks at small drainage areas less than 1000 km2 is dominated by orographic thunderstorm systems like the smethport storm orographic thunderstorm systems that have produced catastrophic flooding in the central appalachians are examined through observational and numerical model analyses using the weather research and forecasting wrf model analyses suggest that the frequency of catastrophic flooding varies over the central appalachian region and that small scale variation may be linked to the role of complex terrain in altering thunderstorm dynamics catastrophic flooding along the western margin of the central appalachians is dominated by four storms that occurred on 18 19 july 1889 1942 1977 and 1996 which were associated with warm season extratropical systems and were characterized by rapidly moving storm elements in complex terrain along the eastern margin and interior of the central appalachians catastrophic flooding is linked to four terrain locked orographic convective systems that occurred 17 18 june 1949 18 19 august 1969 27 june 1995 and 11 august 2003 wrf model simulations of the little river storm june 1949 rapidan storm june 1995 smethport storm 18 july 1942 and redbank storm 18 19 july 1996 are used to characterize ingredients of catastrophic rainstorms in the central appalachians

potential of ambient seismic noise techniques to monitor the st gallen geothermal site switzerland the failures of two recent deep geothermal energy projects in switzerland basel 2006 st gallen 2013 have again highlighted that one of the key challenges for the successful development and operation of deep underground heat exchangers is to control the risk of inducing potentially hazardous seismic events in st gallen after an injection test and two acid injections that were accompanied by a small number of micro earthquakes ml 0 2 operators were surprised by an uncontrolled gas release from the formation gas kick the killing procedures that had to be initiated following standard drilling procedures led to a ml3 5 earthquake with ambient seismic noise cross correlations from nine stations we observe a significant loss of waveform coherence that we can horizontally and vertically constrain to the injection location of the fluid the loss of waveform coherence starts with the onset of the fluid injections 4 days prior to the gas kick we interpret the loss of coherence as a local perturbation of the medium we show how ambient seismic noise analysis can be used to assess the aseismic response of the subsurface to geomechanical well operations and how this method could have helped to recognize the unexpected reservoir dynamics at an earlier stage than the microseismic response alone allowed

geomagnetic repeat station crustal biases and vectorial anomaly maps for germany summary geomagnetic repeat station data of germany from 1964 to present have been studied to determine their accuracy and crustal biases like the data from geomagnetic observatories repeat station data contain contributions from the regional and local crustal field but their spatial density is by far not high enough to resolve such anomalies knowing this crustal bias therefore is important in using repeat station data to map or model the main field to confirm the results obtained by using a global geomagnetic field model we constructed regional lithospheric field models using additional information from satellite and aeromagnetic data the compatibility of the different data types is good and we present vectorial anomaly maps for germany with a spatial resolution of approximately 37 km which could be useful for future geological interpretation of magnetic anomalies the anomalies contributing to the repeat station bias however can be of smaller scale and their amplitudes range up to absolute values of 177 nt in the north x 106 nt in the east y and 176 nt in the vertical z component average uncertainty estimates in the order of 5 8a nd 5n t inx y and z respectively are obtained from comparisons to a global model the estimates however vary a lot between stations and components the uncertainties should mostly result from measurement errors insufficient elimination of external field contributions or relocations of stations which had been regarded as insignificant there might also be a small contribution from insufficient description of secular variation in the global model used

the impacts of mechanical stress transfers caused by hydromechanical and thermal processes on fault stability during hydraulic stimulation in a deep geothermal reservoir we performed a series of 3d thermo hydro mechanical thm simulations to study the influences of hydromechanical and thermal processes on the development of an enhanced geothermal system strongly influenced by a network of short fault zones the model we developed was calibrated by comparing the simulated thm responses to field observations including ground surface deformations well pressure and microseismic activity of particular importance was the comparison between the observed temporal and spatial distribution of microseismic activity and the calculated shear reactivation of preexisting fractures inferred from simulated elasto plastic mechanical responses in the short fault zones using this approach we could identify when fault zones were reactivated as manifested in the field by a surge of local microseismic activity within the fault zone and we could back calculate the in situ stress field as being close to the stress conditions required for shear reactivation our results show that the main mechanisms of inducing seismicity are related to injection induced pressure increase and cooling during injection the reservoir expansion caused by the pressure increase led to mechanical stress transfer through the reservoir which prevented or delayed the reactivation of preexisting fractures after injection stopped there was an inversion of the mechanical stress transfers that favored shear reactivation which may explain why microseismic activity occurred after the cessation of the injection

landslide area probability density function statistics to assess historical landslide magnitude and frequency in coastal california abstract landslide area probability density function pdf statistics elucidate the landslide magnitude frequency distribution in a small coastal watershed in central california detailed mapping into a gis and compilation of two slide inventories in walker creek marin county reflect erosional effects of storms occurring in 1941 and 1998 respectively we focus on the spatial distribution and area of slides to illustrate that during both periods slides originate mainly from hillslopes underlain by franciscan complex units with slopes ranging from 10 to 40 the majority of slides 70 have areas ranging between 100 and 1000 m 2 the magnitude frequency distribution of slides represented by the pdf produces a curve that has a linear portion representing the relatively large slides the power functions of the linear portion of these curves have exponents of about 2 0 for both inventories results suggest that the storm event based pdf of landslide area developed using historical aerial images is a viable means of quantifying the landslide magnitude frequency relationship at the scale of a small watershed

a numerical model for fluid injection induced seismicity at soultz sous forets abstract during fluid injection experiments at the geothermal site of soultz sous forets france more than 114 000 induced seismic events with magnitudes between 2 0 and 2 9 were detected by a local downhole monitoring network of these 35 039 events are sufficiently constrained to be located hypocenters align along a sub vertical planar structure with the apparent width being dominated by data scattering indicating that seismic activity predominantly occurs along a pre existing larger scale fault structure for this scenario we present a numerical model to simulate hydraulic overpressures and induced seismicity during hydraulic injection the numerical model is based on the physical processes of fluid pressure and stress diffusion with triggering of the induced seismicity being controlled by coulomb friction even in its simplest form of a fault zone without any structural heterogeneity the numerical model reproduces typical observations at soultz sous forets such as number and magnitude of induced events hypocenter locations including the kaiser effect occurrence of post injection seismicity and the largest magnitude event occurring several days after shut in

comparative geomorphic analysis of surficial deposits at three central appalachian watersheds implications for controls on sediment transport efficiency abstract factors that control the routing and storage of sediments in the appalachian region are poorly understood this study involves a comparative geomorphic analysis of three watersheds underlain by sandstones and shales of the acadian clastic wedge these areas include the fernow experimental forest tucker county west virginia the north fork basin pocahontas county west virginia and the little river basin augusta county virginia gis based analyses of surficial map units allow first order approximation of sediment storage volumes in valley bottoms estimates of volumes are examined in tandem with morphometric analyses and the distribution of bedrock channels to make inferences regarding controls on sediment transport efficiency in the central appalachians the fernow and north fork areas are characterized by v shaped valleys with mixed reaches of alluvial bedrock channels distributed throughout the drainage network in contrast the little river valley is notably wider and gravelly alluvial fill is abundant comparator watershed parameters for the fernow north fork and little river areas include respectively 1 basin area 15 2 km 2 49 3 km 2 41 5 km 2 2 basin relief 0 586 km 0 533 km 0 828 km 3 drainage density 4 2 km 1 3 3 km 1 4 7 km 1 4 ruggedness 2 5 1 7 3 9 5 shreve magnitude 139 287 380 6 total valley bottom area km 2 0 76 km 2 1 86 km 2 3 09 km 2 7 average hillslope gradients 17 2 18 4 22 1 8 total debris fan surface area 0 113 km 2 0 165 km 2 0 486 km 2 and 9 debris fan frequency 2 0 km 2 1 0 km 2 2 8 km 2 the storage volumes in valley bottoms were estimated using map polygon areas and surface heights above channel grade the little river contains significantly higher sediment volumes in floodplain terrace and fan storage compartments total volumes of the valley bottoms are approximately twice that of the fernow and north fork areas combined unit storage volumes for the fernow north fork and little river are 5 2 10 4 m 3 km 2 5 5 10 4 m 3 km 2 and 1 6 10 5 m 3 km 2 respectively a conceptual model postulates that valley width morphometry and style of delivery from hillslopes are the primary factors controlling the efficiency of sediment transport steep debris flow prone hillslopes at the little river deliver high volumes of gravelly sediment at magnitudes greater than transport capacity of the channel patterns of stream power are complex as low order tributaries are under capacity and high order tributaries over capacity with respect to sediment load aggraded alluvial fill insulates valley floor bedrock from vertical erosion and valley widening dominates expansion of the valley width creates a positive response via increased storage capacity and lower unit stream power conversely the fernow and north fork are characterized by diffusive mass movement on hillslopes with incremental bedload transport to higher order tributaries rates of hillslope delivery are balanced by the rate of channel export mixed alluvial bedrock reaches provide the optimal channel configuration for active incision of the valley floor low expansion of valley width promotes high unit stream power and processes of vertical erosion the model implies that the fernow and north fork have been more effective at sediment transport during the late quaternary given similar climatic and tectonic settings variation in bedrock lithofacies is likely the primary factor modulating the efficiency of sediment transport

compatibility of high altitude aeromagnetic and satellite altitude magnetic anomalies over canada results from equivalent source distributions derived jointly from high altitude average 4 km aeromagnetic and magsat derived average 400 km magnetic anomalies over canada indicate that long wavelength components 500 2500 km in these fields are extremely compatible with one another with a correlation coefficient of 0 95 the jointly estimated anomaly field at the earth s surface can be used as a long wavelength adjustment surface for regional near surface magnetic anomaly compilations and in assessing the performance of other downward continuation techniques because near surface anomalies are not available over all regions of the world we compare the jointly estimated anomaly field to the results of two different downward continuation techniques the evaluation of anomalies at the earth s surface from spherical harmonic coefficients derived from satellite altitude data and the use of downward continuation methods based on harmonic splines numerical and visual comparisons of these downward conti

real time discrimination of earthquake foreshocks and aftershocks immediately after a large earthquake the main question asked by the public and decision makers is whether it was the mainshock or a foreshock to an even stronger event yet to come so far scientists can only offer empirical evidence from statistical compilations of past sequences arguing that normally the aftershock sequence will decay gradually whereas the occurrence of a forthcoming larger event has a probability of a few per cent here we analyse the average size distribution of aftershocks of the recent amatrice norcia and kumamoto earthquake sequences and we suggest that in many cases it may be possible to discriminate whether an ongoing sequence represents a decaying aftershock sequence or foreshocks to an upcoming large event we propose a simple traffic light classification to assess in real time the level of concern about a subsequent larger event and test it against 58 sequences achieving a classification accuracy of 95 per cent

effective stress history and the potential for seismicity associated with hydraulic fracturing of shale reservoirs the influence of effective stress history on reservoir stability and the response to hydraulic fracturing are simulated for two hypothetical shale reservoirs it is numerically demonstrated that the effective stress history influences the present day stability of faults and natural fractures any assumption of a homogeneous stress state is shown to be unrealistic in the majority of fractured shale reservoirs the simulations demonstrate that depending upon the effective stress history shear displacements can be induced by stress changes associated with stimulation without a change of fluid pressure in the destabilized fractures elastoplastic shale and other fractured reservoirs are shown to have a memory of past geomechanical states these numerical findings demonstrate the value of interpreting reservoir effective stress history when planning fluid injection a previous case history is summarized to illustrate the overwhelming dependence of stress history analyses on a wide spectrum of earth science disciplines it also illustrates the application of stress history analyses to activities other than hydraulic fracturing the current inexperience of effective stress history description means that new approaches must be identified to optimize the necessary multidisciplinary investigations supplementary material details of the simulations are available at www geolsoc org uk sup18743

control of hazard due to seismicity induced by a hot fractured rock geothermal project in 2003 hydraulic stimulations were carried out in a geothermal field in eastern el salvador central america as part of a project to explore the feasibility of commercial hot fractured rock energy generation a key requisite for this environmentally friendly energy source is that the fracturing of the hot rocks at depths of 1 2 km must not produce levels of ground shaking at the surface that would present a serious disturbance or threat to the local population thresholds of tolerable ground motion were inferred from guidelines and regulations on tolerable levels of vibration and from correlations between instrumental strong motion parameters and intensity considering the vulnerability of the exposed housing stock the thresholds were defined in terms of peak ground velocity pgv and incorporated into a traffic light system that also took account of the frequency of occurrence of the induced earthquakes the system was implemented through a dedicated seismograph array and locally derived predictive equations for pgv the traffic light was used as a decision making tool regarding the duration and intensity of pumping levels during the hydraulic stimulations the system was supplemented by a small number of accelerographs and re calibrated using records obtained during the rock fracturing

ground motion and macroseismic intensities of a seismic event related to geothermal reservoir stimulation below the city of basel observations and modelling summary to stimulate a geothermal reservoir below the city of basel switzerland fluid was injected in december 2006 at high pressure into a 5 km deep borehole this stimulation led to an increase in local seismicity with the largest seismic event ml 3 4 occurring on 2006 december 8 the event was widely felt by the local population slight non structural damage to buildings was reported and ultimately this event was the cause to put the geothermal project on hold in this study we present recorded ground motion and determinations of macroseismic intensity of the ml 3 4 event as well as simulations of seismic wave propagation and a model to predict macroseismic intensities as the two models are based on different simplifying assumptions and different underlying physical processes the predicted intensity distributions exhibit differences in their details however the first order characteristics of the observed macroseismic intensity distribution are well matched based on this result we compute intensities also for hypothetical scenarios of earthquakes with larger magnitudes

erosion of river terraces as a component of large catchment sediment budgets a pilot study from the gangetic plain erosion of river terraces and alluvial interfluves in large catchments may be a significant source of sediment but is not readily included in sediment budgets because quantification is not straightforward here a pond on a large river terrace on the gangetic plain in northern india provides an estimate of the proportion of sheet and rill erosion products that reaches a valley floor and by analogy the amount that reaches a channel that drains to a major river and insights into the sensitivity of this delivery to climate change and land use comparison is made between the rate of delivery of the products of sheet and rill erosion to a valley floor with approximate sediment yield from gullies indicating that the latter is likely to be a more significant source of sediment this is a pilot study and its limitations can guide future research the construction of sediment budgets in many large catchments worldwide could potentially include the approach reported here the study also contributes to understanding of human environment interactions specifically with regard to sheet erosion of agricultural soils

magnitudes of induced earthquakes and geometric scales of fluid stimulated rock volumes sometimes rock stimulations by fluid injections into geothermal boreholes are able to trigger perceptible or even potentially damaging earthquakes this does not seem to be the case for hydraulic fracturing of hydrocarbon reservoirs reasons for such a difference and factors defining magnitudes of induced earthquakes triggered tectonicly as well as induced artificially remain unclear we analyzed microseismic data obtained by fluid stimulations at different geothermal and hydrocarbon sites this analysis indicates that a rupture corresponding to a fluid induced earthquake seems to be only probable along a surface located mainly inside a stimulated rock volume we approximated the stimulated volume by an ellipsoid and compared the statistics of induced events with the statistics of randomly distributed thin flat disks modeling rupture surfaces we found that one of the main factors limiting the probability to induce a large magnitude event is the minimum principal axis of a fluid stimulated rock volume

intensity prediction equations for north america abstract equations that predict intensity as a function of magnitude and distance are useful tools for hazard and risk assessment and in interpretation of both contemporary and historical earthquake information the intensity prediction equations of atkinson and wald 2007 hereafter aw07 have been remarkably successful in describing the level and intensity of motions reported under the did you feel it dyfi program over the last several years examination of the performance of aw07 for north american earthquakes evaluated using an extensive compiled database of dyfi observations from 2000 to 2013 suggests that there is little statistical basis for revising these equations however a problem with the aw07 equations is that they predict unrealistically large median intensities for large events m 6 at close distances in this study we revise aw07 to improve the intensity scaling at large magnitudes and close distances by reconciling intensity equations with ground motion prediction equations

induced seismicity and the potential for liability under u s law abstract research by seismologists over the past 30 years has firmly established that some human activities induce seismicity sometimes induced seismicity causes injuries to people or property the activities which induce seismicity generally involve extraction of energy or natural resources or the disposal of wastes as the human population increases these extraction and disposal activities will increase in number of sites and intensity of effort as the demands become greater and the resources scarcer with these increases the number and severity of damaging induced earthquakes is likely to increase induced seismicity may cause injuries by vibrations or by seismically induced ground failure in either case compensation for injuries caused by induced seismicity should be paid for by the inducer in the united states the inducer of damaging seismicity can be made to pay for the harm caused liability for damage caused by vibrations can be based on several legal theories trespass strict liability negligence and nuisance our research revealed no cases in which an appellate court has upheld or rejected the application of tort liability to an induced earthquake situation however there are numerous analogous cases that support the application of these legal theories to induced seismicity vibrations or concussions due to blasting or heavy machinery are sometimes viewed as a trespass analogous to a physical invasion in some states activities which induce earthquakes might be considered abnormally dangerous activities that require companies engaged in them to pay for injuries the quakes cause regardless of how careful the inducers were in some circumstances a court may find that an inducer was negligent in its site selection or in maintenance of the project if induced seismicity interferes with the use or enjoyment of another s land then the inducing activity may be a legal nuisance even if the seismicity causes little physical damage in most states of the united states owners of land owe a duty of lateral support to adjacent landowners and in some states mineral estate owners and lessees owe a duty of subjacent support to the surface owners failure to meet those duties of support can result in liability seismicity induced by one source might accelerate failure of support originating from another source leaving both of the parties at fault proportionally liable to the injured parties geoscientists can use their roles as investigators educators and advisors to help companies in the petroleum mining and geothermal fields avoid liability

ground motion prediction equations for the geysers geothermal area based on induced seismicity records abstract the geysers geothermal field in northern california which has been actively exploited since the 1960s is the world s largest geothermal field the continuous injection of fluids and the consequent stress perturbations induce seismicity that is clearly felt in the surrounding communities in order to evaluate seismic hazard due to induced seismicity and the effects of seismicity rate level on the population and buildings in the area reliable ground motion prediction equations gmpes must be developed this paper introduces the first gmpes specific for the geysers area in terms of peak ground velocity pgv peak ground acceleration pga and 5 damped spectral acceleration sa t at t 0 2 s 0 5 s and 1 0 s the adopted non linear mixed effect regression technique to derive the gmpe includes both fixed and random effects and it permits to account for both inter event and intra event dependencies in the data site specific effects are also estimated from the data and are corrected in the final ground motion model we used data from earthquakes recorded at 29 stations of the berkeley geysers network during the period september 2007 through november 2010 the magnitude range is 1 3 m w 3 3 whereas the hypocentral distances range between 0 5 km and 20 km the comparison of our new gmpe for the geysers with a standard model derived in a different tectonic context shows that our model is more robust when predictions have to be made for induced earthquakes in this geothermal area

destructive upper crustal earthquakes of central america since 1900 we have compiled a catalog of 51 destructive upper crustal earthquakes in central america since 1900 an event is included if it caused casualties or heavy damage of modified mercalli mm intensity vii all events larger than magnitude ms 5 7 are found to be destructive we believe the catalog is complete for events of ms 6 along the volcanic front the catalog includes estimates of epicentral coordinates depth magnitude and casualties for all events and presents mm intensity vii contours for most events data in this catalog place severe constraints on the spatial temporal and magnitude distribution of destructive upper crustal earthquakes in central america the catalog contains 30 events of ms 6 depths of well constrained mainshock hypocenters range from 5 to 15 km the most striking feature of the catalog is the spatial alignment along the volcanic front of 23 of the 30 events volcanic front earthquake source mechanisms for such events show east west tension and are compatible with a model of the volcanic front as a zone of right lateral strike slip faulting volcanic front earthquake magnitudes do not exceed ms 6 5 except in southeastern guatemala where they reach ms 6 9 maximum earthquake magnitudes are apparently related to the distance between adjacent holocene volcanic centers destructive events occur at offsets in the volcanic chain as isolated mainshock aftershock sequences however within linear segments destructive earthquakes have a strong tendency to cluster and are often preceded by significant foreshock activity although the volcanic front is the locus of both destructive earthquakes and volcanism we find no temporal correlation between the two of the seven events of ms 6 that did not originate near the volcanic front six originated near the transcurrent caribbean north american plate boundary including the ms 7 5 guatemala earthquake of 1976 along the volcanic front destructive upper crustal earthquakes have occurred at a rate of about one event every 2 1 2 years during this century much more frequently than along either the caribbean north american plate boundary or the subduction zone in central america since 1900 about 17 000 people have died from volcanic front earthquakes but only about 2000 people are known to have died from subduction zone earthquakes although subduction zone earthquakes can have larger magnitudes and produce more widespread damage destructive volcanic front earthquakes pose the greater hazard because they are more frequent and originate much closer to the bulk of central america s population which is concentrated along the volcanic front

probability of inducing given magnitude earthquakes by perturbing finite volumes of rocks 1 fluid induced seismicity results from an activation of finite rock volumes the finiteness of perturbed volumes influences frequency magnitude statistics previously we observed that induced large magnitude events at geothermal and hydrocarbon reservoirs are frequently underrepresented in comparison with the gutenberg richter law this is an indication that the events are more probable on rupture surfaces contained within the stimulated volume here we theoretically and numerically analyze this effect we consider different possible scenarios of event triggering rupture surfaces located completely within or intersecting only the stimulated volume we approximate the stimulated volume by an ellipsoid or cuboid and derive the statistics of induced events from the statistics of random thin flat discs modeling rupture surfaces we derive lower and upper bounds of the probability to induce a given magnitude event the bounds depend strongly on the minimum principal axis of the stimulated volume we compare the bounds with data on seismicity induced by fluid injections in boreholes fitting the bounds to the frequency magnitude distribution provides estimates of a largest expected induced magnitude and a characteristic stress drop in addition to improved estimates of the gutenberg richter a and b parameters the observed frequency magnitude curves seem to follow mainly the lower bound however in some case studies there are individual large magnitude events clearly deviating from this statistic we propose that such events can be interpreted as triggered ones in contrast to the absolute majority of the induced events following the lower bound

large magnitude crustal seismic sources in el salvador and deterministic hazard scenarios abstract during the last years several crustal seismic sources have been proposed in el salvador however the actual destructive potential of these proposals has not been revealed yet here we present several seismic scenarios related with the main crustal faults in the country we have characterized the corresponding hazard scenarios in a deterministic way estimating the peak ground accelerations pga including local site effects in addition we present a list of 29 sources that can be considered potentially dangerous with their main features when they are available and four seismic scenarios that we consider to be more probable we have resorted to the february 13th 2001 mw 6 6 destructive earthquake the only earthquake occurred in a known crustal source in el salvador and recorded by the strong motion network in order to test the methodological approach and the reliability of the pga results predicted by two available ground motion prediction equations gmpes including the site effect the consistence between the values given by the models and the ones recorded during the event provides reliability to our results this approach allowed us to conclude that faults within the volcanic arc can produce accelerations up to 1 g in the most conservator case mw 7 0 while accelerations up to 0 6 g are usual results related with specific faults within the salvadoran volcanic arc besides the reported damage distribution of the 8th june 1917 earthquakes and its similarity with one of the proposed scenarios allowed us to infer the possible source of this event the guaycume fault

fluvial processes and vegetation glimpses of the past the present and perhaps the future abstract most research before 1960 into interactions among fluvial processes resulting landforms and vegetation was descriptive since then however research has become more detailed and quantitative permitting numerical modeling and applications including agricultural erosion abatement and rehabilitation of altered bottomlands although progress was largely observational the empiricism increasingly yielded to objective recognition of how vegetation interacts with and influences geomorphic process a review of advances relating fluvial processes and vegetation during the last 50 years centers on hydrologic reconstructions from tree rings plant indicators of flow and flood frequency parameters hydrologic controls on plant species regulation of sediment movement by vegetation vegetative controls on mass movement and relations between plant cover and sediment movement extension of present studies of vegetation as a regulator of bottomland hydrologic and geomorphic processes may become markedly more sophisticated and widespread than at present research emphases that are likely to continue include vegetative considerations for erosion modeling response of riparian zone forests to disturbance such as dams and water diversion the effect of vegetation on channel and bottomland dynamics and rehabilitation of stream corridors research topics that presently are receiving attention are the effect of woody vegetation on the roughness of stream corridors and hence processes of flood conveyance and flood plain sedimentation the development of a theoretical basis for rehabilitation projects as opposed to fully empirical approaches the effect of invasive plant species on the dynamics of bottomland vegetation the quantification of below surface biomass and related soil stability factors for use in erosion prediction models and the effect of impoundments on downstream narrowing of channels and accompanying encroachment of vegetation bottomland vegetation partially controls and is controlled by fluvial geomorphic processes the purposes of this paper are to identify and review investigations that have related vegetation to bottomland features and processes to distinguish the present status of these investigations and to anticipate future research into how hydrologic and fluvial geomorphic processes of bottomlands interact with vegetation

role of tree dams in the construction of pseudo terraces and variable geomorphic response to floods in little river valley virginia geomorphic response to a 1985 flood in little river valley northern virginia was different in magnitude and style from the largest historic flood in the same valley in 1949 the primary geomorphic activity during the 1985 flood was severe bank erosion and channel gravel deposition rather than the debris flow and avalanching of the 1949 event an unusual and widespread phenomenon of the recent flood was that large trees eroded and transported by the floodwater were aligned parallel to the river banks and at isolated sites were braced and stacked against trees still standing on the floodplain lateral barriers or dams created from these displaced trees allowed the channel to be locally aggraded above the level of the flood plain in these reaches little if any river gravel was deposited on the floodplain even though the adjacent channel floor was raised well above that surface the river has now shifted around the filled segments leaving flat isolated surfaces underlain by channel gravel standing above the level of the modern floodplain these features may be mistaken for terraces alter they become vegetated and the trees bracing the gravels decay interpreting these surfaces to be terrace remnants would lead to a faulty reconstruction of geomorphic history in the little river valley and other valleys where floodplain morphology is controlled by infrequent flood events

earth s lithospheric magnetic field determined to spherical harmonic degree 90 from champ satellite measurements summary the champ magnetic field mission is providing highly reliable measurements from which the global lithospheric magnetic field can be determined in unprecedented resolution and accuracy using almost 5 yr of data we derive our fourth generation lithospheric field model termed mf4 which is expanded to spherical harmonic degree and order 90 after subtracting from the full magnetic field observations predicted fields from an internal field model up to degree 15 an external field model up to degree two and the predicted magnetic field signatures for the eight dominant ocean tidal constituents we fit and remove remaining external fields and polar electrojet signatures in a track by track scheme from a subset of least disturbed tracks we estimate the mf4 model by least squares damping ill determined coefficients by regularization the resulting mf4 model provides a good representation of the lithospheric field down to an altitude of about 50 km at lower latitudes with reduced accuracy in the polar regions crustal features come out significantly sharper than in previous models in particular bands of magnetic anomalies along subduction zones become visible by satellite for the first time

dynamic fault interaction during a fluid injection induced earthquake the 2017 mw 5 5 pohang event the november 15th 2017 mw 5 5 pohang earthquake south korea has been linked to hydraulic stimulation and fluid injections making this the largest induced seismic event associated with an enhanced geothermal system egs to understand its source dynamics and fault interactions we conduct the first 3d high resolution spontaneous dynamic rupture simulations of an induced earthquake we account for topography off fault plastic deformation under depth dependent bulk cohesion rapid velocity weakening friction and 1d subsurface structure a guided fault reconstruction approach that clusters spatio temporal aftershock locations including their uncertainties is used to identify a main and a secondary fault plane that intersects under a shallow angle of 15 based on simple mohr coulomb failure analysis and 180 dynamic rupture experiments in which we vary local stress loading conditions fluid pressure and relative fault strength we identify preferred two fault plane scenarios that well reproduce observations we find that the regional far field tectonic stress regime promotes pure strike slip faulting while local stress conditions constrained by borehole logging generate the observed thrust faulting component our preferred model is characterized by overpressurized pore fluids non optimally oriented but dynamically weak faults and a close to critical local stress state in our model earthquake rupture jumps to the secondary fault by dynamic triggering generating a measurable non double couple component our simulations suggest that complex dynamic fault interaction may occur during fluid injection induced earthquakes and that local stress perturbations dominate over the regional stress conditions these findings therefore have important implications for seismic hazard in active geo reservoir

performance assessment of the induced seismicity traffic light protocol for northeastern british columbia and western alberta abstract in response to the increasing concern of possible seismic risk due to injection operations during development of unconventional hydrocarbon resources regulators in both british columbia bc and alberta ab canada have adopted varying aspects of a traffic light protocol as part of their individual oversight and risk mitigation strategies in this study we compare the regional seismicity pattern with the database of injection parameters to assess the performance of the individual induced seismicity traffic light protocols is tlp the red light threshold in both bc and ab is set at local magnitude ml 4 which appears to be adequate in characterizing the potential seismic risk from induced earthquakes since 2014 there were three red light events each in bc and ab all related to hydraulic fracturing in the three ab cases and one bc case at least one 2 ml 4 seismic event characterized in ab as a yellow light event preceded the red light event suggesting that an is tlp based on e

balancing reservoir creation and seismic hazard in enhanced geothermal systems summary fractureshear dilatancyisanessentialprocessforenhancingthepermeabilityofdeepgeothermal reservoirs and is usually accompanied by the radiation of seismic waves however the hazard and risk perspective of induced seismicity research typically focuses only on the question of how to reduce the occurrence of induced earthquakes here we present a quantitative analysisofseismichazardasafunctionofthetwokeyfactorsdefininganenhancedgeothermal system the permeability enhancement and the size of the stimulated reservoir our model has two coupled components 1 a pressure diffusion model and 2 a stochastic seismicity model permeability is increased in the source area of each induced earthquake depending on the amount of slip which is determined by the magnitude we show that the few largest earthquakes i e 5 10 events with m 1 5 contribute more than half of the total reservoir stimulation the results further indicate that planning and controlling of reservoir engineering operations may be compromised by the considerable variability of maximum observed magnitude reservoir size the gutenberg richter b value and shapiro s seismogenic index i e a measure of seismic reactivity of a reservoir that arises from the intrinsic stochastic nature of induced seismicity we also find that injection volume has a large impact on both reservoir size and seismic hazard injection rate and injection scheme have a negligible effect the impact of site specific parameters on seismicity and reservoir properties is greater than that of the injected volume in particular conditions that lead to high b values possibly a low differential stress level have a high impact on seismic hazard but also reduce the efficiency of the stimulation in terms of permeability enhancement under such conditions target reservoir permeability can still be achieved without reaching an unacceptable level of seismic hazard if either the initial reservoir permeability is high or if several fractures are stimulated the proposed methodology is a first step towards including induced seismic hazard analysis into the design of reservoir stimulation in a quantitative and robust manner

identifying potentially induced seismicity and assessing statistical significance in oklahoma and california we develop a statistical method for identifying induced seismicity from large datasets and apply the method to decades of wastewater disposal and seismicity data in california and oklahoma the study regions are divided into gridblocks we use a longitudinal study design seeking associations between seismicity and wastewater injection volume along time series within each gridblock in each gridblock we find the maximum likelihood estimate for a model parameter that relates induced seismicity hazard to total volume of wastewater injected each year to assess significance we compute likelihood ratio test statistics in each gridblock and each state california and oklahoma resampling with permutation and random temporal offset of injection data is used to estimate p values from the likelihood ratio statistics we focus on assessing whether observed associations between injection and seismicity occur more often than would be expected by chance we do not attempt to quantify the overall incidence of induced seismicity the study is designed so that under reasonable assumptions the associations can be formally interpreted as demonstrating causality wastewater disposal is associated with other activities that can induce seismicity such as reservoir depletion therefore our results should be interpreted as finding seismicity induced by wastewater disposal and all other associated activities in oklahoma the analysis finds with extremely high confidence that seismicity associated with wastewater disposal has occurred in california the analysis finds moderate evidence that seismicity associated with wastewater disposal has occurred but the result is not strong enough to be conclusive

shaking from injection induced earthquakes in the central and eastern united states abstract in this study i consider the ground motions generated by 11 moderate m w 4 0 5 6 earthquakes in the central and eastern united states that are thought or suspected to be induced by fluid injection using spatially rich intensity data from the u s geological survey did you feel it system i show the distance decay of intensities for all events is consistent with that observed for tectonic earthquakes in the region but for all of the events intensities are lower than the values predicted from an intensity prediction equation that successfully characterizes intensities for regional tectonic events i introduce an effective intensity magnitude m ie defined as the magnitude that on average would generate a given intensity distribution for all 11 events m ie is lower than the event magnitude by 0 4 1 3 magnitude units with an average difference of 0 82 units this suggests stress drops of injection induced earthquakes are systematically lower than tectonic earthquakes by an estimated factor of 2 10 however relatively limited data suggest intensities for epicentral distances less than 10 km are more commensurate with expectations for the event magnitude which can be reasonably explained by the shallow focal depth of the events the results suggest damage from injection induced earthquakes will be especially concentrated in the immediate epicentral region

shaking intensity thresholds for rock falls and slides evidence from 1987 whittier narrows and superstition hills earthquake strong motion records due to inconsistencies in using descriptive intensity scales to describe earthquake shaking necessary to trigger landslides arias intensity a quantity calculated from seismic strong motion records has been employed as a measure of the seismic energy required to initiate landslides because arias intensity is defined as the sum of all the squared acceleration values from a strong motion record it is a measure of the energy dissipated at a site by shaking it incorporates both amplitude and duration information making it more useful to compare with the failure of slopes than parameters such as peak acceleration arias intensities calculated from the 24 october 1987 superstition hills and the 1 october 1987 whittier narrows earthquakes in southern california allow comparisons with the limits of landslides specifically falls and slides from rock and soil in these two earthquakes these comparisons establish two shaking thresholds for the limits of falls and slides a range of 0 08 to 0 6 m sec is observed for tertiary and younger deposits while the range of 0 01 to 0 07 m sec is observed for mesozoic and older rocks these two ranges of shaking levels are controlled by the relative degree of fracturing and aperture of fracture systems within the two general age groups of rocks and soils in the los angeles area and the imperial valley

the induced earthquake sequence related to the st gallen deep geothermal project switzerland fault reactivation and fluid interactions imaged by microseismicity in july 2013 a sequence of more than 340 earthquakes was induced by reservoir stimulations and well control procedures following a gas kick at a deep geothermal drilling project close to the city of st gallen switzerland the sequence culminated in an ml 3 5 earthquake which was felt within 10 15 km from the epicenter high quality earthquake locations and 3 d reflection seismic data acquired in the st gallen project provide a unique data set which allows high resolution studies of earthquake triggering related to the injection of fluids into macroscopic fault zones in this study we present a high precision earthquake catalog of the induced sequence absolute locations are constrained by a coupled hypocenter velocity inversion and subsequent double difference relocations image the geometry of the ml 3 5 rupture and resolve the spatiotemporal evolution of seismicity a joint interpretation of earthquake and seismic data shows that the majority of the seismicity occurred in the pre mesozoic basement hundreds of meters below the borehole and the targeted mesozoic sequence we propose a hydraulic connectivity between the reactivated fault and the borehole likely through faults mapped by seismic data despite the excellent quality of the seismic data the association of seismicity with mapped faults remains ambiguous in summary our results document that the actual hydraulic properties of a fault system and hydraulic connections between its fault segments are complex and may not be predictable upfront incomplete knowledge of fault structures and stress heterogeneities within highly complex fault systems additionally challenge the degree of predictability of induced seismicity related to underground fluid injections

selecting ground motion models developed for induced seismicity in geothermal areas we present a case study of the ranking and weighting of ground motion prediction equations gmpes for seismic hazard assessment of enhanced geothermal systems egss the study region is cooper basin australia where a hot fractured rock project was established in 2002 we test the applicability of 36 gmpes based on stochastic simulations previously proposed for use at egss each gmpe has a set of corresponding model parameters describing stress drop regional and local near surface attenuation to select suitable gmpes for cooper basin from the full set we applied two methods in the first seismograms recorded on the local monitoring network were spectrally analysed to determine characteristic stress and attenuation parameters in a second approach residual analysis using the log likelihood llh method was used to directly compare recorded and predicted short period response spectral accelerations the resulting ranking was consistent with the models selected based on spectral analysis with the advantage that a transparent weighting approach was available using the llh method region specific estimates of variability were computed with significantly lower values observed compared to previous studies of small earthquakes this was consistent with the limited range of stress drops and attenuation observed from the spectral analysis

modeling the lithospheric magnetic field over france by means of revised spherical cap harmonic analysis r scha 1 we have recently proposed the revised spherical cap harmonic analysis r scha modeling technique the new mathematical functions represent faithfully the spatial variations of potential fields in a restricted area in this paper we tackle the inverse problem and outline the efficiency of the new basis functions with respect to real magnetic data processing simultaneously repeat stations observatory aeromagnetic and champ satellite data provides our first vector lithospheric field model over france which extends from surface to 500 km of altitude the magnetic field is represented with a minimum horizontal spatial representation of 40 km at the mean earth radius the magnetic lithospheric map consistency is confirmed with a comparison to known geological features the model variation with altitude also suggests that the major french magnetic anomaly the paris basin anomaly is produced by a deep rooted geological structure these results demonstrate the superiority of regional modeling over global modeling for delineating small scale details in the lithospheric field in view of forthcoming satellite missions like swarm the revised spherical cap harmonic analysis method will help to accurately represent the lithospheric field for more detailed geological interpretations

satellite observations of magnetic fields due to ocean tidal flow the ocean is an electrically conducting fluid that generates secondary magnetic fields as it flows through earth s main magnetic field extracting ocean flow signals from remote observations has become possible with the current generation of satellites measuring earth s magnetic field here we consider the magnetic fields generated by the ocean lunar semidiurnal m2 tide and demonstrate that magnetic fields of oceanic origin can be clearly identified in satellite observations

developing an application specific ground motion model for induced seismicity abstract a key element of quantifying both the hazard and risk due to induced earthquakes is a suite of appropriate ground motion prediction equations gmpes that encompass the possible shaking levels due to such events induced earthquakes are likely to be of smaller magnitude and shallower focal depth than the tectonic earthquakes for which most gmpes are derived furthermore whereas gmpes for moderate to large magnitude earthquakes are usually derived to be transportable to different locations and applications taking advantage of the limited regional dependence observed for such events the characteristics of induced earthquakes warrant the development of application specific models a preliminary ground motion model for induced seismicity in the groningen gas field in the netherlands is presented as an illustration of a possible approach to the development of these equations the gmpe is calibrated to local recordings of small magnitude events and captures the epistemic uncertainty in the extrapolation to larger magnitude considered in the assessment of the resulting hazard and risk

a warning system for rainfall induced shallow failures abstract it is widely recognised that soil slips and debris flows are triggered by short intense storms owing its geologic geomorphologic and climatic settings the piedmont region nw italy is highly prone to the occurrence of this kind of landslides in the last two centuries in fact a total of 105 severe meteoric events which triggered shallow failures occurred and of these 18 events took place from 1990 to 2002 a fair number of rainfall thresholds have been proposed in the literature defined both on empirical or on physical bases empirical thresholds are defined collecting rainfall data for landslide meteoric events and for events without landslides while physical thresholds are based on numerical models that consider the relation between rainfall pore pressure and slope stability the main objective of this paper is the identification of the empirical triggering thresholds for the piedmont region four meteoric events were selected and analysed november 4 5 1994 july 7 8 1996 april 27 30 2000 october 13 16 2000 because they supply a wide range of variation for both rainfall parameters duration intensity cumulative rainfalls and the number of induced landslides in the intensity duration plot the critical limit is described by the equation i 19d 0 50 where i rainfall intensity expressed in mm h and d rainfall duration expressed in hours such a limit is traced to envelop 90 of the points on the graph in the ni d diagram the triggering thresholds are given by the equations ni 0 76d 0 33 and ni 4 62d 0 79 where ni normalised intensity with respect to the annual precipitation map expressed in mm h pma 100 in the article the different meaning of these thresholds is discussed finally the diagram ni ncr is proposed the triggering threshold is given by the expression ni 0 09ln ncr 0 54 where ncr is the normalised cumulative critical rainfall mm pma 100 the application of the triggering thresholds as a fundamental element in a warning system dedicated to the safeguarding of population in landslide prone areas is discussed in detail an operating procedure which is presently being verified and tested in the studied area is described

oklahoma experiences largest earthquake during ongoing regional wastewater injection hazard mitigation efforts the 3 september 2016 mw 5 8 pawnee earthquake was the largest recorded earthquake in the state of oklahoma seismic and geodetic observations of the pawnee sequence including precise hypocenter locations and moment tensor modeling shows that the pawnee earthquake occurred on a previously unknown left lateral strike slip basement fault that intersects the mapped right lateral labette fault zone the pawnee earthquake is part of an unprecedented increase in the earthquake rate in oklahoma that is largely considered the result of the deep injection of waste fluids from oil and gas production if this is indeed the case for the m5 8 pawnee earthquake then this would be the largest event to have been induced by fluid injection since 2015 oklahoma has undergone wide scale mitigation efforts primarily aimed at reducing injection volumes thus far in 2016 the rate of m3 and greater earthquakes has decreased as compared to 2015 while the cumulative moment or energy released from earthquakes has increased this highlights the difficulty in earthquake hazard mitigation efforts given the poorly understood long term diffusive effects of wastewater injection and their connection to seismicity

geomorphology and vegetation on hillslopes interactions dependencies and feedback loops article i nfo the linkages between vegetation and hillslope geomorphology have been the subject of serious study for years but traditionally ecologists and geomorphologists have viewed these interactions as unidirectional on the one hand botanists and landscape ecologists have examined the effects of hillslope features processes and materials on vegetation structure composition and dynamics focus has been placed on the effects of topography elevation slope angle slope aspect edaphic factors rock type and geomorphic disturbance mass movement snow avalanches land surface erosion on the other hand geomorphologists have traditionally treated vegetation as an independent variable that affects landforms and sediment routing at limited spatial temporal scales hillslope vegetation and landforms however co evolve one key is to understand the role of time disturbances and feedbacks that link vegetation and geomorphology on hillslopes the effects of vegetation on mass movement and landscape evolution are being studied in new ways many regional studies claim that vegetation becomes less relevant as one moves to larger and larger watershed scales but ecoregion analysis offers a contrasting view whereas these efforts have produced vehicles of understanding that are simple ordered unified and harmonious they often do not reflect the complexity that leads to multiple possible outcomes place dependent results recent perspectives focus on the two way interplay between vegetation and hillslope geomorphology where establishing cause and effect linkages is made difficult by confounding factors spatial temporal scale location convergence divergence nonlinearity thresholds feedbacks vegetation and geomorphology interactions are controlled by a combination of global factors independent of time and place and the local environmental history continued refinement of fine scale deterministic models should be encouraged but the ability to translate these results to larger scales needs to be explored at large scales future research especially those with predictive modeling as the goal should concentrate on how to increase the generality of concepts and models and should seek to reduce the number of variables and factors considered

reciprocal interactions and adjustments between fluvial landforms and vegetation dynamics in river corridors a review of complementary approaches abstract until recently one way relationships between flow dynamics geomorphology and plant ecology were considered dominantly when studying the functioning of river systems whereby fluvial landforms and hydrogeomorphic processes drive the evolution of riparian plant communities however biological communities may significantly control geomorphic processes and have strong impacts on landform dynamics in order to fully identify the processes linked to river dynamics changes in time and space of fluvial landforms and associated plant communities conceptual multidisciplinary progress is clearly needed to understand the mutual interactions and feedbacks between fluvial landforms and vegetation community dynamics this paper presents a detailed literature review of fluvial geomorphology riparian plant ecology and hydraulic engineering knowledge the historical and recent development of ecological plant succession theory toward the integration of hydrogeomorphic disturbances is discussed as well as the integration of vegetation within geomorphology as a significant landform control factor incorporating both hydrogeomorphic controls on riparian vegetation dynamics and mechanical impacts of vegetation structures on flow properties and sediment dynamics recent progress in ecology hydraulic engineering and fluvial geomorphology emphasises interdependence between biological and physical forms and processes based on this literature review a fluvial biogeomorphic succession concept is proposed to link fluvial landform and riparian vegetation community evolution within a bi directional model the succession of fluvial landforms and associated vegetation communities is composed of four main critical phases that represent a shift in the relative dominance of hydrogeomorphic and ecological processes as a response to biostabilisation and passive bioconstruction processes the positive feedbacks associated with this shift lead to the development of characteristic biogeomorphic structures such as vegetated banks islands or floodplains which are moderated by the biogeomorphic functional roles of ecosystem engineers that induce or reinforce the positive feedbacks this fluvial biogeomorphic succession concept relates the natural darwinian selection and ecological succession theories to fluvial geomorphology

generation of large postinjection induced seismic events by backflow from dead end faults and fractures induced seismicity is common during hydraulic stimulation in fractured crystalline rock fluid injection pressurizes preexisting fractures triggering slip and seismicity often the largest induced events occur after the end of injection which complicates efforts to manage seismic risk in this study a three dimensional discrete fracture network simulator that couples fluid flow with earthquake simulation was used to investigate a novel hypothesis for why large postinjection seismic events occur fractures that form dead end pathways differentially pressurize during injection after injection is stopped fluid backflows through the well from the dead end fractures into larger fractures inducing additional seismicity and potentially causing events larger than occurred during injection our simulations indicate that flowing fluid back to the surface immediately after injection could mitigate this effect and reduce postinjection seismicity

extending comprehensive models of the earth s magnetic field with orsted and champ data summary a new model of the quiet time near earth magnetic field has been derived using a comprehensive approach which includes not only pogo and magsat satellite data but also data from the orsted and champ satellites the resulting model shows great improvement over its predecessors in terms of completeness of sources time span and noise reduction in parameters with its well separated fields and extended time domain of 1960 to mid 2002 the model is able to detect the known sequence of geomagnetic jerks within this frame and gives evidence for an event of interest around 1997 because all sources are coestimated in a comprehensive approach intriguing north south features typically filtered out with other methods are being discovered in the lithospheric representation of the model such as the s atlantic spreading ridge and andean subduction zone lineations in addition this lithospheric field exhibits significantly less noise than previous models as a result of improved data selection the f region currents through which the satellites pass are now treated as lying within meridional planes as opposed to being purely radial results are consistent with those found previously for magsat but an analysis at orsted altitude shows exciting evidence that the meridional currents associated with the equatorial electrojet likely close beneath the satellite besides the model a new analysis technique has been developed to infer the portion of a model parameter state resolved by a particular data subset this has proven very useful in diagnosing the cause of peculiar artefacts in the magsat vector data which seem to suggest the presence of a small misalignment bias in the vector magnetometer

from induced seismicity to direct time dependent seismic hazard the growing installation of industrial facilities for subsurface exploration worldwide requires continuous re nements in understanding both the mechanisms by which seismicity is induced by eld operations and the related seismic hazard particularly in proximity of densely populated areas induced low to moderate magnitude seismicity characterized by high frequency content can be clearly felt by the surrounding inhabitants and in some cases may produce damage in this respect we propose a technique for time dependent probabilistic seismic hazard analysis to be used in geothermal elds as a monitoring tool for the e ects of on going eld operations the technique integrates the observed features of the seismic ity induced by uid injection and extraction with a local ground motion prediction equation the result of the analysis is the time evolving probability of exceedance of peak ground acceleration which can be compared with selected critical values to manage eld operations to evaluate the reliability of the proposed technique we applied it to data collected in the geysers geothermal eld in northern california between 1 september 2007 and 15 november 2010 we show that in the period considered the seismic hazard at the geysers was variable in time and space which is a consequence of the eld operations and the variation of both seismicity rate and b value we conclude that for the exposure period taken into account i e 2 months as a conservative limit peak ground acceleration values corresponding to the lowest probability of exceedance e g 30 must not be exceeded to ensure safe eld operations we suggest testing the proposed technique at other geothermal areas or in regions where seismicity is induced for example by hydrocarbon exploitation or carbon dioxide storage

the contributions of biogeomorphology to the emerging field of geobiology biogeomorphology has developed into a well established research field over the past 15 years with studies examining a range of two way interrelations between organisms and geomorphology in a variety of terrestrial and marine environments this paper starts by defining the core biogeomorphological processes bioerosion bioprotection and bioconstruction particular emphasis is placed on the study of bioconstructional forms providing a clear definition examples of bioconstructions and crucially examining important interactions between bioconstruction and bioerosion three key areas where biogeomorphological research can directly contribute to the emerging field of geobiology are identified 1 the use of biogeomorphological approaches combined with palaeoecological investigations and predictive modelling in the growing field of carbon sequestration and climate change mitigation 2 providing geomorphological expertise to support the emerging field of astrobiology and 3 the potential contributions of biogeomorphology to the blossoming field of bio geoengineering some key research directions and challenges for future biogeomorphological research include exploring how biogeomorphological studies can contribute to and benefit from collaborations with other fields of geobiology and assisting in the development of a useful effective interdisciplinary toolbox of methods to improve quantification of geobiological processes importantly suggestions are made for potentially fruitful collaborations with geomicrobiologists geochemists and palaeoecologists

evaluation of using r scha to simultaneously model main field and secular variation multilevel geomagnetic data for the north atlantic abstract one efficient approach to modelling the earth s core magnetic field involves the inclusion of crossover marine data which cover areas lacking in observatory and repeat station data for epochs when precise three component satellite magnetic field measurements were not common in this study we show how the revised spherical cap harmonic analysis r scha can appropriately provide a continuous time field model for the north atlantic region by using multilevel sets of geomagnetic data such as marine repeat station observatory and satellite data taking advantage of the properties of the r scha basis functions we can model the radial and horizontal variations of the main field and its secular variation with the most suitable spatial and temporal wavelengths to assess the best compromise between the data fit and the model roughness temporal and spatial regularization matrices were implemented in the modelling approach two additional strategies were also used to obtain a satisfactory regional model the opportunity to fit the anomaly bias at each observatory location and constraining the regional model to the chaos 6 model at the end of its period of validity i e 1999 2000 allowing a smooth transition with the predictions of this recent model in terms of the root mean square error the degree of success was limited partly because of the high uncertainties associated with some of the datasets especially the marine ones but we have produced a model that performs comparably to the global models for the period 1960 2000 thus showing the benefits of using this regional technique

rock specific hydraulic fracturing and matrix acidizing to enhance a geothermal system concepts and field results abstract enhanced geothermal systems egs are engineered reservoirs developed to extract economic amounts of heat from low permeability and or porosity geothermal resources to enhance the productivity of reservoirs a site specific concept is necessary to actively make reservoir conditions profitable using specially adjusted stimulation treatments such as multi fracture concepts and site specific well path design the results of previously performed stimulation treatments in the geothermal research well gtgrsk4 05 at gros schonebeck germany are presented the reservoir is located at a 4100 4300 m depth within the lower permian of the ne german basin with a bottom hole temperature of 150 c the reservoir rock is classified by two lithological units from bottom to top volcanic rocks andesitic rocks and siliciclastics ranging from conglomerates to fine grained sandstones fluvial sediments the stimulation treatments included multiple hydraulic stimulations and an acid treatment in order to initiate a cross flow from the sandstone layer the hydraulic stimulations were performed in different depth sections two in the sandstone section and one in the underlying volcanic section in low permeability volcanic rocks a cyclic hydraulic fracturing treatment was performed over 6 days in conjunction with adding quartz in low concentrations to maintain a sustainable fracture performance flow rates of up to 150 l s were realized and a total of 13 170 m3 of water was injected a hydraulic connection to the sandstone layer was successfully achieved in this way however monitoring of the water level in the offsetting well egrsk3 90 which is 475 m apart at the final depth showed a very rapid water level increase due to the stimulation treatment this can be explained by a connected fault zone within the volcanic rocks two gel proppant treatments were performed in the slightly higher permeability sandstones to obtain long term access to the reservoir rocks during each treatment a total of 100 ton of high strength proppants was injected with 500 m3 of cross linked gel the subsequent production test in conjunction with flowmeter logging showed an improvement of productivity by a factor of more than 4 due to assumed residual drilling mud constituents calcite dolomite and aragonite in the near wellbore vicinity an acid matrix stimulation was performed thereafter using a coil tubing unit the following nitrogen lift test demonstrated another increase of productivity by 30 50 to an overall increase by a factor of 5 5 6 2