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  • 1
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    Bayesian Forecast Evaluation and Ensemble Earthquake Forecasting (2013)
    Seismological Society of America
    Details
    Publication Date: 2021-06-25
    Description: The assessment of earthquake forecast models for practical purposes requires more than simply checking model consistency in a statistical framework. One also needs to understand how to construct the best model for specific forecasting applications. We describe a Bayesian approach to evaluating earthquake forecasting models, and we consider related procedures for constructing ensemble forecasts. We show how evaluations based on Bayes factors, which measure the relative skill among forecasts, can be complementary to common goodness-of-fit tests used to measure the absolute consistency of forecasts with data. To construct ensemble forecasts, we consider averages across a forecast set, weighted by either posterior probabilities or inverse log- likelihoods derived during prospective earthquake forecasting experiments. We account for model correlations by conditioning weights using the Garthwaite–Mubwandarikwa capped eigenvalue scheme. We apply these methods to the Regional Earthquake Like- lihood Models (RELM) five-year earthquake forecast experiment in California, and we discuss how this approach can be generalized to other ensemble forecasting applications. Specific applications of seismological importance include experiments being conducted within the Collaboratory for the Study of Earthquake Predictability (CSEP) and ensemble methods for operational earthquake forecasting.
    Description: Published
    Description: 2574 – 2584
    Description: 4.2. TTC - Modelli per la stima della pericolosità sismica a scala nazionale
    Description: JCR Journal
    Description: restricted
    Keywords: earthquake forecasting ; ensemble model ; 04. Solid Earth::04.06. Seismology::04.06.02. Earthquake interactions and probability
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
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    Operational earthquake forecasting can enhance earthquake preparedness (2015)
    Seismological Society of America
    Details
    Publication Date: 2021-06-25
    Description: We cannot yet predict large earthquakes in the short term with much reliability and skill, but the strong clustering exhibited in seismic sequences tells us that earthquake probabilities are not constant in time; they generally rise and fall over periods of days to years in correlation with nearby seismic activity. Opera- tional earthquake forecasting (OEF) is the dissemination of authoritative information about these time-dependent proba- bilities to help communities prepare for potentially destructive earthquakes. The goal of OEF is to inform the decisions that people and organizations must continually make to mitigate seismic risk and prepare for potentially destructive earthquakes on time scales from days to decades. To fulfill this role, OEF must provide a complete description of the seismic hazard—ground-motion exceedance probabilities as well as short-term rupture probabilities—in concert with the long-term forecasts of probabilistic seismic-hazard analysis (PSHA).
    Description: Published
    Description: 955-959
    Description: 3T. Pericolosità sismica e contributo alla definizione del rischio
    Description: JCR Journal
    Description: reserved
    Keywords: Operational earthquake forecasting ; seismic preparedness ; 04. Solid Earth::04.06. Seismology::04.06.11. Seismic risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 3
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    Feasibility study of repurposing Trenton-Black River gas fields for geothermal heat extraction, southern New York (2017)
    Geological Society of America (GSA)
    In: Geosphere
    Details
    Publication Date: 2017-01-29
    Description: Geothermal resources have the potential to fulfill a significant portion of the low-temperature (30–100 °C) thermal energy demand in the United States. Investment risk at the exploration stage is a primary factor limiting the development of geothermal energy projects, due to the high cost of drilling and limited reservoir data. An approach to reduce this risk is to target proven, well-characterized conventional oil and gas reservoirs. We examined the suitability of the Trenton–Black River gas fields of southern New York as geothermal reservoirs. These highly productive hydrothermal dolomite fields occur within long, narrow normal-fault–bounded, en echelon grabens that are scattered with saddle dolomite-lined vugs, fractures, and breccia. The Quackenbush Hill field was analyzed using existing data sets with geothermal purposes in mind. Key geothermal reservoir characteristics examined here include rock temperature, porosity and permeability, stimulation potential, and the risk of inducing seismicity. Results indicate that the Quackenbush Hill field would produce temperatures of ~91 °C from a dolomite reservoir with sufficient average horizontal permeability, low vertical permeability, and significant vertical and horizontal anisotropy. In the case that adequate flow rates cannot be achieved in practice, stimulation is a feasible option from the perspective of well-field design for optimal heat sweep; however, higher-resolution data are necessary to constrain the risk of inducing seismicity. We demonstrate the technical feasibility of transitioning conventional gas fields into geothermal heat-producing reservoirs, setting the stage for future consideration of the economics of a petroleum-to-geothermal transition.
    Electronic ISSN: 1553-040X
    Topics: Geosciences
    Published by Geological Society of America (GSA)
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  • 4
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    Landscape modification in response to repeated onset of hyperarid paleoclimate states since 14 Ma, Atacama Desert, Chile (2014)
    Geological Society of America (GSA)
    Details
    Publication Date: 2014-06-28
    Description: The landscape of the hyperarid Atacama Desert in northern Chile records extremely slow change on Earth’s surface. Disputed ages for the onset of hyperaridity range from the late Paleogene through the Pleistocene. A long-term paleoclimate record is recorded in a nonmarine basin whose fill is primarily alluvial strata. For this setting, the primary proxies for climate state are the mineralogical and chemical composition of soil, which varies across a precipitation gradient, and the landforms and deposits of alluvial fans. During the most recent ~15 million years, five climate-related landscape stages are resolved for the Pampa del Tamarugal sedimentary basin, with each successively younger stage inset lower in the local topography than its predecessor. The earliest landscape stage is expressed as a set of alluvial strata inherited from a time of arid or semi-arid climate, ca. 14–12 Ma. The younger four landscape stages generated a composite long-lasting exposure surface. Predominantly hyperarid conditions have persisted since ca. 12 ± 1 Ma, during which four intervals of arid to semi-arid climate occurred. Each wet interval was short lived, a million years or less, whereas some of the hyperarid periods were lengthy, 1–5 m.y. The hyperarid intervals were roughly 11–5.5 Ma, 4.5–4 Ma, 3.6–2.6 Ma, 2.2–1 Ma, and repeated intervals during the last 1 m.y. The onset of hyperaridity ca. 12 Ma likely reflects the growth of the Andes Mountains above a climate threshold. In contrast, sea surface temperature variability likely has controlled Atacama paleoclimate changes since the late Miocene.
    Print ISSN: 0016-7606
    Electronic ISSN: 1943-2674
    Topics: Geosciences
    Published by Geological Society of America (GSA)
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  • 5
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    A temperate former West Antarctic ice sheet suggested by an extensive zone of subglacial meltwater channels (2014)
    Geological Society of America (GSA)
    In: Geology
    Details
    Publication Date: 2014-11-04
    Description: Several recent studies predict that the West Antarctic Ice Sheet will become increasingly unstable under warmer conditions. Insights on such change can be assisted through investigations of the subglacial landscape, which contains imprints of former ice-sheet behavior. Here, we present radio-echo sounding data and satellite imagery revealing a series of ancient large sub-parallel subglacial bed channels preserved in the region between the Möller and Foundation Ice Streams, West Antarctica. We suggest that these newly recognized channels were formed by significant meltwater routed along the ice-sheet bed. The volume of water required is likely substantial and can most easily be explained by water generated at the ice surface. The Greenland Ice Sheet today exemplifies how significant seasonal surface melt can be transferred to the bed via englacial routing. For West Antarctica, the Pliocene (2.6–5.3 Ma) represents the most recent sustained period when temperatures could have been high enough to generate surface melt comparable to that of present-day Greenland. We propose, therefore, that a temperate ice sheet covered this location during Pliocene warm periods.
    Print ISSN: 0091-7613
    Electronic ISSN: 1943-2682
    Topics: Geosciences
    Published by Geological Society of America (GSA)
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  • 6
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    The Ellsworth Subglacial Highlands: Inception and retreat of the West Antarctic Ice Sheet (2013)
    Geological Society of America (GSA)
    Details
    Publication Date: 2013-12-31
    Description: Antarctic subglacial highlands are where the Antarctic ice sheets first developed and the "pinning points" where retreat phases of the marine-based sectors of the ice sheet are impeded. Due to low ice velocities and limited present-day change in the ice-sheet interior, West Antarctic subglacial highlands have been overlooked for detailed study. These regions have considerable potential, however, for establishing the locations from which the West Antarctic Ice Sheet originated and grew, and its likely response to warming climates. Here, we characterize the subglacial morphology of the Ellsworth Subglacial Highlands, West Antarctica, from ground-based and aerogeophysical radio-echo sounding (RES) surveys and the Moderate-Resolution Imaging Spectroradiometer (MODIS) Mosaic of Antarctica. We document well-preserved classic landforms associated with restricted, dynamic, marine-proximal alpine glaciation, with hanging tributary valleys feeding a significant overdeepened trough (the Ellsworth Trough) cut by valley (tidewater) glaciers. Fjord-mouth threshold bars down-ice of two overdeepenings define both the northwest and southeast termini of paleo-outlet glaciers, which cut and occupied the Ellsworth Trough. Satellite imagery reveals numerous other glaciated valleys, terminating at the edge of deep former marine basins (e.g., Bentley Subglacial Trench), throughout the Ellsworth Subglacial Highlands. These geomorphic data can be used to reconstruct the glaciology of the ice masses that formed the proto–West Antarctic Ice Sheet. The landscape predates the present ice sheet and was formed by a small dynamic ice field(s), similar to those of the present-day Antarctic Peninsula, at times when the marine sections of the West Antarctic Ice Sheet were absent. The Ellsworth Subglacial Highlands represent a major seeding center of the paleo–West Antarctic Ice Sheet, and its margins represent the pinning point at which future retreat of the marine-based West Antarctic Ice Sheet would be arrested.
    Print ISSN: 0016-7606
    Electronic ISSN: 1943-2674
    Topics: Geosciences
    Published by Geological Society of America (GSA)
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  • 7
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    Geothermal energy characterization in the Appalachian Basin of New York and Pennsylvania (2015)
    Geological Society of America (GSA)
    In: Geosphere
    Details
    Publication Date: 2015-09-30
    Description: Analysis of geothermal energy resources in the Appalachian Basin of the eastern United States is of interest, given the region’s population- and climate-driven demand for thermal energy. This study provides a fuller picture of geothermal resources across New York and Pennsylvania than previous studies by providing a rigorous statistical analysis of temperature-depth data using records from nearly 8000 locations. The compilation of thousands of temperature-depth data enables a significant increase in the spatial resolution of geothermal resource assessment maps for this region. In addition, this project has contributed to the compilation of geothermal data at a national level through the National Geothermal Data System. These temperature-depth measurements are byproducts of historical and recent drilling for petroleum and natural gas in the sedimentary basin. Bottom hole temperatures (BHTs) were recorded before the wells reached thermal equilibrium and at a wide range of depths. To extract a comprehensive description of the thermal state of the Appalachian Basin strata required application of both a BHT correction scheme and a simple thermal model. The model results for individual wells were combined with geostatistical interpolation employing kriging to produce maps that reveal significant variations in subsurface thermal gradient and surface heat flow with markedly improved spatial resolution. An area in south-central New York State displays favorable geothermal resource potential, with heat flow estimates of 50–60 mW/m 2 . There are 2 elongate, 200–300 km long, northeast-trending bands of favorable geothermal resource potential in central and western Pennsylvania, with heat flow of 55–90 mW/m 2 .
    Electronic ISSN: 1553-040X
    Topics: Geosciences
    Published by Geological Society of America (GSA)
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  • 8
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    Architecture of the aquifers of the Calama Basin, Loa catchment basin, northern Chile (2015)
    Geological Society of America (GSA)
    In: Geosphere
    Details
    Publication Date: 2015-09-30
    Description: In the Loa water system of the Atacama Desert in northern Chile, careful management of groundwater is vital and data are sparse. Several key management questions focus on aquifers that occur in the Calama sedimentary basin, through which groundwater and Loa surface water flow to the west. The complexity of the two major aquifers and their discharge to wetlands and rivers are governed by primary facies variations of the sedimentary rocks as well as by faults and folds that create discontinuities in the strata. This study integrates geological studies with groundwater hydrology data to document how the aquifers overlay the formations and facies. Neither the phreatic aquifer nor the confined or semiconfined aquifer, each of which is identified in most basin sectors, corresponds to a laterally persistent geological unit. The variable properties of low-permeability units sandwiched between units of moderate to high permeability cause a patchwork pattern of areas in which water is exchanged between the two aquifers and areas where the lower aquifer is confined. The westward termination of most of the sedimentary rocks against a north-trending basement uplift at an old fault zone terminates the principal aquitard and the lower aquifer. That termination causes lower aquifer water to flow into the upper aquifer or discharge to the rivers. The regionally important West fault juxtaposes formations with differing lithological and hydraulic properties, resulting in some exchange of water between the upper and lower aquifers across the fault.
    Electronic ISSN: 1553-040X
    Topics: Geosciences
    Published by Geological Society of America (GSA)
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