William Foxall - Academia.edu (original) (raw)

Papers by William Foxall

We have developed a methodology for synthesizing broadband ground motion that incorporates the ef... more We have developed a methodology for synthesizing broadband ground motion that incorporates the effects of earthquake rupture along specific faults and the actual geology between the source and site. The source model is simple, but based on the physics of earthquake rupture. We compute ground motions for finite rupture models with the Green’s function summation solution of the representation relation that uses empirical Green’s functions for high frequencies and synthetic Green's functions for low frequencies. The same source model is used for both high and low frequencies, so merged, broad-band Green's functions can be used. Parameters used for modeling the source are derived from dynamic modeling, field observations and laboratory studies, and therefore are based upon epistemic uncertainty and provides a means for narrowing uncertainty in analysis. We are using the fully dynamic code PyLith to investigate dynamic rupture parameters. We generate rupture scenarios that span the variability of potential ground motion in a predictive situation. This considers ruptures on “unidentified faults” and rupture scenarios not previously encountered in the historical data base. Output from this approach is a library of source- and site-specific ground-motion time series comprising a sample of all the earthquakes that could affect a site during its design life. The library of seismograms can be used either to develop hazard curves of traditional engineering parameters in the form of the annual probability of exceedance or to develop risk estimates from dynamic analysis of structures. The methodology has been validated by “predicting” ground motion for 15 moderate and large earthquakes throughout the world. In addition it has generated ground motion not previously observed that was subsequently recorded in the M7.5 1999 Taiwan, M7.4 1999 Izmit, M7.3 1992 Landers, and the M6.2 2004 Firoozabad-Kojoor, Iran earthquake, and we demonstrated that when physical constraints were applied to the M6.0 1997 Colfiorito, Italy earthquake we narrowed the bounds of uncertainty in the ground motion prediction. We expanded the methodology by extending it to all significant magnitudes for a PSHA in the northern area of the Saronikos Gulf (Greece) and predicting the effects of a great earthquake near Tehran, Iran.

&lt;p&gt;The Mont Terri rock laboratory, located in the Swiss Jura Mountains, is ... more &lt;p&gt;The Mont Terri rock laboratory, located in the Swiss Jura Mountains, is dedicated to research on argillaceous rocks. Since its founding in 1996, the objective is the hydrogeological, geochemical, and geotechnical characterisation of Opalinus Clay in the context of nuclear waste repositories. More recently, the work has broadened to additional fields, covering potential uses of the deep geological subsurface such as geological storage of carbon dioxide and geothermal energy. With the excellent infrastructure, a comprehensive database, and the broad scientific and technological expertise, knowledge is enhanced e.g. through the advancement and comparison of approaches as well as the development and testing of novel investigation methods. These, as well as studies on feasibility and risk assessment, are of benefit also for underground laboratories in general and in situ explorations in different rock types worldwide. Due to the long-term commitment and the available gallery space of the research facility, elaborate as well as decade-long experiments can be implemented.&lt;/p&gt;&lt;p&gt;In order to detect, quantify, and understand short- and long-term deformations in the Mont Terri rock laboratory, quasi continuous time series are established employing various monitoring techniques. The latter complement each other in regard to their spatial dimensions, operational frequency optima, and their point or integral information. The approach combines&lt;/p&gt;&lt;ul&gt;&lt;li&gt;a 50&amp;#160;m long uniaxial hydrostatic levelling system (HLS, Type &amp;#8220;PSI&amp;#8221;, positioned along a gallery wall, measuring principle: electrical plate capacitors),&lt;/li&gt; &lt;li&gt;four mini-arrays of very-broad-band triaxial seismometers, installed in the rock laboratory (one under the HLS) as well as outside the rock laboratory at the surface,&lt;/li&gt; &lt;li&gt;and an array of high resolution, biaxial platform tiltmeters, with instruments situated close to the HLS and in various parts of the rock laboratory, integrated in other in situ experiments.&lt;/li&gt; &lt;/ul&gt;&lt;p&gt;The observed signals and their analysis differ in space and time. They range from the detection of local nanoseismic as well as large tele seismic events, to the determination of earth tides, and to the identification of seasonal trends versus other long term geodetic movements. Besides the mutual comparison of the three deformation measurements, the time series provide valuable input for numerous scientific questions such as the stability of the rock laboratory as a whole or in its parts, the influence of excavation, ventilation, or fluid injection on rock matrix and faults. Long data series of ambient parameters, essential for interpretation of the deformation records, such as temperature, pressure, and humidity, are recorded by sensors integrated in the above listed instruments and are also of interest in further experiments performed by the Mont Terri Consortium.&lt;/p&gt;

Author(s): Long, Jane; Feinstein, Laura; Bachmann, Corinne; Birkholzer, Jens; Camarillo, Mary; Do... more Author(s): Long, Jane; Feinstein, Laura; Bachmann, Corinne; Birkholzer, Jens; Camarillo, Mary; Domen, Jeremy; Foxall, William; Houseworth, James; Jin, Ling; Jordan, Preston; Lindsey, Nathaniel; Maddalena, Randy; McKone, Thomas; Millstein, Dev; Reagan, Matthew; Sandelin, Whitney; Stringfellow, William; Varadharajan, Charuleka; Cooley, Heather; Donelly, Kristina; Heberger, Matthew; Hays, Jake; Shonkoff, Seth; Brandt, Adam; Englander, Jacob; Hamdoun, Amro; Nicklisch, Sascha; Harrison, Robert; Wettstein, Zachary; Banbury, Jenner; Cypher, Brian; Phillips, Scott | Abstract: In 2013, the California Legislature passed Senate Bill 4 (SB 4), setting the framework for regulation of well stimulation technologies in California, including hydraulic fracturing. SB 4 also requires the California Natural Resources Agency to conduct an independent scientific study of well stimulation technologies in California. SB 4 stipulates that the independent study assess current and potential future well stimul...

We test a methodology to predict the range of ground-motion hazard for a fixed magnitude earthqua... more We test a methodology to predict the range of ground-motion hazard for a fixed magnitude earthquake along a specific fault or within a specific source volume, and we demonstrate how to incorporate this into probabilistic seismic hazard analyses (PSHA). We modeled ground motion with empirical Green's functions. We tested our methodology with the 7 September 1999, Mw=6.0 Athens earthquake, we: (1) developed constraints on rupture parameters based on prior knowledge of earthquake rupture processes and sources in the region; (2) generated impulsive point shear source empirical Green's functions by deconvolving out the source contribution of M < 4.0 aftershocks; (3) used aftershocks that occurred throughout the area and not necessarily along the fault to be modeled; (4) ran a sufficient number of scenario earthquakes to span the full variability of ground motion possible; (5) found that our distribution of synthesized ground motions span what actually occurred and their distri...

Geophysical Journal International, 2021

SUMMARY Estimates of line-of-sight (LOS) displacements from Interferometric Synthetic Aperture Ra... more SUMMARY Estimates of line-of-sight (LOS) displacements from Interferometric Synthetic Aperture Radar (InSAR) observations serve as the basis of the long-term monitoring of an operating natural gas storage site at Honor Rancho in California. An inversion algorithm is used to estimate the portion of the signal that is attributable to deformation within the gas storage reservoir, located at a depth of around 3 km. Removing this contribution produces residuals that are used to characterize the background variation is surface deformation at the gas storage facility and to determine a threshold that can signify unusually large residuals. An application to almost 7 yr of InSAR data, from 2011 until 2018, indicates that there are intervals of heightened residuals as well as brief episodes of anomalously large misfits. An examination of the spatial distributions of the individual residual LOS displacements indicates larger displacements in an alluvial valley just south of the reservoir, with...

Geological Carbon Storage, 2018

Earth and Planetary Science Letters, 2018

International Journal of Greenhouse Gas Control, 2017

Journal of Rock Mechanics and Geotechnical Engineering, 2016

Pure and Applied Geophysics, 2017

Surface displacements caused by reservoir pressure perturbations resulting from CO2 injection can... more Surface displacements caused by reservoir pressure perturbations resulting from CO2 injection can often be measured by geodetic methods such as InSAR, tilt and GPS. We have developed a Markov Chain Monte Carlo (MCMC) approach to invert surface displacements measured by InSAR to map the pressure distribution associated with CO2 injection at the In Salah Krechba field, Algeria. The MCMC inversion entails sampling the solution space by proposing a series of trial 3D pressure-plume models. In the case of In Salah, the range of allowable models is constrained by prior information provided by well and geophysical data for the reservoir and possible fluid pathways in the overburden, and injection pressures and volumes. Each trial pressure distribution source is run through a (mathematical) forward model to calculate a set of synthetic surface deformation data. The likelihood that a particular proposal represents the true source is determined from the fit of the calculated data to the InSAR...

This paper tests a new approach to predict a range of ground motion hazard at specific sites gene... more This paper tests a new approach to predict a range of ground motion hazard at specific sites generated by earthquakes on specific faults. The approach utilizes geodynamics to link structural, lithological and Theological descriptions of the fault zones to development of fault rupture scenarios and computation of synthetic seismograms. Faults are placed within a regional geomechanical model that is used to calculate stress conditions along the fault. The approach is based upon three hypothesis: (1) An exact solution of the representation relation that u@s empirical. Green`s functions enables very accurate computation of ground motions generated by a given rupture scenario; (2) a general description of the rupture is sufficient; and (3) the structural, lithological and Theological characteristics of a fault can be used to constrain, in advance, possible future rupture histories. Ground motion hazard here refers to three-component, full wave train descriptions of displacement, velocity...