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Prieto, GA, Shearer PM, Vernon FL, Kilb D.  2004.  Earthquake source scaling and self-similarity estimation from stacking P and S spectra. Journal of Geophysical Research-Solid Earth. 109   10.1029/2004jb003084   AbstractWebsite

[1] We study the scaling relationships of source parameters and the self-similarity of earthquake spectra by analyzing a cluster of over 400 small earthquakes (M-L = 0.5 to 3.4) recorded by the Anza seismic network in southern California. We compute P, S, and preevent noise spectra from each seismogram using a multitaper technique and approximate source and receiver terms by iteratively stacking the spectra. To estimate scaling relationships, we average the spectra in size bins based on their relative moment. We correct for attenuation by using the smallest moment bin as an empirical Green's function (EGF) for the stacked spectra in the larger moment bins. The shapes of the log spectra agree within their estimated uncertainties after shifting along the omega(-3) line expected for self-similarity of the source spectra. We also estimate corner frequencies and radiated energy from the relative source spectra using a simple source model. The ratio between radiated seismic energy and seismic moment ( proportional to apparent stress) is nearly constant with increasing moment over the magnitude range of our EGF-corrected data (M-L = 1.8 to 3.4). Corner frequencies vary inversely as the cube root of moment, as expected from the observed self- similarity in the spectra. The ratio between P and S corner frequencies is observed to be 1.6 +/- 0.2. We obtain values for absolute moment and energy by calibrating our results to local magnitudes for these earthquakes. This yields a S to P energy ratio of 9 +/- 1.5 and a value of apparent stress of about 1 MPa.

Jacques, AA, Horel JD, Crosman ET, Vernon F, Tytell J.  2016.  The Earthscope US transportable array 1 Hz surface pressure dataset. Geoscience Data Journal. 3:29-36.   10.1002/gdj3.37   AbstractWebsite

A unique set of high temporal frequency surface atmospheric pressure observations have been collected and archived from a large-scale field campaign in the geosciences. The Earthscope U.S. Transportable Array (USArray TA) consists of approximately 400 deployable surface platforms. Stations were deployed in a Cartesian-like gridded fashion across a section of the contiguous United States for 1-2 year then retrieved and redeployed as new platforms further east. While primarily deployed for seismic measurements, platforms also recorded surface atmospheric pressure. These pressure data, collected and stored at a temporal frequency of 1 Hz, have been made available via the Research Data Archive at the National Center for Atmospheric Research (NCAR) for the time period 1 Jan 2010-31 Dec 2015. The 6 years of observations contain data from over 1000 locations ranging from the central to eastern United States, as well as some platforms in Alaska and the northwest United States. Data were organized as annual station files with supplemental metadata and quality control summary files. Several web-based interfaces are also available to rapidly explore the pressure archive. We describe the available dataset with several prominent atmospheric events shown as usage examples.

Kilb, D, Newman RL, Vernon FL, Eakins JA, Ziegler L, Bowen J, Otero J.  2003.  Education and outreach based on data from the Anza seismic network in Southern California. Seismological Research Letters. 74( Mellors RJ, Wald L, Eds.).:522-528., El Cerrito, CA, United States (USA): Seismological Society of America, El Cerrito, CAWebsite
Tanimoto, T, Lin C-J, Hadziioannou C, Igel H, Vernon F.  2016.  Estimate of Rayleigh-to-Love wave ratio in the secondary microseism by a small array at Piñon Flat observatory, California. Geophysical Research Letters. 43:11,173-11,181.   10.1002/2016GL071133   Abstract

Using closely located seismographs at Piñon Flat (PFO), California, for 1 year long record (2015), we estimated the Rayleigh-to-Love wave energy ratio in the secondary microseism (0.1–0.35 Hz) in four seasons. Rayleigh wave energy was estimated from a vertical component seismograph. Love wave energy was estimated from rotation seismograms that were derived from a small array at PFO. Derived ratios are 2–2.5, meaning that there is 2–2.5 times more Rayleigh wave energy than Love wave energy at PFO. In our previous study at Wettzell, Germany, this ratio was 0.9–1.0, indicating comparable energy between Rayleigh waves and Love waves. This difference suggests that the Rayleigh-to-Love wave ratios in the secondary microseism may differ greatly from region to region. It also implies that an assumption of the diffuse wavefield is not likely to be valid for this low frequency range as the equipartition of energy should make this ratio much closer.

Heuze, F, Archuleta R, Bonilla F, Day S, Doroudian M, Elgamal A, Gonzales S, Hoehler M, Lai T, Lavallee D, Lawrence B, Liu PC, Martin A, Matesic L, Minster B, Mellors R, Oglesby D, Park S, Riemer M, Steidl J, Vernon F, Vucetic M, Wagoner J, Yang Z.  2004.  Estimating site-specific strong earthquake motions. Soil Dynamics and Earthquake Engineering. 24:199-223.   10.1016/j.soildyn.2003.11.002   AbstractWebsite

The Campus Earthquake Program (CEP) of the University of California (UC) started in March 1996, and involved a partnership among seven campuses of the UC-Berkeley, Davis, Los Angeles, Riverside, San Diego, Santa Barbara, Santa Cruz-and the Lawrence Livermore National Laboratory (LLNL). The aim of the CEP was to provide University campuses with site-specific assessments of their earthquake strong motion exposure, to complement estimates they obtain from consultants according to the state-of-the-practice (SOP), i.e. Building Codes (UBC 97, IBC 2000), and Probabilistic Seismic Hazard Analysis (PSHA). The Building Codes are highly simplified tools, while the more sophisticated PSHA is still somewhat generic in its approach because it usually draws from many earthquakes not necessarily related to the faults threatening the site under study. Between 1996 and 2001, the site-specific studies focused on three campuses: Riverside, San Diego, and Santa Barbara. Each campus selected 1-3 sites to demonstrate the methods and procedures used by the CEP: Rivera Library and Parking Lots (PL) 13 and 16 at UCR, Thornton Hospital, the Cancer Center, and PL 601 at UCSD, and Engineering I building at UCSB. The project provided an estimate of strong ground motions at each selected site, for selected earthquake scenarios. These estimates were obtained by using an integrated geological, seismological, geophysical, and geotechnical approach, that brings together the capabilities of campus and laboratory personnel. Most of the site-specific results are also applicable to risk evaluation of other sites on the respective campuses. The CEP studies have provided a critical assessment of whether existing campus seismic design bases are appropriate. Generally speaking, the current assumptions are not acknowledging the severity of the majority of expected motions. Eventually, both the results from the SOP and from the CEP should be analyzed, to arrive at decisions concerning the design-basis for buildings on UC campuses. Published by Elsevier Ltd.

De Groot-Hedlin, CD, Vernon FL.  1998.  An evolutionary programming method for estimating layered velocity structure. Bulletin of the Seismological Society of America. 88:1023-1035. AbstractWebsite

For most geophysical inverse problems, one solves for an Earth model that minimizes the misfit between the observed data and observational predications determined from forward modeling. However, the solutions to such problems are almost always nonunique, as some of the model parameters are poorly resolved by the data. We have developed a novel form of evolutionary programming (EP) that solves directly for a broad cluster of models that adequately fit the data. We obtain improved performance of the EP algorithm by rotating the model parameter axes at each generation so that the axes are aligned perpendicular and parallel to long valleys in the misfit surface. The rotated axes are defined by the eigenvectors of the covariance matrix of the set of models; the mutation rate in each new direction varies with the square root of the corresponding eigenvalue, This modified EP method finds a wide range of models satisfying the data, allowing one to determine the uncertainty in the model parameters. We illustrate this EP method by applying it to the problem of determining velocity structure from regional travel-time data. Application of this method to a travel-time data set generated from a model that includes a low-velocity zone (LVZ) illustrates that it successfully finds a wide range of models within the broad minimum that includes the initial solution. We apply the method to regional travel-time data recorded at the Kyrgyz broadband network (KNET) and find that velocities are well resolved, except at depths of 25 to 50 km.