Receiver functions are produced by deconvolving the horizontal components of a seismogram vertical component. Typically this is performed spectral division recordings single events. from events with similar backazimuth and ray parameter then stacked to improve signal-to-noise ratio. To avoid subjective time-consuming method prewhitening typically employed division, we have cast deconvolution in time domain. By performing time-domain as regularized simultaneous inversion for group that would...

The ambient infrasound noise environment is characterized for 21 globally distributed arrays in the frequency band of 0.03 to 7 Hz. Power Spectral Density (PSD) measured one site each array intervals at four times day from January 2003 through 2004. stations highly variable by season, time and station. Noise spectra an individual station may vary orders magnitude any given frequency. Preliminary models are defined, which can be used as baselines evaluating current new stations. Median levels...

Abstract Earthquake hypocenters within the subducting Juan de Fuca plate beneath Washington and northern Oregon are interpreted as showing that direction of dip changes from northeast Puget Sound region to east-southeast southwestern Washington. The shallowest between 30- 40-km depth, distribution these events strikes north-northeast near mouth Columbia River Olympic Mountains. 40 50 km generally parallel with events, but shows a significant broadening eastern Mountains Sound. Events depths...

We used a dense seismic network to test the P / S amplitude ratio discriminant for earthquakes and explosions at distances from 20 200 km in complex tectonic setting. data several hundred stations northern Wyoming observe 22 earthquakes, 37 mining blasts, 24 borehole shots compared their ratios. Frequencies of 6–8 Hz above achieved best discrimination results single‐shot explosions, whereas 6–8 8–10 Hz passbands were blasts. The method appears valid 50–200 km but fails <50  km. Geologic...

Backazimuth estimates derived from surface wave polarization can be used to test association of an observed with a seismic event. However, commonly techniques for estimating the backazimuth are subject number errors and often inaccurate. We evaluate performance new algorithm determining Rayleigh propagation direction cross‐correlation horizontal Hilbert transformed vertical seismograms. This proves more accurate much less error‐prone than current automatic processing procedures, value...

Abstract Teleseismic P, SH, and SV first motions SH to amplitude ratios recorded at eight teleseismic receivers from the 1949 magnitude 7.1 Olympia, Washington, earthquake in combination with data three stations regional distances were utilized a grid testing routine constrain focal mechanism. Identification of pP phase places event 54 km depth. Distinct pulses, assumed be source effects, are observed far-field waveforms. Analysis these pulses for directivity made possible discrimination...

Abstract We use teleseismic P waves recorded at Piñon Flat Observatory (PFO) to constrain the three-dimensional crustal and upper-mantle velocity structure beneath station. By forward modeling radial receiver function waveforms, we construct a one-dimensional model that includes significant shear-velocity inversion 9 km in depth. Arrivals on tangential components indicate dip of least uppermost discontinuity. Complicated Moho topography, deepening northwest PFO, is suggested by azimuthal...

Lg group velocities are slower for very shallow events than deeper crustal in both southern California and Israel. An velocity depth discriminant applied to data below 1 Hz was proposed then abandoned two decades ago, but a more precise measure of the energy distribution within leads conclusion that higher frequency may identify event depth. Because its practical importance nuclear monitoring implications generation propagation , we quantify model delay shallow-event . We consider...

We evaluate the mechanisms responsible for generation of shear waves by explosions in high‐velocity source media identifying, quantifying, and modeling observations that can distinguish between commonly suggested mechanisms. review literature to identify regional have been or be used two more supplement these historical with new measurements Semipalatinsk test site (STS) event Lg P amplitudes at Borovoye model nonlinear models, Rg ‐to‐ upper bound calculations, wavenumber integration...

Abstract The detection of the high‐frequency fundamental‐mode Rayleigh‐wave Rg is important for explosion monitoring efforts because it indicates a shallow source, which most often man‐made. We developed an automated detector that successfully identifies using spectrogram seismic signal to find peaks in characteristic frequency band. tested network over 200 seismometers Wyoming, recorded dozens nearby coal‐mining blasts and active‐source tamped borehole shots. finds summed amplitudes from...

We develop a general solution for seismic wave generation by an explosion source in spherical cavity, and then specific point offset from the cavity center. find that causes dipole component to which generates S waves angular variation P amplitude shape. The vanish at zero frequency but may be sizable fraction of frequencies interest. also perform nonlinear axisymmetric calculation complex due reverberations comparable those found analytic solution. has application shear decoupled...

Abstract We use conservation of energy to place an upper bound on Lg generated by explosions through Rg scattering. assume that all in scatters very rapidly into the higher mode surface waves make up . consider directly explosion source and a collocated but possibly shallower compensated linear vector dipole (CLVD) source. scattering may be viable mechanism for generating at low frequencies ( CLVD or is comparable greater than For shallow sources 2–3 Hz direct smaller limit scattered waves....

Research Article| November 21, 2017 Evaluating Local Distance Seismic Amplitude Measurements as Predictors of Event Magnitude in a Tectonically Complex Setting Colin T. O'Rourke; O'Rourke aAir Force Laboratory, Nuclear Explosion Monitoring, Kirtland AFB, New Mexico 87117, colin.orourke@colorado.edu Search for other works by this author on: GSW Google Scholar G. Eli Baker Author and Article Information Publisher: Seismological Society America First Online: 21 Nov Online Issn: 1943-3573 Print...

Rg scattering has often been suggested as the source of regional Lg phase generated by explosions (e.g., Patton and Taylor, 1995; Gupta Wagner, 1998). The main point our paper (Stevens et al. , 2009) was that it is very difficult to get enough energy out generate observed direct generation S or pS conversion are likely be stronger sources than scattering. To compare contributions each mechanism, we derived an upper bound on possible size -to- assuming 100% scattered quickly into with no loss...