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Berger, J, Davis P, Widmer‐Schnidrig R, Zumberge M.  2014.  Performance of an optical seismometer from 1 μHz to 10 Hz. Bulletin of the Seismological Society of America. 104:2422-2429.   10.1785/0120140052   AbstractWebsite

We compare the performance of four different instruments that measure the vertical component of motion of an inertial mass—an STS1 seismometer, an STS2 seismometer, a superconducting gravity meter, and an optical seismometer—operating inside the mine at the Black Forest Observatory near Schiltach in southwest Germany. Simultaneous, collocated operation of these sensors offers an opportunity to test the calibration, response, and performance of each instrument. We estimate noise floors from the tidal bands to 10 Hz. We note small nonlinearities in the suspension of the STS1, which are normally suppressed by analog signal processing and feedback or, in the optical version, by digital signal processing alone. The results demonstrate that the optical seismometer utilizing an STS1 suspension can provide observatory‐quality data over a bandwidth from tidal frequencies to at least 10 Hz and over a large dynamic range.

Davis, P, Berger J.  2012.  Initial impact of the global seismographic network quality initiative on metadata accuracy. Seismological Research Letters. 83:697-703., El Cerrito, CA, United States (USA): Seismological Society of America, El Cerrito, CA   10.1785/0220120021   Website
Davis, P, Berger J.  2007.  Calibration of the global seismographic network using tides. Seismological Research Letters. 78:454-459.   10.1785/gssrl.78.4.454   Website
Davis, P, Ishii M, Masters G.  2005.  An assessment of the accuracy of GSN sensor response information. Seismological Research Letters. 76:678-683.Website
Park, J, Song T-RA, Tromp J, Okal E, Stein S, Roult G, Clevede E, Laske G, Kanamori H, Davis P, Berger J, Braitenberg C, van Camp M, Lei X'e, Sun H, Xu H, Rosat S.  2005.  Earth's free oscillations excited by the 26 December 2004 Sumatra-Andaman earthquake. Science. 308:1139-1144.
Park, J, Butler R, Anderson K, Berger J, Benz H, Davis P, Hutt CR, McCreery CS, Ahern T, Ekstrom G, Aster R.  2005.  Performance Review of the Global Seismographic Network for the Sumatra Andaman Megathrust Earthquake. Seismological Research Letters. 76:331-343.: Seismological Society of America, 201 Plaza Professional Bldg , El Cerrito, CA, 94530, USA, [URL:]   10.1029/2004jb003408.   AbstractWebsite

On 26 December 2004, a 1,200-km length of seafloor boundary between the India Plate and Burma microplate ruptured in the Sumatra-Andaman earthquake. This earthquake was one of the five largest earthquakes of the past century and the largest in the past four decades. The SumatraAndaman earthquake is the first large tsunamigenic event and the first with an estimated Mw > 9 to be recorded by the Global Seismographic Network (GSN; Figure 1; Butler et al., 2004), as well as the observatories of the broader Federation of Digital Seismographic Networks (FDSN; Dziewonski, 1994). Earthquakes with Mw > 8 are commonly termed "great" earthquakes, but those with Mw > 8.7, not experienced on Earth since the 1960's, present hazards to lives and property that are far more extensive than a typical "great" earthquake. We therefore adopt the term "megathrust earthquake" after the common usage among paleoseismologists for exceptionally destructive earthquakes in the past (e.g., Priest et al., 2000; Cummins et al., 2001; Leonard et al., 2004).

Berger, J, Davis P, Ekstrom G.  2004.  Ambient Earth noise: A survey of the Global Seismographic Network. Journal of Geophysical Research-Solid Earth. 109   10.1029/2004jb003408   AbstractWebsite

It has been a decade since the last comprehensive model of ambient Earth noise was published (Peterson, 1993). Since then, observations of ambient Earth noise from the Incorporated Research Institutions for Seismology (IRIS) Global Seismographic Network (GSN) of widely distributed, similarly equipped, and well-calibrated stations have become available. The broad geographic sampling of this large data set and the ease of access to waveform data provided by the IRIS Data Management System facilitate analysis of global noise samples. We have analyzed data from the 118 GSN stations operating during the year July 2001 through June 2002. On the basis of over 738,000 hourly spectral estimates computed from these stations' data, we have developed a robust noise model that exhibits significant differences from previous models both in the normal mode and body wave bands. Our analysis technique has the advantage that we do not need to search for quiet periods but can include all data where the instruments are operating correctly.

Barker, B, Clark M, Davis P, Fisk M, Hedlin M, Israelsson H, Khalturin V, Kim W-Y, McLaughlin K, Meade C, North R, Orcutt J, Powell C, Richards PG, Stead R, Stevens J, Vernon F, Murphy J, Wallace T.  1998.  Monitoring nuclear tests. Science. 281:1967-1968.   10.1126/science.281.5385.1967   AbstractWebsite

In May 1998, the prototype monitoring systems for the Comprehensive Nuclear Test Ban Treaty (CTBT) provided effective and timely reporting on the Indian and Pakistani nuclear tests. More detailed analysis of a broad range of imagery and seismic data illustrates evolving capabilities for refining the test site locations and estimating the yields and number of explosions. The results demonstrate that there will be sufficient scientific and technical capabilities to perform global treaty monitoring to very low thresholds once the CTBT monitoring network is fully deployed.

Weber, M, Davis JP.  1990.  Evidence of a laterally variable lower mantle structure from P- and S-waves. Geophysical Journal International. 102:231-255., [London], United Kingdom (GBR): Blackwell, [London]Website
Davis, PJ, Weber M.  1990.  Lower mantle velocity inhomogeneity observed at GRF array. Geophysical Research Letters. 17:187-190., Washington, DC, United States (USA): American Geophysical Union, Washington, DC   10.1029/GL017i002p00187   AbstractWebsite

GRF broadband array recordings provide strong support for the existence of anomalous P-coda phases along the Kuriles - European path first observed using WWSSN data. The data suggest that the phase, termed here PdP, arrives 3-5s after the direct P-wave and has a slowness 0.7-0.8 s/deg smaller. The latter measurement precludes PdP's misidentification as a source stopping phase, and given the magnitude of the slowness difference, slab multipathing and diffraction are equally unlikely. Because the phase is clearly not observed for all Kurile events and from timing and geometric considerations, crustal reverberations are also untenable as an explanation for PdP's appearance. The hypothesis which best explains the PdP arrival time, arrival angle, and waveform is the presence of a 3% velocity jump in the lower mantle approximately 290 km above the core-mantle boundary. Because of the failure of other studies to observe PdP under favorable recording conditions, the reflector must be of limited regional extent beneath Northern Siberia. Copyright 1990 by the American Geophysical Union.

Davis, PJ, Sacks SI, Linde AT.  1989.  Source complexity of small earthquakes near Matsushiro, Japan. Tectonophysics. 166( Denham D, Ed.).:175-187., Amsterdam, Netherlands (NLD): Elsevier, AmsterdamWebsite
Davis, JP.  1987.  Local eigenfrequency and its uncertainty inferred from fundamental spheroidal mode frequency - shifts. Geophysical Journal of the Royal Astronomical Society. 88:693-722.   10.1111/j.1365-246X.1987.tb01652.x   Website
Davis, JP, Henson IH.  1986.  Validity of the great circular average approximation for inversion of normal mode measurements. Geophysical Journal of the Royal Astronomical Society. 85:69-92., London, United Kingdom (GBR): Blackwell [for the] Royal Astronomical Society, LondonWebsite
Davis, PJ.  1985.  Variation in apparent attenuation of the Earth's normal modes due to lateral heterogeneity. Geophysical Research Letters. 12:141-144., Washington, DC, United States (USA): American Geophysical Union, Washington, DC   10.1029/GL012i003p00141   AbstractWebsite

Study of 3242 full first order synthetic seismograms of isolated normal mode multiplets shows that constructive and destructive interference of the singlets comprising a multiplet can account for the noise-corrected variance of free oscillation attenuation measurements in the frequency band 3.0-4.0 mHz. This interference gives rise to a distribution of synthetic Q measurements which is sensitive to the short wavelength velocity features of a model. While individual attenuation measurements depend also on the moment tensor, the overall variance of Q fluctuations is insensitive to the characteristics of the source employed and depends little on the length of the time series processed. The Woodhouse-Dziewonski model M84A of upper mantle velocity structure causes a scatter in the synthetics large enough to interfere significantly with any signal from lateral Q structure. Correlation of individual synthetics with data is poor, however, which suggests that either there are remaining uncertainties in the velocity model, that mode-mode coupling occurs in the data in a way that is poorly understood, or that lateral attenuative structure contributes to the observed scatter. Resolution of any such Q structure will be difficult given the present data set.

Crampin, S, Evans R, Ucer B, Doyle M, Davis JP, Yegorkina GV, Miller A.  1980.  Observations of Dilatancy-Induced Polarization Anomalies and Earthquake Prediction. Nature. 286:874-877.Website