Calculation of the frequency response of the USGS telemetered short-period seismic system

Stewart, S. W.; O’Neill, M. E.

doi:10.3133/ofr80143

Cited by 22 publications

(15 citation statements)

References 5 publications

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“…The left panel contains a subset of the displacement data waveforms for the Fiji record section in the limited distance range of 82 ø to 83 ø , showing the spatial density of the data. To obtain the displacement waveforms, the original data were band-pass filtered between 0.2 and 10 hz and corrected for the short-period instrument response [Stewart and O'Neill, 1980]. The seismograms were lined up to a common start time by using the lag time that corresponded to the maximum cross correlation between the trace and an averaged version of all the traces.…”

Section: Datasupporting

confidence: 69%

Localized boundary layer below the mid‐Pacific velocity anomaly identified from a PcP precursor

Mori¹,

Helmberger²

1995

J. Geophys. Res.

142

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Dense record sections from deep earthquakes in Fiji and Argentina recorded on hundreds of short‐period stations in California at distances of 81° to 85° are used to investigate the detailed P wave velocity structure above the core‐mantle boundary (CMB). In the Fiji data a secondary phase arriving 2 to 4 s after the direct P is identified as a precursor to PcP. This phase provides good evidence for a reflection off the top of a thin low‐velocity layer above the CMB. Comparisons to synthetic seismograms indicate a layer thickness of 10 km and a velocity reduction of 5%–10% compared to the overlying mantle. A record section from an Argentina event does not show the PcP precursor, indicating that the low‐velocity layer is not a global feature. This thin low‐velocity layer is in the same place as a much larger S wave velocity anomaly in the lower mantle and is probably indicative of a boundary layer just above the CMB under the mid‐Pacific.

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Section: Datasupporting

confidence: 69%

Localized boundary layer below the mid‐Pacific velocity anomaly identified from a PcP precursor

Mori¹,

Helmberger²

1995

J. Geophys. Res.

142

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show abstract

“…Earthquakes are located with HYPOINVERSE [Klein, 1989] using a homogeneous layered crustal model determined from refraction studies [Catchings, 1983[Catchings, , 1987. For a full discussion of instrumentation and data processing, see Lester and Meagher [1978] and Stewart and O'Neill [1980]. Between 1980 and the September 1988 swarm (see below), only three earthquakes were located in the vicinity of Medicine Lake caldera.…”

Section: Seismicitymentioning

confidence: 99%

Crustal subsidence, seismicity, and structure near Medicine Lake Volcano, California

Dzurisin¹,

Donnelly‐Nolan²,

Evans³

et al. 1991

J. Geophys. Res.

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The pattern of historical ground deformation, seismicity, and crustal structure near Medicine Lake volcano illustrates a close relation between magmatism and tectonism near the margin of the Cascade volcanic chain and the Basin and Range tectonic province. Between leveling surveys in 1954 and 1989 the summit of Medicine Lake volcano subsided 389±43 mm with respect to a reference bench mark 40 km to the southwest (average rate = 11.1±1.2 mm/yr). A smaller survey across the summit caldera in 1988 suggests that the subsidence rate was 15–28 mm/yr during 1988–1989. Swarms of shallow earthquakes (M ≤ 4.6) occurred in the region during August 1978, January–February 1981, and September 1988. Except for the 1988 swarm, which occurred beneath Medicine Lake caldera, most historical earthquakes were located at least 25 km from the summit. The spatial relation between subsidence and seismicity indicates (1) radially symmetric downwarping of the volcano's summit and flanks centered near the caldera and (2) downfaulting of the entire edifice along regional faults located 25–30 km from the summit. We propose that contemporary subsidence, seismicity, and faulting are caused by (1) loading of the crust by more than 600 km3 of erupted products plus a large volume of mafic intrusives; (2) east‐west extension in the western Basin and Range province; and, to a lesser extent, (3) crystallization or withdrawal of magma beneath the volcano. Thermal weakening of the subvolcanic crust by mafic intrusions facilitates subsidence and influences the distribution of earthquakes. Subsidence occurs mainly by aseismic creep within 25 km of the summit, where the crust has been heated and weakened by intrusions, and by normal faulting during episodic earthquake swarms in surrounding, cooler terrain.

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“…Figure 5 shows an example of a digitally recorded seismogram from the Southern California Network and the ground displacement calculated first using a program originally written by Stewart and O'Neill (1980) and the ground displacement calculated using the poles and zeroes in the SAC program. The poles and zeroes in the SEED format follow the same convention as the SAC format.…”

Section: Poles and Zeroes For Usgs Short-period Instrumentmentioning

confidence: 99%

“…The following poles and zeroes for a typical USGS short-period instrument response were taken from a program written by Mary O'Neill and described in Stewart and O'Neill (1980). The sign convention is changed to conform to die SAC and SEED formats.…”

Section: Poles and Zeroes For Usgs Short-period Instrumentmentioning

confidence: 99%

The Southern California Network Bulletin January - December 1992

Wald¹,

Watts²,

Mori³

et al. 1993

Open-File Report

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Calculation of the frequency response of the USGS telemetered short-period seismic system

Cited by 22 publications

References 5 publications

Localized boundary layer below the mid‐Pacific velocity anomaly identified from a PcP precursor

Localized boundary layer below the mid‐Pacific velocity anomaly identified from a PcP precursor

Crustal subsidence, seismicity, and structure near Medicine Lake Volcano, California

The Southern California Network Bulletin January - December 1992

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