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At least 19 recordsLinked to original sources
USGS1999

Wide-angle seismic recordings from the 1998 Seismic Hazards Investigation of Puget Sound (SHIPS), western Washington and British Columbia

This report describes the acquisition and processing of deep-crustal wide-angle seismic reflection and refraction data obtained in the vicinity of Puget Lowland, the Strait of Juan de Fuca, and Georgia Strait, western Washington and southwestern British Columbia, in March 1998 during the Seismic Hazards Investigation of Puget Sound (SHIPS). As part of a larger initiative to better understand lateral variations in crustal structure along the Cascadia margin, SHIPS participants acquired 1000 km of deep-crustal multichannel seismic-reflection profiles and 1300 km of wideangle airgun shot lines in this region using the R/V Thompson and R/V Tully. The Tully was used to record airgun shots fired by the Thompson in two different geometries: (1) expanding spread profiles (ESPs) and (2) constant offset profiles (COPs). Prior to this reflection survey, we deployed 257 Reftek and 15 ocean-bottom seismic recorders to record the airgun signals at far offsets. All data were recorded digitally on large-capacity hard disks. Although most of these stations only recorded the vertical component of motion, 95 of these seismographs recorded signals from an oriented 3-component seismometer. By recording signals generated by the Thompson's marine air gun array, operated in two differing geometries having a total volume of 110 and 79 liters (6730 and 4838 cu. in.), respectively, the arrays of wide-angle recorders were designed to (1) image the crustal structure, particularly in the vicinity of crustal faults and Cenozoic sedimentary basins, (2) determine the geometry of the Moho, and (3) image the subducting Gorda and Juan de Fuca plates. Nearly 33,300 air gun shots were recorded along several seismic lines. In this report, we illustrate the expanding spread profiles acquired using the Thompson and Tully, describe the land and ocean-bottom recording of the air gun signals, discuss the processing of the land recorder data into common receiver gathers, and illustrate the processed wide-angle seismic data collected using the Refteks and ocean-bottom seismometers. We also describe the format and content of the archival tapes containing the SEGY-formated, common-receiver gathers for the Reftek data. Data quality is variable but SHIPS appears to have successfully obtained useful data from almost all the stations deployed to record the airgun shots. Several interesting arrivals were observed: including refractions from the sedimentary basin fill in several basins, refractions from basement rocks forming the upper crust, Pg, refractions from the upper mantle, Pn, as well as reflections from within the crust and from the top of the upper mantle, PmP. We separately archived more than 30 local earthquakes recorded by the Reftek array during our deployment.

Washington↗
USGS1978

Five-day recorder seismic system

The 10-day recorder seismic system used by the USGS since 1965 has been modified substantially to improve its dynamic range and frequency response, to decrease its power consumption and physical complexity, and to make its recordings more compatible with other NCER systems to facilitate data processing. The principal changes include: 1. increasing tape speed from 15/160 ips to 15/80 ips (reducing running time from 10 days to 5 days with a 14' reel of 1 mil tape), 2. increasing the FM center frequency by a factor of 4, from 84.4 Hz to 337.6 Hz, 3. replacing the original amplifiers and FM modulators with new low-power units, 4. replacing the chronometer with a higher quality time code generator (with IRIG-C) to permit automation of data retrieval, 5. eliminating the amplifier/WWVB radio field case by incorporating these elements, along with the new TCG, in the weatherproof tape-recorder box, 6. reducing the power consumption of the motor-drive circuit by removal of a redundant component. In the new system, the tape-recorder case houses all components except the seismometers, the WWVB antenna, the 70-amp-hour 12-VDC battery (which powers the system for 5 days), and the cables to connect these external elements to the recorder box. The objectives of this report are: 1. to describe the new 5-day-recorder seismic system in terms of its constituent parts and their functions, 2. to describe modifications to parts of the original system that were retained and to document new or replacement components with appropriate circuit diagrams and constructional details, 3. to provide detailed instructions for the correct adjustment or alignment of the system in the laboratory, and 4. to provide detailed instructions for installing and operating the system in the field.

Open-File Report↗
USGS2020

Measuring basal force fluctuations of debris flows using seismic recordings and empirical green's functions

We present a novel method for measuring the fluctuating basal normal and shear stresses of debris flows by using along‐channel seismic recordings. Our method couples a simple parameterization of a debris flow as a seismic source with direct measurements of seismic path effects using empirical Green's functions generated with a force hammer. We test this method using two large‐scale (8 and 10 m 3 ) experimental flows at the U.S. Geological Survey debris‐flow flume that were recorded by dozens of three‐component seismic sensors. The seismically derived basal stress fluctuations compare well in amplitude and timing to independent force plate measurements within the valid frequency range (15–50 Hz). We show that although the high‐frequency seismic signals provide band‐limited forcing information, there are systematic relations between the fluctuating stresses and independently measured flow properties, especially mean basal shear stress and flow thickness. However, none of the relationships are simple, and since the flow properties also correlate with one another, we cannot isolate a single factor that relates in a simple way to the fluctuating forces. Nevertheless, our observations, most notably the gradually declining ratio of fluctuating to mean basal stresses during flow passage and the distinctive behavior of the coarse, unsaturated flow front, imply that flow style may be a primary control on the conversion of translational to vibrational kinetic energy. This conversion ultimately controls the radiation of high‐frequency seismic waves. Thus, flow style may provide the key to revealing the nature of the relationship between fluctuating forces and other flow properties.

Journal of Geophysical Research Earth Surface↗
USGS1992

Recorded seismic response of Pacific Park Plaza. II. System identification

This is the second of two companion papers on the recorded seismic response of the Pacific Park Plaza building, in Emeryville, Calif., during the October 17, 1989, Ms = 7.1 (surface-wave magnitude) Loma Prieta earthquake. In this second part, the recorded data are analyzed in more detail by using system-identification techniques. The three-dimensional behavior and the coupled modes of the building are determined, and the effects of soil-structure interaction are investigated. The study shows that the response of the building is nonlinear at the beginning, and becomes linear after 17 sec into the earthquake. The dominant motion of the building follows an elliptical path oriented in the southeast-northwest direction. Some of the modes are complex, with nonproportional damping, and there are phase differences among modal response components. The fundamental mode of the building is a translation in the southeast-northwest direction at 0.4 Hz, with 13% damping. The wing displacements relative to the center core are large, about 50% of the center core displacements, and indicate significant torsion in the center core. The soil-structure interaction is characterized by a vibration at 0.7 Hz. This is believed to be the fundamental frequency of the surrounding soil medium. The rocking motions of the building are negligible.

Journal of Structural Engineering↗
USGS1962

Digital processing of array seismic recordings

This technical letter contains a brief review of the operations which are involved in digital processing of array seismic recordings by the methods of velocity filtering, summation, cross-multiplication and integration, and by combinations of these operations (the "UK Method" and multiple correlation). Examples are presented of analyses by the several techniques on array recordings which were obtained by the U.S. Geological Survey during chemical and nuclear explosions in the western United States. Seismograms are synthesized using actual noise and P n -signal recordings, such that the signal-to-noise ratio, onset time and velocity of the signal are predetermined for the synthetic record. These records are then analyzed by summation, cross-multiplication, multiple correlation and the UK technique, and the results are compared. For all of the examples presented, analysis by the non-linear techniques of multiple correlation and cross-multiplication of the traces on an array recording are preferred to analyses by the linear operations involved in summation and the UK Method.

Crustal Studies Technical Letter↗
USGS1977

Catalog of seismic records obtained in support of the ERDA/Nevada Operations Office, October 1963 through June 1976

The United States Geological Survey (USGS), Branch of Earthquake Hazards (BEH), Las Vegas, Nevada has provided ERDA, Nevada Operations Office, with seismic monitoring support to the underground nuclear weapons test program conducted at the Nevada Test Site (NTS) since September 1961. Activities from September 15, 1961 to September 13, 1963 are summarized in the report, "Seismic Dats Summary Nuclear Detonation Program, 1961 thru 1963", (Mickey and Shugart 1964) which lists seismic records obtained from all announced underground nuclear tests conducted during that period.

Nevada↗
USGS2009

Finding Trapped Miners by Using a Prototype Seismic Recording System Made from Music-Recording Hardware

The goal of this project was to use off-the-shelf music recording equipment to build and test a prototype seismic system to listen for people trapped in underground chambers (mines, caves, collapsed buildings). Previous workers found that an array of geophones is effective in locating trapped miners; displaying the data graphically, as well as playing it back into an audio device (headphones) at high speeds, was found to be effective for locating underground tapping. The desired system should record the data digitally to allow for further analysis, be capable of displaying the data graphically, allow for rudimentary analysis (bandpass filter, deconvolution), and allow the user to listen to the data at varying speeds. Although existing seismic reflection systems are adequate to record, display and analyze the data, they are relatively expensive and difficult to use and do not have an audio playback option. This makes it difficult for individual mines to have a system waiting on the shelf for an emergency. In contrast, music recording systems, like the one I used to construct the prototype system, can be purchased for about 20 percent of the cost of a seismic reflection system and are designed to be much easier to use. The prototype system makes use of an ~$3,000, 16-channel music recording system made by Presonus, Inc., of Baton Rouge, Louisiana. Other manufacturers make competitive systems that would serve equally well. Connecting the geophones to the recording system required the only custom part of this system - a connector that takes the output from the geophone cable and breaks it into 16 microphone inputs to be connected to the music recording system. The connector took about 1 day of technician time to build, using about $300 in off-the-shelf parts. Comparisons of the music recording system and a standard seismic reflection system (A 24-channel 'Geode' system manufactured by Geometrics, Inc., of San Jose, California) were carried out at two locations. Initial recordings of small hammer taps were carried out in a small field in Seattle, Washington; more elaborate tests were carried out at the San Juan Coal Mine in San Juan, New Mexico, in which miners underground were signaling. The comparisons demonstrate that the recordings made by the two systems are nearly identical, indicating that either system adequately records the data from the geophones. In either system the data can quickly be converted to a format (Society of Exploration Geophysicists 'Y' format; 'SEGY') to allow for filtering and other signal processing. With a modest software development effort, it is clear that either system could produce equivalent data products (SEGY data and audio data) within a few minutes of finishing the recording. The two systems both have significant advantages and drawbacks. With the seismograph, the tapping was distinctly visible when it occurred during a time window that was displayed. I have not identified or developed software for converting the resulting data to sound recordings that can be heard, but this limitation could be overcome with a trivial software development effort. The main drawbacks to the seismograph are that it does not allow for real-time listening, it is expensive to purchase, and it contains many features that are not utilized for this application. The music recording system is simple to use (it is designed for a general user, rather than a trained technician), allows for listening during recording, and has the advantage of using inexpensive, off-the-shelf components. It also allows for quick (within minutes) playback of the audio data at varying speeds. The data display by the software in the prototype system, however, is clearly inferior to the display on the seismograph. The music system also has the drawback of substantially oversampling the data by a factor of 24 (48,000 samples per second versus 2,000 samples per second) because the user interface only allows limited subsampling. This latte

Open-File Report↗
USGS2003

Wide-angle seismic recording from the 2002 Georgia Basin Geohazards Initiative, northwestern Washington and British Columbia

This report describes the acquisition and processing of shallow-crustal wide-angle seismicreflection and refraction data obtained during a collaborative study in the Georgia Strait, western Washington and southwestern British Columbia. The study, the 2002 Georgia Strait Geohazards Initiative, was conducted in May 2002 by the Pacific Geoscience Centre, the U.S. Geological Survey, and the University of Victoria. The wide-angle recordings were designed to image shallow crustal faults and Cenozoic sedimentary basins crossing the International Border in southern Georgia basin and to add to existing wide-angle recordings there made during the 1998 SHIPS experiment. We recorded, at wide-angle, 800 km of shallow penetration multichannel seismic-reflection profiles acquired by the Canadian Coast Guard Ship (CCGS) Tully using an air gun with a volume of 1.967 liters (120 cu. in.). Prior to this reflection survey, we deployed 48 Refteks onshore to record the airgun signals at wide offsets. Three components of an oriented, 4.5 Hz seismometer were digitally recorded at all stations. Nearly 160,300 individual air gun shots were recorded along 180 short seismic reflection lines. In this report, we illustrate the wide-angle profiles acquired using the CCGS Tully, describe the land recording of the air gun signals, and summarize the processing of the land recorder data into common-receiver gathers. We also describe the format and content of the archival tapes containing the SEGY-formated, common-receiver gathers for the Reftek data. Data quality is variable but the experiment provided useful data from 42 of the 48 stations deployed. Three-fourths of all stations yielded useful first-arrivals to source-receiver offsets beyond 10 km: the average maximum source-receiver offset for first arrivals was 17 km. Six stations yielded no useful data and useful firstarrivals were limited to offsets less than 10 km at five stations. We separately archived our recordings of 86 local and regional earthquakes ranging in magnitude from 0.2 to 4.3 and 16 teleseisms ranging in magnitude 5.5 to 6.5.

British Columbia;Washington↗
USGS1995

Data report for onshore-offshore wide-angle seismic recordings in the Bering-Chukchi Sea, Western Alaska and eastern Siberia

This report presents fourteen deep-crustal wide-angle seismic reflection and refraction profiles recorded onland in western Alaska and eastern Siberia from marine air gun sources in the Bering-Chukchi Seas. During a 20-day period in August, 1994, the R/V Ewing acquired two long (a total of 3754 km) deep-crustal seismic-reflection profiles on the continental shelf of the Bering and Chukchi Seas, in a collaborative project between Stanford University and the United States Geological Survey (USGS). The Ewing's 137.7 liter (8355 cu. in.) air gun array was the source for both the multichannel reflection and the wide-angle seismic data. The Ewing, operated by the Lamont-Doherty Earth Observatory, steamed northward from Nunivak Island to Barrow, and returned, firing the air gun array at intervals of either 50 m or 75 m. About 37,700 air gun shots were fired along the northward directed Lines 1 and 2, and more than 40,000 air gun shots were fired along the southward directed Line 3. The USGS and the University of Alaska, Fairbanks (UAF), deployed an array of twelve 3-component REFTEK and PDAS recorders in western Alaska and eastern Siberia which continuously recorded the air gun signals fired during the northward bound Lines 1 and 2. Seven of these recorders also continuously recorded the southward bound Line 3. These wide-angle seismic data were acquired to: (1) image reflectors in the upper to lower crust, (2) determine crustal and upper mantle refraction velocities, and (3) provide important constraints on the geometry of the Moho along the seismic lines. In this report, we describe the land recording of wide-angle data conducted by the USGS and the UAF, describe in detail how the wide-angle REFTEK and PDAS data were reduced to common receiver gather seismic sections, and illustrate the wide-angle seismic data obtained by the REFTEKs and PDAS's. Air gun signals were observed to ranges in excess of 400 km, and crustal and upper /mantle refractions indicate substantial variation in the crustal thickness along the transect.

Alaska↗
USGS1989

Recorded seismic response of a base-isolated steel bridge carrying a steel water pipe

A set of strong motion records was obtained from the base-isolated Santa Ana River Pipeline Bridge during the magnitude 5.9 Whittier Narrows, California, earthquake of October 1, 1987. The analysis of the records show that the level of excitation was not strong enough to fully activate the base isolators. The dominant modes of the response are the translations of the abutment-bridge-pipe system in the longitudinal and transverse directions, and the bending of the steel truss between supports in the vertical direction.

Conference Paper↗
USGS2012

Teleseismically recorded seismicity before and after the May 7, 1986, Andreanof Islands, Alaska, earthquake

The May 7, 1986, Andreanof Islands earthquake ( M w 8.0) is the largest event to have occurred in that section of the Aleutian arc since the March 9, 1957, Aleutian Islands earthquake ( M w 8.6). Teleseismically well-recorded earthquakes in the region of the 1986 earthquake are relocated with a plate model and with careful attention to the focal depths. The data set is nearly complete for m b ≥4.7 between longitudes 172°W and 179°W for the period 1964 through April 1987 and provides a detailed description of the space-time history of moderate-size earthquakes in the region for that period. Additional insight is provided by source parameters which have been systematically determined for M w ≥5 earthquakes that occurred in the region since 1977 and by a modeling study of the spatial distribution of moment release on the mainshock fault plane. A technically significant component of oblique convergence in the central Aleutian arc results in its breakup into clockwiserotating and westward translating blocks. The western part of the Andreanof block is distinct from and stronger than flanking regions. The greater strength of this block segment and strong coupling along the main thrust zone result in the accumulation of high levels of shear stress, which give rise to great earthquakes near its eastern boundary. The occurrence of the 1986 rupture only 29 years after the 1957 earthquake may indicate that in the central Aleutians M 7+ earthquakes ordinarily do represent the predominant mode of strain release. Segmentation of the main thrust zone into upper and lower planes is supported by spatial and temporal patterns of seismicity and by focal mechanism data. This and other lines of evidence indicate a downdip increase in fault strength and possibly in heterogeneity within the main thrust zone in subduction zone environments. Aftershocks of the 1986 earthquake were bounded to the west by the Andreanof block boundary (Adak Canyon) and to the east by an aseismic segment of the main thrust zone near the subducted extension of the Amlia fracture zone. The aftershock distribution was bounded to the south by a forearc shear zone and to the north by the base of the main thrust zone in the Hawley Ridge segment and by the downdip edge of the upper plane of the main thrust zone in the eastern segment. Aftershocks which occurred near the volcanic line at shallow crustal depths in the upper plate were triggered by the mainshock and manifest a partial decoupling of oblique slip in this region along a west-striking right-lateral fault with low shear strength. Aftershock clustering along the main thrust zone was very similar to the distribution of prior seismicity, suggesting a continuation of long-term processes and the existence of areas with distinct mechanical properties. Interconnecting regions of low seismicity during both the premainshock and aftershock periods coincided with areas of major moment release during the mainshock. Seismicity data prior to the 1986 mainshock gave few clues about the location of the mainshock nucleation point, the mainshock size, and its time of occurrence. However, a large part of the mainshock moment release did coincide with a zone of seismic quiescence monitored by the Adak local seismograph network.

Journal of Geophysical Research Solid Earth↗
USGS2019

Site response in the Oklahoma region from seismic recordings of the 2011 Mw 5.7 Prague earthquake

We invert the shear-wave displacement spectra obtained from 30 three-component, broadband waveforms recorded within 300 km of the 6 November 2011 Mw 5.7 Prague, Oklahoma earthquake to recover the site-response contribution using an inversion method that simultaneously inverts for source, path, and site effects. Site-response functions identify resonant frequencies within a range of 0.1-10 Hz that generally coincide with spectral peaks in H/V curves derived from the recorded waveforms. S-wave velocity profiles available for several sites were also used to calculate theoretical SH transfer functions that predict the site amplification due to the near-surface soil structure down to depths of 30-50 m. These transfer functions are generally flat below about 8 Hz in the frequency range sampled by the spectral inversion process, indicating that the spectral peaks in the site response obtained from the waveform analysis result from deeper velocity variations. A 0.3-Hz spectral peak observed at several stations, for example, coincides with the strong, surface-wave amplitudes observed at 3s periods for induced M ≥ 3 earthquakes in Oklahoma and Kansas, suggesting that this resonant peak may be due to surface waves trapped in the upper sedimentary layer of the crust. Both shallow and deep contributions to the site response are important for the characterization of ground motion from Central and Eastern North America (CENA) earthquakes. We obtain a seismic moment of 4.32 × 1024 dyne-cm and a corner frequency of 0.229, consistent with the magnitude of the event. A frequency-dependent attenuation relation of Q(f)=1107f 0.398 consistent with prior measurements of path properties in CENA is also derived.

Oklahoma↗
USGS2012

Data quality of seismic records from the Tohoku, Japan earthquake as recorded across the Albuquerque Seismological Laboratory networks

Great earthquakes recorded across modern digital seismographic networks, such as the recent Tohoku, Japan, earthquake on 11 March 2011 (M w = 9.0), provide unique datasets that ultimately lead to a better understanding of the Earth's structure (e.g., Pesicek et al. 2008) and earthquake sources (e.g., Ammon et al. 2011). For network operators, such events provide the opportunity to look at the performance across their entire network using a single event, as the ground motion records from the event will be well above every station's noise floor.

Seismological Research Letters↗