Search USGS⌕ Search

SEARCH · Search USGS

Results for “The Seismic Record”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 883 records · Page 49Linked to original sources
USGS2023

Uncertainties in intensity-based earthquake magnitude estimates

Estimating the magnitude of historical earthquakes is crucial for assessing seismic hazard. Magnitudes of early‐instrumental earthquakes can be inferred using a combination of instrumental records, field observations, and the observed distribution of shaking intensity determined from macroseismic observations. For earthquakes before 1900, shaking intensity distributions often provide the only information to constrain earthquake magnitude. Considerable effort has been made to develop methods to estimate the magnitude of moderate‐to‐large historical earthquakes using shaking intensities derived from macroseismic data. In this study, we consider earthquakes in California with known instrumental magnitudes to explore uncertainties in estimating the magnitude of historical earthquakes from intensity information alone. We use three California‐specific intensity prediction equations (IPEs) and an IPE based on a global ground‐motion model (GMM) to determine optimum intensity‐based magnitudes for 33 moderate‐to‐large California earthquakes between 1979 and 2021. Intensity‐based magnitudes are close to instrumental magnitudes on average. However, intensity‐based magnitudes for individual events differ by as much as 2.2 magnitude units from instrumental magnitudes. This result reflects the weak dependence of ground motions and shaking intensities on moment magnitude and their strong dependence on stress drop. Considering the intensity distributions of the 1906 San Francisco and 1989 Loma Prieta earthquakes, we show that information that could constrain rupture length is discarded when considering only the 2D decay of intensity with distance. We also show that ground‐motion intensity conversion equations used in a GMM‐based approach may cause a systematic overestimation of large historical earthquake magnitudes. This study underscores both the reducible and potentially irreducible uncertainties associated with using intensity data to estimate magnitudes of historical earthquakes using IPEs and highlights the value of using additional information to constrain rupture dimensions. Using intensity observations alone, moment magnitude uncertainties are typically on the order of a full unit.

California↗
USGS2006

Earthquakes in Virginia and vicinity 1774 - 2004

This map summarizes two and a third centuries of earthquake activity. The seismic history consists of letters, journals, diaries, and newspaper and scholarly articles that supplement seismograph recordings (seismograms) dating from the early twentieth century to the present. All of the pre-instrumental (historical) earthquakes were large enough to be felt by people or to cause shaking damage to buildings and their contents. Later, widespread use of seismographs meant that tremors too small or distant to be felt could be detected and accurately located. Earthquakes are a legitimate concern in Virginia and parts of adjacent States. Moderate earthquakes cause slight local damage somewhere in the map area about twice a decade on the average. Additionally, many buildings in the map area were constructed before earthquake protection was added to local building codes. The large map shows all historical and instrumentally located earthquakes from 1774 through 2004.

Virginia↗
USGS2009

High-Resolution Geologic Mapping of the Inner Continental Shelf: Cape Ann to Salisbury Beach, Massachusetts

The geologic framework of the Massachusetts inner continental shelf between Cape Ann and Salisbury Beach has been shaped by a complicated history of glaciation, deglaciation, and changes in relative sea level. New geophysical data (swath bathymetry, sidescan sonar and seismic-reflection profiling), sediment samples, and seafloor photography provide insight into the geomorphic and stratigraphic record generated by these processes. High-resolution spatial data and geologic maps in this report support coastal research and efforts to understand the type, distribution, and quality of subtidal marine habitats in the Massachusetts coastal ocean.

Open-File Report↗
USGS2008

Earthquakes in Ohio and Vicinity 1776-2007

This map summarizes two and a third centuries of earthquake activity. The seismic history consists of letters, journals, diaries, and newspaper and scholarly articles that supplement seismograph recordings (seismograms) dating from the early twentieth century to the present. All of the pre-instrumental (historical) earthquakes were large enough to be felt by people or to cause shaking damage to buildings and their contents. Later, widespread use of seismographs meant that tremors too small or distant to be felt could be detected and accurately located. Earthquakes are a legitimate concern in Ohio and parts of adjacent States. Ohio has experienced more than 160 felt earthquakes since 1776. Most of these events caused no damage or injuries. However, 15 Ohio earthquakes resulted in property damage and some minor injuries. The largest historic earthquake in the state occurred in 1937. This event had an estimated magnitude of 5.4 and caused considerable damage in the town of Anna and in several other western Ohio communities. The large map shows all historical and instrumentally located earthquakes from 1776 through 2007.

Open-File Report↗
USGS1978

South Carolina seismic program seismological data report, July 1975-June 1977

The purpose of this data report is to collect and distribute preliminary data acquired from a network of seismic stations (Tarr and King, 1974) in order to facilitate current studies of earthquake occurrence. Record interpretation, data processing, and collation of hypocenter data and related-event parameters are performed by the U.S. Geological Survey, Golden, Colorado. This compilation is preliminary and is subject to later revisions on the basis of current research.

South Carolina↗
USGS1980

Seismic-reflection data on the eastern U.S. continental shelf acquired by M. V. L'OLONNOIS as part of the Atlantic Margin Coring Project (AMCOR) of the U.S. Geological Survey, July-September 1976

In 1976 the U.S. Geological Survey undertook a program to sample the eastern United States Shelf for stratigraphic information by drilling a set of core holes. Results of this Atlantic Margin Coring Program (AMCOR) have been reported by Hathaway and others. Sites were chosen from seismic-reflection data and were reviewed by a safety panel to minimize the risk of penetrating any hydrocarbon accumulation which might lead to environmental contamination. The M-V-L'OLONNOIS, the service ship for the drilling operation, was fitted with seismic-reflection profiling equipment (listed below), to run seismic-reflection profiles before drilling began on each hole. This provided additional assurance that no closed structures would be penetrated and allowed minor adjustment with the site selection. A total of 491 km of high-resolution seismic profiles was collected on 22 sites. Equipment used (specifics for each site noted on records): Bolt Air Guns 1-40 cubic inch chambers EPC Recorder Teledyne Minisparker (last two sites) Navigation used two Internav 101 Loran-C receivers.

Open-File Report↗
USGS2017

Shallow repeating seismic events under an alpine glacier at Mount Rainier, Washington, USA

We observed several swarms of repeating low-frequency (1–5 Hz) seismic events during a 3 week period in May–June 2010, near the summit of Mount Rainier, Washington, USA, that likely were a result of stick–slip motion at the base of alpine glaciers. The dominant set of repeating events ('multiplets') featured >4000 individual events and did not exhibit daytime variations in recurrence interval or amplitude. Volcanoes and glaciers around the world are known to produce seismic signals with great variability in both frequency content and size. The low-frequency character and periodic recurrence of the Mount Rainier multiplets mimic long-period seismicity often seen at volcanoes, particularly during periods of unrest. However, their near-surface location, lack of common spectral peaks across the recording network, rapid attenuation of amplitudes with distance, and temporal correlation with weather systems all indicate that ice-related source mechanisms are the most likely explanation. We interpret the low-frequency character of these multiplets to be the result of trapping of seismic energy under glacial ice as it propagates through the highly heterogeneous and attenuating volcanic material. The Mount Rainier multiplet sequences underscore the difficulties in differentiating low-frequency signals due to glacial processes from those caused by volcanic processes on glacier-clad volcanoes.

Washington↗
USGS1982

GLORIA sidescan and seismic data collected by the DESV STARELLA along the continental slope and upper continental rise of the Eastern United States in 1979

A cruise on the- DESV STARELLA was conducted between October 23. 1979, and November 8, 1979, by the U.S. Geologic.al Survey (USGS) in cooperation with the United Kingdom's Institute of Oceanographic Sciences (IOS). The purpose of the study was to gain an overview of the morphology of large areas of the Continental Slope and upper Continental Rise off the eastern ·united States. Sidescan-sonar and single-channel seismic-reflection data were collected along the tracklines. The ship's position. was monitored using LORAN_C and satellite navigation techniques. The sidescan data were collected using the !OS-developed Geologic Long­-Range Inclined Asdic, Mark II (GLORIA II) system. GLORIA was operated at either a 20-second or 40-second sweep, giving maximum slant-range distances of 15 or 30 kilometers, respectively, to each side of the towed fish. The sidescan data were collected on graphic recorders and analog tapes. The tapes were played onto photographic paper in a facsimile machine; then these prints were photographically stretched to produce approximately isometric images .. The images were not corrected for slant-range distortion. Mosaics at a scale of 1:250,000 (Mercator projection) were made from the photographic images. The seismic· data consist of 40-in 3 airgun and 10-kHz echo-sounder profiles. The airgun data were recorded on EPC recorders at both 8- and 4- second sweep rates. The 10-kHz echo-sounder data were recorded on a wet-paper recorder at a 2-second sweep rate. Approximately 4,820 km of seismic and sonar-data wera collected from four areas of interest and along the lines connecting those areas. Area 1 includes the Continental Slope and upper Rise seaward of Georges Bank, between Northeast Channel and Alvin Canyon. Numerous lines were run here, resulting in approximately 2,500 km of seismic data and complete and overlapping GLORIA coverage of the area. A similar survey, consisting of approximately 1 2 200 km of trackline, was run in area 2, which includes the Continental Slope and upper Rise seaward of the middle Atlantic states between Hudson Canyon and Baltimore Canyon. A single line, 250 km long, was run through area 3 along the base of the Continental Slope from Cape Hatteras to latitude 33°N. off North and South Carolina. Two parallel lines, totaling 870 km, were run through area 4 along the Blake Escarpment, from the Blake Spur south to latitude 27°40'N. One line was run along the top of the escarpment and the other was run along the base of the escarpment. All the data can be studied at the U.S. Geological Survey offices in Woods Hole, MA 02543. Microfilm copies of the sidescan-monitor record as well as the airgun and 10-kHz profiles can be purchased only from the National Geophysical Data Center, NOAA, Code E64, 325 Broadway, Boulder, CO 80303 (303/497-6338). Photographic copies of the GLORIA mosaics can also be obtained only from this address.

Open-File Report↗
USGS1997

One minute after: Strong-motion map, effective epicenter, and effective magnitude

This article reports the recent progress on real-time seismic monitoring in Taiwan, particularly the real-time strong-motion monitoring by the Taiwan Central Weather Bureau's telemetered seismic network ( CWBSN ), which is presently aiming at rapid reporting immediately after a large earthquake occurrence. If rapid reporting can be achieved before the arrival of the strong shaking, earthquake early warning will become possible. CWBSN has achieved the generation of the intensity map, epicenter, and magnitude within 1 min of the occurrence of a large earthquake. Both rapid reporting and early warning are principally applied to large ( M ≫ 5) events; the requirement of on-scale waveform recording prompted CWBSN in 1995 to integrate strong-motion sensors (e.g., force-balance accelerometers) into its telemetered seismic monitoring system. Time-domain recursive processing is applied to the multi-channel incoming seismic signals by a group of networked personal computers to generate the intensity map. From the isoseismal contours, an effective epicenter is immediately identified that resides in the middle of the largest (usually the 100-gal) contour curve of the intensity map. An effective magnitude is also defined that can be derived immediately from the surface area covered by the largest (usually the 100-gal) contour curve. For a large event with a finite rupture surface, the epicenter and magnitude so derived are more adequate estimates of the source location and of the strength of destruction. The effective epicenter gives the center of the damage area; it stands in contrast with the conventional epicenter location, which only gives the initial point of rupture nucleation. The effective magnitude reflects more closely the earthquake damage potential, instead of the classical magnitude definition that emphasizes the total energy release. The CWBSN has achieved in obtaining the above crucial source information well within 1 min. This time can further be reduced to better than 30 sec, as illustrated by the example in this article, showing that earthquake early warning is indeed an achievable goal. The rapid reporting and early warning information is electronically transmitted to users to allow rapid response actions, with or without further human intervention.

Bulletin of the Seismological Society of America↗
USGS1993

Seismic response of eccentrically braced tall buildings

Spectral analysis and system identification techniques are used to analyze a set of acceleration reponse records obtained during the Loma Prieta earthquake from the 47-story, moment-resisting framed and eccentrically braced Embarcadero Building (EMB). The EMB was constructed in 1979 based on the 1976 Uniform Building Code requirements and a design response spectra defined by two levels of earthquake performances. The EMB is in the lower market area of San Francisco, which is of great interest to the engineering community because of the area's soft soil characteristics that amplify ground motions originating at long distances, and because the Embarcadero freeway suffered extensive damage during the earthquake and was razed in 1991. The first modal frequencies of the building at approximately 0.19 Hz (north-south) and 0.16 Hz (east-west) are identified. The torsional response and rocking motions of the building are insignificant. Discontinuity of stiffness and mass at the 40th floor level causes significant response issues above that floor such as excessive drift ratios.

Journal of Structural Engineering↗
USGS2021

Shear-wave velocity site characterization in Oklahoma from joint inversion of multi-method surface seismic measurements: Implications for central U.S. Ground Motion Prediction

We analyze multimethod shear (SH)‐wave velocity ( ⁠ V S "> V S ) site characterization data acquired at three permanent and 25 temporary seismograph stations in Oklahoma that recorded M 4+ earthquakes within a 50 km hypocentral distance of at least one of the 2016 M 5.1 Fairview, M 5.8 Pawnee, or M 5.0 Cushing earthquakes to better constrain earthquake ground‐motion modeling in the region. We acquired active‐source seismic data for time‐averaged V S "> V S to 30 m depth ( V S "> V S V S 30 "> 30 ) at 28 seismograph stations near the Fairview, Pawnee, and Cushing epicentral areas. The SH‐wave refraction travel times coupled with Rayleigh‐ and Love‐wave phase velocity dispersion were extracted and modeled in a nonlinear least‐squares (L2) joint inversion to obtain a best‐fit 1D V S "> V S versus depth profile for each site. At a subset of sites where the preferred L2 inverse model did not optimally fit each of the Love, Rayleigh, and SH travel‐time datasets, we explore application of simulated annealing in a joint inversion to find a more global solution. V S "> V S V S 30 "> 30 values range from 262 to 807    m / s "> 807 m / s for the preferred measured (in situ) V S "> V S profiles, or National Earthquake Hazards Reduction Program (NEHRP) site class D to B, and are broadly comparable with estimates from previous data reports in the region. Site amplification estimates were calculated next from 1D SH transfer functions of the preferred V S "> V S VS profiles and then compared against observed horizontal‐to‐vertical spectral ratios (HVSRs) from nearby seismograph stations. We generally see good agreement between the predicted in situ model and the observed HVSR resonant frequencies, with nominal amplifications between 2 and 10 within the 2–15 Hz frequency band. Next, using 40 known in situ V S "> V S V S 30 "> 30 measurements in the region, we demonstrate that the in situ V S "> V S V S 30 "> 30 values improve the fit for selected suites of ground‐motion models (GMMs) for M 4+ earthquakes within a 50 km hypocentral distance when compared with proxy methods, arguing for future development of GMMs implementing in situ V S "> V S profiles.

Oklahoma↗
USGS2019

Comparison of site dominant frequency from earthquake and microseismic data in California

An important predictive variable for site amplification is the site dominant frequency ( ⁠ƒ d ⁠ ). At seismic monitoring stations, ƒ d can be calculated from the peak of the horizontal‐to‐vertical spectral ratios (HVSRs) obtained from earthquake recordings (eHVSR). For other sites, ƒ d can be estimated from microseismic (mHVSR) observations. We compare the ƒ d values derived from eHVSR (5% damped response spectra from the Next Generation Attenuation‐West2 [NGA‐West2] database; Ancheta et al. , 2014 ) with those derived from mHVSR (Fourier spectra from Yong et al. , 2013 ) for seismic stations in California. We show that the logarithm of eHVSR ƒ d scales linearly with the logarithm of mHVSR ƒ d ⁠ , with a standard deviation of 0.14log 10 units for mHVSR ƒ d larger than 0.2 Hz. The relationship holds for microseismic surveys at distances up to 300 m away from the seismic stations. The results of this study have beneficial implications for the characterization of site response in modern ground‐motion models as well as in building codes.

California↗
USGS1977

Evaluating the intensity of U.S. earthquakes

The intensity scale based on the Modified Mercalli Scale of 1931 (MM scale) measures the effects of seismic shaking. Intensity estimations are often the only representation of the size of an earthquake when small shocks occur in areas far removed from seismograph stations that can record them instrumentally. The impossibility of setting up and maintaining instruments to measure ground motion everywhere that earthquakes occur makes the intensity scale a necessary and useful method to estimate earthquake effects. The effects of seismic shaking are objective. All observers can agree these are real occurences and not subjective speculation. Reliable intensity evaluations are based not on a single factor on any scale but on consistent combinations.

Earthquake Information Bulletin (USGS)↗
USGS2011

Moment tensor inversions using strong motion waveforms of Taiwan TSMIP data, 1993–2009

Earthquake source parameters are important for earthquake studies and seismic hazard assessment. Moment tensors are among the most important earthquake source parameters, and are now routinely derived using modern broadband seismic networks around the world. Similar waveform inversion techniques can also apply to other available data, including strong-motion seismograms. Strong-motion waveforms are also broadband, and recorded in many regions since the 1980s. Thus, strong-motion data can be used to augment moment tensor catalogs with a much larger dataset than that available from the high-gain, broadband seismic networks. However, a systematic comparison between the moment tensors derived from strong motion waveforms and high-gain broadband waveforms has not been available. In this study, we inverted the source mechanisms of Taiwan earthquakes between 1993 and 2009 by using the regional moment tensor inversion method using digital data from several hundred stations in the Taiwan Strong Motion Instrumentation Program (TSMIP). By testing different velocity models and filter passbands, we were able to successfully derive moment tensor solutions for 107 earthquakes of M w >= 4.8. The solutions for large events agree well with other available moment tensor catalogs derived from local and global broadband networks. However, for M w = 5.0 or smaller events, we consistently over estimated the moment magnitudes by 0.5 to 1.0. We have tested accelerograms, and velocity waveforms integrated from accelerograms for the inversions, and found the results are similar. In addition, we used part of the catalogs to study important seismogenic structures in the area near Meishan Taiwan which was the site of a very damaging earthquake a century ago, and found that the structures were dominated by events with complex right-lateral strike-slip faulting during the recent decade. The procedures developed from this study may be applied to other strong-motion datasets to compliment or fill gaps in catalogs from regional broadband networks and teleseismic networks.

Tectonophysics↗
USGS2011

Imaging using cross-hole seismoelectric tomography

We propose a new cross-hole imaging approach based on seismoelectric conversions associated with the transmission of seismic waves from seismic sources located in a borehole to receivers electrodes located in a second borehole. The seismoelectric seismic-to-electric problem is solved using Biot theory coupled with a generalized Ohm's law with an electrokinetic coupling term. The components of the displacement of the solid phase, the fluid pressure, and the electrical potential are solved using a finite element approach with PML boundary conditions for the seismic waves and boundary conditions mimicking an infinite material for the electrostatic problem. We have developed an inversion algorithm using the electrical disturbances recorded in the second borehole to localize the position of the heterogeneities responsible for the seismoelectric conversions. Because of the ill-posed nature of the inverse problem, regularization is used to constrain the solution at each time in the seismoelectric time window comprised between the time of the seismic shot and the time of the first arrival of the seismic waves in the second borehole. All the inverted volumetric current source densities are stacked to produce an image of the position of the heterogeneities between the two boreholes. Two simple synthetic case studies are presented to test this concept. The first case study corresponds to a vertical discontinuity between two homogeneous sub-domains. The second case study corresponds to a poroelastic inclusion embedded into an homogenous poroelastic formation. In both cases, the position of the heterogeneity is fairly well-recovered using only the electrical disturbances associated with the seismoelectric conversions. ?? 2011 Society of Exploration Geophysicists.

SEG Technical Program Expanded Abstracts↗
USGS2024

New developments at the Center for Engineering Strong-Motion Data (CESMD)

The Center for Engineering Strong-Motion Data (CESMD), an internationally utilized joint center of the U.S. Geological Survey (USGS) and the California Geological Survey (CGS), provides a single access point for earthquake strong-motion records and station metadata from the CGS California Strong-Motion Instrumentation Program (CSMIP), the USGS National Strong-Motion Project (NSMP), the USGS Advanced National Seismic System, and other affiliates. The CESMD has been continuously improving its webtools to facilitate the access of strong-motion data and metadata for use in post-earthquake response and for scientific and engineering research applications. The Center provides raw and processed strong-motion data via the Engineering Data Center (EDC) and the Virtual Data Center (VDC) web portals. This paper focuses on the strong-motion products provided by the EDC where more than 48,000 records with peak ground accelerations greater than 0.1% g from over 2400 earthquakes are currently hosted. and on the ongoing efforts to develop data access tools and applications. The new developments and ongoing efforts in the EDC include: 1) enhancements to the CESMD webservices to facilitate access to station metadata, earthquake information, and strong motion records 2) new features to the interactive map interface, improving the visualization and access to earthquake, station, and record information, 3) efforts to develop a new web application tool for data format conversion from a number of data formats, 4) efforts to unify varying waveform data formats into a consistent format, 5) ongoing efforts to compile seismic station site geology, measured or inferred Vs30 values, shear-wave profiles, NEHRP site class, and available structural instrument deployment schematics, and 6) a special studies pages for research topic-specific ground motion datasets that offer uniform processing of records from a variety of sources.

Conference Paper↗
USGS1969

Seismic activity in the Sunnyside mining district, Utah, during 1967

A seismic monitoring network near Sunnyside, Utah, consisting of a triangular array of seismometer stations that encompasses most of the mine workings in the district, recorded over 50,000 local earth tremors during 1967. About 540 of the tremors were of sufficient magnitude to be accurately located. Most of these were located within 2-3 miles of mine workings and were also near known or suspected faults. The district-wide seismic activity generally consisted of two different patterns--a periodic increase in the daily number of tremors at weekly intervals, and also a less regular and longer term increase and decrease of seismic activity that occurred over a period of weeks or even months. The shorter and more regular pattern can be correlated with the mine work week and seems to result from mining. The longer term activity, however, does not correlate with known mining causes sad therefore seems to be .caused by natural stresses.

Open-File Report↗
USGS2012

Imaging with cross-hole seismoelectric tomography

We propose a cross-hole imaging approach based on seismoelectric conversions (SC) associated with the transmission of seismic waves from seismic sources located in a borehole to receivers (electrodes) located in a second borehole. The seismoelectric (seismic-to-electric) problem is solved using Biot theory coupled with a generalized Ohm's law with an electrokinetic streaming current contribution. The components of the displacement of the solid phase, the fluid pressure, and the electrical potential are solved using a finite element approach with Perfect Match Layer (PML) boundary conditions for the seismic waves and boundary conditions mimicking an infinite material for the electrostatic problem. We develop an inversion algorithm using the electrical disturbances recorded in the second borehole to localize the position of the heterogeneities responsible for the SC. Because of the ill-posed nature of the inverse problem (inherent to all potential-field problems), regularization is used to constrain the solution at each time in the SC-time window comprised between the time of the seismic shot and the time of the first arrival of the seismic waves in the second borehole. All the inverted volumetric current source densities are aggregated together to produce an image of the position of the heterogeneities between the two boreholes. Two simple synthetic case studies are presented to test this concept. The first case study corresponds to a vertical discontinuity between two homogeneous sub-domains. The second case study corresponds to a poroelastic inclusion (partially saturated by oil) embedded into an homogenous poroelastic formation. In both cases, the position of the heterogeneity is recovered using only the electrical disturbances associated with the SC. That said, a joint inversion of the seismic and seismoelectric data could improve these results.

Geophysical Journal International↗