USGS Science⌕ Search

SEARCH · USGS Science

Results for “The Seismological 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 55 records · Page 3Linked to original sources
USGS1922

Hawaiian Volcano Observatory bulletins - 1922

The Hawaiian Volcano Observatory (HVO) Bulletin series was an informal publication issued between the years 1913 to 1929. Individual issues contain information on volcanic and earthquake activity, volcano research, and volcano monitoring in Hawaii, and issues often included photographs, sketches, and data plots. Information on volcanic activity at other locations is also occasionally included. The Bulletin series was published by HVO through the Hawaiian Volcano Research Association. Weekly Bulletins (initially called Reports) were issued between June 28, 1913, and July 1, 1914. Bulletins were issued monthly after July 1, 1914, though they were still named Weekly Bulletins until January 1919. Starting with the February 1919 issue, the Bulletins were named Monthly Bulletins, and they continued to be issued monthly until the series ceased in July 1929. During a single year, 1915, Seismometric Bulletins were also issued quarterly. These four issues contain summaries of seismic observations recorded by the then-nascent Whitney Laboratory of Seismology, located underground in a vault near the summit of Kīlauea. Two of the bulletins are misnumbered: • April 1916 volume IV no. 4 incorrectly says April 1915 volume III no. 4 • September 1916 volume IV no. 9 incorrectly says September 1916 volume VI no. 9

Hawaii↗
USGS1923

Hawaiian Volcano Observatory bulletins - 1923

The Hawaiian Volcano Observatory (HVO) Bulletin series was an informal publication issued between the years 1913 to 1929. Individual issues contain information on volcanic and earthquake activity, volcano research, and volcano monitoring in Hawaii, and issues often included photographs, sketches, and data plots. Information on volcanic activity at other locations is also occasionally included. The Bulletin series was published by HVO through the Hawaiian Volcano Research Association. Weekly Bulletins (initially called Reports) were issued between June 28, 1913, and July 1, 1914. Bulletins were issued monthly after July 1, 1914, though they were still named Weekly Bulletins until January 1919. Starting with the February 1919 issue, the Bulletins were named Monthly Bulletins, and they continued to be issued monthly until the series ceased in July 1929. During a single year, 1915, Seismometric Bulletins were also issued quarterly. These four issues contain summaries of seismic observations recorded by the then-nascent Whitney Laboratory of Seismology, located underground in a vault near the summit of Kīlauea. Two of the bulletins are misnumbered: • April 1916 volume IV no. 4 incorrectly says April 1915 volume III no. 4 • September 1916 volume IV no. 9 incorrectly says September 1916 volume VI no. 9

Hawaii↗
USGS1924

Hawaiian Volcano Observatory bulletins - 1924

The Hawaiian Volcano Observatory (HVO) Bulletin series was an informal publication issued between the years 1913 to 1929. Individual issues contain information on volcanic and earthquake activity, volcano research, and volcano monitoring in Hawaii, and issues often included photographs, sketches, and data plots. Information on volcanic activity at other locations is also occasionally included. The Bulletin series was published by HVO through the Hawaiian Volcano Research Association. Weekly Bulletins (initially called Reports) were issued between June 28, 1913, and July 1, 1914. Bulletins were issued monthly after July 1, 1914, though they were still named Weekly Bulletins until January 1919. Starting with the February 1919 issue, the Bulletins were named Monthly Bulletins, and they continued to be issued monthly until the series ceased in July 1929. During a single year, 1915, Seismometric Bulletins were also issued quarterly. These four issues contain summaries of seismic observations recorded by the then-nascent Whitney Laboratory of Seismology, located underground in a vault near the summit of Kīlauea. Two of the bulletins are misnumbered: • April 1916 volume IV no. 4 incorrectly says April 1915 volume III no. 4 • September 1916 volume IV no. 9 incorrectly says September 1916 volume VI no. 9

Hawaii↗
USGS1925

Hawaiian Volcano Observatory bulletins - 1925

The Hawaiian Volcano Observatory (HVO) Bulletin series was an informal publication issued between the years 1913 to 1929. Individual issues contain information on volcanic and earthquake activity, volcano research, and volcano monitoring in Hawaii, and issues often included photographs, sketches, and data plots. Information on volcanic activity at other locations is also occasionally included. The Bulletin series was published by HVO through the Hawaiian Volcano Research Association. Weekly Bulletins (initially called Reports) were issued between June 28, 1913, and July 1, 1914. Bulletins were issued monthly after July 1, 1914, though they were still named Weekly Bulletins until January 1919. Starting with the February 1919 issue, the Bulletins were named Monthly Bulletins, and they continued to be issued monthly until the series ceased in July 1929. During a single year, 1915, Seismometric Bulletins were also issued quarterly. These four issues contain summaries of seismic observations recorded by the then-nascent Whitney Laboratory of Seismology, located underground in a vault near the summit of Kīlauea. Two of the bulletins are misnumbered: • April 1916 volume IV no. 4 incorrectly says April 1915 volume III no. 4 • September 1916 volume IV no. 9 incorrectly says September 1916 volume VI no. 9

Hawaii↗
USGS1926

Hawaiian Volcano Observatory bulletins - 1926

The Hawaiian Volcano Observatory (HVO) Bulletin series was an informal publication issued between the years 1913 to 1929. Individual issues contain information on volcanic and earthquake activity, volcano research, and volcano monitoring in Hawaii, and issues often included photographs, sketches, and data plots. Information on volcanic activity at other locations is also occasionally included. The Bulletin series was published by HVO through the Hawaiian Volcano Research Association. Weekly Bulletins (initially called Reports) were issued between June 28, 1913, and July 1, 1914. Bulletins were issued monthly after July 1, 1914, though they were still named Weekly Bulletins until January 1919. Starting with the February 1919 issue, the Bulletins were named Monthly Bulletins, and they continued to be issued monthly until the series ceased in July 1929. During a single year, 1915, Seismometric Bulletins were also issued quarterly. These four issues contain summaries of seismic observations recorded by the then-nascent Whitney Laboratory of Seismology, located underground in a vault near the summit of Kīlauea. Two of the bulletins are misnumbered: • April 1916 volume IV no. 4 incorrectly says April 1915 volume III no. 4 • September 1916 volume IV no. 9 incorrectly says September 1916 volume VI no. 9

Hawaii↗
USGS1927

Hawaiian Volcano Observatory bulletins - 1927

The Hawaiian Volcano Observatory (HVO) Bulletin series was an informal publication issued between the years 1913 to 1929. Individual issues contain information on volcanic and earthquake activity, volcano research, and volcano monitoring in Hawaii, and issues often included photographs, sketches, and data plots. Information on volcanic activity at other locations is also occasionally included. The Bulletin series was published by HVO through the Hawaiian Volcano Research Association. Weekly Bulletins (initially called Reports) were issued between June 28, 1913, and July 1, 1914. Bulletins were issued monthly after July 1, 1914, though they were still named Weekly Bulletins until January 1919. Starting with the February 1919 issue, the Bulletins were named Monthly Bulletins, and they continued to be issued monthly until the series ceased in July 1929. During a single year, 1915, Seismometric Bulletins were also issued quarterly. These four issues contain summaries of seismic observations recorded by the then-nascent Whitney Laboratory of Seismology, located underground in a vault near the summit of Kīlauea. Two of the bulletins are misnumbered: • April 1916 volume IV no. 4 incorrectly says April 1915 volume III no. 4 • September 1916 volume IV no. 9 incorrectly says September 1916 volume VI no. 9

Hawaii↗
USGS1928

Hawaiian Volcano Observatory bulletins - 1928

The Hawaiian Volcano Observatory (HVO) Bulletin series was an informal publication issued between the years 1913 to 1929. Individual issues contain information on volcanic and earthquake activity, volcano research, and volcano monitoring in Hawaii, and issues often included photographs, sketches, and data plots. Information on volcanic activity at other locations is also occasionally included. The Bulletin series was published by HVO through the Hawaiian Volcano Research Association. Weekly Bulletins (initially called Reports) were issued between June 28, 1913, and July 1, 1914. Bulletins were issued monthly after July 1, 1914, though they were still named Weekly Bulletins until January 1919. Starting with the February 1919 issue, the Bulletins were named Monthly Bulletins, and they continued to be issued monthly until the series ceased in July 1929. During a single year, 1915, Seismometric Bulletins were also issued quarterly. These four issues contain summaries of seismic observations recorded by the then-nascent Whitney Laboratory of Seismology, located underground in a vault near the summit of Kīlauea. Two of the bulletins are misnumbered: • April 1916 volume IV no. 4 incorrectly says April 1915 volume III no. 4 • September 1916 volume IV no. 9 incorrectly says September 1916 volume VI no. 9

Hawaii↗
USGS1929

Hawaiian Volcano Observatory bulletins - 1929

The Hawaiian Volcano Observatory (HVO) Bulletin series was an informal publication issued between the years 1913 to 1929. Individual issues contain information on volcanic and earthquake activity, volcano research, and volcano monitoring in Hawaii, and issues often included photographs, sketches, and data plots. Information on volcanic activity at other locations is also occasionally included. The Bulletin series was published by HVO through the Hawaiian Volcano Research Association. Weekly Bulletins (initially called Reports) were issued between June 28, 1913, and July 1, 1914. Bulletins were issued monthly after July 1, 1914, though they were still named Weekly Bulletins until January 1919. Starting with the February 1919 issue, the Bulletins were named Monthly Bulletins, and they continued to be issued monthly until the series ceased in July 1929. During a single year, 1915, Seismometric Bulletins were also issued quarterly. These four issues contain summaries of seismic observations recorded by the then-nascent Whitney Laboratory of Seismology, located underground in a vault near the summit of Kīlauea. Two of the bulletins are misnumbered: • April 1916 volume IV no. 4 incorrectly says April 1915 volume III no. 4 • September 1916 volume IV no. 9 incorrectly says September 1916 volume VI no. 9

Hawaii↗
USGS1915

Hawaiian Volcano Observatory seismometric bulletins - 1915

The Hawaiian Volcano Observatory (HVO) Bulletin series was an informal publication issued between the years 1913 to 1929. Individual issues contain information on volcanic and earthquake activity, volcano research, and volcano monitoring in Hawaii, and issues often included photographs, sketches, and data plots. Information on volcanic activity at other locations is also occasionally included. The Bulletin series was published by HVO through the Hawaiian Volcano Research Association. Weekly Bulletins (initially called Reports) were issued between June 28, 1913, and July 1, 1914. Bulletins were issued monthly after July 1, 1914, though they were still named Weekly Bulletins until January 1919. Starting with the February 1919 issue, the Bulletins were named Monthly Bulletins, and they continued to be issued monthly until the series ceased in July 1929. During a single year, 1915, Seismometric Bulletins were also issued quarterly. These four issues contain summaries of seismic observations recorded by the then-nascent Whitney Laboratory of Seismology, located underground in a vault near the summit of Kīlauea. Two of the bulletins are misnumbered: • April 1916 volume IV no. 4 incorrectly says April 1915 volume III no. 4 • September 1916 volume IV no. 9 incorrectly says September 1916 volume VI no. 9

Hawaii↗
USGS2022

On the documentation, independence, and stability of widely used seismological data products

Earthquake scientists have traditionally relied on relatively small data sets recorded on small numbers of instruments. With advances in both instrumentation and computational resources, the big-data era, including an established norm of open data-sharing, allows seismologists to explore important issues using data volumes that would have been unimaginable in earlier decades. Alongside with these developments, the community has moved towards routine production of interpreted data products such as seismic moment tensor catalogs that have provided an additional boon to earthquake science. As these products have become increasingly familiar and useful, it is important to bear in mind that they are not data, but rather interpreted data products. As such, they differ from data in ways that can be important, but not always appreciated. Important - and sometimes surprising - issues can arise if methodology is not fully described, data from multiple sources are included, or data products are not versioned (time-stamped). The line between data and data products is sometimes blurred, leading to an underappreciation of issues that affect data products. This note illustrates examples from two widely used data products: moment tensor catalogs and Did You Feel It? (DYFI) macroseismic intensity values. These examples show that increasing a data product’s documentation, independence, and stability can make it even more useful. To ensure the reproducibility of studies using data products, time-stamped products should be preserved, for example as electronic supplements to published papers, or, ideally, a more permanent repository.

Frontiers in Earth Science↗
USGS2005

An evaluation of the strong ground motion recorded during the May 1, 2003 Bingol Turkey, earthquake

An important record of ground motion from a M 6.4 earthquake occurring on May 1, 2003, at epicentral and fault distances of about 12 and 9 km, respectively, was obtained at a station near the city of Bingöl, Turkey. The maximum peak ground values of 0.55g and 36 cm/s are among the largest ground-motion amplitudes recorded in Turkey. From simulations and comparisons with ground motions from other earthquakes of comparable magnitude, we conclude that the ground motion over a range of frequencies is unusually high. Site response may be responsible for the elevated ground motion, as suggested from analysis of numerous aftershock recordings from the same station. The mainshock motions have some interesting seismological features, including ramps between the P- and S-wave that are probably due to near- and intermediate-field elastic motions and strong polarisation oriented at about 39 degrees to the fault (and therefore not in the fault-normal direction). Simulations of motions from an extended rupture explain these features. The N10E component shows a high-amplitude spectral acceleration at a period of 0.15 seconds resulting in a site specific design spectrum that significantly overestimates the actual strength and displacement demands of the record. The pulse signal in the N10E component affects the inelastic spectral displacement and increases the inelastic displacement demand with respect to elastic demand for very long periods.

Journal of Earthquake Engineering↗
USGS2015

Self-noise models of five commercial strong-motion accelerometers

Strong‐motion accelerometers provide onscale seismic recordings during moderate‐to‐large ground motions (e.g., up to tens of m/s 2 peak). Such instruments have played a fundamental role in improving our understanding of earthquake source physics (Bock etal. , 2011), earthquake engineering (Youd et al. , 2004), and regional seismology (Zollo et al. , 2010). Although strong‐motion accelerometers tend to have higher noise levels than high‐quality broadband velocity seismometers, their higher clip‐levels provide linear recordings at near‐field sites even for the largest of events where a collocated broadband sensor would no longer be able to provide onscale recordings (Clinton and Heaton, 2002). Recently, the seismological community has begun to make use of strong‐motion accelerometer data even in the absence of large ground motions (e.g., Tibuleac et al. , 2011). The noise floor of the instruments often limits the usefulness of strong‐motion accelerometer data in such studies, because it obscures first arrivals or can make the traces dominated by noise. When a strong‐motion accelerometer is deployed in a quiet setting, the noise floors of the digitizer and the accelerometer tend to dominate the other noise sources (Cauzzi and Clinton, 2013). This situation is unlike that using broadband sensors, in which site conditions are typically the largest contributing source of noise in seismic data, especially at long periods (Wilson et al. , 2002). With the widespread deployment of strong‐motion accelerometers recorded on high resolution digitizers, it is now possible to get continuous high‐rate acceleration data in which the digitizer noise is not the dominant noise source (Cauzzi and Clinton, 2013). To better characterize the noise of a number of commonly deployed accelerometers in a standardized way, we conducted noise measurements on five different models of strong‐motion accelerometers. Our study was limited to traditional accelerometers (Fig. 1) and is in no way exhaustive.

Seismological Research Letters↗
USGS2008

Location of the Green Canyon (Offshore Southern Louisiana) Seismic Event of February 10, 2006

We calculated an epicenter for the Offshore Southern Louisiana seismic event of February 10, 2006 (the 'Green Canyon event') that was adopted as the preferred epicenter for the event by the USGS/NEIC. The event is held at a focal depth of 5 km; the focal depth could not be reliably calculated but was most likely between 1 km and 15 km beneath sea level. The epicenter was calculated with a radially symmetric global Earth model similar to that routinely used at the USGS/NEIC for all earthquakes worldwide. The location was calculated using P-waves recorded by seismographic stations from which the USGS/NEIC routinely obtains seismological data, plus data from two seismic exploration arrays, the Atlantis ocean-bottom node array, operated by BP in partnership with BHP Billiton Limited, and the CGG Green Canyon phase VIII multi-client towed-streamer survey. The preferred epicenter is approximately 26 km north of an epicenter earlier published by the USGS/NEIC, which was obtained without benefit of the seismic exploration arrays. We estimate that the preferred epicenter is accurate to within 15 km. We selected the preferred epicenter from a suite of trial calculations that attempted to fit arrival times of seismic energy associated with the Green Canyon event and that explored the effect of errors in the velocity model used to calculate the preferred epicenter. The various trials were helpful in confirming the approximate correctness of the preferred epicenter and in assessing the accuracy of the preferred epicenter, but none of the trial calculations, including that of the preferred epicenter, was able to reconcile arrival-time observations and assumed velocity model as well as is typical for the vast majority of earthquakes in and near the continental United States. We believe that remaining misfits between the preferred solution and the observations reflect errors in interpreted arrival times of emergent seismic phases that are due partly to a temporally extended source-time function and partly to failure of our travel-time model to account for the extremely complicated velocity structure of the sedimentary section in which the event occurred.

Open-File Report↗
USGS1982

Design concepts for a Global Telemetered Seismograph Network

This study represents a first step in developing an integrated, real-time global seismic data acquisition system a Global Telemetered Seismograph Network (GTSN). The principal objective of the GTSN will be to acquire reliable, high-quality, real-time seismic data for rapid location and analysis of seismic events. A secondary, but important, objective of the GTSN is to augment the existing off-line seismic data base available for research. The deployment of the GTSN will involve a variety of interrelated activities development of the data acquisition and receiving equipment, establishment of satellite and terrestrial communication links, site selection and preparation, training of station personnel, equipment installation, and establishment of support facilities. It is a complex program and the development of a sound management plan will be essential. The purpose of this study is not to fix design goals or dictate avenues of approach but to develop working concepts that may be used as a framework for program planning. The international exchange of seismic data has been an important factor in the progress that has been made during the past two decades in our understanding of earthquakes and global tectonics. The seismic data base available for analysis and research is derived principally from the Global Seismograph Network (GSN), which is funded and managed by the U.S. Geological Survey (USGS). The GSN comprises some 120 seismograph stations located in more than 60 countries of the world. Established during the 1960 s with the installation of the World-Wide Standardized Seismograph Network (WWSSN) , the GSN has been augmented in recent years by the installation of more advanced data systems, such as the Seismic Research Observatories (SRO), the modified High-Gain LongPeriod (ASRO) seismographs, and the digital WWSSN (DWWSSN). The SRO, ASRO, and DWWSSN stations have the common, distinctive feature of digital data recording, so they are known collectively as the Global Digital Seismograph Network (GDSN). The fundamental objective in operating the GSN is to create and update a seismic data base that is accessible without restrictions to organizations and research scientists throughout the world. The USGS provides cooperating stations with instrumentation, training, and continuing support, including supplies and on-site maintenance. In return, the host organization operates the equipment and sends the recorded data to the USGS. Analog data (seismograms) are microfilmed and about four million copies are requested annually by researchers. Digital data, which are recorded on magnetic tape, are organized by the USGS Albuquerque Seismological Laboratory (ASL) into networkday tapes and copies of the day tapes are furnished to data users through national and regional data centers. After copying, original data are returned to the stations and used for local research. Most of the stations in the GSN also provide the USGS with seismic readings « phase arrival times and amplitudes scaled from the seismograms. These readings are transmitted on a daily or biweekly basis via commercial or diplomatic communication channels. They are used by the USGS National Earthquake Information Service (NEIS) to determine the location and magnitude of earthquakes occurring throughout the world. The results are published monthly in bulletins that are distributed to the participating stations and virtually all scientific organizations that are involved in seismological studies. It is a much-valued service that provides a current, updated catalog of seismic activity on a global scale. The NEIS also has the responsibility for rapid reporting of large and potentially destructive earthquakes. The NEIS issues news bulletins as soon as possible after the occurrence of magnitude 6.5 or greater earthquakes (magnitude 5 or greater in the conterminous United States). The news bulletins are sent to disaster relief, public safety, and other interested organizations. Tsunami warnings issued to countries bordering the Pacific Ocean are based initially on earthquake location and magnitude data. Rapid reporting of earthquakes requires real-time waveform data or readings. Currently, signals are being telemetered from more than thirty stations in the United States to the NEIS, which is located in Golden, Colorado. An extension of the telemetry network to other countries will provide the seismological community with a significantly improved means of monitoring earthquake activity in real time; it will lower the response time for determining the location and magnitude of potentially destructive or tsunamigenic earthquakes and it will provide more timely information that may be needed by governments to respond promptly.

Open-File Report↗
USGS2003

Old Seismic bulletins to 1920: A collective heritage from early seismologists

This chapter focuses on collective heritage from early seismologists. Scientists began systematic instrumental observation of earthquakes in the latter part of the 19 th century. Several authors describe the history of the development of an adequate instrumentation for seismology. In the 1880s, scientists in Italy, Japan, and Germany began to record more or less continuously the ground motion with their newly developed seismographs. Because of the limited ability to reproduce the original (analog) paper seismograms, seismologists had to describe their observations in words and numbers. The recording instruments were able to produce seismograms in which one could distinguish between the onsets of all three wave types (i.e., P, S, and surface waves), and a common vocabulary for the description of these records was developed. During the last half of the 19 th century, scientists in many countries began to systematically collect data of macro seismically observed earthquakes and the locations of these events, known only on the basis of such data. In some countries, scientists and/or their governments established special committees or commissions to do this work. The earthquake lists and bulletin data from the early seismic stations not only document the history of seismology but also have intrinsic scientific value. Even today, these old bulletins are needed for event relocation as our technique for earthquake location improves. They are also useful for magnitude analysis to establish a consistent magnitude scale.

Book chapter↗
USGS2024

Seismic response comparison of a historical masonry church subject to real and simulated ground motions

In recent years, advanced numerical models and high-performance computing have facilitated the utilization of ground motion time series in the assessment of the non-linear dynamic behavior of historic masonry structures. Since recorded accelerograms can be sparse for specific analysis conditions, stochastic ground motion simulations have become a viable alternative to overcome this limitation. This study simulates the recorded acceleration time series of the Central Italy 2016 earthquake event at the closest station to the town of Macerata using a site-based stochastic approach. The simulated motions are seismologically evaluated using a goodness-of-fit method in terms of various intensity measures. The simulated records, in conjunction with real records, are used to study the non-linear dynamic behavior of San Filippo Neri church located in Macerata. The church of San Filippo represents an important example of Baroque religious architecture in central Italy, which was damaged and closed off to the public after the 2016 earthquake events. The construction was investigated with a vast diagnostic campaign which included on-site testing and dynamic identification tests. The collected data is used to calibrate the dynamic response of a three-dimensional finite element model of the church. The model is finally used to compare the non-linear seismic responses under real and simulated ground motions with the site recorded damage. The results of structural responses demonstrate a strong agreement between the real and simulated records, providing evidence to support the validation of the site-based stochastic simulation.

Macerata↗
USGS2014

Response of Global Navigation Satellite System receivers to known shaking between 0.2 and 20 Hertz

Over the past decade, several technological advances have allowed Global Navigation Satellite Systems (GNSS) receivers to have the capability to record displacements at high frequencies, with sampling rates approaching 100 samples per second (sps). In addition, communication and computer hardware and software have allowed various institutions, including the U.S. Geological Survey (USGS), to retrieve, process, and display position changes recorded by a network of GNSS sites with small, less than 1-s delays between the time that the GNSS receiver records signals from a constellation of satellites and the time that the position is estimated (a method known as “real-time”). These improvements in hardware and software have allowed the USGS to process GNSS (or a subset of the GNSS, the Global Positioning System, GPS) data in real-time at 1 sps with the goal of determining displacements from earthquakes and volcanoes in real-time. However, the current set of GNSS equipment can record at rates of 100 sps, which allows the possibility of using this equipment to record earthquake displacements over the full range of frequencies that typically are recorded by acceleration and velocity transducers. The advantage of using GNSS to record earthquakes is that the displacement, rather than acceleration or velocity, is recorded, and for large earthquakes, the GNSS sensor stays on scale and will not distort the observations due to clipping of the signal at its highest amplitude. The direct observation of displacement is advantageous in estimating the size and spatial extent of the earthquake rupture. Otherwise, when using velocity or acceleration sensors, the displacements are determined by numerical integration of the observations, which can introduce significant uncertainty in the estimated displacements. However, GNSS technology can, at best, resolve displacements of a few millimeters, and for most earthquakes, their displacements are less than 1 mm. Consequently, to be useful, GNSS data are only relevant for the large earthquakes with magnitudes (M) exceeding M5.5 at best. With the capability to record GNSS data at high-rate, at sampling rates typical for seismological applications, experiments are needed to quantify the response of GNSS to shaking from earthquakes. There have been a few studies that examine the response of GNSS to strong shaking. One of the first was Elosegui and others (2006), where they simulated surface waves from a distant earthquake and mechanically applied the shaking to a GPS antenna. They processed the 1 sps observations and compared the estimated displacements with the simulated displacements. They determined that the GPS could accurately track the simulated surface wave whose primary frequency spans from 0.01 to 0.1 Hertz (Hz), which spanned the frequency band of the simulation. To test GNSS equipment due to shaking from a large earthquake in the near-field, Wang and others (2012) used a mechanical simulator or shake table with 6 degrees of freedom and studied two different inputs to the simulator—(1) the accelerometer record from one station that was located near the 2010 M8.8 Maule, Chile earthquake, and (2) a 2-Hz sinusoid. Wang and others (2012) analyzed the 2-Hz data with spectral analysis and determined that the displacements observed by the GPS included higher harmonics along with the 2-Hz signal. In addition, the background spectral amplitude was greater during periods of 2-Hz shaking than when at rest. With the simulated M 8.8 earthquake, Wang and others (2012) observed decreased signal to noise for L1 and L2 carrier frequencies of the GPS signal, at times corresponding to high acceleration and jerk (first derivative of acceleration). One of the principal limitations of these experiments was that the displacements of the shake table itself could not be measured independently. Although with the 2-Hz sinusoidal measurements, the input displacements were purely translational, Wang and others (2012) analysis of the data showed that the shake table also included rotational motions which affect horizontal inertial sensors like accelerometers and seismometers at first order. More recently, Ebinuma and Kato (2012) used a GPS simulator to electronically test several GNSS receivers and obtain the receiver characteristics at three frequencies: 1, 2, and 5 Hz. The results showed that the amplitude of 5-Hz displacements recorded by the GPS was, depending on the receiver model, between 30 and 125 percent more than the displacement input to the simulator. At low frequencies, the GPS displacement was nearly equal to the input displacement. In addition, Ebinuma and Kato (2012) examined how each receiver model amplified an earthquake displacement record in the 2–8 Hz band. The simulated earthquake was the 2008 moment magnitude (Mw) 6.8 Iwate-Miyagi earthquake where, for the simulated record, acceleration peaked at 1 G. The study discussed here builds on the tests by Ebinuma and Kato (2012), but rather than using electronic simulation, the tests are setup outdoors and closer to actual field installations of GNSS equipment. We used a one-dimensional shake table capable of 400 mm of displacement and high acceleration; the shake table also is constrained by a precision linear slider to have very low tilt that would affect inertial sensors. In addition, the stage position can be accurately monitored independent of the GNSS hardware and, importantly, provides a reference to compare with the estimated displacements from the GNSS data. Our tests spanned a greater frequency range from 0.2 to 20 Hz and we used equipment from three different manufacturers covering five different combinations of receivers and antennas. In addition, we have been able to simulate the frequency response of the GNSS equipment using a simple, causal filter. The quality of the filter was tested using additional test data where a step function in displacement was applied to the shake table. The observed displacements from the GNSS data show an overshoot in displacement at the time of the step or transition of the stage. That overshoot was accurately predicted using the filter design derived from our sinusoidal displacement tests. Similar to Wang and others (2012), we also examined the GPS displacement records using standard spectral techniques. However, we extended their work by evaluating several models of GNSS receivers using a variety of input frequencies. Because our shake table was limited on acceleration and displacement, we did not attempt to duplicate the high shaking associated with high magnitude earthquakes. However, because our shake table could measure the table displacement, we could directly compare the measured GPS displacements with the true displacements.

Open-File Report↗
USGS2013

Finite-fault source inversion using teleseismic P waves: Simple parameterization and rapid analysis

We examine the ability of teleseismic P waves to provide a timely image of the rupture history for large earthquakes using a simple, 2D finite‐fault source parameterization. We analyze the broadband displacement waveforms recorded for the 2010 M w ∼7 Darfield (New Zealand) and El Mayor‐Cucapah (Baja California) earthquakes using a single planar fault with a fixed rake. Both of these earthquakes were observed to have complicated fault geometries following detailed source studies conducted by other investigators using various data types. Our kinematic, finite‐fault analysis of the events yields rupture models that similarly identify the principal areas of large coseismic slip along the fault. The results also indicate that the amount of stabilization required to spatially smooth the slip across the fault and minimize the seismic moment is related to the amplitudes of the observed P waveforms and can be estimated from the absolute values of the elements of the coefficient matrix. This empirical relationship persists for earthquakes of different magnitudes and is consistent with the stabilization constraint obtained from the L‐curve in Tikhonov regularization. We use the relation to estimate the smoothing parameters for the 2011 M w 7.1 East Turkey, 2012 M w 8.6 Northern Sumatra, and 2011 M w 9.0 Tohoku, Japan, earthquakes and invert the teleseismic P waves in a single step to recover timely, preliminary slip models that identify the principal source features observed in finite‐fault solutions obtained by the U.S. Geological Survey National Earthquake Information Center (USGS/NEIC) from the analysis of body‐ and surface‐wave data. These results indicate that smoothing constraints can be estimated a priori to derive a preliminary, first‐order image of the coseismic slip using teleseismic records.

Darfield, El Mayor-Cucapah↗