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

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At least 937 records · Page 52Linked to original sources

USGS2010

Analysis of nonvolcanic tremor on the San Andreas Fault near Parkfield, CA using U.S. Geological Survey Parkfield Seismic Array

Reports by Nadeau and Dolenc (2005) that tremor had been detected near Cholame Valley spawned an effort to use UPSAR (U. S. Geological Survey Parkfield Seismic Array) to study characteristics of tremor. UPSAR was modified to record three channels of velocity at 40–50 sps continuously in January 2005 and ran for about 1 month, during which time we recorded numerous episodes of tremor. One tremor, on 21 January at 0728, was recorded with particularly high signal levels as well as another episode 3 days later. Both events were very emergent, had a frequency content between 2 and 8 Hz, and had numerous high-amplitude, short-duration arrivals within the tremor signal. Here using the first episode as an example, we discuss an analysis procedure, which yields azimuth and apparent velocity of the tremor at UPSAR. We then provide locations for both tremor episodes. The emphasis here is how the tremor episode evolves. Twelve stations were operating at the time of recording. Slowness of arrivals was determined using cross correlation of pairs of stations; the same method used in analyzing the main shock data from 28 September 2004. A feature of this analysis is that 20 s of the time series were used at a time to calculate correlation; the longer windows resulted in more consistent estimates of slowness, but lower peak correlations. These values of correlation (peaks of about 0.25), however, are similar to that obtained for the S wave of a microearthquake. Observed peaks in slowness were traced back to source locations assumed to lie on the San Andreas fault. Our inferred locations for the two tremor events cluster near the locations of previously observed tremor, south of the Cholame Valley. Tremor source depths are in the 14–24 km range, which is below the seismogenic brittle zone, but above the Moho. Estimates of error do not preclude locations below the Moho, however. The tremor signal is very emergent but contains packets that are several times larger than the background tremor signal and lasts about 5 s. These impulsive wavelets are similar to low-frequency earthquakes signals seen in Japan but appear to be broader band rather than just higher in low-frequency energy. They may be more appropriately called high-energy tremor (HET). HET signals at UPSAR correlate well with the record of this event from station GHIB of the HRSN borehole array at Parkfield and HETs typically have a higher cross-correlation coefficient than the rest of the tremor event. The amplitudes of a large HET are consistent with a magnitude of 0.1 when compared with a M2.3 event that had about the same epicenter. Polarizations of the tremor episode at UPSAR are mostly just north of east. Both linearity and azimuth evolve over time suggesting a change in tremor source location over time and linearity is typically higher at the HETs.

California↗

USGS2016

Responses of a tall building in Los Angeles, California as inferred from local and distant earthquakes

Increasing inventory of tall buildings in the United States and elsewhere may be subjected to motions generated by near and far seismic sources that cause long-period effects. Multiple sets of records that exhibited such effects were retrieved from tall buildings in Tokyo and Osaka ~ 350 km and 770 km from the epicenter of the 2011 Tohoku earthquake. In California, very few tall buildings have been instrumented. An instrumented 52-story building in downtown Los Angeles recorded seven local and distant earthquakes. Spectral and system identification methods exhibit significant low frequencies of interest (~0.17 Hz, 0.56 Hz and 1.05 Hz). These frequencies compare well with those computed by transfer functions; however, small variations are observed between the significant low frequencies for each of the seven earthquakes. The torsional and translational frequencies are very close and are coupled. Beating effect is observed in at least two of the seven earthquake data.

Earthquake Spectra↗

USGS1978

VAMPs—Possible hydrocarbon-bearing structures in Bering Sea Basin: Geologic notes

Narrow (1 to 2 km) subsurface columns of concave reflection horizons are common time-base seismic profiles collected in the Bering Sea basin. The columns of recorded downflexures are thought to be velocity pulldowns and commonly are associated with one or more arched or gently domed high-amplitude reflection horizons about 100 m higher in the section. Inferred from this association is that subsurface deposits characterized by anomalously low acoustic velocity are present. We refer to the velocity-anomaly and reflection-amplitude association as a velocity-amplitude feature, or VAMP, and speculate that VAMPs are deep-seated “bright spots” underlain by a strong velocity pulldown possibly caused by gas-charged deposits.

AAPG Bulletin↗

USGS2019

Length-scale-dependent relationships between VS30 and topographic slopes in southern California

In engineering seismology, the time‐averaged shear‐wave velocity ( ⁠ V S ⁠ ) of the upper 30 m of the crust ( ⁠V S30⁠ ) is the primary parameter used in ground‐motion models to predict seismic site effects. ⁠V S30⁠ is typically derived from in situ recordings of V S ⁠ , although proxy‐based approaches (using geologic and/or geomorphometric classifications) are provisionally adopted when measurement‐based ⁠V S30⁠ are sparse or not readily available. Despite the acceptance of proxy approaches, there are limited studies that examine the empirical relationships between ⁠V S30⁠ and topographic attributes measured from various length scales and different resolutions of the digital elevation model. In this study, we examine the relationships between compiled ⁠V S30⁠ measurements from 218 sites in southern California and topographic metrics of slope and relief measured over various length scales. We find that the correlations between topographic metrics and ⁠V S30⁠ are weak but statistically significant. The correlations are improved when topographic slopes and relief are measured over length scales longer than typical hillslopes and ⁠V S30⁠ sites are separated by different geologic groups. This is likely because ⁠V S30⁠ ⁠ , especially on the rock sites, is better reflected in topographic metrics that capture large‐scale topographic relief, as well as landscape positions such as hilltops and valley bottoms.

California↗

USGS2025

Examining the role of elevated and sustained strain in dynamically triggering earthquakes on the Anza section of the San Jacinto fault

Microearthquakes can be dynamically triggered in southern California by remote earthquakes. However, directly connecting dynamic triggering mechanisms with observational data remains challenging. One proposed failure mechanism suggests that both the amplitude and duration of cyclic fatigue caused by the passing seismic wave contribute to triggering occurrence. Here, we measure dynamic strains recorded by borehole strainmeters in the Anza section of the San Jacinto fault zone from 710 earthquakes that occurred over 300 km away between 2008 and 2017 to systematically investigate the role of elevated and sustained strain in controlling dynamic triggering. We design a suite of tests to evaluate whether specific amplitude thresholds and durations of strain can predict dynamic triggering cases. We further test whether the peak dynamic strain (PDS) can predict triggering occurrence in combination with the strain amplitude and duration. Based on these tests, there is no strain amplitude–duration threshold that can distinguish triggering occurrence in Anza. Dynamic triggering is more likely to occur if a remote earthquake causes a PDS above 100 nanostrain, though many cases were triggered at smaller PDSs. The lack of clear correlation between triggering and characteristics of the dynamic strain field suggests that the tested features of the incoming waves do not determine triggering occurrence and local fault conditions and slip processes are more important in controlling dynamic triggering in Anza.

California↗

USGS2021

Short‐period surface‐wave tomography in the continental United States— A resource for research

The variation of phase and group velocity dispersion of Love and Rayleigh waves was determined for the continental United States and adjacent Canada. By processing ambient noise from the broadband channels of the Transportable Array (TA) of USArray and several Program for the Array Seismic Studies of the Continental Lithosphere experiments and using some earthquake recordings, the effort was focused on determining dispersion down to periods as short as 2 s. The relatively short distances between TA stations permitted the use of a 25    km × 25    km "> 25 km × 25 km grid for the four independent tomographic inversions (Love and Rayleigh and phase and group velocity). One reason for trying to obtain short‐period dispersion was to have a data set capable of constraining upper crust velocity models for use in determining regional moment tensors. The benefit of focusing on short‐period dispersion is apparent in the tomography maps—shallow geologic structures such as the Mid‐Continent Rift, and the Michigan, Illinois, Anadarko, Arkoma, and Appalachian basins are imaged. In our processing, we noted that the phase velocities were more robustly determined than the group velocities. We also noted that the inability to obtain dispersion at short periods shows distinct regional patterns that may be related to the local upper crust structure.

Seismological Research Letters↗

USGS1996

Landslides triggered by the 1994 Northridge, California, earthquake

The 17 January 1994 Northridge, California, earthquake ( M w = 6.7) triggered more than 11,000 landslides over an area of about 10,000 km 2 . Most of the landslides were concentrated in a 1000-km 2 area that included the Santa Susana Mountains and the mountains north of the Santa Clara River valley. We mapped landslides triggered by the earthquake in the field and from 1:60,000-nominal-scale aerial photography provided by the U.S. Air Force and taken the morning of the earthquake; these mapped landslides were subsequently digitized and plotted in a GIS-based format. Most of the triggered landslides were shallow (1- to 5-m thick), highly disrupted falls and slides within weakly cemented Tertiary to Pleistocene clastic sediment. Average volumes of these types of landslides were less than 1000 m 3 , but many had volumes exceeding 100,000 m 3 . The larger disrupted slides commonly had runout paths of more than 50 m, and a few traveled as far as 200 m from the bases of steep parent slopes. Deeper (>5-m thick) rotational slumps and block slides numbered in the tens to perhaps hundreds, a few of which exceeded 100,000 m 3 in volume. Most of these were reactivations of previously existing landslides. The largest single landslide triggered by the earthquake was a rotational slump/block slide having a volume of 8 × 10 6 m 3 . Analysis of the mapped landslide distribution with respect to variations in (1) landslide susceptibility and (2) strong shaking recorded by hundreds of instruments will form the basis of a seismic landslide hazard analysis of the Los Angeles area.

California↗

USGS2013

Alaska earthquake source for the SAFRR tsunami scenario: Chapter B in The SAFRR (Science Application for Risk Reduction) Tsunami Scenario

Tsunami modeling has shown that tsunami sources located along the Alaska Peninsula segment of the Aleutian-Alaska subduction zone have the greatest impacts on southern California shorelines by raising the highest tsunami waves for a given source seismic moment. The most probable sector for a M w ~ 9 source within this subduction segment is between Kodiak Island and the Shumagin Islands in what we call the Semidi subduction sector; these bounds represent the southwestern limit of the 1964 M w 9.2 Alaska earthquake rupture and the northeastern edge of the Shumagin sector that recent Global Positioning System (GPS) observations indicate is currently creeping. Geological and geophysical features in the Semidi sector that are thought to be relevant to the potential for large magnitude, long-rupture-runout interplate thrust earthquakes are remarkably similar to those in northeastern Japan, where the destructive M w 9.1 tsunamigenic earthquake of 11 March 2011 occurred. In this report we propose and justify the selection of a tsunami source seaward of the Alaska Peninsula for use in the Tsunami Scenario that is part of the U.S. Geological Survey (USGS) Science Application for Risk Reduction (SAFRR) Project. This tsunami source should have the potential to raise damaging tsunami waves on the California coast, especially at the ports of Los Angeles and Long Beach. Accordingly, we have summarized and abstracted slip distribution from the source literature on the 2011 event, the best characterized for any subduction earthquake, and applied this synoptic slip distribution to the similar megathrust geometry of the Semidi sector. The resulting slip model has an average slip of 18.6 m and a moment magnitude of M w = 9.1. The 2011 Tohoku earthquake was not anticipated, despite Japan having the best seismic and geodetic networks in the world and the best historical record in the world over the past 1,500 years. What was lacking was adequate paleogeologic data on prehistoric earthquakes and tsunamis, a data gap that also presently applies to the Alaska Peninsula and the Aleutian Islands. Quantitative appraisal of potential tsunami sources in Alaska requires such investigations.

Alaska↗

USGS1990

Magnetic and bathymetric data from R/V FARNELLA cruises FRNL87-1, 87-2, 87-3, 87-4 and 87-5 in the U.S. Atlantic Margin EEZ, southern Blake Escarpment, and Nova Scotia continental rise

During the winter and spring of 1987, the U.S. Geological Survey, in cooperation with the Institute of Oceanographic Sciences of the United Kingdom, collected approximately 31,350 line kilometers (km) of magnetic data and approximately 32,280 line km of bathymetric data in the U.S. Atlantic Margin Exclusive Economic Zone (EEZ), Southern Blake Escarpment, and Nova Scotia Rise (Fig. 1). Collected simultaneously with the magnetic and bathymetric data was a suite of geophysical data. These geophysical datasets will be released at a later date and include GLORIA (Geological LOng-Range Inclined Asdic) sidescan-sonar digital image data, 3.5 kilohertz (kHz) high-resolution sub-bottom profiler records, 10 kHz bottom profiler records from which bathymetric data were derived, and two channel seismic-reflection profiles. Survey line spacing was about 25 km in water depths exceeding 3,000 meters (m) and gradually decreased to less than 5 km in 200 m water depths. No areas were surveyed with depths shallower than 200 m. Orientation of the tracklines varies with respect to the trend of the bathymetric contours for each of the five legs (Fig.l).

Open-File Report↗

USGS1995

Inventory of landslides triggered by the 1994 Northridge, California earthquake

The 17 January 1994 Northridge, California, earthquake (M=6.7) triggered more than 11,000 landslides over an area of about 10,000 km?. Most of the landslides were concentrated in a 1,000-km? area that includes the Santa Susana Mountains and the mountains north of the Santa Clara River valley. We mapped landslides triggered by the earthquake in the field and from 1:60,000-scale aerial photography provided by the U.S. Air Force and taken the morning of the earthquake; these were subsequently digitized and plotted in a GIS-based format, as shown on the accompanying maps (which also are accessible via Internet). Most of the triggered landslides were shallow (1-5 m), highly disrupted falls and slides in weakly cemented Tertiary to Pleistocene clastic sediment. Average volumes of these types of landslides were less than 1,000 m?, but many had volumes exceeding 100,000 m?. Many of the larger disrupted slides traveled more than 50 m, and a few moved as far as 200 m from the bases of steep parent slopes. Deeper ( >5 m) rotational slumps and block slides numbered in the hundreds, a few of which exceeded 100,000 m? in volume. The largest triggered landslide was a block slide having a volume of 8X10E06 m?. Triggered landslides damaged or destroyed dozens of homes, blocked roads, and damaged oil-field infrastructure. Analysis of landslide distribution with respect to variations in (1) landslide susceptibility and (2) strong shaking recorded by hundreds of instruments will form the basis of a seismic landslide hazard analysis of the Los Angeles area.

Open-File Report↗

USGS2012

The 2009 eruption of Redoubt Volcano, Alaska

Redoubt Volcano, an ice-covered stratovolcano on the west side of Cook Inlet, erupted in March 2009 after several months of escalating unrest. The 2009 eruption of Redoubt Volcano shares many similarities with eruptions documented most recently at Redoubt in 1966–68 and 1989–90. In each case, the eruptive phase lasted several months, consisted of multiple ashproducing explosions, produced andesitic lava and tephra, removed significant amounts of ice from the summit crater and Drift glacier, generated lahars that inundated the Drift River valley, and culminated with the extrusion of a lava dome in the summit crater. Prior to the 2009 explosive phase of the eruption, precursory seismicity lasted approximately six months with the fi rst weak tremor recorded on September 23, 2008. The first phreatic explosion was recorded on March 15, and the first magmatic explosion occurred seven days later, at 22:34 on March 22. The onset of magmatic explosions was preceded by a strong, shallow swarm of repetitive earthquakes that began about 04:00 on March 20, 2009, less than three days before an explosion. Nineteen major ash-producing explosions generated ash clouds that reached heights between 17,000 ft and 62,000 ft (5.2 and 18.9 km) ASL. During ash fall in Anchorage, the Ted Stevens International Airport was shut down for 20 hours, from ~17:00 on March 28 until 13:00 on March 29. On March 23 and April 4, lahars with fl ow depths to 10 m in the upper Drift River valley inundated parts of the Drift River Terminal (DRT). The explosive phase ended on April 4 with a dome collapse at 05:58. The April 4 ash cloud reached 50,000 ft (15.2 km) and moved swiftly to the southeast, depositing up to 2 mm of ash fall in Homer, Anchor Point, and Seldovia. At least two and possibly three lava domes grew and were destroyed by explosions prior to the final lava dome extrusion that began after the April 4 event. The fi nal lava dome ceased growth by July 1, 2009, with an estimated volume of 72 Mm 3

Alaska↗

USGS2003

New insights into Kilauea's volcano dynamics brought by large-scale relative relocation of microearthquakes

We investigated the microseismicity recorded in an active volcano to infer information concerning the volcano structure and long-term dynamics, by using relative relocations and focal mechanisms of microearthquakes. There were 32,000 earthquakes of the Mauna Loa and Kilauea volcanoes recorded by more than eight stations of the Hawaiian Volcano Observatory seismic network between 1988 and 1999. We studied 17,000 of these events and relocated more than 70%, with an accuracy ranging from 10 to 500 m. About 75% of these relocated events are located in the vicinity of subhorizontal decollement planes, at a depth of 8-11 km. However, the striking features revealed by these relocation results are steep southeast dipping fault planes working as reverse faults, clearly located below the decollement plane and which intersect it. If this decollement plane coincides with the pre-Mauna Loa seafloor, as hypothesized by numerous authors, such reverse faults rupture the pre-Mauna Loa oceanic crust. The weight of the volcano and pressure in the magma storage system are possible causes of these ruptures, fully compatible with the local stress tensor computed by Gillard et al. [1996]. Reverse faults are suspected of producing scarps revealed by kilometer-long horizontal slip-perpendicular lineations along the decollement surface and therefore large-scale roughness, asperities, and normal stress variations. These are capable of generating stick-slip, large-magnitude earthquakes, the spatial microseismic pattern observed in the south flank of Kilauea volcano, and Hilina-type instabilities. Rupture intersecting the decollement surface, causing its large-scale roughness, may be an important parameter controlling the growth of Hawaiian volcanoes.

Journal of Geophysical Research B: Solid Earth↗

USGS1994

Map showing surficial and hydrologic features in the vicinity of New Madrid, Missouri

This is one in a series of five seismotectonic maps of the seismically active New Madrid area in southeast Missouri and adjacent parts of Arkansas, Kentucky, and Tennessee (table 1). ). We cannot legibly show all the seismotectonic data on a single map, therefore each of the five maps in this series groups a different type of related information. Rhea and others (1994) summarized the background and purpose of the seismotectonic map folio. To aid in locating small features mentioned in the text and tables we have divided the map area into 16 tracts (fig. 1); some of the small features are identified by tract number. The focus of this map is earthquake effects in the New Madrid area. The first part of the discussion is a description of some superficial effects of three great earthquakes that struck the map area during the winter of 1811-12 (Nuttli, 1973). Next, we discuss other possible records of recent deformation that may have bearing on the assessment of seismic hazards. Finally, some features of uncertain origins are discussed; these have unknown bearing on hazard assessment. Some swampy or flooded areas, locally called sunklands, are discussed in two places because two of the sunklands formed or enlarged during the 1811-12 earthquakes, whereas the others are of uncertain origins.

Missouri↗

USGS2020

Recording the aurora borealis (northern lights) at seismometers across Alaska

We examine three continuously recording data sets related to the aurora: all‐sky camera images, three‐component magnetometer data, and vertical‐component, broadband seismic data as part of the EarthScope project (2014 to present). Across Alaska there are six all‐sky cameras, 13 magnetometers, and > 200 "> > 200 >200 seismometers. The all‐sky images and magnetometers have the same objective, which is to monitor space weather and improve our understanding of auroral activity, including the influence on magnetic fields in the ground. These variations in the magnetic field are also visible on seismometers, to the extent that during an auroral event, the long‐period (40–800 s) waves recorded by a seismometer are magnetic field variations, not true ground motion. Although this is a problem—one that can be rectified with magnetic shielding at each seismometer site—it is also an opportunity because the present seismic array in Alaska is much broader than the coverage by magnetometers and all‐sky cameras. Here we focus on three aurora events and document a direct link between aurora images in the night sky and seismometer recordings on ground. Simultaneous recordings by magnetometers provide a critical link between the sky images and the seismometer recordings. We document qualitative correlations among sky, magnetic, and seismic data. The findings suggest that the signature of auroral activity is widespread across seismometers in Alaska, implying that the seismic array could be used to enhance the spatial resolution of the existing network of all‐sky cameras and magnetometers. Future efforts to improve the multisensor seismic stations in Alaska, for the purpose of monitoring seismic and auroral activity, should consider installation of all‐sky cameras, installation of magnetometers, and magnetic shielding of seismic sensors.

Alaska↗

USGS2022

Seismic monitoring solutions for buildings

This chapter introduces seismic monitoring of structural systems for buildings and begins with a historical background of this topic in the United States. After providing the historical context, the chapter reviews common seismic instrumentation issues such as utilization of data, code versus extensive instrumentation, free-field instrumentation, record synchronization requirements and more. Recent developments in damage detection is examined including damage detection based on changes in natural frequencies, permanent deformations, and interstory drift. Finally, applications in Europe, the Middle East, and Japan of seismic monitoring of structural systems for buildings are discussed.

Book chapter↗

USGS2014

Frequency-dependent seismic attenuation in the eastern United States as observed from the 2011 central Virginia earthquake and aftershock sequence

Ground shaking due to earthquakes in the eastern United States (EUS) is felt at significantly greater distances than in the western United States (WUS) and for some earthquakes it has been shown to display a strong preferential direction. Shaking intensity variation can be due to propagation path effects, source directivity, and/or site amplification. In this paper, we use S and Lg waves recorded from the 2011 central Virginia earthquake and aftershock sequence, in the Central Virginia Seismic Zone, to quantify attenuation as frequency‐dependent Q ( f ). In support of observations based on shaking intensity, we observe high Q values in the EUS relative to previous studies in the WUS with especially efficient propagation along the structural trend of the Appalachian mountains. Our analysis of Q ( f ) quantifies the path effects of the northeast‐trending felt distribution previously inferred from the U.S. Geological Survey (USGS) “Did You Feel It” data, historic intensity data, and the asymmetrical distribution of rockfalls and landslides.

Bulletin of the Seismological Society of America↗

USGS2011

Seismicity of the Earth 1900-2010 New Guinea and vicinity

There have been 22 M7.5+ earthquakes recorded in the New Guinea region since 1900. The dominant earthquake mechanisms are thrust and strike slip, associated with the arc-continent collision and the relative motions between numerous local microplates. The largest earthquake in the region was a M8.2 shallow thrust fault event in the northern Papua province of Indonesia that killed 166 people in 1996. The Australia-Pacific plate boundary is over 4,000 km long on the northern margin, from the Sunda (Java) trench in the west to the Solomon Islands in the east. The eastern section is over 2,300 km long, extending west from northeast of the Australian continent and the Coral Sea until it intersects the east coast of Papua New Guinea. The boundary is dominated by the general northward subduction of the Australia plate.

Open-File Report↗

USGS2014

The evolution of seismic monitoring systems at the Hawaiian Volcano Observatory

In the century since the Hawaiian Volcano Observatory (HVO) put its first seismographs into operation at the edge of Kīlauea Volcano’s summit caldera, seismic monitoring at HVO (now administered by the U.S. Geological Survey [USGS]) has evolved considerably. The HVO seismic network extends across the entire Island of Hawai‘i and is complemented by stations installed and operated by monitoring partners in both the USGS and the National Oceanic and Atmospheric Administration. The seismic data stream that is available to HVO for its monitoring of volcanic and seismic activity in Hawai‘i, therefore, is built from hundreds of data channels from a diverse collection of instruments that can accurately record the ground motions of earthquakes ranging in magnitude from <1 to ≥8. In this chapter we describe the growth of HVO’s seismic monitoring systems throughout its first hundred years of operation. Although other references provide specific details of the changes in instrumentation and data handling over time, we recount here, in more general terms, the evolution of HVO’s seismic network. We focus not only on equipment but also on interpretative products and results that were enabled by the new instrumentation and by improvements in HVO’s seismic monitoring, analytical, and interpretative capabilities implemented during the past century. As HVO enters its next hundred years of seismological studies, it is well situated to further improve upon insights into seismic and volcanic processes by using contemporary seismological tools.

Hawaii↗