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Results for “Seismological Research Letters”

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

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USGS1998

The Soufriere Hills eruption, Montserrat, British West Indies: Introduction to special section, part 1

The special section on the eruption of Soufriere Hills volcano is a collection of 24 papers that summarises the early scientific work of the Montserrat Volcano Observatory. Part 1 of the special section, published in a previous issue of GRL , provided a sampling of the multidisciplinary investigations undertaken at Montserrat. The papers published in Part 1 included an overview of the eruption, investigations on seismicity, ground deformation studies, and petrology. The papers of this issue comprise Part 2 of the special section. These papers also cover a broad spectrum of topics, including various topics in seismology, petrology, pyroclastic flow models, gas chemistry, hydrothermal systems, and tsunami models. In general, papers in Part 1 may be said to be more observational- or data-orientated, and those of Part 2 more model-orientated, but indeed there is much overlap of descriptive material, data, and modelling within the individual contributions. Considered in total the collection presents a representative summary of the scientific effort carried out in Montserrat through much of 1997.

Geophysical Research Letters↗

USGS2014

Breaking the oceanic lithosphere of a subducting slab: the 2013 Khash, Iran earthquake

[1] Large intermediate depth, intraslab normal faulting earthquakes are a common, dangerous, but poorly understood phenomenon in subduction zones owing to a paucity of near field geophysical observations. Seismological and high quality geodetic observations of the 2013 M w 7.7 Khash, Iran earthquake reveal that at least half of the oceanic lithosphere, including the mantle and entire crust, ruptured in a single earthquake, confirming with unprecedented resolution that large earthquakes can nucleate in and rupture through the oceanic mantle. A rupture width of at least 55 km is required to explain both InSAR observations and teleseismic waveforms, with the majority of slip occurring in the oceanic mantle. Combining our well-constrained earthquake slip distributions with the causative fault orientation and geometry of the local subduction zone, we hypothesize that the Khash earthquake likely occurred as the combined result of slab bending forces and dehydration of hydrous minerals along a preexisting fault formed prior to subduction.

Geophysical Research Letters↗

USGS2020

Six-axis ground motion measurements of caldera collapse at Kīlauea Volcano, Hawaiʻi - More data, more puzzles?

Near‐field recordings of large earthquakes and volcano‐induced events using traditional seismological instrumentation often suffer from unaccounted effects of local tilt and saturation of signals. Recent hardware advances have led to the development of the blueSeis‐3A, a very broadband, highly sensitive rotational motion sensor. We installed this sensor in close proximity to permanently deployed classical instrumentation (i.e., translational seismometer, accelerometer, and tiltmeter) at the Hawaiian Volcano Observatory (USGS). There, we were able to record three ~Mw 5 earthquakes associated with large collapse events during the later phase of the 2018 Kīlauea summit eruption. Located less than 2 km from the origins of these sources, the combined six‐axis translational and rotational measurements revealed clear static rotations around all three coordinate axes. With these six component recordings, we have been able to reconstruct the complete time history of ground motion of a fixed point during an earthquake for the first time.

Hawaii↗

USGS2012

Rapid determination of global moment-tensor solutions

In an effort to improve data services, the National Earthquake Information Center has begun a program, in cooperation with the Incorporated Research Institutions for Seismology Data Management Center (IRIS DMC), to produce rapid estimates of the seismic moment tensor for most earthquakes with a body-wave magnitude of 5.8 or greater. Although this program is still undergoing testing and fine-tuning, an estimate of the moment tensor can usually be produced within 20 minutes of the arrival of the broadband P -waveform data from the IRIS DMC. Although the speed with which this data can be obtained varies, in many cases a solution can be obtained within two hours of the earthquake. These solutions do not vary significantly from the final solutions determined using the entire network. Because of the manner in which the data and the synthetic seismograms are aligned, the method is insensitive to the effects of timing errors, epicentral mislocation, and lateral heterogeneity in earth structure. This procedure was implemented in May 1993; the results from that month are presented here.

Geophysical Research Letters↗

USGS2019

The August 2018 Kaktovik earthquakes: Active tectonics in northeastern Alaska revealed With InSAR and seismology

The largest earthquakes recorded in northern Alaska (M w 6.4 and M w 6.0) occurred ~6 hours apart on August 12, 2018 in the northeastern Brooks Range. The earthquakes were captured by Sentinel-1 InSAR satellites and Earthscope Transportable Array seismic data, giving insight into the little-known active tectonic processes of Arctic Alaska, obscured until recently by sparse data availability. In this study, InSAR modelling, teleseismic back projections, calibrated hypocentral relocations and regional moment tensor solutions resolve two previously unknown, SSW-dipping right-lateral fault segments. These are the first active faults identified as conjugate to the NE-trending sinistral Canning Displacement Zone directly to the west, which is therefore a more complex zone of diffuse faulting than previously thought. The northeastern Brooks Range has been characterized as an area of low to moderate seismic hazard, but these earthquakes illustrate the potential for larger, possibly destructive events in a region earmarked for rapid resource development.

Alaska↗

USGS2002

Seismological evidence for a sub-volcanic arc mantle wedge beneath the Denali volcanic gap, Alaska

Arc volcanism in Alaska is strongly correlated with the 100 km depth contour of the western Aluetian Wadati-Benioff zone. Above the eastern portion of the Wadati-Benioff zone however, there is a distinct lack of volcanism (the Denali volcanic gap). We observe high Poisson's ratio values (0.29-0.33) over the entire length of the Alaskan subduction zone mantle wedge based on regional variations of Pn and Sn velocities. High Poisson's ratios at this depth (40-70 km), adjacent to the subducting slab, are attributed to melting of mantle-wedge peridotites, caused by fluids liberated from the subducting oceanic crust and sediments. Observations of high values of Poisson's ratio, beneath the Denali volcanic gap suggest that the mantle wedge contains melted material that is unable to reach the surface. We suggest that its inability to migrate through the overlying crust is due to increased compression in the crust at the northern apex of the curved Denali fault.

Alaska↗