scholarly journals The seismic and hydroacoustic stations on Socorro Island: Early results

2007 ◽  
Vol 46 (1) ◽  
pp. 3-18
Author(s):  
Raúl W. Valenzuela ◽  
Javier F. Pacheco ◽  
José Pereira ◽  
Jorge A. Estrada ◽  
Jesús A. Pérez ◽  
...  
Keyword(s):  
Acoustic Waves ◽  
High Frequency ◽  
Seismic Waves ◽  
Kamchatka Peninsula ◽  
Nuclear Test ◽  
Fracture Zones ◽  
Early Results ◽  
Socorro Island ◽  
High Frequency Seismic Waves ◽  
Test Ban

A seismic and hydroacoustic network on Socorro Island was installed jointly by the Servicio Sismolo?gico Nacional, Instituto de Geofi?sica, Universidad Nacional Auto?noma de Me?xico, and the Comprehensive Nuclear-Test-Ban Treaty Organization. The detection of ten earthquakes in June and July 2004 is reported in this study. These events occurred at epicentral distances between 209 and 9050 km and ranged in magnitude between 3.9 and 6.8. An event in the Kamchatka Peninsula featured arrivals of teleseismic high-frequency P and pP waves from a distance of 8245 km. An earthquake in the Guerrero-Oaxaca, Mexico, region shows clear seismic and T phases. Three earthquakes in the Rivera Fracture Zone were recorded, thus leading to the expectation of the continued detection of events from nearby fracture zones as well as earthquakes generated by volcanoes on Socorro and San Benedicto Islands. The analysis of the T phases from several events validates the design of the network, with three sites around the island in order to record arrivals from all directions. High frequency seismic waves generated by acoustic waves attenuate as they propagate through the rock from one end of the island to the other. Consequently small or distant events are difficult to detect at the far side of the island.

High frequency seismic waves and slab structures beneath Italy

2014 ◽  
Vol 391 ◽  
pp. 212-223 ◽  
Author(s):  
Daoyuan Sun ◽  
Meghan S. Miller ◽  
Nicola Piana Agostinetti ◽  
Paul D. Asimow ◽  
Dunzhu Li
Keyword(s):  
High Frequency ◽  
Seismic Waves ◽  
High Frequency Seismic Waves

High‐frequency reflections in granite? Delineation of the weathering front in granodiorite at Piñon Flat, California

Geophysics ◽  
1999 ◽  
Vol 64 (6) ◽  
pp. 1828-1835 ◽  
Author(s):  
Stanley J. Radzevicius ◽  
Gary L. Pavlis
Keyword(s):  
High Frequency ◽  
Seismic Waves ◽  
Lower Layer ◽  
Specular Reflection ◽  
Earth Model ◽  
Remarkable Feature ◽  
Reflection Data ◽  
Weathered Layer ◽  
High Frequency Seismic Waves ◽  
Seismic Lines

We analyze data from two orthogonal seismic lines 336 m in length collected at Piñon Flat, California, over weathered granodiorite bedrock. Each line was made up of 10 reversed segments 84 m in length. We analyzed the first arrivals from these data and found dramatic variations in velocity along the profiles. An upper layer (approximately 2-m thick) known from trenching to be composed of soil and sandy grus had measured velocities ranging from 400 to 700 m/s. Velocities inferred from refraction analysis of first arrivals of the reversed lines revealed a heterogeneous lower layer below the soil with measured velocities of 1600–2700 m/s by a depth of 15 m. We interpret these data to be measuring velocities of a deeply weathered unit characterized by granodiorite corestones embedded in a matrix of saprolite. The most remarkable feature of these data emerged from attempting to process the same data as reflection data. Simple bandpass filtering in the 250–400 Hz band revealed a bright, impulsive arrival with three characteristic properties: (1) irregular velocity moveout that is inconsistent with that expected from a layered earth model, (2) the arrival is at a nearly constant time‐depth on all data, and (3) the arrival tends to be followed by a ringing coda whose frequency varies from trace to trace. This arrival ties exactly with a velocity discontinuity measured in a borehole located on one of the profiles that we interpret as the base of the weathered layer. We suggest this arrival is a specular reflection from a weathering front that occurs along horizontal sheeting joints at a fixed depth below the surface. This surface acts as an effective mirror for high‐frequency seismic waves which are then channeled upward through an intact, high-Q path of unaltered blocks of granodiorite to define the observed signals at the surface.

The 2010 Haiti Earthquake Disaster: The ShakeMap that could have been...

2020 ◽  
Author(s):  
Shahar Shani-Kadmiel ◽  
Gil Averbuch ◽  
Pieter Smets ◽  
Jelle Assink ◽  
Läslo Evers
Keyword(s):  
Acoustic Waves ◽  
Seismic Waves ◽  
Source Region ◽  
Low Frequency ◽  
Processing Technique ◽  
Disaster Mitigation ◽  
Haiti Earthquake ◽  
Earthquake Disaster ◽  
Global Coverage ◽  
Test Ban

<p>When an earthquake occurs, it is important to rapidly assess the severity of the consequences. The distribution of shaking intensity around the epicenter, known as the ShakeMap, is a key component in this process and is crucial for guiding first responders to the region. Whereas earthquake source characteristics, e.g., location and magnitude, can be rapidly determined using distant seismic stations, ground motion measurements from stations in the near-source region are needed to generate an adequate ShakeMap. When few or no seismometers exist in the region, ground motions are only estimated and the ShakeMap can be grossly inaccurate.</p><p>Besides seismic waves, earthquakes generate infrasound, i.e., inaudible acoustic waves in the atmosphere. Due to the low frequency nature of infrasound, and facilitated by waveguides in the atmosphere, signals propagate over long ranges with limited attenuation and are detected at ground-based stations. Here we show, that acousto-ShakeMaps, indicating the relative shaking intensity, can be rapidly generated using remotely detected infrasound. We illustrate this with infrasound from the 2010 Mw 7.0 Port-au-Prince, Haiti earthquake, detected in Bermuda, over 1700 km away from Haiti.</p><p>Such observations are made possible by: (1) An advanced array processing technique that enables the detection of coherent wavefronts, even when amplitudes are below the noise level, and (2) A backprojection technique that maps infrasound detections in time to their origin on the Earth's surface.</p><p>Infrasound measurements are conducted globally for the verification of the Comprehensive Nuclear-Test-Ban Treaty and together with regional infrasound networks allow for an unprecedented global coverage. This makes infrasound as an earthquake disaster mitigation technique feasible for the first time.</p>

Landslide Characteristics Revealed by High-Frequency Seismic Waves from the 2017 Landslide in Central Japan

2020 ◽  
Vol 91 (5) ◽  
pp. 2719-2729
Author(s):  
Issei Doi ◽  
Takuto Maeda
Keyword(s):  
High Frequency ◽  
Seismic Waves ◽  
Wave Packets ◽  
Impulsive Phase ◽  
Frequency Component ◽  
Source Location ◽  
High Frequency Component ◽  
Central Japan ◽  
Location Determination ◽  
High Frequency Seismic Waves

Abstract The recent development of advanced seismograph networks offers us a chance to remotely detect landslide occurrences with high-frequency (>∼1  Hz) components. This study examined a landslide in central Japan that produced clearly detectable seismic signals at multiple seismic stations in a permanent network. Wave packets propagated with a group velocity of 3  km/s from the landslide area. Using a source location determination method with amplitude information from the high-frequency component, the source location of the wave packets was shown to be in the vicinity of the landslide with an error of 5 km. Moreover, seismograms specific to this landslide also contained a distinct impulsive phase with a source located in the vicinity of the landslide. The study demonstrated that seismic waves with a high-frequency component from landslides can be used to estimate their mechanisms as well as their locations when they are recognized by a routine seismic network.

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