scholarly journals Post-seismic response of the outer accretionary prism after the 2010 Maule earthquake, Chile

Geosphere ◽  
2019 ◽  
Vol 16 (1) ◽  
pp. 13-32 ◽  
Author(s):  
Anne M. Tréhu ◽  
Alexander de Moor ◽  
José Mieres Madrid ◽  
Miguel Sáez ◽  
C. David Chadwell ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Plate Boundary ◽  
Low Frequency ◽  
Accretionary Prism ◽  
Absolute Pressure ◽  
Ocean Bottom ◽  
Intermediate Band ◽  
Outer Rise ◽  
Maule Earthquake ◽  
Seafloor Pressure

Abstract To investigate the dynamic response of the outer accretionary prism updip from the patch of greatest slip during the 2010 Mw 8.8 Maule earthquake (Chile), 10 ocean-bottom seismometers (OBSs) were deployed from May 2012 to March 2013 in a small network with an inter-instrument spacing of 7–10 km. Nine were recovered, with four recording data from intermediate-band three-component seismometers and differential pressure gauges, and five recording data from absolute pressure gauges (APGs). All instruments were also equipped with fluid flow meters designed to detect very low rates of flow into or out of the seafloor. We present hypocenters for local earthquakes that have S-P times <17 s (i.e., within ∼125 km of the network), with a focus on events located beneath or near the network. Most of the seismicity occurred either near the boundary between the active accretionary prism and continental basement or in the outer rise seaward of the trench. For many outer-rise earthquakes, the P and S arrivals are followed by a distinctive T-phase arrival. Very few earthquakes, and none located with hypocenters deemed “reliable,” were located within the active accretionary prism or on the underlying plate boundary. Nonvolcanic tremor-like pulses and seafloor pressure transients (but no very-low-frequency earthquakes or fluid flow) were also detected. Many of the tremor observations are likely T-phases or reverberations due to soft seafloor sediments, although at least one episode may have originated within the accretionary prism south of the network. The transient seafloor pressure changes were observed simultaneously on three APGs located over the transition from the active prism to the continental basement and show polarity changes over short distances, suggesting a shallow source. Their duration of several hours to days is shorter than most geodetic transients observed using onshore GPS networks. The results demonstrate the need for densely spaced and large-aperture OBS networks equipped with APGs for understanding subduction zone behavior.

The Alaska Amphibious Community Seismic Experiment

2020 ◽  
Vol 91 (6) ◽  
pp. 3054-3063 ◽  
Author(s):  
Grace Barcheck ◽  
Geoffrey A. Abers ◽  
Aubreya N. Adams ◽  
Anne Bécel ◽  
John Collins ◽  
...  
Keyword(s):  
Strong Motion ◽  
Seismic Survey ◽  
Absolute Pressure ◽  
Ocean Bottom ◽  
Ocean Bottom Seismometer ◽  
Alaska Peninsula ◽  
Outer Rise ◽  
Kodiak Island ◽  
Active Source ◽  
Seismic Experiment

Abstract The Alaska Amphibious Community Seismic Experiment (AACSE) is a shoreline-crossing passive- and active-source seismic experiment that took place from May 2018 through August 2019 along an ∼700  km long section of the Aleutian subduction zone spanning Kodiak Island and the Alaska Peninsula. The experiment featured 105 broadband seismometers; 30 were deployed onshore, and 75 were deployed offshore in Ocean Bottom Seismometer (OBS) packages. Additional strong-motion instruments were also deployed at six onshore seismic sites. Offshore OBS stretched from the outer rise across the trench to the shelf. OBSs in shallow water (<262  m depth) were deployed with a trawl-resistant shield, and deeper OBSs were unshielded. Additionally, a number of OBS-mounted strong-motion instruments, differential and absolute pressure gauges, hydrophones, and temperature and salinity sensors were deployed. OBSs were deployed on two cruises of the R/V Sikuliaq in May and July 2018 and retrieved on two cruises aboard the R/V Sikuliaq and R/V Langseth in August–September 2019. A complementary 398-instrument nodal seismometer array was deployed on Kodiak Island for four weeks in May–June 2019, and an active-source seismic survey on the R/V Langseth was arranged in June 2019 to shoot into the AACSE broadband network and the nodes. Additional underway data from cruises include seafloor bathymetry and sub-bottom profiles, with extra data collected near the rupture zone of the 2018 Mw 7.9 offshore-Kodiak earthquake. The AACSE network was deployed simultaneously with the EarthScope Transportable Array (TA) in Alaska, effectively densifying and extending the TA offshore in the region of the Alaska Peninsula. AACSE is a community experiment, and all data were made available publicly as soon as feasible in appropriate repositories.

scholarly journals Geologic controls on up-dip and along-strike propagation of slip during subduction zone earthquakes from a high-resolution seismic reflection survey across the northern limit of slip during the 2010 Mw 8.8 Maule earthquake, offshore Chile

Geosphere ◽  
2019 ◽  
Vol 15 (6) ◽  
pp. 1751-1773 ◽  
Author(s):  
Anne M. Tréhu ◽  
Bridget Hass ◽  
Alexander de Moor ◽  
Andrei Maksymowicz ◽  
Eduardo Contreras-Reyes ◽  
...  
Keyword(s):  
High Resolution ◽  
Subduction Zone ◽  
Seismic Reflection ◽  
Plate Boundary ◽  
Accretionary Prism ◽  
Structural Heterogeneity ◽  
Deformation Front ◽  
Maule Earthquake ◽  
Subduction Zone Earthquakes ◽  
Trench Sediments

Abstract A grid of closely spaced, high-resolution multichannel seismic (MCS) reflection profiles was acquired in May 2012 over the outer accretionary prism up dip from the patch of greatest slip during the 2010 Mw 8.8 Maule earthquake (offshore Chile) to complement a natural-source seismic experiment designed to monitor the post-earthquake response of the outer accretionary prism. We describe the MCS data and discuss the implications for the response of the accretionary prism during the earthquake and for the long-term evolution of the margin. The most notable observation from the seismic reflection survey is a rapid north-to-south shift over a short distance from nearly total frontal accretion of the trench sediments to nearly total underthrusting of undeformed trench sediments that occurs near the northern edge of slip in the 2010 earthquake. Integrating our structural observations with other geological and geophysical observations, we conclude that sediment subduction beneath a shallow décollement is associated with propagation of slip to the trench during great earthquakes in this region. The lack of resolvable compressive deformation in the trench sediment along this segment of the margin indicates that the plate boundary here is very weak, which allowed the outer prism to shift seaward during the earthquake, driven by large slip down dip. The abrupt shift from sediment subduction to frontal accretion indicates a stepdown in the plate boundary fault, similar to the stepovers that commonly arrest slip propagation in strike-slip faults. We do not detect any variation along strike in the thickness or reflective character of the trench sediments adjacent to the change in deformation front structure. This change, however, is correlated with variations in the morphology and structure of the accretionary prism that extend as far as 40 km landward of the deformation front. We speculate that forearc structural heterogeneity is the result of subduction of an anomalously shallow or rough portion of plate that interacted with and deformed the overlying plate and is now deeply buried. This study highlights need for three-dimensional structural images to understand the interaction between geology and slip during subduction zone earthquakes.

Comparison of the S/N ratios of low-frequency hydrophones and geophones as a function of ocean depth

1981 ◽  
Vol 71 (5) ◽  
pp. 1649-1659
Author(s):  
Thomas M. Brocher ◽  
Brian T. Iwatake ◽  
Joseph F. Gettrust ◽  
George H. Sutton ◽  
L. Neil Frazer
Keyword(s):  
Nova Scotia ◽  
Continental Margin ◽  
Low Frequency ◽  
Weather Conditions ◽  
Ocean Bottom ◽  
Ocean Bottom Seismometer ◽  
Scotian Shelf ◽  
Ocean Bottom Seismometers ◽  
Particle Velocities ◽  
Refraction Data

abstract The pressures and particle velocities of sediment-borne signals were recorded over a 9-day period by an array of telemetered ocean-bottom seismometers positioned on the continental margin off Nova Scotia. The telemetered ocean-bottom seismometer packages, which appear to have been very well coupled to the sediments, contained three orthogonal geophones and a hydrophone. The bandwidth of all sensors was 1 to 30 Hz. Analysis of the refraction data shows that the vertical geophones have the best S/N ratio for the sediment-borne signals at all recording depths (67, 140, and 1301 m) and nearly all ranges. The S/N ratio increases with increasing sensor depth for equivalent weather conditions. Stoneley and Love waves detected on the Scotian shelf (67-m depth) are efficient modes for the propagation of noise.

Low-frequency sound interaction with a sloping, refracting ocean bottom

1988 ◽  
Vol 13 (4) ◽  
pp. 235-244 ◽  
Author(s):  
M.D. Collins ◽  
H.B. Ali ◽  
M.J. Authement ◽  
A. Nagl ◽  
H. Uberall ◽  
...  
Keyword(s):  
Low Frequency ◽  
Ocean Bottom ◽  
Frequency Sound

A comparative fluid flow characterisation in a low frequency/high power sonoreactor and mechanical stirred vessel

2015 ◽  
Vol 27 ◽  
pp. 359-373 ◽  
Author(s):  
Baharak Sajjadi ◽  
Abdul Aziz Abdul Raman ◽  
Shaliza Ibrahim
Keyword(s):  
Fluid Flow ◽  
High Power ◽  
Low Frequency ◽  
Stirred Vessel

A study of the effects of ocean bottom roughness on low‐frequency sound propagation

1979 ◽  
Vol 65 (2) ◽  
pp. 381-386
Author(s):  
Steven R. Rutherford ◽  
Kenneth E. Hawker ◽  
Susan G. Payne
Keyword(s):  
Sound Propagation ◽  
Low Frequency ◽  
Ocean Bottom ◽  
Frequency Sound

Investigation of Low Frequency Elastic Wave Application for Fluid Flow Percolation Enhancement in Fractured Porous Media

2013 ◽  
Vol 31 (11) ◽  
pp. 1159-1167 ◽  
Author(s):  
B. Keshavarzi ◽  
R. Karimi ◽  
I. Najafi ◽  
M. H. Ghazanfari ◽  
M. Amani ◽  
...  
Keyword(s):  
Porous Media ◽  
Fluid Flow ◽  
Elastic Wave ◽  
Low Frequency ◽  
Fractured Porous Media
Sign in / Sign up

Export Citation Format

Share Document