scholarly journals Earth's free oscillations recorded by free-fall OBS ocean-bottom seismometers at the Lesser Antilles subduction zone

2011 ◽  
Vol 38 (24) ◽  
pp. n/a-n/a ◽  
Author(s):  
A. Bécel ◽  
M. Laigle ◽  
J. Diaz ◽  
J.-P. Montagner ◽  
A. Hirn
Keyword(s):  
Subduction Zone ◽  
Free Fall ◽  
Lesser Antilles ◽  
Ocean Bottom ◽  
Free Oscillations ◽  
Ocean Bottom Seismometers ◽  
Earth’S Free Oscillations

scholarly journals First Observation of the Earth's Permanent Free Oscillations on Ocean Bottom Seismometers

2017 ◽  
Vol 44 (21) ◽  
Author(s):  
M. Deen ◽  
E. Wielandt ◽  
E. Stutzmann ◽  
W. Crawford ◽  
G. Barruol ◽  
...  
Keyword(s):  
Ocean Bottom ◽  
Free Oscillations ◽  
Ocean Bottom Seismometers

scholarly journals Observations of Earth’s Normal Modes on Broadband Ocean Bottom Seismometers

2021 ◽  
Vol 9 ◽  
Author(s):  
Gabi Laske
Keyword(s):  
Normal Modes ◽  
Low Frequency ◽  
Free Fall ◽  
Ocean Bottom ◽  
High Quality ◽  
Broadband Seismometer ◽  
The Pacific ◽  
Ocean Bottom Seismometers ◽  
The Pacific Ocean ◽  
First Time

It is generally thought that high noise levels in the oceans inhibit the observation of long-period earthquake signals such as Earth’s normal modes on ocean bottom seismometers (OBSs). Here, we document the observation of Earth’s gravest modes at periods longer than 500 s (or frequencies below 2 mHz). We start with our own 2005–2007 Plume-Lithosphere-Undersea-Mantle Experiment (PLUME) near Hawaii that deployed a large number of broadband OBSs for the first time. We collected high-quality normal mode spectra for the great November 15, 2006 Kuril Islands earthquake on multiple OBSs. The random deployment of instruments from different OBS groups allows a direct comparison between different broadband seismometers. For this event, mode S06 (1.038 mHz) consistently rises above the background noise at all OBSs that had a Nanometrics Trillium T-240 broadband seismometer. We also report observations of other deployments in the Pacific ocean that involved instruments of the U.S. OBS Instrument Pool (OBSIP) where we observe even mode S04 (0.647 mHz). Earth’s normal modes were never the initial target of any OBS deployment, nor was any other ultra-low-frequency signal. However, given the high costs of an OBS campaign, the fact that data are openly available to future investigators not involved in the campaign, and the fact that seismology is evolving to investigate ever-new signals, this paper makes the case that the investment in a high-quality seismic sensor may be a wise one, even for a free-fall OBS.

scholarly journals Along‐Arc Heterogeneity in Local Seismicity across the Lesser Antilles Subduction Zone from a Dense Ocean‐Bottom Seismometer Network

2019 ◽  
Vol 91 (1) ◽  
pp. 237-247 ◽  
Author(s):  
Lidong Bie ◽  
Andreas Rietbrock ◽  
Stephen Hicks ◽  
Robert Allen ◽  
Jon Blundy ◽  
...  
Keyword(s):  
Subduction Zone ◽  
Subduction Zones ◽  
Lesser Antilles ◽  
Seismogenic Zone ◽  
Ocean Bottom ◽  
Ocean Bottom Seismometer ◽  
Plate Interface ◽  
Local Seismicity ◽  
Slow Spreading ◽  
Lesser Antilles Arc

Abstract The Lesser Antilles arc is only one of two subduction zones where slow‐spreading Atlantic lithosphere is consumed. Slow‐spreading may result in the Atlantic lithosphere being more pervasively and heterogeneously hydrated than fast‐spreading Pacific lithosphere, thus affecting the flux of fluids into the deep mantle. Understanding the distribution of seismicity can help unravel the effect of fluids on geodynamic and seismogenic processes. However, a detailed view of local seismicity across the whole Lesser Antilles subduction zone is lacking. Using a temporary ocean‐bottom seismic network we invert for hypocenters and 1D velocity model. A systematic search yields a 27 km thick crust, reflecting average arc and back‐arc structures. We find abundant intraslab seismicity beneath Martinique and Dominica, which may relate to the subducted Marathon and/or Mercurius Fracture Zones. Pervasive seismicity in the cold mantle wedge corner and thrust seismicity deep on the subducting plate interface suggest an unusually wide megathrust seismogenic zone reaching ∼65  km depth. Our results provide an excellent framework for future understanding of regional seismic hazard in eastern Caribbean and the volatile cycling beneath the Lesser Antilles arc.

Migration-Based Local Event-Location Workflow for Ocean-Bottom Seismometer (OBS) Records in Subduction Zones: A Practical Approach for Addressing a Large Number of Events

2021 ◽  
Author(s):  
Shinji Yoneshima ◽  
Kimihiro Mochizuki
Keyword(s):  
Subduction Zone ◽  
Subduction Zones ◽  
Real Data ◽  
Japan Trench ◽  
Ocean Bottom ◽  
Ocean Bottom Seismometer ◽  
S Waves ◽  
Local Earthquakes ◽  
Ocean Bottom Seismometers ◽  
Event Location

ABSTRACT An efficient event-location workflow is highly desired to analyze large numbers of local earthquakes recorded by ocean-bottom seismometers (OBSs) in subduction zones. The present study proposes a migration-based event-location approach for evaluating OBS records to examine local subduction-zone earthquakes. This approach can significantly reduce the amount of manual time picks compared with conventional methods. The event-location workflow was designed to detect arrival onsets of both P and S phases. Synthetic tests have shown that the proposed migration-based event-location method is robust against different types of noise, such as environmental noise and local spike noise. This workflow was then applied to real OBS data in the off-Ibaraki region at the southern end of the Japan trench. The results show that this approach is applicable to real data from subduction-zone events: It gives reasonable agreement with manual time picks for both P and S waves and reasonable error bars, and it demonstrates a clear down-dip trend of seismicity. The results also show fair agreement with event distributions from previous studies of the off-Ibaraki region. This proposed workflow can be used to examine the seismicity of local earthquakes around the subduction zone using OBSs. This approach is especially effective when the seismicity is high and/or in cases in which long-term OBS monitoring has recorded a large number of events.

A microprocessor-based ocean-bottom seismometer

1993 ◽  
Vol 83 (1) ◽  
pp. 190-217 ◽  
Author(s):  
David F. Willoughby ◽  
John A. Orcutt ◽  
David Horwitt
Keyword(s):  
Free Fall ◽  
Acoustic Signals ◽  
Differential Pressure ◽  
Ocean Bottom ◽  
Ocean Bottom Seismometer ◽  
Serial Links ◽  
Natural Period ◽  
Scripps Institution ◽  
Ocean Bottom Seismometers ◽  
Spherical Pressure

Abstract For over 12 years, the Scripps Institution of Oceanography has operated a fleet of microprocessor-based ocean-bottom seismometers. These instruments free-fall to the seafloor and release their anchors and rise to the surface either at preset times or on receipt of an acoustic command. The instruments are contained in a single spherical pressure case and include geophones with a 1-Hz natural period, and differential pressure gauges responsive to acoustic signals between 0.003 and 30 Hz. Recent improvements described in detail here include the implementation of a C-44 bus 80C88 microprocessor and cassette recorders capable of storing up to 10 days of data digitized at 128 samples/sec, or 40 days at 32 samples/sec. In addition, tiltmeters have been installed in the instruments. Serial links to the processor and release timers provide for instrument checkout and the setting of time and data parameters from outside the pressure case. A portable laboratory also described here is used to prepare the instruments for deployment at sea.

scholarly journals Comparison of fluid tiltmeter data with long-period seismograms: Surface waves and Earth's free oscillations

2006 ◽  
Vol 111 (B11) ◽  
pp. n/a-n/a ◽  
Author(s):  
A. M. G. Ferreira ◽  
N. F. d'Oreye ◽  
J. H. Woodhouse ◽  
W. Zürn
Keyword(s):  
Surface Waves ◽  
Free Oscillations ◽  
Long Period ◽  
Earth’S Free Oscillations

scholarly journals Microearthquake seismicity and focal mechanisms at the Rodriguez Triple Junction in the Indian Ocean using ocean bottom seismometers

2001 ◽  
Vol 106 (B12) ◽  
pp. 30689-30699 ◽  
Author(s):  
Kei Katsumata ◽  
Toshinori Sato ◽  
Junzo Kasahara ◽  
Naoshi Hirata ◽  
Ryota Hino ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Triple Junction ◽  
Focal Mechanisms ◽  
Ocean Bottom ◽  
Ocean Bottom Seismometers ◽  
The Indian Ocean

The Seismotectonics and Seismicity of the Laptev Sea Region: The Current Situation and a First Experience in a Year-Long Installation of Ocean Bottom Seismometers on the Shelf

2020 ◽  
Vol 14 (6) ◽  
pp. 379-393
Author(s):  
A. A. Krylov ◽  
A. I. Ivashchenko ◽  
S. A. Kovachev ◽  
N. V. Tsukanov ◽  
M. E. Kulikov ◽  
...  
Keyword(s):  
Current Situation ◽  
Laptev Sea ◽  
Ocean Bottom ◽  
Ocean Bottom Seismometers ◽  
The Laptev Sea
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