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 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

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.

scholarly journals The GITEWS ocean bottom sensor packages

2010 ◽  
Vol 10 (8) ◽  
pp. 1759-1780
Author(s):  
O. Boebel ◽  
M. Busack ◽  
E. R. Flueh ◽  
V. Gouretski ◽  
H. Rohr ◽  
...  
Keyword(s):  
Warning System ◽  
Deep Ocean ◽  
Indian Ocean Tsunami ◽  
False Alarms ◽  
Ocean Bottom ◽  
Bottom Pressure ◽  
Tsunami Early Warning ◽  
Ocean Bottom Seismometers ◽  
First Results ◽  
Sensor Package

Abstract. The German-Indonesian Tsunami Early Warning System (GITEWS) aims at reducing the risks posed by events such as the 26 December 2004 Indian Ocean tsunami. To minimize the lead time for tsunami alerts, to avoid false alarms, and to accurately predict tsunami wave heights, real-time observations of ocean bottom pressure from the deep ocean are required. As part of the GITEWS infrastructure, the parallel development of two ocean bottom sensor packages, PACT (Pressure based Acoustically Coupled Tsunameter) and OBU (Ocean Bottom Unit), was initiated. The sensor package requirements included bidirectional acoustic links between the bottom sensor packages and the hosting surface buoys, which are moored nearby. Furthermore, compatibility between these sensor systems and the overall GITEWS data-flow structure and command hierarchy was mandatory. While PACT aims at providing highly reliable, long term bottom pressure data only, OBU is based on ocean bottom seismometers to concurrently record sea-floor motion, necessitating highest data rates. This paper presents the technical design of PACT, OBU and the HydroAcoustic Modem (HAM.node) which is used by both systems, along with first results from instrument deployments off Indonesia.

Tidal Triggering of the Harmonic Noise in Ocean-Bottom Seismometers

2020 ◽  
Vol 91 (2A) ◽  
pp. 803-813 ◽  
Author(s):  
Telluri Ramakrushana Reddy ◽  
Pawan Dewangan ◽  
Lalit Arya ◽  
Pabitra Singha ◽  
Kattoju Achuta Kamesh Raju
Keyword(s):  
Spectral Analysis ◽  
Fundamental Frequency ◽  
Ocean Bottom ◽  
Automated Algorithm ◽  
Tidal Triggering ◽  
Spectral Peaks ◽  
Ocean Bottom Seismometers ◽  
Oceanic Tides ◽  
Harmonic Noise

Abstract We observed a harmonic noise (HN) in DEutscher Geräte-Pool für Amphibische Seismologie ocean-bottom seismometers (OBSs) data recorded from the Andaman–Nicobar region. The HN is characterized by sharp spectral peaks with a fundamental frequency and several overtones occurring at integer multiples of the fundamental frequency. We used an automated algorithm to quantify the occurrence of HN for the entire four-month deployment period (1 January 2014 to 30 April 2014). The algorithm detected more than 23 days of HN for some OBS stations. The spectral analysis of the hourly count of HN shows distinct lunar and solar tidal periodicities at 4.14, 6.1, 6.22, 12, and 12.4 hr as well as 13.66 days. The observed periodicities provide evidence of tidal triggering of HN. The HN is generated by the strumming of head buoys due to seafloor currents initiated by oceanic tides in the Andaman–Nicobar region.

scholarly journals Seismic Characteristics of the Nootka Fault Zone: Results from the Seafloor Earthquake Array Japan–Canada Cascadia Experiment (SeaJade)

2019 ◽  
Vol 109 (6) ◽  
pp. 2252-2276 ◽  
Author(s):  
Jesse Hutchinson ◽  
Honn Kao ◽  
George Spence ◽  
Koichiro Obana ◽  
Kelin Wang ◽  
...  
Keyword(s):  
Sea Level ◽  
Fault Zone ◽  
Cascadia Subduction Zone ◽  
Ocean Bottom ◽  
Deformation Front ◽  
Thrust Faulting ◽  
Modes Of Failure ◽  
Ocean Bottom Seismometers ◽  
Thrust Zone ◽  
Depth Ranges

Abstract The Nootka fault zone (NFZ) divides the incoming Explorer and Juan de Fuca plates of the Cascadia subduction zone. Three months of seafloor monitoring using 33 ocean‐bottom seismometers off the west coast of Vancouver Island has allowed us to better understand the tectonic configuration and seismogenic characteristics of the NFZ. We have learned that the NFZ is comprised of northern and southern primary bounding faults, and several conjugate faults developed subperpendicular to the primary faults. Earthquakes typically occur over the depth ranges of 15–20 and 6–15 km along the primary bounding and conjugate faults, respectively. Focal mechanisms reveal that the most common modes of failure in this region are left‐lateral strike slip, with normal faulting occurring along the southwestern extent of the NFZ and thrust faulting to the northeast before the subduction front. Seismic tomography suggests that the oceanic Moho is at a depth of 12–14 km below sea level (10–12 km below seafloor) just seaward of the Cascadia deformation front, and that it deepens to 19 km (17 km below seafloor) approximately 20 km landward of the deformation front. Converted phase analysis illuminates four velocity‐contrasting interfaces with average depths below sea level deepening landward of the subduction front at ∼4–6, ∼6–9, ∼11–14, and ∼14–18  km. We interpret them as the sedimentary basement, upper–lower crust boundary, oceanic Moho, and the base of the highly fractured and seawater or mineral enriched veins within mantle. The precipitation of minerals such as quartz or the formation of talc, which is made possible by the intense degree of fracturing within the NFZ facilitating the infiltration of seawater, may reduce mantle velocities, as well as VP/VS ratios. The lack of seismicity observed along the interplate thrust zone in northern Cascadia may suggest that the megathrust fault is completely locked, consistent with prior studies.

scholarly journals Aftershock observation of the Noto Hanto earthquake in 2007 using ocean bottom seismometers

2008 ◽  
Vol 60 (10) ◽  
pp. 1005-1010 ◽  
Author(s):  
Tomoaki Yamada ◽  
Kimihiro Mochizuki ◽  
Masanao Shinohara ◽  
Toshihiko Kanazawa ◽  
Asako Kuwano ◽  
...  
Keyword(s):  
Ocean Bottom ◽  
Aftershock Observation ◽  
Noto Hanto Earthquake ◽  
Ocean Bottom Seismometers
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