An Efficient Approach of Data Adaptive Polarization Filter to Extract Teleseismic Phases from the Ocean-Bottom Seismograms

2020 ◽  
Vol 92 (1) ◽  
pp. 528-542
Author(s):  
Sanjay S. Negi ◽  
Amit Kumar ◽  
Lachit S. Ningthoujam ◽  
Dhananjai K. Pandey
Keyword(s):  
Seismic Noise ◽  
Signal To Noise Ratio ◽  
Phase Identification ◽  
Ocean Bottom ◽  
Polarization Filter ◽  
Software Suite ◽  
Mantle Dynamics ◽  
The Indian Ocean ◽  
Data Adaptive ◽  
Ocean Bottom Seismographs

Abstract The microseism is the strongest component of background seismic noise that masks seismic signals recorded by ocean-bottom seismographs (OBSs). Such undesired noise hampers the identification of critical seismic phases and sometimes even the entire waveform. Here, we introduce the data adaptive polarization filter (DAPF), an approach that suppresses random signals from the background seismic-noise significantly to overcome such difficulties. To automate this task, we have developed a self-contained software suite—DAPF-v1, supported by a MATLAB graphical user interface. The polarization filter is constructed from the data spectral density matrices of seismogram segments employing multitaper spectral analysis approach. We demonstrate a successful application of this technique to the OBSs deployed in the Indian Ocean. Our results confirm substantially enhanced signal-to-noise ratio after application of DAPF. The application of this technique has extensive implications for seismological studies particularly those aimed at understanding deep mantle dynamics, in which phase identification and qualitative waveform recovery are crucial yet challenging.

Queen Charlotte fault zone: microearthquakes from a temporary array of land stations and ocean bottom seismographs

1981 ◽  
Vol 18 (4) ◽  
pp. 776-788 ◽  
Author(s):  
R. D. Hyndman ◽  
R. M. Ellis
Keyword(s):  
Fault Zone ◽  
Strike Slip ◽  
Ocean Bottom ◽  
Small Component ◽  
Queen Charlotte Islands ◽  
The North ◽  
Vertical Fault ◽  
Linear Sections ◽  
Ocean Bottom Seismographs ◽  
Steep Slopes

A temporary array of land and ocean bottom seismograph stations was used to accurately locate microearthquakes on the Queen Charlotte fault zone, which occurs along the continental margin of western Canada. The continental slope has two steep linear sections separated by a 25 km wide irregular terrace at a depth of 2 km. Eleven events were located with magnitudes from 0.5 to 2.0, 10 of them beneath the landward one of the two steep slopes, some 5 km off the coast of the southern Queen Charlotte Islands. No events were located beneath the seaward and deeper steep slope. The depths of seven of these events were constrained by the data to between 9 and 21 km with most near 20 km. The earthquake and other geophysical data are consistent with a near vertical fault zone having mainly strike-slip motion. A model including a small component of underthrusting in addition to strike-slip faulting is suggested to account for the some 15° difference between the relative motion of the North America and Pacific plates from plate tectonic models and the strike of the margin. One event was located about 50 km inland of the main active zone and probably occurred on the Sandspit fault. The rate of seismicity on the Queen Charlotte fault zone during the period of the survey was similar to that predicted by the recurrence relation for the region from the long-term earthquake record.

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

scholarly journals Ocean-Bottom Seismographs Based on Broadband MET Sensors: Architecture and Deployment Case Study in the Arctic

Sensors ◽  
2021 ◽  
Vol 21 (12) ◽  
pp. 3979
Author(s):  
Artem A. Krylov ◽  
Ivan V. Egorov ◽  
Sergey A. Kovachev ◽  
Dmitry A. Ilinskiy ◽  
Oleg Yu. Ganzha ◽  
...  
Keyword(s):  
Site Response ◽  
The Arctic ◽  
Laptev Sea ◽  
Ocean Bottom ◽  
Arctic Seas ◽  
Shirshov Institute ◽  
Study Results ◽  
Ocean Bottom Seismographs ◽  
The Laptev Sea

The Arctic seas are now of particular interest due to their prospects in terms of hydrocarbon extraction, development of marine transport routes, etc. Thus, various geohazards, including those related to seismicity, require detailed studies, especially by instrumental methods. This paper is devoted to the ocean-bottom seismographs (OBS) based on broadband molecular–electronic transfer (MET) sensors and a deployment case study in the Laptev Sea. The purpose of the study is to introduce the architecture of several modifications of OBS and to demonstrate their applicability in solving different tasks in the framework of seismic hazard assessment for the Arctic seas. To do this, we used the first results of several pilot deployments of the OBS developed by Shirshov Institute of Oceanology of the Russian Academy of Sciences (IO RAS) and IP Ilyinskiy A.D. in the Laptev Sea that took place in 2018–2020. We highlighted various seismological applications of OBS based on broadband MET sensors CME-4311 (60 s) and CME-4111 (120 s), including the analysis of ambient seismic noise, registering the signals of large remote earthquakes and weak local microearthquakes, and the instrumental approach of the site response assessment. The main characteristics of the broadband MET sensors and OBS architectures turned out to be suitable for obtaining high-quality OBS records under the Arctic conditions to solve seismological problems. In addition, the obtained case study results showed the prospects in a broader context, such as the possible influence of the seismotectonic factor on the bottom-up thawing of subsea permafrost and massive methane release, probably from decaying hydrates and deep geological sources. The described OBS will be actively used in further Arctic expeditions.

Turbidity Current in the Northern Suruga Bay Recorded by Ocean Bottom Seismographs after Passing Typhoon No. 24 in 2018

2021 ◽  
Vol 73 (0) ◽  
pp. 197-207
Author(s):  
Hisatoshi BABA ◽  
Nagisa NAKAO ◽  
Takahito NISHIMIYA ◽  
Masanao SHINOHARA ◽  
Shintaro ABE ◽  
...  
Keyword(s):  
Turbidity Current ◽  
Ocean Bottom ◽  
Suruga Bay ◽  
Ocean Bottom Seismographs

Characteristics of Low-Frequency Horizontal Noise of Ocean-Bottom Seismic Data

2021 ◽  
Author(s):  
Chao An ◽  
Chen Cai ◽  
Lei Zhou ◽  
Ting Yang
Keyword(s):  
Water Waves ◽  
Noise Source ◽  
Random Noise ◽  
Low Frequency ◽  
Ocean Bottom ◽  
Coherent Noise ◽  
Infragravity Waves ◽  
Low Frequencies ◽  
Bottom Currents ◽  
Ocean Bottom Seismographs

Abstract Horizontal records of ocean-bottom seismographs are usually noisy at low frequencies (< 0.1 Hz). The noise source is believed to be associated with ocean-bottom currents that may tilt the instrument. Currently horizontal records are mainly used to remove the coherent noise in vertical records, and there has been little literature that quantitatively discusses the mechanism and characteristics of low-frequency horizontal noise. In this article, we analyze in situ ocean-bottom measurements by rotating the data horizontally and evaluating the coherency between different channels. Results suggest that the horizontal noise consists of two components, random noise and principle noise whose direction barely changes in time. The amplitude and the direction of the latter are possibly related to the intensity and direction of ocean-bottom currents. Rotating the horizontal records to the direction of the principle noise can largely suppress the principle noise in the orthogonal horizontal channel. In addition, the horizontal noise is incoherent with pressure, indicating that the noise source is not ocean surface water waves (infragravity waves). At some stations in shallow waters (<300 m), horizontal noise around 0.07 Hz is found to be linearly proportional to the temporal derivative of pressure, which is explained by forces of added mass due to infragravity waves.

T Waves Associated with Submarine Volcanic Eruptions in the Marianas Observed by Ocean Bottom Seismographs.

1993 ◽  
Vol 41 (2) ◽  
pp. 57-74 ◽  
Author(s):  
Hitoshi Yamasato ◽  
Nobuo Hamada ◽  
Charles S. McCreery ◽  
Firmin J. Oliveira ◽  
Daniel A. Walker ◽  
...  
Keyword(s):  
Volcanic Eruptions ◽  
Ocean Bottom ◽  
Ocean Bottom Seismographs ◽  
T Waves

Towards upgraded capability in offshore seismic studies with the new National Australian Pool of Ocean Bottom Seismographs

2013 ◽  
Vol 53 (2) ◽  
pp. 482
Author(s):  
Alexey Goncharov ◽  
Nicholas Rawlinson ◽  
Bruce Goleby
Keyword(s):  
Natural Hazard ◽  
Ocean Bottom ◽  
Data Set ◽  
Multi Scale ◽  
Refraction Seismic ◽  
Short And Long Term ◽  
Ocean Bottom Seismographs ◽  
Obs Data ◽  
First Time

In 2013, Australia, for the first time in its history, will obtain a national pool of ocean-bottom seismographs (OBSs) suitable for multi-scale experiments at sea and for onshore-offshore combined observations. Twenty broadband OBS instruments will be purchased for short- and long-term deployment (up to 12 months) to a maximum depth of 6 km. The instruments will be made available to Australian researchers through ANSIR, with only the costs of mobilisation and deployment to be met. It is anticipated that the OBS facility will greatly enhance the research capabilities of Australian scientists in the area of Earth imaging, offshore exploration, and natural hazard assessment. OBS experiments in Australia have been limited so far, with the only data set collected by Geoscience Australia in 1995–96 on a number of coincident reflection/refraction seismic transects across the northwestern Australian Margin. The main findings from that experiment will be reviewed in the context of recent OBS data processing and acquisition advances. The scope of the experiments with the new national Australian pool of OBSs will be presented, as well as practicalities and logistics of the OBS experiments.

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