Nature of the Ambient Noise, Site Response, and Orientation of Ocean‐Bottom Seismometers (OBSs): Scientific Results of a Passive Seismic Experiment in the Andaman Sea

2017 ◽  
Vol 108 (1) ◽  
pp. 248-259 ◽  
Author(s):  
Pawan Dewangan ◽  
Ramakrushana Reddy ◽  
K. A. Kamesh Raju ◽  
Pabitra Singha ◽  
K. K. Aswini ◽  
...  
Keyword(s):  
Ambient Noise ◽  
Site Response ◽  
Andaman Sea ◽  
Ocean Bottom ◽  
Seismic Experiment ◽  
Ocean Bottom Seismometers ◽  
Passive Seismic ◽  
Scientific Results ◽  
Passive Seismic Experiment

scholarly journals Moment magnitude estimates for Central Anatolian earthquakes using coda waves

2019 ◽  
Author(s):  
Tuna Eken
Keyword(s):  
Empirical Relation ◽  
Active Regions ◽  
Moment Magnitude ◽  
Central Anatolia ◽  
Coda Wave ◽  
Seismic Experiment ◽  
Tectonically Active ◽  
Passive Seismic ◽  
Passive Seismic Experiment ◽  
Good Agreement

Abstract. Proper estimate of moment magnitude that is a physical measure of the energy released at earthquake source is essential for better seismic hazard assessments in tectonically active regions. Here a coda wave modeling approach that enables the source displacement spectrum modeling of examined event was used to estimate moment magnitude of central Anatolia earthquakes. To achieve this aim, three component waveforms of local earthquakes with magnitudes 2.0 ≤ ML ≤ 5.2 recorded at 72 seismic stations which have been operated between 2013 and 2015 within the framework of the CD-CAT passive seismic experiment. An inversion on the coda wave traces of each selected single event in our database was performed in five different frequency bands between 0.75 and 12 Hz. Our resultant moment magnitudes (MW-coda) exhibit a good agreement with routinely reported local magnitude (ML) estimates for study area. Finally, we present an empirical relation between MW-coda and ML for central Anatolian earthquakes.

scholarly journals Seismic attenuation from recordings of ambient noise

Geophysics ◽  
2013 ◽  
Vol 78 (1) ◽  
pp. Q1-Q14 ◽  
Author(s):  
Cornelis Weemstra ◽  
Lapo Boschi ◽  
Alexander Goertz ◽  
Brad Artman
Keyword(s):  
Surface Waves ◽  
Bessel Function ◽  
Acoustic Waves ◽  
Ambient Noise ◽  
Sea Water ◽  
Seismic Attenuation ◽  
Ocean Bottom ◽  
Quality Factors ◽  
Ocean Bottom Seismometers ◽  
Additional Loss

We applied seismic interferometry to data from an ocean-bottom survey offshore Norway and found that ambient seismic noise can be used to constrain subsurface attenuation on a reservoir scale. By crosscorrelating only a few days of recordings by broadband ocean bottom seismometers, we were able to retrieve empirical Green’s functions associated with surface waves in the frequency range between 0.2 and 0.6 Hz and acoustic waves traveling through the sea water between 1.0 and 2.5 Hz. We discovered that the decay of these surface waves cannot be explained by geometrical spreading alone and required an additional loss of energy with distance. We quantified this observed attenuation in the frequency domain using a modified Bessel function to describe the cross-spectrum in a stationary field. We averaged cross-spectra of equally spaced station couples and sorted these azimuthally averaged cross-spectra with distance. We then obtained frequency-dependent estimates of attenuation by minimizing the misfit of the real parts to a damped Bessel function. The resulting quality factors as function of frequency are indicative of the depth variation of attenuation and correlated with the geology in the survey area.

Stability of ambient noise H/V spectra obtained from OBS near the Japan Trench

2020 ◽  
Author(s):  
Atikul Haque Farazi ◽  
Emmanuel Soliman M. Garcia ◽  
Yoshihiro Ito
Keyword(s):  
Ambient Noise ◽  
Temporal Stability ◽  
Spectral Ratio ◽  
Japan Trench ◽  
Future Application ◽  
Ocean Bottom ◽  
S Wave ◽  
Slow Earthquakes ◽  
Short Period ◽  
Ocean Bottom Seismometers

<p>Ocean bottom seismometers (OBS) are widely in use since recent past to monitor seismicity of slow earthquakes as well as that of ordinary earthquakes. Seismic velocity structures, especially of S-wave are essential to estimate hypocenters of them with accuracy. Here we focus on spatial and temporal stability of ambient noise horizontal to vertical spectral ratio (H/V) spectra calculated from ocean bottom seismometers, as the first step toward future application of ambient noise H/V to estimate S-wave velocity structure. We aim to use the Nakamura’s method (1989) for ambient noise H/V spectra using a 3-component OBS array in the Japan Trench, to image deep structure above the plate interface near the trench. To achieve the imaging, it is necessary to examine spatial and temporal stability of the derived H/V spectra from these seismometers. First, we split each 24-hours record into 1-hour windows after removing the instrumental response, Then, Fourier amplitude spectra of each component is taken and smoothed using Konno and Ohmachi (1998) method, with applying downsampling, mean and trend removal, and tapering to each window. Finally, a 1-hour H/V spectral ratio is calculated with taking quadratic mean of two horizontal components. However, a total of 21 OBS, 3 broadband and 18 short-period, stations have been used in this study. A daily variation and stability of the H/V spectra are examined along with comparing them spatially from one station to another. Stability of the H/V spectra from OBS is promising for carrying out our future endevour of deeper observation using the ambient noise H/V method.</p>

scholarly journals Passive seismic experiment and ScS wave splitting in the southwestern subbasin of South China Sea

2012 ◽  
Vol 57 (25) ◽  
pp. 3381-3390 ◽  
Author(s):  
AiGuo Ruan ◽  
JiaBiao Li ◽  
ChaoShing Lee ◽  
XueLin Qiu ◽  
ShaoJun Pan
Keyword(s):  
South China Sea ◽  
South China ◽  
China Sea ◽  
Seismic Experiment ◽  
Wave Splitting ◽  
Passive Seismic ◽  
Passive Seismic Experiment
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