Passive seismic reflectivity imaging with ocean‐bottom cable data

2006 ◽  
Author(s):  
Detlef Hohl ◽  
Albena Mateeva
Keyword(s):  
Ocean Bottom ◽  
Passive Seismic ◽  
Seismic Reflectivity ◽  
Reflectivity Imaging

scholarly journals Seismicity cluster below the Moho indicates thrust faulting in the central Ligurian Basin

2020 ◽  
Author(s):  
Martin Thorwart ◽  
Anke Dannowski ◽  
Heidrun Kopp ◽  
Dietrich Lange ◽  
Wayne Crawford ◽  
...  
Keyword(s):  
Ocean Bottom ◽  
Tyrrhenian Sea ◽  
Seismic Profiles ◽  
Ligurian Sea ◽  
Thrust Faulting ◽  
Research Initiative ◽  
Passive Seismic ◽  
Long Term Experiment ◽  
Back Arc ◽  
Ligurian Basin

<p><span>The Alpine orogen and the Apennines system </span><span>are</span><span> part of the complex tectonic settings in the Mediterranean Sea caused by the convergence between Africa and Eurasia. Between 30 Ma and 15 Ma, the Calabrian Subduction retreated in southeast direction pulling Corsica and Sardinia away from the Eurasian continent. In this extensional setting, the Ligurian Sea was formed as a back-arc basin. The rifting jumped 15 MA ago </span><span>to</span><span> the Tyrrhenian Sea leaving Corsica and Sardinia in a stable position relative to Eurasia </span><span>as observed by GPS measurements.</span></p><p><span>Within the framework of the AlpArray research initiative and its German component “4D Mountain building” (SPP2017 4D-MB) a long-term experiment was conducted in the Ligurian sea to investigate the lithosphere structure and the seismicity in the Ligurian basin. The passive seismic network </span><span>was operated by France and Germany and </span><span>consisted of 29 br</span><span>oad-band ocean bottom stations. It was in operation between June 2017 and February 2018. At the end of the experiment </span><span>two</span><span> active seismic profiles were conducted additionally.</span></p><p><span>A cluster of 15 events with </span><span>m</span><span>agnitudes lower than 2.5 occurred in the centre of the Ligurian Basin. The earthquakes are located at a </span><span>depth </span><span>of 20 km to 35 km, i.e. </span><span>10 - 25 km below the Moho.</span><span> The cluster was not continuously active but had several active periods </span><span>which</span><span> lasted between 2 and 5 days.</span></p><p><span>A f</span><span>ault plane solution could be determined of the larger events in the cluster. The mechanism is a thrust faulting. </span><span>S</span><span>maller events </span><span>should have a similar mechanism</span> <span>due to the highly</span> <span>coherent </span><span>waveforms. </span><span>A</span> <span>similar </span><span>mechanism </span><span>was </span><span>observed for the Mw=4.9 earthquake on 07.07.2011 which occurred 50 km east of the cluster. Both solutions show a SW-NE striking, northwest dipping fault plane. </span><span>This indicates a convergence in NW-SE direction between Corsica and Eurasia.</span></p>

Passive seismic interferometry of the ultraslow-spreading Southwest Indian Ridge 

2021 ◽  
Author(s):  
Mohamadhasan Mohamadian Sarvandani ◽  
Emanuel Kästle ◽  
Lapo Boschi ◽  
Sylvie Leroy ◽  
Mathilde Cannat
Keyword(s):  
Wave Velocity ◽  
Vertical Component ◽  
Velocity Model ◽  
Southwest Indian Ridge ◽  
Seismic Interferometry ◽  
Ocean Bottom ◽  
S Wave ◽  
Passive Seismic ◽  
Indian Ridge ◽  
Marine Exploration

<p>Passive seismic interferometry (ambient-noise seismology) is an increasingly popular, eco-friendly, relatively inexpensive exploration geophysics tool, to map S-wave velocity in the Earth’s crust. This method has not yet been applied widely to marine exploration. The purpose of this study is to investigate the crustal structure of a quasi-amagmatic portion of the Southwest Indian Ridge by interferometry, and to examine the performance and reliability of interferometry in marine exploration. To achieve this goal, continuous vertical-component recordings from 43 ocean bottom seismometers (OBS) deployed during the SISMO-SMOOTH cruise (2014) were utilized. Recorded signals span frequencies between 0.1Hz and 3Hz. We show that reliable estimates of the Green’s function are obtained for many station pairs, by cross-correlation in the frequency domain. The comparison of the cross-correlations with the theoretical Green’s (Bessel) function provides one Rayleigh-wave dispersion curve per station pair; dispersion curves are then averaged, and inverted through a conditional neighborhood algorithm to determine a 1D S-wave velocity model, that we estimate to be well constrained within the crust. Our S-wave velocity model is analyzed and interpreted with geological information, and independent geophysical studies in the region of interest, as well as other areas characterized by similar tectonically-dominated, quasi amagmatic spreadings.</p>

BIO-OCEANOGRAPHER, ZOOLOGIST LEV IVANOVICH MOSKALEV (04.01.1935–04.12.2020)

2020 ◽  
Vol 48 (4) ◽  
pp. 168-171
Author(s):  
E. M. Krylova ◽  
A. N. Mironov ◽  
A. V. Gebruk
Keyword(s):  
Deep Sea ◽  
Bottom Fauna ◽  
Ocean Bottom ◽  
Scientific Career ◽  
Shirshov Institute ◽  
Popular Book ◽  
Scientific Papers

The article is dedicated to the memory of L.I. Moskalev – renowned bio-oceanographer, zoologist who spent his entire scientific career at the Laboratory of Ocean Bottom Fauna. L.I. Moskalev participated in more than 30 deep-sea voyages, spent 200 hours diving in manned submersibles “Pisces” and “Mir”, published about 100 scientific papers and a popular book «Masters of the Deep» (2005). Colleagues will remember Lev Moskalev – an extraordinary and deep person and a true patriot of the Laboratory and P.P. Shirshov Institute of Oceanology

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