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

Travel-time residuals of teleseismic P-waves at the Rodriguez Triple Junction in the Indian Ocean using ocean-bottom seismometers

1996 ◽  
Vol 23 (7) ◽  
pp. 713-716 ◽  
Author(s):  
Toshinori Sato ◽  
Kei Katsumata ◽  
Junzo Kasahara ◽  
Naoshi Hirata ◽  
Ryota Hino ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Travel Time ◽  
Triple Junction ◽  
Ocean Bottom ◽  
P Waves ◽  
Ocean Bottom Seismometers ◽  
The Indian Ocean

Segmentation of the Central Indian Ridge between 12°12′ S and the Indian Ocean Triple Junction

1993 ◽  
Vol 15 (4) ◽  
pp. 265-282 ◽  
Author(s):  
Lindsay M. Parson ◽  
Philippe Patriat ◽  
Roger C. Searle ◽  
Anne R. Briais
Keyword(s):  
Indian Ocean ◽  
Triple Junction ◽  
Central Indian Ridge ◽  
The Indian Ocean ◽  
Indian Ridge

scholarly journals Eocene to recent development of the South-west Indian Ridge, a consequence of the evolution of the Indian Ocean Triple Junction

1981 ◽  
Vol 64 (3) ◽  
pp. 587-604 ◽  
Author(s):  
John G. Sclater ◽  
Robert L. Fisher ◽  
Phillippe Patriat ◽  
Christopher Tapscott ◽  
Barry Parsons
Keyword(s):  
Indian Ocean ◽  
Triple Junction ◽  
West Indian ◽  
The South ◽  
South West ◽  
The Indian Ocean ◽  
Indian Ridge

scholarly journals Tomography of crust and lithosphere in the western Indian Ocean from noise cross-correlations of land and ocean bottom seismometers

2019 ◽  
Vol 219 (2) ◽  
pp. 924-944 ◽  
Author(s):  
Sarah Hable ◽  
Karin Sigloch ◽  
Eléonore Stutzmann ◽  
Sergey Kiselev ◽  
Guilhem Barruol
Keyword(s):  
Indian Ocean ◽  
Group Velocity ◽  
Western Indian Ocean ◽  
Spreading Ridge ◽  
Ocean Bottom ◽  
Depth Range ◽  
La Réunion ◽  
Velocity Measurements ◽  
Ocean Bottom Seismometers ◽  
Cross Correlations

SUMMARY We use seismic noise cross-correlations to obtain a 3-D tomography model of SV-wave velocities beneath the western Indian Ocean, in the depth range of the oceanic crust and uppermost mantle. The study area covers 2000 × 2000 km2 between Madagascar and the three spreading ridges of the Indian Ocean, centred on the volcanic hotspot of La Réunion. We use seismograms from 38 ocean bottom seismometers (OBSs) deployed by the RHUM-RUM project and 10 island stations on La Réunion, Madagascar, Mauritius, Rodrigues, and Tromelin. Phase cross-correlations are calculated for 1119 OBS-to-OBS, land-to-OBS, and land-to-land station pairs, and a phase-weighted stacking algorithm yields robust group velocity measurements in the period range of 3–50 s. We demonstrate that OBS correlations across large interstation distances of >2000 km are of sufficiently high quality for large-scale tomography of ocean basins. Many OBSs yielded similarly good group velocity measurements as land stations. Besides Rayleigh waves, the noise correlations contain a low-velocity wave type propagating at 0.8–1.5 km s−1 over distances exceeding 1000 km, presumably Scholte waves travelling through seafloor sediments. The 100 highest-quality group velocity curves are selected for tomographic inversion at crustal and lithospheric depths. The inversion is executed jointly with a data set of longer-period, Rayleigh-wave phase and group velocity measurements from earthquakes, which had previously yielded a 3-D model of Indian Ocean lithosphere and asthenosphere. Robust resolution tests and plausible structural findings in the upper 30 km validate the use of noise-derived OBS correlations for adding crustal structure to earthquake-derived tomography of the oceanic mantle. Relative to crustal reference model CRUST1.0, our new shear-velocity model tends to enhance both slow and fast anomalies. It reveals slow anomalies at 20 km depth beneath La Réunion, Mauritius, Rodrigues Ridge, Madagascar Rise, and beneath the Central Indian spreading ridge. These structures can clearly be associated with increased crustal thickness and/or volcanic activity. Locally thickened crust beneath La Réunion and Mauritius is probably related to magmatic underplating by the hotspot. In addition, these islands are characterized by a thickened lithosphere that may reflect the depleted, dehydrated mantle regions from which the crustal melts where sourced. Our tomography model is available as electronic supplement.

Focal mechanisms of earthquakes in the Indian Ocean and adjacent regions

1969 ◽  
Vol 74 (2) ◽  
pp. 632-649 ◽  
Author(s):  
A. R. Banghar ◽  
Lynn R. Sykes
Keyword(s):  
Indian Ocean ◽  
Focal Mechanisms ◽  
The Indian Ocean

The tectonic evolution of the Indian Ocean Triple Junction, anomaly 6 to present

1993 ◽  
Vol 98 (B2) ◽  
pp. 1793-1812 ◽  
Author(s):  
Neil C. Mitchell ◽  
Lindsay M. Parson
Keyword(s):  
Indian Ocean ◽  
Triple Junction ◽  
Tectonic Evolution ◽  
The Indian Ocean

Microseismicity near the Indian Ocean triple junction

1977 ◽  
Vol 4 (12) ◽  
pp. 597-600 ◽  
Author(s):  
Sean C. Solomon ◽  
Paul J. Mattaboni ◽  
Richard L. Hester
Keyword(s):  
Indian Ocean ◽  
Triple Junction ◽  
The Indian Ocean

Shallow Nonvolcanic Tremor Activity and Potential Repeating Earthquakes in the Chile Triple Junction: Seismic Evidence of the Subduction of the Active Nazca–Antarctic Spreading Center

2019 ◽  
Author(s):  
Miguel Sáez ◽  
Sergio Ruiz ◽  
Satoshi Ide ◽  
Hiroko Sugioka
Keyword(s):  
Triple Junction ◽  
Local Maximum ◽  
Time Correlation ◽  
Spreading Center ◽  
Ocean Bottom ◽  
P Waves ◽  
South American Plate ◽  
Repeating Earthquakes ◽  
Ocean Bottom Seismometers ◽  
Chile Triple Junction

ABSTRACT In southern Chile, at ∼46.2°S and ∼75.2°W, the active spreading center between the Nazca and Antarctic plates is colliding with the South American plate, forming the Chile triple junction (CTJ). For 1 yr, from March 2009 to February 2010, five ocean‐bottom seismometers (OBSs) were deployed over the CTJ. We used a portion of the OBS data to study the seismic signatures of the subduction of the active Nazca–Antarctic spreading center. Using the envelope technique, we detected long episodes of shallow nonvolcanic tremor (NVT) activity. To improve the identified location of the NVT activity, we cross‐correlated the vertical and horizontal components of all located NVTs. In different months, we measured the local maximum of the lag‐time correlation near 2 s, which is associated with the lag between the S and P waves (S−Ptime). Furthermore, we observed that in the days with intense tremor activity, the maxima corresponding to S−Ptime emerged in windows without observable NVTs. We suggest that days with intense tremor activity correspond to an almost continuous slow slip, which may accelerate and decelerates nearly randomly, with spatial and temporal heterogeneity. In addition, we detected some potential repeating earthquakes with an S−Ptime near 2 s, as well as NVTs. The detected NVT activity and potential repeating earthquakes suggest the existence of a shallow region close to the CTJ that is able to generate brittle (earthquakes) and brittle–ductile (potential repeating earthquakes and NVTs) ruptures.

scholarly journals Precise aftershock distribution of the 2019 Yamagata-oki earthquake using newly developed simple anchored-buoy ocean bottom seismometers and land seismic stations

2022 ◽  
Vol 74 (1) ◽  
Author(s):  
Masanao Shinohara ◽  
Shin’ichi Sakai ◽  
Tomomi Okada ◽  
Hiroshi Sato ◽  
Yusuke Yamashita ◽  
...  
Keyword(s):  
Shallow Water ◽  
Travel Time ◽  
Focal Mechanism ◽  
Water Depth ◽  
Source Area ◽  
Focal Mechanisms ◽  
Reverse Fault ◽  
Ocean Bottom ◽  
Fault Type ◽  
Ocean Bottom Seismometers

AbstractAn earthquake with a magnitude of 6.7 occurred in the Japan Sea off Yamagata on June 18, 2019. The mainshock had a source mechanism of reverse-fault type with a compression axis of WNW–ESE direction. Since the source area is positioned in a marine area, seafloor seismic observation is indispensable for obtaining the precise distribution of the aftershocks. The source area has a water depth of less than 100 m, and fishing activity is high. It is difficult to perform aftershock observation using ordinary free-fall pop-up type ocean bottom seismometers (OBSs). We developed a simple anchored-buoy type OBS for shallow water depths and performed the seafloor observation using this. The seafloor seismic unit had three-component seismometers and a hydrophone. Two orthogonal tiltmeters and an azimuth meter monitored the attitude of the package. For seismic observation at shallow water depth, we concluded that an anchored-buoy system would have the advantage of avoiding accidents. Our anchored-buoy OBS was based on a system used in fisheries. We deployed three anchored-buoy OBSs in the source region where the water depth was approximately 80 m on July 5, 2019, and two of the OBSs were recovered on July 13, 2019. Temporary land seismic stations with a three-component seismometer were also installed. The arrival times of P- and S-waves were read from the records of the OBSs and land stations, and we located hypocenters with correction for travel time. A preliminary location was performed using absolute travel time and final hypocenters were obtained using the double-difference method. The aftershocks were distributed at a depth range of 2.5 km to 10 km and along a plane dipping to the southeast. The plane formed by the aftershocks is consistent with the focal mechanism of the mainshock. The activity region of the aftershocks was positioned in the upper part of the upper crust. Focal mechanisms were estimated using the polarity of the first arrivals. Although many aftershocks had a reverse-fault focal mechanism similar to the focal solution of the mainshock, normal-fault type and strike–slip fault type focal mechanisms were also estimated. Graphical Abstract

Evolution of the Indian Ocean Triple Junction between 65 and 49 Ma (anomalies 28 to 21)

1993 ◽  
Vol 98 (B8) ◽  
pp. 13863-13877 ◽  
Author(s):  
Jérôme Dyment
Keyword(s):  
Indian Ocean ◽  
Triple Junction ◽  
The Indian Ocean
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