Seismotectonic evaluation of off Nicobar earthquake swarms, Andaman Sea

The off Nicobar region in the Andaman Sea is witnessing frequent earthquake swarms after December 2004 Tsunamigenic earthquake in January 2005, March and October 2014, November 2015 and April 2019. In this study, we present the geophysical evidence of active volcanism in the Off Nicobar back-arc region on 21st and 22nd March 2014 based on a passive Ocean Bottom Seismometer (OBS) experiment. We detected a series of hybrid earthquake events characterized by the onset of high&#8211;frequency signal (1-10 Hz) which is followed by a long period waveform of up to 600s having a range of 0.1-1 Hz. The waveforms appear to be emergent and lack the onset of a distinct S-phase. We also observed a very high frequency (10-40 Hz) hydro-acoustic phase in the coda of long-period events.&#160; These hybrid events are considered to be volcano-tectonic (VT) events that may trigger magmatic activities in the Off Nicobar region. We have identified and located 141 high-frequency events on 21st and 22nd March 2014 using hypocent v.3.2 program and they are distributed along NW-SE direction aligning with the submarine volcanoes defining the volcanic arc as observed in the high-resolution bathymetry data. The fault plane solution of the major high-frequency events suggests strike-slip faulting with the strike, dip and rake values of 334&#176;, 89&#176; and 171&#176;, respectively along the direction of the prevalent sliver strike-slip faulting in the Andaman back-arc region. We propose that the upward movement of magma is a plausible mechanism which can explain the frequent occurrence of earthquake swarms in the off Nicobar region. The stress generated from magma movement may initially trigger shallow VT events such as faulting or dike intrusions and later generate long period ringing associated with the resonance of the magma chamber. The shallow nature of the events also generates a hydroacoustic wave which is detected in the OBS experiment as the source region is in the SOFAR channel.

Download Full-text

Earthquake swarms reveal submarine magma unrest induced by distant mega-earthquakes: Andaman Sea region

Journal of Asian Earth Sciences ◽

10.1016/j.jseaes.2015.11.017 ◽

2016 ◽

Vol 116 ◽

pp. 155-163 ◽

Cited By ~ 1

Author(s):

Aleš Špičák ◽

Jiří Vaněk

Keyword(s):

Andaman Sea ◽

Earthquake Swarms

Download Full-text

Sub-surface magma movement inferred from low-frequency seismic events in the off-Nicobar region, Andaman Sea

Scientific Reports ◽

10.1038/s41598-020-78216-2 ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

K. K. Aswini ◽

Pawan Dewangan ◽

K. A. Kamesh Raju ◽

V. Yatheesh ◽

Pabitra Singha ◽

...

Keyword(s):

High Frequency ◽

Low Frequency ◽

Andaman Sea ◽

Earthquake Swarms ◽

Ocean Bottom ◽

Upward Movement ◽

Ocean Bottom Seismometer ◽

Magma Pulses ◽

Obs Data ◽

Acoustic Phase

AbstractMonitoring volcanic activity along the submarine volcanoes that are usually induced by subsurface magmatism is a challenge. We present fresh set of Ocean Bottom Seismometer (OBS) data that shows geophysical evidence indicative of subsurface magmatism along the submarine volcanoes in the off Nicobar region, Andaman Sea. In this region, we observed for the first time, hybrid very long-period earthquakes documented by passive OBS experiment. These events were initiated by high-frequency (5–10 Hz) with a clear onset of P-phase followed by low-frequency (0.01–0.5 Hz) oscillations in the range of 300–600 s with a prominent high-frequency (10–40 Hz) hydro-acoustic phase. A total of 141 high-frequency events were detected on 21st and 22nd March 2014 out of which 71 were of low-frequency oscillations. These events are distributed in the northwest–southeast direction along the submarine volcanic arc and Seulimeum strand of Great Sumatra fault. Off Nicobar region has been witnessing frequent earthquake swarms since 26th December 2004 tsunamigenic Sumatra earthquake. These swarms occurred in January 2005, March and October 2014, November 2015 and March 2019. The occurrence of low-frequency earthquakes and prominent hydro-acoustic phase are suggestive of sub-surface tectonic and magmatic influence. We propose that upward movement of magma pulses from deeper magma reservoir to the shallow magma chamber activated the strike-slip movement of sliver faults and induced earthquake swarms in the off Nicobar region.

Download Full-text

New island in Andaman sea?

Nature India ◽

10.1038/nindia.2009.131 ◽

2009 ◽

Keyword(s):

Andaman Sea

Download Full-text

Foreshocks, Aftershocks and Earthquake Swarms (V)

Papers in Meteorology and Geophysics ◽

10.2467/mripapers1950.19.3_437 ◽

1968 ◽

Vol 19 (3) ◽

pp. 437-445

Author(s):

Norio Yamakawa

Keyword(s):

Earthquake Swarms

Download Full-text

GAS HYDRATE SATURATION ESTIMATED FROM ACOUSTIC IMPEDANCE IN THE ANDAMAN SEA, INDIA

Marine Geology & Quaternary Geology ◽

10.3724/sp.j.1140.2013.02163 ◽

2014 ◽

Vol 33 (2) ◽

pp. 163-168

Author(s):

Xiujuan WANG ◽

Jiliang WANG ◽

Wei LI ◽

Nittala Satyavani ◽

Kalachand Sain

Keyword(s):

Gas Hydrate ◽

Acoustic Impedance ◽

Andaman Sea ◽

Hydrate Saturation

Download Full-text

Simulation of diurnal variability in vertical density structure using a coupled model

Scientific Reports ◽

10.1038/s41598-021-90426-w ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

B. Yadidya ◽

A. D. Rao ◽

Sachiko Mohanty

Keyword(s):

Mixed Layer ◽

3D Model ◽

Coupled Model ◽

Wave Model ◽

Andaman Sea ◽

Surface Mixed Layer ◽

Diurnal Variability ◽

Rama Buoy ◽

Vertical Displacements ◽

Primary Advantage

AbstractThe changes in the physical properties of the ocean on a diurnal scale primarily occur in the surface mixed layer and the pycnocline. Price–Weller–Pinkel model, which modifies the surface mixed layer, and the internal wave model based on Garrett–Munk spectra that calculates the vertical displacements due to internal waves are coupled to simulate the diurnal variability in temperature and salinity, and thereby density profiles. The coupled model is used to simulate the hourly variations in density at RAMA buoy (15° N, 90° E), in the central Bay of Bengal, and at BD12 (10.5° N, 94° E), in the Andaman Sea. The simulations are validated with the in-situ observations from December 2013 to November 2014. The primary advantage of this model is that it could simulate spatial variability as well. An integrated model is also tested and validated by using the output of the 3D model to initialize the coupled model during January, April, July, and October. The 3D model can be used to initialize the coupled model at any given location within the model domain to simulate the diurnal variability of density. The simulations showed promising results which could be further used in simulating the acoustic fields and propagation losses which are crucial for Navy operations.

Download Full-text