Estimation of source parameters and scaling relations for local earthquakes of Lohit Valley in Arunachal Himalaya, Northeast India

Abstract

We estimate the source parameters (stress drop, corner frequency, source radius and scalar seismic moment) for local earthquakes that occurred during 2007–2008 in the Lohit Valley, Arunachal Himalaya in northeast India. The source parameters of 33 selected earthquakes (2.0 ≤ ML ≤ 4.4) are estimated by spectral analysis of P‐waves of the vertical component. The results are authenticated further by spectral analysis of S‐waves of horizontal component seismograms. Both P‐ and S‐wave spectral analyses show comparable results. The earthquakes' seismic moment varies from 2.66 × 1012 to 1.16 × 1015 N.m. The estimates of stress drop and source radius range from ~0.145 to 31.85 bar and ~242 to 647 m, respectively. The majority of the earthquakes show a low‐stress drop (≤10 bar). We interpret that the low‐stress drop is plausibly due to the presence of creeping patches in the thrust sheets in the study area within the upper ~10 km depth, which is not able to withstand much stress and release it in the forms of micro‐earthquakes. The scaling relations have been developed between important source parameters (ML, Mw, M0, ∆σ, and fc), which can serve as useful inputs for the assessment of earthquake hazards in the region.

Introduction, Part 2—Geodynamic evolution of Eastern Himalaya and Indo‐Myanmar orogenic belts: Advances through interdisciplinary studies

“…The first paper by Kundu and Hazarika (2022) has estimated the source parameters (stress drop, corner frequency, source radius, and scalar seismic moment) for local earthquakes that occurred during 2007–2008 in the Lohit Valley, Arunachal Himalaya in north‐east India. The majority of the earthquakes show a low‐stress drop (≤10 bar).…”

“…The Himalaya mountain belt is about 2500 km in length, from west to east, and is a classic example of an orogenic system created by the continent-continent collision between the Indian-Eurasian plates F I G U R E 2 Geological map of Eastern Himalaya, Indo-Myanmar orogenic belt, northern, Central Myanmar, and adjacent areas (modified after Mitchell et al, 2007;Searle et al, 2007;. Locations of study area presented in the issue include 1/S2: Kundu and Hazarika (2022); 2/S2: Y. R. ; 3/S2: Rawat and Luirei (2022) Chaubey et al (2022); 24/S2: ; Bora, Mukherjee, et al (2022); 25/S2: Khuman and Ibotombi (2022); 26/S2: Y. R. ; 27/S2: Thokchom and Kshetrimayum (2021); 28/S2: Barman et al (2022); 29/S2: V. Sharma and Biswas (2022) along the Indus-Tsangpo Suture Zone (ITSZ) $55 Ma ago (de Sigoyer et al, 2000;DeCelles et al, 2001;Yin, 2006). The southern parts of the Eurasian Plate mainly have the Trans-Himalaya, Ladakh batholith, Gangdese batholith, Lohit batholith, Karakoram Ranges, Ophiolites, Indus-Tsangpo Mélange zone, etc.…”

“…The first paper by Kundu and Hazarika (2022) Apart from infrastructural degeneracy, the 2011 Sikkim Earthquake (Mw 6.9) also caused generation of co-seismic landslides within $100 km epicentral distance from the earthquake. After a decade of the 2011 earthquake, Gangtok city and other parts of the state have been rebuilt and reconstructed again, but most of the newly constructed and old refurbished buildings are established in the steep slope areas without considering the geotechnical properties of the underlying soil.…”

“…Geological map of Eastern Himalaya, Indo‐Myanmar orogenic belt, northern, Central Myanmar, and adjacent areas (modified after Mitchell et al, 2007; Searle et al, 2007; Y. R. Singh, Singh, Singh, et al, 2022). Locations of study area presented in the issue include 1/S2: Kundu and Hazarika (2022); 2/S2: Y. R. Singh, Singh, Singh, et al (2022); 3/S2: Rawat and Luirei (2022); 4/S2: Kayal et al (2022); 5/S2: Choudhury et al (2022); 6/S2: N. M. Sharma et al (2022); 7/S2: Goswami, Gogoi, et al (2022); 8/S2: Bikramaditya et al (2022); 9/S2: Goswami, Kalita, et al (2022); 10/S2: Joshi (2022); 11/S2: Jha and Sharma (2022); 12/S2: Shukla et al (2022); 13/S2: Khonglah et al (2022); 14/S2: Ali and Duarah (2022); 15/S2: Mohanty et al (2022); 16/S2: Chanu et al (2022); 17/S2: Majumdar, Gogoi, and Ghatak (2022); Majumdar, Gogoi, Ghatak, Saikia, et al (2022); 18/S2: Ding et al (2022); 19/S2: Ghose et al (2022); 20/S2: Hussain and Dey (2022); 21/S2: Ozukum et al (2022); 22/S2: Jamir et al (2022); 23/S2: Chaubey et al (2022); 24/S2: Bora, Borah, et al (2022); Bora, Mukherjee, et al (2022); 25/S2: Khuman and Ibotombi (2022); 26/S2: Y. R. Singh, Singh, Singh, et al (2022); 27/S2: Thokchom and Kshetrimayum (2021); 28/S2: Barman et al (2022); 29/S2: V. Sharma and Biswas (2022)…”