Modelling of source parameters of local earthquakes and seismotectonic implications in Siang Valley, NE India

IF 1.3 4区地球科学 Q3 GEOSCIENCES, MULTIDISCIPLINARY Journal of Earth System Science Pub Date : 2024-04-04 DOI:10.1007/s12040-024-02272-9

Ashish Pal, Dilip Kumar Yadav, Naresh Kumar, Abhishek Kumar Gupta, Ajay Paul, H C Nainwal

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Abstract

A moderate size earthquake (M_L 5.9) occurred near Mechuka in Siang Valley on 23rd April 2019 at 20:15:50.00 UTC in the rupture zone of the great Assam earthquake of 15th August 1950. This shallow-focused earthquake occurred close to NE trending Main Central Thrust has a thrust fault mechanism striking parallel to this major tectonics of the Himalaya. Including this event, a dataset of 46 local, micro and low magnitude earthquakes (1.5 ≤ M_L ≤ 5.9) of the Siang Valley of Arunachal Pradesh, NE India, are evaluated for the characteristics of the earthquake source, seismicity, stress drop and tectonic structures. The earthquake events were recorded by a close digital network of eight broadband seismic stations installed in December 2018 in the Siang Valley. The stress drop (Δσ) obtained for the Mechuka earthquake in the Siang Valley is 114.71 bars, the seismic moment (Mo) of 6.86E + 16 Nm and the source radius (r) of 1392.41 m. The seismic moments obtained from the microearthquakes vary between 2.44E + 11 and 6.86E + 16 Nm, and the source radius varies from 172.90 to 1392.41 m based on Brune’s circular source model 1970. The corner frequencies (fc) of the events range from 1.03 to 8.04 Hz. Seismically intense clustering of microearthquakes has a low-stress drop below 10 bar except for the Mechuka earthquake, which varies from 0.05 to 114.72. This high-stress drop of moderate earthquake compared to its low values of lower magnitude earthquakes indicates that the earthquake of 23rd April 2019 is associated with high-strength material accumulating high strain during the earthquake-building process. Moment magnitude of whole data set ranges from 1.52 to 5.16. The scaling relationship between Mo and fc is obtained as 9.089E + 16fc^–9.52, and for Mo and Δσ are modelled to be related as Mo = 8.96E + 10Δσ^2.86. Evaluated low-stress drop for the smaller size of earthquakes shows brittleness of the upper crustal region.

Research highlights

Modelling of earthquake source parameters to obtain scaling relations for Siang Valley, Arunachal Pradesh.
The estimated Mo, fc, r, ∆σ and Mw are 2.44 × 10¹¹ to 6.86 × 10¹⁶ Nm, 1.03–8.04 Hz, 172.90–1392.41 m, 0.05–114.71 bar and 1.52–5.16, respectively.
Scaling relation between Mo and fc, Mo and Δσ and Mw and fc is Mo = 9.089E + 16fc^−9.52, Mo = 8.96E + 10 Δσ^2.86 and Log fc = –0.39Mw + 2.39, respectively.

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印度东北部 Siang 谷当地地震震源参数建模及其地震构造影响

摘要 2019 年 4 月 23 日 20:15:50.00 UTC 时，在 1950 年 8 月 15 日阿萨姆邦大地震的断裂带上，Siang Valley 的 Mechuka 附近发生了一次中等规模的地震（ML 5.9）。这次浅源地震发生在东北走向的主中央推力断层附近，其推力断层机制与喜马拉雅山脉的这一主要构造平行。包括这次地震在内，我们对印度东北部阿鲁纳恰尔邦锡安河谷的 46 次局部、微震级和低震级地震（1.5 ≤ ML ≤ 5.9）的数据集进行了评估，以了解震源、震度、应力下降和构造结构的特征。地震事件由 2018 年 12 月在 Siang 谷安装的 8 个宽带地震台站组成的近距离数字网络记录。根据1970年Brune的圆形震源模型，微地震得到的地震力矩在2.44E+11到6.86E+16牛米之间，震源半径在172.90到1392.41米之间。事件的角频率（fc）在 1.03 至 8.04 Hz 之间。除 Mechuka 地震外，地震烈度较高的微地震群的应力降均低于 10 巴，从 0.05 到 114.72 不等。与低震级地震的低值相比，中震级地震的高应力下降表明，2019 年 4 月 23 日的地震与地震形成过程中积累高应变的高强度材料有关。整个数据集的矩震级在 1.52 到 5.16 之间。Mo 与 fc 的比例关系为 9.089E + 16fc-9.52，Mo 与 Δσ 的模型关系为 Mo = 8.96E + 10Δσ2.86。对较小规模地震的低应力下降的评估表明，上地壳区域是脆性的。研究重点模拟震源参数以获得阿鲁纳恰尔邦 Siang 谷的比例关系。Mo 与 fc、Mo 与 Δσ 和 Mw 与 fc 的比例关系分别为 Mo = 9.089E + 16fc-9.52、Mo = 8.96E + 10 Δσ2.86 和 Log fc = -0.39Mw + 2.39。

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来源期刊

Journal of Earth System Science Earth and Planetary Sciences-General Earth and Planetary Sciences

CiteScore

3.20

自引率

5.30%

发文量

226

期刊介绍： The Journal of Earth System Science, an International Journal, was earlier a part of the Proceedings of the Indian Academy of Sciences – Section A begun in 1934, and later split in 1978 into theme journals. This journal was published as Proceedings – Earth and Planetary Sciences since 1978, and in 2005 was renamed ‘Journal of Earth System Science’. The journal is highly inter-disciplinary and publishes scholarly research – new data, ideas, and conceptual advances – in Earth System Science. The focus is on the evolution of the Earth as a system: manuscripts describing changes of anthropogenic origin in a limited region are not considered unless they go beyond describing the changes to include an analysis of earth-system processes. The journal''s scope includes the solid earth (geosphere), the atmosphere, the hydrosphere (including cryosphere), and the biosphere; it also addresses related aspects of planetary and space sciences. Contributions pertaining to the Indian sub- continent and the surrounding Indian-Ocean region are particularly welcome. Given that a large number of manuscripts report either observations or model results for a limited domain, manuscripts intended for publication in JESS are expected to fulfill at least one of the following three criteria. The data should be of relevance and should be of statistically significant size and from a region from where such data are sparse. If the data are from a well-sampled region, the data size should be considerable and advance our knowledge of the region. A model study is carried out to explain observations reported either in the same manuscript or in the literature. The analysis, whether of data or with models, is novel and the inferences advance the current knowledge.