The Shillong Plateau (SP) is globally renowned for its high seismic activity. The seismicity is mainly caused by the subduction of the Indian plate beneath the Eurasian and Burmese plates in the north and east, respectively, in addition to the popup of SP. In the present study, we analyze the seismicity of the SP and adjoining region bounded by latitude from 22.8° to 28.5°N and longitude 87.5° to 95.5°E using earthquake data for the period 825–2024 acquired from national, international, and literature sources. 825–2024, 2019–2024, 2008–2018, 1997–2007, 1986–1996, 1975–1985, 1964–1974, 1901–1963, 1801–1900, and 825–1800 periods have been considered to estimate and compare the spatio-temporal variation of seismicity parameters. We estimated the spatio-temporal variation of the magnitude of completeness (MC), a-value, b-value, and fractal dimension (DC) of the study area. MC, a-value, and b-value for the above periods range from 4.70 to 5.70, 4.36 to 9.85, and 0.52 to 1.59. However, spatial mapping of MC, a-value, and b-value at each node of the grid of 0.05°× 0.05° range from 4.10 to 5.82, 4.46 to 18.94, and 0.58 to 3.66, respectively. Spatial mapping of DC at each node of the grid of 1°×1° and 0.5° × 0.5° range from 0.258 to 2.240 and 0.462 to 2.164, respectively. However, the temporal variation of DC ranges from 0.344 to 2.842. The relationship between b-values for the entire study period and DC-values shows a positive correlation, while a negative correlation exists between <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="12040_2025_2579_Article_IEq1.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="29" /> </InlineMediaObject> <EquationSource Format="TEX">$a/b$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>a</mi> <mo stretchy="false">/</mo> <mi>b</mi> </mrow> </math></EquationSource> </InlineEquation>-values and DC-values. The spatio-temporal distributions of these parameters reveal insights into the regional variation of stress levels and geological complexity, which can be used as input for seismic hazard assessment.

Spatio-temporal mapping of seismicity parameters in Shillong Plateau and adjoining regions

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2025年5月27日

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Mohd Shahabuddin,
William Kumar Mohanty

摘要

The Shillong Plateau (SP) is globally renowned for its high seismic activity. The seismicity is mainly caused by the subduction of the Indian plate beneath the Eurasian and Burmese plates in the north and east, respectively, in addition to the popup of SP. In the present study, we analyze the seismicity of the SP and adjoining region bounded by latitude from 22.8° to 28.5°N and longitude 87.5° to 95.5°E using earthquake data for the period 825–2024 acquired from national, international, and literature sources. 825–2024, 2019–2024, 2008–2018, 1997–2007, 1986–1996, 1975–1985, 1964–1974, 1901–1963, 1801–1900, and 825–1800 periods have been considered to estimate and compare the spatio-temporal variation of seismicity parameters. We estimated the spatio-temporal variation of the magnitude of completeness (M_C), a-value, b-value, and fractal dimension (D_C) of the study area. M_C, a-value, and b-value for the above periods range from 4.70 to 5.70, 4.36 to 9.85, and 0.52 to 1.59. However, spatial mapping of M_C, a-value, and b-value at each node of the grid of 0.05°× 0.05° range from 4.10 to 5.82, 4.46 to 18.94, and 0.58 to 3.66, respectively. Spatial mapping of D_C at each node of the grid of 1°×1° and 0.5° × 0.5° range from 0.258 to 2.240 and 0.462 to 2.164, respectively. However, the temporal variation of D_C ranges from 0.344 to 2.842. The relationship between b-values for the entire study period and D_C-values shows a positive correlation, while a negative correlation exists between $a/b$ $a / b$ -values and D_C-values. The spatio-temporal distributions of these parameters reveal insights into the regional variation of stress levels and geological complexity, which can be used as input for seismic hazard assessment.