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<p>The Koyna–Warna region in southern India is a unique case of dual Reservoir-Triggered Seismicity (RTS), surrounding impoundments on Koyna and Warna rivers. In this study, we perform ambient noise surface wave tomography using data from a temporary dense deployment of three-component geophones in order to understand the origin of RTS. To achieve this objective, surface wave dispersion curves from noise cross-correlations in rotated coordinates were used to create group velocity maps in 0.5–5 s periods. The group velocity dispersions from map bins were inverted for shear wave velocity (<InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="41598_2025_12099_Article_IEq1.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="18" /> </InlineMediaObject> <EquationSource Format="TEX">\(V_s\)</EquationSource> </InlineEquation>) and <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="41598_2025_12099_Article_IEq1.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="18" /> </InlineMediaObject> <EquationSource Format="TEX">\(V_s\)</EquationSource> </InlineEquation> radial anisotropy (<InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="41598_2025_12099_Article_IEq3.gif" Format="GIF" Height="17" Rendition="HTML" Resolution="72" Type="Linedraw" Width="13" /> </InlineMediaObject> <EquationSource Format="TEX">\(\xi\)</EquationSource> </InlineEquation>) maps down to 5 km depth. The <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="41598_2025_12099_Article_IEq1.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="18" /> </InlineMediaObject> <EquationSource Format="TEX">\(V_s\)</EquationSource> </InlineEquation> and <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="41598_2025_12099_Article_IEq3.gif" Format="GIF" Height="17" Rendition="HTML" Resolution="72" Type="Linedraw" Width="13" /> </InlineMediaObject> <EquationSource Format="TEX">\(\xi\)</EquationSource> </InlineEquation> till 1 km depth are correlated with topographical features in agreement with the basement depth estimates. Large earthquakes in the region are marked by negative <InlineEquation ID="IEq6"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="41598_2025_12099_Article_IEq3.gif" Format="GIF" Height="17" Rendition="HTML" Resolution="72" Type="Linedraw" Width="13" /> </InlineMediaObject> <EquationSource Format="TEX">\(\xi\)</EquationSource> </InlineEquation> with negative <InlineEquation ID="IEq7"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="41598_2025_12099_Article_IEq1.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="18" /> </InlineMediaObject> <EquationSource Format="TEX">\(V_s\)</EquationSource> </InlineEquation> anomaly or <InlineEquation ID="IEq8"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="41598_2025_12099_Article_IEq1.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="18" /> </InlineMediaObject> <EquationSource Format="TEX">\(V_s\)</EquationSource> </InlineEquation> anomaly contrast, suggesting shear strength could be an important control on their genesis. A large negative <InlineEquation ID="IEq9"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="41598_2025_12099_Article_IEq1.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="18" /> </InlineMediaObject> <EquationSource Format="TEX">\(V_s\)</EquationSource> </InlineEquation> anomaly southwest of the Koyna reservoir is linked with reservoir water migration to greater depths, part of a larger interconnected system of pathways extending across the reservoirs. These results, set decades post reservoir impoundment, can help understand the evolution of RTS around dam sites elsewhere.</p>

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Investigating reservoir-triggered seismicity in the Koyna–Warna region through nodal ambient noise tomography

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  • 发表日期：

    2025年7月20日

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  • Pratul Ranjan,
  • Prakash Kumar,
  • Biswajit Mandal,
  • Periyasamy Karuppannan

摘要

The Koyna–Warna region in southern India is a unique case of dual Reservoir-Triggered Seismicity (RTS), surrounding impoundments on Koyna and Warna rivers. In this study, we perform ambient noise surface wave tomography using data from a temporary dense deployment of three-component geophones in order to understand the origin of RTS. To achieve this objective, surface wave dispersion curves from noise cross-correlations in rotated coordinates were used to create group velocity maps in 0.5–5 s periods. The group velocity dispersions from map bins were inverted for shear wave velocity ( \(V_s\) ) and \(V_s\) radial anisotropy ( \(\xi\) ) maps down to 5 km depth. The \(V_s\) and \(\xi\) till 1 km depth are correlated with topographical features in agreement with the basement depth estimates. Large earthquakes in the region are marked by negative \(\xi\) with negative \(V_s\) anomaly or \(V_s\) anomaly contrast, suggesting shear strength could be an important control on their genesis. A large negative \(V_s\) anomaly southwest of the Koyna reservoir is linked with reservoir water migration to greater depths, part of a larger interconnected system of pathways extending across the reservoirs. These results, set decades post reservoir impoundment, can help understand the evolution of RTS around dam sites elsewhere.