Seismic and tsunami hazard potential of the Negros–Sulu megathrust, Philippines
- 1University of the Philippines Diliman (Quezon City, Philippines)
Abstract
The Negros–Sulu megathrust poses an imminent threat to coastal communities surrounding the Sulu Sea, but with limited information on past tsunamis, megathrust geometry, and locked segments, robust seismic and tsunami hazard assessments are hindered. To identify highly exposed coastal areas amid this knowledge gap, we estimated the Negros–Sulu megathrust source parameters using a structural-based segmentation and scaling-relation approach for tsunami modeling. A total of 18 sets of source parameters from six segments and three dip angle scenarios were considered with moment magnitude and average slip of M w 8.0–8.9 and 1.68–6.23 m, respectively. Tsunami simulations were modeled in JAGURS, accounting for nonlinear shallow water equations, horizontal and vertical seafloor displacements, and Boussinesq dispersion effects. Coastal regions directly facing the segments have the highest exposures with <2 min arrival times, highlighting the major control of wave directivity and the need for rapid evacuation strategies. The Negros Trench generates up to 6 m wave height and 7 m s ⁻¹ flow velocity, while the Sulu Trench produces up to 8 m and 6 m s ⁻¹ . Coastal areas with ≥2 m wave heights typically exhibit a concave morphology with a nearshore width interquartile range of 2–4.5 km. At wider nearshore widths (>20 km), wave dissipation results in lower wave heights (<2 m) that underscore the need for accurate nearshore bathymetry in tsunami modeling. As average slip is used in these models, we highlight that the maximum wave height and flow velocity are likely underestimated and recommend treating them as minimum values. Nonetheless, the relative exposure levels of coastal areas from these results provide a significant basis for regional-scale tsunami risk mitigation strategies and for searching tsunami deposits.
Versions
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BibTeX
@article{jr2026seismic,
title = {{Seismic and tsunami hazard potential of the Negros–Sulu megathrust, Philippines}},
author = {Lyndon P. Nawanao Jr. and Noelynna T. Ramos and Toshitaka Baba and Naotaka Chikasada and Kenji Satake},
journal = {Natural Hazards and Earth System Sciences},
year = {2026},
month = oct,
doi = {10.5194/nhess-26-5035-2026},
url = {https://nhess.copernicus.org/articles/26/5035/2026/},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Seismic and tsunami hazard potential of the Negros–Sulu megathrust, Philippines
AU - Lyndon P. Nawanao Jr.
AU - Noelynna T. Ramos
AU - Toshitaka Baba
AU - Naotaka Chikasada
AU - Kenji Satake
PY - 2026
DA - 2026/10/14
JO - Natural Hazards and Earth System Sciences
DO - 10.5194/nhess-26-5035-2026
UR - https://nhess.copernicus.org/articles/26/5035/2026/
AB - The Negros–Sulu megathrust poses an imminent threat to coastal communities surrounding the Sulu Sea, but with limited information on past tsunamis, megathrust geometry, and locked segments, robust seismic and tsunami hazard assessments are hindered. To identify highly exposed coastal areas amid this knowledge gap, we estimated the Negros–Sulu megathrust source parameters using a structural-based segmentation and scaling-relation approach for tsunami modeling. A total of 18 sets of source parameters from six segments and three dip angle scenarios were considered with moment magnitude and average slip of M w 8.0–8.9 and 1.68–6.23 m, respectively. Tsunami simulations were modeled in JAGURS, accounting for nonlinear shallow water equations, horizontal and vertical seafloor displacements, and Boussinesq dispersion effects. Coastal regions directly facing the segments have the highest exposures with <2 min arrival times, highlighting the major control of wave directivity and the need for rapid evacuation strategies. The Negros Trench generates up to 6 m wave height and 7 m s ⁻¹ flow velocity, while the Sulu Trench produces up to 8 m and 6 m s ⁻¹ . Coastal areas with ≥2 m wave heights typically exhibit a concave morphology with a nearshore width interquartile range of 2–4.5 km. At wider nearshore widths (>20 km), wave dissipation results in lower wave heights (<2 m) that underscore the need for accurate nearshore bathymetry in tsunami modeling. As average slip is used in these models, we highlight that the maximum wave height and flow velocity are likely underestimated and recommend treating them as minimum values. Nonetheless, the relative exposure levels of coastal areas from these results provide a significant basis for regional-scale tsunami risk mitigation strategies and for searching tsunami deposits.
SN - 1684-9981
ER -