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- Title
Assessing the Risk of Potential Tsunamigenic Earthquakes in the Mentawai Region by Seismic Imaging, Central Sumatra.
- Authors
Qin, Yanfang; Chen, Jian; Singh, Satish C.; Hananto, Nugroho; Carton, Helene; Tapponnier, Paul
- Abstract
In the marginal regions along subduction zones, oceanic plates subducting beneath continental plates produce the largest number of earthquakes on Earth and sometimes devastating tsunamis. The lateral segmentation of earthquakes along the Sumatra subduction zone is well documented. However, the entirely different seismic behaviors among the segments indicate that local structures are key elements controlling coseismic slip propagation; in particular, frontal accretionary prism structures are closely associated with tsunami generation. Offshore of Central Sumatra, in the Mentawai segment, large earthquakes nucleated in 2007 and 2010 caused many human casualties and a great deal of property loss. Using seismic reflection data, we show the subsurface structure of accretionary over a significant portion of the frontal wedge that did not rupture during the 2007 earthquake, and this area remains locked. The subsurface deformation structure at the wedge front, which is similar to that in the 2010 Mw7.8 tsunami earthquake rupture zone, suggests the potential for a large tsunami earthquake in the near future. On the other hand, the along‐strike variations of the effective basal friction at shallow depth may indicate that different coseismic behaviors are caused by a sudden failure of the deeper seismogenic zone. Plain Language Summary: In certain areas where oceanic plates slide beneath continental plates (subduction zones), earthquakes and tsunamis, such as those seen in the Sumatra region, can lead to significant loss. Although previous studies show that earthquakes are segmented along the Sumatra subduction zone, indicating distinct seismic behaviors, the reasons behind these differences are not well understood. This study focuses on the Mentawai segment off Central Sumatra, where large earthquakes occurred in 2007 and 2010, causing casualties and property damage. We use seismic reflection data to image the subsurface structure of the frontal wedge, an area associated with tsunami generation. In the portion of the wedge that did not rupture during the 2007 earthquake, our results indicate a potential threat of a future large tsunami earthquake. Interestingly, the different earthquake behaviors might be explained by variations in basal friction along the plate boundary fault. This research enhances our understanding of the factors influencing earthquake and tsunami generation in subduction zones, with implications for future hazard assessments. Key Points: The deformation structures at the wedge front consist of mixed vergent ramp faults and varying stratigraphic levels of décollementsThe mapped deformation structures in the unruptured segment are similar to those observed in the 2010 Mw7.8 tsunami earthquake rupture zoneThe along‐strike variations of the basal friction along the megathrust may indicate different coseismic behaviors and tsunami risk
- Subjects
SUMATRA (Indonesia); TSUNAMI warning systems; IMAGING systems in seismology; SUMATRA Earthquake, 2004; TSUNAMIS; EARTHQUAKES; SUBDUCTION zones; EARTHQUAKE zones; PROPERTY damage
- Publication
Geochemistry, Geophysics, Geosystems: G3, 2024, Vol 25, Issue 5, p1
- ISSN
1525-2027
- Publication type
Article
- DOI
10.1029/2023GC011149