Abstract by Claire Ashcraft
Identifying the Source of an 1820 Earthquake and Tsunami South of Sulawesi, Indonesia and Evaluating the Potential of a Future Recurrence
Numerical modeling of a giant earthquake and tsunami that struck the SW coast of Sulawesi, Indonesia in 1820 has identified the most likely source as the Walinae Fault. The nearby island of Selayar provides geomorphic clues, such as uplifted coral terraces and differences in coastal sinuosity, that indicate the east coast has subsided and the west coast has uplifted, similar to a subduction forearc (the reverse of a typical forearc). A lack of earthquakes since 1820 shows the Walinae fault is in a stage of strain accumulation, and GPS measurements indicate it may have accumulated 2.0-3.4 m of strain since 1820. This strain over a distance of 250 km could produce a Mw 8.1-8.2 earthquake. The last major event like this, the 1820 event, produced a tsunami 18-24 m high. This occurred prior to the invention of seismographs, so the exact magnitude is unknown, but the length of shaking time and the size of the tsunami are consistent with a giant earthquake. The strain accumulation and drastic population increase since this event pose a significant threat to the area.