Abstract by Claire Ashcraft
Ron Harris, Jared Whitehead
Identifying the Source of an 1820 Earthquake and Tsunami South of Sulawesi, Indonesia through Geologic Data and Numerical Modeling
Digital 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. Adjacent to the fault the island of Selayar provides geomorphic clues, such as uplifted coral terraces and differences in sinuosity, that indicate the east coast has subsided and the west coast has uplifted, similar to a subduction forearc. A lack of earthquakes since 1820 shows the fault is in a stage of strain accumulation. GPS measurements show that it may have built up 2.0-3.4 m of strain since 1820, which could produce a Mw 8.1-8.2 earthquake. The last major event like this, the 1820 quake, created a tsunami 18-24 m high. This occurred before the invention of modern seismographs, so the exact moment magnitude is unknown, but generating a wave of that height would require a high-magnitude earthquake. Using statistical methods, it is possible to reconstruct the most likely earthquake source parameters for the 1820 quake. This sheds light on the fault’s dynamics and how it may act in the future.