Kerry Sieh studies the geological record to understand the geometries of active faults, the earthquakes they generate, and the crustal deformation their movements produce. His early work studying geological layers and landforms along the San Andreas fault led to the discovery of how often and how regularly it produces large earthquakes in southern California. More recently, Kerry Sieh, along with his students and colleagues, have investigated Taiwan's multitude of active faults and figured out how their earthquakes are continuously creating that mountainous island.One of Sieh’s group’s current research interests is the subduction megathrust that produced the devastating giant Sumatran earthquakes and Indian Ocean tsunamis of 2004 and 2005. A chain of outer arc islands, southwest of Sumatra, sits above this megathrust. This group of islands rises and falls as strain accumulates gradually between earthquakes and is released suddenly during the giant ruptures. Certain corals, called microatolls, surround these islands and record relative sea level changes as the islands move up or down. By carefully studying the coral microatolls, geologists can piece together a record of past strain accumulation and earthquakes. Sieh’s research suggests that the megathrust is poised to produce yet another giant earthquake in western Sumatra.Professor Sieh’s group is also exploring the earthquake geology and hazards of Myanmar (Burma).