Dr. Kerry Sieh , a veteran seismologist at the California Institute of Technology , has spent years studying some of the world 's wealthiest and poorest earthquake-prone territory -- not only the sickle-shaped scar of faults off Sumatra 's west coast that caused last week 's tsunami , but also California 's San Andreas fault , which could , with a sudden twitch , submerge the inhabitants of some of the most valuable land on Earth .