1906 San Dcisco Earthquake Research Paper

Modulus: 1X Earth Science

Name: Leroy (CHAN CHUNG YIU)

Staff member in charge: Tim Dempster

ID:2183820C

Title: The April 1906 San Francisco Earthquake

Introduction

On April 18th, 1906, one of the worst natural disasters happened in the US history. This first major disaster which is recorded in human history with photography, has a 7.8 magnitude(USGS,2013).A subduction of the Pacific plates pulled into the San Andreas plates with the north-west direction, causing a 400 km(ECSC) rupture line. Huge energy is radiated out of the epicenter which was just 2 miles of west San Francisco, the intensity of the shaking nearly wiped out most of the buildings and structures with a duration of 110s(ECSC), affected around 370,000 square meters(NZH,1906).

Usually because the plates have friction, the stresses build up on the surface. The process is relatively slow with a rate of 1 inch per year, until one of the surface slips due to high pressure. The slippage speed up to 5000 miles an hour, the pressure tears down the fault to a stuck patch which slows down the speed of the moving plates. The plates may break though the stuck patch and continue to the next knot and affecting more area.(USGS)

Geology in San

Which is covered with series of subparallel faults between Pacific and North American plates, faults consisting complex trace and multiple traces(USGS). Rocks on the continent generally made up of Iron and Magnesium. There was a was 7.9 magnitude earthquake happened in 1857 before the one happened in 1906. The south fault of the Pacific and North American plates are slipping to the direction north-west with a rate of 33-37mm/yr.

The formation of the San Francisco Bay

The San Francisco Bay is divided into 4 sub-bays, Central Bay, South Bay, Suisun Bay and San Pablo bay which contains rivers and channels. The San Francisco bay is located 27 miles west from the golden gate. 14000 years ago the Farallon island was extended west to a few miles and beyond, which was the west coast of North America. As the ice age ended, the sea level rose. 7000 years ago the dramatic shift of sea level slow, sediment flowing in from surrounding hills in the Great Valley England settled around the edges and create the San Francisco in present. (Reference from BBC, by Jonathan Amos, The figure shows the fault lines between the area of the west side of America and as we can see San Francisco is located nearly the central between the fault lines which makes it highly risk to occur