The San Francisco Earthquake of 1906 By Mrs. Cheney

PROCESSES: EVENT & LOCATION The San Francisco earthquake of 1906 occurred on the northernmost part of the San Andreas Fault in California which is located on the Ring of Fire. This earthquake ranks as one of the most significant of all time due to the scientific information gained from the event and its sheer size (8-9 on the Richter scale) com/i/map/

PROCESSES: WHAT CAUSES THIS EVENT The earthquake was caused by a rupture or breakage of the rocks on the San Andreas fault line which forms a transform fault boundary between the Pacific and the North American plate. Transform faults occur where plates slide past each other and crust shifts. When these plates shift, pressure is released causing an earthquake. The Pacific Plate and Juan De Fuca Plate form a spreading center and are being pulled apart as energy from the core causes magma to move upward, cool and moves downward through a process called convection. Then, the more dense Juan de Fuca Plate subducts under the less dense North American plate which drives the transform boundary creating the San Andreas Fault zone.

RISKS: TYPE AND EFFECTS The many risks associated with earthquakes can be visibly seen in the photos, artifacts & captions below that illustrate the effects of the 1906 San Francisco Earthquake. Risks include death from collapsing buildings and debris, property damage from structures shaking back and forth, and permanent changes to the landscape from a shift in the plates. 3,000 deaths 225,000 out of 400,000 homeless 28,000 building destroyed $400,000,000 in 1906 dollars which is like 1,201,404,950 in 2011 dollars The earthquake caused the earth to offset (move) 8 ½ feet as shown above. Due to the chaos of destruction and homelessness, looting arose forcing the mayor to announce a “Shoot to Kill” people engaging in this activity. Complete destruction of a structure. Factors 1. People were not prepared as this was the first earthquake since the city was settled. 2.There was no emergency plan established for what to do after an earthquake.

RISKS: HISTORY OF EARTHQUAKES IN THIS AREA Is this event common for this area & why Because San Fransisco is located on the Ring of Fire where 80% of the world’s earthquakes occur, this type of event is a common ocurance. “Based on models and the rate of slipping on the San Andreas fault, the best prediction for another earthquake of this intensity in this area is in intervals of about 200 years”. “The real threat to the San Francisco Bay region over the next 30 years comes not from a 1906 type earthquake, but from smaller (magnitude 7) earthquakes occurring on the Hayward fault, the Peninsula segment Of the San Andreas fault, or the Rogers Creek fault.”

TECHNOLOGICAL ADVANCES Can We Forecast Earthquakes? We know a great deal about where earthquakes occur based on historical evidence of where they have occurred in the past and our understanding of plate tectonics and fault zones. “Most large earthquakes occur on long fault zones around the margin of the Pacific Ocean. This is because the Atlantic Ocean is growing a few inches wider each year, and the Pacific is shrinking as ocean floor is pushed beneath Pacific Rim continents. Geologically, earthquakes around the Pacific Rim are normal and expected.” What we cannot know exactly is when an earthquake might occur as even a seismometer only detects vibrations a few minutes before larger vibrations strike. This inability to forecast the exact time and date of the next earthquake contributes to many of the risks that are associated with them. There are systems in place to warn people or reduce the impact. The emergency broadcast system warns people once an event has occurred and directs people what to do. Along the coasts there are tsunami warnings as well Showing people routes to evacuate to after a large earthquake.

TECHNOLOGICAL ADVANCES SLIDE 6 CONTINUED How can people reduce future risks from Earthquakes? 1.Making current homes more earthquake resistant by making sure foundations are tied to the structure, anchoring furniture, and using supportive bracing is one way future damage can be avoided. 2.Understanding what to do in case of an earthquake whether you are at home, work or school. Taking earthquake drills seriously, having an emergency plan and supplies at home.

TECHNOLOGICAL ADVANCES CONTINUED. How did this event lead to any new precautionary systems? Since this earthquake in 1906 a large scale research program has developed in the US. As a result of this earthquake many advances have been made.  1,000 seismograph stations measure the shaking intensity in California.  Scientists have formed detailed pictures of the location and activity of hundreds of faults that make up the San Andreas fault system.  From this understanding, maps have been created that anticipate where shaking is likely to be strong, and these maps guide regional zoning and land use decisions affecting the location of schools, hospitals, homes and nuclear power plants.  Also from this understanding, engineers have developed building codes designed to produce buildings and bridges that can withstand the shaking.

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