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Earthquake Causes: An earthquake is the violent shaking of the earth caused by

Earthquake Causes: An earthquake is the violent shaking of the earth caused by a sudden movement of rock beneath its surface. Plate Tectonics: Although earthquakes can occur anywhere on earth, the majority of earthquakes worldwide occur at plate boundaries. These earthquakes are known as interplate earthquakes. In contrast, South Carolina is located within the interior of the North American plate, far from any plate boundary. Earthquakes occuring within a plate are intraplate earthquakes. Little is known as to why intraplate earthquakes occur. The most widely accepted model is that several geologically old fault systems of varying orientation within the subsurface are being reactivated while being subjected to stress.This stress buildup may be due to the Plate Tectonic Theory. For hundreds of millions of years, the forces of continental drift have reshaped the Earth. Continental drift is based on the concept that the continents bumped into, and slid over and under each other and at some later time broke apart. Today, most people accept the theory that the Earth's crust is on the move. Most of South Carolina’s earthquakes occur in the Coastal Plain where the underlying rocks are very faulted or broken from the break-up of the plates. These cracks in the deep rocks mean that this area of the plate is weak. If pressure is exerted on the edge of the plate, some of these faults/breaks will allow the rocks to move. Faults in South Carolina have been mapped and estimated. Fault rupture is not the only cause of earthquakes. Small earthquakes may also occur near dams from water pressure and near the Appalachian Mountains. Currently, there is no reliable method for predicting the time, place, and size of an earthquake. Several areas of South Carolina regularly experience earthquakes and have experienced strong earthquakes in the past. Approximately 70% of all earthquakes in the state occur in the Coastal Plain with most clustered around three areas of the State: Ravenel-Adams Run-Hollywood, Middleton-Place-Summerville, and Bowman. There is a consensus among seismologists that where earthquakes have occurred before, they can again.The two most signifcant historical earthquakes in South Carolina were the 1886 Charleston earthquake and the 1913 Union County earthquake. The August 31, 1886 earthquake which struck in the Summerville/Charleston area is the largest event to have occurred in the southeastern U.S. and the most destructive, killing 60 people. On January 1, 1913, Union County experienced an earthquake that by today’s standards would probably be measured as a M 4.1 on the Magnitude scale. Not much is known about the cause of the Union County earthquake because of the lack of technology at the time. Earthquakes in South Carolina South Carolina’s Fault System Threat Level for South Carolina Caribbean Plate Pacifc Plate Nazca Plate Antarctica Plate Cocos Plate North American Plate Eurasian Plate South American Plate Earthquakes are probably the most frightening naturally occurring hazard encountered. Why? Earthquakes typically occur with little or no warning.There is no escape from an earthquake! While South Carolina is usually not known for earthquakes, ten to twenty earthquakes are recorded annually and two to fve earthquakes are felt each year. These earthquakes tend to be less than magnitude 3.0 on the magnitude scale and cause little damage. Destruction Based on Intensity 10 Complete destruction Cracks in walls, windows broken Things would be thrown of shelves If lying down, vibrations might be felt 5/6 4 2 South Carolina Earthquakes from 1698 to Present Charleston Earthquake of 1886 An Earthquake Today On August 31, 1886, Charleston, South Carolina, experienced the most damaging earthquake in the eastern United States. The initial shock lasted nearly one minute. The earthquake had a magnitude of 7.3 (Johnson, 1996) and was felt over 2.5 million square miles, from Cuba to NewYork, and Bermuda to the Mississippi River. Structural damage extended several hundreds of miles to cities in Alabama, Ohio, and Kentucky. At the time of the earthquake, many of the residents of Charleston thought it was a calamity that struck the entire world. Many residents were surprised when they discovered it was principally their area where the majority of severe damage occurred. Geologically, Charleston lies in one of the most seismically active areas in the Eastern United States. The seismicity in the Coastal Plain of South Carolina clusters around the cities of Summerville and Bowman, SC, known as the Middleton Place - Summerville Seismic Zone (MPSSZ). The MPSSZ seismicity appears to be occurring in two steeply dipping faults. The frst fault is the deeper, northeast-trending Woodstock Fault and the second is the shallower, northwest-trending Ashley River Fault. Recent seismic activity (November 2002; M=4.2 & 3.5) has also included an earthquake in the Atlantic Ocean of the coast of South Carolina. Currently the MPSSZ experiences between 10 to 15 magnitude 3 or less events every year. Large events, like the 1886 earthquake, have been recorded in the oral history of the area (~1600 and 13-1400's AD). Additionally, paleoseismic investigations have shown evidence for several pre-historic, liquefaction-inducing earthquakes in coastal South Carolina in the last 6000 years. If the present is the key to the past, and the past is an analog for the future, then the Charleston region can expect to experience another 1886 magnitude event in the future. (South Carolina Earthquake Educationand Preparedness, College of Charleston.) • An estimated 45,000 casualties, of which approximately 9,000 (about 20 percent) would be major injuries requiring hospitalization; fatalities would number about 900. A daytime event would cause the highest number of casualties. • Nearly 70,000 households, or about 200,000 people, would be displaced, with an estimated 60,000 people requiring short-term shelter. • Total economic losses from damage to buildings, direct business interruption losses, and damage to transportation and utility systems would exceed $20 billion. Direct economic losses due to building damages (without the business interruption losses) are estimated to exceed $14 billion. Transportation and utility systems' direct economic losses would exceed $1 billion. • About $10.9 billion in economic losses would occur in the tri-county area of Charleston, Berkeley, and Dorchester. The building damages alone would cause more than $4.2 billion in losses due to direct business interruption in the state. Loss estimates include rental income, business income, wages, and relocation expenses. • More than 250 fres would burn, primarily in the tri-county area. The lack of operational frefghting equipment and water due to the earthquake would be a major concern. • About 80 percent of urban households in the afected tri-county area would be deprived of water. It would take weeks, if not months, to restore the water systems to normal operation. • Hospitals would likely sufer signifcant building damage that could result in up to 30 hospitals out of the 108 (about 30 percent) being nonfunctional. • More than 220 schools and more than 160 fre stations would have signifcant damage. In addition, extensive damage is expected to the large inventory of relocatable school buildings. • Close to 800 bridges would be damaged beyond use, thus hampering recovery eforts. • About 63 electric power facilities (51 substations out of 380, and 12 power plants out of 53) would sufer at least moderate damage; about 300,000 households would be without power. • More than 36 million tons of debris would be generated. Results of a scientifc study commissioned by the South Carolina Emergency Management Division indicate that an earthquake today of similar intensity(7.3) and location to the one in 1886 could have the following results: Brace or replace masonry chimneys Strap down computers Secure ceiling fans and hanging light fixtures Securely fasten or relocate heavy pictures and mirrors over beds. Strengthen garages that have living space above them. Know how & where to shut off utilities Know how & where to shut off utilities Prevent rolling or tilting of refridgerators Brace water heaters Upgrade unbraced crawlspace walls (or other foundation problems) Ensure that gas appliances have flexible connections Secure cabinets to wall studs; use latches to keep doors from opening during an earthquake Strap down televisions and other expensive or hazardous electrical components Strap bookcases & shelves to walls to prevent tipping Earthquake Home Hazard Hunt Citizens with Functional Needs Recommendations for reducing earthquake hazards in your home. Citizens with disabilities and functional needs should understand the importance of being prepared for the efects of an earthquake. Unlike some disasters, normally there is no time for evacuation and citizens should shelter-in-place. Planning ahead is the key. Identifying potential hazards ahead of time can reduce the dangers of serious injury or loss of life. • Talk to neighbors, family or caregivers about how to protect your home and belongings from earthquake damage. Check for hazards in your home. Repairing deep plaster cracks in ceilings and foundations and anchoring overhead lighting will help reduce the impact of an earthquake. • Make sure that you have your supplies kit and that it is maintained. Some of the supplies that you should have in your kit include batteries for hearing aids, fashlights and similar devices, extra oxygen tanks, electrical backups for medical equipment, emergency food and water including uploads/Geographie/ sc-earthquake-guide.pdf