Changes in Ground level

During earthquakes, blocks of earth shift relative to one another. This may result in changes in ground level, base level, the water table, and high-tide marks. Particularly large shifts have been recorded from some of the historically large earthquakes, such as the magnitude 9.2 Alaskan earthquake (1964) and the Sumatra earthquake (2004). In 1964 an area more than 600 miles (1,000 km) long in south central Alaska recorded significant changes in ground level, including uplifts of up to 12 yards (11 m), downdrops of more than two yards (2 m), and lateral shifts of several to tens of yards. Uplifted areas along the coastline experienced dramatic changes in the marine ecosystem—clam banks were suddenly uplifted out of the water and remained high and dry. Towns built around docks were suddenly located many yards above the convenience of being at the shoreline. Downdropped areas experienced different effects—forests that relied on freshwater for their root systems suddenly were inundated by salt water and were effectively "drowned." Populated areas located at previously safe distances from the high tide (and storm) line became prone to flooding and storm surges, and had to be relocated.

Areas far inland also suffered from changes in ground level—when some were uplifted by many tens of feet (~10 m), the water table recovered to a lower level relative to the land surface, and soon became out of reach of many water wells, which had to be redrilled. Changes in ground level, although seemingly a minor hazard associated with earthquakes, are significant and cause a large amount of damage that may cost millions of dollars to mitigate.

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The Basic Survival Guide

The Basic Survival Guide

Disasters: Why No ones Really 100 Safe. This is common knowledgethat disaster is everywhere. Its in the streets, its inside your campuses, and it can even be found inside your home. The question is not whether we are safe because no one is really THAT secure anymore but whether we can do something to lessen the odds of ever becoming a victim.

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