Island Earthquake Prone? Earthquakes Exactly Two Years

¶ … ISLAND EARTHQUAKE PRONE?

Earthquakes

Exactly two years ago, a 3.9 magnitude earthquake struck off the coast of Long Island and New Jersey and caused no significant damage (Perez-Pena, 2010). In contrast, the largest quake on record (5.5) for the New York City area occurred in 1884, could be felt as far away as Ohio, Virginia, and Maine, and damage was limited to chimneys and cracked walls (USGS, 2009a). Strong earthquakes rarely happen to this area and those over magnitude 5 only occur about once every hundred years, but in terms of quake activity the area ranks fourth behind Los Angeles, San Francisco, and Seattle (Groves, 2001). To understand the seismic hazards of living on Long Island, where I live, the relevant information provided by the U.S. Geological Survey website will be used assess the relative risk for this area.

Major Fault Lines Near Long Island

The primary fault line in the eastern New York area is the Ramapo Fault that runs for 70 miles between Morris County, New Jersey and Bear Mountain, New York, and roughly parallel to the Hudson River (Groves, 2001). Another active fault, the 125th Street Fault, runs through New York City. If the seismic hazard map for New York State is examined, the areas of greatest risk are along the Ramapo and 125th Street fault lines and along the St. Lawrence Seaway south of Montreal, Canada (USGS, 2009b). On Long Island, the risk diminishes the further away from New York City a person goes, such that the eastern half of the island has little earthquake risk. For example, the 2% seismic hazard over 50 years is 0.16 to 0.18 g (yellow/green) on the western end of Long Island and diminishes to 0.8 to 0.10 g (light blue) at the eastern 1/3 of the island.

Relative Risk

There are clearly hot zones in terms of the frequency of earthquakes across the continental United States (USGS, 2012a). The distribution of earthquakes in the lower 48 for the past week, reveal frequent, mild earthquakes along the west coast/San Andreas Fault line. A number of minor quakes occurred over the past week just east of the Sierra Nevada Mountains, across Nevada and Utah, and along the Rocky Mountain chain between Idaho and Wyoming/Montana. In the central part of the U.S., a few recent quakes hit Oklahoma northeast of the Meers Fault, Arkansas east of the Ozarks, southwest Illinois, and along the New Madrid Fault north of Memphis Tennessee (USGS, 2011a).

Globally, one of the most active regions for seismic activity is the Ring of Fire, encircling the Pacific Ocean from New Zealand, to Indonesia, Japan, Aleutian Islands, along the west coast of North America, and south to Peru (USGS, 2012b). This Ring of Fire represents the boundary of the Pacific Plate, a tectonic plate forming the floor of the Pacific Ocean. One of the more recent earthquakes to be recorded on the world map is a 5.0 magnitude quake that occurred on May 14, 2012 at 12:36 PM local time, with an epicenter located 20 km southeast of Miyazaki, Japan. Other active areas around the globe include the Persian Gulf area and Northern India (Himalayan Mountains).

If the seismic hazard maps for New York (USGS, 2009b) and California (USGS, 2009c) are compared, it quickly becomes obvious that there is a significant difference in quake risk levels between the two states. While California is mostly yellow (moderate/high) and red (high risk), New York is mostly blue (low risk).

San Francisco probably has a comparable climate to Long Island, but moving there would mean moving to a red area in terms of seismic hazard risk (USGS, 2009c). However, the relative risk may be similar between the two regions because building codes in San Francisco are designed to minimize risk from earthquakes and building codes on Long Island have probably ignored earthquake risk. For the right job opportunity, the difference in risk would probably not be enough to prevent most people from making the move.

Preparedness

If a job opportunity in San Francisco was too hard to resist, a number of steps can be taken to maximize safety during earthquakes (USGS, 2009d). For example, choosing a newer building to live in would tend to ensure it has been designed to meet the most recent building codes. Once moved in, reading tips on the USGS website for preparedness reveals what to do and not do during an earthquake, such as turning on and off utilities, purchasing emergency food and water supplies, and where the safe places are inside and outside a structure.

Recent Devastation

Several of the most devastating earthquakes ever recorded have occurred very recently (USGS, 2011b). On January 12, 2010, a magnitude 7.0 earthquake struck Haiti, killing over 300,000 people and destroying close to 100,000 homes. On May 12, 2008, a 7.9 magnitude earthquake struck Eastern Sichuan, China, killing 90,000 people and injuring 300,000 others. Nearly 5 million people ended up homeless. Given these statistics, it seems obvious that scientists are unable to accurately predict earthquakes, let alone prevent them from occurring.