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Volcanowatch

May 13, 2004

A weekly feature provided by scientists at the Hawaiian Volcano Observatory.


Lights! Camera! Disaster!: Mixing fact and fantasy in the movies

Colossal natural disasters have been fodder for Hollywood movies long enough that we can recognize the basic recipe. A pinch of fact, a fistful of myth and exaggeration, and a large dose of spectacular special effects add up to an entertaining, but often preposterous disaster movie.

In the recent TV movie "10.5", an earthquake in the Pacific Northwest starts a chain reaction of ever-larger earthquakes propagating down the west coast, predicted to culminate in a magnitude 10.5 earthquake that will send much of California sliding off into the ocean. Luckily, an intrepid heroine saves the day by setting off nuclear devices to seal the fault and prevent the earthquake. Hard to find the pinch of fact in that storyline!

Is a magnitude-10.5 (M10.5) earthquake even possible? Theoretically, yes. Realistically, no. The strength of an earthquake depends primarily on the area of rupture, and there are no known faults anywhere near the size it would take to generate a "mega-quake" of magnitude greater than 10. The largest earthquake ever recorded was a M9.5 in 1960 on a fault almost 1,000 miles long in Chile.

One of the more amazing fantasies in the movie is the revival of the old myth that California will one day fall into the ocean - totally impossible. The ocean is not a hole that California can get swept into. In fact, southwestern California is part of the Pacific tectonic plate, as are the Hawaiian Islands. The boundary between the Pacific and North American plates is the San Andreas fault system, not the coastline. So southwestern California is riding along with the plate, as we are, northward about 46 millimeters (2 inches) per year. Unfortunately for Californians, the North American plate is moving southward, so the plates grind past each other along the San Andreas, building up stresses that are released through earthquakes.

Another fantasy is the idea that a nuclear explosion could seal a fault. People cannot prevent earthquakes from happening or stop them once they've started. Giant nuclear explosions at shallow depths won't stop an earthquake.

Every seismologist wishes he/she could, like the rebel scientist in the movie, predict the time, place, and magnitude of a future earthquake. Unfortunately, no one has that ability yet. Research into earthquake prediction continues, but, in the meantime, we can make long-range forecasts of the likelihood of earthquakes for specific locations. For example, scientists estimate that over the next 30 years the probability of a major earthquake occurring in the San Francisco Bay area is 62 percent.

Most people associate large earthquakes in the U.S. with the west coast of the mainland, but in fact the Big Island has as high a hazard from ground motion due to earthquakes as any area in the continental U.S.

The intensity of expected ground motion is based on the geology and history of earthquake activity of the region. Engineers and building-code developers use these site response models to improve the safety of structures. So while some of the most spectacular special effects in the movie had the Seattle Space Needle and the Golden Gate Bridge toppling, collapses of major public structures during an earthquake are not very likely in most of the United States.

While we can't stop earthquakes or predict exactly when they will occur, we can be prepared for them. We can minimize our risk by knowing and practicing how to stay safe during the next earthquake. For example, did you know that a doorway is no longer considered a safe place to be during the shaking? The safest place is actually under a sturdy table or desk, but even sitting next to an inside wall or lying down and holding on to a heavy piece of furniture will help reduce the likelihood of injury.

You can take simple steps to reduce earthquake damage in your home, such as securing your water heater and bolting bookshelves to the wall. http://www.earthquakecountry.info/roots/steps.html is one of many good sites on the internet that give advice on earthquake preparedness.

Activity update

Eruptive activity at Pu`u `O`o continues. The Banana flow, which breaks out of the Mother's Day lava tube a short distance above Pulama pali, has moved to within 550 yards of the coastline. Early this week a flow moved steadily toward the ocean, but stagnated on Tuesday about 400 yards from the sea cliff. Many active flows along the coastal flat made spectacular lava viewing conditions this week. There is no eruptive activity in Pu`u `O`o's crater except for sporadic minor spattering.

No earthquakes were reported felt on the island during the week ending May 13.

Mauna Loa is not erupting. The summit region continues to inflate slowly. Seismic activity remains low, with 2 earthquakes located during the past week.

Visit our website (hvo.wr.usgs.gov) for daily volcano updates and nearly real-time earthquake information. skip past bottom navigational bar


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Updated: May 17, 2004 (pnf)