Geologists report that risks of big earthquakes may be underestimated

Dec 12, 2013 by Bob Yirka report
Aerial photo of the San Andreas Fault in the Carrizo Plain, northwest of Los Angeles. Credit: Wikipedia.

(Phys.org) —Several geologists from around the world are presenting a case for missing or underreported earthquakes at this year's American Geophysical Union Fall meeting being held in San Francisco. They suggest that faulty or missing data from before 1900 might be leading to underestimations of the numbers of big quakes to expect in the future.

One such speaker is Susan Hough—she's with the US Geological Survey. She reported to those in attendance that prior to the invention and implementation of seismometers, evidence of earthquakes could be found only through earlier anecdotal writings. But such records, she notes, tended to underestimate the size of the quakes being described. Suddenly, she says, after 1900, earthquakes started getting bigger.

They didn't get bigger of course, what she meant was that the size perception of earlier earthquakes had been underestimated—many might not be in the historical record at all. Part of the problem, she explained, was that until fairly recently, it was believed that all earthquakes of a certain large size, produced tsunami's, which of course tend to show up in written records.

The problem with relying on underestimated data, she also explained, is that it causes modern day planners to underestimate what is likely to happen in the future. She notes that one example was that of the Kamchatka quake that occurred in 1841 in Russia. The record shows it to have been an 8.3 magnitude quake, but closer scrutiny suggests that estimate was wrong—reports of a tsunami in Hawaii at the time, indicate it was almost certainly much stronger, perhaps as high as magnitude 9.2.

Roger Musson of the British Geological Survey concurred, noting that people were taken almost completely by surprise when the Fukushima quake struck in 2011. But, looking back, it's clear that one almost exactly like it struck in the same place back in the 9th century. He noted virtually the same thing can be said for the Haiti quake that struck in 2010.

The overall point the geologists are trying to make is that it's likely that the reported numbers and sizes of quakes described in the past are in error, and thus, using them as guides for the future is both risky and ill-advised as the lives of people in many at-risk areas may be depending on more accurate assessments.

Explore further: 6.5 magnitude quake off Alaska's Aleutian Islands

More information: fallmeeting.agu.org/2013/

Related Stories

Are large earthquakes linked across the globe?

Aug 02, 2012

The past decade has been plagued with what seems to be a cluster of large earthquakes, with massive quakes striking Sumatra, Chile, Haiti and Japan since 2004. Some researchers have suggested that this cluster has occurred ...

Aftershock: 6.2 quake off British Columbia coast

Oct 30, 2012

(AP)—The U.S. Geological Survey says a magnitude 6.2 earthquake off the west coast of Canada on Monday night is an aftershock of the magnitude 7.7 quake that struck Saturday night. A geophysicist says the agency had no ...

Are we living in an age of giant quakes?

Apr 08, 2011

Searching for patterns in the occurrence of large magnitude earthquakes after a succession of large tremors -- surpassed by the recent magnitude-9.0 quake in Japan -- has researchers wondering if the amount ...

Moderately strong quake hits eastern Indonesia

Sep 08, 2012

(AP)—A moderately strong earthquake has hit eastern Indonesia, causing panic among residents, but there were no immediate reports of damage or injuries. No tsunami warning was issued.

Recommended for you

NASA gets two last looks at Tropical Cyclone Jack

18 hours ago

Tropical Cyclone Jack lost its credentials today, April 22, as it no longer qualified as a tropical cyclone. However, before it weakened, NASA's TRMM satellite took a "second look" at the storm yesterday.

Krypton used to accurately date ancient Antarctic ice

Apr 21, 2014

A team of scientists has successfully identified the age of 120,000-year-old Antarctic ice using radiometric krypton dating – a new technique that may allow them to locate and date ice that is more than ...

Taking the pulse of mountain formation in the Andes

Apr 21, 2014

Scientists have long been trying to understand how the Andes and other broad, high-elevation mountain ranges were formed. New research by Carmala Garzione, a professor of earth and environmental sciences ...

User comments : 0

More news stories

60% of China underground water polluted: report

Sixty percent of underground water in China which is officially monitored is too polluted to drink directly, state media have reported, underlining the country's grave environmental problems.

Florida is 'Ground Zero' for sea level rise

Warm sunshine and sandy beaches make south Florida and its crown city, Miami, a haven for tourists, but the area is increasingly endangered by sea level rise, experts said Tuesday.

NASA gets two last looks at Tropical Cyclone Jack

Tropical Cyclone Jack lost its credentials today, April 22, as it no longer qualified as a tropical cyclone. However, before it weakened, NASA's TRMM satellite took a "second look" at the storm yesterday.

In the 'slime jungle' height matters

(Phys.org) —In communities of microbes, akin to 'slime jungles', cells evolve not just to grow faster than their rivals but also to push themselves to the surface of colonies where they gain the best access ...

Robot scouts rooms people can't enter

(Phys.org) —Firefighters, police officers and military personnel are often required to enter rooms with little information about what dangers might lie behind the door. A group of engineering students at ...

New alfalfa variety resists ravenous local pest

(Phys.org) —Cornell plant breeders have released a new alfalfa variety with some resistance against the alfalfa snout beetle, which has ravaged alfalfa fields in nine northern New York counties and across ...