US scientists unveil new earthquake tracking system
From: physorg.com
In a presentation at the annual meeting of the American Geophysical Union, researchers revealed a method which combines geological records with GPS tracking to help assess earthquake risk.
"This is the most realistic model to date," said Kaj Johnson, a geophysicist from the University of Indiana. "This is something that people have been asking for years now - it's the next step."
Earthquake probability assessment requires accurate determination of how fast a fault moves. Prior to the advent of GPS technology, scientists relied solely on paleoseimology, a complex method of digging trenches along fault lines and mapping the signatures of past earthquakes over thousands of years.
Now, the earth's movements are measured down to the millimeter with GPS antennae secured into bedrock.
"People say 'let's compare the rates of fault movement from GPS to rates of fault movement from geological studies," said Paul Segall, Geophysicist from Stanford University and co- author of the study.
"But it's as if you're measuring different parts of the same thing with different tools. The discrepancy can be quite big."
Segall and Johnson's model weds all available data about the way any given fault moves, and takes into account that fault-slippage rates vary over time. Time dependence is important because GPS doesn't measure fault slippage directly but how quickly points on the earth's surface are moving.
Scientists then fit this GPS data into mathematical models to estimate the rate of fault slip.
"Because of the time dependant rate, your estimate depends on where you are in the earthquake cycle," said Segall. "If the model doesn't take that into account, you will get a different slip rate."
Using their new system, the researchers found the slip rates from GPS tracking and the geological record to be relatively consistent for the San Francisco bay area, which was reduced to rubble by a quake in 1906.
But in other tectonically active regions of China and Taiwan, there are large discrepancies between the data. The researchers want to use their time-dependent model to scrutinize these faults to reconcile the data.
"There is debate within the scientific community about how fast the faults are slipping in Tibet and China," said Johnson.
"This model can better resolve those discrepancies between the data on modern surface velocities and what the geologists say has happened over time."
But Johnson stressed that this new methodology is by no means a crystal ball. "We are not talking about short-term forecasting at all," he said. "But this type of approach is very helpful for long-term probability forecasting."
In a presentation at the annual meeting of the American Geophysical Union, researchers revealed a method which combines geological records with GPS tracking to help assess earthquake risk.
"This is the most realistic model to date," said Kaj Johnson, a geophysicist from the University of Indiana. "This is something that people have been asking for years now - it's the next step."
Earthquake probability assessment requires accurate determination of how fast a fault moves. Prior to the advent of GPS technology, scientists relied solely on paleoseimology, a complex method of digging trenches along fault lines and mapping the signatures of past earthquakes over thousands of years.
Now, the earth's movements are measured down to the millimeter with GPS antennae secured into bedrock.
"People say 'let's compare the rates of fault movement from GPS to rates of fault movement from geological studies," said Paul Segall, Geophysicist from Stanford University and co- author of the study.
"But it's as if you're measuring different parts of the same thing with different tools. The discrepancy can be quite big."
Segall and Johnson's model weds all available data about the way any given fault moves, and takes into account that fault-slippage rates vary over time. Time dependence is important because GPS doesn't measure fault slippage directly but how quickly points on the earth's surface are moving.
Scientists then fit this GPS data into mathematical models to estimate the rate of fault slip.
"Because of the time dependant rate, your estimate depends on where you are in the earthquake cycle," said Segall. "If the model doesn't take that into account, you will get a different slip rate."
Using their new system, the researchers found the slip rates from GPS tracking and the geological record to be relatively consistent for the San Francisco bay area, which was reduced to rubble by a quake in 1906.
But in other tectonically active regions of China and Taiwan, there are large discrepancies between the data. The researchers want to use their time-dependent model to scrutinize these faults to reconcile the data.
"There is debate within the scientific community about how fast the faults are slipping in Tibet and China," said Johnson.
"This model can better resolve those discrepancies between the data on modern surface velocities and what the geologists say has happened over time."
But Johnson stressed that this new methodology is by no means a crystal ball. "We are not talking about short-term forecasting at all," he said. "But this type of approach is very helpful for long-term probability forecasting."
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