GPS, satellite data can shorten earthquake response times

GPS and satellite data can be used as tools to improve reaction time to deadly earthquakes, scientists say.
Researchers from the University of Iowa, along with scientists from United States Geological Survey (USGS), found that Global Positioning System (GPS) and satellite data can be used in a real-time, coordinated effort to fully characterise a fault line within 24 hours of an earthquake, ensuring that aid is delivered faster and more accurately than ever before.
Researchers used GPS and satellite measurements from the magnitude 6.0 South Napa, California earthquake on August 24, 2014, to create a three-dimensional map of how the ground surface moved in response to the earthquake.

The map was made without using traditional rapid response instruments, such as seismometers, which may not afford the same level of detail for similar events around the globe.
"By having the 3D knowledge of the earthquake itself, we can make predictions of the ground shaking, without instruments to record that ground shaking, and then can make estimates of what the human and infrastructure impacts will be - in terms of both fatalities and dollars," said Iowa Earth and Environmental Sciences assistant professor William Barnhart.
To accurately map the South Napa earthquake for this study, Barnhart and a team of researchers created a complex comparison scenario.

They first used GPS and satellite readings to measure the very small- millimetre-to-centimetre-sized-displacements of the ground's surface that were caused by the earthquake.

They fed those measurements into a mathematical equation that inverts the data and relates how much the ground moved to the degree of slip on the fault plane. Slip describes the amount, timing, and distribution of fault plane movement during an earthquake.
This allowed the group to determine the location, orientation, and dimensions of the entire fault without setting foot on the ground near the earthquake.
The mathematical inversion gave the researchers predictions of how much the ground might be displaced, and they compared those results to their initial estimations, bit by bit, until their predictions and observations matched.

The resulting model is a 3D map of fault slip beneath the Earth's surface. The entire procedure takes only a few minutes to complete.
The study is published in the Seismological Research Letters journal.