New model to predict earthquake behaviour
6 Jun 2012 by Evoluted New Media
Scientists have taken a step towards understanding how earthquakes develop thanks to a new computer model that closely mimics a fault’s seismic and aseismic behaviour.
Researchers from the California Institute of Technology (Caltech) have modelled Parkfield, an active region of the San Andreas Fault which produces magnitude 6 earthquakes on average every 20 years. The model may be used to forecast the range of potential earthquakes on the fault segment, and to further assess seismic hazard and improve building design.
“Previous research has mostly either concentrated on the dynamic rupture that produces ground shaking or on long periods between earthquakes, which are characterised by slow tectonic loading and associated slow motions – but not on both at the same time,” said Nadia Lapusta, professor of mechanical engineering and geophysics.
“In our study, we model the entire history of an earthquake-producing fault and the interaction between the fast and slow deformation phases.”
Sylvain Barbot – lead author of the study published in Science – said the method assimilates geologic, seismologic and geodetic data surrounding a seismic fault to form a physical model of the cycle of earthquakes that has a predictive power.
Using the model they were able to create a series of earthquakes ranging from magnitude 2 to 6, producing fault slip before, during and after the quake that closely matched the behaviour observed in the past 50 years.
“Our model explains some aspects of the seismic cycle at Parkfield that had eluded us, such as what causes changes in the amount of time between significant earthquakes and the jump in location where earthquakes nucleate,” Barbot said.
The paper also shows that a physical model of fault-slip evolution, based on laboratory experiments that measure how rock material deform in the fault core, can explain many aspects of the earthquake cycle,
“Earthquake science is on the verge of building models that are based on the actual response of the rock materials as measured in the lab – models that can be tailored to reproduce a broad range of available observations for a given region,” said Lapusta. “This implies we are getting close to understanding the physical laws that govern how earthquakes nucleate, propagate and arrest.”
