Early warning systems underestimate magnitude of large earthquakes

January 28, 2009

Scientists seek to create reliable early warning systems that accurately estimate the magnitude of an earthquake within the first seconds of rupture. In this paper published by the Bulletin of the Seismological Society of America, authors S. Murphy of University College Dublin, Ireland and S. Nielsen of the Instituto Nazionale di Geofisica e Vulcanologia, Roma, Italy look at the idea that an earthquake's final size can be determined during its initiation, rather than something that only becomes apparent at the end of the rupture.

They found that, while this may be true over a small range of earthquake sizes, it is unlikely to hold for the larger magnitudes, limiting its applicability for early warning systems.

Alternatively, the authors found that rapid magnitude estimation could be better explained in terms of what seismic stations capture of an earthquake in a few seconds. This section is generally quite large and is dependent on the relative position of the station to the fault. Therefore using a number of seismic stations around an earthquake fault, as is the case in early warning systems, the size of the earthquake can be quickly estimated.

This explanation shows a scaling between ground motion and final earthquake size similar to that observed from seismograms. The authors found that this relationship breaks down for very large earthquakes, i.e. earthquakes with a magnitude greater than 6.5. In these cases, the seismic stations no longer capture the edges of the fault in a few seconds due to the large area of the fault. When this happens, the authors suggest that early warning systems which use the peak ground displacement technique for estimating earthquake size, shall underestimate the size of the earthquake.

Source: Seismological Society of America

Explore further: Social engagement aids disaster preparedness

Related Stories

Social engagement aids disaster preparedness

July 8, 2015

Community participation and strong social networks can aid preparedness to natural disaster such as tsunamis in vulnerable regions, shows new research conducted in the south of Thailand.

Professor calls for national earthquake early warning system

October 3, 2013

(Phys.org) —Richard Allen, Director of Berkeley's Seismology Laboratory and Professor of Earth and Planetary Sciences is calling for the installation of a national early warning system to alert people to an impending earthquake. ...

Recommended for you

Global index proposed to avoid delays on climate policies

August 4, 2015

Professor David Frame, Director of Victoria's Climate Change Research Institute (CCRI), has co-authored a paper published today in the high profile international scientific journal Nature Climate Change. The paper argues ...

Study calculates the speed of ice formation

August 3, 2015

Researchers at Princeton University have for the first time directly calculated the rate at which water crystallizes into ice in a realistic computer model of water molecules. The simulations, which were carried out on supercomputers, ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.