Early warning systems underestimate magnitude of large earthquakes

Jan 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: Tropical depression 21W forms, Philippines under warnings

add to favorites email to friend print save as pdf

Related Stories

And now, the volcano forecast

Oct 22, 2014

Scientists are using volcanic gases to understand how volcanoes work, and as the basis of a hazard-warning forecast system.

Whither the Internet of Things?

Oct 09, 2014

The Internet of Things – IoT – it's a phrase we hear more and more, often hyped, often discussed seriously in the context of cloud computing but definitely a buzz phrase. Put simply, it is the connection of "smart" (and ...

Advancing the state-of-the-art in seismic science

Sep 30, 2014

Data received from seismic monitoring stations coupled with information rapidly shared via smartphones and the Internet by those who experienced the south Napa temblor is serving to advance scientists' understanding ...

Recommended for you

Better forecasts for sea ice under climate change

Nov 25, 2014

University of Adelaide-led research will help pinpoint the impact of waves on sea ice, which is vulnerable to climate change, particularly in the Arctic where it is rapidly retreating.

User comments : 0

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.