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: New detector sniffs out origins of methane

add to favorites email to friend print save as pdf

Related Stories

IOC defends Rio legacy amid green protests

19 hours ago

Ecological protests on Saturday dogged the final day of an International Olympic Committee executive board meeting in Rio as green campaigners slated the choice of a nature reserve to hold the golf event ...

Recommended for you

New detector sniffs out origins of methane

14 hours ago

Methane is a potent greenhouse gas, second only to carbon dioxide in its capacity to trap heat in Earth's atmosphere for a long time. The gas can originate from lakes and swamps, natural-gas pipelines, deep-sea ...

The tides they are a changin'

19 hours ago

Scientists from the University of Southampton have found that ocean tides have changed significantly over the last century at many coastal locations around the world.

Lightning plus volcanic ash make glass

Mar 03, 2015

In their open-access paper for Geology, Kimberly Genareau and colleagues propose, for the first time, a mechanism for the generation of glass spherules in geologic deposits through the occurrence of volcan ...

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.