[iris-bulk] Rotational Seismology at the Fall AGU Meeting in San Francisco (H. Igel, W. H. K. Lee, and M. I. Todorovska, Conveners)

[IRIS]

Earthquake seismology and engineering are based primarily on the  
observation and modeling of three-component translational ground  
motions, despite the fact that rotational earthquake effects have  
been observed after large earthquakes for centuries, and both  
translational and rotational displacements are required in defining  
motions of a rigid body (six degrees of freedom, 6DOF).  The paucity  
of observations of rotational motions is mainly due to the high cost  
and insufficient accuracy of earlier rotation sensors.

In the past several years development of large ring laser gyros have  
led to the first significant and consistent observations of  
rotational motions generated by large earthquakes in the far field  
(at sites in Germany, New Zealand and southern California), and the  
results agree well with the theory.  However, using far less  
expensive gyros, puzzling results have been obtained from small  
earthquakes in the near field.  If recent measurements of large  
rotations observed for small earthquakes at short distances in Japan  
and Taiwan are confirmed, then strong-motion results based solely on  
translational motions are inadequate and many conclusions derived to  
date may be seriously in error.

Accurate measurements of rotational motions will make it possible to  
(1) recover the complete displacement history from seismometer  
recordings; (2) further constrain rupture parameters during  
earthquakes; (3) extract subsurface properties of fault zones; and  
(4) provide important information to earthquake engineers for safer  
design of structures.

On Tuesday, 12 December, there will be an oral session on rotational  
seismology beginning at 10:20, a luncheon starting at 12:30, and a  
poster session starting at 13:40 PST (UTC-8), as detailed in the  
attached file.  The luncheon will include the inauguration of the  
International Working Group on Rotational Seismology (IWGoRS), which  
aims to:  (1) promote investigations of all aspects of rotational  
motions in seismology and earthquake engineering, as well as their  
implications; and (2) to share experience, data, software, and  
results in an open Web-based environment.  Further information can be  
found at www.rotational-seismology.org.

We invite you to attend the oral and poster sessions on rotational  
seismology as well as the Inauguration Luncheon.

We are experimenting with a new approach for establishing an  
international working group.  Details about the AGU sessions and the  
provisional Charter are given in the attached file  
(Rotational_Seismology-Sessions_and_Charter.pdf), and everyone is  
welcome to join IWGoRS.

If you are interested in attending the Inauguration Luncheon on 12  
December (total cost: $30), please send an email to Willie Lee  
(lee at usgs.gov) by 13 November so that he can make the restaurant  
reservation for you.

Best regards,

Willie Lee (on behalf of the conveners).


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