Earthquake Hazards Program
(alphabetical throughout, excepting first author here)
Rotation of the monument to George Inglis (erected in 1850 at Chatak, India) was observed by Oldham (1899) after the 1897 Great Shillong earthquake of 1897. This monument had the form of an obelisk rising over 60 feet high from a base of 12 square feet. During the earthquake, the topmost 6-foot section was broken off and fell to the south and the next 9-foot section was thrown to the east. The rotated remnant is about 20 feet in length [Photo from Oldham, R.D. (1899). Report on the Great Earthquake of 12th June 1897. Mem. Geol. Survey India, vol. 29.] (from figure 1).
A successful workshop titled “Measuring the Rotation Effects of Strong Ground Motion” was held simultaneously in Menlo Park and Pasadena via video conference on 16 February 2006. The purpose of the Workshop and this Report are to summarize existing data and theory and to explore future challenges for rotational seismology, including free-field strong motion, structural strong motion, and teleseismic motions. We also forged a consensus on the plan of work to be pursued by this international group in the near term.
At this first workshop were 16 participants in Menlo Park, 13 in Pasadena, and a few on the telephone. It was organized by William H. K. Lee and John R. Evans and chaired by William U. Savage in Menlo Park and by Kenneth W. Hudnut in Pasadena. Its agenda is given in the Appendix.
This workshop and efforts in Europe led to the creation of the International Working Group on Rotational Seismology (IWGoRS), an international volunteer group providing forums for exchange of ideas and data as well as hosting a series of Workshops and Special Sessions.
IWGoRS created a Web site, backed by an FTP site, for distribution of materials related to rotational seismology. At present, the FTP site contains the 2006 Workshop agenda (also given in the Appendix below) and its PowerPoint™ presentations, as well as many papers (reasonable-only basis with permission of their authors), a comprehensive citations list, and related information. Eventually, the Web site will become the sole authoritative source for IWGoRS and shared information:
With contributions from various authors during and after the 2006 Workshop, this Report proceeds from the theoretical bases for making rotational measurements (Graizer, Safak, Trifunac) through the available observations (Huang, Lee, Liu, Nigbor), proposed suites of measurements (Hudnut), a discussion of broadband teleseismic rotational seismology (Cochard, Igel, Schreiber, Teisseyre, Wassermann, Majewski), sensor-calibration issues (Evans, Hutt), and finally the summary and conclusions (Savage).
As a direct result of the 2006 Workshop and the formation of IWGoRS, we held a special session at the Fall 2006 AGU meeting (convened by H. Igel, W.H.K. Lee, and M.I. Todorovska). Currently, the first formal Workshop of the IWGoRS is being organized by W.H.K. Lee, M. Çelebi, and M. I. Todorovska with sponsorship by the USGS and assistance from many others; this First International Workshop on Rotational Seismology and Engineering Applications will be held in September 2007 at Menlo Park, California (http://pubs.usgs.gov/of/2007/1144/).
The following summarizes presentations and discussions during and shortly after the informal Workshop of February 2006.
Download this report as a 20-page PDF file (of2007-1145.pdf; 304 kB).
For questions about this report, contact John Evans.
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