NEHRP Clearinghouse

Title
Rotational Seismology: AGU Session, Working Group, and Website.
File
PB2008104454.pdf
Author(s)
Lee, W. H. K.; Igel, H.; Todorovska, M. I.; Evans, J. R.
Source
January 2007, 7 p.
Identifying Number(s)
USGS-OFR-2007-1263
Abstract
Seismology is based primarily on the observation and modeling of three-component translational ground motions. Nevertheless, theoretical seismologists (e.g., Aki and Richards, 1980, 2002) have argued for decades that the rotational part of ground motions should also be recorded. It is well known that standard seismometers are quite sensitive to rotations and therefore subject to rotation-induced errors. The paucity of observations of rotational motions is mainly the result of a lack, until recently, of affordable rotational sensors of sufficient resolution. Nevertheless, in the past decade, a number of authors have reported direct observations of rotational motions and rotations inferred from rigid-body rotations in short baseline accelerometer arrays, creating a burgeoning library of rotational data. For example, ring laser gyros in Germany and New Zealand have led to the first significant and consistent observations of rotational motions from distant earthquakes (Igel et al., 2005, 2007). A monograph on Earthquake Source Asymmetry, Structural Media and Rotation Effects was published recently as well by Teisseyre et al. (2006). Measurement of rotational motions has implications for: (1) recovering the complete ground-displacement history from seismometer recordings; (2) further constraining earthquake rupture properties; (3) extracting information about subsurface properties; and (4) providing additional ground motion information to earthquake engineers for seismic design.
Keywords
; Structural strong motion; Rotational seismology; Teleseismic motions; Free-field strong motion; Working group