@article {Pham2009,
	title = {{Observations and Modeling of Rotational Signals in the P Coda: Constraints on Crustal Scattering}},
	journal = {Bulletin of the Seismological Society of America},
	volume = {99},
	number = {2B},
	year = {2009},
	month = {may},
	pages = {1315{\textendash}1332},
	abstract = {In addition to three classical components (vertical, north-south, and east-west) of ground translations recorded by a broadband seismometer, a component of earthquake induced rotational ground motions around the vertical axis is consistently measured by a ring laser sensor located in Wettzell, southeast Germany. Significant rotations around the vertical axis in the P coda of teleseismic signals are either directly visible or can be inferred through the investigation of cross correlation between the transverse component (the component that is perpendicular to the great circle connecting the earthquake and the seismometer) of translation acceleration and ring laser rotation rate. Theoretically, in spherically symmetric isotropic media, we should not observe rotational signals around the vertical axis before the onset of SH waves. Possible causes for the observed rotations in the P coda are: (1) tilt-ring laser coupling, (2) anisotropy, (3) topographic scattering, and (4) P-SH scattering in the crust. Here we show that P-SH scattering in the 3D random crust can explain the observations and allow us to constrain crustal scattering properties.},
	issn = {0037-1106},
	doi = {10.1785/0120080101},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-67649949683\&partnerID=tZOtx3y1},
	author = {Pham, N. D. and Igel, H. and Wassermann, J. and Kaser, M. and De La Puente, J. and Schreiber, U.}
}
@article {Stupazzini2009,
	title = {{Study of Rotational Ground Motion in the Near-Field Region}},
	journal = {Bulletin of the Seismological Society of America},
	volume = {99},
	number = {2B},
	year = {2009},
	month = {may},
	pages = {1271{\textendash}1286},
	abstract = {During the nineteenth and twentieth centuries observational seismologists recorded primarily the earthquake-induced translational wave field, while the rotational motion still remains poorly observed and investigated. We aim to further understand the rotational ground motion and its relation to the translational wave field, with a special emphasis on the near field, a few wavelengths away from the hypocenter, where damage related to rotational motion might need to be considered. A broad picture of the available values of rotational amplitudes and their variability is obtained by gathering most of the published data on strong rotational motion. To obtain a more detailed picture we perform a large scale 3D numerical study of a strike-slip event in the Grenoble valley where a combination of topographic, source, and site effects produces a realistic wave field. We analyzed the synthetic dataset in terms of the rotational and translational peak amplitudes and their dependence on two effects: nonlinear soil behavior and source directivity. On a soft soil deposit, we observe peak ground rotation of 1 mrad and the peak ground rotation rate of 10 mrad/sec, for an Mw 6.0 event. Those values show a strong dependence on the hypocenter location, the local site conditions, and the topographical features, inducing a variability of almost one order of magnitude in a range of distances of 20 km. Finally, we compare our numerical results in terms of peak ground velocity (PGV) versus peak ground rotation (PG${\o}mega$) with field data obtained at similar scenarios (e.g., Parkfield) by array techniques to investigate the relation between translational and rotational amplitudes expected in the near field for shallow, medium-sized earthquakes. Results of our numerical simulation fit reasonably well with those observed in past studies. Furthermore, the spatial variations of the PGV/PG${\o}mega$ ratio show a trend, which is correlated with the velocity structure of the model under study.},
	issn = {0037-1106},
	doi = {10.1785/0120080153},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-67649962349\&partnerID=tZOtx3y1},
	author = {Stupazzini, M. and De La Puente, J. and Smerzini, C. and Kaser, M. and Igel, H. and Castellani, A.}
}
