Earth’s Rock and Roll: Rotational Motions in Seismology

Heiner Igel wearing a white button up shirt and glasses

Dr. Heiner Igel
Professor of Seismology – Ludwig-Maximilians University of Munich
Department of Earth and Environmental Sciences
Host: Dr. Kim Olsen

Wednesday, October 5, 2022
1 pm – CSL 422 or via zoom

6C point measurements (i.e., three components of translations, three components of rotations) act like a classic seismic array with 3C sensors (thus interesting particularly in situations in which multiple sensors are difficult to install such as volcanoes, seafloor, boreholes, cities, buildings, planetary objects, etc).  6C data allow the estimation of phase velocities, propagation direction (even in anisotropic media), the separation of wave types, the tracking of seismic sources, the estimation of local subsurface structure, and the removal of tilt-contamination in classic seismometers. In addition, gradient-related observations (strain, rotation) are substantially more sensitive to near receiver structure (relevant for monitoring). In this talk we will report recent progress in applying these hitherto mostly theoretical concepts to real 6C observations including the ROMY ring laser in the Geophysical Observatory Munich as well as data recorded with the broadband rotation sensor BlueSeis-3A. Specific applications include 1) the determination of 1D local velocity structure in urban areas from ambient noise for site characterization, 2) tracking seismic energy generated by cars, 3) estimating source direction at Stromboli volcano, and 4) observing prestress-induced velocity changes in bridges. We also (5) report on the estimation of a rotational low velocity model for planet Earth serving as a target for instrumentation development.