Earthquake induced rotational ground motions

Theoretical seismologists have argued for decades that – in addition to translations and strains – rotations should also be measured. The problem so far had been that instruments – particularly mechanically based sensors – did not provide the required resolution for broadband seismology. In a previous study we could demonstrate for the first time that optical sensors based on ring laser technology are capable of measuring seismically induced rotational motions as expected from theory. In addition, we could show that collocated recordings of rotations and translations contain additional information not present in standard three-component seismometer recordings.  This suggests that seismology has a new observable that is worth exploring systematically. In this project we propose (1) to process and model the novel observations and map out potential fields of applications in wave propagation, earthquake rupture, and earthquake engineering problems; (2) to develop standards and infrastructure with which rotational observations can be disseminated and used efficiently in line with other seismological waveform data; and (3) to carry out tests with “low”-resolution mobile rotation sensors and test their fitness for field studies (e.g., close to seismic sources or at volcanoes).