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Updating the Caltech Millkan Shaker for time-lapse seismic imaging in Southern California

Yuling Zhang, Ethan F. Williams, Valere R. Lambert, & Zhongwen Zhan

Published August 16, 2019, SCEC Contribution #9904, 2019 SCEC Annual Meeting Poster #046

Ambient noise interferometry has been invaluable in shallow subsurface imaging. However, in Southern California, rapidly evolving noise sources can lead to spurious velocity changes, posing substantial challenges for time-lapse investigations such as hydrological monitoring. In 1972, an eccentric mass shaker was installed on the roof of Millikan Library on the Caltech campus which has historically been used for forced vibration testing of the building. This shaker has the potential to be a repeatable, tunable seismic source capable of creating surface waves detectable throughout Southern California and as far as the US-Mexican border. In tandem with the newly-established Pasadena distributed acoustic sensing (DAS) array, the Millikan Shaker provides an opportunity to reliably image the subsurface with unprecedentedly high spatial and temporal resolution. Here we will report our ongoing work in upgrading the Millikan Shaker as a customizable active source for imaging in the San Gabriel Valley.

Zhang, Y., Williams, E. F., Lambert, V. R., & Zhan, Z. (2019, 08). Updating the Caltech Millkan Shaker for time-lapse seismic imaging in Southern California. Poster Presentation at 2019 SCEC Annual Meeting.

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