The DAS array
The continuous data we use were collected by the Penn State FORESEE (Fiber-Optics For Environment Sensing) array of underground telecommunication fiber optic cables. The DAS array had a total of 2137 sensors with a 10 m gauge length and 2 m channel spacing. The continuous strain rate measurements are sampled at 500 Hz. We downsampled the data to 250 Hz considering the efficiency in terms of computation and storage. Owing to the unexpected power disruptions, there are no recordings between March 16 – April 15 and May 06 – 26. We analyzed seismic noise variation of 21 weekdays at seven distinct time periods (3 days for each group) from March 3 – June 10, 2020, covering the normal spring semester, spring break, quarantine after the stay-at-home order was issued and the gradual relaxation of the COVID-19 measures.
Our DAS array, which is located at the biggest institution in the town, Penn State University, offers opportunities to explore the social response at city-block scales to Pennsylvania’s progressive lockdown measures that rely on voluntary community action. Penn State University was closed after spring break on March 18, 2020, and all the residents were required to stay at home, except for essential movements according to the statewide stay-at-home order from April 1, 2020. The social activities started to recover after the official relaxation (designated Phase Yellow/Green) on May 27, 2020.