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.