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Merits of Installing Environmental Sensors at Seismic Stations

Description: 

The EarthScope Transportable Array (TA) in Alaska is a unique seismic network because most stations have co-located pressure, temperature, and wind sensors. We will point out some merits of having such co-located environmental sensors and stress their importance.

First, the combined analysis of seismic and pressure data allows us to separate two types of seismic noise; one is the ordinary seismic noise, consisting of propagating body and surface waves, and the other is ground deformation caused by the local pressure loading. This loading effect can be confirmed from two pieces of evidence; the coherence between seismic and pressure data and the phase difference between pressure and vertical seismic displacement. By selecting data from a high-pressure range, we can apply the compliance method and derive shallow elastic structures for a depth range of about 50-100m. Second, the combined analysis of temperature and seismic noise allows us to identify the major effects of near-surface melting in summer, primarily in the permafrost area. Some stations show a thousand-fold increase in horizontal noise in summer at 0.01-0.03 Hz in comparison to the frozen state in winter. This anomalous horizontal noise can be seen at low frequencies (< 0.1 Hz) and is most likely related to the tilt effects as its amplitude increases towards lower frequencies. Third, the way the noise level returns to the frozen, low-noise state after the major melting varies from station to station. For many stations, this return occurs well after the surface temperature becomes negative in September or October. Some stations require time until March of the following year to return to the frozen state. These data suggest that the melt layer remains at depth for a long time even after surface temperature drops below freezing, creating a sandwiched molten layer between the developing ice from the surface and the underlying permafrost ice. These results and perspectives have been gained because of the availability of co-located seismic and environmental data and underscore the importance of installing environmental sensors at seismic stations.

Session: ESC-SSA Joint Session: Climate Change and Environmental Seismology - I

Type: Oral

Date: 5/3/2024

Presentation Time: 03:00 PM (local time)

Presenting Author: Toshiro

Student Presenter: No

Invited Presentation: 

Authors