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Potential of Ocean Bottom Distributed Acoustic Sensing for Seismic Ocean Thermometry

Description: 

The ocean absorbs >90% of the excess heat and plays a key role in the climate system. However, an accurate estimate of global ocean temperature changes is still challenging. Seismic ocean thermometry (SOT) using T-wave from repeating earthquakes has proven an accurate remote-sensing method complementing existing temperature measurements. Nonetheless, current high-quality T-wave stations are sparsely distributed, limiting the spatial resolution of global SOT. Distributed acoustic sensing (DAS) can provide an affordable and scalable solution for long-term submarine array observation and therefore significantly enhance a global SOT capacity. Here we systematically investigate T-wave detectability of ocean bottom DAS (OBDAS) and explore its potential for SOT using the OOI (Ocean Observatories Initiative) OBDAS experiment offshore central Oregon as an example. During the four days, T waves from multiple distant earthquakes, most of which are missing in current catalogs (i.e., ISC), are detected at OOI DAS. To further enhance the signal-to-noise ratio, we use a curvelet-based denoising algorithm to extract the coherent T-wave from noisy data. After denoising, we explore the SOT feasibility using T waves from pseudo repeating earthquakes, which are generated using the realistic T-wave from a Mw5.2 Aleutian earthquake and noises at OOI OBDAS. Benefitting from the ultra-dense array, we find that OBDAS can use T-wave from small repeating events for SOT while data at a co-located OBS from similar magnitude events would be too noisy. Still, some other challenges (e.g., a possible temporal change of cable response to T-wave) affecting SOT awaits further studies.

Session: Understanding Earth Systems with Fiber-optic Cables

Type: Oral

Date: 4/19/2023

Presentation Time: 08:15 AM (local time)

Presenting Author: Zhichao Shen

Student Presenter: No

Invited Presentation: 

Authors