Distance between Terra15’s DAS Interrogator and the earthquake swarm in Wagin, Western Australia
Terra15 continues tracking rare earthquake swarm in Western Australia using DAS
This article is a follow up to our original post in early January titled “Terra15 detects first West Australian earthquake of 2022 with DAS system over 180km away” as significant changes have occurred following the event.
The Earthquakes detected by the Treble DAS (Distributed Acoustic Sensing) interrogator in early January appeared to be precursors followed by a main event and aftershocks. However, in the following weeks we have seen the situation evolve into a rare geophysical occurrence called an “earthquake swarm”.
Earthquake swarms can be defined as a series of seismic events contained within a relatively small area and occur within a short timeframe, ranging from days to months as seen in this case. One of the key features of an earthquake swarm that differentiates it from regular earthquakes is that no single earthquake can be seen as the main event and larger earthquakes in the swarm are not followed by a series of aftershocks, thus behaving differently to a ‘normal’ earthquake that has precursors, a main event, and aftershocks.
Over 60 earthquakes around the original site have since been detected by the Treble DAS interrogator, with the most powerful registering at 4.8 magnitude on January 24th 2022. The swarm has produced some impressive results on the DAS interrogator, some of which we have shared below.
The following image shows the seismic trace of the 4.8 magnitude earthquake recorded with the Treble DAS interrogator alongside Geoscience Australia’s trace, produced with fixed place seismometers. As seen in the original article, these traces show the ability of DAS to monitor seismic events alongside traditional tools and produce incredible results. Even with the DAS system located in a noisy city environment 188km away from ground zero DAS was able to detect and display these events live with clear P and S wave arrivals.
The waterfall plot below shows real time data displaying the clear arrival of both the P and S waves over a 7km length of fiber. As with the 4.0 magnitude earthquake in early January, a discreet moveout can be observed.
Terra15 hopes that using fiber for earthquake monitoring will be standard practice in the future, especially in earthquake prone regions of the world to help coordinate emergency services, guide future building regulations, and save lives. This data can easily flow into the IRIS global database or Geoscience Australia.
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