Seemed to coincide with a distant helicopter passing by. Nothing on the HDF channel other than the helicopter. Perhaps material contraction rather than specific local event. Nothing comparible on nearby shakes.
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An intense one in the low frequencies, for sure!
We have seen instances of similar spikes in the past, and you can find a summary of the topics that covered them in this search: Search results for 'spike' - Raspberry Shake
This topic is probably one of the best on the subject: Spikes in Recording
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