Re: M1.0 event: Geologists haven’t indicated it was a blast. But due to it being tiny, deciphering the waveform for a blast at this location could have been assumed to be a quake. The depth of -0.03km is referenced to Mean Sea Level. The elevation of the surface at this location is around 291-310 feet (-0.0946km up from MSL*). Satellite maps of the location doesn’t indicate an active quarry... So nothing to confirm a “Controlled Blast”.
*note: a negative sign on the depth is upwards from 0.0 MSL. 1.6km depth of the 0.8 magnitude 2nd quake is 1.6km below MSL (this can be eliminated as a “controlled blast”.
Md0.99 Northern California
Event Summary
Date/Time
(UTC) 2017-02-14 10:56:01 UTC
(21 hours, 40 minutes ago)
Location Northern California
Magnitude Md 0.99
Latitude 39.541833° N
Longitude 121.509833° W
Depth -0.03 km
Depth -0.03 km
Surface -0.0946km
About 212 feet below the surface
Feds, Calif. disagree on seismic safety of U.S. tallest dam
Published 9 December 2013
(snip)
The Sacramento Bee reports that the 2010 inspection, conducted by consultants working for the Federal Energy Regulatory Commission (FERC), found no significant flaws in the dam itself. Inspectors recommended the earthquake safety assessment based on recent information about earthquake hazards in the vicinity of the dam.
The California Department of Water Resources (DWR) has no plans to conduct the assessment due to what the department considers to be an “unjustified expense,” but requests by state and federal regulators may force an assessment.
(snip)
Ronald Stork, a senior policy advocate at Friends of the River,noted that the Oroville Dam exhibits a case of reservoir-induced seismicity. In such a case, the reservoir itself can cause earthquakes due to the weight of water stored behind the dam being large enough to shift the earth’s crust. Studies have documented the case at Oroville. “A dam with a whole lot of shaking going on … does seem to be something you need to be really careful about,” said Stork, who monitors dam regulation across the state. “You lose a 3.5million acre-foot reservoir — the tallest in the United States — and that could cause a whole mess of downstream trouble.”