Saturday, December 24, 2011

Yet More Continuing Quakes At Mono Lake Swarm Region

About a week went by with no quake activity at Mono Lake, CA, until yesterday 12/20, when p to five tremblors hit the region East of the Mono Lake shoreline. These quakes registered from 1.2-2.6 in magnitude at a depth of 5.1km - 8km below the surface (which is still quite shallow geologically). The ongoing swarm has still not yet been analyzed by USGS, so speculation is still an unwise idea at this time, however I'm going to take a wild guess and say that this is probably hydromagmatic, or related to a small dike intrusion... again this is speculation.

There are many possibilities as to what is occurring in this region, ranging from subterranian hydrothermal activity, tectonic stress, magmatic dike intrusion (similar to what just occurred in the Sierraville, CA region), or other anomalies. The most recent eruptive activity occurred at Mono Lake less than 200 years ago (as per argon dating), which resulted in the extrusion of a rhylotic cryptodome. So given this (geologically) recent activity, it is probably safe to assume that these quakes are not purely tectonic in nature.

Indeed Mono Lake is considered by some to be a part of the Long Valley Caldera region, although most scientists say that they are chemically and magmatically distinct from each other. This could be the case, but they do share similar geologies, and are along the same fault area, so they could have a few things in common. I have posted more screenshots of the most recent additions to the quake swarm (Screenshots are of Google Earth with the USGS real-time Earthquake layer added). The quakes from the start of the swarm no longer appear on this screenshot as they are more than 1 week old. This screenshot only displays the quakes within the past week.



The below screenshot is some of the wave forms recorded (I am no geologist, but if one of my readers happens to be, please feel free to comment on the wave forms in all your scientific glory). This waveform is from the 2.6 magnitude quake (below picture from USGS at this link ).

                               

While I am no expert on seismic waves, these no not appear to be harmonic tremors, but I could be mistaken. These simply look like common rock-breaking quakes to my eye, which could mean these are purely tectonic. Again, I'd really like an actual expert on wave forms to weigh in on this, but my Internet exposure is still in its infancy as far as this blog is concerned. However I am the only person (to my knowledge) reporting on these quakes at this time, so hopefully someone with the correct qualifications will run across this post.

I have reviewed some past wave forms of tectonic quakes that occurred near this ares earlier this year (located here) and they are quite similar to the wave forms in the above snapshot.

This swarm is still very intriguing, mostly because of how localized (within only a couple miles) these quakes are occurring. It certainly begs the question, will we be seeing minor activity at Mono Lake in the near future? I will be keeping my eye on this for a while, or until the situation stops.


****UPDATE****
12/24/2011

There were two quakes today at the swarm region registering 2.0 and 2.7 at a depth of 3.7 miles. These quakes are a bit stronger than the typical ones so far. Keeping an eye on the continuing swarm. It is hard to tell given the local clustering of these quakes whether or not this is purely tectonic... the quakes could certainly indicate minor dike intrusion.

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