January 13, 2012
by Kate Allstadt
We continue to monitor the repeating earthquakes and to improve our methods for characterizing them. Noise due to high winds at a few stations, primarily RCM and STAR, was resulting in poor multiplet detection for a few periods. To get around this problem, we redid all calculations using just the Camp Schurman station (RCS). RCS is more sheltered from the wind and is also closest to many of the multiplet sets, we were able to detect a few hundred more multiplets and to fill in some of the gaps in detection. These results are plotted below. The first plot is the timeline of repeating events, each circle represents one earthquake. Earthquakes on the same line are in the same set of repeaters, each having nearly identical waveforms to the next, the total number in each set is listed at the end of the line.
There are two sets with over 500 events each and two more with over 100. There also are several smaller sets, some starting prior to the start of the main sequence. If we compare the recurrence intervals of the four biggest sets (see figure below), we see that the two largest sets started out occurring more frequently, then slowed down and became more regular. Around January 5th the second largest set (red) started gradually slowing down and petering out while the largest set is still chugging along at a steady ~20 minute recurrence interval.
The four lines are tricky to follow, so here are the two repeating sequences with the most pops. The first one shows irregular recurrence intervals for a few days, then frequent repetitions for a week, variable recurrence intervals for a few days at the start of January, then settling on 20 minute intervals recently, as we noted in the previous blog post.
The second on starts out a few days later with frequent pops, settles on 20-minute intervals for a few days (while the first sequence is losing its periodicity) then strikes more and more infrequently, with events more than an hour apart now.
If we plot up the weather conditions, temperature, wind speeds, precipitation (liquid), and snow levels recorded at Paradise and Camp Muir and compare them to the number of repeating earthquakes per hour (total for all sets), we see that the precipitation curves closely follow the shape of the earthquakes per hour curve.
This correlation could of course be a coincidence, but assuming it is not, it supports a glacial or other non-volcanic source. Glaciers are controlled by climate and respond to weather forcing while a volcano preparing to erupt couldn't care less about the weather. However, glaciers are usually slow to respond to changes and the appearance of these repeating earthquakes is nearly instantaneous (in glacier-time) with the dumping of snow from the passing storm. A glaciologist colleague upstairs did some back of the envelope calculations and found that the amount of snow that fell in this storm would only increase the driving stress pushing the Rainier glaciers downhill by 0.5%, a practically negligible amount. But these are no ordinary alpine glaciers, these are glaciers riding on a bed of crumbly volcanic rocks and heated from below, the typical rules may not apply.
- Is Mount St. Helens seismicity increasing?
- Warm weather triggers snow avalanches at St. Helens
- Seismic recordings of a gas explosion in North Bend, WA
- Seismic signals generated by the March 22nd Oso Landslide
- Legacy web site content returns
- Ice avalanches on Cascade volcanoes
- A New View On What's Shaking on the Cascade Volcanoes
- Seismic Spectrograms - A new way to look at wiggles
- The final football game analysis
- The Football Game Experiment Continues
- July (1)
- May (1)
- April (1)
- March (2)
- February (3)
- January (4)
- October (1)
- September (1)
- August (1)
- June (1)
- April (3)
- March (4)
- February (1)
- January (2)
- December (1)
- November (2)
- October (3)
- September (1)
- August (3)
- July (2)
- June (4)
- May (4)
- April (2)
- The wech-o-meter takes over all of Cascadia
- Keystone Cops: Italy prosecutes seismologists for failure to predict deadly quake
- UFOs in eastern Washington? No, rather UTEs (Unidentified Terrestrial Events)
- New Sodo Seattle Liquefaction Array Installed
- Why we should constantly watch the deformation of the seafloor
- Mystery chirp near Newberry Volcano
- Planting seismographs causes earthquakes? or maybe ice-quakes?
- Tunneling rumbles south under Capitol Hill
- 15 years of mostly silent magma inflation near Three Sisters, Oregon
- Mount Hood earthquake swarm of Feb 23, 2012
- Web glitches: duplicate (and even triplicate!) earthquakes
- How earthquake magnitude scales work
- Mine blast masquerades as volcanic tremor
- The Spokane Swarm about 10 years ago
- Another hum around Mount St. Helens
- Slow slip: A new kind of earthquake under our feet
- PNSN and social media
- 3am M3.4 earthquake in St. Helens Seismic Zone
- The wrong kind of volcano noise
- Fast chatter on Rainier an hour ago
- Can slush-mageddon trigger earthquakes?
- Rainier Repeating Earthquakes Update and Comparison with Weather Patterns
- 22-minutes drumbeat icequakes(?)
- Mount Rainier popping away
- Repeating Earthquakes on Mount Rainier - are glaciers the culprit?
- Debunking another SEC football myth by the PAC-12
- One year ago, Seattle Seahawks 12th Man Earthquake
- The odds this year of a megaquake on the Pacific Northwest coast
- Is the plague of great earthquakes this decade a sign of increased danger?
- Nile Valley landslide talks to PNSN seismologists
- Good vs evil in central US earthquake hazard analysis
- Why does a volcano scream?
- Predicting big quakes from patterns of little ones
- 1-hour warning for Japanese M9 earthquake?
- Sound Transit train under Interlaken keeps a rollin'
- Invisible changes under the hood at the PNSN
- Sound Transit Tunneling Noise
- "Visionary" toads
- Earthquake early warning in the PNW
- November (1)
- December (13)