Did Sandy trigger major earthquakes off Vancouver?

The NASA image below gives an impression of the strengtrh of hurricane Sandy, as it approached the U.S. coast on October 28, 2012. 

Image produced with data from a radar scatterometer on the Indian Space Research Organization’s (ISRO) Oceansat-2,
showing the strength and direction of Sandy’s ocean surface winds on October 28, 2012.

The animation below was created by Alex Hutko, a seismologist at the Incorporated Research Institutions for Seismology (IRIS) in Seattle. It shows how seismic stations lit up as hurricane Sandy continued its path.

 

The images below are screenshots from the animation, showing how three eathquakes hit the coast off British Columbia in Canada, coinciding with large tremors caused by Sandy. A 7.7 magnitude earthquake (image below) hit the coast off Vancouver on October 28, 2012, at around 2:00 EDT. The USGS later upgraded the earthuake to magnitude 7.8 and gave the time as 3:04 UTC.

 

 

A 6.3 earthquake below hit the area the same day (October 28, 2012) at 17:00 EDT (USGS: 18:54 UTC).

 

 

A 6.2 earthquake (image below) followed on October 30, 2012.

 

 

The USGS image below gives further time and location details of these earthquakes using UTC time. 

 

 

There were more earthquakes than that. At the USGS site, I counted 90 further earthquakes in the area with a magnitude of at least 4 that occurred within days of the first earthquake.

 

Paul Beckwith, regular contributor to this blog, gives the following comments on the question whether Sandy was the trigger for major earthquakes off Vancouver.

“Sandy was a massive storm, packing an enormous amount of energy. According to Jeff Master's Wunderground blog, she carried the energy equivalent of five Hiroshima sized nuclear bombs.

 

As she approached the eastern seaboard of the United States she was detected on the seismic stations in the U.S. As she moved her large size (tropical storm winds within a 900 mile diameter) and extremely low pressure center (940 mb usually indicative of Category 3 or even 4 magnitude hurricanes), she sucked enormous quantities of ocean water upward.

 

Clearly, this adds tremendous stresses onto the earths crust and pushes it downward; this was reflected in the seismic stations. The animation of her progress shows the ground stresses across North America between October 14th and November 1st. On her northward jaunt up the eastern coast the seismic strain lit up to a peak and there was a 7.8 magnitude earthquake (Oct 28th, 3:04 UTC) off Vancouver, as shown in the first image.

 

As she continued northward and just before her extremely unusual left turn (due to extreme waviness of Rossby wave jet streams leading to continental low and northward tilted blocking high), there was another maximum of red seismic activity and a 6.3 magnitude aftershock (October 28, 18:54 UTC).

 

Then she turned left and as she crossed the coastline just south of NYC there was a second large aftershock of 6.2 magnitude (October 30, 2:38 UTC). Again, this aftershock coincided with large seismic activity indicated in red on the east coast.

 

Coincidence? I think not. Stress on one side of a continental plate (North American plate in this case) can deflect the plate downward locally and cause it to bow up or down afar, i.e. on the other side of the plate of the west coast). The precise coincidence of the timing for the main quake and the 2 aftershocks with peaks of seismic activity on the eastern coast seems to match too closely to be a mere coincidence, but more study is required.”

In conclusion, there is a danger that storms and cyclones trigger submarine earthquakes, which can in turn cause shockwaves and landslides over a wide area, destabilizing hydrates and triggering massive releases of methane in the process. As the sea ice disappears, the Arctic Ocean increasingly features open waters which are more prone to cyclones.

Arctic Sea Ice set to collapse in 2015

The image below depicts Arctic sea ice volume as calculated by PIOMAS (the Pan-Arctic Ice Ocean Modeling and Assimilation System at the Polar Science Center

Total Arctic sea ice volume from PIOMAS showing the volume of the mean annual cycle.

Below, the average monthly volume data over the years with exponential trends added by Wipneus, incorporating the data for November 2012. 

In November 2012, the average Arctic sea ice thickness over ice-covered regions fell below one meter, as illustrated by the image below. 

Average Arctic sea ice thickness over the ice-covered regions from PIOMAS for a selection of years.
The average thickness is calculated for the PIOMAS domain by only including locations where ice is thicker than .15 m

As the sea ice gets thinner, the risk increases that the ice will break up. More open water makes the Arctic Ocean more prone to storms and associated feedbacks that can be expected to speed up such break up. Furthermore, they can push much of the ice into the Atlantic Ocean, leaving little ice in the Arctic Ocean to reflect sunlight back into space and to act as a buffer when temperatures start rising again the following year. For more on such feedbacks, see the post Diagram of Doom. 

Professor Peter Wadhams warns in an article in Scientific American that the rate at which summer melting is outstripping accumulation of new ice in winter makes the entire ice cover likely to collapse by 2015. Less ice means that less sunlight will be reflected back into space; as a result, warming in the Arctic will accelerate dramatically. Because a third of the Arctic Ocean is composed of shallow shelf seas, surface warming will extend to the seabed, melt offshore permafrost and trigger the release of methane, which has a much greater greenhouse warming effect than CO2. A Russian-U.S. expedition led by Igor Semiletov has recently observed more than 200 sites off the coast of Siberia where methane is welling up from the seabed. Atmospheric measurements also show that methane levels are rising, most likely largely from Arctic emissions. To avoid the consequences of a collapse of summer ice, we need to bring back the ice we have lost. That will require more than merely slowing the pace of warming—we need to reverse it, Professor Wadhams adds.