Seemorerocks: An important resource on seismic events and the Arctic

Seismic Events

Seismic events include earthquakes, volcano eruptions, landslides and shockwaves that can in turn trigger tsunamis, avalanches and further seismic events.

People are changing the climate and this can trigger seismic events. Earthquakes can be triggered in a number of ways, including the following:
• Earthquakes can be triggered by fracking and by waste pits and pools associated with fracking.
See the article at:
http://www.pbs.org/newshour/rundown/earthquakes-triggered-by-fracking
• Warming caused by people makes snow and ice melt, removing weight off the land and dumping it into the sea. This change in weight can trigger earthquakes. See text further below and the post at:
https://arctic-news.blogspot.com/2015/02/something-had-to-give-baffin-island-hit-by-m4.6-earthquake.html
• The Earth's crust can be flexed by storms. Large cyclones first suck up water, making sea level retreat and lifting up the crust. Then, a surge follows, while huge amounts of rainwater can add further weight, pushing the crust down again. This change can be felt over longer distances, triggering earthquakes across continents. See the post at:
https://arctic-news.blogspot.com/2017/09/extreme-weather-is-upon-us.html
• Wild weather swings can be the result of changes in the jet streams caused by global warming. Huge sudden swings in temperature and in air pressure can make soils and ice go abruptly from expansion to compression and back again, which can cause cracks and landslides, and associated shockwaves, which can in turn trigger larger seismic events and open up methane craters with can come with large releases of methane. See the segment further below on 'Earthquakes and Extreme Weather Events'.
• War and explosions associated with testing of new weapons could also trigger seismic events, as discussed e.g. at:

http://www.zerohedge.com/news/2017-09-16/north-koreas-nuclear-tests-could-trigger-supervolcano-eruption

An example of a landslide is the M 4.2 seismic event in Greenland
https://earthquake.usgs.gov/earthquakes/eventpage/us20009nlg#executive
• location: 107km N of Uummannaq, Greenland
• date & time: June 17, 2017 23:39:12 UTC
• co-ordinates: 71.640°N 52.344°W
• map: https://earthquake.usgs.gov/earthquakes/eventpage/us20009nlg#map
For more, see this discussion.

In turn, earthquakes can cause clathrate destabilization, resulting in methane releases. Below are discussions of links between seismic events in the Arctic and methane releases.

Earthquakes and Methane

An earthquake hit the Arctic Ocean with a magnitude of 4.7 on the Richter scale on July 12, 2016. High levels of methane showed up in the atmosphere on July 15, 2016, over the area where the earthquake hit.

From:
• High Methane Levels Follow Earthquake in Arctic Ocean
https://arctic-news.blogspot.com/2016/07/high-methane-levels-follow-earthquake-in-arctic-ocean.html

An earthquake with a magnitude of 4.5 on the Richter scale hit the seafloor 204 km East of Nord, Greenland, on May 8, 2017. The inset shows that methane levels over 1950 ppb (magenta color) were recorded on the morning of May 8, 2017, by two satellites.

From:
• Earthquake east of Greenland triggers methane releases
https://arctic-news.blogspot.com/2017/05/earthquake-east-of-greenland-triggers-methane-releases.html

Some of the earthquakes occurring in 2014 were discussed in specific posts:
• M4.6 - North of Franz Josef Land, 2014-04-13 02:12:19 UTC, discussed in this post
• M4.2 - North of Franz Josef Land, 2014-04-04 07:01:30 UTC
• M4.4 - 262km NE of Nord, Greenland, 2014-04-22 10:30:23 UTC, discussed in this post
• M4.3 - 148km SSE of Longyearbyen, Svalbard, 2014-04-24 08:33:06 UTC
• M5.1 - Greenland Sea, 2014-04-26 03:55:33 UTC, discussed in this post
• M4.5 - Gakkel Ridge, 2014-03-06 11:17.17.0 UTC, discussed in this post

As melting of the Greenland Ice Sheet speeds up, isostatic rebound could cause earthquakes around Greenland to become stronger and occur more frequently. Earthquakes in this region are very worrying, as they can destabilize hydrates contained in the sediment under the seafloor of the Arctic Ocean. Furthermore, one earthquake can trigger further earthquakes, especially at locations closeby on the same faultline.

From:
• M5.1 Earthquake hits Greenland Sea
https://arctic-news.blogspot.com/2014/04/m51-earthquake-hits-greenland-sea.html

Earthquakes and Extreme Weather Events

An earthquake with a magnitude of 4.6 on the Richter scale hit Baffin Island on February 12, 2015, at 02:11:40 (UTC). The image below, from the United States Geological Survey (USGS), shows the epicenter of the quake.

The earthquake occurred at a time when surface temperature anomalies over parts of North America and Greenland are at the bottom end of the scale, while surface temperature anomalies over parts of Siberia are at the top end of the scale, as illustrated by the image below.

The image below shows pressure differences reaching the top and bottom ends of the scale (left). At the same time, sea surface temperature anomalies around North America and Greenland are at the top end of the scale (right). It appears that something had to give.

This earthquake is important, given that it hit an area without large faultlines (though earthquakes are common here, also see this discussion). The Baffin Island earthquake occurred in an area prone to glacial isostatic adjustment, as illustrated by the image below.

From "http://grace.jpl.nasa.gov", (unfiltered version). Credit: A, G., J. Wahr, and S. Zhong (2013) "Computations
of the viscoelastic response of a 3-D compressible Earth to surface loading: an application to Glacial Isostatic
Adjustment in Antarctica and Canada", Geophys. J. Int., 192, 557–572, doi: 10.1093/gji/ggs030

Glacial isostatic adjustment as a phenomenon takes place over relatively long periods. An additional problem is extreme weather events influencing the occurence of earthquakes more immediately.

Five earthquakes occured on February 13, 2015, closely after each other together:
• M5.3 Northern Mid-Atlantic Ridge 2015-02-13 18:48:16 UTC 10.0 km
• M4.9 Northern Mid-Atlantic Ridge 2015-02-13 18:58:06 UTC 10.0 km
• M7.1 Northern Mid-Atlantic Ridge 2015-02-13 18:59:12 UTC 13.8 km, south of Greenland
• M4.7 Reykjanes Ridge 2015-02-13 21:25:18 UTC 10.0 km
• M5.2 Reykjanes Ridge 2015-02-13 19:33:10 UTC 14.2 km

The M7.1 is the largest earthquake to hit the area around Greenland in a decade or more. And it's not just this one that has recently hit the area. The image below shows the February 12, 2015. Baffin Island quake in yellow, and the earthquakes that occurred on February 13, 2015, at the Northern Mid-Atlantic Ridge in orange. Furthermore, there are recent quakes on Iceland in orange and yellow. There were also three large earthquakes in the Greenland Sea, the 4.6 one is highlighted in blue (otherwise it would have been hidden).

The image below gives an impression of extreme weather events on February 13-14, 2015.

Links between extreme weather events and earthquakes have been discussed before. Extreme weather events look set to intensify as temperatures in the Arctic keep rising. This is very worrying, given the vulnerability of methane under the seafloor of the Arctic Ocean. Furthermore, there are also indications that methane could be released from Greenland due to sequences of strong compaction and expansion of the snow and ice cover, due to extreme weather events.

High methane levels have recently been recorded in the atmosphere over the Arctic Ocean, including over Baffin Bay.

Methane is present in sediments under the Arctic Ocean in the form of free gas and hydrates. Earthquakes can send out strong tremors through the sediment and shockwaves through the water, which can trigger further earthquakes, landslides and destabilization of methane hydrates.

As temperatures in the Arctic keep rising, the jet streams and polar vortex are changing their shape, in particular becoming more wavy, which can cause more extreme weather events such as the events described above.

From:
• Something had to give - Baffin Island hit by M4.6 earthquake
https://arctic-news.blogspot.com/2015/02/something-had-to-give-baffin-island-hit-by-m4.6-earthquake.html

Methane Release caused by Earthquakes

Methane hydrates can become destabilized due to changes in temperature or pressure, as a result of earthquakes and shockwaves accompanying them, severe storms, volcanic activity, coastal collapse and landslides. As an example, an earthquake followed by methane release was discussed in the post Sea of Okhotsk a few months back. Such events can be both primed and triggered by global warming, particularly in the Arctic, as follows:

As more ice melts away on Greenland and more water runs off into the sea, there is less weight on the Earth’s crust under Greenland. The crust and mantle can bounce back during a large melt, an effect that is called 'isostatic rebound'. This rebound can not only trigger earthquakes and landslides, it can also suck up the magma in the Earth’s crust to the surface and trigger volcanic eruptions.
The added weight of water from melting glaciers stresses the Earth’s crust underneath the sea, which can cause earthquakes. This is especially the case for coastal waters, where the impact of the water that flows into the sea is huge, not only in terms of weight, but also in terms of the currents they cause.
As the permafrost melts, mountain ranges, soil and submarine sediments all become less robust. Where the permafrost previously held things together, we can now expect more coastal collapse, avalanches and landslides, which can send shockwaves through the sea that in turn trigger earthquakes and hydrate destabilization.
Methane hydrates that are on the edge of stabilization can be disturbed by global warming in two additional ways, temperature and pressure: Warming of the Earth's crust as heat penetrates sediments on the seafloor. Thermal expansion of the Earth's crust means that the crust will expand slightly in volume, resulting in expansion of the cavity that holds the hydrates.
Finally, there's the additional impact of methane itself. Permafrost previously kept methane stable in sediments. Methane converting from hydrates into free gas will expand some 160 times in volume; this explosive process can trigger further destabilization. Once released into the atmosphere, the methane has a huge local warming potential, adding to the threat that further methane releases will occur locally.

Back in 2006, Bill McGuire said: "A particular worry is that this in turn will contribute to large-scale releases of methane gas from the solid gas hydrate deposits that are trapped in marine sediments. Gas hydrates have been identified around the margins of all the ocean basins, and outbursts of gas may occur as sea temperatures climb or as rising sea levels trigger underwater quakes in the vicinity."

For more than a decade, Malcolm Light, contributor to the Arctic-news blog, has been warning about the danger of methane hydrate destabilization due to earthquakes (see the poster at the bottom of the page on seismic activity).

With this in mind, let's take a look at a picture of Earth.

September 13, 2013, 3am - Sep 14, 2013 1am [ click on image to enlarge ]

The large number of yellow spots in the top left corner are related to the flooding in the Basin of the Amur River (Heilong Jiang). Such extreme weather events are becoming ever more prominent, due to global warming and the feedbacks such as methane releases. Similarly, extreme weather events such as droughts and heatwaves lead to wildfires that also produce large amounts of methane.

The image only shows the Northern Hemisphere, but on the Southern Hemisphere, high levels of methane have been recorded for a long time on Antarctica. While huge amounts of snow fall on Antartica, the amount of snow and ice that melts each year is even larger, widening the difference between the weight the snow and ice exercize between periods. This difference in weight could similarly cause rebounds of the Earth's crust, sucking up the magma and causing methane hydrates to be destabilized, as described in the earlier post Antarctic methane peaks at 2249 ppb.

The image also shows fault lines. Several yellow spots are present on the fault line over the Arctic, including some that point at the coast of Norway; they appear to be caused by seismic activity along the fault line, as discussed in the recent post Methane reaches 2571 ppb.

Meanwhile, methane readings peaked at 2416 ppb on September 14, 2013. Very worrying are also the high methane readings close to the Gakkel Ridge, the fault line at the center of the Arctic Ocean, and the spots closer to the Laptev Sea.

Finally, there are high readings along the Aleutian Islands, Alaska. The islands, with their 57 volcanoes, are in the northern part of the Pacific Ring of Fire and they have experienced a lot of seismic activity lately, including an earthquake with a magnitude of 7 on the Richter scale on August 30, 2013, and several more recent earthquakes with a higher magnitude than 6 on the Richter scale.

[Editor: The images below, added September 24 and 26, 2013, show high methane releases at a spot just north of Greenland that was hit by an earthquake with a magnitude of 4.5 on the Richter scale on September 1, 2013, as also discussed in the post Methane reaches 2571 ppb. The two bottom images also show the magnitude 5 earthquake that hit Russia on September 24, 2013.]

September 20, 2013, 11am - Sep 22, 2013 3pm [ click on image to enlarge ]

Sept. 25, 2013 am - the orange spot just north of Greenland indicates a recent earthquake [ click on image to enlarge ]

Map specifying details of two recent earthquakes. Size of spots indicating earthquakes on the map is relative

Adapted from:
• Methane Release caused by Earthquakes
https://arctic-news.blogspot.com/2013/09/methane-release-caused-by-earthquakes.html

Methane, Faults and Sea Ice

The animation below illustrates links between:

The fault line that crosses the Arctic Ocean and forms the boundery between two tectonic plates (i.e. the North American Plate and the Eurasian Plate)
Arctic sea ice, which until now has acted as a shield
The prominence of high methane readings over the Arctic Ocean

[ this animation is a 1.67 MB file that may take some time to fully load ]

Above animation illustrates high methane readings (1950 ppb and higher, in yellow) prominently showing up within the bounderies of the sea ice, and especially along the Gakkel Ridge and Laptev Sea Rift parts of the fault line that crosses the Arctic Ocean.

From:
• Methane, Faults and Sea Ice
http://arctic-news.blogspot.com/2013/11/methane-faults-and-sea-ice.html

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Tuesday, 14 August 2018

An important resource on seismic events and the Arctic

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Tuesday, 14 August 2018

An important resource on seismic events and the Arctic

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