SCIENCE  HIGHLIGHTS  -  JULY  2004

Sauber Research on Glacier-Earthquake Link Highlighted
NASA Press Conference Describes How Glacial Retreat May Advance Earthquake Timing

Alaska suffers large and devastating earthquakes, due to its location along a major tectonic subduction zone. It is also known for its mountain glaciers which experience advances and retreats in response to climate change. Advances increase the surface loading and retreats decrease that loading, causing changes to the stress levels on faults which can rupture in an earthquake. A joint research effort by NASA and USGS scientists over the last several years has demonstrated an apparent link between deglaciation (loss of ice mass) and a possible increase in the frequency of earthquakes.  This research was the subject of a NASA press release on July 26, 2004.

Earthquakes, especially those at the subduction zones
where one tectonic plate slides beneath another, have
been a central focus of Jeanne Sauber’s research
since graduate school at MIT. As a civil servant in the
Geodynamics Branch of Goddard Space Flight Center
she did field studies in Alaska using GPS to measure
crustal motions as a constraint on models of how
earthquakes occur. More recently she has teamed
with Bruce Molnia, a glaciologist from the USGS,
to study how changes in the mass of glacial ice can
affect the earthquake process. Their work, described in several recent papers, has demonstrated a link between unloading of the crust due to glacial retreat and the frequency of earthquakes: it appears that loss of ice during glacial thinning may advance the likely onset time of recurrent large earthquakes. Unloading the crust by removing the overburden pressure makes it easier for the faults to move, so the plate tectonic driving of the plates can proceed more easily, likely leading to more frequent ruptures. On a larger scale similar increases in the occurrence of earthquakes appears to have accompanied the end of major ice ages.
     This important result was highlighted in a July 26, 2004 NASA press release, and has been the subject of news stories and almost daily interviews since. Details can be found at the Goddard Top Story web site at   http//www.gsfc.nasa.gov/topstory/2004/07/15glacierquakes.html .  The Fairbanks, Alaska newspaper carried the story on the front page, and a National Public radio interview was broadcast on August 5, 2004.

Map showing location of the Bagley glacier (left) and the Malaspina glacier (right) in southeaster Alaska. Significant changes in ice mass loading have occurred in this area. Loss of ice reduces the loading on the crust, making it easier for the tectonic plates to move as they do suddenly in an earthquake.

Contact:  Jeanne Sauber, GSFC, Code 921, jeanne@steller.gsfc.nasa.gov