 |
| Titel |
Magma Intrusion at Mount St. Helens, Washington, from Temporal Gravity
Variations |
| VerfasserIn |
Maurizio Battaglia, Mike Lisowski, Dan Dzursin, Mike Poland, Steve Schilling, Angie Diefenbach, Jeff Wynn |
| Konferenz |
EGU General Assembly 2017
|
| Medientyp |
Artikel
|
| Sprache |
en
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250140744
|
| Publikation (Nr.) |
 EGU/EGU2017-4173.pdf |
|
|
|
|
|
| Zusammenfassung |
| Mount St. Helens is a stratovolcano in the Pacific Northwest region of the United
States, best known for its explosive eruption in May 1980 – deadliest and most
economically destructive volcanic event in US history. Volcanic activity renewed in
September 2004 with a dome forming eruption that lasted until 2008. This eruption
was surprising because the preceding four years had seen the fewest earthquakes
and no significant deformation since the 1980-86 eruption ended. After the dome
forming eruption ended in July 2008, the volcano seismic activity and deformation
went back to background values. Time-dependent gravimetric measurements can
detect subsurface processes long before magma flow leads to earthquakes or other
eruption precursors. A high-precision gravity monitoring network (referenced to a
base station 36 km NW of the volcano) was set up at Mount St Helens in 2010.
Measurements were made at 12 sites on the volcano (at altitudes between 1200 and 2350
m a.s.l.) and 4 sites far afield during the summers of 2010, 2012, and 2014. The
repeated gravity measurements revealed an increase in gravity between 2010 and
2014. Positive residual gravity anomalies remained after accounting for changes in
surface height, in the Crater Glacier, and in the shallow hydrothermal aquifer. The
pattern of residual gravity changes, with a maximum of 57±12 μGal from 2010 to
2014, is radially symmetric and centered on the 2004-08 lava dome. Inversion of the
residual gravity signal points to a source 2.5-4 km beneath the crater floor (i.e., in
the magma conduit that fed eruptions in 1980-86 and 2004-08). We attribute the
gravity increase to re-inflation of the magma plumbing system following the 2004-8
eruption. Recent seismic activity (e.g., the seismic swarm of March 2016) has been
interpreted as a response to the slow recharging of the volcano magma chamber. |
|
|
|
|
|
|