iMUSH (iMaging Magma Under St Helens)

NSF GeoPRISMS and NSF EarthScope: EAR 1144455

Mount St Helens

Mount St Helens viewed from the northwest, August 2014.

NSF Abstract

To better understand volcanic activity on our planet, it is fundamental to get an accurate representation of magma generation zones and storage regions in the Earth’s crust and upper mantle. Illuminating the architecture of the plumbing system beneath volcanoes will allow scientists to determine (1) at which depths and conditions magmas are generated, and (2) the shapes and sizes of pathways and reservoirs as magma travels towards the surface. Such knowledge will allow scientists to make more informed predictions on the durations of volcanic crises and on the total volume of erupted material during eruptive episodes.

This project focuses on the Mount St. Helens volcanic edifice, (WA, USA), whose explosive eruption in 1980 attracted world’s attention, and was the first volcano to be thoroughly monitored with modern instruments. Mount St. Helens provides the perfect setting to apply state-of-the-art geophysical and geochemical techniques to image its subterranean roots: It is active, easily accessible, and has a well recorded past history. The project will use many different methods (active and passive source seismic tomography and scattered wave imaging, magneto-telluric imaging, petrology and geochemistry), involving a large collaborative team, to image the volcano’s plumbing system with unprecedented resolution from the subducting plate to the surface. The results will be extendable to many other volcanoes around the world, particularly those located in the infamous Pacific Ring of Fire.

Rice is one of the institutions involved in the iMUSH project. Our original partners were the University of Washington (Ken Creager, lead PI, John Vidale, Steve Malone), Oregon State University (Adam Schultz), Cornell University (Geoffrey Abers), the ETH Zurich (Olivier Bachmann),  and the U.S. Geological Survey (Seth Moran and Roger Denlinger).  Partners that have joined iMUSH are the University of New Mexico (Brandon Schmandt), and the University of Arizona (Eric Kiser, the former Rice iMUSH Post-doc).

iMUSH Project Website

iMUSH Facebook Page

The Rice component of iMUSH is the active source seismology tomography experiment, designed to image the crustal magma plumbing system in 3D with high ray density directly beneath MSH: The experiment was centered on MSH with two rings of shots surrounding the volcano at ~ 15 and ~30 km radii, and additional shots at 50 and 75 km distance in the NW, NE, SW, and SE quadrants (Figure).  A team of ~55 volunteers conducted the iMUSH active experiment in July and August 2014, fielding ~2500 Reftek RT125 “Texan” seismographs twice. 250 seismographs were hiked into the region around MSH. A piggyback experiment of 940 continuously recording Nodal Seismic units were deployed on foot within ~7.5 km of MSH by the University of New Mexico, giving the experiment a total of 6000 seismographs.  The National Seismic Source Facility at the University of Texas at El Paso detonated 23 450 and 900 kg shots. with source-receiver offsets up to ~170 km. Including Texan and Nodal seismograph deployment and the shooting, experiment required the efforts of ~75 people.

iMUSH active experiment. Black dots are Texans, blue dots are Nodal seismic, white stars are shots

iMUSH active experiment deployments. Red triangle is MSH. Black dots are Texan seismographs, blue dots are Nodal seismographs, white stars are shots. Red stars are local earthquakes recorded by the Texan and Nodal arrays.  MR is Mount Rainier, MA is Mount Adams

The first results from the experiment can be found in:

Kiser, E., Palomeras, I., Levander, A., Zelt, C., Harder, S., Schmandt, B., Hansen, S., Creager, K. and Ulberg, C., 2016. Magma reservoirs from the upper crust to the Moho inferred from high-resolution Vp and Vs models beneath Mount St. Helens, Washington State, USA. Geology44(6), pp.411-414.  Geology Paper