The pre-lecture dinner (5:30 pm in the Mitchell Bldg, 1st floor) requires reservation no later than 06/02/06, and is $30 regular, $5 for students; however no-shows owe full price.
Abstract
In 1957 Allan Cox reported in _Nature_ that the paleomagnetic pole for the
Eocene Siletz River Volcanics (SRV) of the Oregon Coast Range lay far to
the east of the geocentric axial dipole, an oddity that defied adequate
explanation for nearly two decades. Subsequent studies have shown that the
Oregon Coast Range (OCR) has rotated clockwise more than 70 degrees since
50 Ma, and that rotation decreases northward into Canada, southward into
California, and eastward into the backarc. The rotations are thought to be
driven by Basin and Range extension and dextral shear between N. America
(NA) and northward-moving oceanic plates to the west. The block rotations
are related to patterns of seismicity and volcanism in Cascadia, and GPS
data from McCaffrey and others indicates rotations are still occurring. We
have created independent block models that honor the paleomagnetic and GPS
data, and they are very similar. We can combine the paleomagnetic,
geologic, and GPS data into a single model of plate-like blocks bounded by
elastic fault zones The rotation pole for the OCR lies nearby in
northeastern Oregon. Calculated forearc velocities are consistent with the
rate and direction of extension in the Basin and Range province, the change
from extension in the southern Cascade arc to compression in the northern
arc, and the northward shortening and crustal seismicity in western
Washington as it is compressed against the Canadian Coast Mountains
buttress. The rate of shortening across western Washington and the Puget
Lowland is 4.4 +/- 0.3 mm/yr, sufficient to drive the Seattle fault and
many other recently discovered active faults in the Lowland.
About the Speaker
http://www.diggles.com/pgs/2006/060317-5104_Ray.jpg
Ray's specialties include geologic mapping, Pacific Northwest geology and
tectonics, geology of the Cascadia forearc, crustal deformation and
neotectonics of convergent margins, structure of subduction zones,
paleomagnetism . Ray's current work includes
* Geologic mapping of Urban Corridor fault zones (Gales Creek fault zone,
NW Oregon; Seattle fault, Puget Sound Washington (with Rick Blakely, Alan
Nelson, Sam Johnson, Tom Brocher, Brian Sherrod, Derek Booth, Kathy Troost,
and others).
* Geologic mapping of the Columbia River Basalt aquifer, NW Oregon, using
aeromagnetic and paleomagnetic methods, geochemistry and classical field
work (with Rick Blakely, Jon Hagstrum, Marv Beeson, Terrry Tolan, and Al
Niem).
* Modeling of plate motions along the Cascadia convergent margin,
comparison to GPS results, and assessment of strain partitioning in the
forearc (with Bob Simpson, Rick Blakely, Craig Weaver).
* Study of slip during great subduction earthquakes, its relation to
margin structure, and implications for the Cascadia subduction zone (with
Rick Blakely, and Yuichi Sugiyama, Geological Survey of Japan).
* Pacific Northwest Project management
* President of the Peninsula Geological Society
