Although there is increasing evidence that fluids may play a significant
role in the earthquake rupture process, direct observation of fluids in active fault
zones remains difficult. Since the presence of an electrically conducting fluid, such
as saline pore water, strongly influences the overall conductivity of crustal rocks,
electrical and...
In a companion paper (Egbert et al., this issue) we describe the estimation of very long period (0.16 < T < 91 days) magnetotelluric (MT) impedances from 11 years of data collected at the Tucson geomagnetic observatory. Here we discuss the implications of these data for mantle conductivity. Using minimum...
We use data from a series of small (three to five stations) overlapping magnetovariational (MV) arrays to image variations of vertically integrated electrical conductivity in the crust of southwestern Washington. Two principal structures are revealed: a large north-south trending anomaly (the southern Washington Cascades Conductor (SWCC), which has been detected...
The stability of a coastal jet and front is investigated using the primitive
equations applied to a continuously stratified flow in geostrophic balance. A linear
stability analysis successfully explains the growth of two modes of instability with
distinctly different horizontal scales. A long-wavelength mode (fastest-growing
wavelength of 0(100 km)) is...
Horizontal current measurements from an array of moored acoustic Doppler profilers are assimilated sequentially into a model of coastal wind-driven circulation off Oregon during the upwelling season of May–August 2001. Model results are compared against independent moored and ship survey data to document a positive effect of velocity data assimilation...
The linear stability of a coastal transition zone (CTZ) jet is analyzed using a six-layer quasi-geostrophic model with observed basic state velocity profiles. The velocity profiles are obtained from objectively analyzed hydrographic and acoustic doppler data from the 1987 CTZ pilot experiment. Along-jet perturbation wave-lengths of 260-265 km are found...
Eleven years (1932-1942) of electric potential and magnetic measurement at the Tucson observatory
represent a unique very long period magnetotelluric (MT) data set. We report here on a careful reanalysis of this
data using modern processing techniques. We have developed and used novel methods for separating out the
quasi-periodic daily...
During summer 2001, high-resolution hydrographic, velocity, and bio-optical surveys
were conducted over Heceta Bank off central Oregon. North of the bank, upwelling
over simple bottom topography exhibited a classic response with a midshelf, baroclinic
coastal jet and upwelled isopycnals. The coastal upwelling jet follows the bank
topography as it widens...
As part of the U.S. Joint Global Ocean Flux Study Southern Ocean
program, high-resolution surveys of the Antarctic Polar Front near 170øW were
conducted during October-November 1997 with a towed undulating system equipped
with conductivity-temperature-depth and bio-optical sensors. Transects along
170°W and two successive mapping surveys revealed zonal bands with...
Observations, from the Oregon continental shelf, describe the slumping of a coastal
upwelling front in response to a reversal of winds from upwelling-to downwelling-favorable.
Initially, the front outcropped in a surface mixed layer of depth 10–20 m with a
pronounced cross-shelf density gradient. Following wind reversal, both the unbalanced
cross-shelf...