Publications

Although rivers provide important biogeochemical inputs to oceans, there are currently no descriptive or predictive relationships of the spatial scales of these river influences. Our combined satellite, laboratory, field and modeling results show that the coastal dispersal areas of small, mountainous rivers exhibit remarkable self-similar scaling relationships over many orders of...

Seismic velocity and attenuation anomalies in the mantle are commonly interpreted in terms of temperature variations on the basis of laboratory studies of elastic and anelastic properties of rocks. In order to evaluate the relative contributions of thermal and non-thermal effects on anomalies of attenuation of seismic shear waves, Q−1s, and seismic velocity, Vs, we compare global maps of...

We report new strength data for the serpentine mineral chrysotile at effective normal stresses, σn between 40 and 200 MPa in the temperature range 25°-280°C. Overall, the coefficient of friction, μ (= shear stress/effective normal stress) of water-saturated chrysotile gouge increases both with increasing temperature and σn, but the rates vary and the temperature-related increases begin...

No abstract available.

The modern Monterey submarine fan, one of the largest deep-water deposits off the western US, is composed of two major turbidite systems: the Neogene Lower Turbidite System (LTS) and the late Quarternary Upper Turbidite System (UTS). The areally extensive LTS is a distal deposit with low-relief, poorly defined channels, overbank, and lower-fan elements. The younger UTS comprises almost...

A 66-monument geodetic array spanning the Coast Ranges near San Francisco has been surveyed more than eight times by GIPS between late 1993 and early 2001. The measured horizontal velocities of the monuments are well represented by uniform, right-lateral, simple shear parallel to N29°W. (The local strike of the San Andreas Fault is ∼N34°W.) The observed areal dilatation rate of 6.9 ± 10...

Perhaps the most difficult task facing volcanologists today is that of distinguishing between low-level volcanic restlessness and activity that presages a full-scale eruption. We illustrate these difficulties by reexamining the sequence of events that led to the 18 May 1980 eruption of Mount St. Helens, activity that is often presented as a classic example of early phreatic explosions...

A coastal vulnerability index (CVI, http://pubs.usgs.gov/of/2004/1020/html/cvi.htm) was used to map relative vulnerability of the coast to future sea-level rise within Assateague Island National Seashore (ASIS) in Maryland and Virginia. The CVI ranks the following in terms of their physical contribution to sea-level rise-related coastal change: geomorphology, regional coastal slope, rate...

The 2002 M7.9 Denali fault, Alaska, earthquake triggered thousands of landslides, primarily rock falls and rock slides, that ranged in volume from rock falls of a few cubic meters to rock avalanches having volumes as great as 15 ?? 106 m3. The pattern of landsliding was unusual; the number of slides was less than expected for an earthquake of this magnitude, and the landslides were...

The Long Valley Volcanic Field in east-central California straddles the East Sierran frontal fault zone, overlapping the Sierra Nevada and western Basin and Range Provinces. The volcanic field overlies a mature mid-Tertiary erosional surface that truncates a basement composed mainly of Mesozoic plutons and associated roof pendants of Mesozoic metavolcanic and Paleozoic metasedimentary...

Evaluation of the erosional response of 95 recently burned watersheds in Colorado, New Mexico, and southern California to storm rainfall established the factors that best differentiate between debris-flow producing basins and those that produced other flow responses. These factors are drainage-basin morphology and lithology, and the presence or absence of water-repellent soils. Basins...

The volcanic history of the Long Valley region is examined within a framework of six successive (spatially discrete) foci of silicic magmatism, each driven by locally concentrated basaltic intrusion of the deep crust in response to extensional unloading and decompression melting of the upper mantle. A precaldera dacite field (3.5–2.5 Ma) northwest of the later site of Long Valley and the...