Digital Commons Network^™

Systematic Revision Of The Genus Eupleura H. And A. Adams, 1853 (Gastropoda: Muricidae) In The Neogene To Recent Of Tropical America, Gregory S. Herbert

School of Geosciences Faculty and Staff Publications

The systematics of the Neogene to Recent genus Eupleura of tropical America are revised, with descriptions of four new species: Eupleura engerrabunda, from the Late Miocene of Mexico (Atlantic); Eupleura gravidentata, from the Plio-Pleistocene of Colombia (Atlantic); Eupleura paroudia, from the Early or middle Pliocene of Mexico (Atlantic); and Eupleura vokesorum, from the Pliocene of Costa Rica (Pacific) and Ecuador and the Recent tropical eastern Pacific. Two recent taxa, Eupleura plicata and Eupleura limata, are also resurrected, increasing the standing diversity of Eupleura in the eastern Pacific to seven species. Eupleura limata, however, may …

Geodetic Gps Measurements In South Iceland: Strain Accumulation And Partitioning In A Propagating Ridge System, P. C. Lafemina, Timothy H. Dixon, R. Malservisi, T. Arnadottir, E. Sturkell, F. Sigmundsson, P. Einarsson

School of Geosciences Faculty and Staff Publications

GPS observations in south Iceland between 1994 and 2003 are compared with two-dimensional elastic half-space and viscoelastic coupling models for two parallel rift zones, representing the Western and Eastern volcanic zones (WVZ, EVZ). GPS data from the Hreppar block, between the WVZ and EVZ, fit a rigid block model within uncertainties. Spreading rates across the WVZ increase from 2.6 ± 0.9 mm/yr in the northeast to 7.0 ± 0.4 mm/yr in the southwest. Conversely, spreading rates in the EVZ decrease from 19.0 ± 2.0 mm/yr in the northeast to 11.0 ± 0.8 mm/yr in the southwest, the direction of ridge …

The 7 May 2001 Induced Seismic Event In The Ekofisk Oil Field, North Sea, L. Ottemöller, H. H. Nielsen, K. Atakan, Jochen Braunmiller, J. Havskov

School of Geosciences Faculty and Staff Publications

A moderate size seismic event on 7 May 2001 was strongly felt on platforms in the Ekofisk oil field, in the southern North Sea, but did not cause damage to platforms or wells. We combined near- and far-field observations to develop a consistent source model and to determine whether the event was induced. Seismic data placed the epicenter inside the Ekofisk field and suggested a shallow source depth based on spectral and moment tensor analysis. GPS data from the Ekofisk platforms displayed permanent vertical and horizontal movement due to the event. A topographic bulge in the sea bottom, revealed by …

Degassing And Hydrothermal Activity At Mt. Spurr, Alaska During The Summer Of 2004 Inferred From The Complex Frequencies Of Long-Period Events, S. De Angelis, Stephen R. Mcnutt

School of Geosciences Faculty and Staff Publications

Results of analyses of unusual long-period earthquakes, recorded between July and September 2004 at Mt. Spurr, Alaska, are presented. The waveforms of these events are characterized by quasi-sinusoidal signatures of long duration (up to 40 sec) with slowly decaying amplitudes; bandwidths of 0.5–4.0 Hz are typical; amplitude spectra are marked by strong and sharp peaks, reflecting the quasi-monochromatic nature of the signal. The temporal variations of the complex frequencies are investigated by use of the Sompi method; the dominant mode is resolved and its Q factor estimated for each available event. Dominant frequencies are found in the band 0.8–2.2 Hz …

Hydrology Of Vernal Pools At Three Sites, Southern Sacramento Valley, Robert J. Williamson, Graham E. Fogg, Mark C. Rains, Thomas H. Harter

School of Geosciences Faculty and Staff Publications

The subsurface hydrology of vernal pools at three vernal pool complexes was investigated during three wet seasons in 2002-2004. The complexes were at Gridley Ranch, Valensin Ranch, and the Mather Field in northern California. The selected complexes provided variation in soils, landforms and topography. Three vernal pools were chosen in each complex based on variation in pool type, size, and position in the drainage system. The objectives were to describe the subsurface hydrology of vernal pools to refine the conceptual model of vernal pool hydrology and to answer questions about: the size of watershed support for vernal pools, the importance …

The 2003 Boumerdes, Algeria Earthquake: Regional Moment Tensor Analysis, Jochen Braunmiller, Fabrizio Bernardi

School of Geosciences Faculty and Staff Publications

We used regional broadband seismograms to determine seismic moment tensors for the destructive May 21, 2003 Boumerdes (Algeria) M_w = 7.0 earthquake and its larger aftershocks. Fully automatic inversions using near-real time data provided solutions for seven M_w ≥ 4.7 events within 90 minutes after event occurrence. After adding off-line data, we manually obtained 30 solutions (M_w ≥ 3.8) from May 2003 to January 2004. All have shallow source depths (6–21 km). The median P-axis orientation (338°) of 24 thrust and four strike-slip events is consistent with Africa-Eurasia plate motion (330°). The main shock hypocenter at 8–10 …

Numerical Simulation Of Double‐Diffusive Finger Convection, Joseph D. Hughes, Ward E. Sanford, H. L. Vacher

School of Geosciences Faculty and Staff Publications

A hybrid finite element, integrated finite difference numerical model is developed for the simulation of double‐diffusive and multicomponent flow in two and three dimensions. The model is based on a multidimensional, density‐dependent, saturated‐unsaturated transport model (SUTRA), which uses one governing equation for fluid flow and another for solute transport. The solute‐transport equation is applied sequentially to each simulated species. Density coupling of the flow and solute‐transport equations is accounted for and handled using a sequential implicit Picard iterative scheme. High‐resolution data from a double‐diffusive Hele‐Shaw experiment, initially in a density‐stable configuration, is used to verify the numerical model. The temporal …

Assembly Focuses On Volcanism And Societal Impacts, Anita Grunder, Stephen R. Mcnutt

School of Geosciences Faculty and Staff Publications

With a theme of “Volcanism and Its Impact on Society,” the November 2004 meeting of the International Association of Volcanology and Chemistry of the Earth's Interior (IAVCEI) held in Pucón, Chile, brought together experts to discuss many aspects of volcanology.

The five‐day IAVCEI meeting was the association's largest, attracting 940 participants from 44 countries. U.S. participants constituted one third. The meeting consisted of over 1100 abstracts presented in 12 theme sessions, and reflected a diversity of disciplines and techniques encompassed by volcanic studies.