Earth Sciences Commons^™

Extremely Slow Feeding In A Tropical Drilling Ectoparasite, Vitularia Salebrosa (King And Broderip, 1832) (Gastropoda: Muricidae), On Molluscan Hosts From Pacific Panama, Gregory S. Herbert, Gregory P. Dietl, Helena Fortunato, Luiz R. L. Simone, Jennifer Leigh Sliko

School of Geosciences Faculty and Staff Publications

This study documents one of the slowest feeding behaviors ever recorded for a muricid gastropod in one of the most biotically rigorous regions on the planet. In Pacific Panama, Vitularia salebrosa attacks mollusks by drilling through their shells. The duration of attacks estimated by isotope sclerochronology of oyster shells collected during attacks in progress ranges from 90 to 230 days, while experimental observation of interactions documented one attack greater than 103 days. The prolonged nature of attacks suggests that V. salebrosa is best characterized as an ectoparasite than as a predator, which is the ancestral condition in the Muricidae. An …

Segmentation Of The Blanco Transform Fault Zone From Earthquake Analysis: Complex Tectonics Of An Oceanic Transform Fault, Jochen Braunmiller, John Nábělek

School of Geosciences Faculty and Staff Publications

The Blanco Transform Fault Zone (BTFZ) forms the ∼350 km long Pacific–Juan de Fuca plate boundary between the Gorda and Juan de Fuca ridges. Nearby broadband seismic networks provide a unique framework for a detailed, long-term seismotectonic study of an entire oceanic transform fault (OTF) system. We use regional waveforms to determine 129 earthquake source parameters; combined with 28 Harvard moment tensors, they represent the largest waveform derived OTF source parameter data set. Joint epicenter determination removes the northeasterly routine location bias. Projecting seismicity onto the BTFZ, we determine along-fault seismic slip rate variations. Earthquake source parameters and morphology indicate …

Alaska's Pavlof Volcano Ends 11-Year Repose, Christopher F. Waythomas, Stephanie G. Prejean, Stephen R. Mcnutt

School of Geosciences Faculty and Staff Publications

After an 11-year period of repose, Pavlof volcano on the Alaska Peninsula (Figure 1) began an episode of Strombolian eruption lasting 31 days, from 14 August to 13 September 2007.

The eruption began abruptly on 14 August after a minor increase in seismicity the previous day. Nearly continuous lava fountaining, explosions, and lahars caused by minor disruption of the ice and snow cover on the volcano characterized the eruption. The eruption also produced diffuse ash plumes that reached 5–6 kilometers above sea level, but the plumes were too small and did not extend high enough to affect local or regional …

Moho Depth And Poisson's Ratio In The Western–Central Alps From Receiver Functions, D. Lombardi, Jochen Braunmiller, E. Kissling, D. Giardini

School of Geosciences Faculty and Staff Publications

Current knowledge about deep crustal structure of the Alpine orogen has mainly been derived from P-wave velocity models obtained from active and passive seismic experiments. A complementary S-wave model to provide lithological constraints necessary for unique structural interpretation has been missing to date. In this paper, we present important new information on S-wave velocity model in the Alps. We applied the receiver function method using 6 yr of high quality data from 61 permanent and temporary stations sampling the Western–Central Alps. We determined first-order crustal features Moho depth (H) and average Vp/Vs ratio …

A Large New Species Of Lobatus (Gastropoda: Stromnidae) From The Neogene Of The Dominican Republic, With Notes On The Genus, Bernard M. Landau, Gijs C. Kronenberg, Gregory S. Herbert

School of Geosciences Faculty and Staff Publications

No abstract provided.

Earth Scientists And Public Policy: Have We Failed New Orleans?, Timothy H. Dixon, Roy K. Dokka

School of Geosciences Faculty and Staff Publications

Earth scientists rarely influence public policy or urban planning. In defiance of geologic reality, cities are established on or expanded into floodplains, wetlands, earthquake faults, and active volcanoes. One exception to our lack of influence is that shortly after a major natural disaster, there is a brief window of heightened public awareness that may lead to sensible regulation or relocation of infrastructure. After the 1933 Long Beach earthquake, for example, California building codes were improved to reduce earthquake hazard. After Mississippi River flooding in 1993, several U.S. cities designated parts of their low-lying flood-plain as green space.

Rethinking Early Earth Phosphorus Geochemistry, Matthew A. Pasek

School of Geosciences Faculty and Staff Publications

Phosphorus is a key biologic element, and a prebiotic pathway leading to its incorporation into biomolecules has been difficult to ascertain. Most potentially prebiotic phosphorylation reactions have relied on orthophosphate as the source of phosphorus. It is suggested here that the geochemistry of phosphorus on the early Earth was instead controlled by reduced oxidation state phosphorus compounds such as phosphite (HPO₃ ²⁻), which are more soluble and reactive than orthophosphates. This reduced oxidation state phosphorus originated from extraterrestrial material that fell during the heavy bombardment period or was produced during impacts, and persisted in the mildly reducing atmosphere. …

Combination Of Sar Remote Sensing And Gis For Monitoring Subglacial Volcanic Activity – Recent Results From Vatnajökull Ice Cap (Iceland), K. Scharrer, Rocco Malservisi, Ch. Mayer, O. Spieler, U. Münzer

School of Geosciences Faculty and Staff Publications

This paper presents latest results from the combined use of SAR (Synthetic Aperture Radar) remote sensing and GIS providing detailed insights into recent volcanic activity under Vatnajökull ice cap (Iceland). Glaciers atop active volcanoes pose a constant potential danger to adjacent inhabited regions and infrastructure. Besides the usual volcanic hazards (lava flows, pyroclastic clouds, tephra falls, etc.), the volcano-ice interaction leads to enormous meltwater torrents (icelandic: jökulhlaup), devastating large areas in the surroundings of the affected glacier. The presented monitoring strategy addresses the three crucial questions: When will an eruption occur, where is the eruption site and which area is …

Variable Intensity Of Teleconnections During The Late Holocene In Subtropical North America From An Isotopic Study Of Speleothem From Florida, Philip E. Van Beynen, Yemane Asmerom, Victor J. Polyak, Limaris R. Soto, Jason S. Polk

School of Geosciences Faculty and Staff Publications

The persistence and influence of both tropical and extra‐tropical teleconnections on the hydrology of subtropical North America are little understood. Major atmospheric‐oceanic controls on the isotopic composition of the precipitation reconstructed from a 1,000 year old stalagmite are the North Atlantic Oscillation (NAO) and the Pacific Decadal Oscillation (PDO). These teleconnections create decadal‐ to centennial‐scale changes in the seasonal distribution of precipitation. An increase in the winter proportion of annual precipitation coincides with negative phase NAO conditions and a positive phase PDO. However, the PDO's influence appears to be weakened when it is out of phase with the El Niño …

Geodetic, Teleseismic, And Strong Motion Constraints On Slip From Recent Southern Peru Subduction Zone Earthquakes, M. E. Pritchard, E. O. Norabuena, C. Ji, R. Boroschek, D. Comte, M. Simons, Timothy H. Dixon, P. A. Rosen

School of Geosciences Faculty and Staff Publications

We use seismic and geodetic data both jointly and separately to constrain coseismic slip from the 12 November 1996 M_w 7.7 and 23 June 2001 M_w 8.5 southern Peru subduction zone earthquakes, as well as two large aftershocks following the 2001 earthquake on 26 June and 7 July 2001. We use all available data in our inversions: GPS, interferometric synthetic aperture radar (InSAR) from the ERS-1, ERS-2, JERS, and RADARSAT-1 satellites, and seismic data from teleseismic and strong motion stations. Our two-dimensional slip models derived from only teleseismic body waves from South American subduction zone earthquakes with M …

Kinematics Of The Nicaraguan Forearc From Gps Geodesy, Henry L. Turner, Peter Lafemina, Armando Saballos, Glen S. Mattioli, Pamela E. Jansma, Timothy H. Dixon

School of Geosciences Faculty and Staff Publications

Campaign GPS data from a network in the Nicaraguan forearc show a strong component of arc-parallel motion indicating northwest translation of a nearly rigid forearc sliver. Our measured mean velocity for forearc sites of 15.1 mm yr⁻¹ agrees well with the arc-parallel sliver motion predicted previously by DeMets (2001) derived from closure constraints on oblique convergence between the Cocos and Caribbean plates. The lack of a northeasterly oriented arc-normal component of motion in forearc velocities indicates that there are complexities involved beyond a simple interpretation of sliver motion being driven by oblique convergence. The forearc is reasonably well-fit by …

Observation Of Glacial Isostatic Adjustment In “Stable” North America With Gps, Giovanni F. Sella, Seth Stein, Timothy H. Dixon, Michael Craymer, Thomas S. James, Stephane Mazzotti, Roy K. Dokka

School of Geosciences Faculty and Staff Publications

Motions of three hundred and sixty Global Positioning System (GPS) sites in Canada and the United States yield a detailed image of the vertical and horizontal velocity fields within the nominally stable interior of the North American plate. By far the strongest signal is the effect of glacial isostatic adjustment (GIA) due to ice mass unloading during deglaciation. Vertical velocities show present-day uplift (∼10 mm/yr) near Hudson Bay, the site of thickest ice at the last glacial maximum. The uplift rates generally decrease with distance from Hudson Bay and change to subsidence (1–2 mm/yr) south of the Great Lakes. The …

Tectonic Control Of Subsidence And Southward Displacement Of Southeast Louisiana With Respect To Stable North America, Roy K. Dokka, Giovanni F. Sella, Timothy H. Dixon

School of Geosciences Faculty and Staff Publications

GPS data collected between 1995 and 2006 suggest that southeast Louisiana, including New Orleans and the larger Mississippi Delta, are both subsiding vertically and moving southward with respect to stable North America. Both motions are likely related due to their common tectonic setting. Subsidence in the New Orleans area occurs in part because it is located in the hanging wall of a large listric normal fault system that forms the northern boundary of a 7–10 km thick allochthon that is detached from stable North America. Southward motion of this allochthon relative to stable North America occurs at 2.2 ± 0.6 …

Local Infrasound Observations Of Large Ash Explosions At Augustine Volcano, Alaska, During January 11-28, 2006, Tanja Petersen, Silvio De Angelis, Guy Tytgat, Stephen R. Mcnutt

School of Geosciences Faculty and Staff Publications

We present and interpret acoustic waveforms associated with a sequence of large explosion events that occurred during the initial stages of the 2006 eruption of Augustine Volcano, Alaska. During January 11–28, 2006, 13 large explosion events created ash-rich plumes that reached up to 14 km a.s.l., and generated atmospheric pressure waves that were recorded on scale by a microphone located at a distance of 3.2 km from the active vent. The variety of recorded waveforms included sharp N-shaped waves with durations of a few seconds, impulsive signals followed by complex codas, and extended signals with emergent character and durations up …

Is There A Northern Lesser Antilles Forearc Block?, A. M. Lopez, S. Stein, Timothy H. Dixon, G. Sella, E. Calais, P. Jansma, J. Weber, P. Lafemina

School of Geosciences Faculty and Staff Publications

A systematic discrepancy exists between slip vectors of thrust fault earthquakes at the Lesser Antilles trench (LAT) and the predicted direction of North American‐Caribbean convergence. A possibility has been that the discrepancy resulted because neither was well constrained. Estimating Caribbean motion has been challenging owing to the limited data along the plate's complex boundaries. Similarly, earlier studies had few slip vectors because interplate thrust events are infrequent. To address these difficulties, we estimate a new Caribbean‐North America Euler vector using recently available GPS data from sites in the presumably stable interior of the Caribbean, and compare the predicted velocities to …

Strain Accumulation Across The Carrizo Segment Of The San Andreas Fault, California: Impact Of Laterally Varying Crustal Properties, Gina Schmalzle, Timothy H. Dixon, Rocco Malservisi, Rob Govers

School of Geosciences Faculty and Staff Publications

Major strike slip faults juxtapose geologically dissimilar terrain which may vary in mechanical properties, leading to an asymmetric pattern of strain accumulation. We present new GPS data on the Carrizo segment of the San Andreas Fault, separating the Salinian block southwest of the fault from Franciscan terrane northeast of the fault, to better quantify asymmetric strain accumulation. We also present a series of finite element models to investigate the possible role of variable elastic layer thickness and material properties of the upper crust. The geodetic data are well fit with a simple model comprising a weak upper crustal zone 10–25 …

Dry Creek Long Term Watershed Study: Buffer Zone Performance As Viable Amphibian Habitat, Brooke L. Talley, Thomas Crisman

School of Geosciences Faculty and Staff Publications

As bioindicators, amphibians typically require both terrestrial and aquatic habitats to complete their life cycles. Pre- timber-harvest monitoring (December 2002 through September 2003) of salamander and frog (Hylidae) populations was conducted in four watersheds of Decatur County, GA. Post- timber-harvest monitoring (December 2003 through September 2004) continued in the same watersheds (two reference and two treatment watersheds). Coverboards were used to monitor adult salamanders, larval salamanders were surveyed with dipnet sweeps, and frogs were monitored with vertical PVC pipes. Six salamander species (Desmognathus apalachicolae, Eurycea cirrigera, E. guttolineata, Notophthalmus viridescens, Plethodon grobmani, and Pseudotriton ruber) and five frog species (Hyla …

Dry Creek Long Term Watershed Study: Assessment Of Immediate Response Of Aquatic Macroinvertebrates To Watershed Level Harvesting And Thinning Of Streamside Management Zones, M. W. Griswold, R. T. Winn, Thomas Crisman, W. R. White

School of Geosciences Faculty and Staff Publications

Streamside Management Zones (SMZs) are meant to protect riparian habitat and the stream ecosystem. Benthic macroinvertebrates are recognized bioindicators of water quality in streams, typically occupying multiple trophic levels in these systems and providing food for vertebrates. Thus, it is important to understand the effects of harvest within and adjacent to the SMZ on macroinvertebrate assemblages. Benthic macroinvertebrates were sampled pre- and post-harvest from four firstorder streams draining the Dry Creek watershed in southwestern Georgia. A multi-habitat sampling procedure was used. Macroinvertebrates were identified and compared using biotic indices. Comparisons were made between streams within the pre-harvest period and between …

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 …

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.

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 …

Locating A Radioactive Waste Repository In The Ring Of Fire, Mick Apted, Kelvin Berryman, Neil Chapman, Mark Cloos, Charles B. Connor, Kazumi Kitayama, Steve Sparks, Hiroyuki Tsuchi

School of Geosciences Faculty and Staff Publications

The scientific, technical, and sociopolitical challenges of finding a secure site for a geological repository for radioactive wastes have created a long and stony path for many countries. Japan carried out many years of research and development before taking its first steps in site selection.

The Nuclear Waste Management Organization of Japan (NUMO) began looking for a high-level waste repository site (HLW, vitrified residue from reprocessing power reactor fuel) 2 years ago. Over the next 10–20 years, NUMO hopes to find a site to dispose of ∼20,000 tons of HLW in a robustly engineered repository constructed at a depth of …

Geodetic And Sconstraints On Some Seismogenic Zone Processes In Costa Rica, Edmundo Norabuena, Timothy H. Dixon, Susan Schwartz, Heather Deshon, Andrew Newman, Marino Protti, Victor Gonzalez, Leroy Dorman, Ernst R. Flueh, Paul Lundgren, Fred Pollitz, Dan Sampson

School of Geosciences Faculty and Staff Publications

New seismic and geodetic data from Costa Rica provide insight into seismogenic zone processes in Central America, where the Cocos and Caribbean plates converge. Seismic data are from combined land and ocean bottom deployments in the Nicoya peninsula in northern Costa Rica and near the Osa peninsula in southern Costa Rica. In Nicoya, inversion of GPS data suggests two locked patches centered at 14 ± 2 and 39 ± 6 km depth. Interplate microseismicity is concentrated in the more freely slipping intermediate zone, suggesting that small interseismic earthquakes may not accurately outline the updip limit of the seismogenic zone, the …

Space-Based Measurements Of Sheet Flow Characteristics In The Everglades, Wetland, Florida, Shimon Wdowinski, Falk Amelung, Fernando Miralles-Wilhelm, Timothy H. Dixon, Richard Carande

School of Geosciences Faculty and Staff Publications

New space-based observations of South Florida with interferometric SAR (InSAR) reveal spatially detailed, quantitative images of water levels in the Everglades. The new data capture dynamic water level topography, providing the first detailed picture of wetland sheet flow. We observe localized radial sheet flow in addition to well-known southward unidirectional sheet flow, modelled as a linear diffusive flow. We obtain quantitative estimates of flow diffusivity (23–91 m²/s), the first space-based estimates of such hydrologic parameter for the Everglades. Space-based hydrologic observations can provide critical information for monitoring, understanding and managing wetland sheet flow, and contribute to wetland restoration.

“Coupling” Semantics And Science In Earthquake Research, Kelin Wang, Timothy H. Dixon

School of Geosciences Faculty and Staff Publications

Coupling is a convenient word that describes a wide variety of interactions or feedback processes, including those that we do not fully understand. Examples in Earth science include ocean-atmosphere coupling, climate-tectonics coupling, and core-mantle coupling. The word is also very popular in discussions of plate boundary earthquake processes.

As a vague expression, fault coupling is a perfectly adequate term, describing some kind of mechanical interaction between rocks of each side of a fault. For those of us who try to infer fault processes from geodetic measurements, coupling usually indicates a state of no or low current slip. If a fault …