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Articles 61 - 84 of 84

Full-Text Articles in Earth Sciences

The Karst Of West-Central Florida, Lee J. Florea Aug 2006

The Karst Of West-Central Florida, Lee J. Florea

Lee J Florea, PhD, P.G.

Caves, the cornerstone feature of karst aquifers, are little understood in Florida. This dissertation, which analyzes the morphology, elevation, lithologic setting, and hydrology of caves in west-central Florida, demonstrates that the karst of the unconfined Floridan aquifer differs from the paradigm view of karst presented in modern geology textbooks. The differences reflect setting: eogenetic (west-central Florida) vs. telogenetic (conventional).


The Use Of Seismic Impedance To Locate A Discovery Well South Of Ghawar Field., Thomas M. Loretto, Adel Al-Mousa Feb 2006

The Use Of Seismic Impedance To Locate A Discovery Well South Of Ghawar Field., Thomas M. Loretto, Adel Al-Mousa

Thomas M Loretto

No abstract provided.


Le Voragini Catastrofiche Della Florida, Lee J. Florea, Robert Brooks, Tom Turner, Mario Parise Jan 2006

Le Voragini Catastrofiche Della Florida, Lee J. Florea, Robert Brooks, Tom Turner, Mario Parise

Lee J Florea, PhD, P.G.

The West-Central Florida landscape is worlds away from white-sand beaches and palm trees: gentle rolling hills, dense jungle-like forests, pine tree and palmetto scrub lands, impenetrable cypress swamps, and alligator-laden rivers. Numerous crystal-clear springs offer a glimpse of the hidden world below these wildly-diverse ecosystems. Internationally recognized in the cave diving community, Florida harbors some of the longest and most spectacular underwater cave systems. Lesser known are Florida’s “dry” caves, that rarely have large natural openings and, though often smaller than their aquatic counterparts, the beauty found within can rival the world’s best show-caves. Little was known about caves and …


Community Education In Karst At The Geological Alumni Society Geopark, University Of South Florida, Beth Fratesi, Lee J. Florea Jan 2006

Community Education In Karst At The Geological Alumni Society Geopark, University Of South Florida, Beth Fratesi, Lee J. Florea

Lee J Florea, PhD, P.G.

No abstract provided.


Cave Levels, Marine Terraces, Paleoshorelines, And The Water Table In Peninsular Florida, Lee J. Florea, H L. Vacher Jan 2006

Cave Levels, Marine Terraces, Paleoshorelines, And The Water Table In Peninsular Florida, Lee J. Florea, H L. Vacher

Lee J Florea, PhD, P.G.

Levels of passages are a common feature of many cave systems around the world. Likewise, coastal and marine terraces are common in coastal plain settings. This paper extends the discussion of cave levels from traditional research sites in the interior lowlands of the United States to the Atlantic Coastal Plains, namely peninsular Florida. Are there levels in Florida caves, and is there a link between the elevation of cave levels, marine terraces, paleoshorelines, and thus the water table, above and below present sea level in peninsular Florida?


Refine Slip Rates And Segmentation Of The Northern Sangre De Cristo Fault, Colorado’S Largest Active Fault, James P. Mccalpin Jan 2006

Refine Slip Rates And Segmentation Of The Northern Sangre De Cristo Fault, Colorado’S Largest Active Fault, James P. Mccalpin

James P. McCalpin

We excavated a 25 m-long trench on the northern part of the Crestone section of the Northern Sangre de Cristo fault zone, to see whether the Crestone section might be composed of more than one (independent) rupture segments. The Carr Gulch trench exposed evidence for 3 paleoearthquake displacements in the past 27.4 ka. The existence of 3 colluvial deposits (units 2, 3, 4) indicates that the ca. 4.5 m of surface offset was formed during 3 surface-faulting events with an average displacement of about 1.5 m each. The events occurred at about 8 ka, 20 ka, and between 22.5 and …


Using State-Wide Gis Data To Identify The Coincidence Betwen Sinkholes And Geologic Structure, Lee J. Florea Aug 2005

Using State-Wide Gis Data To Identify The Coincidence Betwen Sinkholes And Geologic Structure, Lee J. Florea

Lee J Florea, PhD, P.G.

The Kentucky GIS coverage of sinkholes, completed in 2003, consists of 101,176 polygons representing the uppermost closed contour of every karst sinkhole identified using USGS 1:24,000 scale topographic maps. This resource is a useful tool for delineating karst landscapes in Kentucky because karstified limestones underlie 55% of the areal surface of the state. For hydrologic studies, alignments of sinkholes commonly indicate preferential flowpaths for groundwater; and this information aids in large-scale planning and zoning. In this paper, I demonstrate the effectiveness of using this sinkhole coverage as a tool for delimiting structural features of Kentucky.


Constraining The Exhumation And Burial History Of The Safod Pilot Hole With Apatite Fission Track And (U-Th)/He Thermochronometry, Ann Blythe, M D’Alessio, R Bürgmann Jun 2004

Constraining The Exhumation And Burial History Of The Safod Pilot Hole With Apatite Fission Track And (U-Th)/He Thermochronometry, Ann Blythe, M D’Alessio, R Bürgmann

Ann Blythe

[1] The San Andreas Fault Observatory at Depth (SAFOD) pilot hole traverses the upper 2 km of a site 1.8 km west of the San Andreas fault (SAF) near Parkfield, California. In order to evaluate the burial and exhumation history of the site and its relationship to the kinematics and mechanics of the SAF, we use 15 apatite fission-track (FT) and 5 (U-Th)/He analyses from pilot hole samples to document their thermal history. Sample ages decrease with depth: FT and (U-Th)/He ages range from ∼60 and ∼31 Ma, respectively, in the upper 800 m of the hole to ∼3 and …


1d Energy Transport In A Strongly Scattering Laboratory Model, Kasper Van Wijk, Matt M. Haney, John A. Scales Mar 2004

1d Energy Transport In A Strongly Scattering Laboratory Model, Kasper Van Wijk, Matt M. Haney, John A. Scales

Matthew M. Haney

Radiative transfer (RT) theory is often invoked to describe energy propagation in strongly scattering media. Fitting RT to measured wave field intensities is rather different at late times, when the transport is diffusive, than at intermediate times (around one extinction mean free time), when ballistic and diffusive behavior coexist. While there are many examples of late-time RT fits, we describe ultrasonic multiple scattering measurements with RT over the entire range of times—from ballistic to diffusive. In addition to allowing us to retrieve the scattering and absorption mean free paths independently, our results also support theoretical predictions in 1D that suggest …


Stacking Velocities As Geopressure Indicators In Ghawar And Red Sea Areas, Saudi Arabia., Thomas M. Loretto Feb 2004

Stacking Velocities As Geopressure Indicators In Ghawar And Red Sea Areas, Saudi Arabia., Thomas M. Loretto

Thomas M Loretto

No abstract provided.


Breakdown Ofwave Diffusion In 2d Due To Loops, Matt M. Haney, Roel Snieder Aug 2003

Breakdown Ofwave Diffusion In 2d Due To Loops, Matt M. Haney, Roel Snieder

Matthew M. Haney

The validity of the diffusion approximation for the intensity of multiply scattered waves is tested with numerical simulations in a strongly scattering 2D medium of finite extent. We show that the diffusion equation underestimates the intensity and attribute this to both the neglect of recurrent scattering paths and interference within diffusion theory. We present a theory to quantify this discrepancy based on counting all possible scattering paths between point scatterers. Interference phenomena, due to loop paths, are incorporated in a way similar to coherent backscattering.


On Porosity Prediction From Seismic Data In Ghawar Field, Saudi Arabia, Thomas M. Loretto Sep 2002

On Porosity Prediction From Seismic Data In Ghawar Field, Saudi Arabia, Thomas M. Loretto

Thomas M Loretto

No abstract provided.


On The Feasibility Of Geopressure Detection From Seismic Data In Saudi Arabia., Thomas M. Loretto, James J. Funk Feb 2002

On The Feasibility Of Geopressure Detection From Seismic Data In Saudi Arabia., Thomas M. Loretto, James J. Funk

Thomas M Loretto

No abstract provided.


Detection Of Iapetan Rifting (Rome Trough Tectonism) By Quaternary Karstification: Pulaski County, Kentucky, Lee J. Florea Jan 2002

Detection Of Iapetan Rifting (Rome Trough Tectonism) By Quaternary Karstification: Pulaski County, Kentucky, Lee J. Florea

Lee J Florea, PhD, P.G.

No abstract provided.


Wide Plate Margin Deformation, Southern Central America And Northwestern South America, Casa Gps Observations, James Kellogg Dec 2001

Wide Plate Margin Deformation, Southern Central America And Northwestern South America, Casa Gps Observations, James Kellogg

James N Kellogg

Global Positioning System (GPS) data from southern Central America and northwestern South America were collected during 1991, 1994, 1996, and 1998 in Costa Rica, Panama, Ecuador, Colombia and Venezuela. These data reveal wide plate boundary deformation and escape tectonics occurring along an approximately 1400 km length of the North Andes; locking of the subducting Nazca plate and strain accumulation in the Ecuador-Colombia forearc; ongoing collision of the Panama arc and Colombia; and convergence of the Caribbean plate with Panama and South America. Elastic modeling of observed horizontal displacements in the Ecuador forearc is consistent with partial locking (50%) in the …


Long Recurrence Records From The Wasatch Fault Zone, Utah, James P. Mccalpin Jan 2001

Long Recurrence Records From The Wasatch Fault Zone, Utah, James P. Mccalpin

James P. McCalpin

The Wasatch fault "megatrench" was excavated in September 1999 across two fault scarps totaling 18 meters high on the Salt Lake City segment of the Wasatch fault zone (WFZ). The purpose of the megatrench was to date a long series of consecutive earthquakes (8-12 events?) on the WFZ and measure the variability of recurrence times between the events.This variability could then be used in calculating the future probability of large earthquakes on the WFZ. The trench was located 1 km north of the mouth of Little Cottonwood Canyon, at an elevation of 1525 m, between the Bonneville highstand (ca. 17.5 …


Paleoseismicity Of Quaternary Faults Near Albuquerque, New Mexico: The Zia Fault, James P. Mccalpin Jan 2001

Paleoseismicity Of Quaternary Faults Near Albuquerque, New Mexico: The Zia Fault, James P. Mccalpin

James P. McCalpin

This study continues USGS-funded efforts to assess the activity and earthquake hazard potential of Quaternary faults in the Albuquerque metropolitan region. Our target in 2000 was the Zia fault, a 37 km-long normal fault that trends N-S in northern Llano de Albuquerque (LdA). The Zia fault is one of three major east-dipping normal faults that define the western margin of the Rio Grande rift in the northern Albuquerque basin, the other faults being the Calabacillas fault (to the west of the Zia fault) and the County Dump fault (to the east of the Zia fault) (Machette et al., 1998). In …


Correction Of Seismic Amplitude Maps To Validate Amplitude Derived Porosity Inferences., Thomas M. Loretto Feb 2000

Correction Of Seismic Amplitude Maps To Validate Amplitude Derived Porosity Inferences., Thomas M. Loretto

Thomas M Loretto

No abstract provided.


Ridgetop Splitting, Spreading, And Shattering Related To Earthquakes In Southern California, James P. Mccalpin Jan 1998

Ridgetop Splitting, Spreading, And Shattering Related To Earthquakes In Southern California, James P. Mccalpin

James P. McCalpin

Our mapping documents that anomalous ridgetop landforms are numerous in the San Gabriel and Santa Susana Mountains, and that many sites (37% of the San Gabriel sites, 16% of the Santa Susana sites) are not associated with any visible signs of landsliding. These sites may represent deep-seated gravitational spreading due to earthquake shaking. However, our factor analysis indicates that the spatial distribution of these suspected spreading landforms, with respect to ridge relief and distance to Late Quaternary faults, is essentially identical to that of landslides. Thus, it seems that if these spreading landforms represent the results of earthquake shaking, than …


Statistics Of Paleoseismic Data, James P. Mccalpin Jan 1998

Statistics Of Paleoseismic Data, James P. Mccalpin

James P. McCalpin

Compiled data from numerous neotectonic-geomorphic and trench studies reveals patterns in the spatial and temporal variation of coseismic fault displacement. Recurrence intervals between successive large earthquakes on faults define a near-symmetrical probability distribution with a coefficient of variance of 0.36. Normal faults have the most regular recurrence, and subduction zones the most variable. Variability in recurrence times at a site is not dependent on the number of recurrence intervals dated at that site. During historic surface-rupturing earthquakes slip has varied widely along strike. Based on 56 ruptures where more than 15 displacement measurements were made, the generic pattern is for …


Recommended Setback Distances From Active Normal Faults, James P. Mccalpin Jan 1987

Recommended Setback Distances From Active Normal Faults, James P. Mccalpin

James P. McCalpin

The geometry of near-surface ground breakage was analyzed from 40 trenches across Quaternary normal faults to help define reasonable setback distances. From each of the trench logs (28 on the Wasatch Fault, 11 on other Great Basin faults) eight parameters characteristic of surface rupture style were measured. Parameters included: 1) position of the main fault in relation to scarp morphology. 2) dip of the main fault. 3) number of faults on the upthrown block, 4) width of the upthrown block fault zone. 5) number of faults in the downthrown block. 6) width of the downthrown deformation zone, 7) ratio of …


Preliminary Age Classification Of Landslides For Inventory Mapping, James P. Mccalpin Jan 1984

Preliminary Age Classification Of Landslides For Inventory Mapping, James P. Mccalpin

James P. McCalpin

A preliminary age classification for landslides is proposed for inventory mapping, based on morphologic criteria visible on aerial photographs. Because landslide scars and deposits are generally disequilibrium landforms, they progress through observable morphologic stages as they age. Four age classes are distinguished: 1) active; 2) inactive-young; 3) inactive-mature; 4) inactive-old. Each age class reflects the age of latest movement only. The morphologic "freshness" of each part of the landslide must be evaluated, including: the head scarp, lateral scarps, marginal drainage, internal scarps and blocks, internal drainage pattern, vegetation type and density, and toe morphology. Morphologic parameters defined from air photos …


Subduction Of The Caribbean Plate And Basement Uplifts In The Overriding South American Plate, James N. Kellogg, William E. Bonini May 1982

Subduction Of The Caribbean Plate And Basement Uplifts In The Overriding South American Plate, James N. Kellogg, William E. Bonini

James N Kellogg

Abstract. The new tectonic interpretations presented in this paper are based on geologic field mapping and gravity data supplemented by well logs, seismic profiles, and radiometric and earthquake data. The present Caribbean-South American plate boundary is the South Caribbean marginal fault, where subduction is indicated by folding and thrusting in the deformed belt and a seismic zone that dips 30o to the southeast and terminates 200 km below the Maracaibo Basin. The Caribbean-South American convergence rate is estimated as 1.9 +_. 0.3 cm/yr on the basis of the 390-km length of the seismic zone and a thermal equilibration time of …


Areal Distribution, Thickness, Mass, Volume, And Grain Size Of Air-Fall Ash From The Six Major Eruptions Of 1980, Andrei M. Sarna-Wojcicki, Susan Shipley, Richard B. Waitt Jr., Daniel Dzurisin, Spencer H. Wood Jan 1981

Areal Distribution, Thickness, Mass, Volume, And Grain Size Of Air-Fall Ash From The Six Major Eruptions Of 1980, Andrei M. Sarna-Wojcicki, Susan Shipley, Richard B. Waitt Jr., Daniel Dzurisin, Spencer H. Wood

Spencer H. Wood

The airborne-ash plume front from the Mount St. Helens eruption of May 18 advanced rapidly to the northeast at an average velocity of about 250 km/hr during the first 13 min after eruption. It then traveled to the east-northeast within a high-velocity wind layer at altitudes of 10-13 km at an average velocity of about 100 km/hr over the first 1,000 km. Beyond about 60 km, the thickest ash fall was east of the volcano in Washington, northern Idaho, and western Montana. A distal thickness maximum near Ritzville, Wash., is due to a combination of factors: (1) crude sorting within …