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Geology

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2002

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Articles 31 - 60 of 123

Full-Text Articles in Physical Sciences and Mathematics

Gpr Monitoring Of Volumetric Water Content In Soils Applied To Highway Construction And Maintenance, Katherine R. Grote, Susan Sharpless Hubbard, Yoram N. Rubin May 2002

Gpr Monitoring Of Volumetric Water Content In Soils Applied To Highway Construction And Maintenance, Katherine R. Grote, Susan Sharpless Hubbard, Yoram N. Rubin

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

An overview is given on two experiments, a controlled pit study and a transportation application in subasphalt soils. Both experiments show that common-offset ground-penetrating radar (GPR) reflection data can be used to estimate θv to a high degree of accuracy. The methodology developed in these two experiments provides a technique for obtaining quick, noninvasive, accurate, and high-resolution estimates of θv.


Temporal Variation Of Seismic B-Values Beneath Northeastern Japan Island Arc, Aimin Cao, Stephen S. Gao May 2002

Temporal Variation Of Seismic B-Values Beneath Northeastern Japan Island Arc, Aimin Cao, Stephen S. Gao

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

Analysis of a high quality seismic catalog reveals that the average of seismic b-values in the crust beneath most part of northeastern Japan island arc decreased from 0.86 between 1984 and 1990, to 0.73 between 1991 and 1995. The two areas with the largest decrease are found to be in the same areas where the coupling between the North American and the Pacific plates is the highest, as suggested by a recent geodetic study. In the same time period, the annual seismic moment release increased by 10 times. In addition, there seems to be a corresponding increase in volcanic activities …


Physical And Chemical Heterogeneity In The Subsurface: Spatial Distribution Of Transport Parameters And Their Relation To Depositional Processes, Dana Divine May 2002

Physical And Chemical Heterogeneity In The Subsurface: Spatial Distribution Of Transport Parameters And Their Relation To Depositional Processes, Dana Divine

Conservation and Survey Division

This thesis consists of two parts. The goal of first section is to better understand the influence of heterogeneity on contaminant transport. This objective is approached by quantifying the heterogeneity that may have affected transport of the Stanford-Waterloo tetrachloroethene (PCE) plume. Specifically, I determine the statistical distribution of the PCE sorption distribution coefficient (Kd) at Canadian Forces Base Borden, identify the spatial distribution of Kd, and determine the cross-correlation structure between PCE Kd and permeability (k). The results show that Kd is not lognormally distributed, and that variance is insufficient to …


Defining The Hayesville–Soque River And Allatoona Faults And An Ordovician Arc Assemblage Within The Central Blue Ridge Northwest Of Dahlonega, Georgia, David Jonathan Settles May 2002

Defining The Hayesville–Soque River And Allatoona Faults And An Ordovician Arc Assemblage Within The Central Blue Ridge Northwest Of Dahlonega, Georgia, David Jonathan Settles

Masters Theses

The goal of this research within the central Blue Ridge northwest of Dahlonega, Georgia, is to provide new information toward better understanding of the Allatoona(?)/ Hayesville/Gossan Lead fault and terrane boundary, and to provide convincing evidence of Ordovician arc-related igneous activity. The Hayesville-Soque River and Allatoona faults separate three distinct tectonostratigraphic assemblages in this area: the Coweeta Group, Great Smoky Group, and Dahlonega gold belt. The gold belt here contains metasandstone, pelitic schist, and mafic rocks of the Otto Formation and the Sally Free mafic complex, while the Great Smoky Group contains metasandstone and pelitic schist with abundant calc-silicate. The …


Distribution Of Patterned Ground And Surficial Deposits On A Debris-Covered Glacier Surface In Mullins Valley And Upper Beacon Valley, Antarctica, Andrew M. Lorrey May 2002

Distribution Of Patterned Ground And Surficial Deposits On A Debris-Covered Glacier Surface In Mullins Valley And Upper Beacon Valley, Antarctica, Andrew M. Lorrey

Electronic Theses and Dissertations

Beacon Valley is located in the western Dry Valleys, Antarctica, adjacent to the East Antarctic Ice Sheet (EAIS). The surficial material on the floor of Beacon Valley is segmented into large polygonal landforms separated by trenches. Buried beneath the polygons and surficial material is massive ground ice. One hypothesis is that the buried ice in upper Beacon Valley is glacier ice originating from local debris-covered glaciers. The networks of polygons and trenches form as the buried ice undergoes thermal contraction and sublimation. Contraction cracks that penetrate the surficial material and buried ice in Beacon Valley contain Late Miocene age volcanic …


Mantle Discontinuities Beneath Southern Africa, Stephen S. Gao, Paul G. Silver, Kelly H. Liu, Kaapvaal Seismic Group May 2002

Mantle Discontinuities Beneath Southern Africa, Stephen S. Gao, Paul G. Silver, Kelly H. Liu, Kaapvaal Seismic Group

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

Seismic velocity discontinuities within the top 1000 km of the Earth beneath southern Africa are imaged by stacking about 1300 source-normalized broadband seismograms recorded by the Southern African Seismic Experiment. The Moho, 410, and 660 kilometer discontinuities are clearly detected. The mean mantle transition zone thickness is 245 km, essentially the same as the global average, suggesting that the transition zone is not anomalously warm. Thus, the lower-mantle 'African Superplume' beneath our study area has no discernible effect on transition zone temperature and is consequently confined to the lower mantle. Variations in transition zone thickness appear to be related to …


Transport Of The Herbicide Atrazine On Suspended Sediments During A Spring Storm Event In Mammoth Cave, Kentucky, Michael Anderson May 2002

Transport Of The Herbicide Atrazine On Suspended Sediments During A Spring Storm Event In Mammoth Cave, Kentucky, Michael Anderson

Masters Theses & Specialist Projects

This study examines the transport of atrazine, an herbicide used in Kentucky to control grassy and broad-leaf weeds in corn fields, on suspended sediments. Atrazine is a known carcinogen and endocrine disruptor and has been shown to be toxic at low environmental concentrations. Atrazine has the capacity to adsorb to soil particles, which in karst areas such as those found in south central Kentucky can be transported directly into the groundwater. Suspended sediments and water were collected from a well at the Hawkins River in Mammoth Cave National Park during a spring storm and tested for atrazine. Atrazine was found …


Geometry And Physical Properties Of The Chelungpu Fault, Taiwan, And Their Effect On Fault Rupture, Richard V. Heermance May 2002

Geometry And Physical Properties Of The Chelungpu Fault, Taiwan, And Their Effect On Fault Rupture, Richard V. Heermance

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Rupture of the Chelungpu fault during the September 21, 1999, 7.6 Mwearthquake in Taiwan caused a 90-Jr,m-long surface rupture with variable displacement along strike. Analysis of core from two holes drilled through the fault zone, combined with geologic mapping and detailed investigation from three outcrops, define the fault geometry and physical properties of the Chelungpu fault in its northern and southern regions. In the northern region, the fault dips 45-60° east parallel to bedding and consists of a narrow (1-20 cm) core of dark-gray, sheared clay gouge at the base of a 30-50 m zone of increased fracture …


Relationships Between Tributary Catchments, Valley-Bottom Width, Debris-Fan Area, And Mainstem Gradient On The Colorado Plateau: A Case Study In Desolation And Gray Canyons On The Green River, Caroline M. Elliott May 2002

Relationships Between Tributary Catchments, Valley-Bottom Width, Debris-Fan Area, And Mainstem Gradient On The Colorado Plateau: A Case Study In Desolation And Gray Canyons On The Green River, Caroline M. Elliott

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The alluvial forms of the rivers that drain the Colorado Plateau are a product of the water and sediment load that tributaries deliver to the trunk streams. Where the Green and Colorado Rivers cross structural barriers, narrow canyons have been incised. In the steep terrain adjacent to many of these canyons debris flows occur in the catchment basins of tributaries and deliver coarse sediment to the mainstem river corridor. Over time, debris flow deposits have aggraded in trunk stream valleys and created landforms known as debris fans. The sizes of these debris fans are related to the accommodation space available …


The Stratigraphic, Sedimentologic, And Paleogeographic Evolution Of The Eocene- Oligocene Grasshopper Extensional Basin, Southwest Montana, Joseph P. Matoush May 2002

The Stratigraphic, Sedimentologic, And Paleogeographic Evolution Of The Eocene- Oligocene Grasshopper Extensional Basin, Southwest Montana, Joseph P. Matoush

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Grasshopper basin, located in southwest Montana, is an east-tilted graben bounded by the listric Muddy-Grasshopper fault and the Meriwether Lewis fault on the eastern and western margins of the basin, respectively. This basin contains a complex stratigraphy of intertonguing facies comprised of five unconformity-bounded sequences of Tertiary alluvial, flu vial, deltaic, and lacustrine sedimentary and volcanic rocks. Sequence 1 consists of the Challis volcanic Group (Middle Eocene). The sedimentary rocks of the Medicine Lodge beds (Late Eocene-Late Oligocene) represent sequence 2 and approximately 90% of the basin-fill within Grasshopper basin. Sequence 3 consists 11 of the Sedimentary Rocks of Everson …


Structural And Kinematic Evolution Of Eocene-Oligocene Grasshopper Extensional Basin, Southwest Montana, Julie C. Kickham May 2002

Structural And Kinematic Evolution Of Eocene-Oligocene Grasshopper Extensional Basin, Southwest Montana, Julie C. Kickham

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The Grasshopper basin of southwest Montana is a complex east-dipping graben containing five unconformity-bounded sequences of Tertiary sedimentary rocks. The Eocene-Oligocene basin lies within the northern Rocky Mountain Basin and Range province. Geologic mapping in five and a half 7.5 minute quadrangles indicates that at least three distinct phases of extension characterize the Cenozoic tectonic evolution of Grasshopper basin from approximately 46 Ma to < Ma.

The significant phases of extension in Grasshopper basin were phases 1 and 3. During the first phase of extension (46-27 Ma) the nonplanar Muddy-Grasshopper fault was initiated and 90% of the basin fill was deposited. At …


Stratigraphy And Paleoecology Of The Morrison Formation, Como Bluff, Wyoming, Melissa V. Connely May 2002

Stratigraphy And Paleoecology Of The Morrison Formation, Como Bluff, Wyoming, Melissa V. Connely

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The Morrison Formation at Como Bluff, Wyoming, has been historically known for containing a rich source of Late Jurassic vertebrate fossils. However, when collected, most of these fossils were not positioned into a stratigraphic or sedimentologic framework. Research shows that the Morrison Formation at Como Bluff can be divided into three members. These members can be identified by lithologic and paleontological characteristics. The lower Morrison members include the Windy Hill Member and the recently described Lake Como Member. The Windy Hill Member primarily contains near-shore marine sandstone. Megavertebrate fauna is lacking. The Lake Como Member contains illitic clay in red …


Geology Of The Cuesta Ridge Ophiolite Remnant Near San Luis Obispo, California: Evidence For The Tectonic Setting And Origin Of The Coast Range Ophiolite, Cameron A. Snow May 2002

Geology Of The Cuesta Ridge Ophiolite Remnant Near San Luis Obispo, California: Evidence For The Tectonic Setting And Origin Of The Coast Range Ophiolite, Cameron A. Snow

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The Cuesta Ridge ophiolite is one of the best-preserved remnants of mid-Jurassic ophiolite in California. Geologic mapping and petrologic studies show that it comprises (1) harzburgite mantle tectonite, (2) dunite-rich mantle transition zone (MTZ), (3) wehrlite and pyroxenite, (4) isotropic gabbro, (5) sheeted dike/sill complex, (6) volcanic rocks (7) late-stage dikes and flows, and (8) tuffaceous radiolarian chert.

The sheeted dike/sill complex is dominated by quartz diorite, with significant modal quartz and hornblende. The volcanic section is dominated by arc tholeiite and boninitic lavas. Boninites, with high MgO, Cr, and Ni comprise 40% of the volcanic rocks. Latestage dikes and …


Sedimentology, Facies Architecture, And Reservoir Characterization Of Lacustrine Rocks, Eocene Green River And Colton Formations, Uinta Basin, Utah, Andrew W. Taylor May 2002

Sedimentology, Facies Architecture, And Reservoir Characterization Of Lacustrine Rocks, Eocene Green River And Colton Formations, Uinta Basin, Utah, Andrew W. Taylor

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Outcrop and petrographic studies of the Eocene Green River and Colton formations in the Uinta basin, Utah, document the facies architecture and heterogeneity characteristic of lacustrine reservoirs. A southwest-northeast transect of Eocene strata in the Uinta basin records three main marginal lacustrine depositional environments: fluvial, deltaic, and wave-dominated. Heterogeneity exists between and within individual depositional systems.

Reservoir rocks of Outcrops One and Two (the flu vial facies of the Colton Formation and the deltaic facies of the Green River Formation, respectively) consist of 2 to 18 m thick lenticular, tabular, or undulatory channel-fill, distributary channel, and distributary mouth bar deposits …


Evolution Of A Miocene-Pliocene Low-Angle Normal-Fault System In The Southern Bannock Range, Southeast Idaho, Stephanie M. Carney May 2002

Evolution Of A Miocene-Pliocene Low-Angle Normal-Fault System In The Southern Bannock Range, Southeast Idaho, Stephanie M. Carney

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Geologic mapping, basin analysis, and tephrochronologic analysis in the Clifton quadrangle of southeast Idaho indicates that the modern Basin-and-Range topography is only a few million years old and that the bulk of Cenozoic extension was accommodated by slip on an older low-angle normal-fault system, the Bannock detachment system. The detachment system was active between ~12 and < 4 Ma and accommodated ~50 % extension.

Cross-cutting relationships show that the master detachment fault, the Clifton fault, is the youngest low-angle normal fault of the system, was active at a low angle, and has not been rotated to a low-dip angle through time. Map patterns and relationships indicate that the …


The Formation Of Fissure Ridge Type Laminated Travertine-Tufa Deposits Microscopical Characteristics And Diagenesis, Kirşehi̇r Central Anatolia, Eşref Atabey Apr 2002

The Formation Of Fissure Ridge Type Laminated Travertine-Tufa Deposits Microscopical Characteristics And Diagenesis, Kirşehi̇r Central Anatolia, Eşref Atabey

Bulletin of the Mineral Research and Exploration

No abstract provided.


Karst Gis Advances In Kentucky, Lee J. Florea, Randall L. Paylor, Larry Simpson, Jason Gulley Apr 2002

Karst Gis Advances In Kentucky, Lee J. Florea, Randall L. Paylor, Larry Simpson, Jason Gulley

Lee J Florea, PhD, P.G.

Little statewide geospatial data was available for Kentucky caves and karst in the past. Recent trends in land development have prompted a distinct need for these data in order to help minimize impact to cave and karst resources. During the past two years, the I-66 Special Project of the National Speleological Society, The Kentucky Speleological Survey, and the Kentucky Geological Survey have gathered, archived, and developed karst data for the state. Current projects include publication of karst basin maps, archiving cave entrance locations, archiving and georeferencing cave maps, creating polygon coverages of cave conduits, and a statewide sinkhole digitization project. …


Hugo:The Hawaii Undersea Geo-Observatory, Fred K. Duennebier, David Harris, James Jolly, Jacqueline Caplan-Auerbach, Robert Jordan, Kurt Stiffel, Jeff Bosel Apr 2002

Hugo:The Hawaii Undersea Geo-Observatory, Fred K. Duennebier, David Harris, James Jolly, Jacqueline Caplan-Auerbach, Robert Jordan, Kurt Stiffel, Jeff Bosel

Geology Faculty Publications

The Hawaii Undersea Geo-Observatory, HUGO, was installed with the intent of supplying infrastructure for researchers interested in studies of undersea volcanism and associated phenomena at Loihi, the newest volcano of the Hawaiian chain. Much like an astronomical observatory, HUGO is a facility where scientists can perform experiments while sharing resources with others. The main components of HUGO are the shore station, supplying power to the observatory and recording data; the main cable-an electro-optical cable connecting the shore station to the summit of Loihi; the Junction box-the power distribution and data collection center on Loihi; multiplexing (mux) nodes-secondary distribution points; and …


Geologic Modeling Of Magnetic Data For Cypress Island, Washington, Ian Mynatt Apr 2002

Geologic Modeling Of Magnetic Data For Cypress Island, Washington, Ian Mynatt

WWU Honors College Senior Projects

Cypress Island, Washington is composed of three distinct rock units separated by two major faults with east-west trending surface traces. The rock units are from south to north; an ultramafic unit with varyingly serpentinized harzburgite, a volcanic/ sedimentary unit composed of basalt, numerous pelagic sediments and serpentine, and a greywacke unit. The orientations of the fault contacts at depth are not interpretable by surface data. This study compiled magnetic data from several sources to model subsurface geologic aspects of the island. Magnetic anomaly profiles were created from the data, then analyzed and modeled using the computer program GM-SYS. The primary …


Determining Flow Type In A Carbonate Bedrock Aquifer, Presque Isle County, Michigan, Bonny Armstrong Apr 2002

Determining Flow Type In A Carbonate Bedrock Aquifer, Presque Isle County, Michigan, Bonny Armstrong

Masters Theses

Presque Isle County, Michigan, has a long history of ground water quality problems. Aquifer contamination is most likely the result of large fractures in the bedrock allowing surface water to rapidly reach ground water. The purpose of the study is to l) perform a geochemical investigation of ground water in the bedrock aquifer, 2) suggest the type of ground water flow system present in the study area and characterize the aquifer type, and 3) suggest how the flow system might affect the behavior and transport of contaminants.

Water samples were collected from sixteen wells in the Genshaw Formation, three wells …


Stratigraphic Analysis Of Diamicton Units In Southern Allegan County, Michigan, Shannon A. Wong Apr 2002

Stratigraphic Analysis Of Diamicton Units In Southern Allegan County, Michigan, Shannon A. Wong

Masters Theses

Two diamicton units from the southern Allegan County, Michigan lakeshore bluffs were identified and differentiated through clay mineralogy by analysis of 7 /10A peak-height ratios and the 2-80 mm crystalline fraction from pebble count results. t-Tests indicate the two units are significantly different. These two units are correlated with the Saugatuck and the Ganges tills of southwest Michigan based on similarities in stratigraphic position and lithologic description as described by Monaghan et al. (1986). Other diamicton samples were collected throughout southwest Michigan, near Moline, Otsego, Bloomingdale, Gobles, and Decatur. In correlating the Saugatuck and the Ganges tills to their inland …


Sülfür Throughout Geologi̇cal Time In Balkan Peninsula, Radule Popovic Apr 2002

Sülfür Throughout Geologi̇cal Time In Balkan Peninsula, Radule Popovic

Bulletin of the Mineral Research and Exploration

No abstract provided.


A Late Pleistocene And Holocene High-Resolution Glacial And Paleoclimate Record From The Southern Sangre De Cristo Mountains, Northern New Mexico, Jake Armour Mar 2002

A Late Pleistocene And Holocene High-Resolution Glacial And Paleoclimate Record From The Southern Sangre De Cristo Mountains, Northern New Mexico, Jake Armour

Earth and Planetary Sciences ETDs

Bog deposits in the Winsor Creek drainage basin, southern Sangre de Cristo Mountains, New Mexico contain a high-resolution record of Pleistocene to Holocene glacial activity. Sediment cores were recovered from an alpine bog (elevation 3,100 m) behind a Pinedale age moraine, 2 km from a high-elevation (-3600 m) cirque. Three cores reached glacial talus and consist of -6 meters of finely laminated to coarsely laminated lake clays, grading into gyttja. Superimposed on this long-term, lake-bog transition record are many distinct coarse-grained detrital packages punctuating times of rapid environmental change.

Accelerator mass spectrometry (AMS) carbon dating, sedimentology, variations in rock magnetic …


Transition From Contraction To Extension In The Northeastern Basin And Range: New Evidence From The Copper Mountains, Nevada, Jeffrey M. Rahl, Allen J. Mcgrew, Kenneth A. Foland Mar 2002

Transition From Contraction To Extension In The Northeastern Basin And Range: New Evidence From The Copper Mountains, Nevada, Jeffrey M. Rahl, Allen J. Mcgrew, Kenneth A. Foland

Geology Faculty Publications

New mapping, structural analysis, and 40Ar/39Ar dating reveal an unusually well‐constrained history of Late Eocene extension in the Copper Mountains of the northern Basin and Range province. In this area, the northeast‐trending Copper Creek normal fault juxtaposes a distinctive sequence of metacarbonate and granitoid rocks against a footwall of Upper Precambrian to Lower Cambrian quartzite and phyllite. Correlation of the hanging wall with footwall rocks to the northwest provides an approximate piercing point that requires 8–12 km displacement in an ESE direction. This displaced fault slice is itself bounded above by another normal fault (the Meadow Fork Fault), which brings …


Sedimentology And Paleoenvironments Of The Miocene/Pliocene Pisco Fm., Perú, Cristian R. Carvajal Mar 2002

Sedimentology And Paleoenvironments Of The Miocene/Pliocene Pisco Fm., Perú, Cristian R. Carvajal

Loma Linda University Electronic Theses, Dissertations & Projects

The main objective of this research was to understand the sedimentology and depositional environment of the diatomaceous Miocene/Pliocene Pisco Formation in the Ica Valley, Perú. Four stratigraphic sections were studied, sampled and correlated. Field data were integrated with XRD, diatom taxonomy and taphonomy, and thin section analyses to define six facies.

Facies A is composed of diatomaceous siltstone with scour and fill structures formed on a shallow shelf. Facies B was deposited on the transitional zone between the shallow shelf and nearshore where tuffaceous-diatomaceous siltstone and sandstone accumulated. In facies B, lenticular laminations, and flaser, wavy and lenticular bedding record …


Longshore Sand Transport – Initial Results From The Large-Scale Sediment Transport Facility, Ping Wang, Bruce A. Ebersole, Ernest R. Smith Mar 2002

Longshore Sand Transport – Initial Results From The Large-Scale Sediment Transport Facility, Ping Wang, Bruce A. Ebersole, Ernest R. Smith

Geology Faculty Publications

Accurate predictions of the total rate of longshore sand transport (LST) and its cross-shore distribution pattern in the surf zone are central to many coastal engineering studies. Present understanding and methods for calculating the LST rate are largely developed based on field studies (e.g., Komar and Inman 1970; Inman et al. 1981; Kraus et al. 1982; Bodge and Dean 1987a, b; Dean 1989; Schoonees and Theron 1993; Miller 1998; Wang, Kraus, and Davis 1998; Wang 1998; Wang and Kraus 1999; Miller 1999). The Coastal Engineering Research Center (CERC) formula (Shore Protection Manual 1984), which is based on field measurements, is …


International Telephone Calls: Global And Regional Patterns, Risa Palm Jan 2002

International Telephone Calls: Global And Regional Patterns, Risa Palm

Geosciences Faculty Publications

This study examines patterns in international telephone communications, documenting a close relationship between international call volume aggregated by nation and indicators of global connectivity including volume of international trade, tourism and migration. In addition, the analysis documents the existence of a set of national “communities” of callers. The clear orientation of large portions of the world to former colonial powers (e.g., West Africa and North Africa to France), and the separation of the Muslim Middle East and the Chinese-speaking nations of East and Southeast Asia from other calling communities suggest the importance of continuing historic and cultural influences on information …


The Internet And Home Purchase, Risa Palm Jan 2002

The Internet And Home Purchase, Risa Palm

Geosciences Faculty Publications

In the pre-internet era, information was a key determinant of the geographic nature of intra- urban moves. Information was a far more limited commodity, and therefore subject to management and even manipulation. Information brokers, particularly real estate agents, could order and limit the kinds of information to which prospective buyers gained access, with the potential of strongly biasing search space. In the past few years, a vastly enriched information source on housing vacancies has become available through real estate industry-sponsored sites on the internet. This rich information source has the potential to influence spatial patterns and processes in the search …


Precursory Transient Slip During The 2001 MW = 8.4 Peru Earthquake Sequence From Continuous Gps, Timothy I. Melbourne, Frank H. Webb Jan 2002

Precursory Transient Slip During The 2001 MW = 8.4 Peru Earthquake Sequence From Continuous Gps, Timothy I. Melbourne, Frank H. Webb

Faculty Scholarship for the Cascadia Hazards Institute

Two-hour position estimates from a continuous GPS station located at Arequipa, Peru, document precursory deformation beginning 18 hours prior to an Mw = 7.6 aftershock of the June 23rd 2001 Mw = 8.4 earthquake. This preseismic signal appears on the north and east components as a slow displacement with an amplitude twice that of the subsequent coseismic. Analysis of three years of 18-hour rate measurement shows this signal to be unprecedented and beyond four standard deviations from the mean rate. The best fitting centroid is directionally consistent with slow slip along the plate interface and suggests the preseismic …


Impact Spherules From Western Australia: A Textural Analysis Of Really Old Tiny Rocks, Dawn C.S. Ruth Jan 2002

Impact Spherules From Western Australia: A Textural Analysis Of Really Old Tiny Rocks, Dawn C.S. Ruth

Honors Papers

The fourth shale macroband of the Dales Gorge Member of the Brockman Iron Formation in the Hamersley Basin in Western Australia contains a 2.49 billion years-old impact ejecta layer (Hassler and Simonson,2001). The S4 layer is the least studied Paleoproterozoic impact layer in the Hamersley Basin. It displays textures and replacement minerals not seen in other layers. Analysis of this layer will help our understanding of the processes that form impact ejecta, especially in the Paleoproterozoic.

It is believed that these ejecta settled in a deep basin environment; laterally extensive beds and mud-sized grains are evidence of the deep basin …