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At least 1,387 records · Page 77Linked to original sources
USGS1981

Seismic-reflection and sidescan-sonar data collected off eastern Cape Cod, Massachusetts, during April 1979

The U.S. Geological Survey collected 98 line kilometers of single-channel seismic-reflection profiles and sidescan sonar records on the inner shelf of eastern Cape Cod, Massachusetts, during April 1979. The data were obtained during cruise NE-1-79 of the R/V NEECHO. The purposes of the survey were: (1) to study the development of barrier islands; (2) to document the frequency and rate of migration of inlets that breach barrier islands; and (3) to define the characteristics of shoreface ridges on a barrier island. he survey uti I ized two acoustic systems. Information about the bottom was obtained by using an EDO Western model 606 sidescan-sonar system (100 kHz). Profiles of the subbottom were collected by an EG&G Uni boom transducer (400-4,000 Hz) and a Del Norte streamer. Positional control for al I track! ines was provided by a shore-based Miniranger system and by LORAN-C. The quality of the records generally is very good. However, subbottom penetration did vary somewhat from place to place during the survey due to the nature of the bottom sediments and to the presence or absence of buried channels. The original records may be examined at the U.S. Geological Survey, Woods Hole, MA 02543. Microfilm copies of the data are avai I able for purchase from the National Geophysical pnd Solar-Terrestrial Data Center, NOAA/EDIS/NGSDC, Code D621, 325 Broadway, Boulder, CO 80303 (303-497-6338).

Open-File Report↗
USGS1981

Vertical displacement measurements in Central California with a long-baseline two-fluid tiltmeter

The need for a water-tube tiltmeter and the details of its operation were covered by Eaton [1] in 1959. Since that time more modern instrumentation has allowed modification and further development beyond the basic single-tube fluid tiltmeter with a mechanical surface sensor. A number of instruments are discussed in connection with thermal errors in a paper by Bevan and Bilham [2] including one due to Huggett, et al. [3]. This particular instrument, the two-fluid tiltmeter, is the subject of this project. A laboratory single leg prototype developed by Terra Technology Corporation [4] was modified and expanded for use in a field test site in central California. The two major differences in this fluid tiltmeter are the use of two parallel tubes filled with fluids of different thermal properties experiencing the same thermal environment and the design of the level sensors in the reservoirs. The latter being piezoelectric acoustic drivers (sonar type transducers) submerged in the liquid which detect the change in the surface height in the reservoirs.

California↗
USGS1988

Geophysical logs and hydrologic data for eight wells in the Coyote Spring Valley area, Clark and Lincoln counties, Nevada

Geophysical logs, drilling operations, pump-test data, and water quality determinations are presented for eight wells in the Coyote Spring Valley area of southeastern Nevada. The wells are in an area where thick units of Paleozoic carbonate rock are overlain by Tertiary semiconsolidated basin-fill deposits and Quaternary alluvial deposits. Data collected by the U.S. Geological Survey were augmented with data from previous investigations; however, complete sets of logs and other data are not available for all eight wells. Geophysical data presented included natural-gamma, neutron, gamma-gamma density, caliper, temperature, acoustic, single-point resistance, long- and short-natural resistivity, and spontaneous-potential logs. Drilling penetration rates, lithologic columns, and well construction are also summarized and presented. Measurements of drawdown and recovery during and after constant-discharge pumping periods are also included. Also presented are results of chemical and physical analyses for major-ion chemistry, trace constituents, stable and radioactive isotopes, temperature, pH, specific conductance, and dissolved oxygen. (USGS)

Open-File Report↗
USGS1992

Well-construction, water-level, geophysical, and water-quality data for ground-water monitoring wells for Arnold Air Force Base, Tennessee

Sixty-five wells were installed at 39 sites in the Arnold Air Force Base area in Coffee and Franklin Counties, Tennessee. The wells were installed to provide information on subsurface lithology, aquifer characteristics, ground-water levels, and ground-water quality. Well depths ranged from 11 to 384 feet. Water-quality samples were collected from 60 wells and analyzed for common inorganic ions, trace metals, and volatile organic compounds. The median dissolved-solids concentrations were 60 milligrams per liter in the shallow aquifer, 48 million gallons per liter in the Manchester aquifer, 1,235 milligrams per liter in the Fort Payne aquifer, and 1,712 milligrams per liter in the upper Central Basin aquifer. Caliper, temperature, natural gamma, electric, neutron porosity, gamma-gamma density, and acoustic velocity borehole-geophysical logs were obtained for the six deep wells completed below the Chattanooga Shale. Petrographic and modal analysis were performed on rock samples from each deep well. These six deep wells provide the first information in the study area on hydraulic head and water quality from below the Chattanooga Shale.

Tennessee↗
USGS1994

Review of literature on the testing of point-velocity current meters

The U.S. Geological Survey is in the process of evaluating point-velocity current meters. As part of this evaluation process, a review of the literature pertaining to the testing of point-velocity current meters was conducted. A listing of current-meter testing found in the literature was compiled and is grouped according to the type of meter tested and the type of test conducted. Meter types included in the review were vertical- and horizontal-axis mechanical current meters and electromagnetic acoustic electronic current meters. Laser current meters are not included in the review because there are no practical laser meter designs for field velocity measurements. The results of the literature review indicated that there has not been a comprehensive testing of the commonly available current meters since the 1920's.

Open-File Report↗
USGS1995

Multichannel seismic-reflection profiling on the R/V Maurice Ewing during the Los Angeles Region Seismic Experiment (LARSE), California

This report describes the acquisition of deep-crustal multichannel seismic-reflection data in the Inner California Borderland aboard the R/V Maurice Ewing, conducted in October 1994 as part of the Los Angeles Regional Seismic Experiment (LARSE). LARSE is a cooperative study of the crustal structure of southern California involving earth scientists from the U.S. Geological Survey, Caltech, the University of Southern California, the University of California Los Angeles, and the Southern California Earthquake Center (SCEC). During LARSE, the R/V Ewing's 20- element air gun array, totaling 137.7 liters (8470 cu. in.), was used as the primary seismic source for wide-angle recording along three main onshore-offshore lines centered on the Los Angeles basin and the epicenters of the 1933 Long Beach and 1994 Northridge earthquakes. The LARSE onshore-offshore lines were each 200-250 km long, with the offshore portions being between 90 and 150 km long. The nearly 24,000 air gun signals generated by the Ewing were recorded by an array of 170 PASSCAL REFTEK recorders deployed at 2 km intervals along all three of the onshore lines and 9 ocean bottom seismometers (OBSs) deployed along two of the lines. Separate passes over the OBS-deployment lines were performed with a long air gun repetition rate (60 and 90 seconds) to minimize acoustic-wave interference from previous shots in the OBS data. The Ewing's 4.2-km, 160-channel, digital streamer was also used to record approximately 1250 km of 40-fold multichannel seismic-reflection data. To enhance the fold of the wide-angle data recorded onshore, mitigating against cultural and wind noise in the Los Angeles basin, the entire ship track was repeated at least once resulting in fewer than about 660 km of unique trackline coverage in the Inner Borderland. Portions of the seismic-reflection lines were repeated up to 6 times. A variety of other geophysical data were also continuously recorded, including 3.5 kHz bathymetry, multi-beam swath Hydrosweep bathymetry, magnetics, and gravity data. In this report, we describe the equipment and procedures used to acquire multichannel seismic-reflection and other geophysical data aboard the Ewing, provide a detailed cruise narrative, discuss the reduction of the data, and present near-trace constant offset seismic sections of the acquired profiles.

California↗
USGS1995

Structure of the basins and ranges, Southwest New Mexico, an interpretation of seismic velocity sections

This report presents a geologic appraisal of seismic velocity sections that profile a total of 790 km in southwest New Mexico west of Las Cruces and south of Lordsburg and Deming. The present work outlines the contribution of these velocity sections to estimating areas favorable for mineral resource occurrences. Seismic refraction surveys are carried out with the initial goal of estimating the subsurface distribution of acoustic compressional velocity (Vp), which may ultimately be interpreted to provide information on lithology, geologic structure, and the occurrence of natural resources. The seismic sections presented here show velocity detail having dimensions of 100's to 1000's of meters to a depth of about 2.5 km, and across a net of traverses that profile most basins well as several ranges in the study area. Figure 1 shows the location of the seismic refraction lines. The lines are designated 1, 2, 3, 4, 5, and 7; there is no line 6. The survey covers a broad swath of the southwest Basin and Range Province extending from the Arizona border eastward to the Rio Grande River, and from the Mexican border to about lat. 32° 30' N. Lines 1, 3, and 7 traverse the axis of basins in roughly northsouth directions; the remaining lines 2, 4, and 5 trend east-west and cross various ranges and basins. Seismic data that have been collected in this region include deep-crustal refraction traverses by university scientists and commercial seismic reflection profiles acquired for petroleum exploration. Results of deep-crustal refraction studies are reviewed to provide a regional setting for the higher resolution refraction data. Results from seismic reflection will not be discussed. Industry reflection data in the area are not generally available for non-proprietary use. The nearest reflection data publicly available are in the Socorro area, about 80 km north of the present study area (Brown and others, 1980). These data were acquired by the Consortium for Continental Reflection Profiling (COCORP), a public-supported research group, to investigate the possibility of magma beneath part of the Rio Grande valley. Up to 1978 there were about 36 deep borings in the region of southwest New Mexico (Thompson and others, 1978). This drilling resulted mainly from an evaluation of petroleum potential of the Pedrogosa basin which is an extensive area of Paleozoic subsidence in Arizona, New Mexico, and Mexico that accumulated about three kilometers of Paleozoic sedimentary rock (Zeller, 1965; Thompson and others, 1978). Of these drill holes, 25 are close enough to the present seismic sections to provide correlations of velocity to lithology, and to provide an estimate of the errors associated with depth-to-interface interpretations. This information is summarized prior to considering the implications of the seismic sections in detail. The major portion of the report centers around two plates: Plate I shows seismic lines and selected drill hole locations superimposed on gravity contours, and Plate II shows velocitysections with drill hole summaries. These plates provide the foundation for developing inferences on buried lithologic, structural, and mineral resources for the region.

New Mexico↗
USGS1995

K1-95-HW: Cruise report 1995 - Preliminary results, phase III: Sediment chemistry and biological sampling survey

Mamala Bay, off the south shore of the island of Oahu, has been used as a repository of dredged material primarily from Pearl and Honolulu Harbors for over a century. The U.S. Geological Survey, U.S. Army Corps of Engineers, and the U.S. Environmental Protection Agency are conducting an integrated study on the distribution and character of dredged materials as well as the effects of dredged material on the marine environment. A three phase study is providing information to evaluate the effects on seafloor substrate and the benthic fauna. The studies include geophysical profiling and imaging, bottom photography, sampling, chemical and physical analyses of sediment, and evaluations of the benthic population, population density, and adverse impacts to the benthic fauna. Phase 1, conducted in 1993, inventoried the seafloor via remote sensing. Sidescan sonar and subbottom profilers characterized the seafloor in and around the disposal sites, and the resulting products reveal the character and extent of the dredged material. These data were used to plan Phase 2 in 1994, a sampling program that employed subbottom profilers, video and still photography, and seafloor sampling to ground truth the sonar mosaic and identify the seafloor substrates responsible for the various acoustic signatures on the sonar images and subbottom profiles. Box coring provided the samples necessary to distinguish dredged material from native sediment, and for the chemical analyses used to determine contaminant concentrations. Phase 3 studies conducted in June of 1995 consisted of box core sampling for chemical and biological analyses. Specific studies include: infaunal taxonomy and population density, bioassay/bioaccumulation, sediment chemistry, and post-disposal resuspension and transport. The 1995 survey, conducted June 14 through 17, resulted in the collection of 39 box cores from 20 different stations. Multiple box cores were composited at 7 different locations occupied in 1994, to provide the material required for the 7 bioassay and bioaccumulation analyses currently underway (Figure 1). Seventeen of the 20 stations occupied provided the biological samples for the benthic infaunal identification and population density study conducted by Dr. Julie Brock of the University of Hawaii, and the sediment chemistry analyses conducted (and completed) by Quanterra Environmental Laboratories (Figure 1). Seven of the 20 stations occupied in 1995 were occupied in 1994, and provide the data for direct comparison of sediment chemistry at the same sites from two consecutive years. The sum total of the data collected from all three phases of the monitoring program will provide the U.S. Army Corps of Engineers and the U.S. Environmental Protection Agency with the information required to make informed decisions as to the management of the South Oahu disposal site in Mamala Bay.

Hawai'i↗
USGS1997

Comparison of two methods for estimating discharge and nutrient loads from tidally affected reaches of the Myakka and Peace Rivers, west-central Florida

The Myakka and Peace River Basins constitute more than 60 percent of the total inflow area and contribute more than half the total tributary inflow to the Charlotte Harbor estuarine system. Water discharge and nutrient enrichment have been identified as significant concerns in the estuary, and consequently, it is important to accurately estimate the magnitude of discharges and nutrient loads transported by inflows from both rivers. Two methods for estimating discharge and nutrient loads from tidally affected reaches of the Myakka and Peace Rivers were compared. The first method was a tidal-estimation method, in which discharge and nutrient loads were estimated based on stage, water-velocity, discharge, and water-quality data collected near the mouths of the rivers. The second method was a traditional basin-ratio method in which discharge and nutrient loads at the mouths were estimated from discharge and loads measured at upstream stations. Stage and water-velocity data were collected near the river mouths by submersible instruments, deployed in situ, and discharge measurements were made with an acoustic Doppler current profiler. The data collected near the mouths of the Myakka River and Peace River were filtered, using a low-pass filter, to remove daily mixed-tide effects with periods less than about 2 days. The filtered data from near the river mouths were used to calculate daily mean discharge and nutrient loads. These tidal-estimation-method values were then compared to the basin-ratio-method values. Four separate 30-day periods of differing streamflow conditions were chosen for monitoring and comparison. Discharge and nutrient load estimates computed from the tidal-estimation and basin-ratio methods were most similar during high-flow periods. However, during high flow, the values computed from the tidal-estimation method for the Myakka and Peace Rivers were consistently lower than the values computed from the basin-ratio method. There were substantial differences between discharges and nutrient loads computed from the tidal-estimation and basin-ratio methods during low-flow periods. Furthermore, the differences between the methods were not consistent. Discharges and nutrient loads computed from the tidal-estimation method for the Myakka River were higher than those computed from the basin-ratio method, whereas discharges and nutrients loads computed by the tidal-estimation method for the Peace River were not only lower than those computed from the basin-ratio method, but they actually reflected a negative, or upstream, net movement. Short-term tidal measurement results should be used with caution, because antecedent conditions can influence the discharge and nutrient loads. Continuous tidal data collected over a 1- or 2-year period would be necessary to more accurately estimate the tidally affected discharge and nutrient loads for the Myakka and Peace River Basins.

Florida↗
USGS1997

Maps showing the surficial geology of the Culebra shelf, Puerto Rico

This study presents the surficial and shallow subbottom geology of the insular shelf around Culebra, Puerto Rico. In view of the need for sand and gravel for construction purposes in the area, we inferred the thickness of unlithified, surficial sediment deposits from high-resolution acoustic-reflection profiles and described seafloor sediment samples collected with a Shipek grab.

Open-File Report↗
USGS1997

Stratigraphy and geophysical logs from a corehole drilled to bedrock at Robins Point, J-Field, Edgewood area, Aberdeen Proving Ground, Maryland

A continuous core was recovered from a 961-foot- deep stratigraphic corehole at Robins Point, located at the southeastern tip of the Gunpowder Neck Peninsula, Harford County, Maryland. A 2-inch- diameter ground-water-quality observation well was installed with the screen set at a depth of 392 to 402 feet (ft). Geophysical logs obtained from thecorehole include: natural gamma, multipoint normal resistivity (16-inch and 64-inch), 4-ft-guard focused resistivity, acoustic (sonic) velocity, and caliper. Pollen analysis of 34 samples provided relativestratigraphic ages. Lithologies encountered in ascending order (surface elevation 4 ft above mean sea level), include: 72.4 ft of weatheredmetamorphic rock and saprolie, 711.4 ft of lower and upper Cretaceous fluvio-deltaic deposits, and 145.9 ft of Pleistocene and 31.3 ft of Holocene(?) fluvial and estuarine deposits. Aquifers and confining units identified include, in descending order: 41.8 ft of surficial aquifer, 90.9 ft of upper paleochannel confining unit, 28.8 ft of paleochannel confined aquifer, 15.7 ft of lower paleochannel confining unit, 123.7 ft of Upper Patapsco aquifer, 44.6 ft of Upper Patapsco confining unit, 92.8 ft of Middle Patapsco aquifer, 57.3 ft of Lower Patapsco confining unit, 151.7 ft of Lower Patapsco aquifer, 115.4 ft of Potomac confining unit, 126.4 ft of Patuxent aquifer, an aquifer of 23.4 ft of saprolite, and 48.7 ft of weathered-rock/saprolite confining unit.

Open-File Report↗
USGS1998

Measured flow and tracer-dye data showing the anthropogenic effects on the hydrodynamics of south Sacramento-San Joaquin Delta, California, spring 1996 and 1997

Tidal flows were measured using acoustic Doppler current profilers and ultrasonic velocity meters during spring 1996 and 1997 in south Sacramento-San Joaquin Delta, California, when (1) a temporary barrier was installed at the head of Old River to prevent the entrance of migrating San Joaquin River salmon smolts, (2) the rate of water export from the south Delta was reduced for an extended period of time, and (3) a 30-day pulse flow was created on the San Joaquin River to move salmon smolts north away from the export facilities during spring 1997. Tracer-dye measurements also were made under these three conditions.

Open-File Report↗
USGS1999

Turbidite pathways in Cascadia Basin and Tufts abyssal plain, Part A, Astoria Channel, Blanco Valley, and Gorda Basin

This open-file report was prepared in support of the USGS Earthquake Hazards of Cascadia Project. The primary objective of this phase of the project is to determine recurrence intervals of turbidites in Cascadia basin-floor channel systems and evaluate implications of this event record for the paleoseismic history of the Cascadia subduction zone. The purpose of this study is to determine whether the canyon/channel systems themselves are blocked or deformed in such a way that the downstream turbidite stratigraphy might be biased. To accomplish this investigation approximately 7500 kilometers of pre-existing 3.5 KHz seismic data were evaluated to determine the direction and extent of the Astoria Channel/pathway system, which originates at the base of the Astoria Fan. Additionally, distribution and thickness of turbidite sediment sequences were determined along each identified pathway. Bathymetery and distance were used to determine gradients along the main pathway axis and for each of the secondary pathways that feed into it. Channel pathways were identified on the basis of channel phyisiography, where visible at the seafloor, subbottom channel configuration, and acoustic packets of sediments that might represent turbidite deposits. A principal result of this study is that the Astoria Channel/pathway extends continuously from the base of the Astoria Fan southward along the base of the continental slope through the Blanco Valley, then heads southwestward through the Gorda Basin and into the region of the Escanaba Trough. Additionally it was determined that the Astoria Channel is filled and basically buried for it's full length south of 44 degrees latitude. The 44 North Slump, as defined by Goldfinger (1999, see Map 3 ref.), may have been instrumental in blocking the pathway and thus contributed to the filling of the channel/pathway. Sheets 1 and 2 show the Astoria and secondary turbidite pathways highlighted in blue. Ship survey tracklines are shown for the area studied; they are time and date coded, and color keyed to each ship ID data base listed at the bottom of each sheet. The first letter in the cruise ID is an abbreviation letter for the ship name, the following numbers represent the consecutive cruise number of that year, followed by the year number. The letters at the end of the ID represent the survey area, ie. NC- northern California, NP- north Pacific. Locations of selected sample seismic sections illustrated on sheets 3-5 also are shown. Scales for each of the sheets are the same as for sheets 3-5, which allows for overlaying of track data onto the interpretations shown on Maps A-C. Sheets 3 (MAP A), 4 (MAP B), and 5 (MAP C) show channel pathway location, bathymetric depth based on the USGS COW data base (Ca/Or/Wa), pathway morphology, and thickness of turbidite sediment fill at various locations. The interpreted turbidite sediments are color highlighted on the selected seismic sections to differentiate them from the typical deep sea sediments below and to the side of the turbidite pathways. Thickness of sediment fill, in meters, is shown along major pathways in white circular highlights. The data and interpretations rest on a background of USGS GLORIA side scan sonar imagery (1984) to illustrate the relationship of pathway position to sub sea features. Channel distance points are plotted along channel centerlines at 20,000 m intervals. These points begin at the start of each interpreted channel pathway. A bathymetric depth was assigned to each distance point. These data points were then used to construct channel gradient curves for the Astoria, Eel, Bear Valley, and Mendocino channel pathways. These gradients are plotted on sheet 6 of this report and illustrate the similarities and differences between each of the pathways. Sheet 7 shows various views of the Mendocino/Mattole Canyon heads as an example of useful derivative information of the Seabeam bathymetric data. These views illustrate that the Mendocino pathway probably was directed from it's canyon mouth, to the northwest at an earlier time, but was diverted to the west along the base of the Mendocino Ridge by a major fault event in the recent past. Offset of the southwest channel wall is readily evident in views B and D. This apparent disruption complicates the turbidite history of the Mendocino pathway.

California;Oregon↗
USGS2000

Surveys of water velocities in the vicinity of the discharge-release gates of Salamonie Lake Dam, northeastern Indiana, spring and winter 1998

Two water-velocity surveys in the vicinity of the discharge-release gates were performed at the Salamonie Lake flood-control reservoir in northeastern Indiana during periods of high-discharge release. One survey was done in the spring when the reservoir pool was at high elevation; the other survey was in the winter when the reservoir pool was low. The maximum measured velocity was 2.4 feet per second for the spring survey and 1.9 feet per second for the winter survey. The maximum measured velocities occurred in the immediate vicinity of the spillway tower containing the discharge-release gates. Velocity-field magnitudes diminished rapidly with distance from the tower. Beyond an estimated 40 feet from the tower, velocity magnitudes were below 0.5 feet per second. For the spring and winter surveys, data were collected along four transects that were parallel to the face of the spillway tower. The transects were at the following approximate distances from the spillway tower: 900, 600, and 300 feet and as close to the tower as practical. For the spring and winter surveys, velocity-contour plots were produced for the transects closest to the tower. Plots were not made for the transects at 900-, 600-, and 300-foot intervals because velocities were negligible at these distances. An acoustic Doppler current profiler (ADCP) mounted on a boat was used to collect velocity and depth data and to compute positions of the velocity and depth data relative to the boat track. A global positioning system (GPS) was used to collect earth-referenced position data, and a GPS base station receiver was used to improve the accuracy of the earth-referenced position data. The earth-referenced position data were used to transform the ADCP-computed positions (which were relative to boat tracks) to positions referenced to a point on the spillway tower.

Indiana↗
USGS1999

Analysis of geophysical logs, at North Penn Area 6 Superfund Site, Lansdale, Montgomery County, Pennsylvania

The U.S. Geological Survey (USGS), as part of technical assistance to the U.S. Environmental Protection Agency (USEPA), collected borehole geophysical log data in 34 industrial, commercial, and public supply wells and 28 monitor wells at the North Penn Area 6 Superfund Site, in Lansdale, Pa., from August 22, 1995, through August 29, 1997. The wells range in depth from 50 to 1,027 feet below land surface and are drilled in Triassic-age shales and siltstones of the Brunswick Group and Lockatong Formation. The geophysical log data were collected to help describe the hydrogeologic framework in the area and to provide guidance in the reconstruction of the 28 monitor wells drilled during summer 1997. At the time of logging, all wells had open-hole construction. The geophysical logs, caliper, fluid-resistivity, and fluid-temperature, and borehole video logs were used to determine the vertical distribution of water-bearing fractures. Heatpulse-flowmeter measurements were used to determine vertical borehole flow under pumping and nonpumping conditions. The most productive fractures generally could be determined from heatpulse-flowmeter measurements under pumping conditions. Vertical borehole flow was measured under nonpumping conditions in most wells that had more than one water-bearing fracture. Upward flow was measured in 35 wells and probably is a result of natural head differences between fractures in the local ground-water-flow system. Downward flow was measured in 11 wells and commonly indicated differences in hydraulic heads of the fractures caused by nearby pumping. Both upward and downward flow was measured in three wells. No flow was detected in eight wells. Natural-gamma-ray logs were used to estimate the attitude of bedding. Thin shale marker beds, shown as spikes of elevated radioactivity in the natural-gamma logs of some wells throughout the area, enable the determination of bedding-plane orientation from three-point correlations. Generally, the marker beds in and near Lansdale strike about N. 48°-60° E. and dip about 11° NW. Acoustic televiewer logs run in selected boreholes indicate that the attitude of many water-bearing fractures commonly is similar to that of bedding.

Pennsylvania↗
USGS2008

Seismicity and infrasound associated with explosions at Mount St. Helens, 2004-2005

Six explosions occurred during 2004-5 in association with renewed eruptive activity at Mount St. Helens, Washington. Of four explosions in October 2004, none had precursory seismicity and two had explosion-related seismic tremor that marked the end of the explosion. However, seismicity levels dropped following each of the October explosions, providing the primary instrumental means for explosion detection during the initial vent-clearing phase. In contrast, explosions on January 16 and March 8, 2005, produced noticeable seismicity in the form of explosion-related tremor, infrasonic signals, and, in the case of the March 8 explosion, an increase in event size ~2 hours before the explosion. In both 2005 cases seismic tremor appeared before any infrasonic signals and was best recorded on stations located within the crater. These explosions demonstrated that reliable explosion detection at volcanoes like Mount St. Helens requires seismic stations within 1-2 km of the vent and stations with multiple acoustic sensors.

Washington↗
USGS2008

Views of the Sea Floor in Northern Monterey Bay, California

A sonar survey that produced unprecedented high-resolution images of the sea floor in northern Monterey Bay was conducted in 2005 and 2006. The survey, performed over 14 days by the U.S. Geological Survey (USGS), consisted of 172 tracklines and over 300 million soundings and covered an area of 12.2 km2 (4.7 mi2). The goals of this survey were to collect high-resolution bathymetry (depth to the sea floor) and acoustic backscatter data (amount of sound energy bounced back from the sea floor, which provides information on sea-floor hardness and texture) from the inner continental shelf. These data will provide a baseline for future change analyses, geologic mapping, sediment- and contaminant-transport studies, benthic-habitat delineation, and numerical modeling efforts. The survey shows that the inner shelf in this area is extremely varied in nature, encompassing flat sandy areas, faults, boulder fields, and complex bedrock ridges that support rich marine ecosystems. Furthermore, many of these complex bedrock ridges form the ?reefs? that result in a number of California?s classic surf breaks.

Scientific Investigations Map↗
USGS2011

Bathymetric and sediment facies maps for China Bend and Marcus Flats, Franklin D. Roosevelt Lake, Washington, 2008 and 2009

The U.S. Geological Survey (USGS) created bathymetric and sediment facies maps for portions of two reaches of Lake Roosevelt in support of an interdisciplinary study of white sturgeon (Acipenser transmontanus) and their habitat areas within Franklin D. Roosevelt Lake, Washington. In October 2008, scientists from the USGS used a boat-mounted multibeam echo sounder (MBES) to describe bathymetric data to characterize surface relief at China Bend and Marcus Flats, between Northport and Kettle Falls, Washington. In March 2009, an underwater video camera was used to view and record sediment facies that were then characterized by sediment type, grain size, and areas of sand deposition. Smelter slag has been identified as having the characteristics of sand-sized black particles; the two non-invasive surveys attempted to identify areas containing black-colored particulate matter that may be elements and minerals, organic material, or slag. The white sturgeon population in Lake Roosevelt is threatened by the failure of natural recruitment, resulting in a native population that consists primarily of aging fish and that is gradually declining as fish die and are not replaced by nonhatchery reared juvenile fish. These fish spawn and rear in the riverine and upper reservoir reaches where smelter slag is present in the sediment of the river lake bed. Effects of slag on the white sturgeon population in Lake Roosevelt are largely unknown. Two recent studies demonstrated that copper and other metals are mobilized from slag in aqueous environments with concentrations of copper and zinc in bed sediments reaching levels of 10,000 and 30,000 mg/kg due to the presence of smelter slag. Copper was found to be highly toxic to 30-day-old white sturgeon with 96-h LC50 concentrations ranging from 3 to 5 (u or mu)g copper per liter. Older juvenile and adult sturgeons commonly ingest substantial amounts of sediment while foraging. Future study efforts in Lake Roosevelt should include sampling of bottom material to confirm the presence or absence of slag material indicated on the map. In addition, follow-up acoustic work to determine stream velocities at varying discharges, in conjunction with sediment mapping, would be helpful to more accurately identify areas of scour and areas of sediment deposition where slag deposits may accumulate within the Marcus Flats and China Bend reaches. MBES mapping could also be used to determine changes in bed elevation and sedimentation in the study reaches and could help evaluate annual deposition and provide estimates on fine-sediment thickness.

Washington↗