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At least 793 records · Page 44Linked to original sources
USGS1922

Guidebook of the western United States: Part E - The Denver & Rio Grande Western route

The United States of America comprise an area so vast in extent and so diverse in natural features as well as in characters due to human agency that the American citizen who knows thoroughly his own country must have traveled widely and observed wisely. To 'know America first' is a patriotic obligation, but to meet this obligation the railroad traveler needs to have his eyes directed toward the more important or essential things within his field of vision and then to have much that he sees explained by what is unseen in the swift passage of the train. Indeed, many things that attract his attention are inexplicable except as the story of the past is available to enable him to interpret the present. Herein lie the value and the charm of history, whether human or geologic. The present stimulus given to travel in the home country will encourage many thousands of Americans to study geography at first hand. To make this study most profitable the traveler needs a handbook that will answer the questions that come to his mind so readily along the way. Furthermore, the aim of such a guide should be to stimulate the eye in the selection of the essentials in the scene that so rapidly unfolds itself in the crossing of the continent. In recognition of the opportunity to render service of this kind to an unusually large number of American citizens, as well as to visitors from other countries, the United States Geological Survey has published a series of guidebooks covering four of the older railroad routes west of the Mississippi. The present volume is an addition to this series and covers one of the finest scenic routes of the continent. These books are educational in purpose, but the method adopted is to entertain the traveler by making more interesting what he sees from the car window. The plan of the series is to present authoritative information that may enable the reader to realize adequately the scenic and material resources of the region he is traversing, to comprehend correctly the basis of its development, and above all to appreciate keenly the real value of the country he looks out upon, not as so many square miles of territory represented on the map in a railroad folder by meaningless spaces, but rather as land - real estate, if you please - varying widely in present appearance because differing largely in its history, and characterized by even greater variation in values because possessing diversified natural resources. One region may be such as to afford a livelihood for only a pastoral people; another may present opportunity for intensive agriculture; still another may contain hidden stores of mineral wealth that may attract large industrial development; and, taken together, these varied resources afford, the promise of long-continued prosperity for this or that State. Items of interest in civic development or references to significant epochs in the record of discovery and settlement may be interspersed. with explanations of mountain and valley or statements of geologic history. In a broad way the story of the West is a unit, and every chapter should be told in order to meet fully the needs of the tourist who aims to understand all that he sees. To such a traveler-reader this series of guidebooks is addressed. To this interpretation of our own country the United States Geological Survey brings the accumulated data of decades of pioneering investigation, and the present contribution is only one type of return to the public which has supported this scientific work under the Federal Government - a by-product of research. In the preparation of the description of the country traversed by the Denver & Rio Grande Western Route the geographic and geologic information already published as well as unpublished material in the possession of the Geological Survey has been utilized, but to supplement this material Mr. Campbell made a field examination of the entire route in 1915-1916. Information has been furnished by others,

Bulletin↗
USGS1994

Revised correlation chart of coal beds, coal zones, and key stratigraphic units in the Pennsylvanian rocks of eastern Kentucky

This report revises Miscellaneous Field Studies Map MF-1188 (Rice and Smith, 1980). Major revisions to the original correlation chart include formal naming of key marine units in Kentucky and replacement of informally named marine units incorrectly projected into Kentucky from adjacent states. Also included in the report is the proper correlation of some regionally recognized coal bed names that have been incorrectly projected into Kentucky, particularly from Ohio and West Virginia. Besides these additions and corrections, minor changes have been made to the correlation chart, all of which are discussed below in detail. The Pennsylvania rocks of the eastern Kentucky coal field underlie an area of about 27,000 square kilometers (see index map). Largely because of the size and stratigra[hic complexity of the area, Huddle and others (1963, p. 31) divided the coal field into six coal-reserve districts. District boundaries utilize state and county line as well as geologic features, drainage areas, and coal producing areas. Their division is followed herein because, in general, each of the districts has a characteristic stratigraphic nomenclature, particularly with regard to coal bed names. The six districts are the Princess, Licking River, Big Sandy, Hazard, Southwestern, and Upper Cumberland River district is divided into the Middlesboro and Harlan subdistricts. The correlation chart lists most of the stratigraphic units of Pennsylvanian age used in eastern Kentucky, and is concerned principally with coal bed names used in publications since about 1950, especially all of the names of coal beds for which resources and reserves have been calculated. Coal constitutes only a small percentage of the total Pennsylvanian-rock sequence, but is present in as many as 26 major coal zones that have been prospected and mined extensively in all parts of the coal field since the early 1900's. Coal names listed in this chart represent coal beds that have been mined commercially or used locally by residents of the area. Not every coal bed listed under a district in the chart is found in all parts of that district, nor has every coal bed been given a name. For the sake of saving space, coal beds commonly identified as a "rider" coal bed (commonly a minor coal or split above the main bed) or as a "marker" coal bed (a minor coal below the main bed) are not included in the chart because they do not contribute to the overall stratigraphic framework of the coal field. Most of the stratigraphic units listed in the correlation chart are defined and described in detail in almost 200 geologic reports of the Geologic Quadrangle (GQ) Map Series of the U.S. Geological Survey (USGS). These maps were published as a result of the cooperative geological mapping program of the USGS and the Kentucky Geological Survey; which was begun in 1960 and was completed in 1978. The GQ maps, at a scale of 1:24,000, describe the lithology and local stratigraphy and identify many coal beds by noth local and regional names. Other sources of stratigraphic information and coal bed names used in the construction of the chart include USGS bulletins dealing with the coal resources of single 7.5-minute quadrangles (Englund, 1955; Adkinson, 1957; Welch, 1958; Bergin, 1962). The coal resources of eastern Kentucky as a whole have been described by Huddle and others (1963) and detailed reports on the stratigraphy and coal resources of significant areas in eastern Kentucky have been made by Huddle and Englund (1966) and Englund (1968). An additional source of coal bed names is the SEAMS database, which is jointly sponsored by the University of Kentucky Center for Applied Energy Research, the Kentucky Geological Survey, and the Kentucky Department of Mines and Minerals. The SEAMS database identifies the stratigraphic position and location of all coal beds in the eastern and the western Kentucky coal fields as well as those of bordering areas in adjacent states. The databases includes references to all coal-bed names used in Kentucky, especially those shown on coal company mine maps. Local names of coal beds in the database file that are not generally used in publications are listed in table 1 together with their regional equivalents.

Kentucky↗
USGS1955

Geologic investigations of radioactive deposits, semiannual progress report for June 1 to November 30, 1955

This report is a statement of progress during the six-months period from June 1 to November 30, 1955 on investigations of radioactive materials in the United States and Alaska, undertaken by the U.S. Geological Survey under the sponsorship of the U.S. Atomic Energy Commission. During the period the Geological Survey's program has been directed to an increasing extent toward the understanding of geologic conditions favorable for the concentration of uranium, rather than the search for minable deposits as such. This shift in emphasis is reflected in the decreased amount of exploration drilling during the period, and the accompanying increase in geologic programs of a long-range nature. The program is now directed toward a comprehensive understanding of the many factors involved in uranium geology, and the publication of reports that will make available information on all phases of the uranium program. Many investigations have progressed to the point where final reports are in preparation for future publication with the permission of the Atomic Energy Commission; for other investigations of a continuing nature it will be several years before final reports can be prepared. Formal publications (as distinguished from administrative Trace Elements Reports) published during the period include 10 Geological Survey Bulletins or Bulletin Chapters; 116 Geological Survey maps; 15 reports published in scientific journals; seven Trace Elements Reports sent to the Technical Information Service of the Atomic Energy Commission for distribution and sale to the public; and four Trace Elements reports placed on open file. In addition, a large number •of papers by geologists in the program were presented before scientific societies, and the 61 papers prepared for the United Nations International Conference .on the Peaceful Uses of Atomic Energy during the preceding report period were published by the United Nations.

Trace Elements Investigations↗
USGS1905

Twenty-Sixth Annual Report of the Director of the United States Geological Survey, 1904-1905

Introduction Remarks on the work of the year Branches of work The United States Geological Survey was created in 1879 for the purpose—as its name implies—of examining and reporting on the geologic structure and mineral resources and products of the national domain. To the adequate description of geologic formations and structure cartography is essential, and Congress early recognized this fact by making appropriations for the preparation of a geologic map of the United States. The topographic base map, in order to show with sufficient precision the relations of the geologic formations and the intricacies of the structure, must have a rather large scale and present considerable detail. No such map of this country existed in 1879, and its preparation was immediately begun. The waters of the country are of vast importance, and in a broad sense may be regarded as one of its greatest mineral resources. Hence, in the evolution of the work of the Survey, and especially in view of the great importance of the subject to the irrigation interests, Congress early began making appropriations for ascertaining the amount and quality of the surface and underground waters and when, in 1902, the service for the reclamation of arid lands was organized, that work naturally was placed in the hands of the Secretary of the Interior and by him intrusted to the Director of the Survey. The three great branches of work carried on by the Geological Survey are, therefore, the geologic, the topographic, and the hydrographic, and with these, more especially the latter, is conjoined the Reclamation Service ; publication and administration constitute necessary auxiliary branches. Along these great lines the work of the Survey has progressed without essential variation for many years. The changes made have been due to normal expansion rather than to radical departure in object or plan. State cooperation During the last fiscal year, State cooperation, as explained in previous reports, continued. Arrangements for cooperation in geologic work were made with five States, the total amount contributed by them being about \$8,000, and arrangements for cooperative topographic surveys were made with eleven States, the amount available for such surveys being thus increased by more than \$100,000. Reclamation service The work of the Reclamation Service during the last fiscal year was advanced as rapidly as was thought consistent with thoroughness and accuracy. Actual construction is now in progress on eight projects, as follows : Salt River, Arizona; Truckee-Carson, Nevada; Hondo, New Mexico ; Uncompahgre Valley, Colorado; Minidoka, Idaho; Belle Fourche, South Dakota ; North Platte, Wyoming and Nebraska ; and Shoshone, Wyoming. Proposals were received for work on the Laguna dam, Yuma project, California and Arizona; Huntley project, Montana, and the Fort Buford project, North Dakota and Montana. In several other States operations are at a point where advertisements for bids only await the removal of certain legal obstacles, the settlement of international difficulties, or the termination of delays on the part of local organizations or individuals. The organization of the body of men constituting the personnel of the Reclamation Service, whose field of operations covers so large a territory, though necessarily difficult, has been satisfactorily accomplished, and precedents have been established along approved lines. The general allotment of funds has been made with a view to the greatest benefit to the greatest number, and from the broad standpoint of the welfare of the country as a whole. One of the important features in the evolution of the irrigation work is the development of power, which the numerous dams and, drops in canals make possible. Plans were made to transmit the power being developed in many sections of the arid regions, by means of electricity, to points more or less distant, there to be used for raising underground waters, pumping waters lying above the line of gravity canals, or for various other purposes, and attention was also given to the character of the soils and of the water to be used upon them, the materials used in the construction of the works, and numerous other details incident to reclamation by irrigation. Coal-testing plant Under two special appropriations of \$30,000 each, carried by the urgent deficiency bill approved February 18, 1904, and the general deficiency bill approved April 27, 1904, the Director of the Geological Survey was authorized to construct and operate at the Louisiana Purchase Exposition a plant for testing the coals and lignites of the United States, in order to determine their fuel values and the most economic method of their utilization for different purposes, it being provided that all testing machinery and all coals and lignites to be tested 'should be contributed free of charge to the Government. For carrying out the provisions of these acts the Director appointed a committee, consisting of Edward W. Parker, Joseph A. Holmes, and Marius R. Campbell, to direct the construction and operation of the plant. This committee received the heartiest cooperation from the manufacturers of such equipment as was needed for the installation of the plant, from the railroad companies in freight concessions and transportation for the experts and their assistants, and from the coal operators in the furnishing of coal in carload lots for testing purposes. Although the utmost expedition was used in the construction of the plant, it was not until the first of September that the testing work actually began. Between the first of September and the close of the exposition 65 carload samples of coal for testing purposes were received, and the results of the investigation were published in a preliminary report issued as Geological Survey Bulletin No. 261. The coals tested were received from 17 States and Territories, and much valuable information regarding the best uses to which the different coals may be put was obtained. One of the most important facts developed during this investigation is the possibility of utilizing the vast lignite resources of the West in the manufacture of producer gas, it having been shown that a higher grade of this gas can be obtained from lignite than from ordinary bituminous and anthracite coal. The investigation also showed that the slack or fine coal produced at the dry, noncoking bituminous coal mines of the middle West, large quantities of which are now being wasted, can be profitably utilized by briquetting.

Annual Report↗
USGS2014

Estimating magnitude and frequency of floods using the PeakFQ 7.0 program

Flood-frequency analysis provides information about the magnitude and frequency of flood discharges based on records of annual maximum instantaneous peak discharges collected at streamgages. The information is essential for defining flood-hazard areas, for managing floodplains, and for designing bridges, culverts, dams, levees, and other flood-control structures. Bulletin 17B (B17B) of the Interagency Advisory Committee on Water Data (IACWD; 1982) codifies the standard methodology for conducting flood-frequency studies in the United States. B17B specifies that annual peak-flow data are to be fit to a log-Pearson Type III distribution. Specific methods are also prescribed for improving skew estimates using regional skew information, tests for high and low outliers, adjustments for low outliers and zero flows, and procedures for incorporating historical flood information. The authors of B17B identified various needs for methodological improvement and recommended additional study. In response to these needs, the Advisory Committee on Water Information (ACWI, successor to IACWD; http://acwi.gov/ , Subcommittee on Hydrology (SOH), Hydrologic Frequency Analysis Work Group (HFAWG), has recommended modest changes to B17B. These changes include adoption of a generalized method-of-moments estimator denoted the Expected Moments Algorithm (EMA) (Cohn and others, 1997) and a generalized version of the Grubbs-Beck test for low outliers (Cohn and others, 2013). The SOH requested that the USGS implement these changes in a user-friendly, publicly accessible program.

Fact Sheet↗
USGS1982

Design concepts for a Global Telemetered Seismograph Network

This study represents a first step in developing an integrated, real-time global seismic data acquisition system a Global Telemetered Seismograph Network (GTSN). The principal objective of the GTSN will be to acquire reliable, high-quality, real-time seismic data for rapid location and analysis of seismic events. A secondary, but important, objective of the GTSN is to augment the existing off-line seismic data base available for research. The deployment of the GTSN will involve a variety of interrelated activities development of the data acquisition and receiving equipment, establishment of satellite and terrestrial communication links, site selection and preparation, training of station personnel, equipment installation, and establishment of support facilities. It is a complex program and the development of a sound management plan will be essential. The purpose of this study is not to fix design goals or dictate avenues of approach but to develop working concepts that may be used as a framework for program planning. The international exchange of seismic data has been an important factor in the progress that has been made during the past two decades in our understanding of earthquakes and global tectonics. The seismic data base available for analysis and research is derived principally from the Global Seismograph Network (GSN), which is funded and managed by the U.S. Geological Survey (USGS). The GSN comprises some 120 seismograph stations located in more than 60 countries of the world. Established during the 1960 s with the installation of the World-Wide Standardized Seismograph Network (WWSSN) , the GSN has been augmented in recent years by the installation of more advanced data systems, such as the Seismic Research Observatories (SRO), the modified High-Gain LongPeriod (ASRO) seismographs, and the digital WWSSN (DWWSSN). The SRO, ASRO, and DWWSSN stations have the common, distinctive feature of digital data recording, so they are known collectively as the Global Digital Seismograph Network (GDSN). The fundamental objective in operating the GSN is to create and update a seismic data base that is accessible without restrictions to organizations and research scientists throughout the world. The USGS provides cooperating stations with instrumentation, training, and continuing support, including supplies and on-site maintenance. In return, the host organization operates the equipment and sends the recorded data to the USGS. Analog data (seismograms) are microfilmed and about four million copies are requested annually by researchers. Digital data, which are recorded on magnetic tape, are organized by the USGS Albuquerque Seismological Laboratory (ASL) into networkday tapes and copies of the day tapes are furnished to data users through national and regional data centers. After copying, original data are returned to the stations and used for local research. Most of the stations in the GSN also provide the USGS with seismic readings « phase arrival times and amplitudes scaled from the seismograms. These readings are transmitted on a daily or biweekly basis via commercial or diplomatic communication channels. They are used by the USGS National Earthquake Information Service (NEIS) to determine the location and magnitude of earthquakes occurring throughout the world. The results are published monthly in bulletins that are distributed to the participating stations and virtually all scientific organizations that are involved in seismological studies. It is a much-valued service that provides a current, updated catalog of seismic activity on a global scale. The NEIS also has the responsibility for rapid reporting of large and potentially destructive earthquakes. The NEIS issues news bulletins as soon as possible after the occurrence of magnitude 6.5 or greater earthquakes (magnitude 5 or greater in the conterminous United States). The news bulletins are sent to disaster relief, public safety, and other interested organizations. Tsunami warnings issued to countries bordering the Pacific Ocean are based initially on earthquake location and magnitude data. Rapid reporting of earthquakes requires real-time waveform data or readings. Currently, signals are being telemetered from more than thirty stations in the United States to the NEIS, which is located in Golden, Colorado. An extension of the telemetry network to other countries will provide the seismological community with a significantly improved means of monitoring earthquake activity in real time; it will lower the response time for determining the location and magnitude of potentially destructive or tsunamigenic earthquakes and it will provide more timely information that may be needed by governments to respond promptly.

Open-File Report↗
USGS2007

National water-quality assessment: Future directions of the U.S. Geological Survey

Throughout U.S. history, the Nation has made major investments in assessing natural resources, such as soils, minerals, and hydrocarbons. The maintenance and the improvement of water quality has been one of the major areas of public investment and government regulation. One of the contributions the U.S. Geological Survey proposes to make is to provide a strong, high quality National Water-Quality Assessment Program to underpin and unify the Nation's water-quality activities. Such an assessment program will satisfy a decisive share of the attainable, national scale, water quality information objectives.

Water Resources Bulletin↗
USGS2002

Comparison of shear-wave slowness profiles at 10 strong-motion sites from noninvasive SASW measurements and measurements made in boreholes

The spectral-analysis-of-surface-waves (SASW) method is a relatively new in situ method for determining shear-wave slownesses. All measurements are made on the ground surface, making it much less costly than methods that require boreholes. The SASW method uses a number of active sources (ranging from a commercial Vibroseis truck to a small handheld hammer for the study conducted here) and different receiver spacings to map a curve of apparent phase velocity versus frequency. With the simplifying assumption that the phase velocities correspond to fundamental mode surface waves, forward modeling yields an estimate of the sub-surface shear-wave slownesses. To establish the reliability of this indirect technique, we conducted a blind evaluation of the SASW method. SASW testing was performed at 10 strong-motion stations at which borehole seismic measurements were previously or subsequently made; if previously made, the borehole results were not used for the interpretation of the SASW data, and vice-versa. Comparisons of the shear-wave slownesses from the SASW and borehole measurements are generally very good. The differences in predicted ground-motion amplifications are less than about 15% for most frequencies. In addition, both methods gave the same NEHRP site classification for seven of the sites. For the other three sites the average velocities from the downhole measurements were only 5-13 m/sec larger than the velocity defining the class C/D boundary. This study demonstrates that in many situations the SASW method can provide subsurface information suitable for site response predictions.

California↗
USGS2008

Observation and prediction of dynamic ground strains, tilts, and torsions caused by the Mw 6.0 2004 Parkfield, California, earthquake and aftershocks, derived from UPSAR array observations

The 28 September 2004 Parkfield, California, earthquake (Mw 6.0) and four aftershocks (Mw 4.7-5.1) were recorded on 12 accelerograph stations of the U.S. Geological Survey Parkfield seismic array (UPSAR), an array of three-component accelerographs occupying an area of about 1 km2 located 8.8 km from the San Andreas fault. Peak horizontal acceleration and velocity at UPSAR during the mainshock were 0.45g and 27 cm/sec, respectively. We determined both time-varying and peak values of ground dilatations, shear strains, torsions, tilts, torsion rates, and tilt rates by applying a time-dependent geodetic analysis to the observed array displacement time series. Array-derived dilatations agree fairly well with point measurements made on high sample rate recordings of the Parkfield-area dilatometers (Johnston et al., 2006). Torsion Fourier amplitude spectra agree well with ground velocity spectra, as expected for propagating plane waves. A simple predictive relation, using the predicted peak velocity from the Boore-Atkinson ground-motion prediction relation (Boore and Atkinson, 2007) scaled by a phase velocity of 1 km/sec, predicts observed peak Parkfield and Chi-Chi rotations (Huang, 2003) well. However, rotation rates measured during Mw 5 Ito, Japan, events observed on a gyro sensor (Takeo, 1998) are factors of 5-60 greater than those predicted by our predictive relation. This discrepancy might be caused by a scale dependence in rotation, with rotations measured over a short baseline exceeding those measured over long baselines. An alternative hypothesis is that events having significant non-double-couple mechanisms, like the Ito events, radiate much stronger rotations than double-couple events. If this is true, then rotational observations might provide an important source of new information for monitoring seismicity in volcanic areas.

Bulletin of the Seismological Society of America↗
USGS2003

Uncertainty and inferred reserve estimates — The 1995 National Assessment

Inferred reserves are expected additions to proved reserves of oil and gas fields discovered as of a certain date. Inferred reserves accounted for 65 percent of the total oil and 34 percent of the total gas assessed in the U.S. Geological Survey's 1995 National Assessment of oil and gas in onshore and State offshore areas. The assessment predicted that over the 80-year period from 1992 through 2071, the sizes of pre-1992 discoveries in the lower 48 onshore and State offshore areas will increase by 48 billion barrels of oil (BBO) and 313 trillion cubic feet of wet gas (TCF). At that time, only point estimates were reported. This study presents a scheme to compute confidence intervals for these estimates. The recentered 90 percent confidence interval for the estimated inferred oil of 48 BBO is 25 BBO and 82 BBO. Similarly, the endpoints of the confidence interval about inferred reserve estimate of 313 TCF are 227 TCF and 439 TCF. The range of the estimates provides a basis for development of scenarios for projecting reserve additions and ultimately oil and gas production, information important to energy policy analysis.

Bulletin↗
USGS1968

Platinum deposits of Alaska

The placer deposits of the Goodnews Bay district in southwestern Alaska have yielded the only significant production of platinum metals in the United States, although small amounts of platinum metals have been produced from other deposits in Alaska and elsewhere in the United States. The Goodnews Bay deposits were described by Mertie in U.S. Geological Survey Bulletin 918 (1940). Many new data have been obtained since that time, and in order to make this information available in advance of publication, this report on Platinum deposits of Alaska has been placed on open-file.

Alaska↗
USGS2009

BSSA: Worth thinking about

The Bulletin of the Seismological Society of America ( BSSA ) is a powerful community project that has helped us share the information necessary to keep our field moving forward since 1911. In some ways, BSSA is much like it has always been, and each issue provides us with a collection of research that has been improved by the peer review process and copyedited, typeset, and printed to make it easily readable. But BSSA has also constantly evolved, and the online edition with full-text searching of all content back to volume 1 and linked references that speed our navigation through the related literature is unlike anything J. C. Branner could have imagined when he edited the first issue.

Seismological Research Letters↗
USGS1954

Southern California Water Bulletin for 1953: General review of the water resources of Southern California for the water year of 1952-53 with special reference to the surface runoff for the water year of 1951-52

This WATER BULLETTIN is one of a series issued annually since June 1944. Its main purpose is to present a brief analysis of those phases of the local water supply associated with the work of the Geological Survey. The first part of this review deals with the water resources for the water year ending September 30, 1953. It contains a brief analysis of the annual precipitation, the provisional runoff at a few stations, the changes in water reserves both in surface reservoirs and underground, and the imported waters. It concludes by pointing out the deficiences in the local water reserves. This bulletin has been prepared by the Surface Water Branch; the section on ground-water conditions was prepared chiefly from information supplied by the Ground Hater Branch.

California↗
USGS2016

A strategy for recovering continuous behavioral telemetry data from Pacific walruses

Tracking animal behavior and movement with telemetry sensors can offer substantial insights required for conservation. Yet, the value of data collected by animal-borne telemetry systems is limited by bandwidth constraints. To understand the response of Pacific walruses ( Odobenus rosmarus divergens ) to rapid changes in sea ice availability, we required continuous geospatial chronologies of foraging behavior. Satellite telemetry offered the only practical means to systematically collect such data; however, data transmission constraints of satellite data-collection systems limited the data volume that could be acquired. Although algorithms exist for reducing sensor data volumes for efficient transmission, none could meet our requirements. Consequently, we developed an algorithm for classifying hourly foraging behavior status aboard a tag with limited processing power. We found a 98% correspondence of our algorithm's classification with a test classification based on time–depth data recovered and characterized through multivariate analysis in a separate study. We then applied our algorithm within a telemetry system that relied on remotely deployed satellite tags. Data collected by these tags from Pacific walruses across their range during 2007–2015 demonstrated the consistency of foraging behavior collected by this strategy with data collected by data logging tags; and demonstrated the ability to collect geospatial behavioral chronologies with minimal missing data where recovery of data logging tags is precluded. Our strategy for developing a telemetry system may be applicable to any study requiring intelligent algorithms to continuously monitor behavior, and then compress those data into meaningful information that can be efficiently transmitted.

Wildlife Society Bulletin↗
USGS2023

Spatio-temporal clustering of post-caldera eruptions at Yellowstone caldera: Implications for volcanic hazards and pre-eruptive magma reservoir configuration

At least 28 rhyolitic lava flows, domes, and tuffs erupted within Yellowstone caldera following its formation 631 ka. Understanding the timing of intracaldera eruptions is essential for characterizing natural hazards posed by Yellowstone volcano. We present 40 Ar/ 39 Ar eruption ages for the Mallard Lake Member and Central Plateau Member of the Plateau Rhyolite, which comprise products from 22 eruptions spanning ~160 to ~70 ka. These eruptions occurred along two linear vent zones within Yellowstone caldera that appear to be extensions of major extracaldera normal faults. Eruptions took place in five brief clusters with group mean ages of 160.3±1.0 ka (2σ), 149.8±4.0 ka, 111.4±0.9 ka, 104.1±0.8 ka, and 70.8±0.7 ka. All mapped products within each informal group have indistinguishable 40 Ar/ 39 Ar eruption ages implying brief eruption durations. Eruption products of each group are spatially clustered, with only one of the two linear vent zones being active during an eruption group. Using the oldest group (160 ka), we apply paleomagnetic and geochemical analyses to investigate the duration of these eruption groups and their pre-eruptive magma reservoir configuration. Paleomagnetic analyses suggest that the nine rhyolite eruptions ~160 ka spanned 400 years or less. Glass and sanidine compositions of each rhyolite are nearly identical, which is consistent with pre-eruptive storage of a large (~130 km 3 ), interconnected melt body within Yellowstone volcano’s crystal-rich magma reservoir. These characteristics differ from intracaldera eruptions that vented near the caldera’s inner ring fracture system, which tend to be compositionally disparate with less temporal clustering. These insights inform hazard mitigation scenarios.

Idaho, Wyoming↗
USGS2006

Explosion source strong ground motions in the Mississippi embayment

Two strong-motion arrays were deployed for the October 2002 Embayment Seismic Excitation Experiment to study the spatial variation of strong ground motions in the deep, unconsolidated sediments of the Mississippi embayment because there are no comparable strong-motion data from natural earthquakes in the area. Each linear array consisted of eight three-component K2 accelerographs spaced 15 m apart situated 1.2 and 2.5 kin from 2268-kg and 1134-kg borehole explosion sources, respectively. The array data show distinct body-wave and surface-wave arrivals that propagate within the thick, unconsolidated sedimentary column, the high-velocity basement rocks, and small-scale structure near the surface. Time-domain coherence of body-wave and surface-wave arrivals is computed for acceleration, velocity, and displacement time windows. Coherence is high for relatively low-frequency verticalcomponent Rayleigh waves and high-frequency P waves propagating across the array. Prominent high-frequency PS conversions seen on radial components, a proxy for the direct S wave from earthquake sources, lose coherence quickly over the 105-m length of the array. Transverse component signals are least coherent for any ground motion and appear to be highly scattered. Horizontal phase velocity is computed by using the ratio of particle velocity to estimates of the strain based on a plane-wave-propagation model. The resulting time-dependent phase-velocity map is a useful way to infer the propagation mechanisms of individual seismic phases and time windows of three-component waveforms. Displacement gradient analysis is a complementary technique for processing general spatial-array data to obtain horizontal slowness information.

Arkansas, Missouri, Tennessee↗
USGS2022

Waveform signatures of earthquakes located close to the subducted Gorda Plate interface

Complex seismic velocity structure near the earthquake source can affect rupture dynamics and strongly modify the seismic waveforms recorded near the fault. Fault‐zone waves are commonly observed in continental crustal settings but are less clear in subduction zones due to the spatial separation between seismic stations and the plate boundary fault. We observed anomalously long duration S waves from earthquake clusters located near the interface of the subducted Gorda plate north of the Mendocino triple junction. In contrast, earthquakes located just a few kilometers below each cluster show impulsive S waves. A nodal array experiment was conducted around the Northern California Seismic Network station KCT for two months to investigate the origin of the complex S waves. Beamforming analysis shows that the S waves contain three arrivals that have different horizontal slownesses, which we term S 1, S 2, and S coda. Similar analysis on P waves also show two arrivals with different horizontal slownesses, which we term P 1 and P 2. P 1 and S 1 have larger horizontal slowness than P 2 and S 2, respectively, indicating that the phase pairs are body waves with different ray paths. Building upon a seismic refraction profile, we construct 1D velocity models and test different thicknesses and V P / V S ratios for the subducted oceanic crust. The arrival times and relative slownesses of P 1/ P 2 and S 1/ S 2 phases indicate that they are the direct and the Moho reflected phases, respectively. Their properties are consistent with a crustal thickness of ∼6 km and a moderate V P / V S ratio (∼1.8). The S coda is more difficult to characterize but has a clear dominant frequency that likely reflects the near‐source velocity and attenuation structure. Our study indicates that waveforms from earthquakes near the interface of the subducted slab can be used to infer detailed structural information about the plate‐boundary zone at seismogenic depths.

California↗