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At least 37 records · Page 2Linked to original sources
USGS1964

Variations in regional traveltimes

Precise epicentral location of a seismic event is made difficult by variations in regional traveltimes. A discussion is presented on delays to be expected in the various segments of a generalized travel path of seismic waves. Traveltime variations caused by changes in crustal structure and velocity introduce a major part of the uncertainty in traveltime at both the seismic source and receiver. Consideration of geologic factors that tend to be related to crustal thickness and mantle velocity may permit an estimate of the amount of delay introduced at the source. Delay at the seismic receiving stations can be determined and corrected for by a study of crustal thickness and a calibration of the velocity structure under the stations.

Crustal Studies Technical Letter↗
USGS1964

Compilation of seismic-refraction crustal data in the Soviet Union

The U.S. Geological Survey is preparing a series of terrain atlases of the Sino-Soviet bloc of nations for use in a possible nuclear-test detection program. Part of this project is concerned with the compilation and evaluation of crustal-structure data. To date, a compilation has been made of data from Russian publications that discuss seismic refraction and gravity studies of crustal structure. Although this compilation deals mainly with explosion seismic-refraction measurements, some results from earthquake studies are also included. None of the data have been evaluated.

Crustal Studies Technical Letter↗
USGS1964

Crustal structure in the eastern Colorado Plateaus Provence from seismic-refraction measurements

A reversed seismic-refraction profile was recorded in the Colorado Plateaus Province from Hanksville, Utah, to Chinle, Arizona, The velocity of P g is 6.2 km/sec, and the true velocity of P n is 7.8 km/sec, Waves identified as reflections indicate that an intermediate layer in the crust has a velocity of approximately 6.8 km/sec. Thickness of the crust is 43 km at Chinle and 40 km at Hanksville. The P n velocity in the Colorado Plateaus Province is the same as that in the Basin and Range Province, but is significantly lower than Pn in the High Plains of Colorado.

Arizona;Colorado;Utah↗
USGS1964

Continental crust

The structure of the Earth’s crust (the outer shell of the earth above the M-discontinuity) has been intensively studied in many places by use of geophysical methods. The velocity of seismic compressional waves in the crust and in the upper mantle varies from place to place in the conterminous United States. The average crust is thick in the eastern two-thirds of the United States, in which the crustal and upper-mantle velocities tend to be high. The average crust is thinner in the western one-third of the United States, in which these velocities tend to be low. The concept of eastern and western superprovinces can be used to classify these differences. Crustal and upper-mantle densities probably vary directly with compressional-wave velocity, leading to the conclusion that isostasy is accomplished by the variation in densities of crustal and upper-mantle rocks as well as in crustal thickness, and that there is no single, generally valid isostatic model. The nature of the M-discontinuity is still speculative.

Crustal Studies Technical Letter↗
USGS1964

Seismic-refraction measurements of crustal structure between American Falls Reservoir, Idaho, and Flaming Gorge Reservoir, Utah

Interpretation of a reversed seismic-refraction profile recorded between American Falls reservoir and Flaming Gorge reservoir in May 1963 indicates that the depth to the Mohorovicic discontinuity is about 31 km at American Falls and 37 km at Flaming Gorge. The existence of an intermediate crustal layer at a depth of about 19 to 21 km beneath the profile is well supported by refractions and reflections. The velocity of compressional waves in the mantle just beneath the Mohorovicic discontinuity is about 7.8 km/sec, their velocity in the intermediate layer is about 6.9 km/sec, and their velocity in the upper crust (beneath the near-surface low-velocity material) is about 5.9 km/sec. A prominent phase with an apparent velocity of 8.4 km/sec was recorded at distances of 210 km to 325 km from shots at American Falls. This phase is believed to be a reflection from a boundary within the mantle.

Idaho, Utah↗
USGS1964

Crustal structure between Lake Mead, Nevada, and Mono Lake, California

Interpretation of a reversed seismic-refraction profile between Lake Mead, Nevada, and Mono Lake, California, indicates velocities of 6.15 km/sec for the upper layer of the crust, 7.10 km/sec for an intermediate layer, and 7.80 km/sec for the uppermost mantle. Phases interpreted to be reflections from the top of the intermediate layer and the Mohorovicic discontinuity were used with the refraction data to calculate depths. The depth to the Moho increases from about 30 km near Lake Mead to about 40 km near Mono Lake. Variations in arrival times provide evidence for fairly sharp flexures in the Moho. Offsets in the Moho of 4 km at one point and 2 1/2 km at another correspond to large faults at the surface, and it is suggested that fracture zones in the upper crust may displace the Moho and extend into the upper mantle. The phase P appears to be an extension of the reflection from the top of the intermediate layer beyond the critical angle. Bouguer gravity, computed for the seismic model of the crust, is in good agreement with the measured Bouguer gravity. Thus a model of the crustal structure is presented which is consistent with three semi-independent sources of geophysical data: seismic-refraction, seismic-reflection, and gravity.

California, Nevada↗
USGS1964

A preliminary summary of a seismic-refraction survey in the vicinity of the Tonto Forest Observatory, Arizona

The U.S. Geological Survey complete d a seismic-refraction survey in the vicinity of the Tonto Forest Seismological Observatory (T.F.S.O.) in April and May 1964. More than 1200 km of reversed profiles were surveyed to determine the crustal structure and crustal and upper mantle velocities in this area. The purpose of this work was to provide information on wave-propagation paths of seismic events recorded at T.F.S.O. and to improve the performance of the Observatory in locating and identifying these events. First arrivals indicate that the Mohorovicic discontinuity dips to the northeast by as much as 6 degrees under T.F.S.O., and may even be displaced vertically by as much as 5 km immediately north of the Observatory near the boundary of the Basin and Range and the Colorado Plateau Provinces. A preliminary examination of the first arrivals indicates that the crust at T.F.S.O. is at least 30 km thick and is made up of at least two seismic layers. A thin veneer at the surface with a velocity of approximately 4 km/sec is underlain by a layer with a velocity of approximately 5.9 km/sec to 6.1 km/sec. An intermediate layer with velocity of 6.6 to 7.0 km/sec is probably present in the lower crust, but is not revealed by first arrivals. The velocity of seismic waves in the upper mantle is about 7.9 km/sec.

Arizona↗
USGS1964

Seismic-refraction measurements of crustal structure between Nevada Test Site and Ludlow, California

Seismic-refraction measurements from nuclear and chemical explosions were made along a line from the Nevada Test Site (NTS) to Ludlow, California, and additional recordings from nuclear explosions were made southward toward Calexico, California. The time of first arrivals from the Ludlow shotpoint is expressed as T 0 = 0.00 + Δ/2.50 (assumed), T 1 = 1.00 + Δ6.10, T 2 = 2.81 + Δ/6.80, and T 3 = 5.48 + ~7.76, where T is in seconds and distance Δ is in km. First arrival times from NTS fit the lines T 1 = 0.74 + Δ/6.10, T 2 = 2.81 + Δ/6.80 (assumed), T 3 = 6.70 + Δ/8.04 to a distance of 265 km, beyond 265 km T 3 = 5.83 + Δ/7.75. The difference in the apparent velocities of the P n (T 3 ) arrival is caused by variations in the dip of the Mohorovicic discontinuity. The thickness of the successive layers at NTS are H 0 s 1.0 km (V 0 ~ 2.5 km/sec), H 1 = 13 km (v 1 = 6.1 km/sec), and H 2 = 20 km (v 2 = 6.8 km/ sec); the total crustal thickness is 34 km. The successive crustal layers at Ludlow have a thickness of H 0 = 1.4 km, H 1 = 13 km, and H 2 = 13 km; the total crustal thickness is 27 km.

Arizona, California, Nevada↗
USGS1965

Calculations of upper-mantle velocity from published Soviet earthquake data

The lack of information on mantle velocities and crustal structure of the U.S.S.R. has led to a preliminary examination of published Soviet earthquake bulletins in the hope of deriving useful velocity and structure information from the data they contain. Mantle velocities deduced from earthquake data on several Russian earthquakes are in excellent agreement with results of Soviet deep seismic sounding.

Soviet Union↗
USGS2023

Induced seismicity and its impact on existing seismic hazard analysis

We develop a scheme for mapping changes in earthquake rates within a region in near-real-time. A specific goal of the work is to track recent changes in the rates of induced earthquakes in the central and eastern United States. We map rates in a time window of interest, map rates in a preceding time window, and then ratio the two maps to show changes. A proof-of-concept map is first prepared, comparing rates during the first six months of 2010 with rates from the preceding five years; this demonstration map shows, among other things, the growth of induced seismicity in Oklahoma during 2010. We then present a series of ten ratio maps: the first six months of 2018 compared with the preceding five years, and so on in six-month increments through the end of 2022. These maps show changes in the rates and locations of induced earthquakes, as well as other seismicity trends. Map regions, time windows, and other model parameters are easily adaptable for other applications.

Technical Letter Report↗
USGS1958

A compilation of chemical quality data for ground and surface waters in Utah

An accelerated use of water resulting from a growing population, industrial expansion, and irrigation has brought into focus the importance of the quality as well as the quantity of this natural resource in Utah. As new demands are made on the existing supply, a search goes on for new sources of ground and surface water. These new sources must not only meet quantity requirements, but also must fall within certain limits of chemical composition - in relation to its proposed use. The prime purpose of this report is to compile into one volume all of the available information that exists on the quality of ground and surface water in Utah. The various sources of information, named in the preface, have supplied data obtained through their own organizations. Analyses from these sources may be identified by reference to the indicated 2-letter code on the data sheets.

Utah↗
USGS2016

Summary of SPT based field case history data of CETIN (2016) database

This report provides documentation of the Cetin et al. (2016) field performance case histories, probabilistic maximum likelihood assessment and the sources of differences between the liquefaction triggering resistance estimations (CRR values) of the widely used liquefaction triggering relationships of Seed et al. (1985), Cetin et al. (2004, 2016) and Boulanger and Idriss (2012). Cetin et al. (2016-a) presented a concise summary of the improved database and the updated triggering relationships. For the sake of completeness, as part of Chapter 2 of this report, Cetin et al. (2016-a) manuscript is re-presented, as edited to include the electronic supplements, and a broader and more detailed documentation of all of case histories. This broader and more detailed documentation along with the interpretations of other researchers is presented in Appendix A. Similarly, site response analyses details and results from Cetin (2000) is re-presented in Appendix B. To enable the readers to quickly refer to Cetin and Seed (2004), it is also included in Appendix C. The sources of differences between the liquefaction triggering resistance estimations (CRR values) of the widely used liquefaction triggering relationships of Seed et al. (1985), Cetin et al. (2004) and Boulanger and Idriss (2012) were discussed in Cetin et al. (2016-b). Again, for the sake of completeness, as part of Chapter 3 of this report, Cetin et al. (2016-b) manuscript is re-presented, as edited to the include of electronic supplements, and a detailed response to issues addressed by Idriss and Boulanger (2012). Also, the technical response letter (Cetin, 2014) prepared at the request of the members of the NRC Committee on the State of the Art and Practice in Earthquake Induced Soil Liquefaction Assessment, is given in Appendix D, which is helpful to follow the technical discussions. This report is intended only as a concise summary of a vast amount of data. The interpretations presented are those of the research team. A more detailed description of some of the details of the methods and procedures used to evaluate and analyze these field performance case histories is also presented in Cetin (2000) and Cetin et al. (2000) though the final evaluations presented in this report are the most recent interpretations undertaken under these current studies.

Report↗
USGS1982

WOLF; automatic typing program

A FORTRAN IV program for the Hewlett-Packard 1000 series computer provides for automatic typing operations and can, when employed with manufacturer's text editor, provide a system to greatly facilitate preparation of reports, letters and other text. The input text and imbedded control data can perform nearly all of the functions of a typist. A few of the features available are centering, titles, footnotes, indentation, page numbering (including Roman numerals), automatic paragraphing, and two forms of tab operations. This documentation contains both user and technical description of the program.

Open-File Report↗
USGS2014

Reanalysis of historical U.S. Geological Survey sediment samples for geochemical data from the western part of the Wrangellia terrane, Anchorage, Gulkana, Healy, Mt. Hayes, Nabesna, and Talkeetna Mountains quadrangles, Alaska

The State of Alaska’s Strategic and Critical Minerals (SCM) Assessment project, a State-funded Capital Improvement Project (CIP), is designed to evaluate Alaska’s statewide potential for SCM resources. The SCM Assessment is being implemented by the Alaska Division of Geological & Geophysical Surveys (DGGS), and involves obtaining new airborne-geophysical, geological, and geochemical data. For the geochemical part of the SCM Assessment, thousands of historical geochemical samples from DGGS, U.S. Geological Survey (USGS), and U.S. Bureau of Mines archives are being reanalyzed by DGGS using modern, quantitative, geochemical-analytical methods. The objective is to update the statewide geochemical database to more clearly identify areas in Alaska with SCM potential. The USGS is also undertaking SCM-related geologic studies in Alaska through the federally funded Alaska Critical Minerals cooperative project. DGGS and USGS share the goal of evaluating Alaska’s strategic and critical minerals potential and together created a Letter of Agreement (signed December 2012) and a supplementary Technical Assistance Agreement (#14CMTAA143458) to facilitate the two agencies’ cooperative work. Under these agreements, DGGS contracted the USGS in Denver to reanalyze historical USGS sediment samples from Alaska. For this report, DGGS funded reanalysis of 1,682 historical USGS sediment samples from the statewide Alaska Geochemical Database Version 2.0 (AGDB2; Granitto and others, 2013). Samples were chosen from an area covering the western half of the Wrangellia Terrane in the Anchorage, Gulkana, Healy, Mt. Hayes, Nabesna, and Talkeetna Mountains quadrangles of south-central Alaska (fig. 1). USGS was responsible for sample retrieval from the Denver warehouse through the final quality assurance/quality control (QA/QC) of the geochemical analyses obtained through the USGS contract lab. The new geochemical data are published in this report as a coauthored DGGS report, and will be incorporated into the statewide geochemical databases of both agencies.

Alaska↗
USGS2015

Geochemical reanalysis of historical U.S. Geological Survey sediment samples from the Inmachuk, Kugruk, Kiwalik, and Koyuk River drainages, Granite Mountain, and the northern Darby Mountains, Bendeleben, Candle, Kotzebue, and Solomon quadrangles, Alaska

The State of Alaska’s Strategic and Critical Minerals (SCM) Assessment project, a State-funded Capital Improvement Project (CIP), is designed to evaluate Alaska’s statewide potential for SCM resources. The SCM Assessment is being implemented by the Alaska Division of Geological & Geophysical Surveys (DGGS), and involves obtaining new airborne-geophysical, geological, and geochemical data. As part of the SCM Assessment, thousands of historical geochemical samples from DGGS, U.S. Geological Survey (USGS), and U.S. Bureau of Mines archives are being reanalyzed by DGGS using modern, quantitative, geochemical-analytical methods. The objective is to update the statewide geochemical database to more clearly identify areas in Alaska with SCM potential. The USGS is also undertaking SCM-related geologic studies in Alaska through the federally funded Alaska Critical Minerals cooperative project. DGGS and USGS share the goal of evaluating Alaska’s strategic and critical minerals potential and together created a Letter of Agreement (signed December 2012) and a supplementary Technical Assistance Agreement (#14CMTAA143458) to facilitate the two agencies’ cooperative work. Under these agreements, DGGS contracted the USGS in Denver to reanalyze historical USGS sediment samples from Alaska. For this report, DGGS funded reanalysis of 653 historical USGS sediment samples from the statewide Alaska Geochemical Database Version 2.0 (AGDB2; Granitto and others, 2013). Samples were chosen from an area covering portions of the Inmachuk, Kugruk, Kiwalik, and Koyuk river drainages, Granite Mountain, and the northern Darby Mountains, located in the Bendeleben, Candle, Kotzebue, and Solomon quadrangles of eastern Seward Peninsula, Alaska (fig. 1). The USGS was responsible for sample retrieval from the National Geochemical Sample Archive (NGSA) in Denver, Colorado through the final quality assurance/quality control (QA/QC) of the geochemical analyses obtained through the USGS contract lab. The new geochemical data are published in this report as a coauthored DGGS report, and will be incorporated into the statewide geochemical databases of both agencies.

Alaska↗
USGS2015

Geochemical reanalysis of historical U.S. Geological Survey sediment samples from the Haines area, Juneau and Skagway quadrangles, southeast Alaska

The State of Alaska’s Strategic and Critical Minerals (SCM) Assessment project, a State-funded Capital Improvement Project (CIP), is designed to evaluate Alaska’s statewide potential for SCM resources. The SCM Assessment is being implemented by the Alaska Division of Geological & Geophysical Surveys (DGGS), and involves obtaining new airborne-geophysical, geological, and geochemical data. As part of the SCM Assessment, thousands of historical geochemical samples from DGGS, U.S. Geological Survey (USGS), and U.S. Bureau of Mines archives are being reanalyzed by DGGS using modern, quantitative, geochemical-analytical methods. The objective is to update the statewide geochemical database to more clearly identify areas in Alaska with SCM potential. The USGS is also undertaking SCM-related geologic studies in Alaska through the federally funded Alaska Critical Minerals cooperative project. DGGS and USGS share the goal of evaluating Alaska’s strategic and critical minerals potential and together created a Letter of Agreement (signed December 2012) and a supplementary Technical Assistance Agreement (#14CMTAA143458) to facilitate the two agencies’ cooperative work. Under these agreements, DGGS contracted the USGS in Denver to reanalyze historical USGS sediment samples from Alaska. For this report, DGGS funded reanalysis of 212 historical USGS sediment samples from the statewide Alaska Geochemical Database Version 2.0 (AGDB2; Granitto and others, 2013). Samples were chosen from the Chilkat, Klehini, Tsirku, and Takhin river drainages, as well as smaller drainages flowing into Chilkat and Chilkoot Inlets near Haines, Skagway Quadrangle, Southeast Alaska. Additionally some samples were also chosen from the Juneau gold belt, Juneau Quadrangle, Southeast Alaska (fig. 1). The USGS was responsible for sample retrieval from the National Geochemical Sample Archive (NGSA) in Denver, Colorado through the final quality assurance/quality control (QA/QC) of the geochemical analyses obtained through the USGS contract lab. The new geochemical data are published in this report as a coauthored DGGS report, and will be incorporated into the statewide geochemical databases of both agencies.

Alaska↗
USGS2015

Geochemical reanalysis of historical U.S. Geological Survey sediment samples from the Kougarok area, Bendeleben and Teller quadrangles, Seward Peninsula, Alaska

The State of Alaska’s Strategic and Critical Minerals (SCM) Assessment project, a State-funded Capital Improvement Project (CIP), is designed to evaluate Alaska’s statewide potential for SCM resources. The SCM Assessment is being implemented by the Alaska Division of Geological & Geophysical Surveys (DGGS), and involves obtaining new airborne-geophysical, geological, and geochemical data. As part of the SCM Assessment, thousands of historical geochemical samples from DGGS, U.S. Geological Survey (USGS), and U.S. Bureau of Mines archives are being reanalyzed by DGGS using modern, quantitative, geochemical-analytical methods. The objective is to update the statewide geochemical database to more clearly identify areas in Alaska with SCM potential. The USGS is also undertaking SCM-related geologic studies in Alaska through the federally funded Alaska Critical Minerals cooperative project. DGGS and USGS share the goal of evaluating Alaska’s strategic and critical minerals potential and together created a Letter of Agreement (signed December 2012) and a supplementary Technical Assistance Agreement (#14CMTAA143458) to facilitate the two agencies’ cooperative work. Under these agreements, DGGS contracted the USGS in Denver to reanalyze historical USGS sediment samples from Alaska. For this report, DGGS funded reanalysis of 302 historical USGS sediment samples from the statewide Alaska Geochemical Database Version 2.0 (AGDB2; Granitto and others, 2013). Samples were chosen from the Kougarok River drainage as well as smaller adjacent drainages in the Bendeleben and Teller quadrangles, Seward Peninsula, Alaska (fig. 1). The USGS was responsible for sample retrieval from the National Geochemical Sample Archive (NGSA) in Denver, Colorado through the final quality assurance/quality control (QA/QC) of the geochemical analyses obtained through the USGS contract lab. The new geochemical data are published in this report as a coauthored DGGS report, and will be incorporated into the statewide geochemical databases of both agencies.

Alaska↗