Results for “Surveys in Geophysics” — Page 6

USGS2007

Archive of digital chirp seismic reflection data collected during USGS cruise 05SCC01 offshore of Port Fourchon and Timbalier Bay, Louisiana, August 2005

In August of 2005, the U.S. Geological Survey conducted geophysical surveys offshore of Port Fourchon and Timbalier Bay, Louisiana, and in nearby waterbodies. This report serves as an archive of unprocessed digital chirp seismic reflection data, trackline maps, navigation files, GIS information, Field Activity Collection System (FACS) logs, observer's logbook, and formal FGDC metadata. Filtered and gained digital images of the seismic profiles are also provided. The archived trace data are in standard Society of Exploration Geophysicists (SEG) SEG-Y format (Barry and others, 1975) and may be downloaded and processed with commercial or public domain software such as Seismic Unix (SU). Example SU processing scripts and USGS software for viewing the SEG-Y files (Zihlman, 1992) are also provided.

Louisiana↗

USGS2007

Archive of digital CHIRP seismic reflection data collected during USGS cruise 06FSH01 offshore of Siesta Key, Florida, May 2006

In May of 2006, the U.S. Geological Survey conducted geophysical surveys offshore of Siesta Key, Florida. This report serves as an archive of unprocessed digital chirp seismic reflection data, trackline maps, navigation files, GIS information, Field Activity Collection System (FACS) logs, observer's logbook, and formal FGDC metadata. Gained digital images of the seismic profiles are also provided. The archived trace data are in standard Society of Exploration Geophysicists (SEG) SEG-Y format (Barry and others, 1975) and may be downloaded and processed with commercial or public domain software such as Seismic Unix (SU). Example SU processing scripts and USGS software for viewing the SEG-Y files (Zihlman, 1992) are also provided.

Florida↗

USGS2007

Archive of digital and digitized analog boomer seismic reflection data collected during USGS cruise 96CCT02 in Copano, Corpus Christi, and Nueces Bays and Corpus Christi Bayou, Texas, July 1996

In June of 1996, the U.S. Geological Survey conducted geophysical surveys from Nueces to Copano Bays, Texas. This report serves as an archive of unprocessed digital boomer seismic reflection data, trackline maps, navigation files, GIS information, cruise log, and formal FGDC metadata. Filtered and gained digital images of the seismic profiles and high resolution scanned TIFF images of the original paper printouts are also provided. The archived trace data are in standard Society of Exploration Geophysicists (SEG) SEG-Y format (Barry and others, 1975) and may be downloaded and processed with commercial or public domain software such as Seismic Unix (SU). Example SU processing scripts and USGS software for viewing the SEG-Y files (Zihlman, 1992) are also provided.

Texas↗

USGS2007

Archive of digital boomer and CHIRP seismic reflection data collected during USGS cruise 06FSH03 offshore of Fort Lauderdale, Florida, September 2006

In September of 2006, the U.S. Geological Survey conducted geophysical surveys offshore of Fort Lauderdale, FL. This report serves as an archive of unprocessed digital boomer and CHIRP seismic reflection data, trackline maps, navigation files, GIS information, Field Activity Collection System (FACS) logs, observer's logbook, and formal FGDC metadata. Filtered and gained digital images of the seismic profiles are also provided. The archived trace data are in standard Society of Exploration Geophysicists (SEG) SEG-Y format (Barry and others, 1975) and may be downloaded and processed with commercial or public domain software such as Seismic Unix (SU). Example SU processing scripts and USGS software for viewing the SEG-Y files (Zihlman, 1992) are also provided.

Florida↗

USGS2008

Archive of digital boomer seismic reflection data collected during USGS field activity 96LCA04 in Lakes Mabel and Starr, Central Florida, August 1996

In August of 1996, the U.S. Geological Survey conducted geophysical surveys of Lakes Mabel and Starr, central Florida, as part of the Central Highlands Lakes project, which is part of a larger USGS Lakes and Coastal Aquifers (LCA) study. This report serves as an archive of unprocessed digital boomer seismic reflection data, trackline maps, navigation files, Geographic Information System (GIS) files, observer's logbook; and formal Federal Geographic Data Committee (FGDC) metadata. Filtered and gained (a relative increase in signal amplitude) digital images of the seismic profiles are also provided. Refer to the Acronyms page for expansions of acronyms and abbreviations used in this report. For detailed information about the hydrologic setting of Lake Starr and the interpretation of some of these seismic reflection data, see Swancar and others (2000) at http://fl.water.usgs.gov/publications/Abstracts/wri00_4030_swancar.html. The archived trace data are in standard Society of Exploration Geophysicists (SEG) SEG-Y format (Barry and others, 1975) and may be downloaded and processed with commercial or public domain software such as Seismic Unix (SU). Example SU processing scripts and USGS software for viewing the SEG-Y files (Zihlman, 1992) are also provided. The USGS Florida Integrated Science Center (FISC) - St. Petersburg assigns a unique identifier to each cruise or field activity. For example, 96LCA04 tells us the data were collected in 1996 for the Lakes and Coastal Aquifers (LCA) study and the data were collected during the fourth field activity for that project in that calendar year. Refer to http://walrus.wr.usgs.gov/infobank/programs/html/definition/activity.html for a detailed description of the method used to assign the field activity ID. The boomer plate is an acoustic energy source that consists of capacitors charged to a high voltage and discharged through a transducer in the water. The transducer is towed on a sled floating on the water surface and when discharged emits a short acoustic pulse, or shot, which propagates through the water and sediment column. The acoustic energy is reflected at density boundaries (such as the seafloor or sediment layers beneath the lake bottom), detected by the receiver (a hydrophone streamer), and recorded by a PC-based seismic acquisition system. This process is repeated at timed intervals (for example, 0.5 s) and recorded for specific intervals of time (for example, 100 ms). In this way, a two-dimensional (2-D) vertical image of the shallow geologic structure beneath the ship track is produced. Figure 1 displays the acquisition geometry. Refer to table 1 for a summary of acquisition parameters. Table 2 lists trackline statistics. Scanned images of the handwritten cruise logbook (1,020-KB PDF) is also provided as a PDF file. The unprocessed seismic data are stored in SEG-Y format (Barry and others, 1975). For a detailed description of the data format, refer to the SEG-Y Format page. See the How To Download SEG-Y Data page for download instructions. The printable profiles provided here are GIF images that were filtered and gained using Seismic Unix software. Refer to the Software page for details about the processing and examples of the processing scripts. The processed SEG-Y data were exported to Chesapeake Technology, Inc. (CTI) SonarWeb software to produce an interactive version of the seismic profile that allows the user to obtain a geographic location and depth from the profile for a curser position. This information is displayed in the status bar of the browser.

Florida↗

USGS2012

Archive of digital boomer subbottom profile data collected in the Atlantic Ocean offshore northeast Florida during USGS cruises 03FGS01 and 03FGS02 in September and October of 2003

In September and October of 2003, the U.S. Geological Survey (USGS), in cooperation with the Florida Geological Survey, conducted geophysical surveys of the Atlantic Ocean offshore northeast Florida from St. Augustine, Florida, to the Florida-Georgia border. This report serves as an archive of unprocessed digital boomer subbottom profile data, trackline maps, navigation files, Geographic Information System (GIS) files, Field Activity Collection System (FACS) logs, and formal Federal Geographic Data Committee (FGDC) metadata. Filtered and gained (a relative increase in signal amplitude) digital images of the seismic profiles are also provided. Refer to the Acronyms page for expansions of all acronyms and abbreviations used in this report. The USGS St. Petersburg Coastal and Marine Science Center (SPCMSC) assigns a unique identifier to each cruise or field activity. For example, 03FGS01 tells us the data were collected in 2003 as part of cooperative work with the Florida Geological Survey (FGS) and that the data were collected during the first field activity for that project in that calendar year. Refer to http://walrus.wr.usgs.gov/infobank/programs/html/definition/activity.html for a detailed description of the method used to assign the field activity identification (ID). The naming convention used for each seismic line is as follows: yye##a, where 'yy' are the last two digits of the year in which the data were collected, 'e' is a 1-letter abbreviation for the equipment type (for example, b for boomer), '##' is a 2-digit number representing a specific track, and 'a' is a letter representing the section of a line if recording was prematurely terminated or rerun for quality or acquisition problems. The boomer plate is an acoustic energy source that consists of capacitors charged to a high voltage and discharged through a transducer in the water. The transducer is towed on a sled floating on the water surface and when discharged emits a short acoustic pulse, or shot, which propagates through the water, sediment column, or rock beneath. The acoustic energy is reflected at density boundaries (such as the seafloor, sediment, or rock layers beneath the seafloor), detected by hydrophone receivers, and recorded by a PC-based seismic acquisition system. This process is repeated at timed intervals (for example, 0.5 seconds) and recorded for specific intervals of time (for example, 100 milliseconds). In this way, a two-dimensional (2-D) vertical profile of the shallow geologic structure beneath the ship track is produced. Refer to the handwritten FACS operation log (PDF, 442 KB) for diagrams and descriptions of acquisition geometry, which varied throughout the cruises. Table 1 displays a summary of acquisition parameters. See the digital FACS equipment logs (PDF, 9-13 KB each) for details about the acquisition equipment used. The archived trace data are in standard Society of Exploration Geophysicists (SEG) SEG Y (Barry and others, 1975) format (rev. 0), except for the first 3,200 bytes of the card image header, which are stored in ASCII format instead of the standard EBCDIC format. The SEG Y files may be downloaded and processed with commercial or public domain software such as Seismic Unix (SU) (Cohen and Stockwell, 2005). See the How To Download SEG Y Data page for download instructions. The printable profiles provided here are Graphics Interchange Format (GIF) images that were filtered and gained using SU software. Refer to the Software page for details about the processing and links to example SU processing scripts and USGS software for viewing the SEG Y files (Zihlman, 1992).

Florida;Georgia↗

USGS2014

Archive of digital chirp subbottom profile data collected during USGS cruise 12BIM03 offshore of the Chandeleur Islands, Louisiana, July 2012

From July 23 - 31, 2012, the U.S. Geological Survey conducted geophysical surveys to investigate the geologic controls on barrier island framework and long-term sediment transport along the oil spill mitigation sand berm constructed at the north end and just offshore of the Chandeleur Islands, La. (figure 1). This effort is part of a broader USGS study, which seeks to better understand barrier island evolution over medium time scales (months to years). This report serves as an archive of unprocessed digital chirp subbottom data, trackline maps, navigation files, Geographic Information System (GIS) files, Field Activity Collection System (FACS) logs, and formal Federal Geographic Data Committee (FGDC) metadata. Gained (showing a relative increase in signal amplitude) digital images of the seismic profiles are also provided. Refer to the Abbreviations page for expansions of acronyms and abbreviations used in this report. The USGS St. Petersburg Coastal and Marine Science Center (SPCMSC) assigns a unique identifier to each cruise or field activity. For example, 12BIM03 tells us the data were collected in 2012 during the third field activity for that project in that calendar year and BIM is a generic code, which represents efforts related to Barrier Island Mapping. Refer to http://walrus.wr.usgs.gov/infobank/programs/html/definition/activity.html for a detailed description of the method used to assign the field activity ID. All chirp systems use a signal of continuously varying frequency; the EdgeTech SB-424 system used during this survey produces high-resolution, shallow-penetration (typically less than 50 milliseconds (ms)) profile images of sub-seafloor stratigraphy. The towfish contains a transducer that transmits and receives acoustic energy and is typically towed 1 - 2 m below the sea surface. As transmitted acoustic energy intersects density boundaries, such as the seafloor or sub-surface sediment layers, energy is reflected back toward the transducer, received, and recorded by a PC-based seismic acquisition system. This process is repeated at regular time intervals (for example, 0.125 seconds (s)) and returned energy is recorded for a specific duration (for example, 50 ms). In this way, a two-dimensional (2-D) vertical image of the shallow geologic structure beneath the ship track is produced. Figure 2 displays the acquisition geometry. Refer to table 1 for a summary of acquisition parameters and table 2 for trackline statistics. The archived trace data are in standard Society of Exploration Geophysicists (SEG) SEG Y rev. 0 format (Barry and others, 1975); the first 3,200 bytes of the card image header are in ASCII format instead of EBCDIC format. The SEG Y files may be downloaded and processed with commercial or public domain software such as Seismic Unix (SU) (Cohen and Stockwell, 2010). See the How To Download SEG Y Data page for download instructions. The web version of this archive does not contain the SEG Y trace files. These files are very large and would require extremely long download times. To obtain the complete DVD archive, contact USGS Information Services at 1-888-ASK-USGS or infoservices@usgs.gov. The printable profiles provided here are GIF images that were processed and gained using SU software and can be viewed from the Profiles page or from links located on the trackline maps; refer to the Software page for links to example SU processing scripts. The SEG Y files are available on the DVD version of this report or on the Web, downloadable via the USGS Coastal and Marine Geoscience Data System (http://cmgds.marine.usgs.gov). The data are also available for viewing using GeoMapApp (http://www.geomapapp.org) and Virtual Ocean (http://www.virtualocean.org) multi-platform open source software. Detailed information about the navigation system used can be found in table 1 and the Field Activity Collection System (FACS) logs. To view the trackline maps and navigation files, and for more information about these items, see the Navigation page.

Louisiana↗

USGS2004

Archive of digital boomer and chirp seismic reflection data collected during USGS Cruises 01RCE05 and 02RCE01 in the Lower Atchafalaya River, Mississippi River Delta, and offshore southeastern Louisiana, October 23-30, 2001, and August 18-19, 2002

In October of 2001 and August of 2002, the U.S. Geological Survey conducted geophysical surveys of the Lower Atchafalaya River, the Mississippi River Delta, Barataria Bay, and the Gulf of Mexico south of East Timbalier Island, Louisiana. This report serves as an archive of unprocessed digital marine seismic reflection data, trackline maps, navigation files, observers' logbooks, GIS information, and formal FGDC metadata. In addition, a filtered and gained GIF image of each seismic profile is provided. The archived trace data are in standard Society of Exploration Geophysicists (SEG) SEG-Y format (Barry and othes, 1975) and may be downloaded and processed with commercial or public domain software such as Seismic Unix (SU). Examples of SU processing scripts and in-house (USGS) software for viewing SEG-Y files (Zihlman, 1992) are also provided. Processed profile images, trackline maps, navigation files, and formal metadata may be viewed with a web browser. Scanned handwritten logbooks and Field Activity Collection System (FACS) logs may be viewed with Adobe Reader.

Louisiana↗

USGS2001

Catalog of earthquake hypocenters at Alaskan volcanoes: January 1, 1994 through December 31, 1999

The Alaska Volcano Observatory (AVO), a cooperative program of the U.S. Geological Survey, the Geophysical Institute of the University of Alaska - Fairbanks, and the Alaska Division of Geological and Geophysical Surveys, has maintained a seismic monitoring program at potentially active volcanoes in Alaska since 1988 (Power and others, 1993; Jolly and others, 1996). The primary objectives of this program are the seismic surveillance of active, potentially hazardous, Alaskan volcanoes and the investigation of seismic processes associated with active volcanism. Between 1994 and 1999, the AVO seismic monitoring program underwent significant changes with networks added at new volcanoes during each summer from 1995 through 1999. The existing network at Katmai –Valley of Ten Thousand Smokes (VTTS) was repaired in 1995, and new networks were installed at Makushin (1996), Akutan (1996), Pavlof (1996), Katmai - south (1996), Aniakchak (1997), Shishaldin (1997), Katmai - north (1998), Westdahl, (1998), Great Sitkin (1999) and Kanaga (1999). These networks added to AVO's existing seismograph networks in the Cook Inlet area and increased the number of AVO seismograph stations from 46 sites and 57 components in 1994 to 121 sites and 155 components in 1999. The 1995–1999 seismic network expansion increased the number of volcanoes monitored in real-time from 4 to 22, including Mount Spurr, Redoubt Volcano, Iliamna Volcano, Augustine Volcano, Mount Snowy, Mount Griggs, Mount Katmai, Novarupta, Trident Volcano, Mount Mageik, Mount Martin, Aniakchak Crater, Pavlof Volcano, Mount Dutton, Isanotski volcano, Shisaldin Volcano, Fisher Caldera, Westdahl volcano, Akutan volcano, Makushin Volcano, Great Sitkin volcano, and Kanaga Volcano (see Figures 1-15). The network expansion also increased the number of earthquakes located from about 600 per year in1994 and 1995 to about 3000 per year between 1997 and 1999. Highlights of the catalog period include: 1) a large volcanogenic seismic swarm at Akutan volcano in March and April 1996 (Lu and others, 2000); 2) an eruption at Pavlof Volcano in fall 1996 (Garces and others, 2000; McNutt and others, 2000); 3) an earthquake swarm at Iliamna volcano between September and December 1996; 4) an earthquake swarm at Mount Mageik in October 1996 (Jolly and McNutt, 1999); 5) an earthquake swarm located at shallow depth near Strandline Lake; 6) a strong swarm of earthquakes near Becharof Lake; 7) precursory seismicity and an eruption at Shishaldin Volcano in April 1999 that included a 5.2 ML earthquake and aftershock sequence (Moran and others, in press; Thompson and others, in press). The 1996 calendar year is also notable as the seismicity rate was very high, especially in the fall when 3 separate areas (Strandline Lake, Iliamna Volcano, and several of the Katmai volcanoes) experienced high rates of located earthquakes. This catalog covers the period from January 1, 1994, through December 31,1999, and includes: 1) earthquake origin times, hypocenters, and magnitudes with summary statistics describing the earthquake location quality; 2) a description of instruments deployed in the field and their locations and magnifications; 3) a description of earthquake detection, recording, analysis, and data archival; 4) velocity models used for earthquake locations; 5) phase arrival times recorded at individual stations; and 6) a summary of daily station usage from throughout the report period. We have made calculated hypocenters, station locations, system magnifications, velocity models, and phase arrival information available for download via computer network as a compressed Unix tar file.

Alaska↗

USGS2002

Catalog of earthquake hypocenters at Alaskan volcanoes: January 1, 2000 through December 31, 2001

The Alaska Volcano Observatory (AVO), a cooperative program of the U.S. Geological Survey, the Geophysical Institute of the University of Alaska Fairbanks, and the Alaska Division of Geological and Geophysical Surveys, has maintained seismic monitoring networks at potentially active volcanoes in Alaska since 1988 (Power and others, 1993; Jolly and others, 1996; Jolly and others, 2001). The primary objectives of this program are the seismic surveillance of active, potentially hazardous, Alaskan volcanoes and the investigation of seismic processes associated with active volcanism. This catalog reflects the status and evolution of the seismic monitoring program, and presents the basic seismic data for the time period January 1, 2000, through December 31, 2001. For an interpretation of these data and previously recorded data, the reader should refer to several recent articles on volcano related seismicity on Alaskan volcanoes in Appendix G. The AVO seismic network was used to monitor twenty-three volcanoes in real time in 2000-2001. These include Mount Wrangell, Mount Spurr, Redoubt Volcano, Iliamna Volcano, Augustine Volcano, Katmai Volcanic Group (Snowy Mountain, Mount Griggs, Mount Katmai, Novarupta, Trident Volcano, Mount Mageik, Mount Martin), Aniakchak Crater, Pavlof Volcano, Mount Dutton, Isanotski Peaks, Shishaldin Volcano, Fisher Caldera, Westdahl Peak, Akutan Peak, Makushin Volcano, Great Sitkin Volcano, and Kanaga Volcano (Figure 1). AVO located 1551 and 1428 earthquakes in 2000 and 2001, respectively, on and around these volcanoes. Highlights of the catalog period (Table 1) include: volcanogenic seismic swarms at Shishaldin Volcano between January and February 2000 and between May and June 2000; an eruption at Mount Cleveland between February and May 2001; episodes of possible tremor at Makushin Volcano starting March 2001 and continuing through 2001, and two earthquake swarms at Great Sitkin Volcano in 2001. This catalog includes: (1) earthquake origin times, hypocenters, and magnitudes with summary statistics describing the earthquake location quality; (2) a description of instruments deployed in the field and their locations; (3) a description of earthquake detection, recording, analysis, and data archival systems; (4) station parameters and velocity models used for earthquake locations; (5) a summary of daily station usage throughout the catalog period; and (6) all HYPOELLIPSE files used to determine the earthquake locations presented in this report.

Alaska↗

USGS2003

Catalog of earthquake hypocenters at Alaskan volcanoes: January 1 through December 31, 2002

The Alaska Volcano Observatory (AVO), a cooperative program of the U.S. Geological Survey, the Geophysical Institute of the University of Alaska Fairbanks, and the Alaska Division of Geological and Geophysical Surveys, has maintained seismic monitoring networks at historically active volcanoes in Alaska since 1988 (Power and others, 1993; Jolly and others, 1996; Jolly and others, 2001; Dixon and others, 2002). The primary objectives of this program are the seismic monitoring of active, potentially hazardous, Alaskan volcanoes and the investigation of seismic processes associated with active volcanism. This catalog presents the basic seismic data and changes in the seismic monitoring program for the period January 1, 2002 through December 31, 2002. Appendix G contains a list of publications pertaining to seismicity of Alaskan volcanoes based on these and previously recorded data. The AVO seismic network was used to monitor twenty-four volcanoes in real time in 2002. These include Mount Wrangell, Mount Spurr, Redoubt Volcano, Iliamna Volcano, Augustine Volcano, Katmai Volcanic Group (Snowy Mountain, Mount Griggs, Mount Katmai, Novarupta, Trident Volcano, Mount Mageik, Mount Martin), Aniakchak Crater, Mount Veniaminof, Pavlof Volcano, Mount Dutton, Isanotski Peaks, Shishaldin Volcano, Fisher Caldera, Westdahl Peak, Akutan Peak, Makushin Volcano, Great Sitkin Volcano, and Kanaga Volcano (Figure 1). Monitoring highlights in 2002 include an earthquake swarm at Great Sitkin Volcano in May-June; an earthquake swarm near Snowy Mountain in July-September; low frequency (1-3 Hz) tremor and long-period events at Mount Veniaminof in September-October and in December; and continuing volcanogenic seismic swarms at Shishaldin Volcano throughout the year. Instrumentation and data acquisition highlights in 2002 were the installation of a subnetwork on Okmok Volcano, the establishment of telemetry for the Mount Veniaminof subnetwork, and the change in the data acquisition system to an EARTHWORM detection system. AVO located 7430 earthquakes during 2002 in the vicinity of the monitored volcanoes. This catalog includes: (1) a description of instruments deployed in the field and their locations; (2) a description of earthquake detection, recording, analysis, and data archival systems; (3) a description of velocity models used for earthquake locations; (4) a summary of earthquakes located in 2002; and (5) an accompanying UNIX tar-file with a summary of earthquake origin times, hypocenters, magnitudes, and location quality statistics; daily station usage statistics; and all HYPOELLIPSE files used to determine the earthquake locations in 2002. The AVO seismic network was used to monitor twenty-four volcanoes in real time in 2002. These include Mount Wrangell, Mount Spurr, Redoubt Volcano, Iliamna Volcano, Augustine Volcano, Katmai Volcanic Group (Snowy Mountain, Mount Griggs, Mount Katmai, Novarupta, Trident Volcano, Mount Mageik, Mount Martin), Aniakchak Crater, Mount Veniaminof, Pavlof Volcano, Mount Dutton, Isanotski Peaks, Shishaldin Volcano, Fisher Caldera, Westdahl Peak, Akutan Peak, Makushin Volcano, Great Sitkin Volcano, and Kanaga Volcano (Figure 1). Monitoring highlights in 2002 include an earthquake swarm at Great Sitkin Volcano in May-June; an earthquake swarm near Snowy Mountain in July-September; low frequency (1-3 Hz) tremor and long-period events at Mount Veniaminof in September-October and in December; and continuing volcanogenic seismic swarms at Shishaldin Volcano throughout the year. Instrumentation and data acquisition highlights in 2002 were the installation of a subnetwork on Okmok Volcano, the establishment of telemetry for the Mount Veniaminof subnetwork, and the change in the data acquisition system to an EARTHWORM detection system. AVO located 7430 earthquakes during 2002 in the vicinity of the monitored volcanoes. This catalog includes: (1) a description of instruments deployed in the field and their locations; (2) a description of earthquake detection, recording, analysis, and data archival systems; (3) a description of velocity models used for earthquake locations; (4) a summary of earthquakes located in 2002; and (5) an accompanying UNIX tar-file with a summary of earthquake origin times, hypocenters, magnitudes, and location quality statistics; daily station usage statistics; and all HYPOELLIPSE files used to determine the earthquake locations in 2002.

Alaska↗

USGS2004

Catalog of earthquake hypocenters at Alaskan volcanoes: January 1 through December 31, 2003

The Alaska Volcano Observatory (AVO), a cooperative program of the U.S. Geological Survey, the Geophysical Institute of the University of Alaska Fairbanks, and the Alaska Division of Geological and Geophysical Surveys, has maintained seismic monitoring networks at historically active volcanoes in Alaska since 1988. The primary objectives of this program are the near real time seismic monitoring of active, potentially hazardous, Alaskan volcanoes and the investigation of seismic processes associated with active volcanism. This catalog presents the calculated earthquake hypocenter and phase arrival data, and changes in the seismic monitoring program for the period January 1 through December 31, 2003. The AVO seismograph network was used to monitor the seismic activity at twenty-seven volcanoes within Alaska in 2003. These include Mount Wrangell, Mount Spurr, Redoubt Volcano, Iliamna Volcano, Augustine Volcano, Katmai volcanic cluster (Snowy Mountain, Mount Griggs, Mount Katmai, Novarupta, Trident Volcano, Mount Mageik, Mount Martin), Aniakchak Crater, Mount Veniaminof, Pavlof Volcano, Mount Dutton, Isanotski Peaks, Shishaldin Volcano, Fisher Caldera, Westdahl Peak, Akutan Peak, Makushin Volcano, Okmok Caldera, Great Sitkin Volcano, Kanaga Volcano, Tanaga Volcano, and Mount Gareloi. Monitoring highlights in 2003 include: continuing elevated seismicity at Mount Veniaminof in January-April (volcanic unrest began in August 2002), volcanogenic seismic swarms at Shishaldin Volcano throughout the year, and low-level tremor at Okmok Caldera throughout the year. Instrumentation and data acquisition highlights in 2003 were the installation of subnetworks on Tanaga and Gareloi Islands, the installation of broadband installations on Akutan Volcano and Okmok Caldera, and the establishment of telemetry for the Okmok Caldera subnetwork. AVO located 3911 earthquakes in 2003. This catalog includes: (1) a description of instruments deployed in the field and their locations; (2) a description of earthquake detection, recording, analysis, and data archival systems; (3) a description of velocity models used for earthquake locations; (4) a summary of earthquakes located in 2003; and (5) an accompanying UNIX tar-file with a summary of earthquake origin times, hypocenters, magnitudes, phase arrival times, and location quality statistics; daily station usage statistics; and all HYPOELLIPSE files used to determine the earthquake locations in 2003.

Alaska↗

USGS2005

Catalog of earthquake hypocenters at Alaskan volcanoes: January 1 through December 31, 2004

The Alaska Volcano Observatory (AVO), a cooperative program of the U.S. Geological Survey, the Geophysical Institute of the University of Alaska Fairbanks, and the Alaska Division of Geological and Geophysical Surveys, has maintained seismic monitoring networks at historically active volcanoes in Alaska since 1988. The primary objectives of the seismic program are the real-time seismic monitoring of active, potentially hazardous, Alaskan volcanoes and the investigation of seismic processes associated with active volcanism. This catalog presents the calculated earthquake hypocenter and phase arrival data, and changes in the seismic monitoring program for the period January 1 through December 31, 2004. These include Mount Wrangell, Mount Spurr, Redoubt Volcano, Iliamna Volcano, Augustine Volcano, Katmai volcanic cluster (Snowy Mountain, Mount Griggs, Mount Katmai, Novarupta, Trident Volcano, Mount Mageik, Mount Martin), Mount Peulik, Aniakchak Crater, Mount Veniaminof, Pavlof Volcano, Mount Dutton, Isanotski Peaks, Shishaldin Volcano, Fisher Caldera, Westdahl Peak, Akutan Peak, Makushin Volcano, Okmok Caldera, Great Sitkin Volcano, Kanaga Volcano, Tanaga Volcano, and Mount Gareloi. Over the past year, formal monitoring of Okmok, Tanaga and Gareloi were announced following an extended period of monitoring to determine the background seismicity at each volcanic center. The seismicity at Mount Peulik was still being studied at the end of 2004 and has yet to be added to the list of monitored volcanoes in the AVO weekly update. AVO located 6928 earthquakes in 2004. Monitoring highlights in 2004 include: (1) an earthquake swarm at Westdahl Peak in January; (2) an increase in seismicity at Mount Spurr starting in February continuing through the end of the year into 2005; (4) low-level tremor, and low-frequency events related to intermittent ash and steam emissions at Mount Veniaminof between April and October; (4) low-level tremor at Shishaldin Volcano between April and October; (5) an earthquake swarm at Akutan in July; and (6) low-level tremor at Okmok Caldera throughout the year (Table 2). Instrumentation and data acquisition highlights in 2004 were the installation of subnetworks on Mount Peulik and Korovin Volcano and the installation of broadband stations to augment the Katmai and Spurr subnetworks. This catalog includes: (1) a description of instruments deployed in the field and their locations; (2) a description of earthquake detection, recording, analysis, and data archival systems; (3) a description of velocity models used for earthquake locations; (4) a summary of earthquakes located in 2004; and (5) an accompanying UNIX tar-file with a summary of earthquake origin times, hypocenters, magnitudes, phase arrival times, and location quality statistics; daily station usage statistics; and all HYPOELLIPSE files used to determine the earthquake locations in 2004.

Alaska↗

USGS2006

Catalog of earthquake hypocenters at Alaskan volcanoes: January 1 through December 31, 2005

The Alaska Volcano Observatory (AVO), a cooperative program of the U.S. Geological Survey, the Geophysical Institute of the University of Alaska Fairbanks, and the Alaska Division of Geological and Geophysical Surveys, has maintained seismic monitoring networks at historically active volcanoes in Alaska since 1988 (Figure 1). The primary objectives of the seismic program are the real-time seismic monitoring of active, potentially hazardous, Alaskan volcanoes and the investigation of seismic processes associated with active volcanism. This catalog presents calculated earthquake hypocenters and seismic phase arrival data, and details changes in the seismic monitoring program for the period January 1 through December 31, 2005. The AVO seismograph network was used to monitor the seismic activity at thirty-two volcanoes within Alaska in 2005 (Figure 1). The network was augmented by two new subnetworks to monitor the Semisopochnoi Island volcanoes and Little Sitkin Volcano. Seismicity at these volcanoes was still being studied at the end of 2005 and has not yet been added to the list of permanently monitored volcanoes in the AVO weekly update. Following an extended period of monitoring to determine the background seismicity at the Mount Peulik, Ukinrek Maars, and Korovin Volcano, formal monitoring of these volcanoes began in 2005. AVO located 9,012 earthquakes in 2005. Monitoring highlights in 2005 include: (1) seismicity at Mount Spurr remaining above background, starting in February 2004, through the end of the year and into 2006; (2) an increase in seismicity at Augustine Volcano starting in May 2005, and continuing through the end of the year into 2006; (3) volcanic tremor and seismicity related to low-level strombolian activity at Mount Veniaminof in January to March and September; and (4) a seismic swarm at Tanaga Volcano in October and November. This catalog includes: (1) descriptions and locations of seismic instrumentation deployed in the field in 2005; (2) a description of earthquake detection, recording, analysis, and data archival systems; (3) a description of seismic velocity models used for earthquake locations; (4) a summary of earthquakes located in 2005; and (5) an accompanying UNIX tar-file with a summary of earthquake origin times, hypocenters, magnitudes, phase arrival times, and location quality statistics; daily station usage statistics; and all HYPOELLIPSE files used to determine the earthquake locations in 2005.

Alaska↗

USGS1996

Catalog of earthquake hypocenters for Augustine, Redoubt, Iliamna, and Mount Spurr volcanoes, Alaska: January 1, 1991 - December 31, 1993

The Alaska Volcano Observatory (AVO), a cooperative program of the U.S. Geological Survey, the Geophysical Institute of the University of Alaska, Fairbanks, and the Alaska Division of Geological and Geophysical Surveys, has maintained a program of seismic monitoring at potentially active volcanoes in the Cook Inlet region since 1988. The principal objectives of this program include the seismic surveillance of the Cook Inlet volcanoes and the investigation of seismic processes associated with active volcanism. This catalog reflects the status and evolution of the seismic monitoring program, and presents the basic seismic data for the time interval January 1, 1991, to December 31, 1993. For an interpretation of these data the reader should refer to several recent articles on volcano related seismicity in the Cook Inlet region (e.g. Jolly and others, 1994; Power and others, 1995; and McNutt and others, 1995). A similar catalog covers the period from October 12, 1989 to December 31, 1991 (Power and others 1993). The AVO seismic monitoring program has undergone significant changes during the catalog period. The changes included 1) new seismic stations placed at Mount Spurr and Redoubt Volcano, resulting in increased earthquake detection capability and improved earthquake locations, 2) the addition of several regional stations to the seismic data acquisition system which improved location quality near the volcano and enhanced our ability to scale eruptions and measure magnitudes of the largest volcanic earthquakes, 3) installation of a new event detection algorithm XDETECT (Rogers, 1993), which offered increased data collection capabilities , 4) modifications to the earthquake location program HYPOELLIPSE (Lahr, 1989) which now allows distinct velocity models and station corrections at each volcanic center, and 5) the addition of seismic stations at Augustine and niamna volcanoes to the data acquisition/location system. The 1992 eruptions at Mount Spurr's Crater Peak vent provided the highlight of the catalog period. The crisis included three sub-plinian eruptions, which occurred on June 27, August 18, and September 16-17, 1992. The three eruptions punctuated a complex seismic sequence which included volcano-tectonic (VT) earthquakes, tremor, and both deep and shallow long period (LP) earthquakes. The seismic sequence began on August 18, 1991, with a small swarm of volcano-tectonic events beneath Crater Peak, and spread throughout the volcanic complex by November of the same year. Elevated levels of seismicity persisted at Mount Spurr beyond the catalog time period.

Alaska↗

USGS2013

Volcanic earthquakes in Alaska's national parks

Alaska’s national parks contain 11 historically active volcanoes (Figure 2), which produce thousands of small earthquakes every year. These earthquakes are voices of the magmatic and geothermal systems within the volcanoes. The Alaska Volcano Observatory (AVO), a joint program of the U.S. Geological Survey, the Geophysical Institute at the University of Alaska Fairbanks, and the Alaska Division of Geological and Geophysical Surveys, monitors volcanic earthquakes year round with networks of seismometers (Figure 4). Data from these networks allow AVO to evaluate the state of magmatic systems and provide warning of volcanic unrest, potential eruptions, and hazards. The key to correctly interpreting earthquakes lies in understanding the physical processes that trigger earthquakes at volcanoes.

Alaska↗

USGS1999

Permit application and approval chronology for a small airgun survey offshore southern California, June 1999

Offshore geophysical surveys are subject to increased restrictions resulting from new or revised Federal legislation and increased authority of State agencies that deal with environmental issues. This report reviews the process followed by the U.S. Geological Survey to obtain necessary approvals for a marine geophysical survey conducted in June, 1999, offshore Southern California. Discussions and negotiations between the USGS, National Marine Fisheries Service, the California Coastal Commission, the California State Lands Commission, and various other interested parties during six months prior to the survey are documented. A suggested timeframe that should be followed for obtaining the approvals and permits for future work offshore California is based on the outcome of the permitting process for the 1999 cruise, as well as continuing dialog with representatives of the Federal and State entities involved.

California↗

USGS2026

Hydrogeologic conceptualization of the Arroyos subarea and Northeast Air Force Research Laboratory subarea of the Air Force Research Laboratory, Edwards Air Force Base, Antelope Valley, California, 2017–21

Research and testing within the Air Force Research Laboratory at Edwards Air Force Base in the southwestern Mojave Desert has been conducted since the 1950s. This testing requires large quantities of groundwater for cooling and operations involving hazardous constituents that have entered the groundwater. To better understand the potential movement of contaminants through the groundwater system, the U.S. Geological Survey entered into a cooperative agreement with the U.S. Air Force Civil Engineer Center with the purpose of (1) gaining a more detailed understanding of the hydraulic connection between the unconsolidated basin-fill sediment and the underlying weathered and crystalline bedrock and (2) investigating faults and their potential effect on groundwater flow. This study was specific to the Arroyos subarea and Northeast Air Force Research Laboratory subarea of the Air Force Research Laboratory. The refined hydrogeologic characterization was derived by evaluating surface geologic maps, a regional gravity model, new subsurface geophysical surveys, lithology data from boreholes, and groundwater-level data. Refinement of the hydrogeologic characterization of the study area involved developing a map of basin-fill sediment thickness, estimating the geometry and depth to bedrock, determining the presence of weathered bedrock material, and identifying the location of faults and subsurface structures. The thickness of basin-fill sediment was derived from a regional gravity model. Basin-fill sediment ranges from less than 20 feet (ft) thick to about 150 ft thick and increases substantially toward a deep structural basin in the northwestern part of the study area. The top of bedrock estimated from the new surface geophysical surveys is generally deeper than the top of bedrock from the regional gravity model. These differences in interpreted bedrock tops indicate that there may be a zone of weathered bedrock in the subsurface, overlying crystalline bedrock. Additional subsurface data evaluating the geometry and thickness of weathered bedrock are necessary for a comprehensive evaluation of weathered bedrock in the study area. Previously unmapped extensions of the Leuhman Fault, Spring Fault Zone, and Boron Gate Fault were identified in the new surface geophysical surveys. Evaluation of groundwater flow between bedrock and basin-fill sediment, and the effects of faults on groundwater flow, was done using groundwater-level data from 2020. The groundwater table was in crystalline bedrock throughout most of the Arroyos and Northeast Air Force Research Laboratory subareas, with a few exceptions where it was in basin-fill sediment and weathered bedrock. Basin-fill sediment, and likely weathered bedrock, was partially saturated in parts of the study area where basin-fill sediment was as thick as 150 ft. Weathered bedrock material may be present near the Spring Fault Zone, and if so, was likely saturated in 2020. The groundwater-level data near and within Spring Fault Zone indicate that the Spring Fault Zone acts as a vertical-along-strike conduit for, and as an across-strike impediment to, groundwater flow. In addition, steep groundwater-level gradients in the southeastern part of the study area indicate that a subsurface structure affecting groundwater flow could be related to the Leuhman Fault. Sufficient groundwater-level data were not available to conclusively determine if the Arroyos, Rich, and Boron Gate Faults, and their inferred extensions from the geophysical surveys, affect the movement or direction of groundwater flow.

California↗