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More about Earthquake Seismology at UTIG |
Organization Of These Pages
These pages display information about, images of, and seismograms recorded by the Hockley Seismic Station administrated by the University Of Texas Institute For Geophysics. The Hockley Seismic Station is a state of the art broad band seismometer, and is a member of the IRIS Global Seismic Network and the United States National Seismic Network. Further down this page you will find general information about the Hockley Seismic Station. Separate pages contain information on:
Personnel - who's the boss, and who to contact
Tour - you can take a virtual tour of the facility
Seismograms - you can view HKT seismograms at the TexSeis site
You can jump to any of these topics at any time using the anchor bar at the top of the page, or you can jump to any of the other earthquake pages by clicking icons at the very top of the page. Some of the information in this page is repeated in subsequent pages.
About The Hockley Seismic Station During the week of July 17, 1995, a team from the Albuquerque Seismic Lab (ASL) operated jointly by the United States Geological Survey (USGS) and the Incorporated Research Institutions for Seismology (IRIS) assisted by several staff members from the University Of Texas Institute For Geophysics (UTIG) installed a state of the art broad-band seismometer at Hockley, Texas. The station at Hockley is located about 100 miles east of Austin, just north of the Houston suburbs, and about ½ kilometer below ground. The new Streckeisen sensors and Quanterra digital data aquisition system replace an older analog Teledyne Geotech S-13 short period seismometer installed in 1973 at the same location.
The University of Texas Institute for Geophysics is responsible for operating and maintaining the seismic station, as well as providing data aquired from the system to the Global Seismic Network (GSN) operated by IRIS. The Hockley seismic station is the eighth University Network site selected by the IRIS GSN program. In addition, the Hockley station is a cooperating member of the United States National Seismic Network (USNSN) operated by the USGS. The new station became operational July 21, 1995, and has been given the station code HKT for use with GSN and USNSN databases.
Station HKT is the first IRIS/GSN station in Texas; the nearest regional broad-band stations are located in Albuquerque, New Mexico, Tuscon, Arizona, and in Mexico City. The Hockley station helps fill the large gap in station coverage throughout the mid-west and along the Gulf coast states (Figure 2) [For details on the USNSN, see NEIC USNSN web page, http://wwwneic.cr.usgs.gov/neis/usnsn/usnsn_home.html] and provides crucial information to the national scientific comunity.
The addition of station HKT aids regional and global seismological studies. For example, the location of the Hockley station is ideal for studying the earth's crust and uppermantle structure beneath Texas, the Gulf of Mexico, and Northern Mexico (Figure 3). Such research projects have not been impossible without this modern broad-band seismic station. The addition of station HKT will contribute to studies of earthquake sources and structure of northwestern North America, the middle America Trench, and the South American Trench, as well as the structure of the deep earth.
Description Of The Hockley Seismometer The data aquisition system for the Hockley seismometer is located in an excavated chamber within an active salt mine owned by United Salt Corporation (Figure 4). The chamber lies approximately 470 meters below the surface within a large salt dome. Locating the instrument within a salt dome reduces the noise from human activity that generally affects instruments on the surface. The seismometer consists of three Streckeisen STS-1 sensors oriented vertically, north-south, and east-west, mounted on a concrete slab, and kept in evacuated containers. The seismic sensors feed a signal directly to the Q680 data aquisition (DA) unit manufactured by Quanterra Corporation, which handles all aquisition procedures (Figure 5). The heart of the DA is a Motorola VME-147s computer running OS-9 system software.
A fiber optic cable running up a bore hole connects the DA to the VSAT communications hardware, a Global Positioning System (GPS) clock, and a dial-up modem on the surface. The DA regularly synchronizes its clock to Coordinated Universal Time (UTC) with GPS satellites. Using the VSAT link, the data stream travels to the National Earthquake Information Center (NEIC) in Golden, Colorado, where the USNSN monitors national earthquake activity. The NEIC then transmits the seismometer data via satellite to the data processing (DP) system located in the main computer room at UTIG in Austin. The Hockley station hardware arrangement is known as a separate or split system since the DA and DP are not at the same location.
The DP consists of a Motorola VME-147S computer running OS-9 system software. A 300 Mbyte disk serves as the data buffer area, holding about 1.5 weeks of broad-band high gain data. Hockley's seismic data is periodically written as Standard for the Exchange of Earthquake Data (SEED) Field Volumes to QIC-150 quarter inch tape drives using DC-6150 cartridges. The tapes are changed at about two week intervals, and then sent to the IRIS Data Collection Center at ASL for further processing and ultimately archival at the IRIS Data Management Center in Seattle, Washington. A Graphon GO-250 terminal provides direct control of the DP and display of data. A dot-matrix printer is also connected to the DP and provides a hard copy of the system logs. Quanterra Ultrashear software runs on both the DA and DP, providing all data aquisition, processing, recording, and retrieval utilities. SEED broadband, long period, very long period, and ultra long period high gain channels are recorded. In addition, a very long period mass position channel is also aquired. Channels AFP, AFV, VKI, VK1, VE1, and UE1 are used to administer the seismometer and monitor cabinet temperature and electronics, and are generally not of scientific interest.
About Our Icon
The Hockley Seismic Station logo is formed from four paths taken by earthquake waves as they travel through a cross section of the Earth. These seismic waves traverse six of the Earth's major structural/mechanical boundaries.
Acknowledgements
The Hockley Seismic Station is a cooperative project between the University Of Texas, IRIS, USNSN, and the United Salt Corporation. Daily maintenance and monitoring is handled by University of Texas Institute For Geophysics staff. The UTIG staff would like to thank Dave Ketchum (USGS USNSN) and Don Anderson (IRIS/USGS DCC) for their considerable technical support. From the installation of HKT onward the assistance of United Salt mine personnel has been invaluable.
