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This report lists the main activities of the Geoscience Committee and geoscience
accomplishments by various organizations and individuals in 1999 in Nevada.
The three main activities of the committee were:
(1) Revision of the "Guidelines for Evaluating Potential Surface Fault Rupture/Land Subsidence Hazards in Nevada" was completed, and placed on the NESC and NBMG Web sites.
(2) The "Guidelines for Evaluating Liquefaction Hazards in Nevada" was completed, placed on the NESC Web site on the NBMG Web (www.nbmg.unr.edu/nesc/index.html), and recommended for approval by the NESC at the February 18, 2000 meeting. The committee is especially grateful to: Jim Werle and Mike Klein of Converse, who prepared the initial draft, to Gary Norris and Raj Siddharthan of UNR, who chaired the Liquefaction Subcommittee, and Barbara Luke of UNLV, who organized the southern Nevada efforts.
(3) A subcommittee reviewed the IBC 2000 document and developed new recommendations for appropriate hazard maps in Nevada. A consensus among the geoscience and engineering communities on appropriate levels of seismic hazard and seismic design was developed, particularly in the Western Nevada region.
Related Nevada activities included the following:
The Nevada Bureau of Mines and Geology and the Seismological Laboratory
continued to conduct research and monitoring programs designed to reduce
earthquake losses in Nevada. These programs were funded from various sources
including the National Earthquake Hazard Reduction Program, the U.S. Department
of Energy Yucca Mountain Program, and the U.S. Geological Survey STATEMAP
Program.
The Nevada Bureau of Mines and Geology (NBMG) in 1999 published an updated
earthquake epicenter map for Nevada, NBMG Map 119, which was co-authored by
Diane M. dePolo of the Nevada Seismological Laboratory and Craig dePolo of
NBMG, titled "Earthquakes in Nevada, 1952-1998". The 1:1,000,000-scale map
plotted on a shaded relief base map, with an inset map that shows major
earthquakes in Nevada and surrounding areas, a table of earthquake data for
earthquakes of M> 5.5, and a text. This map will be a major resource for future
earthquake hazard studies and planning in Nevada.
In 1999 NBMG also published twenty new geologic maps, mostly at 1:24,000-scale.
These geologic maps form the basis for hazard studies that are useful in land-use
planning and risk mitigation. Any of the maps delineate areas that, upon further
analysis, may prove to be hazardous in terms of ground shaking or liquefaction.
They include: 4 in the Las Vegas/Pahrump region, 3 in the Reno/Carson City area,
and 13 distributed through the state in rural areas.
During 1999, staff members from the Department of Geological Sciences (UNR) and the Nevada Seismological Laboratory continued studies of Quaternary and Holocene paleoseismic faults, large landslides, and historic earthquakes (including the October 30, 1998 earthquake) in the Lake Tahoe region.
UNLV received a special FEMA grant to fund the up-grading of their seismographic station.
The Nevada Seismological Laboratory (NSL) continued studies of earthquake epicenters, focal mechanisms, aftershocks of specific fault in Nevada (including the Lake Tahoe area, the Scotty’s Junction, Nevada area, and Double Springs, Nevada). The relationship between moderate and major faults is a particular focus at this time. The strong ground motion response in Las Vegas Valley from the Scotty’s Junction and Hector Mine, California earthquakes is the subject of ongoing research. Probabilistic seismic hazard analyses are also being improved.
During 1999, NSL investigated the potential tsunami from a large earthquake bounding Lake Tahoe. Potential wave heights around the lake margins range up to 10 meters, so a simple recommendation to anyone living in the vicinity of the lake is to immediately seek high ground (at least 10 meters above lake level) if they feel a severe earthquake.
NSL received state funding to supplement the strong motion network to achieve a thorough understanding of strong ground motion in the urban areas of Nevada. Five strong motion instruments were installed in Reno/Sparks, Carson City areas, and three instruments are to be installed in Las Vegas.
NSL is in the process of adapting a new operating system that will improve its real-time capabilities to locate and report earthquakes (Antelope software).
NSL expanded its analog seismic network in western Nevada and improved locations especially on the margins of the northern and southern networks.
Other activities included:
NESC council members and participants in the council activities, faculty at UNR and UNLV, staff of the Nevada Bureau of Mines and Geology, and Nevada Seismological Laboratory have continued to interact with the media, particularly after earthquakes were felt in various parts of the state. Also several interviews were made on TV stations, help was provided to journalists, and talks were presented at service and other organizations.