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Margaret G. Hopper

Publications and source records attributed to Margaret G. Hopper.

11 recordsLinked to original sources
USGS2017

Aftershocks, earthquake effects, and the location of the large 14 December 1872 earthquake near Entiat, central Washington

Reported aftershock durations, earthquake effects, and other observations from the large 14 December 1872 earthquake in central Washington are consistent with an epicenter near Entiat, Washington. Aftershocks were reported for more than 3 months only near Entiat. Modal intensity data described in this article are consistent with an Entiat area epicenter, where the largest modified Mercalli intensities, VIII, were assigned between Lake Chelan and Wenatchee. Although ground failures and water effects were widespread, there is a concentration of these features along the Columbia River and its tributaries in the Entiat area. Assuming linear ray paths, misfits from 23 reports of the directions of horizontal shaking have a local minima at Entiat, assuming the reports are describing surface waves, but the region having comparable misfit is large. Broadband seismograms recorded for comparable ray paths provide insight into the reasons why possible S – P times estimated from felt reports at two locations are several seconds too small to be consistent with an Entiat area epicenter.

Washington↗
USGS2002

Intensity distribution and isoseismal maps for the Nisqually, Washington, earthquake of 28 February 2001

We present isoseismal maps, macroseismic intensities, and community summaries of damage for the MW=6.8 Nisqually, Washington, earthquake of 28 February, 2001. For many communities, two types of macroseismic intensity are assigned, the traditional U.S. Geological Survey Modified Mercalli Intensities (USGS MMI) and a type of intensity newly introduced with this paper, the USGS Reviewed Community Internet Intensity (RCII). For most communities, the RCII is a reviewed version of the Community Internet Intensity (CII) of Wald and others (1999). For some communities, RCII is assigned from such non-CII sources as press reports, engineering reports, and field reconnaissance observations. We summarize differences between procedures used to assign RCII and USGS MMI, and we show that the two types of intensity are nonetheless very similar for the Nisqually earthquake. We do not see evidence for systematic differences between RCII and USGS MMI that would approach one intensity unit, at any level of shaking, but we document a tendency for the RCII to be slightly lower than MMI in regions of low intensity and slightly higher than MMI in regions of high intensity. The highest RCII calculated for the Nisqually earthquake is 7.6, calculated for zip code 98134, which includes the ?south of downtown? (Sodo) area of Seattle and Harbor Island. By comparison, we assigned a traditional USGS MMI 8 to the Sodo area of Seattle. In all, RCII of 6.5 and higher were assigned to 58 zip-code regions. At the lowest intensities, the Nisqually earthquake was felt over an area of approximately 350,000 square km (approximately 135,000 square miles) in Washington, Oregon, Idaho, Montana, and southern British Columbia, Canada. On the basis of macroseismic effects, we infer that shaking in the southern Puget Sound region was somewhat less for the 2001 Nisqually earthquake than for the Puget Sound earthquake of April 13, 1949, which had nearly the same hypocenter and magnitude. Allowing for differences in hypocenter, shaking in the 2001 earthquake was very similar to that produced by the Puget Sound earthquake of April 25, 1965. First-person accounts of the effects of the 2001 earthquake on individual households are given for some communities.

Open-File Report↗
USGS1996

National Seismic-Hazard Maps: Documentation June 1996

In this release of hazard maps we present numerous maps and data with varying parameters. The computations for these maps and data used 50 year return periods on firm rock at 760 m/sec. All of the maps were prepared by combining hazard derived from spatially- smoothed historic seismicity with hazard from fault-specific sources. For more information please read our full documentation. Although these maps have been used by the U.S. Geological Survey, no warranty, expressed or implied is made by the USGS as to the accuracy of the maps and related material nor shall the fact of distribution constitute any such warranty, and no responsibility is assumed by the USGS in connection therewith.

Open-File Report↗
USGS1983

Estimation of earthquake effects associated with a great earthquake in the New Madrid seismic zone

Estimates have been made of the effects of a large Ms = 8.6, Io = XI earthquake hypothesed to occur anywhere in the New Madrid seismic zone. The estimates are based on the distributions of intensities associated with the earthquakes of 1811-12, 1843 and 1895 although the effects of other historical shocks are also considered. The resulting composite type intensity map for a maximum intensity XI is believed to represent the upper level of shaking likely to occur. Specific intensity maps have been developed for six cities near the epicentral region taking into account the most likely distribution of site response in each city. Intensities found are: IX for Carbondale, IL; VIII and IX for Evansville, IN; VI and VIII for Little Rock, AR; IX and X for Memphis, TN; VIII, IX, and X for Paducah, KY; and VIII and X for Poplar Bluff, MO. On a regional scale, intensities are found to attenuate from the New Madrid seismic zone most rapidly to the west and southwest sides of the zone, most slowly to the northwest along the Mississippi River, on the northeast along the Ohio River, and on the southeast toward Georgia and South Carolina. Intensities attenuate toward the north, east, and south in a more normal fashion. Known liquefaction effects are documented but much more research is needed to define the liquefaction potential.

Open-File Report↗
USGS1980

Field survey of intensity for the earthquake of July 27, 1980, Sharpsburg, Kentucky

The magnitude 5.2 (mb) northern Kentucky earthquake of July 27, 1980, at 18:52:21.8 UTC, located at 38.17N, 83.91W with a depth of 8 km (as determined by the National Earthquake Information Service), was particularly notable for the widespread damage it did, especially to older chimneys. Investigators from several different organizations were in the field shortly after the earthquake recording aftershocks and checking intensities. The data from postal intensity surveys and field personnel are still coming in, and it will be some time before it is all evaluated and analyzed. This preliminary list of the results of our own field investigations is being produced now in order that the information we gathered may be combined with that of other researchers for analysis. Our investigation, conducted from July 28 to August 3, was designed to delineate the areal distribution of the intensities and to document the amount and type of damage in the epicentral region. Tentative intensities have been assigned to these reports and they have been plotted in figure 1. However, as more information becomes available from other investigators, some of these values may be changed and other locations may be added. Therefore no attempt has been made to contour the data. A maximum Modified Mercalli intensity of VII was assigned to Maysville, Ky., approximately 50 km north of the epicenter, based on the concentrated chimney and other types of building damage there. Elsewhere, similar but scattered chimney damage has been assigned intensity VI.

Kentucky↗