Geology topics
E. L. Harp
Publications and source records attributed to E. L. Harp.
Simulation of rockfalls triggered by earthquakes
A computer program to simulate the downslope movement of boulders in rolling or bouncing modes has been developed and applied to actual rockfalls triggered by the Mammoth Lakes, California, earthquake sequence in 1980 and the Central Idaho earthquake in 1983. In order to reproduce a movement mode where bouncing predominated, we introduced an artificial unevenness to the slope surface by adding a small random number to the interpolated value of the mid-points between the adjacent surveyed points. Three hundred simulations were computed for each site by changing the random number series, which determined distances and bouncing intervals. The movement of the boulders was, in general, rather erratic depending on the random numbers employed, and the results could not be seen as deterministic but stochastic. The closest agreement between calculated and actual movements was obtained at the site with the most detailed and accurate topographic measurements. ?? 1990 Springer-Verlag.
Real-time landslide warning during heavy rainfall
A real-time system for issuing warnings of landslides during major storms is being developed for the San Francisco Bay region, California. The system is based on empirical and theoretical relations between rainfall and landslide initiation, geologic determination of areas susceptible to landslides, real-time monitoring of a regional network of telemetering rain gages, and National Weather Service precipitation forecasts. This system was used to issue warnings during the storms of 12 to 21 February 1986, which produced 800 millimeters of rainfall in the region. Although analysis after the storms suggests that modifications and additional developments are needed, the system successfully predicted the times of major landslide events. It could be used as a prototype for systems in other landslide-prone regions.
Seismically induced landslides: current research by the US Geological Survey.
We have produced a regional seismic slope-stability map and a probabilistic prediction of landslide distribution from a postulated earthquake. For liquefaction-induced landslides, in situ measurements of seismically induced pore-water pressures have been used to establish an elastic model of pore pressure generation. -from Authors
Map showing slope stability during earthquakes in San Mateo County, California
No abstract available.
Map showing ground failures from the Greenville/Mount Diablo earthquake sequence of January 1980, Northern California
The Greenville/Mt. Diablo earthquake sequence of January 24-26, 1980, was composed of Small and moderate earthquakes; the two largest shocks, on January 24 and 26, were of magnitudes (M) 5.5 and 5.6, respectively (Bolt and others, 1981). A 5.5 event is at the lower end of the range of earthquake magnitudes which cause observable ground failure (Youd and Perkins, 1978; Keefer, 1984). While none of the slope failures produced by the Greenville/Mt. Diablo earthquake sequence (GMDES) was larger than a few tens of cubic meters, they were both widespread in area (see map) and rich in variety, and thus have much to teach us about seismically induced slope failures in the San Francisco Bay area. This map depicts the location, type, and relative size of the ground failures observed during our reconnaissance, which began at 2:30 pm PST on January 24 and continued on January 25, 26, and 28 and February 6. Our observations were generally limited to that part of the Livermore region that is accessible by state and county roads. Information about the individual ground failures may be obtained from the map and the brief descriptions in table 1. The following text is a general discussion of the distribution and the mechanisms of the ground failures, followed by a discussion of the effects of wet winter conditions and of topographic amplification on the distribution and mechanisms of slope failure, and it concludes with a description of our (unsuccessful) efforts to locate any ground failures due to liquefaction. The discussion is intended not only to describe the GMDES slope failures but also to place them into the larger general context of seismically induced slope failures.
Subsurface investigation of liquefaction, Imperial Valley earthquake, California, October 15, 1979
Explore the source record for details and available documents.
A comparison of artifical and natural slope failures: the Santa Barbara earthquake of August 13, 1978.
The earthquake triggered rockfalls and rockslides from steep road cuts and coastal cliffs. The landslide reconnaissance survey which was carried out is described, with separate comments on each landslide site recorded. The general regional slope response to the earthquake is briefly considered. -R. House