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Landslides caused by the Klamath Falls, Oregon, earthquakes of September 20, 1993 Landslides caused by the Klamath Falls, Oregon, earthquakes of September 20, 1993

The Klamath Falls earthquakes caused landslides throughout an area of about 420 sq km and as far as about 29 km from the epicenter, a distribution that is typical for magnitude 6 earthquakes (see graphs on following pages). Most of the landslides were rock falls or shallow, highly disrupted rock slides from roadcuts, quarries, and steep bluff faces. Such landslides are also among the...
Authors
D. K. Keefer, R. L. Schuster

A rainfall intensity-duration threshold for landslides in a humid- tropical environment, Puerto Rico A rainfall intensity-duration threshold for landslides in a humid- tropical environment, Puerto Rico

Landslides are triggered by factors such as heavy rainfall, seismic activity, and construction on hillslopes. The leading cause of landslides in Puerto Rico is intense and/or prolonged rainfall. A rainfall threshold for rainfall-triggered landsliding is delimited by 256 storms that occurred between 1959 and 1991 in the central mountains of Puerto Rico, where mean annual rainfall is close...
Authors
M. C. Larsen, A. Simon

Landslides triggered by Hurricane Hugo in eastern Puerto Rico, September 1989 Landslides triggered by Hurricane Hugo in eastern Puerto Rico, September 1989

On the morning of September 18, 1989, a category-four hurricane struck eastern Puerto Rico with a sustained wind speed in excess of 46 m/s. The 24-h rainfall accumulation from the hurricane ranged from 100 to 339 mm. Average rainfall intensities ranging from 34 to 39 mm/h were calculated for 4 and 6 h periods, respectively, at a rain gage equipped with satellite telemetry, and at an...
Authors
Matthew C. Larsen, Angel J. Torres-Sanchez

The National Landslide Information Center; data to reduce landslide damage The National Landslide Information Center; data to reduce landslide damage

Almost every day a landslide disasters occurs somewhere in the world. Nearly any time there is heavy rainfall, an earthquake, a volcanic eruption, strong wave action on a shoreline, or some ill-considered alteration of sloping land by humans, landslides occur. In a world of persistent and increasing construction on and occupation of hillslopes, canyons, and coastal bluffs, landslides are...
Authors
W. M. Brown

Analysis of geomagnetic secular variation during 1980-1985 and 1985- 1990, and geomagnetic models proposed for the 1991 revision of the International Geomagnetic Reference Field Analysis of geomagnetic secular variation during 1980-1985 and 1985- 1990, and geomagnetic models proposed for the 1991 revision of the International Geomagnetic Reference Field

The secular variation of the main geomagnetic field during the periods 1980-1985 and 1985-1990 was analyzed in terms of spherical harmonics up to the eighth degree and order. Data from worldwide magnetic observatories and the Navy's Project MAGNET aerial surveys were used. The resulting pair of secular-variation models was used to update the Definitive Geomagnetic Reference Field (DGRF)...
Authors
N.W. Peddie

Hazards of geomagnetic storms Hazards of geomagnetic storms

Geomagnetic storms are large and sometimes rapid fluctuations in the Earth's magnetic field that are related to disturbances on the Sun's surface. Although it is not widely recognized, these transient magnetic disturbances can be a significant hazard to people and property. Many of us know that the intensity of the auroral lights increases during magnetic storms, but few people realize...
Authors
D.C. Herzog

Evaluation of models proposed for the 1991 revision of the International Geomagnetic Reference Field Evaluation of models proposed for the 1991 revision of the International Geomagnetic Reference Field

The 1991 revision of the International Geomagnetic Reference Field (IGRF) comprises a definitive main-field model for 1985.0, amain-field model for 1990.0, and a forecast secular-variation model for the period 1990-1995. The five 1985.0 main-field models and five 1990.0 main-field models that were proposed have been evaluated by comparing them with one another, with magnetic observatory...
Authors
N.W. Peddie
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