Publications

Observations of 167 small, shallow landslides spanning a 22-year period on extensively logged slopes of Quaternary terraces in the lower Skagit and Baker Valleys, Washington, shows that there is a relationship between the common slope failures in this area and the slope angle, stratigraphy, and logging practices. Landslide frequency increases upvalley, as do mean annual precipitation and...

A 13,000 km2 area of the southern New England Continental Shelf which is covered by anomalously fine-grained sediment has been surveyed by means of high-resolution, seismic-reflection and side-scan sonar techniques to map its morphology and structure, and a near-bottom instrument system contributed to understanding present activity of the deposit. Seismic-reflection profiles show that...

Long linear tension cracks associated with declining groundwater levels at four sites in subsiding areas in south-central Arizona, Fremont Valley, California, and Las Vegas Valley, Nevada, occur near points of maximum convex-upward curvature in subsidence profiles oriented perpendicular to the cracks. Profiles are based on repeated precise vertical control surveys of lines of closely...

The preliminary geomagnetic data included here is made available to scientific personnel and organizations, as part of a cooperative effort and on a data exchange basis because of the early need by some users. To avoid delay, all of the data is copied from original forms processed at the observatory; therefore it should be regarded as preliminary.

The morphology and distribution of ridges and scarps on Mars in the ± 30° latitude belt were investigated. Two distinct types of ridges were recognized. The first is long and linear, resembling mare ridges on the Moon; it occurs mostly in plains areas. The other is composed of short, anastomosing segments and occurs mostly in ancient cratered terrain and intervening plateaus. Where...

The icy crust of Ganymede comprises bright and dark areas. Investigation of Voyager 1 and 2 images has shown that bright terrain is grooved and separates dark polygons of cratered terrain. The grooved terrain contains alternating ridges and grooves in straight and curvilinear sets, which are locally interrupted by smooth patches and swaths. Cratered terrain, where 'it occurs in small...

No abstract available.

The mechanical properties of elemental sulfur are such that the upper crust of Io cannot be primarily sulfur. For heat flows in the range 100–1000 ergs cm−2, sec−1, sulfur becomes ductile within several hundred meters of the surface and would prevent the formation of calderas with depths greater than this. However, the one caldera for which precise depth data are available is 2 km deep...

Prism-shaped single crystals of MgO(Al2O3)n spinel (n 1.1) have been compressed to significant plastic strain at a temperature of 400°C (∼0·28 TM) in controlled experiments under a superimposed hydrostatic pressure of 1·4 GPa. Compression of crystals approximately parallel to , and resulted in simple yield behaviour at axial stress differences of 1940, 3720, and 4300 MPa respectively...

No abstract available.

No abstract available.

Studies conducted in the San Francisco Bay Region (Gibbs, Fumal and Borcherdt, 1980) have shown that average shear-wave velocity can be readily tied to quantitative estimates of ground motion such as ground amplification and earthquake intensity. Furthermore, when certain physical properties of the geologic materials such as texture, hardness and fracture spacing are observed during...