Tilt Precursors before Earthquakes on the San Andreas Fault, California

An array of 14 biaxial shallow-borehole tiltmeters (at 1O(-7) radian sensitivity) has been installed along 85 kilometers of the San Andreas fault during the past year. Earthquake-related changes in tilt have been simultaneously observed on up to four independent instruments. At earthquake distances greater than 10 earthquake source dimensions, there are few clear indications of tilt change. For the four instruments with the longest records (> 10 months), 26 earthquakes have occurred since July 1973 with at least one instrument closer than 10 source dimensions and 8 earthquakes with more than one instrument within that distance. Precursors in tilt direction have been observed before more than 10 earthquakes or groups of earthquakes, and no similar effect has yet been seen without the occurrence of an earthquake.     

Paleoseismic Evidence for Recurrence of Earthquakes near Charleston, South Carolina

A destructive earthquake that occurred in 1886 near Charleston, South Carolina, was associated with widespread liquefaction of shallow sand structures and their extravasation to the surface. Several seismically induced paleoliquefaction structures preserved within the shallow sediments in the meizoseismal area of the 1886 event were identified. Field evidence and radiocarbon dates suggest that at least two earthquakes of magnitudes greater than 6.2 preceded the 1886 event in the past 3000 to 3700 years. The evidence yielded an initial estimate of about 1500 to 1800 years for the maximum recurrence of destructive, intraplate earthquakes in the Charleston region.     

Lithologic Control of the Depth of Earthquakes in Southern California

The depth distribution of southern California earthquakes indicates that areas underlain by schist basement rocks have a shallower (4 to 10 kilometers) maximum depth of earthquakes than do areas with other types of basement rocks. The predominant minerals in the schists become plastic at lower temperatures, and thus at shallower depths, than the minerals in the other basement rocks. The lateral variations in lithology will control the depth extent (and thus the magnitudes) of potential future earthquakes; these depths can be determined from the depth of the current background seismicity.     

High Rates of Vertical Crustal Movement near Ventura, California

Fission track, radiometric, and paleomagnetic age determinations in marine sedimentary rocks of the Ventura Basin make it possible to estimate the vertical components of displacement rates for the last 2 million years. The basin subsided at rates up to 9.5 +/- 2.5 millimeters per year until about 0.6 million years ago, when subsidence virtually ceased. Since then, the northern margin of the basin has been rising at an average rate of 10 +/- 2 millimeters per year, about the same rate as that based on the geodetic record north and west of Ventura since 1960 but considerably lower than the rate along the San Andreas fault at Palmdale since 1960.     

Earthquake Swarm Along the San Andreas Fault near Palmdale, Southern California, 1976 to 1977

Between November 1976 and November 1977 a swarm of small earthquakes (local magnitude 相似文献   

Earthquakes and the Earth's Wobble

Observational evidence is presented in support of the hypothesis that large earthquakes excite the earth's natural wobble and produce the observed secular polar shift. Previous theoretical calculations based on elasticity theory and earthquake statistics had predicted a significant effect. There appear to be some premonitory signs of large earthquakes in the pole path.     

Earthquakes, active faults, and geothermal areas in the imperial valley, california

A dense seismograph network in the Imperial Valley recorded a series of earthquake swarms along the Imperial and Brawley faults and a diffuse pattern of earthquakes along the San Jacinto fault. Two known geothermal areas are closely associated with these earthquake swarms. This seismicity pattern demonstrates that seismic slip is occurring along both the Imperial-Brawley and San Jacinto fault systems.     

Earthquakes and the rotation of the Earth

A correlation exists between long-term variations in the length of the day, Chandler wobble amplitudes, and global seismic activity. These variations may be partially due to climatic changes and ultimately to explosive volcanic activity.     

California current eddy formation: ship, air, and satellite results

Until recently, quantitative measurements of the circulation of the California Current were limited to hydrographic determinations [See figure in the PDF file] of temperature and salinity. This information is now being augmented by satellite data. Clouds permitting, satellite scanner systems can locate major ocean frontal boundaries if they are associated with even quite weak horizontal sea-surface temperature gradients. The satellite data are most usefully interpreted in a region such as that encompassing the California Current, where the surface and main thermocline temperature distributions bear some relation to each other. In such a region, it is possible to make interpretations of circulation based on satellite-derived sea-surface temperature patterns. The correctness of these interpretations depends heavily on the availability of historical and present-day subsurface data, collected by conventional methods from ships and aircraft. Satellite infrared scanners, in addition to providing information on circulation with vastly increased spatial resolution, have the potential (with cooperative weather) for providing increased time resolution. These improvements in resolution have permitted us to see that much of the spatial variation in the California Current takes place along welldefined fronts and to observe the evolution of one particular meander.     

The killing fields: Science and politics at Berkeley, California, USA

Over the past several decades, a group of scholars at the Berkeley campus of the University of California have frequently challenged many of the dominant themes of contemporary agricultural research. In their work, they have organized curricula questioning the assumptions of conventional agriculture and its sciences while encouraging the development of alternative agricultural practices based on principles of ecology. Their collective critique has stimulated an intellectual climate calling forth a scrutiny of the university's role in the production of knowledge and the social consequences of its works. The result of this intellectual project has been a group that has also largely challenged the dominant themes of the modern university. In place of a setting where ideas are a passive currency, the modern university is a place where knowledge and power are manifest in a dialectic that is revealed not simply by the production of knowledge, but its destruction as well. It is in this context that the recent history of a group of scholars at the University of California provides a striking testimony concerning the disturbing character of science in the modern university. The ecological and social dimensions of “killing fields” that captures the contemporary hazards of food and fiber production in California is also reflected in the gradual demise of a group of researchers at Berkeley who have endeavored to provide an alternative vision of agriculture.     

Peruvian desert mice: water independence, competition, and breeding cycle near the Equator

The native mouse of the Peruvian coastal desert, near latitude 6 degrees S, can survive on dry seed without drinking water, it bears young in winter, and it burrows in sand. House mice (which abound in other adjoining deserts) also tolerate dehydration, and in some areas may displace the native mice.