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Engineering topics

Beavan, R. J.

Publications and source records attributed to Beavan, R. J..

Eruptions of Pavlof Volcano and their possible modulation by ocean load and tectonic stresses

Data pertaining to the basic features (such as the volume of erupted materials and the rate of mass ejection) of the eruptions of the Pavlof Volcano, Alaska, and the accompanying seismicity were related to other geophysical data, including atmospheric pressure, earth and ocean-load tides, long-period sea level, and ground tilt. A significant correlation was found between the eruptions of the volcano and yearly nontidal variations in sea level, that possibly resulted from ocean loading; volume changes beneath the volcano due to ocean loading were calculated to be from 0.02 to 2 times eruption volumes. It is suggested that the volcano acts as a long-period volume strain meter, with lava being preferentially erupted when strain beneath the volcano is compressive. No eruptions occurred during the period of 1978-1980, when tilt, seismic data, and sea level data indicated that a deep aseismic slip may have occurred. Models of this aseismic event predict a volume increase beneath the volcano that might have compensated strain from magma injection.

Mcnutt, S. R.↗

Strains and tilts on crustal blocks

Geodetic work done over the past century is examined to investigate block motion in areas of intense tectonic deformation, with special attention to geodetic releveling data obtained for Japan. Problems in interpreting strainmeter and tiltmeter to study the behavior of crustal blocks and block boundaries are discussed. Block dimensions of 5 to 50 km seem to occur frequently in regions of intense tectonic activity. Block boundaries are often considerably weaker than contiguous crustal blocks, resulting in a concentration of strains at boundaries and decrease of strains within blocks. Block to block variations in tilt phase and magnitude are observed. There is some evidence that block boundaries may exhibit strain-dependent elastic properties or respond viscoelastically, possibly accounting for the slow transmission of tectonic deformation reported in Japan. If nonlinear behavior is characteristic of regions fragmented by crustal blocks, it will generally not be possible to apply a site correction factor based on the observed distortion of tidal or seismic strains in interpreting secular strains.

Bilham, R. G.↗