Displacements, strains, and tilts at teleseismic distances

Abstract

The dislocation theory representation of faulting of Vvedenskaya, Steketee, Chinnery, and Maruyama is used to compute the residual displacement, strain, and tilt fields at intermediate and large distances from major earthquakes. It is shown that the distant fields are large enough to be detected by modern instruments. The vertical displacement field from the Alaskan earthquake of March 27, 1964, indicates that the primary fault extended to a depth of 150 to 200 km and that it probably came to within 15 km of the surface. The residual strain observed at Hawaii amounted to 10^(−8), a value which is reasonably consistent with the extent of faulting and the displacements near the source. The elastic strain energy release was about 10^(25) ergs. Other observations of residual strains and tilts are examined. In some cases nonfaulting sources are probably involved. In other cases the observations may be a spurious manifestation of instrumental hysteresis. The Mindlin‐Cheng catalog of fields from various nuclei of strain in a half‐space offers a convenient way to derive residual displacements from diverse sources, including those of Chinnery and Maruyama.