Bulletin of the Seismological Society of America Volume N . 5-6

Bulletin of the Seismological Society of America Volume N . 5-6

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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1915 edition. Excerpt: ...facts of observation are concordant with the implications of the hypothesis, and, therefore, tend in some degree to support it. In the Coast Ranges, particularly near San Francisco Bay, there are drowned valleys, which point to recent, and probably progressive, subsidence. In spite of this, raised beaches of slight and irregular elevation, and usually of small extent, also occur, apparently contradicting the drowned-valley indications. The hypothesis not only explains and harmonizes these features, but requires their coexistence. We have supposed the down-warping of the Coast Ranges in this neighborhood to be at a less rate than that of the adjacent submarine and Great Valley sedimentation tracts. This positive, general sinking would account for, and require, the drowned-valley phenomena. But if the adjacent lateral territory sinks faster than the mountain belt, a vertical shearing strain will develop locally along the coast and the Great Valley margin. If this became sufficiently acute and so were relieved by minor, local faults, the fling of the rebound would in every case tend to uplift the margins of the mountain tract and downthrow the margins of the submarine and Great Valley areas. Besides the marine terraces, similar features, having of course, different physiographic expression, are to be seen along the western margin of the Great Valley. Since the line of acute shear would not follow with fidelity the indentations of the coast line, or of the junction of foothills and valley floor, minor apparent discrepancies might be expected. Therefore, whether this action is competent or not, it is at least plausible and expectable, and to some extent support is given to the hypothesis. Though less pertinent, the following phenomena are of interest...show more

Product details

  • Paperback | 160 pages
  • 189 x 246 x 9mm | 299g
  • Rarebooksclub.com
  • Miami Fl, United States
  • English
  • black & white illustrations
  • 1236639669
  • 9781236639660