. Compendium of meteorology. Meteorology. 1314 MICROSEISMS SO that their optimum response range will be in reso- nance with the microseisms. Horizontal component instruments were chosen in preference to vertical component seismographs because they are simpler to operate and are much less sensitive to fluctuations in temperature and hence require much less elaborate vault insulation. The seismographs at the outlying corners are connected by shielded cable to the respective gal- vanometers in the main vault of the tripartite station where they record on a triple drum whose speeds of rotation and
. Compendium of meteorology. Meteorology. 1314 MICROSEISMS SO that their optimum response range will be in reso- nance with the microseisms. Horizontal component instruments were chosen in preference to vertical component seismographs because they are simpler to operate and are much less sensitive to fluctuations in temperature and hence require much less elaborate vault insulation. The seismographs at the outlying corners are connected by shielded cable to the respective gal- vanometers in the main vault of the tripartite station where they record on a triple drum whose speeds of rotation and endwise translation are variable. Moderate speeds are used as long as there is no evidence of a storm. When the ampHtudes of the microseisms are seen to increase, the drum rates are greatly accelerated (Fig. 4).. Fig. 4.âPart of a record made at the Miami, Florida, tripartite station of the U. S. Navy, August 23, 1949, showing large microseisms recorded at the stand-by rate (top) and at the hurricane rate (bottom). Time interval between interrup- tions in both cases, 15 sec. However, the problem still remains as to the mecha- nism by which a storm center produces the elastic waves on the ocean bottom and why they are so conspicuously characterized by groups resembling inter- "^m^if^ii-^jhlli-^^fi^ w W H'^m^lMhh ^m^^'lVl^wyl^f^vw^KJ^f, rt ^'*''^'^^^^^^ â ^'/>\1'^%^>,^^^^^^ ference patterns (Fig. 5). An argument in favor of swell and decay of activity at the source rather than interference from independent sources within the storm area is the similar appearance of the records in many different directions. A thorough study of the "groups" from this point of view remains to be Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original American Meteorological Society. Committee on the Compendi
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