. After earthquake and fire . dedfor a distance of 25 to 30 miles on each side of the rift, althoughthese observations are complicated by the possible occurrenceof other lines of movement. The report does not refer to it,but it is likely that there was another rupture, traversing theeastern side of the Contra Costa hills, across Mare Island andthrough Sonoma county. The main line of disturbance, andthe only one positively ascertained, cuts obliquely throughthe Santa Cruz mountains and is independent of such topog-raphy as it is due directly to ordinary erosion. It had beennoted and described s
. After earthquake and fire . dedfor a distance of 25 to 30 miles on each side of the rift, althoughthese observations are complicated by the possible occurrenceof other lines of movement. The report does not refer to it,but it is likely that there was another rupture, traversing theeastern side of the Contra Costa hills, across Mare Island andthrough Sonoma county. The main line of disturbance, andthe only one positively ascertained, cuts obliquely throughthe Santa Cruz mountains and is independent of such topog-raphy as it is due directly to ordinary erosion. It had beennoted and described several years ago, for this reason. That CONCERNING THE EARTHQUAKE. 125 is to say, it is the track of an old break in the earths surfaceof a magnitude far exceeding the recent small slip and themovements which it marks must have been as much greaterthan the recent disturbance as a railroad collision surpassesthe encounter of two persons in a crowd. The big fault orig-inated far back in geologic time; it probably antedated mans. A Crack Across Van Ness Avenue. first appearance and each succeeding movement involved in-tervals of time so great as to make human history an inade-quate measure. Therefore, from a practical standpoint theproof of earlier disturbances and the suggestion of others yetto come, need cause no alarm, for it is the geologist whospeaks, and he deals with time extravagantly. As to the effect 126 AFTER EARTHQUAKE AND FIRE. on buildings, the Commissions report confirms the first infer-ences, which were those made on the occasion of previousearthquakes—and disregarded. Structures built on madeground or on alluvial soil suffered severely, because in suchfoundations the earth-waves are of maximum a jelly be placed in a porcelain bowl and if the latter betapped, the vibrations pass through the highly elastic mediumof the bowl in swift but minute waves that produce no appar-ent effect, but when they strike the jelly, their amplitude isenlarged and their
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