Strong motion earthquake accelerograms, digitized and plotted data, Volume I - uncorrected accelerograms; Part B - Accelerograms IB21 through IB40

Abstract

The first set, of 20 uncorrected digitized earthquake accelerograms was published in July, 1969, as Volume I, Part. A of the present series. That volume also contained introductory material and background information describing the methods used, accuracies, etc. which should be referred to by all users of the data. Over 500 copies of the first report were distributed to investigators all over the world, and we are grateful for the many comments we have received which will guide our future efforts. The format used in presenting the data seems to have received a general approval, and we have accordingly continued it without change for the present report. Two records in this report need special mention. IB21 Vernon, California, 3-10-33, 1754PST, was digitized in two parts. The first part was an enlarged print of the faintly recorded strong motion portion, and the second part was the normal translucent contact print. An overlap was included. After scaling the first digitized portion to be the same as the second, the two portions were joined by least square fitting the overlapped portion.. The usual procedure for uncorrected data was then followed. The other record was IB33 Cholame-Shandon, California, No. 2, 6-27-66, 2026PST. The accelerograph component in the N25W direction malfunctioned, leaving no suitable recorded trace, and the printout and plot are consequently excluded. On some of the early records with no fixed trace incorporated we have been able to consider the time mark trace as an approximation to a fixed trace, for all three components. Digitization of a particular place in each time mark then allowed use of the (x, y) coordinates for a fixed trace, and the x-coordinate for a time mark. The printout and plots as before contain asterisks and arrows, respectively, indicating where the record was shifted in the digitizer when required.