Fig. 4

Digitization Example 1: 1938 Earthquake Off Coast of Northern Ibaraki, Japan. Screenshot from DigitSeis showing the completed analysis of the May 22–23, 1938, long-period east–west seismogram recorded at the Harvard Seismographic Station. The left column contains various functionalities in the form of push-buttons and editable boxes which the user goes through from top to bottom to process the analogue seismogram digitization. Most of the screen space is taken up by the image window on the right where the digitized traces in light and dark blue are overlain on top of the analogue seismogram image. The yellow vertical bars indicate the rightmost location of each time mark, providing the position at which each minute begins, and the vertical red bars show the beginning and ending of each line. Time stamps (in UTC) are given for each 15-minute interval. Note that a beta-version of DigitSeis 1.6 is used here; hence, the layout of functionalities is not the same as the released version 1.5