Figure 1.10

Figure 1.10A Figure 1.10B Figure 1.10C



Examples of how arrival times have been picked over the years. Traces of the 19840214 09:01 mN 2.5 event from which Pg and Sg phases were picked during the period October 1977 to November 1988. (A) High gain display. The top and bottom X axes are second marks. The six traces correspond to stations A10; A16; A20; A64; A54 and A61. Arrival times were measured by interpolating between the two vertical 10 second lines. Since only the vertical traces existed, Pg phases were generally more evident than the Sg phases. (B) Low gain display. Some Sg phases were picked on this plot. (C)Example of a computer display used to pick Pg and Sg phases after 1993 (software "dan" by Nanometrix Inc). The icons (top) represent the various options to get, display or analyse data. The lower three traces are the three components of station A54 (Z: vertical; N: north-south; E: east-west). The time scale for these three traces can be seen at the bottom (40 seconds total). The top trace represents an enlarged view of 2 seconds of the trace A54..EHZ. Phases are picked in the zoom window, with adjustable X and Y scaling.