Recorded with the Very Broadband System in Pasadena

Since 1 December 1987, a very broadband seismographic system has been in operation at the Kresge Laboratory of the California Institute of Technology. This system consists of the Streckeisen-1 very broadband sensor (Wielandt and Streckeisen, 1982), the Kinemetrics FBA-23 triaxial force balance accelerometer and a Quanterra data-logger with a 24-bit (for Streckeisen-1) and a 16-bit (for FBA-23) digitizer. The details of the data logger are described in Steim (1986). The overall dynamic range of this system is about 200 db. This system was constructed as a joint project between the California Institute of Technology, the U.S. Geological Survey, the University of Southern California and the International Research Institution for Seismology (IRIS), and is an element of the IRIS global network as well as the TERRAscope network of California Institute of Technology. A brief description of the system is given by Given et al. (1989). The Very Broadband (VBB) system recorded the 3 December 1988, Pasadena earthquake (Origin Time: 12/3/1988 11:38:26 GMT; ML = 4.9; 34.1412N, 118.1327W; depth = 15.6 km) on scale. These records are unique because the station is only about 4 km from the epicenter so that not only the far-field but also nearfield displacements were clearly recorded. The maximum acceleration at this station was about 5 per cent of g. Figure la shows the displacement trace obtained from the low-gain channel (Kinemetrics FBA-23) by time-domain integration with high-pass filtering at 5 sec to remove the baseline drift. The far-field pulses and the near-field displacement (displacement between P and S) are clearly recorded.