To reduce the number of false alarms it is necessary to steer detection beams to local areas. By detecting local events on these beams and by using a higher S/N threshold in processing these signals, we can effectively reduce the number of false alarms from the original 57% to 41%. A new beam set has been developed and deployed uhich concentrates teleseismic beams in high seismicity areas instead of spacing them equidistantly apart. This arrangement reduced the average detection errors from 200 km to 50 km, there is also some indication of a lowered detection threshold on the order of 0.1 + 0.1 magnitude units.

The phase PKIIKP, which is once reflected from the underside of the inner core boundary, was detected at LASA for a large Novaya Zemlya event at an epicentral distance of 63°. The detection was verified by a technique similar to the VESPA process. Clear arrivals for the phases PcP, P2KP, P4KP, and P7KP were also observed. The near‐side reflection PKiKP was unfortunately not observed for this event, but it is nevertheless possible to estimate the compressional velocity in the upper half of the inner core by using the differential PKIIKP‐PcP travel time. Using this single observation, we estimate the average velocity in the outer half of the inner core to be 11.0 km/sec. This number changes by less than 0.1 km/sec for variations in inner core radius from 1215 to 1230 km, for possible errors in the observed differential times of several seconds, and for reasonable differences in the outer core velocity model (Gilbert et al., 1973, vs. Jordan, 1972). A travel time table for PKIIKP is given.