  Our objective is to assess the performance of waveform cross-correlation
technique, as applied to automatic and interactive processing of the aftershock
sequence of the 2012 Sumatera earthquake relative to the Reviewed Event
Bulletin (REB) issued by the International Data Centre. The REB includes 1200
aftershocks between April 11 and May 25 with body wave magnitudes from 3.05 to
6.19. To automatically recover the sequence, we selected sixteen aftershocks
with mb between 4.5 and 5.0. These events evenly but sparsely cover the area of
the most intensive aftershock activity as recorded during the first two days
after the main shock. In our study, waveform templates from only seven IMS
array stations with the largest SNRs estimated for the signals from the main
shock were used to calculate cross-correlation coefficients over the entire
period of 44 days. Approximately 1000000 detections obtained using
cross-correlation were then used to build events according to the IDC
definition. After conflict resolution between events with similar arrivals
built by more than one master all qualified event hypotheses populated the
automatic cross-correlation Standard Event List (aXSEL). The total number of
distinct hypotheses was 2763. To evaluate the quality of new events in the
aXSEL, we randomly selected a small portion of XSEL events and analysts
reviewed them according to standard IDC rules and guidelines. After the
interactive review of a small portion of the final product of cross correlation
was obtained which we call the interactive XSEL. We have constructed relevant
frequency and probability density distributions for all detections, all
associated detection,and for those which were associated with the aXSEL and
final XSEL events. These distributions are also station and master dependent.

Geophysics;Physics and Society