0.3 Tanzania, August 2016

Temporary dense deployment of seismic stations in Tanzania to identify previously unknown faults and infer their dimensions. 1 month continuous data (2016-07-31 to 2016-08-31), at 5 stations, 15 channels (3 components per station), provided by Laura Parisi of King Abdullah University of Science and Technology (KAUST). The stations are located about 10 km apart, at the base of a volcanic caldera called Ngorongoro Crater. For all 15 channels, we applied the following preprocessing: 4-12 Hz bandpass filter, then decimated to 25 Hz (factor of 8, from original 200 Hz); also, all time gaps with 0’s were filled with uncorrelated random noise (only on station CES04).

Table S4: FAST input parameters for Tanzania earthquake detection, applied to each component at all 5 stations. For the median statistics calculation (for wavelet coefficient selection), we randomly sampled 10% of the data, once per day. Total number of fingerprints (largest number over all channels): 2,231,989.

Table S5: Network detection input parameters for Tanzania earthquakes at 5 stations, after getting similar pairs of fingerprints from FAST for each station — added similarity from all 3 [HNE,HNN,HNZ] components at a given station and set station-pair threshold of (v=2)*(3 components) = 6.

Table S6: Final thresholds for Tanzania earthquakes, applied to network detection parameters nsta (number of stations that detected event pair) and peaksum (total similarity score at all stations) to determine list of earthquakes, set empirically after visual inspection. For each value of nsta, a different threshold for peaksum can be applied.

Figure 4: Tanzania earthquake detections from 2016-07-31 to 2016-08-31. The vertical axis indicates a measure of network FAST similarity: nsta*peaksum (Table S6). FAST detected a total of 1,156 earthquakes during this month. Some false positive detections had to be removed manually, especially detections on only 2 out of 5 stations.