Reservoir Induced Seismicity at Nova Ponte (MG): Revisited

Nova Ponte reservoir (situated on the Araguari and Quebra Anzois rivers, planned capacity 1.28 x 109 m3 , maximum water depth 132 m; formed behind an earth-rockfill type dam with height 142 m and length 1600 m) is one of the recent cases of reservoir induced seismicity (RIS) in Brazil (see also Veloso et al., 1994 and 1995 or Ferreira et al., 1995 for presentation of other case histories of RIS in Brazil). Pre-impounding seismic monitoring has started 8 years before filling, using a single l-component SP analog seismic station, without detecting any local seismic activity in a radius of 80 km around the dam. Shortly after beginning of impounding (14 October 1994) quasi-continuous induced activity was detected. The seismic activity was triggered as soon as the lake attained about 20% of the full planned volume.