The EEE Catalogue: a global catalogue of Earthquake Environmental Effects

Abstract

In this paper, we provide a review of the properties and behavior of active faults in the Borborema Province, northeastern Brazil, using instrumental, historical and paleoseismological records. The Borborema Province is one of the most seismically active parts of the South American stable continental region (the South American Platform). The Province encompasses an area ~ 900 km long and ~ 600 km wide. It is composed of a branching system of Neoproterozoic orogens, encompassing Archean and Proterozoic inliers deformed during the Brasiliano orogeny at ~ 750–500 Ma. Active faults reactivate shear zones or regional foliation and quartz veins or cut across the preexisting fabric. Active faults are usually strike–slip and generate events ≤ 5.2 mb, which we interpret as the lower limit for maximum possible earthquakes. Seismicity is concentrated in the upper crust down to a depth of 12 km. Earthquake sequences illuminated naturally occurring faults up to 40 km long and segments in the order of 0.5–2.6 km in faults related to induced seismicity. Earthquakes have a recurrence interval of ~ 15 years for Ms = 4. Paleoseismological data indicate that although earthquakes associated with surface ruptures have not occurred in the last 200 years, they struck the region in the last ~ 100 ka. Paleoearthquakes have a recurrence interval of ~ 15.8 ka for magnitudes of ~ 5.5 Mw in individual faults. Moreover, earthquake-induced soft-sediment deformation caused by events of at least 5.5–6.0 Ms have occurred at least six times in the last 400–10 ka in one alluvial valley. Seismically defined faults are concentrated along the continental margin at the border of sedimentary basins as far as 250–300 km inland in areas of extended crust; faults in the paleoseismic record are also found in rift basins along this margin. Both records also reveal that active faults tend to be hydraulically conductive.