Geofísica

We report a geophysical investigation at a former wood treatment facility that used creosote oil in the treatment process. Creosote is a DNAPL (Dense Non-Aqueous Phase Liquid) and previous studies have detected this contaminant in groundwater samples from the site. Two spill locations are known.

The Quaternary Pantanal sedimentary basin is tectonically active with earthquakes with magnitude up to 5.4. The upper mantle of this region presents low velocity in the propagation of the P and S seismic waves. To better understand the causes of this low-velocity anomaly of the S wave beneath the Pantanal Basin we analyzed surface-wave dispersion curves. We only use events of magnitude larger than or equal to 5.5 mb, with good azimuthal distribution. For the Rayleigh surface waves, we measured phase and group velocities for fundamental and first higher modes.

Whether intraplate earthquakes have different average source properties, compared to interplate events, has been long debated.

Whether intraplate earthquakes have different average source properties, compared to interplate events, has been long debated. It has been proposed that intraplate events tend to rupture smaller areas with higher stress drops, compared to the average interplate earthquake. Here we estimate the rupture lengths of several Brazilian earthquakes by accurately locating their immediate aftershocks. The sparsity of stations in low-seismicity regions, such as Brazil, hinders accurate epicentral determination.

O embasamento da Bacia do São Francisco entre os estados de Minas Gerais e Bahia (Alto de Januária) é caracterizado por um conjunto de rochas que variam desde gnaisses, migmatitos e anfibolitos do Arqueano, até granitoides porfiríticos e sienitos do Paleoproterozoico, e que tem sido agrupadas como um Complexo Arqueano-Paleoproterozoico nos trabalhos de mapeamento geológico regional. Neste estudo, cristais de zircão de duas amostras do embasamento do Grupo Bambuí no Alto de Januária foram datados pelo método U-Pb SHRIMP.