Exploring the Influence of Topography on Seismicity Patterns in the Northern Chile Andes

Abstract:

The high topographic of the Andes has been resulted from the long-lasting and ongoing convergence between Nazca and South America plates. The build-up of the high topographic Andes does not only have reduced the convergent rate in the long-term but may have also influenced the short-term patterns of seismicity. The high mountains and the west flank of the Northern Chile is experiencing shallow and deep seismicity, with notable along-strike variations. Motivated by these considerations, we integrate modeling of Gravitational Potential Energy (GPE) and Global Positioning System (GPS) observations to investigate the control of the topography on the seismicity distribution. In this attempt, it is hypothesized that shallow seismicity is strongly influenced by the GPE in the range per unit area (1.45 -1.66) x10¹⁴ N/m due to high topography. By calculating the deviatoric stress associated with GPE and strain rate from GPS velocities, we obtain depth integrated value of stress for the full thickness of the lithosphere and the state of the stress in the upper crust and seismogenic plate contact. The GPE field in combination with GPS derived strain rates are used to sketch the present deformation pattern in the northern Chile Andes in regard of the crustal seismicity. The results indicate that high GPE gradient exhibits significant relationships with the shallow earthquake activity in the region. Therefore region of large topographic, where earthquakes have not occurred in past years, may be considered as potentially seismic hazards. Therefore high GPE gradient factors should be considered in the studies of earthquake activity and seismic hazard estimation.