Gianluca Norini

Bio: Gianluca Norini is an academic researcher from National Autonomous University of Mexico. The author has contributed to research in topics: Volcano & Geothermal gradient. The author has an hindex of 23, co-authored 70 publications receiving 1304 citations. Previous affiliations of Gianluca Norini include University of Milan & National Institute of Geophysics and Volcanology.

Structural architecture of the Colima Volcanic Complex

Abstract: [1] The Colima Volcanic Complex (CVC) is currently the most active Mexican volcano and is located in the western sector of the Trans–Mexican Volcanic Belt, inside the active Colima Rift, a regional N-S-striking extensional structure. The Colima Rift is filled by a ∼1 km-thick sequence of quaternary lacustrine sediments, alluvium, and colluvium, mostly underling the about 3000-m-thick volcanic pile of the CVC. In this work we present the results of a detailed morphostructural and field study of Quaternary faults and fractures in the CVC and the surrounding area, including the regional structures of the Colima Rift. We also present a geometrical modeling of the faults inside the volcano and a numerical model of the gravity-induced stress and strain fields of the CVC. The study attempts to characterize the geometry, kinematics, and dynamics of the deformation features of the CVC and relate it with the volcano structure, the geology of the substratum, and the geodynamic setting of the region. Our model considers that the observed deformation of the CVC and the surroundings results from the interplay between the active N-S-trending regional extensional tectonics and the southward spreading of the volcano over its basement forming an E-W-oriented volcanotectonic graben. The interaction between regional tectonics and previously unrecognized volcanic spreading can control magma migration and flank instability, in an area where eruptions and sector failures represent a potential high risk for more than 500,000 people.

Topographic site effects and the location of earthquake induced landslides

Abstract: In the epicentral areas of major recent earthquakes, landslide density scales with peak ground acceleration. Topographic site effects on seismic waves are known to cause important gradients in ground acceleration in individual mountain ridges. Using landslide maps from the epicentral areas of earthquakes near Northridge, California, Chi-Chi, Taiwan, and the Finisterre Mountains of Papua New Guinea, we have investigated the control of these site effects over the location of earthquake induced slope failure. In our examples, earthquake-triggered landslides clustered near ridge crests, where the susceptibility to landsliding was greatest. This pattern is strongest in the Northridge epicentral area, and secondary landslide clusters were found in colluvial slope toes in western Taiwan and above inner gorges in the Finisterre Mountains. In contrast, rainfall-triggered landslides in the western Southern Alps of New Zealand were evenly distributed over all slope segments, and the landslide susceptibility was lowest near ridge crests. Observed patterns of earthquake induced landsliding are consistent in a diverse geological substrate. They correlate with the distribution of very steep slopes in the epicentral areas, but we demonstrate that topographic site effects can also be a strong control. Using the impedance operator method, we have modeled the propagation of seismic waves in a generic ridge-and-valley topography with and without inner gorge. This topography has little effect on incoming P waves, but a strong effect on S waves, giving rise to a significant amplification of peak ground accelerations at or near ridge crests, and at convex knickpoints within ridge flanks. The preferential orientation of landslides away from earthquake epicenters in the Finisterre Mountains and central west Taiwan is likely caused by asymmetric amplification of oblique incoming seismic waves across mountain ridges, and indicates that topographic site effects have dominated over topographic controls on landslide location in these areas. Although orientation of landslides in the Northridge area does not conform with this interpretation, our results suggest that knowledge of topographic site effects and the attenuation of seismic waves can be an important tool in the prediction of spatial patterns of earthquake induced landsliding.