Abstract

The eastern flank of the Mount Etna stratovolcano is affected by extension and is slowly sliding eastward into the Ionian Sea. The Pernicana fault system forms the border of the northern part of this sliding area. It consists of three E-W−oriented fault sectors that are seismically active and characterized by earthquakes up to 4.7 in magnitude (M) capable of producing ground rupture and damage located mainly along the western and central sectors, and by continuous creep on the eastern sector. A new topographic study of the central sector of the Pernicana fault system shows an overall bell-shaped profile, with maximum scarp height of 35 m in the center of the sector, and two local minima that are probably due to the complex morphological relation between fault scarp and lava flows. We determined the ages of lava flows cut by the Pernicana fault system at 12 sites using cosmogenic 3 He and 40 Ar/ 39 Ar techniques in order to determine the recent slip history of the fault. From the displacement-age relations, we estimate an average throw rate of ∼2.5 mm/yr over the last 15 k.y. The slip rate appears to have accelerated during the last 3.5 k.y., with displacement rates of up to ∼15 mm/yr, whereas between 3.5 and 15 ka, the throw rate averaged ∼1 mm/yr. This increase in slip rate resulted in significant changes in seismicity rates, for instance, decreasing the mean recurrence time of M ≥ 4.7 earthquakes from ∼200 to ∼20 yr. Based on empirical relationships, we attribute the variation in seismic activity on the Pernicana fault system to factors intrinsic to the system that are likely related to changes in the volcanic system. These internal factors could be fault interdependencies (such as those across the Taupo Rift, New Zealand) or they could represent interactions among magmatic, tectonic, and gravitational processes (e.g., Kīlauea volcano, Hawaii). Given their effect on earthquake recurrence intervals, these interactions need to be fully assessed in seismic hazard evaluations.

Highlights

  • Knowledge of the slip rates of active faults is critical for understanding the earthquake recurrence rate and the tectonic driver(s) of seismicity, and evaluating the rate of interseismic strain accumulation around a locked fault

  • On the basis of the fault scarp heights, measured using topographic profiles calculated from digital elevation model (DEM) data, and of the lava flow ages from the geological map (Branca et al, 2011), Azzaro et al (2012) estimated vertical slip rates ranging from 3.3 to 5.2 mm/yr in the eastern sector of the Pernicana fault system during the Holocene (15–3.9 ka)

  • By integrating the mapped lava flows (Branca et al, 2011) with detailed field mapping and trace-element geochemistry, we identified five lava flows that are displaced to different degrees in the central sector of the Pernicana fault system: the Piano Pernicana (PP), Pineta di Linguaglossa (PL), Monte Ponte di Ferro (FR), Due Monti (DM), and Millicucco (ML) lavas (Fig. 2B)

Read more

Summary

INTRODUCTION

Knowledge of the slip rates of active faults is critical for understanding the earthquake recurrence rate and the tectonic driver(s) of seismicity, and evaluating the rate of interseismic strain accumulation around a locked fault. Slip rate variability on the Pernicana fault system (Mt. Etna) and magmatic activity control deformation processes yields fundamental information for evaluating the seismic hazards in volcanic regions. We combine a detailed study of the morphology of the most active sector of the Pernicana fault system of Mt. Etna with new age determinations of faulted lava flows in order to construct a model of the spatial and temporal variation in the fault slip rate. Etna with new age determinations of faulted lava flows in order to construct a model of the spatial and temporal variation in the fault slip rate This morphochronological approach constrains fault activity over a time period that is longer than can be assessed by instrumental measurements or historical data. The eastern sector of the Pernicana fault system develops for 9 km from Rocca Campana to the coast with a general NW-SE trend (Azzaro et al, 2012)

Due Monti
DISCUSSION
CONCLUSIONS
Full Text
Published version (Free)

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call