Dynamic Triggering of Mud Volcano Eruptions During the 2016–2017 Central Italy Seismic Sequence

Abstract

On 24 August 2016 a seismic event (Mw 6.0) was the first of the long Central Italy sequence (ongoing at the end of 2017) of medium‐to‐high magnitude earthquakes, with nine Mw ≥5 up to October 2017, and with about 74.000 seismic events registered after 1 year. The largest was the Mw 6.5 30 October 2016 event near Norcia. After the major seismic events, 17 mud volcanoes erupted around Monteleone di Fermo village (Marche region). Mud volcano eruptions generally occurred a few hours to a few days after the main earthquakes, suggesting a seismic triggering. We analyzed the peak ground velocities and dynamic stresses during the three largest earthquakes. We also evaluated the static stress changes in order to assess the potential influence of normal stress changes on the feeder system of the activated mud volcanoes. We find a correlation with dynamic stresses, whereas static stress changes are negligible or negative (with values reaching −0.44 bar, clamping feeder dykes). We conclude that seismic shaking (up to ~3.9 bar during Norcia earthquake) is the dominant driver for these eruptions. Finally, we evaluated the response ratio as a function of the dynamic stress. It increases exponentially with peak dynamic stress varying from <10% for peak dynamic stress >0.3 bar to >50% for peak dynamic stress >2 bar, indicating a link between earthquake shaking and mud volcano activity.

Goldilocks conditions required for earthquakes to trigger basaltic eruptions: Evidence from the 2015 Ambrym eruption

“…The predicted PGVs in the region of the caldera are 0.09 to 0.15 m/s, and assuming a shear modulus of 30 GPa and a shear wave velocity of ~3000 m/s, the peak dynamic stress change would then be ~0.9 to 1.5 MPa (Fig. 4), consistent with estimates from similarly sized earthquakes at similar distances (30).…”

Strain Diffusion from the 30 October 2016 Norcia (Central Italy) Earthquake

“…The red star indicates the epicenter of the 30 October 2016 Norcia earthquake. The yellow triangle indicates the mud volcanoes located near Monteleone di Fermo, which erupted shortly after the Norcia earthquake (Maestrelli et al, ).…”

“…Coseismic effect includes remarkable and diffuse surface faulting (e.g., Civico et al, ; Villani et al, ). Moreover, the emplacement of mud volcanoes about 30 km NE of Norcia shortly after the mainshock suggests dynamic stress transfer by seismic waves (Maestrelli et al, ). However, comprehensive analyses of the long‐term and long‐range effects induced by the largest earthquake of the above crisis are not available so far.…”

Continental degassing of helium in an active tectonic setting (northern Italy): the role of seismicity

“…This correspondence has been related to the enhanced permeability of the extensional tectonic discontinuities 6 . However, it has been also observed that variations of the volatiles degassing rate are earthquake-related, and are frequently post-seismic [7][8][9] . Thus, fluids geochemistry provides evidences of the episodic large-scale transport of volatiles.…”