Seismological analysis of flood dynamics and hydrologically triggered earthquake swarms associated with Storm Alex [Brief communication]

2022

Article référencé dans le Web of Science WOS:000791467800001

Chmiel M., Godano M., Piantini M., Brigode P., Gimbert F., Bakker M., Courboulex F., Ampuero Jean-Paul, Rivet D., Sladen A., Ambrois D., Chapuis M.

Natural Hazards and Earth System Sciences, 2022, 22 (5), p. 1541-1558 ISSN 1561-8633

On 2 October 2020, the Maritime Alps in southern France were struck by the devastating Storm Alex, which caused locally more than 600 mm of rain in less than 24 h. The extreme rainfall and flooding destroyed regional rain and stream gauges. That hinders our understanding of the spatial and temporal dynamics of rainfall-runoff processes during the storm. Here, we show that seismological observations from permanent seismic stations constrain these processes at a catchment scale. The analysis of seismic power, peak frequency, and the back azimuth provides us with the timing and velocity of the propagation of flash-flood waves associated with bedload-dominated phases of the flood on the Vesubie River. Moreover, the combined short-term average to long-term average ratio and template-matching earthquake detection reveal that 114 local earthquakes between local magnitude M-L = -0.5 and M-L = 2 were triggered by the hydrological loading and/or the resulting in situ underground pore pressure increase. This study shows the impact of Storm Alex on the Earth's surface and deep-layer processes and paves the way for future works that can reveal further details of these processes.

Sciences du milieu [021] ; Hydrologie [062] ; Géophysique interne [066]

FRANCE

Fonds IRD [F B010084775]

fdi:010084775