Stochastic ground motion simulation of earthquakes associated with September 19, 2021, Cumbre Vieja (La Palma Island) eruption: Determination of the quality factor Q, spectral decay parameter kappa, and site response

The relatively strong damage caused by the seismicity associated with historical eruptions in La Palma (Canary Islands) makes it necessary to upgrade the seismic hazard of the island to produce seismic scenarios for future eruptions. Moreover, ancient earthquakes related to older eruptions can be studied if the seismic waves they produced are reproduced. To simulate such scenarios, the characteristics of the unknown earthquake must be determined: its focal characteristics including focal mechanism, location, magnitude, and stress drop; path properties, namely the geometrical spreading, quality factor Q, and its frequency dependence, along which the seismic waves propagate; and site effect. For the site effects, we considered the crustal and Vs30 amplification factors and the kappa value for the station, which represent the spectral amplitude diminution in the high-frequency band. The simulation process used in this study is known as the stochastic simulation technique, which is based on the stochastic properties of strong ground motion and the utilization of a simple physical model for the source. Considering the seismicity registered during the last eruption on the island of La Palma on September 19, 2021, we calculated the parameters required for the simulation to reproduce the strong ground motion of some of the recorded events. The adjustment of the observed to the recorded strong-motion records revealed the goodness of fit and the extent to which future simulations will be close to the real data. The use of the calculated parameters in future studies would permit us to increase our knowledge of the seismic hazards on the island by considering different possible scenarios. • Spectral decay kappa κ for each station is calculated. • Quality factor Q c for coda waves is calculated and its frequency dependency. • The Vs30 parameter for each recording site is evaluated using ReMi surface wave method. • An empirical spectra factor is deduced for the Broad Band stations. • A simulation process is carried out to develop theoretical response for future or past earthquakes.