GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 1.1 GNGTS 2024 locaton of each seismic event. Four parameters describe the event locaton in space and tme (X, Y, Z, T0), two parameters represent the elastcity of the rock volume (Vp, Vs) and the last two are used to evaluate the data uncertaintes (π p, π s ). The X and Y parameters show a Gaussian distributon with a standard deviaton of about 1 km. The Z parameter (depth value) shows a Gaussian distributon with a mean value at around − 7 ± 3 km for this event. (Figure 1a–c). The velocity of P waves shows a Gaussian distributon with an average value between 5 and 6 km/s, whereas the velocity of S waves has the highest peak at 3.5 km/s with a standard deviaton of about 1 km/s (Figure 1d, e). Both P (π p, ) and S wave uncertaintes (π s ) have a Gaussian distributon with a narrow shape meaning that they have been well-constrained. The average value for π s is 1.2, for π s is 1.4, both with standard deviaton lower than 1 (Figure 1g, h). Finally, the mean value for the Vp ∕Vs rato of 1.69 with a standard deviaton of less than 0.1. The Figure 2 shows the located natural events within the Donegal Granite region. The natural seismicity is gathered between 55.12 and 55.22 N and between −7.59 and − 7.74 E (580–590 Km on the X coordinate and 6110–6120 Km on the Y coordinate) (Figure 2a). In the lower panel (panel b), the events are shown in cross-secton along the track line A-B. The majority of the events is clearly aligned, showing a trend towards SE with a high dip angle. Figure 3 shows the distributon of located blast events within the Donegal area. Most of the blast events are concentrated in the proximity of actve local quarries in the area. Table 1 resumes the geographical locatons for the Donegal's quarries. Quarrie’s locatons have been used to cross-validate the locaton of the recorded blast events. Comparing the positon of the quarries and the clusters of localized blast events, the correlaton between the two is clearly visible. This means that the majority of the anthropic events in Donegal are quarry blasts and they have been correctly localized by McMC procedure to their correspondent quarry.