GNGTS 2018 - 37° Convegno Nazionale

GNGTS 2018 S essione 3.2 707 2.29 m within one grid spacing in 3D. Therefore, although the grid spacing affects the precision of location, the error of the location is acceptable and limited to one grid spacing. This shows the accuracy of the applied location algorithm. Fig. 2 - Location of events from five hammer hits with the uniform velocity model. Stars in different colors named “Hammer n” indicate the estimated source positions for the hammer hits, while the black square is the real hit position, apparently in the air due to the 2m discretization of the model, actually on the rock surface Tab. 3 - Summary of the location results for the hammer hits. X [m] Y [m] Z [m] 3D error [m] Hit position 99.079 44.991 683.2864 - Hammer1 98 46 682 1.96 Hammer2 98 46 680 3.60 Hammer3 98 46 682 1.96 Hammer4 98 46 682 1.96 Hammer5 98 46 682 1.96 Average error 1.079 -1.009 1.6864 2.29 Conclusions. We have performed a preliminary study on microseismic event location considering a monitoring system deployed on a rock cliff in northern Italy. With the aim of exploring the most suitable source for a planned tomographic survey, we performed some trigger tests using a hammer and firework charges. The results showed that the hammer performs better than the firework charges as more geophones can record the source signal. Proper design of