Browsing by Author "Voutilainen, Ahti"

A new ground motion prediction equation, named ON21, is solved for the ST1 Deep Heat enhanced geothermal system in Otaniemi, city of Espoo, Finland. The raw data from seismic events, that occurred during the stimulation of 2018, is processed, instrument response is removed, and frequency domain is used to obtain peak ground displacement, velocity, and acceleration. A database with 20,768 ground motion recordings from 204 events is compiled and used to solve a ground motion prediction equation for peak ground velocity and acceleration for vertical and horizontal movement. The model has a magnitude range from 0.0 to 1.8 on the scale of local magnitude used in Finland, and hypocentral distances of 0 km to 20 km. A 1σ value of 0.60 for vertical peak ground velocity model is lower than the 1σ of the models previously in use at Otaniemi and its surrounding areas. It is observed that the azimuth between the strike of the fault causing the earthquakes and the station recording the events seems to affect the peak ground motion values at a hypocentral distance of no more than 10 km, and beyond that the magnitude and distance are the dominant factors in the peak ground motion values. The new ground motion prediction equation model ON21 should be tested with ground motion data from earthquakes that occurred during the 2020 stimulations to assess its usefulness in predicting peak ground motion values, and to further study the effect of azimuth on the peak ground motion values.