In the period between January 16 and 19, 2023, researchers from component 2, Lada Dvornik, Mario Gazdek, and Iva Lončar, carried out field research to measure ambient noise vibrations using the HVSR method at selected locations in the region of Dalmatia. Measurements of the horizontal and vertical spectral ratio (The Horizontal-to-Vertical Spectral Ratio, HVSR) were carried out using Tromino instruments, purchased from the funds of the CRONOS project. The mentioned measurements are carried out for the purpose of soil research at the given locations, that is, the frequency content of the examined soil is determined in order to obtain information about the depth of the bedrock. In addition to this method, Multichannel Analysis of Surface Waves (MASW) is also usually used, which is planned for future field investigation for the mentioned region.
The bedrock depth is also important information in construction because the natural frequency of the soil directly dictates the type, i.e. the height of the building, in order to avoid the effect of resonance. Therefore, this information is also very important in the later steps of seismic hazard and risk assessment.
The mentioned HVSR measurements were carried out according to the plan for the first year of the CRONOS project.
100 measurements were carried out at the following locations:
- Vinovac – 9 measurements
- Dugopolje (Church of St. Michael – the Dugopolje municipality building) – 6 measurements
- Trilj (industrial area Trilj-Čaporice) – 12 measurements
- Sinj (center) – 6 measurements
- Aržano (Josip Jović elementary school, Church of All Saints) – 9 measurements
- Cista Provo (center) – 6 measurements
- Zagvozd (Church of Lady of Carmel, Zagvozd elementary school) – 6 measurements
- Baška Voda (Bariša Granić Meštar elementary school) – 3 measurements
- Makarska (Stjepan Ivičević elementary school, observatory) – 13 measurements
- Brela (Church of St. George) – 6 measurements
- Omiš (Zakučac, Josip Pupačić elementary school, mountain road to Fortica, Duće cemetery) – 10 measurements
- Split (Marjan-ZOO, Banovina) – 14 measurements
During the measurement, the quality of the instrument installation and the quality of the location itself were considered. Difficult weather conditions caused potential disturbances in measurements, and urban influences (traffic, pedestrians, etc.) were minimized, for example, by night-time measurements (Split).
Prepared by Iva Lončar