Type of parameter | Main Recommendations | |
---|---|---|
Recording duration | Minimum expected f0(Hz) | Recommended minimum recording duration (min) |
0.2 | 30′ | |
0.5 | 20′ | |
1 | 10′ | |
2 | 5’ | |
5 | 3’ | |
10 | 2’ | |
Measurement spacing | Microzonation: start with a large spacing and, in case of lateral variation of the results, densify the grid point. Single site response: never use a single measurement point to derive f0 value, make at least three measurement points. | |
Recording parameters | Level the sensor as recommended by the manufacturer. Fix the gain level at the maximum possible without signal saturation. | |
In situ soil-sensor coupling | Set the sensor down directly on the ground, whenever possible. Avoid setting the sensor on “soft grounds” (mud, plowed soil, tall grass, etc.) or soil saturated after rain. | |
Artificial soil-sensor coupling | Avoid plates from “soft” materials such as foam rubber, cardboard, etc. On steep slopes that do not allow correct sensor leveling, install the sensor in a sand pile or in a container filled with sand. On snow or ice, install a metallic or wooden plate or a container filled with sand to avoid sensor tilting due to local melting. | |
Nearby structures | Avoid recording near structures such as buildings, trees, etc. in case of wind blowing (faster than about 5 m/s). It may strongly influence H/V results by introducing some low frequencies in the curves. Avoid measuring above underground structures such as car parks, pipes, sewer lids, etc. | |
Weather conditions | Wind: protect the sensor from the wind (faster than approx. 5 m/s). This only helps if there are no nearby structures. Rain: avoid measurements under heavy rain. Slight rain has no noticeable influence. Temperature: check sensor and recorder manufacturer’s instructions. Meteorological perturbations: indicate on the field sheet whether the measurements are performed during a low-pressure meteorological event. | |
Disturbances | Monochromatic sources: avoid measurements near construction machines, industrial machines, pumps, generators, etc. Transients: in case of transients (steps, cars, etc) increase the recording duration to allow for enough windows for the analysis, after transient removal. |