Most seismic methods are based on array measurements, in which the analysis of signals recorded simultaneously by a set of sensors provides information about the propagation characteristics of surface waves (velocity-frequency response or dispersion curve) in analyzed soil. A brief revision of seismic methods will be addressed in Section 4, as they are the methods used in this work. Furthermore, geotechnical methods are very invasive, and they are not suitable for application in urban areas. In general, both methods can be very expensive. The determination of the characteristics of subsoil could be conducted through geophysical (i.e., seismic, electric, and magnetic methods) and geotechnical methods (i.e., a borehole test, dynamic penetration test, and standard penetration test).
Therefore, subsoil characterization is mandatory in the evaluation of seismic hazards in urban areas, because it provides information about the site effects when an earthquake occurs. The seismic wave amplification is determined by the physical soil characteristics. This effect can significantly increase the seismic shaking at the surface of the site, especially when it is constituted by soft sediments. The level of damage at each site is closely linked to what is called the “site effect”. The damage produced in different places by the occurrence of an earthquake is not only related to the energy released. Geophonino-W is an economic open-source and hardware system that is available to any small research group or university. The estimated dispersion curves obtained using the proposed system were compared with the ones obtained using other commercial equipment, demonstrating the effectiveness of Geophonino-W for seismic noise array measurements. Comparisons of Geophonino-W with the commercial systems and field measurements were also carried out.
Several laboratory tests were carried out in order to study the performance of the Geophonino-W: A frequency response test (impulse response and noise) synchronization test and battery duration test. Each station includes a microcontroller board (Arduino), a conditioning circuit, an Xbee module, an SD card, and a GPS module. In this work, we have developed a wireless multichannel seismic noise recorder system (Geophonino-W), which is suitable for array measurements. The equipment required for the application of this technique is usually very expensive, which could be a significant economic challenge for small research groups. Concretely, methods based on seismic noise array measurements allow for the estimation of Rayleigh wave dispersion curves and, subsequently, shear-wave velocity profiles. Methods based on seismic noise are the most commonly used in soil characterization. The characterization of soil is essential for the evaluation of seismic hazard, because soil properties strongly influence the damage caused by earthquakes.
0 kommentar(er)
