The characterization of soil is essential for the evaluation of seismic hazard, because soil properties strongly influence the damage caused by earthquakes. Methods based on seismic noise are the most commonly used in soil characterization. Concretely, methods based on seismic noise array measurements allow for the estimation of Rayleigh wave dispersion curves and, subsequently, shear-wave velocity profiles. The equipment required for the application of this technique is usually very expensive, which could be a significant economic challenge for small research groups. In this work, we have developed a wireless multichannel seismic noise recorder system (Geophonino-W), which is suitable for array measurements. Each station includes a microcontroller board (Arduino), a conditioning circuit, an Xbee module, an SD card, and a GPS module. 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. Comparisons of Geophonino-W with the commercial systems and field measurements were also carried out. 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. Geophonino-W is an economic open-source and hardware system that is available to any small research group or university.

This article presents a new wireless seismic sensor network system, especially design for building monitoring. The designed prototype allows remote control, and remote and real-time monitoring of the recorded signals by any internet browser. The system is formed by several Nodes (based on the CC3200 microcontroller of Texas Instruments), which are in charge of digitizing the ambient vibrations registered by three-component seismic sensors and transmitting them to a central server. This server records all the received signals, but also allows their real-time visualization in several remote client browsers thanks to the JavaScript’s Node.js technology. The data transmission uses not only Wi-Fi technology, but also the existing network resources that nowadays can be found usually in any official or residential building (lowering deployment costs). A data synchronization scheme was also implemented to correct the time differences between the Nodes, but also the long-term drifts found in the internal clock of the microcontrollers (improving the quality of records). The completed system is a low-cost, open-hardware and open-software design. The prototype was tested in a real building, recording ambient vibrations in several floors and observing the differences due to the building structure.

The commercial data acquisition systems used for seismic exploration are usually expensive equipment. In this work, a low cost data acquisition system (Geophonino) has been developed for recording seismic signals from a vertical geophone. The signal goes first through an instrumentation amplifier, INA155, which is suitable for low amplitude signals like the seismic noise, and an anti-aliasing filter based on the MAX7404 switched-capacitor filter. After that, the amplified and filtered signal is digitized and processed by Arduino Due and registered in an SD memory card. Geophonino is configured for continuous registering, where the sampling frequency, the amplitude gain and the registering time are user-defined. The complete prototype is an open source and open hardware system. It has been tested by comparing the registered signals with the ones obtained through different commercial data recording systems and different kind of geophones. The obtained results show good correlation between the tested measurements, presenting Geophonino as a low-cost alternative system for seismic data recording.

Highlights  Low cost data acquisition system for recording three-component seismic noise.  Suitability of the equipment for the application of the H/V method.  The developed system has been successfully compared with commercial systems.  It is an open source and open hardware system.  The low cost is essential for small research groups with reduced economic support.

The analysis of seismic noise provides a reliable estimation of the soil properties, which supposes the starting point for the assessment of the seismic hazard. The horizontal-to-vertical spectral ratio technique calculates the resonant frequency of the soil just by using a single three-component sensor. Array measurements require at least several vertical sensors registering simultaneously and their analysis provides an estimation of the surface waves dispersion curve. Although these methods are relatively cheaper than other geotechnical techniques, the cost of the sensors and the multi-channel data acquisition system means that small research groups cannot afford this kind of equipment. In this work, two prototypes for registering seismic noise have been developed and implemented: a three-channel acquisition system, optimized for working with three-component sensors; and a twelve-channel acquisition system, prepared for working simultaneously with twelve vertical geophones. Both prototypes are characterized by being open-hardware, open-software, easy to implement, and low-cost. The main aim is to provide a data acquisition system that can be reproduced and applied by any research group. Both developed prototypes have been tested and compared with other commercial equipment, showing their suitability to register seismic noise and to estimate the soil characteristics.