Abstract
In earthquake monitoring, an important aspect of the operational effect of earthquake intensity rapid reporting and earthquake early warning networks depends on the density and performance of the deployed seismic sensors. To improve the resolution of seismic sensors as much as possible while keeping costs low, in this article the use of multiple low-cost and low-resolution digital MEMS accelerometers is proposed to increase the resolution through the correlation average method. In addition, a cost-effective MEMS seismic sensor is developed. With ARM and Linux embedded computer technology, this instrument can cyclically store the continuous collected data on a built-in large-capacity SD card for approximately 12 months. With its real-time seismic data processing algorithm, this instrument is able to automatically identify seismic events and calculate ground motion parameters. Moreover, the instrument is easy to install in a variety of ground or building conditions. The results show that the RMS noise of the instrument is reduced from 0.096 cm/s2 with a single MEMS accelerometer to 0.034 cm/s2 in a bandwidth of 0.1–20 Hz by using the correlation average method of eight low-cost MEMS accelerometers. The dynamic range reaches more than 90 dB, the amplitude–frequency response of its input and output within −3 dB is DC −80 Hz, and the linearity is better than 0.47%. In the records from our instrument, earthquakes with magnitudes between M2.2 and M5.1 and distances from the epicenter shorter than 200 km have a relatively high SNR, and are more visible than they were prior to the joint averaging.
Highlights
Earthquakes are common natural phenomena on Earth
Japan, South Korea, and Taiwan have all established earthquake early warning systems (EEW systems) [10,11,12,13,14,15,16,17,18,19,20,21,22]; Turkey, Romania, Italy, China, Israel, and southwestern Iberia are on the verge of developing and testing their own seismic intensity rapid reporting systems [10,14,23,24,25,26,27,28]
Because the instruments were installed in very different areas, it was not possible for each instrument to be hardwired into a network
Summary
Earthquakes are common natural phenomena on Earth. According to statistics, approximately 1 million earthquakes occur every year [1], and approximately 1000 of them can cause damage. Warning Research Group of National Taiwan University (NTU) developed a P-alert device based on MEMS accelerometers and formed an EEW test network system in June 2012 [36] They used a low-cost MEMS accelerometer to develop a seismic intensity rapid reporting instrument that can output ground motion parameters in real time and that can quickly measure the vibration intensity within a few seconds to tens of seconds after the earthquake occurs [36]. MEMS sensor for EEW high-density networks, with a dynamic range of 87 dB, capable of detecting small earthquakes from M3.1 to M3.6 within 50 km [4] These low-cost commercial MEMS digital accelerometers have a number of advantages: they are small, record data in three directions, consume little power, and do not require an AD conversion circuit or calibration.
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