A new radio-based monitoring technology by Koherent is introduced for earthquake monitoring. A single 24/7 real-time monitoring system can be used for early warning as well as monitoring 3D building dynamics and irreversible changes during and after an earthquake.
Introduction
Koherent has developed a new radio-based 3D displacement monitoring system that operates in the unlicensed 5 GHz band. It can measure relative movements of just 0.1 mm over up to 1 km distance even at 100 times per second. The system operates in real time with <100ms latency to cloud and can measure both fast (up to 50 Hz) and slow (over months) 3D movements. As a radio system it is insensitive to weather and dust. It is also much less sensitive to jamming compared to e.g. GNSS systems.
Usage for earthquake monitoring
Due to the high measurement speed, accuracy and range of the system - as well as its capability to provide real-time monitoring – we envision three possible usages for earthquake monitoring before, during and after the quake.
Earthquake early warning
As the earthquake P-waves travel faster than the S- and L-waves that cause the actual damage, its detection can be used for earthquake early warning. The P-wave causes displacement of 1 mm to tens of mm over a wavelength of ~800 meters for significant quakes with a typical frequency of 10 Hz. This is something that the Koherent system can detect as a movement between the lower parts of nearby buildings and provide a warning in the cloud in less than 1 second.
The dynamics of buildings during the quake
The capability to accurately measure fast movements of different points in buildings with respect to sensors in the ground (and nearby buildings) can give a precise characterization of the building 3D dynamics during the quake. All sensors are accurately in time sync so vibration modes can be derived from the data.
Displacements caused by the quake
As the measurement system can also accurately record “static” movements, possible irreversible displacements in buildings can be analyzed in 3D immediately after the quake.
Exemplary deployment
The position calculation is based on distance measurements between multiple sensors. Therefore, a deployment shown in the figure would yield monitoring for all three applications described. Each sensor requires power supply and connection to the cloud e.g. using 4G or 5G cellular connection.
