Luna Accelerometer Senses Earthquake from 3,000 km Away

Fiber Optic Accelerometer Performs Long-Range Seismometry … and Much More

Accelerometers that are part of a vibration event detection development deployment for security applications at Luna’s Atlanta office detected a magnitude 7.1 earthquake, which occurred 18 km west of Searles Valley, California on July 6. Luna’s os7520 optical sensors detected and measured the vibration wave as it arrived in Atlanta 650 seconds later.

As part of the pilot vibration-based security system, sensors were buried in soil just below the surface. The setup was not optimized for seismic detection, since the sensors reside in a densely populated, high-traffic area in Atlanta.

The os7520 sensors combined with a HYPERION interrogator enable high-performance vibration monitoring. The all-optical sensors have no electrical connections and are entirely passive. Up to 128 sensors can be monitored with a single interrogator. This data was acquired with a prototype system that monitors the sensor output 24/7 and automatically synchronizes to cloud databases over the cellular network, while also sending notifications of detected events. The main purpose of this deployment is to develop, validate, and refine high performance and versatile vibration monitoring methods and solutions for security applications.

This result demonstrates the exceptional performance of the os7520 vibration sensor, which can be used for wide-ranging applications, including perimeter and border security, structural monitoring, and both strong motion and long-range seismometry.  


 

Figure 1 below shows the event as measured in Atlanta. For validation, Luna engineers also downloaded the waveform for the event from the nearest USGS monitoring station, shown in Figure 2. The timing and waveform structure clearly indicates that these waveforms correspond to the same event.

Figure 1. Ground acceleration measured by sensors at Luna Innovations Atlanta on July 6, 2019 at 03:19:52 UTC time. This data is the average of three sensors buried just below the surface of the lawn. The sensors used were Luna os7520 optical sensors, measured over fiber by a HYPERION optical interrogator. Data was acquired at 1 kHz and then digitally filtered and decimated in 2 stages to the 0.5 Hz sampling rate.
Figure 2. This is the waveform of the event as detected at a seismic station operated by the USGS in Waverly, Tennessee. This is the nearest station to the Atlanta location. The vertical lines indicate the arrival times of P, PP, S and SS modes, respectively left to right. This was measured using a Streckeisen ST-6A VBB seismometer.

 

Contact us for more information on os7520 sensors and the various applications in vibration monitoring.