Current earthquake and tsunami monitoring relies on ground-based monitoring stations, and the process of gathering information, judging and issuing alerts can take anywhere from several minutes to several hours. The new study proposes that using the existing Global Navigation Satellite System (GNSS) to monitor earthquakes can determine the magnitude of an earthquake in less than a second, dramatically increasing the time it takes to arrange for evacuation of people.
GNSS is the collective name for various satellite navigation systems, commonly used by people including the United States’ GPS, Russia’s GLONASS and the European Union’s GALILEO, etc. Other countries like Japan and India also have their own satellite navigation systems developed.
This study is responsible for the Central Washington University (Central Washington University) geophysicist Melbourne (Timothy Melbourne) said that the system uses the satellite in the sky to send signals to the ground receiving station to locate the exact location of the receiving station. Once an earthquake occurs at the location of the receiving station, the location of the receiving station will change, and by analyzing the signal it is immediately possible to determine the magnitude of the earthquake and the type of ground rupture.
Nowadays, the widely used ground monitoring system is so sensitive that the speed of seismic wave is only a few tens of nanometers per second can be detected; while the detection technology based on satellite system can only detect the displacement of a few centimeters or more.
In the event of a large earthquake, the ground system has to process a large amount of data, leading to a significant increase in the complexity of the judgment. Seismologists generally have to wait for the seismic waves to reach a very distant monitoring station before they can make an accurate judgment, a process that takes about several minutes.
This seismic monitoring system, based on satellite navigation signals, is the first of its kind. The transmission of data back and forth between ground-based receiving stations and satellites, as well as processing centers, is completed in less than a second, communicating as fast as any receiving station anywhere in the world.
This system can therefore be used to detect strong earthquakes of magnitude 7 or greater, as well as to provide early warning of the possibility of a tsunami, providing more time for people to arrange evacuations or to decommission certain infrastructure early enough to minimize disaster damage.
For strong earthquakes, it typically takes tens of seconds, or even minutes, for the energy of the quake to travel through the earth’s crust before the movement of fault zones is seen and cracks appear in the ground. So this means that the satellite system is able to detect earthquakes before the fault zone tearing event, Melbourne said.
Such rapid detection is even more important for tsunami warning. Melbourne said the global monitoring of tsunamis is now using data from the global seismic network, combined with data from global ocean observatories and buoys to determine the combination. The first part of the data takes about 15 minutes to determine the magnitude of the earthquake, and the second part of the data can take up to an hour to be aggregated.
Many fields, such as mining and construction, are now using GNSS signals for mapping and monitoring by setting up ground-based receiving stations, so the popularity of ground-based stations is not a problem. The only problem is that the system relies on open data, and some agencies charge a fee to provide that data. Melbourne said, “Part of my job is to go out and convince countries or regions where earthquakes are likely to occur to open up their data (to use our system) to mitigate the shock that a disaster might cause.”
The study was published May 11 in the Bulletin of the Seismological Society of America.
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