EQ Monitoring Today
Now that we know the history of earthquake monitoring and the instruments that were used not so long ago, we can learn about what is being used now.
Almost everything now is computerized. The long strips of paper with squiggly lines exist primarily as visual aids for education and outreach purposes. Read on to see more development in earthquake monitoring.
Digital stations, on the other hand, have high and low gain sensors and do their data conversion at the sensing site itself with 24 bit digitizers, thus allowing both small and large signals to stay on scale. The digital information is then sent via digital data link to the central site where it is able to be used immediately by the computers processing and storing the data.
Using digital stations instead of analog stations provides several important benefits:
The high and low gain sensors provide data on scale for both small and large earthquakes.
The digital data can be error checked so that line noise won't cause the data to be corrupted.
Although the data output by different data loggers is often of different formats, the network can incorporate them through simple software changes.
Pictures of Equipment
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The K2 Strong Motion Accelerograph
The K2 as it would be set up at an actual digital site. The metal frame is used to keep things from bumping up against the seismometer while it is in operation. The K2 is crooked in its frame for a specific reason. It must be aligned in a northerly direction so that the North-South and East-West ground motions are indeed what are sensed by the device.
A closer view of the internals of the K2 accelerograph. The metal bar in the lower left hand corner of the case is the battery holder. The three ground motion sensors (for vertical, N-S, and E-W motions) are in the top left hand corner of the device, covered by a protective grille. The data conversion/storage/communications hardware is in the right half of the device. The orange rectangular object to the left is the rechargeable battery which powers the K2 during power shortages.
The Central Site Data Acquisition System
This is a picture of the central site data acquisition system. The tower contains the actual data receiving hardware, as well as a computer and data storage system. The large terminal on the table allows system administrators to modify and maintain the system.
These are some of the new devices that are used in measuring earthquakes.
The Force Balance Accelerometer measure the acceleration of the ground as it is shaking during an earthquake. It uses a feedback system in which the output signal from the transducer is amplified and fed back to a device that moves the mass to the original unperturbed position.
This electronic seismometer is a state-of-the art instrument. It can accurately record both small local earthquakes and large distant ones. It can also record earth tides and the sonic boom produced by the Space Shuttle as it flies into Edwards Air Force Base.
This instrument is a newer version of the FBA-23. It records ground acceleration much more accurately and with greater sensitivity.