Seismographs recorded hundreds of small earthquakes every day. Seismographs were set up and began monitoring the volcano for earthquakes. Minor earthquakes have also been measured by seismographs and reported by residents. The seismographs sensed and located earthquakes 1.5 magnitude and larger in the area. This destructive earthquake occurred at 22&colon;15 UTC and was recorded by several early seismographs. The society funded the invention of seismographs to detect and measure the strength of earthquakes. Originally, European seismographs were placed in a particular area after a destructive earthquake. Ground motions from waves or normal modes are measured using seismographs. One of the continuing problems with sensitive vertical seismographs is the buoyancy of their masses. Analog seismographs require analog recording equipment, possibly including an analog-to-digital converter. A variation on this scheme is the use of smoked paper in early seismographs. Another team gave the local officials seismographs, but no instructions on how to operate them. Consequently, a total of 11 seismographs were installed in the region. Therefore, most professional seismographs are sealed in rigid gas-tight enclosures.