What are two uses for seismometers?

iT MEASURES EARTHQUAKE TREMORS AND SHOCKS- Some can also be used- a two-truck team for these portable ones- for prospecting for underground oil and gas deposits. one truck shoots off ( through a well or derrick framework) an underground depth charge, the other truck- they are in touch by two way radio but use whistle blast signals- records the shockwaves on a modified seismograph, analysis of the seismogram or chart can be used to deduce if there are any echo anomalies caused by Oil or natural gas deposits. Generally, the term is used for instruments measuring and recordind earthquake shocks on the Richter scale. 7.0 is a big Jolt- but the Japanese Quake that caused the nuclear accident- went up to 9.0 Great Quake.