Have you seen the movie “Contact” ? In this film, a father reminds his young daughter that small moves adjusting a radio antenna’s frequency is a more effective method to locating a ping back (another radio antenna operator on the same frequency). Similarly, small moves, or changes, in air temperature affects responses on the EQ1 educational seismograph…..more specifically, it yields a change in volume of the instrument’s dampening oil which, in turn, yields “apparent” ground movement. Liberally applying the Natural Gas Law, PV=nRT, when the dampening oil is exposed to a rapid increase in air temperature, the oil’s volume also increases. Another hypothesis is the external air pressure is lower than the oil’s current ambient state – when the garage door is lifted and the lower pressure air rapidly changes in the room, the oil’s responds inversely by increasing its volume. The hypotheses both suggest that a shift in volume pushes on the sensitive instrument’s balancing arm, causing movement which, in turn, is recorded by the instrument’s sensors. The result is an “apparent” ground motion event as shown in the image below.
The takeaway – Scientists are users of their instruments, but they need to be learners of their instrumentation – understanding sources of data uncertainty, false recordings, and detection capabilities.
Please consider giving to “Cultivating Citizen Scientists” program; we purchase educational seismic instruments, mineral specimens, and provide onsite curriculum development with our Professional Scientists and Science Education team members. Each donation is tax-deductible as TXESP is a 501-c3 Non Profit, designated Public Charity.