Why isn the seismograph reading taken inside the home?
The interior measurements represent “structure” motion and are not considered the same. In many cases the vibration levels measured within the home are less. Research on the effects of blast vibration upon structures has been conducted while recording the blast vibration on the ground, outside of the structure, and usually in the area of the closest portion of the structure to the blast. Vibration recording by the United States Bureau of Mines and many other individual researchers, over many years, with many structures, has allowed those researchers to observe, and predict with a very high degree of certainty, how typical residential-type structures respond to blast vibration. Further seismograph standards are based upon exterior ground vibration levels which take into account the structure’s response to vibration. The measurements on the exterior also allow for consistency. The geophone or transducer (sensor of the seismograph) is attached and secured by spiking, burying or other phys
