47 JULY 2025 WorldWide Drilling Resource® Blasting Seismographs Adapted from Information by the International Society of Explosives Engineers (ISEE) Blasting seismographs play a crucial role in ensuring adherence to regulations designed to protect both public and private property from potential harm. The effectiveness of these regulations heavily relies on the precision of the data regarding ground vibrations and air overpressure data. A key objective of the ISEE Standards Committee is to promote uniformity and accuracy in the measurement of these factors across all blasting seismographs. The precision of recordings is vital in this context. Specific guidelines outline responsibilities of manufacturers when constructing and calibrating blasting seismographs intended for outdoor field applications to monitor ground vibrations and air overpressures. These measurements must facilitate comparisons with the limiting criteria established in the United States Bureau of Mines reports RI 8507 and RI 8485, which frequently serve as foundational regulations for blast vibrations. It is essential blasting seismographs are installed in the field in accordance with the ISEE Field Practice Guidelines for Blasting Seismographs (ISEE 2015). A seismograph is equipped with two types of sensors: a geophone, which is responsible for detecting ground waves, and a microphone, which captures air waves. The geophone is designed to measure ground motion across three dimensions: j Vertical: This measures movement in the up-and-down direction. j Longitudinal: This tracks motion forward and backward relative to the blast. j Transverse: This captures side-toside movements. Meanwhile, the microphone is tasked with measuring air overpressure, which refers to the excess pressure created by a blast that surpasses normal atmospheric levels. The calibration documentation must demonstrate each channel of the seismograph being calibrated complies with or exceeds the ISEE Performance Specifications for Blasting Seismographs. To ensure compliance, the seismograph needs to be tested across the full frequency range of 2 to 250 hertz. Certain specifications, such as cross-talk response, sensor density, and the microphone’s reaction to mechanical vibrations, tend to remain consistent over time and can usually be found on product specification sheets. However, the frequency, amplitude, and phase responses are critical to the accuracy of recorded events and must be thoroughly verified as part of the calibration process. The frequency, amplitude, and phase responses of a blast seismograph are influenced by the specific components utilized in its circuit design. Over time, these components may change, drift, or even fail, potentially impacting the seismograph’s response and accuracy. To ensure optimal performance, each seismograph, along with its ground vibration and air overpressure sensors, should undergo calibration before its initial use, annually thereafter, and following any repairs that could affect its performance. Since calibration procedures can vary among manufacturers, it is advisable to send the seismograph to the manufacturer or an authorized calibration facility for the annual calibration. EXB 2025 Booth 1506
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