FIGURE 4.1 Plot of acceleration amplitude versus frequency, showing effective bandwidth and dynamic range for current broadband, high-frequency, and low-gain (strong-motion) digital seismometers, as well as for the older short-period and long-period analog seismometers of the World Wide Standardized Seismographic Network. Broadband instruments are capable of faithfully recording ground motions ranging from ambient noise at quiet sites (line labeled low Earth noise) to the peak accelerations generated by an M 9.5 earthquake at an epicentral distance of 3000 kilometers (upper line of stars). Low-gain seismometers are needed to record ground accelerations in the damage zones of large earthquakes, which can exceed 1g, and high-frequency seismometers are needed for periods less than about 0.1 second. SOURCE: R. Butler, IRIS.



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