accelerographs

An accelerograph is a seismic instrument that records ground acceleration during earthquakes and other ground motions. It is designed to capture high-amplitude, short-period motions with fidelity sufficient for engineering analysis, and its recordings are known as accelerograms.

Operation typically involves a moving inertial mass attached to a fixed frame by a spring and damper, or a solid-state inertial sensor. When the ground moves, the frame and mass accelerate differently, and sensors measure the relative motion as acceleration. Modern devices use electronic accelerometers, such as capacitive or piezoelectric sensors, linked to a data logger. They sample at rates from tens to hundreds of samples per second and cover a wide dynamic range to record both weak ambient motion and strong seismic shaking.

The instrument output is an acceleration time history, which may be corrected for instrument response and filtering. Through numerical integration, velocity and displacement time histories can be estimated, though this is sensitive to baseline and drift corrections. Data are stored in standard formats and shared in seismic networks for comparative analysis.

Applications include strong-motion seismology and structural engineering. Accelerographs are used to characterize site effects, calibrate ground-motion prediction equations, and inform the seismic design of buildings, bridges, and critical facilities. They are deployed in dense regional networks, boreholes, and on individual structures to capture motion across a range of magnitudes and distances.

Types and deployment vary in axis configuration (single-axis or three-axis), ruggedization, and installation mode (surface, borehole, or embedded in a structure). Strong-motion accelerographs are designed to withstand large motions and provide accurate recordings over wide amplitudes.