Toward Understanding Subtle Instrumentation Effects Associated with Weak Seismic Events in the Near Field

• DOI: 10.1785/0120090087
• Publication Date: 2010-01-29T17:42:08Z
• Authors: J. Zahradnik; A. Plesinger
• Keywords: Instrumentation

Abstract Broadband observations of small earthquakes at short epicentral distances reveal a mixture near-field effects and instrumental artifacts. We investigated these phenomena station equipped with an STS-2 CMG-40T sensor situated almost above shallow M 3.0 to 3.8 events (peak ground acceleration 2×10 -1 m/sec 2 ). The horizontal components were systematically accompanied by tiltlike disturbances, the tilt obtained from records exceeded more than 10 times values predicted source model. also observed so far uncommonly recognized type disturbance, whose shape is first derivative disturbance. most likely explanation seems be clipping high-frequency signal peaks within system. A computational model broadband feedback velocimeter as linear dynamic system saturation proved this interpretation on qualitative level. Generally, any asymmetry in transfer high frequencies would produce long-period disturbance type. Users near-fault velocigrams may numerically simulate without knowledge their physical nature, subtract them records. decontaminated still have strange, bow-shaped form, related ramp static displacement (of order 1×10 -5 m article). studied article seem general character, for apparently feedback-controlled velocimeter.