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Analog-to-digital conversion as a source of drifts in displacements derived from digital recordings of ground acceleration

David M. Boore
Analog-to-digital conversion as a source of drifts in displacements derived from digital recordings of ground acceleration
Bulletin of the Seismological Society of America (October 2003) 93 (5): 2017-2024

Abstract

Displacements obtained from double integration of digitally recorded ground accelerations often show drifts much larger than those expected for the true ground displacements. These drifts might be due to many things, including dynamic elastic ground tilt, inelastic ground deformation, hysteresis in the instruments, and cross feed due to misalignment of nominally orthogonal sensors. This article shows that even if those effects were not present, the analog-to-digital conversion (ADC) process can produce apparent "pulses" and offsets in the acceleration baseline if the ground motion is slowly varying compared with the quantization level of the digitization. Such slowly varying signals can be produced by constant offsets that do not coincide with a quantization level and by near- and intermediate-field terms in the wave field radiated from earthquakes. Double integration of these apparent pulses and offsets leads to drifts in the displacements similar to those found in processing real recordings. These effects decrease in importance as the resolution of the ADC process increases.


ISSN: 0037-1106
EISSN: 1943-3573
Coden: BSSAAP
Serial Title: Bulletin of the Seismological Society of America
Serial Volume: 93
Serial Issue: 5
Title: Analog-to-digital conversion as a source of drifts in displacements derived from digital recordings of ground acceleration
Author(s): Boore, David M.
Affiliation: U. S. Geological Survey, Menlo Park, CA, United States
Pages: 2017-2024
Published: 200310
Text Language: English
Publisher: Seismological Society of America, Berkeley, CA, United States
References: 23
Accession Number: 2004-016011
Categories: Seismology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute.
Update Code: 200405
Program Name: USGSOPNon-USGS publications with USGS authors
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