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Extreme Accelerations During Earthquakes Caused by Elastic Flapping Effect
Hiroyuki Goto1, Yoshihiro Kaneko2, John Young2
1Disaster Prevention Research Institute, Kyoto University, Uji, Kyoto, 6110011, Japan. goto@catfish.dpri.kyoto-u.ac.jp.
Scientific Reports
|February 6, 2019
Summary
Extremely high accelerations recorded during the Kaikoura earthquake were not actual ground shaking. Numerical simulations reveal a local "flapping effect" of the sensor
Area of Science:
- Geophysics
- Seismology
- Earthquake Engineering
Background:
- Accurate recording of earthquake-induced ground motion is vital for understanding earthquake physics and seismic hazard assessment.
- The magnitude 7.8 Kaikoura earthquake in New Zealand generated extremely large accelerations (3.2g) at seismic station WTMC, the cause of which is not well understood.
Purpose of the Study:
- To investigate the physical mechanisms responsible for the exceptionally large accelerations recorded during the Kaikoura earthquake.
- To determine if the recorded accelerations represent true ground shaking or a local sensor response.
Main Methods:
- Utilized numerical simulations to test various physical models against the observed acceleration data.
- Analyzed asymmetric, vertical acceleration records, comparing them with data from a magnitude 6.3 earthquake.
Main Results:
- The observed asymmetric, vertical accelerations can be explained by a "flapping effect"—the local, elastic bouncing of the sensor's foundation slab.
- The extremely large accelerations at WTMC are likely a result of this local system response, not actual ground shaking.
Conclusions:
- The recorded extreme accelerations at WTMC during the Kaikoura earthquake were artifacts of local sensor system response, not indicative of true ground motion.
- Findings impact seismic hazard evaluations using Kaikoura earthquake data and inform best practices for installing strong-motion seismometers globally.
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