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Moment rate scaling for earthquakes 3.3 ≤ M ≤ 5.3 with implications for stress drop
Author(s) -
Archuleta Ralph J.,
Ji Chen
Publication year - 2016
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2016gl071433
Subject(s) - scaling , physics , amplitude , attenuation , drop (telecommunication) , seismic moment , ground motion , moment (physics) , magnitude (astronomy) , geodesy , geometry , seismology , mathematics , optics , geology , classical mechanics , astrophysics , telecommunications , fault (geology) , computer science
We have determined a scalable apparent moment rate function (aMRF) that correctly predicts the peak ground acceleration (PGA), peak ground velocity (PGV), local magnitude, and the ratio of PGA/PGV for earthquakes 3.3 ≤ M ≤ 5.3. Using the NGA‐West2 database for 3.0 ≤ M ≤ 7.7, we find a break in scaling of LogPGA and LogPGV versus M around M ~ 5.3 with nearly linear scaling for LogPGA and LogPGV for 3.3 ≤ M ≤ 5.3. Temporal parameters t p and t d —related to rise time and total duration—control the aMRF. Both scale with seismic moment. The Fourier amplitude spectrum of the aMRF has two corners between which the spectrum decays ~ f − 1 . Significant attenuation along the raypath results in a Brune‐like spectrum with one corner f C . Assuming that f C ≅ 1/ t d , the aMRF predicts non‐self‐similar scaling M 0 ∝ f C 3.3 and weak stress drop scaling Δ σ ∝ M 0 0.091 . This aMRF can explain why stress drop is different from the stress parameter used to predict high‐frequency ground motion.