Peak horizontal acceleration and velocity from strong-motion records including records from the 1979 imperial valley, California, earthquake

TLDR

The study aims to decouple distance and magnitude dependence in attenuation relations for peak horizontal acceleration and velocity. Using a large set of close‑distance strong‑motion records, the authors developed magnitude‑independent attenuation curves based on geometrical spreading and anelastic attenuation, and introduced a technique that separates distance effects from magnitude effects. The resulting equations, log A = −1.02 + 0.249 M − log r − 0.00255 r + 0.26 P and log V = −0.67 + 0.489 M − log r − 0.00256 r + 0.17 S + 0.22 P, provide peak horizontal acceleration and velocity predictions for 5.0 ≤ M ≤ 7.7 and 5.3 ≤ M ≤ 7.4, respectively, and the magnitude‑independent shape was preferred over a magnitude‑dependent one.

Abstract

Abstract We have taken advantage of the recent increase in strong-motion data at close distances to derive new attenuation relations for peak horizontal acceleration and velocity. This new analysis uses a magnitude-independent shape, based on geometrical spreading and anelastic attenuation, for the attenuation curve. An innovation in technique is introduced that decouples the determination of the distance dependence of the data from the magnitude dependence. The resulting equations are log A = − 1.02 + 0.249 M − log r − 0.00255 r + 0.26 P r = ( d 2 + 7.3 2 ) 1 / 2 5.0 ≦ M ≦ 7.7 log V = − 0.67 + 0.489 M − log r − 0.00256 r + 0.17 S + 0.22 P r = ( d 2 + 4.0 2 ) 1 / 2 5.3 ≦ M ≦ 7.4 where A is peak horizontal acceleration in g, V is peak horizontal velocity in cm/ sec, M is moment magnitude, d is the closest distance to the surface projection of the fault rupture in km, S takes on the value of zero at rock sites and one at soil sites, and P is zero for 50 percentile values and one for 84 percentile values. We considered a magnitude-dependent shape, but we find no basis for it in the data; we have adopted the magnitude-independent shape because it requires fewer parameters.