A High‐Frequency Distance Metric in Ground‐Motion Prediction Equations Based on Seismic Array Backprojections

Abstract

Typical ground‐motion prediction equations (GMPEs) measure source‐to‐site distances relative to the closest point on the rupture plane (Rrup). However, for megathrust earthquakes (Mw > 8), the oversimplification of the earthquake source characteristics in distance metrics results in significant bias. Recent studies suggest that the high‐frequency (HF) and low‐frequency (LF) energy tend to emanate from different portions of the megathrusts. This phenomenon motivates an alternative distance metric based on the array backprojection imaging technique that effectively captures regions releasing HF energy. Herein, we define an HF distance metric (Rhf) as the distance from the site to the high‐frequency radiation zone. We study five Mw > 7.2 megathrust earthquakes in Japan and Chile and find that Rhf outperforms Rrup in predicting the ground shaking intensity between 0.5 and 4 Hz. We consider Rhf as a complementary measure to conventional GMPE distance metrics and a more accurate ground‐motion predictor in many cases.

Early and persistent supershear rupture of the 2018 magnitude 7.5 Palu earthquake

“…Such agreement was first achieved for the 2013 Mw 7.7 Balochistan earthquake (Avouac et al, 2014). Real-time automated BP has been proposed to complement earthquake and tsunami early warning (Meng et al, 2014;An and Meng, 2016) and rapid ground-motion estimations (Feng and Meng, 2018). The slowness correction pre-determined with background earthquakes is an important consideration for such applications.…”

Source Imaging With a Multi‐Array Local Back‐Projection and Its Application to the 2019Mw6.4 andMw7.1 Ridgecrest Earthquakes

“…The BP results are made without any assumption of fault geometry. The sources of relatively high‐frequency radiation are complementary to previous studies and more related to strong motion generations (Feng & Meng, 2018; Meng et al., 2014). The choice of the array configurations (size, distance range) and processing parameters (frequency, window length) can be used to optimize future applications of earthquake source imaging.…”

Physically Based and Empirical Ground Motion Prediction Equations for Multiple Intensity Measures (PGA, PGV, Ia, FIV3, CII, and Maximum Fourier Acceleration Spectra) on Sakhalin Island

“…Furthermore, by substituting ( 13) into (19), following the elementary transformations, we obtained the subsequent expression:…”

“…Hypocentral distance (Rhyp) is quite suitable for point-source models, while other measures, such as Rrup (the closest distance between the site and the three-dimensional rupture plane) and Rjb (the shortest distance from a site to the surface projection of the rupture plane), are most commonly used for finite sources. The role of high-frequency radiation is also reflected in modified distance metrics (e.g., [19]).…”