Afterslip Moment Scaling and Variability From a Global Compilation of Estimates

Area of Science:

• Geophysics and seismology, focusing on earthquake physics and hazard assessment.

Background:

• Aseismic afterslip, or postseismic fault sliding, redistributes crustal stresses and can trigger aftershocks.
• Current afterslip modeling relies on case-by-case geodetic data, limiting understanding of moment variation across earthquakes.

Purpose of the Study:

• To systematically analyze the variation in aseismic afterslip moment relative to mainshock moment.
• To identify factors influencing the ratio of afterslip to coseismic moment (M_SS/M_C).

Main Methods:

• Compilation and analysis of 148 afterslip studies for 53 earthquakes (M >= 6.0).
• Formal analysis of 88 well-constrained kinematic models to quantify scaling relationships and correlations.

Main Results:

• Afterslip and coseismic moments exhibit a near-linear scaling relationship (median CC = 0.91).
• The ratio M_SS/M_C varies widely (9%-32% IQR) and shows weak correlations with rupture aspect ratio and fault slip rate.
• No significant correlation was found between M_SS/M_C and mainshock properties (dip, rake, depth) or observation duration.

Conclusions:

• While mainshock moment is a primary control, other factors like fault maturity and rupture complexity influence afterslip magnitude.
• Significant modeling uncertainties currently challenge systematic analysis and the development of predictive afterslip models.
• Standardizing modeling practices is crucial for improving comparability and integrating afterslip into hazard assessments.