Using centroid time-delays to characterize source durations and identify earthquakes with unique characteristics

Abstract

The relationship between M_0 and the rupture duration is often difficult to establish. This is particularly true for large earthquakes for which the moment rate functions (MRF) generally have complicated shapes, and the estimated durations can vary considerably depending on the methodology used to evaluate the MRF. In this work, we show that the centroid time-delay (τ_c) provides an alternative estimate of the source duration. Inverted MRFs often end gradually, making the end of coseismic rupture difficult to detect. In such cases, when the rupture duration is not well defined, the time-delay τ_c is a useful quantity to represent the first-order temporal characteristics of the rupture process. Variations in stress parameter Δσ can be investigated by assuming a standard scaling relationship between the seismic moment M0M0 and τ_c .This simple scaling relationship can also be used to identify unusual earthquakes, with unique source properties, such as events involving complicated rupture processes or earthquakes characterized by unusual rupture velocities, stress drops or aspect ratios.