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A Growing Catalogue of Short-Period Earthquake Rupture Histories From Multi-Array Back-Projection

Description: 

For large earthquakes, the distribution of the high intensity zone depends to first order on the direction and length of rupture propagation. Furthermore, the speed of rupture propagation has a major influence through directivity effects. Of particular concern are rupture segments propagating at supershear speeds, which emit a shockwave-like pulse in the forward direction. Teleseismic back-projection imaging has emerged as a powerful tool for constraining the rupture propagation of large earthquakes with relatively little user input and capturing the high-frequency behavior of the fault, which is most relevant for impact, at least for most building types. However, its application often suffers from artifacts related to the receiver array geometry. We developed a teleseismic backprojection technique that can accommodate data from multiple arrays. Combined processing of P and pP waveforms may further improve the resolution. The method is suitable for defining arrays ad-hoc to achieve a good azimuthal distribution. We present a catalog of short-period rupture histories (0.5–2.0 Hz) for all earthquakes from 2010 to 2023 with Mw ≥ 7.5 and depth less than 200 km (62 events). The method provides automatic estimates of rupture length, directivity, speed, and aspect ratio, a proxy for rupture complexity. We obtained short-period rupture length scaling relations that are in good agreement with previously published relations based on total slip. Rupture speeds were consistently in the sub-Rayleigh regime for thrust and normal earthquakes, whereas a tenth of strike-slip events propagated at supershear speeds. Many rupture histories exhibited complex behaviors, e.g., rupture on conjugate faults, bilateral propagation, and dynamic triggering by a P wave. For megathrust earthquakes, ruptures encircling asperities were frequently observed, with down-dip, up-dip, and balanced patterns, with emissions up-dip of the main asperity more common than suggested by earlier publications. In the presentation, we will also consider the realtime potential of the algorithm.

Session: Creating Actionable Earthquake Information Products - I

Type: Oral

Date: 5/1/2024

Presentation Time: 09:00 AM (local time)

Presenting Author: Frederik

Student Presenter: No

Invited Presentation: 

Authors