T102 Rifts, Rifted Margins, Backarcs, and Spreading Ridges: Understanding Extensional Processes across Tectonic Settings and Time Scales II

Monday, 11 October 2021
1:30 PM - 5:30 PM
B115/B116 (Hybrid Room)

CHARACTERIZING THE SEISMOGENIC POTENTIAL OF ACTIVE FAULTS IN THE WOODLARK RIFT WITH INTEGRATED MULTI-TIMESCALE OBSERVATIONS AND MODELS

Paper number: T102-9
Program: Technical Sessions
Time: 3:15 PM – 3:30 PM

Authors

Abstract

Earthquakes in active rifts pose significant societal hazard, but identifying and characterizing seismically hazardous normal faults can be challenging. Extension rates across active normal faults are typically low (a few mm/yr) and recurrence intervals of large normal fault earthquakes can be correspondingly long (hundreds to thousands of years). Observations from paleoseismology, structural geology, and tectonic geodesy can probe the seismic or aseismic slip behavior of active normal faults that lack a historical or seismological record of large earthquakes. Additionally, seismic cycle and dynamic rupture models can explore the mechanical and frictional conditions that promote large earthquakes for different fault geometries. Integrating multi-timescale geologic and geophysical datasets with physics-based numerical models can further illuminate the seismic hazard potential of interseismically and historically quiet rifts by generating data-constrained rupture scenarios.

In this presentation, we first summarize recent geologic, paleoseismic, geodetic, and experimental friction observations of coseismic-to-tectonic-timescale deformation in the active Woodlark rift of Papua New Guinea, which include evidence for Holocene Mw >7.0 earthquakes. We focus on the western portion of the rift, where new data confirm that extension is localized on the concave-down Mai’iu low-angle normal fault which dips 16-24° at the surface and slips at geodetically inferred dip-slip rates of 8.3 +- 1.2 mm/yr, accommodating rapid rolling-hinge style exhumation of the ~3-km-high Dayman-Suckling metamorphic core complex. In the second part of this talk, we discuss how these new datasets inform our understanding of the regional seismic hazard posed by low-angle normal fault earthquakes, then present preliminary results from 3D data-constrained dynamic earthquake rupture models of the Mai’iu fault.

Geological Society of America Abstracts with Programs. Vol. 53, No. 6

doi: 10.1130/abs/2021AM-368500

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