The 2017 M_w 8.2 Chiapas, Mexico, Earthquake: Energetic Slab Detachment

Abstract

On 8 September 2017, a great (Mw 8.2) normal faulting earthquake ruptured within the subducting Cocos Plate ~70 km landward from the Middle American Trench beneath the Tehuantepec gap. Iterative inversion and modeling of teleseismic and tsunami data and prediction of GPS displacements indicate that the steeply dipping rupture extended ~180 km to the northwest along strike toward the Oaxaca coast and from ~30 to 70 km in depth, with peak slip of ~13 m. The rupture likely broke through the entire lithosphere of the young subducted slab in response to downdip slab pull. The plate boundary region between the trench and the fault intersection with the megathrust appears to be frictionally coupled, influencing location of the detachment. Comparisons of the broadband body wave magnitude (mB) and moment‐scaled radiated energy (ER/M0) establish that intraslab earthquakes tend to be more energetic than interplate events, accounting for strong ground shaking observed for the 2017 event.

Intraslab Deformation in the 30 November 2018 Anchorage, Alaska, MW 7.1 Earthquake

“…constrain or monitor than deformation on plate boundaries. Other major intraplate earthquakes of this type have occurred in Chile (e.g., Delouis & Legrand, 2007), Taiwan (e.g., Kanamori et al, 2012), Sumatra (e.g., Wiseman et al, 2012), the Philippines (e.g., Ye et al, 2012), the western Aleutians (e.g., Ye et al, 2014), Mexico (e.g., Melgar et al, 2018;Ye et al, 2017), and in 1949, 1965, and 2001under Washington State (e.g., Bustin et al, 2004. When located below populated areas, such events can be very damaging.…”

Nucleation and Kinematic Rupture of the 2017 Mw 8.2 Tehuantepec Earthquake

“…The stress triggering relation between the foreshock sequence and the mainshock is usually attributed to static stress triggering, dynamic triggering, or aseismic transients such as slow slip or fluid flow. In the case of the Tehuantepec earthquake, several finite fault studies suggest that the principal slip zone extends over a depth range of 25 km (USGS finite fault model; Ye et al, 2017;Okuwaki & Yagi, 2017;Chen et al, 2018;. The static stress change induced by fault rupture drops significantly with distance and becomes negligible when the receiver fault is located over two times the rupture length away (Hill & Prejean, 2007).…”

“…The kinematic rupture processes of the M 8.2 event are characterized by a unilateral northwestward rupture propagation and a principle slip zone deeper than 25 km (Chen et al, 2018;Okuwaki & Yagi, 2017;Ye et al, 2017;Zhang & Brudzinski, 2019). The kinematic rupture processes of the M 8.2 event are characterized by a unilateral northwestward rupture propagation and a principle slip zone deeper than 25 km (Chen et al, 2018;Okuwaki & Yagi, 2017;Ye et al, 2017;Zhang & Brudzinski, 2019).…”

Long‐Lived Tsunami Edge Waves and Shelf Resonance From the M8.2 Tehuantepec Earthquake

“…The 8 September 2017 M8.2 Tehuantepec, Mexico, earthquake ruptured an~150-km high-angle normal fault below the subduction zone megathrust (Chen et al, 2018;Gusman et al, 2018;Ye et al, 2017), from a depth of 20 to 80 km with upward of 12 m of slip ( Figure 1) and with the majority of moment release at~50-km depth. The event is somewhat peculiar because of its mechanism, dominated by extensional stresses within a convergent plate boundary, and because its deep extent implies complete rupture of the lithosphere .…”