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Variations in Seismogenic Thickness Along the Central Alpine Fault, New Zealand, Revealed by a Decade's Relocated Microseismicity

journal contribution
posted on 09.02.2021, 07:33 by K Michailos, EGC Smith, Calum Chamberlain, Martha Savage, John Townend
©2018. American Geophysical Union. All Rights Reserved. The Alpine Fault is an oblique strike-slip fault that is known to fail in large magnitude (M7–8) earthquakes, yet it is currently seismically quiescent. We examine the low-magnitude earthquake activity occurring along the central portion of the Alpine Fault using seismic data from five temporary seismic networks deployed for various lengths of time between late 2008 and early 2017. Starting from continuous seismic data, we detect earthquake arrivals and construct the longest and most extensive microearthquake catalog for the central Alpine Fault region to date, containing 9,111 earthquakes. This enables us to study the distribution and characteristics of the seismicity in unprecedented detail. Earthquake locations are constrained by high-quality automatic and manual picks, and we perform relocations using waveform cross-correlation to better constrain hypocenters. We have derived a new local magnitude scale calibrated by M w values. Magnitudes range between M L −1.2 and 4.6, and our catalog is complete above M L 1.1. Earthquakes mainly occur southeast of the Alpine Fault (in the hanging wall) and exhibit low magnitudes. We observe a lack of seismicity beneath Aoraki/Mount Cook, which we associate with high uplift rates and high heat flow. Seismogenic cutoff depths vary along the strike of the Alpine Fault from 8 km, beneath the highest topography, to 20 km in the adjacent areas.

Funding

Locked and Loaded? Effects of Deep Seismic and Aseismic Deformation on Alpine Fault Earthquakes | Funder: ROYAL SOCIETY OF NEW ZEALAND | Grant ID: 13-VUW-101

History

Preferred citation

Michailos, K., Smith, E. G. C., Chamberlain, C. J., Savage, M. K. & Townend, J. (2019). Variations in Seismogenic Thickness Along the Central Alpine Fault, New Zealand, Revealed by a Decade's Relocated Microseismicity. Geochemistry, Geophysics, Geosystems, 20(1), 470-486. https://doi.org/10.1029/2018GC007743

Journal title

Geochemistry, Geophysics, Geosystems

Volume

20

Issue

1

Publication date

01/01/2019

Pagination

470-486

Publisher

American Geophysical Union (AGU)

Publication status

Published

Online publication date

29/01/2019

ISSN

1525-2027

eISSN

1525-2027

Language

en

Exports