Analysis of Intraslab Predigital Earthquakes of the South-Central Alaska Region

Abstract I compare intensity data from 17 predigital intraslab earthquakes in south-central Alaska and digitized waveforms for nine of these events to similar data for the 24 January 2016 Iniskin and 30 November 2018 Anchorage intraslab events. Both the 2016 and 2018 events were associated with amplification of strong ground motion at distances of over 100 km from their epicenters, likely due to the velocity structure associated with flat slab subduction in the region as well as the thick sedimentary sequence found within the Cook Inlet basin. Six of the predigital events also appear to have similar amplification of strong ground motion. Waveform comparisons suggest the 4 May 1934 Prince William Sound and 3 October 1954 Kenai Peninsula events had similar focal mechanisms and depths to the 30 November 2018 Anchorage event. Earthquakes occurring in regions where the P-wave velocity of the slab exceeds 7.5 km/s tend to be associated with higher strong ground motions.

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Velocity Structure Models and Strong Ground Motion Simulations

Zisin (Journal of the Seismological Society of Japan 2nd ser ) ◽

10.4294/zisin.61.441 ◽

2009 ◽

Vol 61 (Supplement) ◽

pp. 441-453

Author(s):

Kazuki KOKETSU ◽

Hiroe MIYAKE

Keyword(s):

Ground Motion ◽

Strong Ground Motion ◽

Velocity Structure ◽

Ground Motion Simulations ◽

Strong Ground

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Modeling of Subsurface Velocity Structures from Seismic Bedrock to Ground Surface in the Tokai Region, Japan, for Broadband Strong Ground Motion Prediction

Journal of Disaster Research ◽

10.20965/jdr.2019.p1140 ◽

2019 ◽

Vol 14 (9) ◽

pp. 1140-1153

Author(s):

Atsushi Wakai ◽

Shigeki Senna ◽

Kaoru Jin ◽

Atsushi Yatagai ◽

Haruhiko Suzuki ◽

...

Keyword(s):

Ground Motion ◽

Strong Ground Motion ◽

Velocity Structure ◽

Ground Surface ◽

Disaster Mitigation ◽

Motion Prediction ◽

Ground Motion Prediction ◽

Strong Ground Motion Prediction ◽

Tokai Region ◽

Strong Ground

For sophistication of strong ground motion prediction in terms of disaster mitigation, one of the principal issues is to model subsurface velocity structures so that characteristics of earthquake ground motions can be reproduced in the broadband range 0.1 Hz to 10 Hz. In recent years, subsurface structures have been modeled in sedimentary layers on seismic bedrock for a few regions of Japan, in a national project. In this study, subsurface velocity structures were modeled from seismic bedrock to the ground surface for the Tokai region. These models were constructed in accordance with the subsurface velocity structure modeling scheme published by the Headquarters for Earthquake Research Promotion. To begin with, initial models were constructed based on existing bore-hole data, geological information, etc. Next, they were improved based on results of microtremor explorations which had been conducted in recent years. It was found that the new model had different characteristics to the conventional model. This paper will present the modeling process and characteristics of distribution maps for velocity structures and amplification index.

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