Seismic response of rock towers at the trona pinnacles (U.S.A.) to the 2019 Ridgecrest earthquake sequence: theory, observations, and models
File(s)
Published version
Author(s)
Suarez, Joaquin Garcia
McPhillips, Devin
Asimaki, Domniki
Type
Journal Article
Abstract
We analyze the seismic response of a class of fragile geologic features (FGFs), referred to as rock towers (RTs) at the Trona Pinnacles, a group of RTs in southern California that suffered strong shaking during the 2019 Ridgecrest earthquake sequence. FGFs, including RTs, may provide maximum constraints on past earthquake shaking intensity, and thereby support probabilistic seismic hazard assessments (PSHAs). In a rare case study, we explore the hypothesis that RT structural integrity is time dependent, as damage accumulates progressively. We develop finite‐element method (FEM) models of the RTs using photogrammetric shape models. We validate the models by comparing numerical simulations of their response to broadband ground shaking with low‐intensity seismic recordings obtained at the Pinnacles. Results of our simulations are in good agreement with the seismic recordings of actual earthquake aftershocks. We next use the results of the FEM models to analyze the response and evolution of RTs. Our analyses elucidate the influence of geometry over their seismic response, providing a rationale that may explain the rarity of slender RTs at Trona: high‐aspect‐ratio structures that respond in bending develop detrimental tensile stresses that crack the rock, whereas low‐aspect‐ratio ones’ response also includes shearing, which does not compromise material integrity as much as tension. Field measurements with a rebound hammer support this finding, suggesting that the material around the base of slender rocks has been weakened relative to other parts of the RT. We also study how to define simplified mechanical models (“archetypes”) to predict the natural frequencies of RTs. Results from our work illuminate the fundamental mechanisms of seismic response and progressive failure of RTs, and open new avenues of research to potentially incorporate these geologic features as long‐return period constraints on PSHA, in ways analogous to those of the widely used precariously balanced rocks.
Date Issued
2025-12-01
Date Acceptance
2025-09-01
Citation
Bulletin of the Seismological Society of America, 2025, 115 (6), pp.2769-2792
ISSN
0037-1106
Publisher
Seismological Society of America
Start Page
2769
End Page
2792
Journal / Book Title
Bulletin of the Seismological Society of America
Volume
115
Issue
6
Copyright Statement
© 2025. The Authors. This is an open access article distributed under the terms of the CC-BY license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
License URL
Subjects
CONSTRAINTS
DOMAIN REDUCTION METHOD
FAULT
Geochemistry & Geophysics
GROUND MOTION
INDICATORS
LOCALIZED REGIONS
PARAMETERS
PGV
Physical Sciences
Science & Technology
SEARLES LAKE
SUBCRITICAL CRACK-GROWTH
Publication Status
Published
Date Publish Online
2025-09-08