Revisiting Visible Ground Roll
Description:
Observations of seeing the ground undulate during earthquakes goes back to the earliest days of earthquake observations. Visible ground roll (VGR) was included in early descriptions of earthquake intensity scales. Wood and Newman’s Modified Mercalli Scale of 1931 has the wording “Waves seen on ground surfaces” as an indicator of intensity XII shaking. In more recent renditions of macrointensity, ground roll has fallen by the wayside as a strong motion indicator. It did not make it into the Coast and Geodetic Survey’s postal questionnaire developed in 1928 or the subsequent version used by the USGS when they took over compiling U.S. earthquake data in the 1970s. The “Did You Feel It?” questionnaire currently used to collect and tabulate felt reports does not include a VGR question and some scientists have questioned the validity of such reports. We became interested in VGR in our re-examination of the M6.4 1954 Fickle Hill earthquake. As part of that study, we requested reminiscences of the earthquake in local newspapers and social media. We received over 40 reports from people who were between the ages of 3 and 14 when the earthquake occurred. Their descriptions of chimneys toppling and other strong motion indicators were used along with newspaper reports to revise the location and depth of the earthquake. An unexpected outcome of these reports was the prevalence of VGR observations. More than half of our observers who were outside at the time of the earthquake recalled seeing the ground move like “waves on the ocean” and one person who was indoors saw the hallway of her home undulate. In this study we compile a partial catalog of credible reports of VGR, examine how VGR relates to other macroseismic indicators, and whether source characteristics such as depth and focal mechanism may influence these observations.
Session: New Frontiers in Seismic Observations and Modeling with Innovative Methods and Emerging Data on Earth and Other Planets [Poster]
Type: Poster
Date: 4/17/2026
Presentation Time: 08:00 AM (local time)
Presenting Author: Margaret Hellweg
Student Presenter: No
Invited Presentation:
Poster Number: 112
Authors
Lori Dengler Corresponding Author lad1@humboldt.edu California State Polytechnic University, Humboldt |
Margaret Hellweg Presenting Author hellweg@berkeley.edu Berkeley Seismological Laboratory |
Susan Hough hough@usgs.gov U.S. Geological Survey |
Douglas Dreger ddreger@berkeley.edu Berkeley Seismological Laboratory |
Robert McPherson rm4@humboldt.edu California State Polytechnic University, Humboldt |
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Revisiting Visible Ground Roll
Category
New Frontiers in Seismic Observations and Modeling with Innovative Methods and Emerging Data on Earth and Other Planets