Survey of Damaged Tufa Pinnacles in Trona Following the 2019 Ridgecrest Earthquake Sequence

Session: Observations From the 2019 Ridgecrest Earthquake Sequence [Poster]
Type: Poster
Date: 4/28/2020
Time: 08:00 AM
Room: Ballroom
Description: 

Damage to Fragile Geologic Features (FGFs) can help constrain the level of ground motions in the absence of instruments. Durable FGFs such as Precariously Balanced Rocks (PBRs) gained interest in the last few decades for their potential ability to determine the upper-bound limits of ground motions that a region experienced. Observations of damaged PBRs are extremely rare and other FGFs, such as tufa pinnacles, are now explored as a way to develop and test the ground motion evaluation methodologies. As part of the Ridgecrest Sequence reconnaissance field work, we visited the Trona Pinnacles National Monument where hundreds of tufa pinnacles reside. The pinnacles are located within 5 km of the mapped M7.1 fault trace. The pinnacles have been heavily photographed, both by researchers and tourists, and images documenting their pre-damage state are readily available.

We observed evidence of fresh damage on several of the pinnacles, characterized by the white color of the damaged carbonate material composing the tufa, the angularity of the released rocks and fragments, and several observations of displaced soil where tufa fragments have bounced during their fall or at their landing location. We confirmed damage at two pinnacles relative to pre-event pictures and identified several more potentially damaged spires. We documented our observations with geo-located pictures taken from several angles, and captured most the pinnacles reasonably accessible by car or on foot. LiDAR surveys also captured the post-event state of the pinnacles. In addition, selected pinnacles were imaged using structure from motion with the use of small uninhabited aerial Vehicles (sUAVs) and volumes of the observed damaged features have been estimated. We expect that our database of pictures and 3D images can serve as the reference of pre-event state before the next earthquake. We will summarize our data collection and present results of our analyses to date.

Presenting Author: Christine A. Goulet

Authors