Highlights of Tall Buildings in Los Angeles and San Diego Shaken at Epicentral Distances ~200 Km or More by the 5 July 2019 M7.1 Ridgecrest, California Earthquake

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

The 5 July 2019 Mw7.1 Ridgecrest, California earthquake shook several instrumented tall buildings (greater than or equal to 10 stories tall) in Los Angeles and San Diego, located approximately 200 and 350 km away from the epicenter, respectively.

This cursory study summarizes the characteristics of a few of the tall buildings affected by the far field event, including a 71-story (California tallest) building and a 51-story building, both in Los Angeles. Most of the tall buildings in Los Angeles had input peak accelerations of approximately 0.015 g at either the base or ground level and peak structural accelerations less than or equal to 0.10 g. In San Diego, corresponding accelerations were approximately 0.006 g and less than 0.05g, respectively. At these levels, none of the buildings suffered damage, though damage reconnaissance was not conducted in either city (to current knowledge of the author).

The recorded response data from these instrumented buildings were examined to determine if basin effects were significant during this earthquake. Dynamic response characteristics were extracted from the recorded responses of the buildings. In particular, critical damping percentages were determined and compared with those used in design practice in the USA and Japan.

Also included in the study were discussion of basin effects and transfer function computations for the downtown Los Angeles buildings with the aim of comparing the site transfer function frequencies using deep V_S - profiles and fundamental frequencies of the tall buildings from building response data recorded during the Ridgecrest mainshock. The comparison shows that the tall Los Angeles buildings have fundamental frequencies (0.12-0.25 Hz) well within the range of site frequency estimated from the deep velocity structure (depth-V_S) profiles.

Presenting Author: Mehmet Celebi

Authors