Decisionmaking in Hospital Earthquake Evacuation: Does Distance From the Epicenter Matter?
Presented at the American College of Emergency Physicians Scientific Assembly Research Forum, October 2004, San Francisco, CA.
Received 9 November 2006; received in revised form 27 February 2007; accepted 26 March 2007. published online 28 April 2007.
Study objective
Over large expanses, the risk for hospital damage from an earthquake attenuates as the distance from the epicenter increases, which may not be true within the immediate disaster zone (near field), however. The following study examines the impact of epicenter distance and ground motion on hospital evacuation and closure for those structures near the epicenter of the 1994 Northridge Earthquake and the implications for patient evacuation.
Methods
This is a retrospective case-control study of all hospitals reporting off-site evacuations or permanent closure because of damage from the January 17, 1994, earthquake in Northridge, CA. Control hospitals were randomly identified from those facilities that did not evacuate patients. Distances from the epicenter and peak ground accelerations were calculated for each hospital from Trinet ShakeMap data and compared.
Results
Eight hospitals evacuated patients (study group); 4 of these hospitals were condemned. These were compared to 8 hospitals that did not evacuate patients (control group). The median epicenter-to-hospital distance for evacuated facilities was 8.1 miles (interquartile range [IQRs] 4.0 to 17.2 miles), whereas that for nonevacuated facilities was 14.1 miles (IRQ 10.5 to 17.0 miles). The difference in the median distances was 6.0 miles (95% confidence interval –4.8 to 11.9 miles). The peak ground acceleration had a median of 0.77g (IQR 0.53 to 0.85g) for study hospitals and a median of 0.36g (IQR 0.24 to 0.50g) for control hospitals, where 1g equals the force of gravity. The difference in median acceleration of 0.41g (95% CI 0.14 to 0.55g) was significant (P=.009).
Conclusion
The distances from the epicenter for evacuated or condemned facilities and control hospitals do not appear to differ in the near field. Peak ground acceleration is a superior indicator of the risk for hospital damage and evacuation. Physicians can obtain these data in real time from the Internet and should transfer patients to facilities in areas of lower recorded peak ground acceleration regardless of distance from the epicenter.
aDepartment of Emergency Medicine, University of California Irvine School of Medicine, Irvine, CA, and the Emergency Department, University of California Irvine Medical Center, Orange, CA
bDivision of Emergency Medicine, David Geffen School of Medicine at University of California Los Angeles, Los Angeles, CA, and Emergency Department, Harbor–University of California Los Angeles Medical Center, Torrance, CA.
Address for correspondence: Carl H. Schultz, MD, Department of Emergency Medicine, UCI Medical Center, Route #128, 101 City Drive, Orange, CA 92668; 714-456-3713, fax 714-456-3714.
Supervising editor: Jonathan L. Burstein, MD
Author contributions: CHS conceived of the idea for the article. CHS and KLK reviewed the literature on the subject. CHS, KLK, and RJL wrote and reviewed the article, as well as the references and the tables. RJL provided statistical support. CHS and KLK takes responsibility for the paper as a whole.
Funding and support: By Annals policy, all authors are required to disclose any and all commercial, financial, and other relationships in any way related to the subject of this article, that may create any potential conflict of interest. See the Manuscript Submission Agreement in this issue for examples of specific conflicts covered by this statement. Study funded by a grant from the National Science Foundation CMS-9416277.
ABSTRACT