Survey of Damage to Road Bridges by the Bohol Island Earthquake in thePhilippines
MABUCHI Toshiaki, Senior Researcher
Earthquake Disaster Prevention Division, Research Center for Disaster Management
Keywords: Bohol Island Earthquake, road bridge, damage survey
1. Introduction
An earthquake of M7.2 occurred on Bohol Island,
Philippines, on October 15, 2013 It caused serious
damage and resulted in 222 deaths, 8 missing persons,and 796 injured (as of the end of October). Since roadbridges also suffered serious damage including collapse
from this earthquake, the Department of Public Worksand Highways of the Philippines Government requested
technical assistance for road bridge restoration to theJapan International Cooperation Agency ("JICA")
hereafter). As requested by JICA, I was dispatched to
the Philippines as a short-term expert to survey thedamage to road bridges from November 18 to 22,
together with Junichi Hoshikuma, senior researcher of theCenter for Advanced Engineering Structural Assessment
and Research (CAESAR), Public Works ResearchInstitute, and Toru Tsuchihashi of the Planning /Coordination Division, Economic Infrastructure
Development Department, JICA.
Note that, on November 4 to 11, 20 days after thisearthquake, Typhoon No. 30 ("Haiyan") passed throughan area about 140 km north of Bohol Island and caused
enormous damage to Leyte and Samal Islands, but nofurther serious damage to the road bridges on Bohol
Island, which was just a short distance away.
2. Outline of the Philippines Bohol Island
Earthquake
The earthquake struck at 8:15 a.m (local time). on
October 15 (Wed.), 2013 with an epicenter in Sagbayan
Town (north latitude 9.86°, east longitude 124.07°'). It
had a magnitude of 7.2 and focal depth of 12 km,
according to the announcements of the Philippine
Institute of Volcanology and Seismology.
On the Island, a reverse fault, which is a concealed
fault different from the existing fault (Bohol Fault), wasfound and named the "Northern Bohol Fault."
The maximum seismic intensity was 7 on the 12-stage
seismic intensity scale of the Philippine, which isequivalent to about an upper 5 on the Japanese intensity
scale.
3. Damage to road bridges
Damage to road bridges occurred on the west side of
the roads running around Bohol Island. We investigated
16 bridges during the survey period. The photo shows thecollapsed Moalong Bridge. The deformation in thesurrounding ground caused the abutment andintermediate abutment to tilt. The bridge girder thencollapsed because of the shortened girder seating. In
many other affected bridges, damage resulting from themovement of the abutment due to the subsidence ofsurrounding ground was seen.
Such form of damage was also seen in the 1990 Luzon
Earthquake 1). It is, therefore, necessary to take seismic
improvement measures including the seismic design ofsubstructure, and bridge collapse prevention measures,according to ground conditions.
4. Conclusions
We promptly reported the survey results to theDepartment of Public Works and Highways of thePhilippines Government, and introduced the seismic
measures in Japan in consideration of the type of damage
to the road bridges in the Philippines. The geographicalenvironment of the Philippines is similar to Japan andlikely to suffer disasters from earthquakes and typhoons.
We hope that this survey will contribute to thedevelopment of disaster-resistant roads in the Philippines.
[Reference]"Report on the 1990 Philippines Luzon Earthquake
Damage Survey," edited by the Japan Society of Civil
Engineers (Earthquake Damage Survey Series 1)

Photo: Damage to Moalong Bridge (Built in 1982)