July 27, 2019 Batanes Post-Earthquake Reconnaissance Report

The two consecutive earthquakes happened at 4:16 AM and 7:37 AM with a magnitude of 5.4 and 5.9 respectively. The earthquakes caused major damage to houses in Itbayat, where most traditional unreinforced limestone masonry houses collapsed, and also damaged government buildings such as schools, the town hall and hospital.

The team from Build Change and Philippine Red Cross arrived in Itbayat, Batanes on October 2, 2019 for a weeklong survey. Key findings include: 

• Residents were already rebuilding their temporary shelters since financial aid from the government had been released and construction materials were being distributed. 
• The most common house typologies are unreinforced limestone masonry, reinforced concrete and light timber houses. 
• Most of the unreinforced limestone masonry houses totally collapsed during the earthquake and a few reinforced concrete houses suffered out of plane failure of gable wall and wall cracks. 
• Most of the totally collapsed traditional unreinforced limestone masonry houses were already demolished and cleared when we arrived. Factors that caused the collapse of these houses include the poor quality of material used, age of the house and subjection to numerous tropical storms over the years, which would likely have caused the limestone to erode over time and consequently weakened the walls’ ability to withstand an earthquake. 
• The most common failure observed was the out of plane failure of wall. These walls do not have ring beams, horizontal bands, vertical bands or buttresses, anchors to the roof, or other types of framing typically used to brace unreinforced masonry wall out-of-plane.