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THE 2013 OCTOBER 15

M7.2 BOHOL EARTHQUAKE

COMPREHENSIVE REPORT

(POST-DISASTER ASSESSMENT)

Prepared by:

QUIAPO CHURCH DISASTER RISK REDUCTION

AND MANAGEMENT MINISTRY (QCDRRM)

27 November 2013

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BACKGROUND

The Province of Bohol is a first income class island province of the Philippines located in the Central Visayas region, consisting of Bohol Island and 75 minor surrounding islands. Its capital is Tagbilaran City. With a land area of 4,117.26 square kilometers (1,589.68 sq mi) and a coastline 261 kilometres (162 mi) long, Bohol is the tenth largest island of the Philippines. To the west of Bohol is Cebu, to the northeast is the island of Leyte and to the south, across the Bohol Sea is Mindanao.

The province is a popular tourist destination with its beaches and resorts. The Chocolate Hills, numerous mounds of limestone formations, is the most popular attraction. The formations can be seen by land (climbing the highest point) or by air with ultralight airplane tours. Panglao Island, located just southwest of Tagbilaran City, is famous for its diving locations and routinely listed as one of the top ten diving locations in the world. Numerous tourist resorts dot the southern beaches and cater to divers from around the world. The Philippine Tarsier, considered the second-smallest primate in the world, is indigenous to the island.

A narrow strait separates the island of Cebu and Bohol and both share a common language, but the Boholanos retain a conscious distinction from the Cebuanos. Bohol's climate is generally dry, with maximum rainfall between the months of June and October. The interior is cooler than the coast.

On 15 October 2013, an earthquake of tectonic origin with magnitude of 7.2 hit Bohol and nearby provinces in Region VII (Central Visayas) at 8:12 a.m. Based on preliminary intensity reports, the strongest ground shaking at PEIS VII was felt at Tagbilaran City and several cities in the province of Cebu. Neighboring island provinces of Cebu, Negros Occidental, Negros Oriental, Camiguin, Panay, Leyte, and several areas in northeastern Mindanao felt the earthquake at varying intensities of PEIS I-VI.

Why do earthquakes occur in Bohol?

Bohol Island is one of the seismically active areas in the country. Instrumental monitoring of earthquakes for the past century has detected many small to moderate-magnitude earthquakes in Bohol Island. There is at least one known earthquake generator on the island, the East Bohol Fault. In addition, there are other local faults which can be sources of small to large magnitude earthquakes. Earthquakes can also occur offshore or undersea because of local offshore faults near the island or trenches in the vicinity of the region.

Moderate-magnitude (M5 to 6.9) earthquakes have also affected Bohol Island in the past!

On 08 February 1990, a magnitude 6.8 earthquake occurred at Bohol generated by an offshore reverse fault east of the island. Sixteen municipalities felt the strongest intensity of ground shaking at PEIS VIII. There were reports of severe property damages, numerous casualties, hundreds injured, and several thousands homeless. The towns of Jagna, Duero, Guindulman, Garcia Hernandez, and Valencia experienced tsunami inundation.

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Aside from strong ground shaking, what other seismic hazards are life-threatening?

Landslides, rock falls, and other types of mass movement may occur in mountainous or hilly areas. Liquefaction, manifested by sandboils or lateral spreading may affect low-lying, water-saturated, sandy areas near the coast or at the banks of rivers. In general, since the destructive earthquake occurred inland, no tsunami was generated.

GEOLOGIC HAZARDS AND IMPACTS OF THE MAGNITUDE 7.2 BOHOL EARTHQUAKE

The earthquake produced 1) a surface rupture, 2) strong ground shaking, 3) liquefaction, and 4) landslide. Several sinkholes also appeared after the earthquake. Considerable to severe damage to infrastructures and houses were reported and observed in the north- and south-western municipalities of Bohol, including Maribojoc, Loon, Tubigon, Calape, Clarin Inabanga, Buenavista, Danao, Sagbayan, Catigbian, San Isidro, Antequerra, Balilihan and Cortes. These towns were also the areas that felt the strongest ground shaking at PEIS VII-VIII (destructive to very destructive ground shaking). Damage to houses and infrastructures were also reported in Tagbilaran and in the southern munipalities of Loboc, Carmen, Lila, Valencia, Albuquerque, Baclayon and Loay.

Surface Rupture (from PHIVOLCS website)

The Mw7.2 Bohol Earthquake was generated on the north-western sector of Bohol island by a NE-SW trending reverse fault (hereto named as North Bohol Fault or NBF), which had no previous surface manifestation. The PHIVOLCS Quick Response Team (QRT) measured surface ruptures ranging from 0.10 meter to as much as 5 meters in vertical displacements exposed in Brgy. Anonang in Inabanga Municipality. As of this writing, the mapped surface of the NBF is 6 kilometers long, from Brgy. New Anonang in Buenavista to Brgy. Napo in Inabanga. The NBF generally trends N40E and dips at 50SE. The PHIVOLCS QRT continues to map the probable extension of NBF northeast of Inabanga towards Getafe and southwest towards Loon and Maribojoc.

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The longest, continuous individual trace mapped by PHIVOLCS QRT is approximately 2 kilometers in Brgy. Anonang. In this barangay, surface rupture trends N40E. The surface rupture manifested as prominent fault scarps, which range from 2-5 meters of vertical displacements. Other geomorphic manifestations observed in Brgy. Anonang include 2.5 meter vertical displacement of Cawasan Creek in Sitio Calubian, producing a small waterfall at the point where the fault transects the creek. Other typical features associated with reverse faulting, such as scallops, bulges and warps, were also observed in the deformation zone, which extended as wide as 30 meters in some places.

Further south-westward of Brgy. Anonang in Sitio Tangub, Brgy. Liloan Norte, PHIVOLCS QRT measured a shift in the trend of the fault trace to N55-60E and a decrease in the vertical displacement to 0.15 meter. PHIVOLCS QRT observed the presence of a spring along the trace of the surface rupture. Residents of this sitio confirmed that the spring appeared only after the earthquake.

In the next barangay of Napo, still in Inabanga and north of Inabanga River, the surface rupture trends N40-60E, with vertical displacements ranging from 0.10 to 0.40 meter.

Towards the NE from Brgy. Anonang in Inabanga to Brgy. New Anonang in Buenavista, the surface rupture trending N40E is manifested by displaced rice paddies. Vertical displacements range from 0.3 to 0.5 meter.

The fault probably terminates in Sitio Haligi, Brgy. New Anonang in Buenavista, where an originally flat-lying ricefield became gently sloping. The difference in elevation is measured at 0.10 meter. This feature is different from the previously observed abrupt break along the surface rupture and is common along the termini of active faults.

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Although the PHIVOLCS QRT has not yet finished mapping the SW extension of NBF, it is likely that the fault extends towards north of Maribojoc. A sea-ward shift of the high tide mark after the earthquake was observed by the residents in Brgy. Punta Cruz, Maribojoc. This shift in high tide mark may imply that Maribojoc is on the upthrown block of the reverse NBF. The PHIVOLCS QRT measured the shift to be about 50 meters.

Liquefaction

Loon “Sinkhole”

According to PHIVOLCS QRT, what they saw in Loon are not technically “sinkholes” in the strictest sense but depressions as a result of ejection of materials due to liquefaction. Almost an entire coastal barangay (Brgy. Napo) experienced liquefaction. Some of the houses even had rejected mud in their living rooms. Those which were not damaged are still habitable but those that collapsed are no longer safe. Loon Church was totally damaged. The shoreline in loon also shifted by about 30 meters, similar to that of Maribojoc.

Isla Batasan is one of the islands located between Bohol and Cebu. It is experiencing sudden floods, causing its residents to believe that their island is slowly sinking. PHIVOLCS

explains that there is indeed a big possibility that some islands may start sinking after the earthquake, due to liquefaction and

earthquake deformation.

Liquefaction happens when the soil loses its strength and stiffness due to an

earthquake, causing it to soften and behave like liquid. Earthquake deformation, on the other

hand, refers to a change in the original shape of a material.

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Earthquake-Induced Landslide

The magnitude 7.2 earthquake on 15 October 2013 main shock, triggered shallow

landslides that can be observed on the steep natural slopes of the famous Chocolate

Hills in Bohol. The shallow disaggregated landslides are typically not associated with

particular geologic units and/or type of slopes. They are usually as deep as the root

zone of the vegetative cover, anywhere from several decimeters to a meter deep, and

consist of dry, highly disaggregated and fractured material that cascaded down-slope to

flatter areas at or near the base of slopes.

Shallow disaggregated landslides account form most the failure types after earthquakes. However, some of the landslides shown on the Chocolate Hills when looked at more closely are more deep-seated rock and earth slumps that involve relatively large volumes of material. Earthquake triggered landslides contributed to the following noted disruptions as shown and more than 40 barangays have reported landslides :

The highway in Cortes particularly in Lilo-and was rendered impassable due to a landslide. A part of Cortes’ highway was also damaged.

In Balilihan, the Bohol Mayor, Dominisio Chatto has confirmed that 5 people died from a landslide due to the earthquake.

In Loon, Bohol, numerous landslides have affected areas. Sinkholes

A sinkhole is an area of ground that has no natural external surface drainage; when it rains, all of the water stays inside the sinkhole and typically drains into the sub

surface.

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Collapsed sinkhole along A. Torralba St.,

Poblacion, Tagbilaran City from the earthquake

Sinkhole located at the back of Panganan

High School, estimated depth ~3.4m, area

20x6 m

Uvala

According to MGB, an uvala is a collection of multiple smaller individual sinkholes that

coalesce into a compound sinkhole.

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EFFECTS

Seismological Information

Aftershocks

As of the last Situational Report of NDRRMC on Bohol Earthquake

(Sit Rep no.35) dated November 3, PHIVOLCS recorded 3,198 aftershocks, 94 of

which were felt. (as of 4am, Nov.3)

Aftershocks are expected, some of which will be felt. These may

continue for weeks to months, but diminishing in number and strength as time passes.

In this case, a higher magnitude earthquake related to this event is no longer expected

to occur.

DECREASING TREND OF

AFTERSHOCKS

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PHIVOLCS EARTHQUAKE INTENSITY SCALE (PEIS)

Intensity Scale Description I

Scarcely Perceptible. It is scarcely perceptible to people under favorable circumstances. Delicately balanced objects are disturbed slightly. Still water in containers oscillates slowly.

II

Slightly Felt. It is felt by few individuals at rest indoors. Hanging objects swing slightly. Still water in containers oscillates noticeably.

III

Weak. It is felt by many people indoors especially in upper floors of buildings. Vibration is felt like one passing of a light truck. Dizziness and nausea are experienced by some people. Hanging objects swing moderately. Still water in containers oscillates moderately.

IV

Moderately Strong. It is felt generally by people indoors and by some people outdoors. Light sleepers are awakened. Vibration is felt like a passing of heavy truck. Hanging objects swing considerably. Dinner, plates, glasses, windows and doors rattle. Floors and walls of wood framed buildings creak. Standing motor cars may rock slightly. Liquids in containers are slightly disturbed. Water in containers oscillates strongly. Rumbling sound may sometimes be heard.

V

Strong. It is generally felt by most people indoors and outdoors. Many sleeping people are awakened. Some are frightened, some run outdoors. Strong shaking and rocking felt throughout building. Hanging objects swing violently. Dining utensils clatter and clink; some may be damaged. Small, light and unstable objects may fall or overturn. Liquids spill from open containers. Standing vehicles rock noticeably. Shaking of leaves and twigs of trees are noticeable.

VI

Very Strong. Many people become scared; many may run outdoors. Some people lose their balance. Motorists feel like driving in flat tires. Heavy objects or furniture move or may be shifted. Small church bells may ring. Wall plaster may crack. Very old or poorly built houses and man-made structures are slightly damaged though well-built structures are not affected. Limited rockfalls and rolling boulders occur in hilly to mountainous areas and escarpments. Trees shake noticeably.

VII

Destructive. Most are frightened and run outdoors. People find it difficult to stand in upper floors. Heavy objects and furniture overturn or topple. Big church bells may ring. Old or poorly-built structures suffer considerably damage. Some well-built structures may be damaged slightly. Some cracks may appear on dikes, fishponds, road surface, or concrete hollow block walls. Limited liquefaction, lateral spreading, and landslides are observed. Trees shake visibly. (Liquefaction is a process by which loose saturated sand lose strength during an earthquake and behave like liquid).

VIII

Very Destructive. People become panicky. People find it difficult to stand outdoors. Many well-built buildings are considerably damaged. Concrete dikes and foundation of bridges are destroyed by ground settling or toppling. Railway tracks are bent or broken. Tombstones may be displaced, twisted, or overturned. Utility posts, towers, and monuments may tilt or topple. Water and sewer pipes may be bent, twisted, or broken. Liquefaction and lateral spreading cause man-made structure to sink, tilt, or topple. Landslides and rockfalls occur in mountainous and hilly areas. Boulders roll out from their positions particularly those near the epicenter. Fissures and faults rapture may be observed. Trees violently shake. Water splash over dikes or banks of rivers.

IX

Devastating. People are forcibly thrown to ground. Many cry and shake with fear. Most buildings are totally damaged. Bridges and elevated concrete structures are toppled or destroyed. Numerous utility posts, towers, and monument are tilted, toppled, or broken. Water sewer pipes are bent, twisted, or broken. Landslides and liquefaction with lateral spreadings and sandboils are widespread. The ground is distorted into undulations. Trees are shaken very violently with some toppled or broken. Boulders are commonly thrown out. River water splashes violently on slops over dikes and banks.

X

Completely Devastating. Practically all man-made structures are destroyed. Massive landslides and liquefaction, large scale subsidence and uplifting of land forms and many ground fissures are observed. Changes in river courses and destructive seiches in large lakes occur. Many trees are toppled, broken and uprooted.

With the PEIS as guide, people will know the severity of the earthquake.

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Casualties

As of November 3, 2013, 6am, 222 individuals are reported

dead, 976 injured, and 8 are missing

Affected Population

A total of 671,103 families / 3,221,248 persons were affected in 1,527

barangays in 60 municipalities and 6 cities in 6 provinces of Region VI and

VII

Out of the total affected, 71,822 families / 348,507 persons were displaced and

served both inside and outside evacuation centers in the Province of Bohol:

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Inside 392 evacuation centers: 17,203 families / 79,773 persons

Outside evacuation centers: 54,619 families / 268,734 persons

The number of homeless from this earthquake is somewhere between 87,000 and

370,000. Due to aftershocks, damaged houses, lack of basic services, 87,000 people are in

shelters, but many remain also in tents next to their homes or along roads (around 280,000

are outside of shelters but still in need of basic support.

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NEEDS ASSESSMENT

The earthquake affected areas in Bohol were not directly hit by the super Typhoon Haiyan (locally known as Yolanda) and no major damages were reported. Power supply to the Bohol region, however, has been disrupted, causing blackouts and water shortages. The majority of the earthquake-affected population have returned to their settlements, but are still dependent on assistance from the government and humanitarian partners.

According to NDRRMC, the number of evacuation sites and centers has decreased from a high of 599 down to 65 as of November 15. While relief distributions are ongoing, the focus of assistance is now shifting to early recovery activities. Rehabilitation of damaged infrastructure and houses remains the priority. Early Recovery Needs:

Support for debris management

Updating of damage assessments Constraints:

Coordination for early recovery planning needs strengthening.

Damage assessment including final numbers of partially and totally damaged houses needs to be finalized.

Specific assessments and interventions should be developed for debris management including solid and liquid waste.

Provincial Planning Department (PPD) is facing challenges in obtaining reports from municipal government.

Emergency Shelter

Needs:

DSWD review of damaged or destroyed houses has identified 28,000 houses as

damaged or destroyed. The survey is ongoing, with the Provincial Engineers

Office leading, executed by municipality engineers.

The interim report confirms that most of the destroyed houses are concrete or masonry houses. Approximately 50 percent of the affected population are sleeping inside their houses; most of the remaining displaced are in makeshift shelters near their damaged or destroyed homes. Less than 5 percent are staying formal and informal evacuation centers.

Many families are demolishing and repairing their houses, with needs emerging within the communities

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Constraints:

There is a need for further clarification and verification of the damage and destroyed house data. This will be done through the structural damage assessment under the lead of the Provincial Engineers Office.

There is a need for additional tarpaulins. Currently, only one tarpaulin is being distributed per family.

Evacuation

Need:

There is a need to set up a system to identify the needs in the displacement sites Constraint:

Access constraints continue to hamper delivery of service and relief items.

Food Security

Need:

More than 70,000 families are in need of immediate food assistance. Constraint:

Resources are overstretched as organizations are also responding to Typhoon Yolanda survivors and Zamboanga emergencies.

Health

Needs:

According to the November 15 Disaster Response Operations Monitoring and Information Center (DROMIC) report, 73,195 families whose houses have been destroyed need medical and psychosocial support. An estimated 7,894 pregnant and 5,262 lactating women need specialized services for prenatal, postnatal, child health, health promotion and family planning services.

Provincial Health Office (PHO) Bohol has confirmed 8 totally and 29 partially damaged rural health units, 13 totally and 116 partially damaged barangay health stations, 1 totally and 11 partially damaged hospitals and 4 damaged birthing facilities, two of which are non-functional.

Surveillance in Post Extreme Emergencies and Disasters (SPEED) reported the top five consultations as acute respiratory infection (ARI), fever, skin diseases, open wounds and bruises, and hypertension. Municipalities of Tubigon, Maribojoc, and Inabanga reported high numbers of consultations for acute diarrhea. Suspected leptospirosis was reported from the municipalities of Loon,

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Sagbayan and Carmen, while suspected measles were reported in the municipalities of Antequera, Danao, Clarin, Carmen, Sagbayan and Tubigon.

Constraints:

Capacity to sustain health services in communities where health facilities are not functioning and surge medical teams are pulling out. Additional medical and mobile team are needed to provide health services to the remaining barangays not yet covered.

There is a need for an in-depth assessment of damaged health facilities according to services and functionality at the barangay level.

Additional staff trained in SPEED at local levels are needed to sustain and improve regularity of reporting.

Weather disturbances over the past week have made support more difficult, including risks of landslides on roads in affected municipalities.

Reports of deliveries at home and en route to referral hospitals highlight the need to urgently improve access to emergency obstetric care. Health service delivery points for emergency obstetric and neonatal care were compromised with the damage to health facilities.

Irregular power supply in almost all health facilities after Typhoon Haiyan (Yolanda) compromises vaccines and management of cold chain as well as poses challenges for emergency obstetric and medical services.

Water, Sanitation and Hygiene (WASH)

Needs:

Additional hygiene kits are needed.

Some water treatment units have been moved from Bohol to Tacloban. Water supply remains problematic in some municipalities, particularly in Clarin and Sagbayan.

Regular water quality monitoring is needed – results of tests conducted have not been shared by the Provincial Health Office (PHO).

Constraint:

Gaps in data on WASH needs in schools Protection Needs:

Except for the Philippine National Police (PNP) reporting system, Gender Based Violence (GBV) reporting and counseling services in most affected areas has been disrupted.

Children are becoming used to the ongoing aftershocks but require safe, structured play and developmental opportunities in Child Friendly Spaces (CFS).

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The majority of local level Child Welfare Councils are inactive, with individual child protection concerns dealt with by police and social workers.

capacity building and awareness-raising in the evacuation centers and communities

Constraints:

Limited availability and shortage of social workers to address psychosocial issues of earthquake survivors.

Lack of data on GBV cases due to the disruption of reporting and prevention services after the earthquake.

Psychosocial support services provided mainly by DOH, NGOs and individuals are still fragmented

The inter-agency mechanism for GBV is not functioning well in the provinces and municipalities.

Logistics Need:

Generators for deployment to the hardest -hit municipalities.

Constraints:

Pending security assessment, the cluster will establish additional prefabricated offices and living accommodations to help front-line responders work more effectively on the ground.

Recent heavy rains flooded the Mobile Storage Unit (MSU) in Tubigon Community Hospital.

Education

Needs:

Priority needs include temporary learning spaces, repair/rehabilitation of schools and replacement of teaching learning materials and school supplies.

WASH in schools also needs proper assessment to see the rehabilitation needs.

Extension of psychosocial support services to affected children and education service providers is also needed.

Constraints:

Resources are overstretched.

Some areas are inaccessible. Broken bridges constrain access to many affected schools in Bohol.

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Livelihood Need:

Of highest priority are emergency income-generating activities which can also align with key rehabilitation and reconstruction needs.

Constraints:

Damaged structures including roads, bridges, public buildings, and private establishments affect the immediate resumption of existing jobs and livelihood.

Alternative and long term livelihood strategies are needed.

SHELTER ASSESSMENT (KEY FINDINGS)

The proportion of totally destroyed shelters and shelters with major damage seems significantly lower than current government estimates. In contrast, the high proportion of partially damaged shelters points to the need for broader based support including in areas which are currently ranked as low priority for intervention. Amongst households that sustained any type of shelter damage, masonry structures were by far the most affected, while huts and timber structures displaying significantly more resilience.

Type of housing and level of damage are strongly related to the recovery intentions of households, especially for those who chose to relocate. Access to land and tenure security are critical concerns for households whose homes were totally destroyed or sustained major damage, and who wish to relocate to areas where they do not own property.

The vast majority of households have not begun repairing, rebuilding, or

relocation processes. This lag in the process along with few households able to recover with their own resources suggests little capacity for self-recovery.

Designs, materials, and labor are reported as the highest needs in terms of

shelter assistance. Particular attention should be given to the specific needs of vulnerable households, such as women-headed households, in terms of shelter assistance.

In spite of the low proportion of households receiving shelter assistance, 96% reported that they had received other types of assistance.

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CONCLUSION AND RECOMMENDATIONS

The earthquake in Bohol and Cebu and the damages it has wrought has again

resurfaced anxiety among Filipinos. Disaster risks have not been reduced to that level wherein people and their communities are safe, secure, and resilient.

Municipalities in northwest Bohol were hardest-hit. At least 3,198 aftershocks were recorded as of November 3 since the first powerful earthquake with 94 tremors of which were felt. Since the destructive earthquake occurred inland, no tsunami was generated.

A total of 222 people died, 976 injured and 8 still missing. The majority of casualties are reported in Bohol, according to the National Disaster Risk Reduction and Management Council (NDRRMC). The earthquake caused landslides and other geological effects and extensive damage to housing, hospitals, schools, infrastructure and utilities, with more than 70,000 houses severely damaged or destroyed.

Structural assessment and clearance of public buildings and residences are urgently needed. Further, awareness of the warning signs in danger areas due to fissures and soil failure, should be raised among affected families. The best course of action is preparedness. Despite the response efforts, still additional response is needed. Reconstruction and recovery will take time, and recovery planning is critical at the early stages of the response.

REFERENCES: PHIVOLCS (www.phivolcs.dost.gov.ph)

Mines and Geosciences Bureau (www.mgb.gov.ph)

NDRRMC Situational Reports-Bohol Earthquake (www.ndrrmc.gov.ph)

Department of Social Welfare and Development (www.dswd.gov.ph)

Philippine Information Agency (http://news.pia.gov.ph)

PPDO-Bohol Interactive Mapping Service (www.ppdobohol.lgu.ph/interactivemap/map.html)

Info Bohol (http://www.infobohol.com/earthquake-relief-efforts-bohol-philippines/)

READY Project-Hazard Maps

United Nations Office for the Coordination of Humanitarian Affairs (OCHA)

Earthquake-Report.com (www.earthquake-report.com)

Earthquake Hazards Program-USGS (www.earthquake.usgs.gov)

REACH Initiative (www.reach-initiative.org)

ReliefWeb (www.reliefweb.int)

ShelterCluster.org-Philippines (https://www.sheltercluster.org/Asia/Philippines/ )

Google Earth (earth.google.com)