Journal of Engineering, Technology and Computing Sciences

Estimating Earthquake Risks: The Use of Rapid Earthquake Damage Assessment System (REDAS) in the Province of ,

P. Silvestre a,e1, R. Talvo b,e2, Z. Vargas c,e3, D. Butedd,e4, G. Domantay e.5

aFaculty of Pangasinan State University-Sta. Maria Campus, Sta. Maria, Pangasinan, Philippines, bcFaculty of Pangasinan State University- Campus, Lingayen, Pangasinan, Philippines d President of Pangasinan State University, Lingayen, Pangasinan, Philippines e Vice President for Academic Affairs of Pangasinan State University, Lingayen, Pangasinan, Philippines [email protected], [email protected], [email protected], e4 [email protected], [email protected]

Abstract - The Philippines has 18 regions, and Pangasinan is the biggest province in Region I with a land area of 536,819 hectares. It has ahigh risk of earthquakes due to the Trench. This study was conducted to estimate earthquake risk in the province with the use of Rapid Earthquake Damage Assessment System (REDAS) software. There were three barangays from , one of the 44 towns in the province, where actual building survey was taken to represent residential, commercial and mixed commercial and residential sites which were used in creating the Pangasinandatabase for this study. Estimation of earthquake risk using REDAS was based on the 1796 historical earthquake event which has a magnitude of 6.9 and a depth of 35 km. Results show that the total estimated floor area damages in square meters are 5,902,337 and 272,064 for totaldisaster with no collapse and fulldestruction with collapse. Based on number of buildings, the total estimated complete with no collapse and complete with collapse damages are 115,694 and 5,315, respectively. The total estimated economic loss in millions is 63,069. The number of injuries is 52,382 minor injuries, 10,949 serious injuries, 459 severe injuries and 1,321 fatalities. The overall result shows that the cities of , Urdaneta and San Carlos and the towns of , and are the most at risk based on estimated damage regardingarea in square meters, number of buildings, economic loss, number of injuries and fatalities. Results of the study have shown that REDAS is a valuable tool to estimate the extent of damages from an earthquake. Information from the assesseddegree of damages in particular areas in the province can guide those who are involved in disaster risk reduction planning and implementation.

Keywords - REDAS; earthquake risk; rapid assessment

I. INTRODUCTION a term used to describe both sudden slip on a fault Natural disasters or calamities are natural and the resulting ground shaking and radiated occurrences that affect the world and cause changes seismic energy caused by the slip, or by volcanic or in the lives of people who suffer from these. magmatic activity, or other sudden stress changes in Typhoons, earthquakes, floods, landslides, tsunamis the earth. The location below the earth’s surface and volcanic eruptions are natural disasters where the earthquake starts is called the hypocenter, commonly experienced not only in the Philippines and the location directly above it on the surface of but also in other countries in the world. The extent the earth is called the epicenter of damages in life and properties among victim (http://earthquake.usgs.gov). An earthquake hazard countries vary depending on how is anything associated with an earthquake that may thegovernmentplanned and prepared for the affect the normal activities of people. emergence of such disasters [1]. An earthquake is one of the natural disasters that pose significant risk to lives and properties. It is

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This includes surface faulting, ground shaking, will occur. The quantified risk may be expressed as landslide, liquefaction, tectonic deformation, the number of elements lost, proportion of elements tsunamis, and seiches [2]. affected and monetary value of damaged property In the Philippines, the Philippine Institute of [4]. Volcanology and Seismology (PHIVOLCS) of the Republic Act (RA) No. 10121 otherwise known Department of Science & Technology (DOST) is the as the “Philippine Disaster Risk Reduction and mandated agency with a mission to provide timely Management Act of 2010” (PDRRM-2010) was and quality information and services for thewarning, enacted on May 27, 2010, to strengthen the disaster preparedness, and mitigation. Thisis Philippine disaster risk reduction system. It accomplished through the development and specifically provides for the development of policies application of technologies for the monitoring and and plans and the implementation of actions and accurate prediction of, and determination of areas measures about all aspects of disaster risk reduction prone to, volcanic eruptions, earthquakes, tsunamis and management. Thisincludesgood governance, and other related hazards, and capacity enhancement risk assessment and early warning, knowledge for comprehensive disaster risk reduction[3]. building and awareness raising, reducing underlying risk factors, and preparedness for effective response One of the strategies of PHIVOLCS to realize and early recovery [5]. their mandate is the development of a user-friendly This study used REDAS to estimate the and straightforward simulation tool or software that earthquake risk in the province of Pangasinan in case can give a rapid estimate of the possible seismic an earthquake of magnitude 6.9 and impact hazards which can be used for inferring the severity estimation in case of an 8.5 earthquake occurs. The of impacts to various elements-at-risk. This software province of Pangasinan is located in the west-central is called “Rapid Earthquake Damage Assessment area of the island of along the . System” or REDAS. PHIVOLCS-DOST developed It is 170 kilometers north of Manila and 50 the software thru a Grant-in-Aid (GIA) from the kilometers south of City. It is considered as Department of Science and Technology (DOST). the “food basket” of Region I and the largest among REDAS aims to provide quick and near real-time the four provinces in the region both regarding simulated earthquake hazard information to disaster theland area and population. It has a land area managers which will help them in assessing the of536,819 hectares and a total population of distribution and extent of the impacts of a strong 2,956,726 based on the 2015 census on population earthquake. This could help them to decide and [5]. It consists of 44 towns, four cities and a total of prioritize the deployment of timely rescue and relief 1,364 barangays. The Philippines lies within the operations. The second objective is for the software “Ring of Fire”, a region of subduction zone to serve as a tool in convincing land use planners, volcanism surrounding the Pacific Ocean which policymakers, city and town development planners makes the country a hotspot for earthquakes and and even local government executives to consider other geological hazards. Records of earthquakes in earthquake hazards in their planning and the Philippines traced to as far back as the 1600s development efforts to ensure long-term mitigation show that tremors registering magnitude-6 and over of seismic risks. Its potential to be a risk assessment on the Richter scale have been experienced all over tool is being enhanced by improving the exposure the country. Pangasinan is prone to earthquakes, database, inclusion of a building inventory module, especially the deep-focused ones, due to the Manila incorporation of vulnerability curves and enhancing Trench and Philippine fault zone [3]. its modeling capability to address other natural On July 16, 1990, Central Luzon was rocked by hazards [3]. the strongest quake to hit the northern Philippines. The risk is the expected losses (of lives, persons The earthquake registered a magnitude 7.8 on the injured, property damaged and economic activity Richter Scale with epicenter at 15.6N and 121.0E disrupted) due to a particular hazard for a given area near the town of Rizal, . The 1990 and reference period. The unit of measure could be Luzon Earthquake was felt in many places at the value of damaged property. Risk assessment Intensity VIII (based on a modified version of the includes the examination of risks resulting from Rossi-Forel Intensity Scale of I to IX currently used natural events like flooding, extreme weather events, in the Philippines). However, some modifications earthquakes, etc. that may pose threats to may be necessary because there were isolated areas, ecosystems, animals, and people. It involves the like Dagupan City, Baguio City and the town of process of quantifying and evaluating risk and their Rizal in Nueva Ecija which seemed to have effects on economic activities and public services experienced the earthquake at Intensity IX based on exposed to hazards in a given area. Quantitative risk theobserved wave-like motion of the ground surface assessment requires calculations of the magnitude of [6] and documented theoccurrence of thrown-up the potential loss, and the probability that the loss

16 PSU JETC Silvestre et al. 1(1):15-19, DecemberJournal 2017 of Engineering, Technology and Computing Sciences ISSN boulders. Liquefaction effects of the 16 July l990 C. Risk Calculation and Loss Estimation Earthquake were particularly pronounced in the Out of the data from the three barangays, the provinces of Tarlac, Pangasinan, and . An assessment of the impact of ground shaking using earlier historical earthquake event that has a high the historic 6.9 magnitude earthquake in 1796 was magnitude of 6.9 in 1796 with a longitude of estimated for the province following the REDAS 120.5045, latitude of 16.1095 and a depth of 35 steps in conducting seismic hazard assessment [7]. kmwas recorded. There are equations in the REDAS program used to Thus, to provide a significant tool for calculate risk and estimate loss due to the earthquake disaster preparedness, this study was earthquake. These estimated damages, losses, conceived to estimate earthquake risk for the injuries and fatalities were plotted as maps and province of Pangasinan using the REDAS. figures. Specifically, it aims to: Develop earthquake exposure database for the province; Estimate risks III. RESULTS AND DISCUSSIONS and calculate losses due to theearthquake; and A total of 1,908 buildings were surveyed from evaluate the capability of the Rapid Earthquake the three barangays of Calit, Gayaman, and Damage Assessment System. Poblacion of Binmaley, Pangasinan. From these building survey data, the exposure database for Pangasinan was developed and used in the seismic II. METHODOLOGY hazard assessment specifically for ground shaking A. Capacity Building using REDAS. Figures of the loss maps and graphs Before the start of the project activities, training are developed for easy interpretation. on the use of the REDAS (Capacity Enhancement of Academic Researchers on Hazards, Risk Assessment Hazard Maps and Impact Graphs of Magnitude 6.9 and Exposure Database Development through the Earthquake Scenario in Pangasinan use of the REDAS software) was conducted at the The following figures show some of the loss Mariano Marcos State University (MMSU) in maps for Pangasinan due to Magnitude 6.9 January 2016. Enumerators were also briefed on earthquake using survey data. The light color proper techniques in the conduct of the actual survey indicates less concentration of damage and the dark of buildings to be used in the study. Another seminar color suggests maximum/extensive damage. The star on earthquake risk assessment in REDAS using shows the epicenter of the earthquake. survey data was conducted in June 2016 at Don

Mariano Marcos Memorial State University, , La Union.

B. Site Selection, Survey Proper, and Exposure Database Three barangays of Binmaley, Pangasinan was the chosen barangays to gather building survey data that was used in the study. The barangays of Calit, Gayaman and Poblacion, were selected to represent theresidential area, commercial area and thecombination of residential and commercial area, respectively. The EDM for android was used to gather the needed data which include among others the building use, structure, period built, geography, and estimated number of occupants. The exposure database for the province of Pangasinan was one of the outputs of the study. It shows us the elements at risk due to ground shaking from an earthquake with Figure 1. Complete Damage with Collapse for an assumed specific magnitude. Among the Pangasinan due to Magnitude 6.9 earthquake using information that was extracted from the database are survey data (in number of buildings). the number of buildings, use of buildings, type of buildings, population and others for the surveyed barangays of Binmaley. These data were used to estimate the earthquake risk for the entire province.

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The highest number of buildings that incur total damage with collapse is shown in Figure 1. The most affected cities and municipalities include Dagupan City (375), Urdaneta City (345), San Carlos City (327), Malasiqui (250) and Mangaldan (246). The least affected is Agno with two buildings.

The economic loss in millions of pesos in case a magnitude of 6.9 earthquakes occurs in Pangasinan is shown in Figure 2. The cities and municipalities that have the highest number of economic loss are the cities of Dagupan (5,121), Urdaneta (4,524), San Carlos (3,804) and the towns of Mangaldan (2,679) and Calasiao (2,627). The municipality of Burgos has the lowest estimated economic loss of 50 million

Figure 3.Serious injuries for Pangasinan due to Magnitude 6.9 earthquake using survey data.

Figure 2.Economic loss for Pangasinan due to Magnitude 6.9 earthquake using survey data (in millions). . Figure4.Fatalities of Pangasinan due to Magnitude The estimated number of severe injuries in case 6.9 earthquake using survey data. a magnitude of 6.9 earthquakes happens for Pangasinan is shown in Figure 3. The cities and The estimated fatalities in case a magnitude of municipalities that have the highest number of 6.9 earthquakes happens inPangasinan is shown in serious injuries are the cities of Dagupan (868), San Figure 4. The cities and municipalities that have the Carlos (3719), Urdaneta (718), and the towns of highest number of fatalities include Dagupan City Mangaldan (567), and Malasiqui (531). The (109), Urdaneta City (94), San Carlos City(92), and municipality of Agno has the lowest number of the towns of Mangaldan (73), and Calasiao (63). The serious injuries which is 2. estimated total number of fatalities is 1,321.

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IV. CONCLUSIONS Estimation of earthquake risk using the REDAS V. ACKNOWLEDGEMENTS with a magnitude of 6.9 earthquake scenario The authors would like to express their revealed that the three cities with the highest gratitude to Isabela State University (ISU), damages in square meters are Dagupan City, Philippine Institute of Volcanology and Seismology UrdanetaCity, and San Carlos City. On the other (PHIVOLCS) specially the REDAS team from hand, the top three municipalities are Mangaldan, Department of Science & Technology - Philippine Calasiao and Malasiqui. The municipality with the Council for Industry, Energy and Emerging least estimated damage is Burgos. Based on the Technology Research and Development (DOST- number of buildings, Dagupan City, Urdaneta City, PCIEERRD), and Pangasinan Provincial and San Carlos City have the highest damage in Government for providing the researchers the number of buildings, also are the municipalities of needed data, the training/seminar in REDAS, Mangaldan, Calasiao and Malasiqui. The financial resources and for all their assistance in the municipality with the least estimated damage is conduct of this study. Burgos. The total estimated economic loss is 63,069 million of pesos with Dagupan City, Urdaneta City REFERENCES and San Carlos city with the highest losses. The total estimated number of injuries is 52,382 [1] World Conference on Disaster Reduction. minor injuries, 10,949 serious injuries, and 459 January 2005. Hyogo Framework for Action: severe injuries. As to the overall estimated number Building the Resilience of Nations and of injuries,the result is 1,321. The cities of Dagupan, Communities to Disasters. Retrieved October Urdaneta and San Carlos and the towns of 2014 at Mangaldan, Malasiqui and Calasiao are the most at http://www.unisdr.org/2005/wcdr/intergover/off risk as to the assessed number of injuries and icial-doc/L-docs/Hyogo-framework-for-action- fatalities. english.pdf. The overall result shows that the cities of [2] http://earthquake.usgs.gov/ Dagupan, Urdaneta and San Carlos and the towns of [3] www.phivolcs.dost.gov.ph Mangaldan, Malasiqui and Calasiao are the most at [4] http://www.neda.gov.ph/ risk based on estimated damage regarding thearea in [5] Commission on Audit. 2014. Assessment of square meters, number of buildings, number of Disaster Risk Reduction and Management injuries and number of fatalities. The cities of (DRRM) at the Local Level. Dagupan, Urdaneta and San Carlos are characterized [6] https://psa.gov.ph as a business or commercial centers and the towns of [7] Torres, Ronnie C., Paladio, Ma. Lynn, Mangaldan, Malasiqui and Calasiao have many Punongbayan, Raymundo, Alonso, Rosalito. commercial establishments as well. Also, the (1990). Mapping of Areas Affected by epicenter of the earthquake is too close to these Liquefaction during the 16 July 1990 cities/municipalities. Earthquake. This study has shown that REDAS is a valuable http://www.phivolcs.dost.gov.ph/html/update_S tool to estimate the extent of damages from a natural OEPD/1990LuzonEQ_Monograph/foreword.ht phenomenon like an earthquake. Information from ml. the estimated extent of damages in particular areas [8] REDAS Manual. of the province can guide those who are involved in disaster risk reduction planning and implementation.

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