Earthquake Monitoring in the Philippines PDF

Name: MONTERA, HANNAH ERICA G. Subject & Code: BCES 2 (1561) EARTHQUAKE MONITORING IN THE PHILIPPINES The Imperative of Earthquake Monitoring in the Philippines The Philippines, nestled in the Pacific Ring of Fire, is a nation perpetually exposed to the seismic forces of nature. Ear...

Name: MONTERA, HANNAH ERICA G. Subject & Code: BCES 2 (1561) EARTHQUAKE MONITORING IN THE PHILIPPINES The Imperative of Earthquake Monitoring in the Philippines The Philippines, nestled in the Pacific Ring of Fire, is a nation perpetually exposed to the seismic forces of nature. Earthquakes, a constant threat, have the potential to wreak havoc on lives, infrastructure, and economies. In this context, earthquake monitoring emerges as a critical tool, not merely for scientific inquiry, but for safeguarding lives and mitigating disaster. Understanding the Seismic Threat The Philippines' geographical location makes it susceptible to frequent seismic activity. Tectonic plates constantly shift and collide beneath the archipelago, generating energy that is released in the form of earthquakes. The intensity and frequency of these events vary, but their potential impact remains significant. Major earthquakes can cause widespread destruction, including collapsed buildings, landslides, and tsunamis. The Role of Earthquake Monitoring Earthquake monitoring involves the systematic observation and analysis of seismic activity. This is accomplished through a network of seismometers strategically placed across the country. These instruments detect and record ground vibrations, providing valuable data on the magnitude, location, and depth of earthquakes. Benefits of Earthquake Monitoring 1. Early Warning Systems: By detecting seismic waves, monitoring systems can issue early warnings to communities at risk. This precious time allows people to take protective measures, such as evacuating buildings or seeking shelter, potentially saving countless lives. 2. Risk Assessment: Analyzing historical earthquake data helps scientists identify areas prone to seismic hazards. This information is crucial for urban planning, infrastructure development, and disaster preparedness strategies. 3. Scientific Research: Continuous monitoring contributes to a deeper understanding of earthquake mechanisms and seismic patterns. This knowledge is essential for refining prediction models and improving disaster response efforts. 4. Public Awareness: By disseminating information about earthquake risks, monitoring systems promote public awareness and preparedness. Educated citizens are more likely to take necessary precautions and respond effectively to seismic events. The Philippine Institute of Volcanology and Seismology (PHIVOLCS) PHIVOLCS, a government agency, plays a pivotal role in earthquake monitoring and research in the Philippines. It operates a network of seismic stations, analyzes data, and issues timely alerts. The agency's efforts have significantly improved the country's ability to respond to earthquakes and mitigate their impact. In a nation as seismically active as the Philippines, earthquake monitoring is not a luxury but a necessity. By providing early warnings, informing risk assessments, and advancing scientific knowledge, monitoring systems empower the country to face the challenges posed by earthquakes. As technology continues to evolve, it is imperative to invest in robust monitoring infrastructure and public education to ensure the safety and well-being of the Filipino people. TYPE OF SEISMIC STATIONS 1. UNMANNED SEISMIC STATION ( SATTELITE TELEMETERED) Unmanned seismic stations are remote, self-sufficient devices that play a vital role in monitoring seismic activity worldwide. Equipped with seismometers, these stations detect and record ground vibrations caused by earthquakes. By deploying these stations in remote and hazardous areas, scientists can gather crucial data on seismic events, enabling early warning systems, accurate hazard assessments, and valuable insights into Earth's dynamic processes. These stations operate autonomously, powered by solar energy and transmitting data via satellite or cellular networks. The benefits of unmanned seismic stations are numerous. They provide real- time data, improve the accuracy of seismic networks, and are cost-effective. Additionally, they contribute to scientific research, disaster preparedness, and nuclear monitoring efforts. As technology advances, unmanned seismic stations are becoming increasingly sophisticated, making them indispensable tools for understanding and mitigating the risks associated with earthquakes and other seismic phenomena.  College Of Engineering Education Civil Engineering Program In Partial Fulfillment of the Requirements for BCES2(1561)- Earthquake Engineering Written Report Submitted by: Jude Gabriel M. Pagatpatan Submitted to: Engr. Mervin Mamza November 2024 MANNED SEISMIC STATION (STAFFCONTROLLED) Components: Seismometers and Accelerometers: high-sensitivity instruments for detecting seismic events. Data Logger: sophisticated equipment for data recording and initial analysis. Power Supply: stable power sources, including backup systems. Communication System: multiple communication methods, including internet and radio links. Workspaces: equipped for staff to perform monitoring and maintenance tasks. Phivolcs Mindanao Cluster Monitoring Center for Earthquake and Tsunami in Davao Seismic Station Volcano Observatory in Philippines Legaspi Volcano Station, the first volcano monitoring station on Mayon Volcano, was established by the Commission on Volcanology (COMVOL) in 1955 and housed at the Civil Aeronautics Building near the Legaspi City airport. This was succeeded by a second volcano station established in 1966 in Brgy. Sta. Misericordia, Sto. Domingo, Albay Province. COMPONENTS: Seismometers: Detect volcanic tremors and earthquakes. Gas Sensors: Measure volcanic gases like sulfur dioxide, which can indicate rising magma. Thermal Cameras: Monitor changes in surface temperature. GPS Receivers: Track ground deformation around volcanoes. Power Supply: Combination of solar panels, batteries, and sometimes generators. Communication System: Satellite and radio links for transmitting data.  WRITTEN REPORT UNIVERSITY OF MINDANAO COLLEGE OF ENGINEERING EDUCATION CIVIL ENGINEERING PROGRAM In Partial Fulfillment of the requirements for BCES2- Earthquake Engineering (1561) Submitted by: Elnar B. Benaning Submitted to: Engr. Mervin Mamza November 2024  THE PHILIPPINE EARTHQUAKE MODEL THE PROBABILISTIC SEISMIC HAZARD ANALYSIS ❖ The goal of many earthquake engineering analyses is to ensure that a structure can withstand a given level of ground shaking while maintaining a desired level of performance. There is a great deal of uncertainty about the location, size, and resulting shaking intensity of future earthquakes. Probabilistic Seismic Hazard Analysis (PSHA) aims to quantify these uncertainties and combine them to produce an explicit description of the distribution of future shaking that may occur at a site. ❖ Using the PSHA equation; PHILIPPINE INSTITUTE OF VOLCANOLOGY AND SEISMOLOGY (PHIVOLCS) ❖ The Philippine Institute of Volcanology and Seismology (PHIVOLCS) is a Philippine national institution dedicated to provide information on the activities of volcanoes, earthquakes, and tsunamis, as well as other specialized information and services primarily for the protection of life and property and in support of economic, productivity, and sustainable development. They produced this site-specific probabilistic seismic hazard assessment of the Philippines and of Metro Manila because it may be used as a basis in promoting adherence to the minimum design requirements in building structures and in calculating for the “design base shear” ( V=2.5CaW/R) where V= the design base shear, Ca= the seismic coefficient, W= the weight of the structure, and R= the numerical coefficient; of the inherent over-strength and global ductility capacity of lateral-force-resisting systems stipulated in the National Structural Code of the Philippines ( NSCP), a referral code of the National Building Code (NBC). DATA SOURCE ❖ More than 58, 000 instrumental records of earthquakes in the Philippines from 1900 to 2015 and 333 historical earthquake accounts from 1600 to 1900 formed in the initial base (Bautista and Oike, 2000). ❖ The instrumental seismicity is a collection of records from the catalogues of the Philippine earthquakes which were source from the following: Seismicity of the Earth (Richter-Gutenberg) International Seismological Summary (1918-1957) Bulletin of the Seismological Society of America Seismological Notes (1926-1963) Bureau Central Institute de Seismologique Strasbourg (1958-1962) United States Coast and Geodetic Survey Card (July 1959-April 1964) Significant Philippine Earthquakes, Philippine Weather Bureau Scientific Publication (1926-1959) Seismological Bulletin Manila Central Observatory (1926-1940)  ❖ The Philippine Atmospheric Geophysical and Astronomical Services Administration (PAGASA) catalogues of significant Philippine earthquakes prior to 1986 and from the PHIVOLCS seismic monitoring from 1986 until December 2015. ❖ In addition, 487 earthquake events (Mw>5.3) were culled from the; International Seismology Center- Global Earthquake Model United States Geological Survey (USGS) Source Model ❖ This collection of data was verified, compared, and the homogenized all magnitudes values to “moment magnitude (Mw)” that were also limited to engineering interest only, that is events of Mw5.2 and above. ❖ A total of 1,179 earthquake events (Mw5.2 and above) constituted the PSHA database is approximately 2% of the Philippine earthquake catalogue together with the information on Active Faults and Trenches in the Philippines and Global Positioning System (GPS) was then utilized to delineate the boundaries and parameters of individual seismic source zone.  ❖ In the figure, shows the earthquake occurrence rates of the 111 characterized source zones. The x-axis shows the individual source zones while the y-axis indicates the frequency of earthquake events per year. ❖ These rates were calculated by dividing the number of seismic events by the number of years of data completeness per magnitude bin for each source zone. ❖ Results show that the Philippine Trench is the most seismically active source zone at 3.6 events per year followed by Eastern Visayas area source zone at 2.4 events per year. ❖ Due to the quality of attributed seismicity per bin, the following weights of contribution was determined for each source zone: ▪ 100% - for area and trench source zones ▪ 60% - for active faults with attributed seismicity ▪ 10% - for active faults with seismicity derived from surficial velocities ❖ Three Source Model: ▪ Source model 1 - all source zones ▪ Source model 2 – area sources, trench sources and active faults ▪ Source model 3 – area sources and trench sources only GROUND MOTION PREDICTION MODEL (GMPM) ❖ GMPMs are used to characterize the source-to-site seismic wave attenuation. ❖ ground-motion prediction models use datasets of recorded ground-motion parameters at multiple stations during different earthquakes and in various source regions to generate equations that are later used to predict site-specific ground motions (Strasser et al. 2009). JOSHUA MORLAND QUIJANO - BCES2 (1561) NARRATIVE REPORT THE PHILIPPINE EARTHQUAKE MODEL Logic trees - were used to account for uncertainties in source models and GMPM applicability. A 10%-50%-40% uncertainty ratio was applied to the source models, while GMPM logic tree weights were 40%-30%-30% for active shallow crust regions and 90%- 10% for subducting slabs. A logic tree is a diagram that visually represents a sequence of decisions, actions, or outcomes, breaking down complex problems into simpler, manageable components. It helps organize information and analyze different possibilities or solutions in a structured way. SITE MODEL The average shear wave velocity of the upper 30 meters of soil (Vs30) plays a key role in determining site response. Since a national Vs30 site model is unavailable for the Philippines, a 1-km x 1-km model was used for Metro Manila (Grutas and Yamanaka, 2012). The soil profile types considered are: Rock site (Sc): Vs30 = 760 m/sec Stiff soil (sD): Vs30 = 360 m/sec CALCULATION PROGRAM The OpenQuake Engine, developed by the Global Earthquake Model (GEM), was used for seismic hazard analysis to model probabilistic ground accelerations (Weatherill, 2012; GEM, 2017). The results were visualized using QGIS (QGIS Development Team, 2009). P R O B A B I L I S T I C G R O U N D A CC E L E R A T I O N M A P S (P G A M A P S) This Atlas includes PGA maps for the Philippines on a rock site (Vs30 = 760 m/sec) and a Vs30 site model for Metro Manila at 10%, 5%, and 2% probability of exceedance (PoE). It also features spectral acceleration (SA) contour maps for the Philippines on stiff soil (Vs30 = 360 m/sec) and a Vs30 site model for Metro Manila. ILLUSTRATIVE CASE: Earthquake Safety Analysis: C.P. Garcia Ave, UP Diliman, Quezon City This case looks at how a specific location along C.P. Garcia Avenue, UP Diliman campus in Quezon City, is expected to respond to an earthquake based on shaking measurements and building code standards. Key Points: 1. Ground Shaking Levels: o At this site, the Peak Ground Acceleration (PGA), which is the maximum expected ground shaking, is 0.4g. o To analyze how the site might shake at different times, we use Spectral Acceleration (SA) values. These values, shown in Figure 2, tell us that the highest SA is 0.9g at 0.2 seconds. For longer time periods (0.5 sec, 0.8 sec, 1.0 sec, and 3.0 sec), the SA values decrease to 0.4g, 0.25g, 0.2g, and 0.05g respectively, meaning the most intense shaking occurs quickly, then tapers off. 2. Comparison with Building Standards: o The National Structural Code of the Philippines (NSCP) requires buildings to be designed to withstand a seismic coefficient of 2.5g, a much higher level than the site’s strongest expected shaking of 0.9g. o Since the site’s maximum SA value (0.9g) is below the NSCP’s design level of 2.5g, code-compliant buildings at this site are expected to perform safely under the anticipated earthquake shaking. Figure 3 illustrates the comparison between the site’s expected response and the NSCP design response. 3. Safety Implications for Structures: o To ensure safety, the NSCP standard suggests that the building design should be stronger than the maximum ground shaking expected at the site. In this case, because the 2.5g design standard exceeds the site’s peak SA of 0.9g, structures built according to code are likely to withstand the expected shaking. o If shaking exceeds the design limits at any period, however, even engineered structures might be at risk, and non-engineered structures could experience serious damage. (See references to these risks in studies by Pallarubia, 2017, and Imai et al., 2015).  4. Factors Affecting Site Shaking: Several factors influence how much shaking this site will experience: o Earthquake Source Characteristics: Where and how the earthquake originates. o Wave Attenuation: The weakening of seismic waves as they travel to the site, which depends on the distance and type of ground. o Soil Layer Properties: Particularly the shear wave velocity in the upper 30 meters of soil (Vs30), shown in Table 1, which can either amplify or reduce ground shaking based on whether the soil is soft or hard. Conclusion: The analysis in Figures 2 and 3, along with data in Table 1, shows that buildings at this site are likely to be safe if they follow the NSCP standards, as the expected shaking is below the required design level. Additionally, the earthquake response at this site depends on the earthquake’s source, how the waves weaken over distance, and the characteristics of the soil, which are important factors for ensuring structural resilience. Assumptions: 1. Shear Wave Velocity: o Assumes 1.0 km/sec shear wave speed at 50 meters depth and 2.5 km/sec at 500 meters depth. These values represent typical speeds through different layers beneath the surface. 2. Peak Ground Acceleration (PGA): o On rock sites, the PGA values are set to a maximum of 0.6g for a 10% probability of exceedance (PoE) in 50 years. This standard is applied uniformly across source zones in the map. 3. Fault Activity Rates: o For active faults without specific seismic records, the assumed activity rate should not be higher than that of active faults with at least one known earthquake. Limitations: Data Sources: o The maps are derived from Probabilistic Seismic Hazard Analysis (PSHA) databases, which include fault activity rates, area sources, fault parameters, and monitoring data. o Updates or improvements in any data source could change hazard estimates. Ground Motion Response: o The displayed acceleration values reflect horizontal ground response only; they don’t consider the influence of structures, site modifications, or development on the ground. Site Model and Structural Design: o The maps use the Vs30 model for short-period responses, which is ideal for assessing nearby earthquake effects on low-rise structures. o For buildings on deeper, soft soil layers or for high-rise and long-span structures, site-specific geotechnical studies are suggested to account for long-period shaking. Uncertainty: o Since there are uncertainties in seismic modeling, data, and estimations, this hazard map provides a detailed yet not absolute estimate. Users should  consult authorities for guidance and apply sound judgment when interpreting these values. Abbreviations: PGA: Peak Ground Acceleration – The highest level of earthquake-induced shaking expected at a site. PoE: Probability of Exceedance – The likelihood that ground shaking will exceed a certain level in a specified time frame (e.g., 10% in 50 years). PSHA: Probabilistic Seismic Hazard Analysis – A method for estimating earthquake hazard by considering the likelihood of various earthquake scenarios and their potential shaking levels. Vs30: Shear Wave Velocity in the Top 30 Meters – Measures the speed of seismic waves through the upper 30 meters of soil or rock, used to classify site conditions and their likely impact on shaking. -----------------------------------------MAPS AFTER THIS PAGE----------------------------------------  figure I. Zonal Earthquake Occurence RMe. N/ye:ir (MW?S.2) " ,, UJJ LI. I.t1.lJ.LJ.J l!JJll!l!lllJJII JJ?1!li 1.00 o.so MO uo OA ".... __ __ __ --- -q,rob:1bilis-tic Spectr:11 Accele.r1nion Response (g) at selected sites (stars a,·ranied norch co south on 1be map) , ,. s·ue LAcalion I Dis1a1 t 10 \VVF PGA SA (0.2) SA (0.5) SA (0.8) SA (I.OJ SA (3.0) I San Mmeo Road. Northvk>w. Quu.on City 145m 0.52 1.30 0.7!/ 0.43 0.32 0.08 J 2 - - , QuCZ(>ll Cily (1'- PMIVOtCS. Oillntl1l Z.!)(J() m. (1.40 0.87f - 0.37 0.23.,. 0.19 0.06 3 T. Ri\'enilde Dflve, DtlaPena. MarildM City 594m (J.5/ 1.32 0.84 0.36 0.28 0.08 4 t BIR. '·-.Y' llltnmll.lfOS, City. otM, - mJla I IO.S30 111 0.32 0.83 Q.65 0,41 0.34 0.0!1 5 Kabu1Jhlln, IJ.ago n}l llg. Pasig Clly 43m 0.49 1.23 (J.50 (J.30 0.24 0.07 I 6 Bougainvilla, Pcn'1x>. -Makatl Chy 209111 0.49 1.23 0.50 0.30 0.24 0,().7 7 SJOH, EDSA,R0X3$ Blvd, P"'yCily 6.980m (J.38 0.88 0.6/1 0.44 0.35 0.09 --. e "!!' t 8 Amlstad, Mer\'llle, 1>aranaque CII y Z,SIOm 0.48 /.24 0.52 0.3/ 0.25 0.07 9 Cun'11nl('l.,. New l..s are horlzo111aJ ground response and do no1 inchide the in0ucnce or on-site s1ruc1urcs and site developments. The relatively shallow Vs30 site model is sensitive to shon-period response (T lscc.) and therefore most useful for near source effect and in the seismic design and performance of low-rise strucwres. for very thick underlying soft soil layer or basin and in designing 4 for long-span s1rucwres. and high-rise buildings (f > lscc.), a she-specific geotechnlcal lnves1lgaclon Is recommended to accommodate for long-period response. Moreover, alemoricand epistemic uncertainties abound. Thus. this Philippine Earthquake Model. although rnay be the most detailed estimate to date based frorn available data. Is not absolute. Users of this Atlas are encouraged 10 exc.rcise caution and soundjudgment and 10 consul1 the: ao1hotitles for insights. References Abe. K, (1981). icucle, ol lar3(' h.1llow r;irrbquakC$ rrc,m 1901,1980, Ph).,._ &nh i>&ine,.Jm:l.7,72,92. Allf'. K. (19St). Compkm 1t. fn W.H.K. L. H. Kanwoor-1. P.C. Jenni and C. Kl li118ff (edit«s> 2002. IJ11.m1a1ion-.d Handl,ook.of &srtJiqwke atKI E..s;infflfag Stbtno!USY. Pait A. ChatlgJrolR(!!,Mn. hlM1eNVOlllffl(' 68. No, I, SS-73. 1997. --------------------------------------------------------------------- _____________________I  M;Jgnitude (Mw) N o o,p[11&)7) 0 0 S-l·S.8(UtJ) 0..... ,,.,) W.E 0 6,S·7,0(l'1.SJ ,.. 0 0 7,1,l,.}(10,J ,.... ,,. 0 ,.. ,,.._..... 0 W tel' &o6lM 0 0 0 [)(pl tion 0 DalStl YMJ t,\f Ph lht cntcn of 1 100 hb ,11,-d lnUrumMtllly rt«lfdcd urthqu:lke from 1608lo 1016 with motntnc m.J:s,,il\16ttp'O th.inMw4.1, 1---- 0 0 0 0 0 0 0 0 0 Oo e o q,g 0 o d eo O 0 0 " o o.i% 'ft ';.,,a, Q 0 'd~ 0 0 0 O O #1., 0 s ·.,o... " 0 6) 0 WEST PHft.lPPIN€ 'I, SEA 0 0 0 0 0 0 0 SUlU SEA o. 0 g O 0 0 0 0 0 0 0 0 0 ~ 0 G) 0 0 0 0 0 0 0 0 CELEBE0 0 0 0 0 [) ~ v.__ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _0_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __.._ __;,...:.._ _ _ _...r;...z,...:;;i;~ - "----...;;,,:,,,_,_. ~ v n&"E 11$"E uo"E mt u 1: ----------------------------  M tudt(Mw) 0 0 µ.µs{10)) sM 6A (164J 0 0 1 111,t ,. 0 1.- MS{10) 0 0 So 1 00 ISCt JOO 250 L 07.'4·&..JS(u) 0 l 416,,146:&1079 T,rkl ~ ~6)191,-a366 iJooo... l! ,____________________________________________ 00 Oeccrnbffi-o,7 ~ r- I o'E u8'E  Peak Ground Acceleration Map of the Philippines 500-Year Return Period on Rock Site I \.. , I Ac.c,(W