The Study on Comprehensive Disaster Prevention Around Mayon Volcano SUPPORTING REPORT (1) (Part I: Master Plan) VI : Disaster Mapping/Hazard Mapping SUPPORTING REPORT (1) – VI DISASTER MAPPING/HAZARD MAPPING Table of Contents Page 1. TOPOGRAPHY AND GEOLOGY ..................................................................... VI - 1 1.1 Topography .................................................................................................... VI - 1 1.2 Geology.......................................................................................................... VI - 5 2. ERUPTION OF MAYON VOLCANO AND RELATED HAZARD.................. VI - 5 2.1 Ejection .......................................................................................................... VI - 5 2.2 Pyroclastic Flow............................................................................................. VI - 7 2.3 Lava Flow ...................................................................................................... VI - 8 2.4 Ash Fall .......................................................................................................... VI - 9 2.5 Mud and Debris Flow .................................................................................. VI - 10 3. HAZARDS AND AFFECTED AREA .............................................................. VI - 12 3.1 Review of Previous Disaster and Hazard Analysis...................................... VI - 12 3.2 Disaster Affected Area................................................................................. VI - 17 3.3. Hazard Zoning.............................................................................................. VI - 17 List of Tables Page Table VI 2.1 Main feature of the Recent four (4) Eruptions and Their Precursors.. VI - 20 Table VI 2.2 Emplacement Parameters of Geomorphologic Major Pyroclastic Deposit Area........................................................................................ VI - 21 Table VI 2.3 Emplacement Parameters of Geomorphologic Major 1984 Pyroclastic Fans................................................................................... VI - 21 Table VI 2.4 Maximum Distance Reached by Mayon Volcano Lava Flow Units ... VI - 22 Table VI 2.5 Emplacement Parameters of Geomorphologic Debris Flow Deposit Area Identified by the 1982 Air Photographs ..................................... VI - 23 Table VI 2.6 Historical Lahar Event of Mayon Volcano (Since 1616 to 1992) ....... VI - 24 Table VI 2.7 Comparative Casualty of the 1993 Eruption and the Following Typhoons ............................................................................................. VI - 25 Table VI 2.8 Disaster Caused by Typhoon and Often Heavy Rainfall..................... VI - 26 Table VI 2.9 Calamities and Casualities in Study Area Caused by Remarkable since 1993............................................................................................ VI - 27 i Table VI 2.10 Hazard Inventory on Each Municipality Caused by Typhoon "Ditang" on 1992................................................................................. VI - 28 Table VI 3.1 Mud and Debris Disaster Affected Area on the Geomorphologicsl Classification Map in 1999.................................................................. VI - 29 Table VI 3.2 Disaster Record of Mud and Debris Flow on the Recent Eruption..... VI - 30 Table VI 3.3 Summary of Assumed Sedimentation Range...................................... VI - 31 Table VI 3.4 Maximum Distance Reached by Mayon Volcano Lava Floe Units .... VI - 32 Table VI 3.5 emplacement Parameters of Geomorphologic 1984 Pyroclastic Fans VI - 33 List of Figures Page Figure VI 1.1 Location Map of Major Volcanic Centers in the Southeastern Luzon Bicol Volcanic Chain........................................................................... VI - 34 Figure VI 1.2 Longitudinal Profile around Mayon Volcano Slope............................ VI - 35 Figure VI 1.3 Longitudinal Profile on the Yawa River System................................. VI - 36 Figure VI 1.4 Simplified Landform Classification Map............................................ VI - 37 Figure VI 1.5 Submarine Contour Map in East Saide of Mayon Volcano................. VI - 38 Figure VI 1.6 Schematic Sketch of Volcanic Fan (source: Moriya, 1983) ................ VI - 39 Figure VI 1.7 Schematic Profile of Volcanic Fan ...................................................... VI - 40 Figure VI 1.8 Schematic Sketch of Geomorphological Development Process of Volcano................................................................................................ VI - 41 Figure VI 1.9 Relationship between Basal Diameter (Horizontal) and Relative Height (Vertial).................................................................................... VI - 42 Figure VI 1.10 Location Map of Geological Survey Points ........................................ VI - 43 Figure VI 1.11 Composite Stratigraphy and Correlative Sections............................... VI - 44 Figure VI 2.1 Disaster Map on the 1814 Eruption..................................................... VI - 45 Figure VI 2.2 Disaster Map on the 1897 Eruption..................................................... VI - 46 Figure VI 2.3 Disaster Map on the 1984 Eruption..................................................... VI - 47 Figure VI 2.4 Disaster Map on the 1993 Eruption..................................................... VI - 48 Figure VI 2.5 Photographs of the June 22, 1999 Eruption ........................................ VI - 49 Figure VI 2.6 Isopach Map fo Lahar Deposit Thickness in the Pawa-Burabod River Field Caused on the 1984 Eruption ........................................... VI - 50 Figure VI 2.7 Comparison of the Aerial Photograph Around the Summit taken in 1982 and 1999 ..................................................................................... VI - 51 Figure VI 2.8 Geomorphologic Change by Comparison of 1982 and 1999 in Maninila River..................................................................................... VI - 52 Figure VI 2.9 Geomorphologic Change by Comparison of 1982 and 1999 in Anuline (C) River and Budiao River................................................... VI - 53 ii Figure VI 2.10 Geomorphologic Change by Comparison of 1982 and 1999 in Basud River ......................................................................................... VI - 54 Figure VI 3.1 Danger Zone Map for Mud/Debris Flow by the 1983 JICA Study (1)..................................................................................... VI - 55 Figure VI 3.2 Danger Zone Map for Mud/Debris Flow by the 1983 JICA Study (2)..................................................................................... VI - 56 Figure VI 3.3 Hazard Map in "Operation Mayon" .................................................... VI - 57 Figure VI 3.4 1999 Mayon Permanent Danger and High Sustainability Areas......... VI - 58 Figure VI 3.5 1999 Mayon Volcano Lava Flow Hazard Map ................................... VI - 59 Figure VI 3.6 1999 Mayon Volcano Pyoclastic Flow Hazard Map ........................... VI - 60 Figure VI 3.7 Mayon Volcano Lahar Flow Hazard Map revised by PHIVOLCS on 1999................................................................................................ VI - 61 Figure VI 3.8 Hazard Map of Lahar and Debris Flow (1) ......................................... VI - 62 Figure VI 3.9 Hazard Map of Lahar and Debris Flow (2) ......................................... VI - 63 iii SUPPORTING REPORT (1) – VI DISASTER MAPPING/HAZARD MAPPING 1. TOPOGRAPHY AND GEOLOGY 1.1 Topography (1) General Setting Mayon Volcano is located on the Bicol Peninsula in the southern part of the Luzon Island. The Luzon Island, situated on the shear zone called circum Pacific island arcs, is centred at an active earthquake fault and volcanic zone between the Philippine Trench and the Philippine Fault Zone. Mayon Volcano is a part of the northwest trending eastern Bicol volcanic chain that results from subduction associated with the Philippine Trench (Ramos, et al. 1985). Location map of Bicol volcanic chain is shown in Figure VI 1.1. The Bicol Peninsula consists generally of Upper Tertiary and Pleistcene sedimentary and volcanic rocks. Mayon Volcano, nine other major stratovolcanoes, and several smaller volcanic cones form the eastern Bicol volcanic chain (Datuin, 1982), associated with west-dipping subduction along the Philippine Trench. (2) Mountain Slope Profile and Riverbed Slope Topographical profile of Mayon Volcano has an extraordinary symmetry as a konide type. Its summit level is 2,469m above sea level and covers an area of 250km2. Mountain slope has steep gradient (1/2.5) from the summit down to 500m above sea level. From 500m down to 200m above sea level, it becomes little gentle gradient (1/7.8) more than upper reaches. From 200m level down to the sea base, it has gently sloping sides (1/19.9). Landform units of Mayon Volcano slope are classified as lava flow, alluvial fan at volcanic foot and tertiary mountain at margin. The profiles and slope gradient classification of the slope are depicted and shown in Figure VI 1.2 and the table in the next page. Meanwhile, Figure VI 1.3 present the profiles of the selected rivers. Most of the profiles show the gradual change in slope from steep to gentle in accordance with descending elevation. The profiles of the San Vicente and the Bulawan rivers in the northeast slope show a slightly sudden decrease in slopes