Tsunami Hazard Assessment along the Coast of Lingayen Gulf, Pangasinan, Philippines Julius M. GALDIANO PHIVOLCS Julius M. GALDIANO PHIVOLCS 4 th International Conference on Earth Science and Climate Change June 2015, Melia Alicante 4 th International Conference on Earth Science and Climate Change June 2015, Melia Alicante

 Introduction and Background  Purpose of the Study  Theories and Methods  Bathymetry and Topography Data  Scenario Earthquakes  Computational Settings  Results and Conclusions  Introduction and Background  Purpose of the Study  Theories and Methods  Bathymetry and Topography Data  Scenario Earthquakes  Computational Settings  Results and Conclusions Presentation Outline 2

3  Introduction and Background  Purpose of the Study  Theories and Methods  Bathymetry and Topography Data  Scenario Earthquakes  Computational Settings  Results and Conclusions  Introduction and Background  Purpose of the Study  Theories and Methods  Bathymetry and Topography Data  Scenario Earthquakes  Computational Settings  Results and Conclusions

EQUATOR Tectonic Setting and Faults and Trenches in the Philippines 4

Data sources:  NEIC for recent earthquakes ( )  Bautista and Oike (2004) for historical earthquakes ( ) Philippine Seismicity Philippine Seismicity  For the past 400 years: 40 tsunamis  Magnitude:6.0 to 8.3  Casualties:4075

Source: Google Maps Study Area: Lingayen Gulf, Pangasinan Province M7.6 6 May 1934 Source: NGDC; Bautista (1999)

May 6, 1934, 11:59 AM-2m tsunami in San Esteban, Ilocos Sur Historical Events Source: Philippine Tsunamis and Seiches ( ) by Bautista et al. Figure by Bautista et al. May 16, 1924, 12:16 AM-1m tsunami in Agno, Pangasinan

System Composition: -Detection Station (Wet, Dry, and Ultrasonic Tide Gauge Sensors) -Alerting System (Tri- directional loud siren, meter range) System Composition: -Detection Station (Wet, Dry, and Ultrasonic Tide Gauge Sensors) -Alerting System (Tri- directional loud siren, meter range) Lingayen Gulf Tsunami Detector Alerting System Map Source: Google Image Lingayen Gulf near Real-time Tsunami Warning System

9  Introduction and Background  Purpose of the Study  Theories and Methods  Bathymetry and Topography Data  Scenario Earthquakes  Computational Settings  Results and Conclusions  Introduction and Background  Purpose of the Study  Theories and Methods  Bathymetry and Topography Data  Scenario Earthquakes  Computational Settings  Results and Conclusions

 To predict the tsunami travel time and its maximum height at forecast points  To calculate the subsequent tsunami inundation height and submerged area at a target location  To discuss the effectiveness of tsunami sensors for near real-time tsunami forecasting Purpose of the Study 10

11  Introduction and Background  Purpose of the Study  Theories and Methods  Bathymetry and Topography Data  Scenario Earthquakes  Computational Settings  Results and Conclusions  Introduction and Background  Purpose of the Study  Theories and Methods  Bathymetry and Topography Data  Scenario Earthquakes  Computational Settings  Results and Conclusions

Theoretical Concepts 12

Theoretical Concepts 13

After JMA Lecture Notes (2013) Theoretical Concepts 14

Effect of the Horizontal Components Theoretical Concepts 15

Numerical Stability Theoretical Concepts 16

 Selection of earthquake source parameters for tsunami simulation for each case scenario from Salcedo (2010) study  Numerical tsunami simulation using TUNAMI-N2 (Imamura et al., 2006; Koshimura, 2009; Yanagisawa, 2013; Fujii, 2013)  Analyze the effectiveness of the existing tsunami sensor and proposed tsunami sensor project Methods and Procedure 17

18  Introduction and Background  Purpose of the Study  Theories and Methods  Bathymetry and Topography Data  Scenario Earthquakes  Computational Settings  Results and Conclusions  Introduction and Background  Purpose of the Study  Theories and Methods  Bathymetry and Topography Data  Scenario Earthquakes  Computational Settings  Results and Conclusions

Bathymetry and Topography Data 19 Topography and Bathymetry Map (NAMRIA, 1952) GEBCO 30 arc-sec + Digitized Points =

Bathymetry and Topography Data 20 GEBCO 1 arc-min Bathymetry GEBCO 30 arc-sec + Digitized Bathymetry Bathymetry data for tsunami arrival times and tsunami heights calculations

Bathymetry and Topography Data 21 Bathymetry and topography data for tsunami inundation calculations GEBCO 30 arc-sec + Digitized Bathymetry + SRTM_v2 Data (N16-17˚E ˚)

22  Introduction and Background  Purpose of the Study  Theories and Methods  Bathymetry and Topography Data  Scenario Earthquakes  Computational Settings  Results and Conclusions  Introduction and Background  Purpose of the Study  Theories and Methods  Bathymetry and Topography Data  Scenario Earthquakes  Computational Settings  Results and Conclusions

Manila Trench Segment 2 (Salcedo, 2010) Scenario Earthquake 23 Case 1 : Historical Initial Condition: Magnitude: 7.6 Lat, Lon : 16.06˚N,119.10˚E Fault length: km Fault width: km Strike angle: 1 deg Dip angle: 36 deg Rake angle : 95 deg Slip amount: 1.21 m Depth: 0 km Maximum uplift : 0.64 m Maximum subsidence: m

Manila Trench Segment 2 (Salcedo, 2010) Scenario Earthquake 24 Case 2 : Maximum Credible Initial Condition: Magnitude: 8.4 Lat, Lon : 16.06˚N,119.10˚E Fault length: km Fault width: km Strike angle: 1 deg Dip angle: 36 deg Rake angle : 95 deg Slip amount: 3.69 m Depth: 0 km Maximum uplift : 1.87 m Maximum subsidence: m

25  Introduction and Background  Purpose of the Study  Theories and Methods  Bathymetry and Topography Data  Scenario Earthquakes  Computational Settings  Results and Conclusions  Introduction and Background  Purpose of the Study  Theories and Methods  Bathymetry and Topography Data  Scenario Earthquakes  Computational Settings  Results and Conclusions

26 Computational Settings Location of Tide Stations

27 Computational Settings For Tsunami Height and Tsunami Travel Time

28 Computational Settings

29 Computational Settings For Tsunami Inundation Computation of 4 Regions  Computational dimension: 14-20˚N, ˚E  Computational time: s (4 hrs)  Temporal grid size, ∆t: 1.0 s  Spatial grid size: 1 arc-min, 20 arc-sec, 6.67 arc-sec, 2.22 arc-sec, respectively for Regions 1-4  Grid points: nx=270 to 945, ny= 360 to 972 ( 4 Regions)  Topography Data: SRTM_v2 (3 arc-sec)  Bathymetry Data : GEBCO 30 arc-sec + Digitized points

30 Computational Settings Region 1 Region 2 Region 3 Region 4

31  Introduction and Background  Purpose of the Study  Theories and Methods  Bathymetry and Topography Data  Scenario Earthquakes  Computational Settings  Results and Conclusions  Introduction and Background  Purpose of the Study  Theories and Methods  Bathymetry and Topography Data  Scenario Earthquakes  Computational Settings  Results and Conclusions

32 Results 1. Tsunami Waveforms Case 1: Mw7.6Case 2: Mw8.4 GEBCO 1 arc-min GEBCO 30 arc-sec

33 Results 1. Tsunami Waveforms Case 1: M7.6Case 2: M8.4 GEBCO 30 arc-sec GEBCO 30 arc-sec + digitized bathymetry

34 Results 2. Tsunami Arrival Times 38 min 35 min

35 Results 3. Tsunami Maximum Heights 0.3 m 1.6 m

36 Results Case 1(Mw7.6)Case 2(Mw8.4) 0.7 m 2.8 m 3. Tsunami Maximum Heights

37 Results 4. Tsunami Inundation Case 1(Mw7.6) Case 2(Mw8.4)

38 Results 4. Tsunami Inundation Vertical + horizontal effects Vertical effects only 17%

39 Results 5. Tsunami Sensor Case 1: 36 min Case 2: 37 min Case 1: 44 min Case 2: 45 min Case 1: 8 min Case 2: <1 min Case 1: 15 min Case 2: 11 min

40 Conclusions  There will be a minimal tsunami effect of the case 1 (M7.6) earthquake scenario in the Lingayen Gulf coast.  Anticipation of the 1.6 m tsunami height (case 2: M8.4) in the inner bay should be planned for.  No enormous tsunami inundation will happen in the case 2 earthquake scenario in Dagupan City assuming that the SRTM data are accurate. Topography verification of the target area is recommended.  Considering the horizontal effect in tsunami simulation is important in order to anticipate the wave height difference when it is neglected.

41 Conclusions  ASTI (existing tsunami sensor) can be effective as warning system in the inner bay because there is a lead time of at least 45 min (case 2) for the people to evacuate after the tsunami will be detected while it is ineffective in Bolinao coast because there is a sudden tsunami arrival (case 1: 8 min; case 2: less than 1 min)  The JICA tide gauge station (proposed tsunami sensor) detects the tsunamis earlier than the tide gauge stations set in the inner bay.  Combining ASTI and JICA tide gauges as tsunami sensors will advance to a better and more robust early warning system in the Lingayen Gulf.

42 Way forward  Topography verification  Recalculation of the inundation area in citywide/townwide coverage  Do the tsunami risk of the study area  Tsunami Hazard plan of the study area

43 Way forward  Topography verification  Recalculation of the inundation area in citywide/townwide coverage  Do the tsunami risk of the study area  Tsunami Hazard plan of the study area  Re-entry Plan…  To develop case scenario earthquakes to use for tsunami early warning system in the Philippines  To help in the development of the tsunami database in the Philippines

Thank you very much for your attention…