Transcript Bathymetry and Topography Data

Tsunami Hazard Assessment along the Coast of
Lingayen Gulf, Pangasinan, Philippines
4th International Conference on Earth Science
and Climate Change
16-18 June 2015, Melia Alicante
Julius M. GALDIANO
PHIVOLCS
Presentation Outline
 Introduction and Background
 Purpose of the Study
 Theories and Methods
 Bathymetry and Topography Data
 Scenario Earthquakes
 Computational Settings
 Results and Conclusions
2
 Introduction and Background
 Purpose of the Study
 Theories and Methods
 Bathymetry and Topography Data
 Scenario Earthquakes
 Computational Settings
 Results and Conclusions
3
Tectonic Setting
and Faults and
Trenches in the
Philippines
EQUATOR
http://earthquake.usgs.gov/learning/topics
4
Philippine
Seismicity
1608-2012
 For the past 400
years: 40 tsunamis
 Magnitude:6.0 to
8.3
 Casualties:4075
Data sources:
 NEIC for recent
earthquakes
(1897-2002)
 Bautista and Oike
(2004) for historical
5
earthquakes (1608-1896)
Study Area: Lingayen Gulf,
Pangasinan Province
M7.6
6 May
1934
Source: Google Maps
Source: NGDC; Bautista (1999)
Historical Events
May 6, 1934, 11:59
AM-2m tsunami in
San Esteban, Ilocos
Sur
Figure by Bautista et al.
May 16, 1924,
12:16 AM-1m
tsunami in Agno,
Pangasinan
Source: Philippine Tsunamis and Seiches (1589-2012) by Bautista et al.
Lingayen Gulf near Real-time
Tsunami Warning System
System
Composition:
- Detection
Station (Wet,
Dry, and
Ultrasonic
Tide Gauge
Sensors)
- Alerting
System (Tridirectional
loud siren,
300-400 meter
range)
Lingayen Gulf Tsunami
Detector
Alerting System
Map Source:
Google Image
 Introduction and Background
 Purpose of the Study
 Theories and Methods
 Bathymetry and Topography Data
 Scenario Earthquakes
 Computational Settings
 Results and Conclusions
9
Purpose of the Study
 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
10
 Introduction and Background
 Purpose of the Study
 Theories and Methods
 Bathymetry and Topography Data
 Scenario Earthquakes
 Computational Settings
 Results and Conclusions
11
Theoretical Concepts
Equations in Cartesian Coordinate System
Shallow Water Wave Equation:
𝝏𝜼 𝝏𝑴 𝝏𝑵
+
+
=𝟎
𝝏𝒕 𝝏𝒙 𝝏𝒚
Equations of motion:
𝝏𝑴
𝝏𝒕
𝝏𝑵
𝝏𝒕
+
𝝏 𝑴𝟐
𝝏𝒚 𝑫
+
𝝏 𝑴𝑵
𝝏𝒙 𝑫
+
𝝏 𝑴𝑵
𝝏𝒚 𝑫
+
𝝏 𝑵𝟐
𝝏𝒚 𝑫
=
=
𝝏𝜼
−𝒈𝑫
𝝏𝒙
𝝏𝜼
−𝒈𝑫
𝝏𝒚
−
−
𝒈𝒏𝟐
𝑴
𝑫𝟕/𝟑
𝒈𝒏𝟐
𝑵
𝑫𝟕/𝟑
𝑴𝟐 + 𝑵𝟐
𝑴𝟐 + 𝑵𝟐
𝜂 : wave amplitude
𝑡 : time
𝑀, 𝑁 : discharge fluxes in the x and y directions
D : total water depth
n : roughness coefficient
References: Imamura et al., 2006; Koshimora, 2009
12
Theoretical Concepts
Equations in Spherical Coordinate System
Continuity and momentum equation:
𝝏𝜼
𝝏𝒕
𝝏𝑴
𝝏𝒕
+
𝝏𝑵
𝝏𝒕
𝒈𝑫 𝝏𝜼
𝑹𝒄𝒐𝒔𝜽 𝝏𝝀
+
+
𝒈𝑫 𝝏
𝑹𝒄𝒐𝒔𝜽 𝝏𝜽
+
𝟏
𝝏𝜼
[
𝑹𝒄𝒐𝒔𝜽 𝝏𝝀
𝟏
𝝏 𝑴𝟐
𝑹𝒄𝒐𝒔𝜽 𝝏𝝀 𝑫
+
𝟏
𝝏
𝑹𝒄𝒐𝒔𝜽 𝝏𝝀
+
𝝏
𝑵
𝝏𝜽
+
𝟏
𝝏
𝝏𝑴𝑵
(𝒄𝒐𝒔𝜽
)
𝑹𝒄𝒐𝒔𝜽 𝝏𝝀
𝑫
𝑵𝟐
𝒄𝒐𝒔𝜽
𝑫
𝒄𝒐𝒔𝜽 ] = 0
+
+
𝒈𝒏𝟐
𝑴
𝑫𝟕/𝟑
𝟏
𝝏 𝑴𝑵
𝒈𝒏𝟐
( ) + 𝟕/𝟑 𝑵
𝑹𝒄𝒐𝒔𝜽 𝝏𝝀 𝑫
𝑫
𝑴𝟐 + 𝑵𝟐 =0
𝑴𝟐 + 𝑵𝟐 =0
𝜂 : wave amplitude
𝑡 : time
𝑀 : discharge flux in the 𝜆 (along the latitude)
𝑁 : discharge flux in the 𝜃 (along the longitude)
𝐷 : total water depth
𝑛 : roughness coefficient
𝑅 : radius of the earth
13
Reference: Yanagisawa, 2013
Theoretical Concepts
After JMA Lecture Notes (2013)
14
Theoretical Concepts
Effect of the
𝒖𝒉 =
Horizontal Components
𝝏𝑯
𝒖𝒙
𝝏𝒙
+
𝝏𝑯
𝒖𝒚
𝝏𝒚
𝐻 : water depth
𝑢𝑥 and 𝑢𝒚 : horizontal seafloor
displacement due to faulting
Total Vertical Water Displacement:
𝒖𝒉 + 𝒖𝒛
𝑢𝑧 : vertical seafloor displacement due
to faulting
Reference: Tanioka and Satake, 1996
15
Theoretical Concepts
Numerical Stability
∆𝒕 ≤
𝜟𝒙
𝟐𝒈𝒉𝒎𝒂𝒙
∆𝑡 and Δ𝑥 : the temporal and spatial
length of grid sizes
𝑔 : gravity acceleration (9.8 m/𝑠 2 )
ℎ𝑚𝑎𝑥 : maximum still water depth
Reference: Imamura et al., 2006
16
Methods and Procedure
 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
17
 Introduction and Background
 Purpose of the Study
 Theories and Methods
 Bathymetry and Topography Data
 Scenario Earthquakes
 Computational Settings
 Results and Conclusions
18
Bathymetry and Topography Data
=
Topography and Bathymetry
Map (NAMRIA, 1952)
GEBCO 30 arc-sec +
Digitized Points
19
Bathymetry and Topography Data
Bathymetry data for tsunami arrival times and
tsunami heights calculations
GEBCO 1 arc-min
Bathymetry
GEBCO 30 arc-sec +
Digitized Bathymetry
20
Bathymetry and Topography Data
Bathymetry and topography data for
tsunami inundation calculations
+
GEBCO 30 arc-sec +
Digitized Bathymetry
SRTM_v2 Data
(N16-17˚E120-121˚)
21
 Introduction and Background
 Purpose of the Study
 Theories and Methods
 Bathymetry and Topography Data
 Scenario Earthquakes
 Computational Settings
 Results and Conclusions
22
Scenario Earthquake
Manila Trench Segment 2 (Salcedo, 2010)
Case 1 : Historical
Initial Condition:
Magnitude
: 7.6
Lat, Lon
: 16.06˚N,119.10˚E
Fault length: 97.52 km
Fault width : 53.21 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: -0.26 m
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Scenario Earthquake
Manila Trench Segment 2 (Salcedo, 2010)
Case 2 : Maximum Credible
Initial Condition:
Magnitude
: 8.4
Lat, Lon
: 16.06˚N,119.10˚E
Fault length: 254.0 km
Fault width : 91.10 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: -0.31 m
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 Introduction and Background
 Purpose of the Study
 Theories and Methods
 Bathymetry and Topography Data
 Scenario Earthquakes
 Computational Settings
 Results and Conclusions
25
Computational Settings
Location of Tide Stations
26
Computational Settings
For Tsunami Height and Tsunami
Travel Time
 Computational dimension: 14-20˚N,116.5-121˚E
 Computational time: 14400 s (4 hrs)
 Temporal grid size, ∆t: 3.0 s
 Spatial grid size: ∆x=1774.0, ∆y=1844.0
 Grid points: nx=270, ny=360
 ℎ𝑚𝑎𝑥 :5189 m (for GEBCO 1 arc-min)
 ℎ𝑚𝑎𝑥 :5183 m (for GEBCO 30 arc-sec)
 ℎ𝑚𝑎𝑥 :5181 m (for GEBCO 30 arc-sec
+ digitized map)
27
Computational Settings
28
Computational Settings
For Tsunami Inundation Computation
4 Regions
of
 Computational dimension: 14-20˚N,116.5-121˚E
 Computational time: 14400 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
29
Computational Settings
Region 1
Region 2
Region 3
Region 4
30
 Introduction and Background
 Purpose of the Study
 Theories and Methods
 Bathymetry and Topography Data
 Scenario Earthquakes
 Computational Settings
 Results and Conclusions
31
Results
1. Tsunami Waveforms
Case 1: Mw7.6
Case 2: Mw8.4
GEBCO 1 arc-min
GEBCO 30 arc-sec
32
Results
1. Tsunami Waveforms
Case 1: M7.6
Case 2: M8.4
GEBCO 30 arc-sec
GEBCO 30 arc-sec + digitized bathymetry
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Results
2. Tsunami Arrival Times
38 min
35 min
34
Results
3. Tsunami Maximum Heights
0.3 m
1.6 m
35
Results
3. Tsunami Maximum Heights
0.7 m
Case 1(Mw7.6)
2.8 m
Case 2(Mw8.4)
36
Results
4. Tsunami Inundation
Case 1(Mw7.6)
Max ht. : 0.7 m
Inun area: 0.13 𝒌𝒎𝟐
Case 2(Mw8.4)
Max ht. : 3.0 m
37 𝟐
Inun area: 0.7 𝒌𝒎
Results
4. Tsunami Inundation
Vertical + horizontal
effects
17%
Vertical
effects only
38
Results
5. Tsunami Sensor
Case 1: 8 min
Case 2: <1 min
Case 1: 15 min
Case 2: 11 min
Case 1: 36 min
Case 2: 37 min
Case 1: 44 min
Case 2: 45 min
39
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.
40
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.
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Thank you very much for your attention…