Predicting
when an earthquake will occur can be very difficult, likewise with tsunamis.
While we may not be able to predict them, we can at least create models to aid
in preparedness in the event that one does occur. FEMA's HAZUS software allows
us to do just that with the power of ArcGIS® 10.5.1. In this project I decided
to revisit my two study areas in Anchorage and Los Angeles from my second
project (Figure 1). I went with HAZUS since modeling tsunamis
requires extensive maths and the modeling software TSUNAMI-N2 by Goto et al.,
1997 is written in FORTRAN. HAZUS is quite large, power, and complex.
 |
| Figure 1 - Location of both study areas. The Anchorage study area includes parts of both Anchorage and Matanuska-Susitna counties. The Los Angeles study area encompasses the entirety of Los Angeles County to include both Catalina and San Clemente Islands. |
To model the tsunamis, I gave HAZUS default parameters laid
out in the HAZUS Tsunami User Manual. I set the maximum runup to 20m for
both study areas. I was expecting Anchorage to get completely inundated and
coastal California to be protected by the coastal cliffs. My predictions were
incorrect (Figures 2 and 3). Tables 1 & 2 compared damages and casualties.
Table 1 – Tsunami Damage to Buildings by
Count by General Occupancy
Agriculture
|
Commercial
|
Education
|
Government
|
|
Anchorage
|
32
|
978
|
72
|
12
|
Los
Angeles
|
57
|
110
|
3
|
1
|
Industrial
|
Religion/Non-Profit
|
Residential
|
Total
|
|
Anchorage
|
164
|
26
|
3488
|
1094
|
Los
Angeles
|
657
|
9
|
44780
|
171
|
Table 2 - Tsunami Casualties by Community Preparedness
Community
Preparedness
|
||||||
Day
|
Good
|
Fair
|
||||
Fatalities
|
Injuries
|
Total
Casualties
|
Fatalities
|
Injuries
|
Total
Casualties
|
|
Anchorage
|
8602
|
1055
|
9657
|
10533
|
665
|
11198
|
Los Angeles
|
1005899
|
71948
|
1077847
|
2412297
|
70164
|
2482461
|
Day
|
Poor
|
|||||
Fatalities
|
Injuries
|
Total
Casualties
|
||||
Anchorage
|
11137
|
397
|
11534
|
|||
Los Angeles
|
5465410
|
62210
|
5527620
|
|||
Night
|
Good
|
Fair
|
||||
Fatalities
|
Injuries
|
Total
Casualties
|
Fatalities
|
Injuries
|
Total
Casualties
|
|
Anchorage
|
7355
|
1362
|
8717
|
9981
|
973
|
10954
|
Los Angeles
|
1001019
|
71720
|
1072739
|
2357493
|
68267
|
2425760
|
Night
|
Poor
|
|||||
Fatalities
|
Injuries
|
Total
Casualties
|
||||
Anchorage
|
10937
|
577
|
11514
|
|||
Los Angeles
|
5304326
|
60138
|
5364464
|
 |
| Figure 2 - Tsunami runup in the Anchorage area. Surprisingly, most of Anchorage is untouched. I hadn't realized that most of Anchorage actually sits at about 100' of elevation. |
 |
| Figure 3 - Tsunami Runup in Los Angeles County, California. I expected the coastal cliffs to provide more protection, however certain low lying areas such as Venice (1), Long Beach (2), Huntington Beach (3), and Newport Beach (4) would experience the effects of a tsunami. Movement along the San Andreas fault would NOT cause a tsunami, however movement along the Catalina fault certainly could. |
Similar to the tsunami model, I followed a basic earthquake
model, though with some modifications. For Anchorage I set the earthquake model
to Alaska or Puerto Rico / VI – Reverse
as I assumed a reverse fault would rupture given Alaska is in an active
subduction zone. For Los Angeles I ran two models, one strike-slip for the San
Andreas fault and one reverse for the Catalina fault. Table 3 compares
casualties Table 4 shows damages to buildings.
Table 3 - Combined Earthquake Economic
Loss and Casualties in Magnitude 7 Event
Economic
Loss - Buildings ($)
|
Economic
Loss - Transportation
($)
|
|
Anchorage
|
2,909,951,000
|
182,302,000
|
Los
Angeles (strike-slip)
|
7,933,660,000
|
69,821,000
|
Los
Angeles (reverse)
|
4,340,831,000
|
73,512,000
|
Economic
Loss - Utilities ($)
|
Shelter
Req's (# people)
|
|
Anchorage
|
0
|
1647
|
Los
Angeles (strike-slip)
|
16,480,000
|
2234
|
Los
Angeles (reverse)
|
6,150,000
|
791
|
Anchorage
|
Casualties
- 2am
|
Casualties
- 2pm
|
Los
Angeles (strike-slip)
|
454
|
1250
|
Los
Angeles (reverse)
|
1231
|
362
|
472
|
902
|
|
Anchorage
|
Casualties
- 5pm
|
|
Los
Angeles (strike-slip)
|
867
|
|
Los
Angeles (reverse)
|
1959
|
|
627
|
Table 4 - Earthquake Damage to Buildings
by Count by General Occupancy
Location
|
Agriculture
|
Commercial
|
Education
|
Government
|
Industrial
|
Anchorage
|
5033
|
2916
|
110
|
178
|
762
|
Los
Angeles (strike-slip)
|
425
|
16916
|
511
|
275
|
4770
|
Los
Angeles (reverse)
|
269
|
13491
|
360
|
232
|
3855
|
Location
|
Other
Residential
|
Religion
|
Single
Family
|
Total
|
|
Anchorage
|
8127
|
258
|
91922
|
8999
|
|
Los
Angeles (strike-slip)
|
29377
|
1242
|
177547
|
22897
|
|
Los
Angeles (reverse)
|
21409
|
1002
|
96055
|
18207
|
 |
| Figure 4 - Ground motion in Anchorage at 1 second (top) and 0.3 seconds (bottom). |
 |
| Figure 5 - Ground motion due to movement along the San Andreas fault at 1 second (top) and 0.3 seconds (bottom). |
 |
| Figure 6 - Ground motion due to movement of a reverse fault offshore at 1 second (top) and 0.3 seconds (bottom). |
In conclusion, HAZUS can provide some useful data for
predicting what could happen and where. The model predicts that casualties due
to an earthquake would be much lower than those from a tsunami, however
building damages from an earthquake would be much more devastating. A link to
the report can be found here.
