HAZUS, Earthquakes, and Tsunamis

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.