MACROSEISMIC SURVEY OF THE M7.9, 2002 DENALI FAULT EARTHQUAKE

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SURVEY RESULTS

The completed questionnaires were submitted to the USGS “Did You Feel It?” website for intensity calculations. The results were analyzed and visualized using GIS software. Appendix B provides the statistics for the questions 6-18. Table 1 provides the parameters of the 99 survey sites, including the geographic coordinates (rounded to three decimal places), distances to the fault rupture, decimal CII intensities, and corresponding MMI intensities. Overall, there are 29 intensity IX (CII ³ 8.5), 29 intensity VIII (7.5 £ CII < 8.5), 19 intensity VII (6.5 £ CII < 7.5), 17 intensity VI (5.5 £ CII < 6.5), and 5 intensity V (CII < 5.5) locations in the dataset. The distances from the fault rupture range from 2 to 127 km; 26 sites are within 20 km of the fault.

Table 1. Parameters of the macroseismic survey sites of the Denali Fault earthquake. Sites are ordered by increasing distance from the fault.

	Code	Location	Latitude	Longitude	Dist, km	CII	MMI
1	TC32	Mentasta Lake	62.933	-143.794	2	8.7	IX
2	TC33	Mentasta Lake	62.932	-143.797	2	8.2	VIII
3	TC34	Mentasta Lak e	62.932	-143.793	2	8.3	VIII
4	TC35	Mentasta Lake	62.931	-143.796	2	8.1	VIII
5	TC36	Mentasta Lake	62.930	-143.797	2	8.2	VIII
6	TC28	Tok Cutoff Hwy, MP83.5	62.930	-143.559	3	8.2	VIII
7	RH14	Richardson Hwy, MP219 (PS10)	63.424	-145.765	3	8.1	VIII
8	TC27	Tok Cutoff Hwy, MP78	62.888	-143.679	4	9.0	IX
9	TC43	Tok Cutoff Hwy, MP78.1	62.890	-143.682	4	9.1	IX
10	TC29	Tok Cutoff Hwy, MP88	62.936	-143.424	7	8.9	IX
11	TC45	Tok Cutoff Hwy, MP76	62.860	-143.672	7	7.4	VII
12	TC47	Tok Cutoff Hwy, MP89.5	62.945	-143.387	7	9.1	IX
13	RH01	Richardson Hwy, MP227	63.514	-145.853	10	7.4	VII
14	TC26	Tok Cutoff Hwy, MP72.3	62.821	-143.709	11	7.5	VIII
15	TC30	Tok Cutoff Hwy, MP91	62.962	-143.352	11	7.7	VIII
16	TC31	Tok Cutoff Hwy, MP91	62.964	-143.357	11	8.9	IX
17	TC24	Tok Cutoff Hwy, MP72	62.813	-143.725	12	9.1	IX
18	TC25	Tok Cutoff Hwy, MP71.8	62.814	-143.724	12	8.2	VIII
19	TC38	Tok Cutoff Hwy, MP71.7	62.810	-143.735	13	9.1	IX
20	SL08	Nabesna Rd, MP28.5	62.527	-143.241	15	7.6	VIII
21	SL07	Nabesna Rd, MP25	62.545	-143.325	16	9.0	IX
22	SL09	Nabesna Rd, MP42	62.396	-142.996	16	7.3	VII
23	TC21	Tok Cutoff Hwy, MP67.5	62.758	-143.804	19	8.6	IX
24	TC22	Tok Cutoff Hwy, MP67.5	62.758	-143.795	19	8.6	IX
25	TC41	Tok Cutoff Hwy, MP68	62.763	-143.794	19	7.2	VII
26	RH10	Richardson Hwy, MP195	63.148	-145.541	19	7.2	VII
27	TC39	Tok Cutoff Hwy, MP66.5	62.746	-143.808	21	5.8	VI
28	TC37	Tok Cutoff Hwy, MP65.5	62.733	-143.837	23	8.6	IX
29	TC44	Tok Cutoff Hwy, MP65.5	62.735	-143.836	23	8.6	IX
30	SL01	Nabesna  Road , MP15	62.601	-143.619	23	7.5	VIII
31	RH03	Richardson Hwy, MP191	63.107	-145.511	23	9.1	IX
32	TC18	Tok Cutoff Hwy, MP63	62.725	-143.914	25	9.1	IX
33	TC19	Tok Cutoff Hwy, MP63.5	62.725	-143.896	25	9.0	IX
34	TC20	Tok Cutoff Hwy, MP63.5	62.724	-143.890	25	8.2	VIII
35	TC42	Tok Cutoff Hwy, MP63.5	62.724	-143.893	25	9.1	IX
36	TC17	Tok Cutoff Hwy, MP61	62.719	-143.962	27	8.9	IX
37	TC40	Tok Cutoff Hwy, MP61	62.718	-143.961	27	9.1	IX
38	SL05	Slana	62.711	-143.966	28	8.9	IX
39	SL06	Slana	62.700	-143.937	28	9.0	IX
40	TC15	Tok Cutoff Hwy, MP58	62.717	-144.035	29	9.1	IX
41	TC16	Tok Cutoff Hwy, MP60	62.714	-143.992	29	8.6	IX
42	SL02	Slana	62.707	-143.968	29	8.1	VIII
43	SL03	Slana	62.674	-143.826	29	8.0	VIII
44	SL04	Slana	62.704	-143.964	29	7.6	VIII
45	RH05	Richardson Hwy, MP185	63.028	-145.492	31	7.2	VII
46	RH12	Paxson	63.030	-145.499	31	7.8	VIII
47	RH13	Paxson	63.033	-145.497	31	8.2	VIII
48	TC46	Tok Cutoff Hwy, MP53	62.710	-144.185	34	8.5	IX
49	RH15	Richardson Hwy, MP182.5	62.983	-145.497	36	8.2	VIII
50	RH04	Richardson Hwy, MP180	62.943	-145.518	41	6.0	VI
51	AK14	Alaska Hwy, MP1338	63.389	-143.740	43	6.5	VII
52	TC10	Tok Cutoff Hwy, MP40	62.644	-144.527	49	7.9	VIII
53	AK09	Alaska Hwy, MP1318.5	63.333	-143.130	53	6.1	VI
54	AK13	Tanacross	63.384	-143.349	53	8.9	IX
55	AK05	Alaska Hwy, MP1318	63.343	-143.109	54	6.6	VII
56	AK11	Tok	63.315	-143.008	54	6.6	VII
57	AK15	Alaska Hwy, MP1378	63.690	-144.552	54	4.8	V
58	AK02	Tok	63.328	-143.002	55	6.4	VI
59	AK04	Alaska Hwy, MP1317.5	63.345	-143.088	55	8.1	VIII
60	AK12	Alaska Hwy, MP1316	63.339	-143.056	55	6.4	VI
61	AK03	Tok	63.327	-142.952	56	8.2	VIII
62	AK06	Alaska Hwy, MP1315	63.340	-143.020	56	6.6	VII
63	AK08	Tok	63.336	-143.021	56	8.2	VIII
64	AK10	Tok	63.321	-142.954	56	5.3	V
65	TC13	Tok Cutoff Hwy, MP34.5	62.589	-144.650	57	6.5	VII
66	TC23	Tok Cutoff Hwy, MP34	62.583	-144.656	57	5.9	VI
67	TC09	Tok Cutoff Hwy, MP33	62.564	-144.668	58	5.5	VI
68	TC11	Tok Cutoff Hwy, MP33	62.566	-144.669	58	6.4	VI
69	TC12	Tok Cutoff Hwy, MP33	62.573	-144.662	58	6.5	VII
70	AK01	Tok	63.346	-142.969	58	6.7	VII
71	AK07	Tok	63.333	-142.921	58	7.9	VIII
72	AK20	Alaska Hwy, MP1399	63.865	-145.104	62	6.2	VI
73	AK16	Dot Lake	63.663	-144.062	63	7.8	VIII
74	AK18	Alaska Hwy, MP1404	63.901	-145.233	63	6.4	VI
75	AK17	Alaska Hwy, MP1412.5	63.962	-145.464	64	5.8	VI
76	AK19	Alaska Hwy, MP1403	63.914	-145.134	66	6.1	VI
77	RH09	Delta Junction	64.046	-145.735	67	7.3	VII
78	NW03	Northway	62.960	-141.943	67	9.0	IX
79	NW04	Northway	62.963	-141.929	67	9.1	IX
80	NW05	Northway	62.961	-141.941	67	8.0	VIII
81	NW06	Northway	62.963	-141.934	67	8.9	IX
82	NW07	Northway	62.962	-141.935	67	7.4	VII
83	RH11	Delta Junction	64.040	-145.743	68	6.0	VI
84	NW01	Northway Village	62.981	-141.952	68	8.6	IX
85	NW02	Northway Village	62.983	-141.956	68	7.7	VIII
86	AK21	Alaska Hwy, MP1264	63.010	-141.802	76	6.1	VI
87	RH06	Richardson Hwy, MP147.5	62.526	-145.520	84	8.4	VIII
88	TC07	Tok Cutoff Hwy, MP9	62.366	-145.155	91	5.8	VI
89	TC06	Tok Cutoff Hwy, MP8	62.361	-145.171	92	7.9	VIII
90	TC14	Gakona	62.301	-145.311	100	7.2	VII
91	TC02	Gakona	62.300	-145.311	101	5.4	V
92	TC03	Gakona	62.302	-145.311	101	7.1	VII
93	TC04	Tok Cutoff Hwy, MP2	62.302	-145.302	101	6.0	VI
94	TC05	Tok Cutoff Hwy, MP2.5	62.304	-145.274	101	7.8	VIII
95	RH07	Richardson Hwy, MP130.5	62.319	-145.356	101	4.8	V
96	TC01	Gakona	62.301	-145.315	102	7.0	VII
97	RH08	Richardson Hwy, MP115.5	62.117	-145.482	124	4.8	V
98	GL01	Glenn Hwy, MP183	62.109	-145.611	126	5.7	VI
99	GL02	Glenn Hwy, MP184	62.110	-145.570	127	6.8	VII

Table C1 (Appendix C) lists the USGS CII dataset for the DF earthquake, representing more than 3,197 responses from 57 zip codes in Alaska (zip codes with only one response are not considered). While these intensities are assigned to the zip codes as regions, in our analysis we need to attribute them to specific locations, which was done in the following way:

a) If the zip code covers a small area with a relatively uniform population distribution, then the intensities are attributed to the geographic centers of the corresponding zip codes

b) If the zip code covers a large area with a few population centers, then the intensities are attributed to the “population-weighted centers.” The population statistics were obtained from the 2000 Census database (www.census.gov). In one case (zip code 99586) however, it was not possible to represent the whole area with a single intensity value, since the rupture passed through the area. Therefore, there is a large intensity gradient within the zip code. This data point has been excluded from the analysis.

Thus, the combined GI-USGS dataset of the DF earthquake contains intensities for more than 155 locations (Figure 2). For mapping purposes we need to create a regular spatial grid of intensities. However, the attempts to create such a grid from the original data points alone did not produce reliable results because of very inhomogeneous spatial distribution. To resolve this problem, we first created a supporting temporary grid with 25 km spacing in which the intensity values were determined from the intensity-distance relationship provided in the next section. This size of the grid is such that it helps to generate smooth contour lines and preserves the spatial heterogeneity of the original data points at the same time.  The final intensity grid with 5 km spacing was produced on the basis of the original points and the supporting grid using the Kriging interpolation method. In the final interpolation, the USGS points were given weights proportional to the number of responses from the corresponding zip code.

Figure 2. Locations of the intensity survey sites. The GI and USGS survey sites are marked by circles and squares, accordingly (Click on Figure to see larger version).