DISCLAIMER -- THIS IS NOT AN EARTHQUAKE PREDICTION OR WARNING! The commentary provided with these map(s) is for INFORMATIONAL USE ONLY, and SHOULD NOT be construed as an earthquake prediction, warning, or advisory. Responsibility for such warnings rests with the Office of Emergency Services of the State of California. PLEASE REMEMBER -- THIS ARE PRELIMINARY DATA Releasing these summaries on a timely basis requires that the data, analysis, and interpretations presented are PRELIMINARY. Of necessity they can only reflect the views of the seismologists who prepared them, and DO NOT carry the endorsement of the U.S.G.S. Thus while every effort is made to ensure that the information is accurate, nothing contained in this report is to be construed as and earthquake prediction, warning, advisory, or official policy statement of any kind, of the U.S. Geological Survey, or the U.S. Government. FOR QUESTIONS CONCERNING THIS REPORT Send e-mail to andy@pangea.stanford.edu Seismicity Report for Northern California, the Nation, and the World for the week of June 17 - 23, 1993 Data and text prepared by Steve Walter, Barry Hirshorn, and Allan Lindh U.S. Geological Survey 345 Middlefield Rd. MS-977, Menlo Park, CA 94025 Graphics by Quentin Lindh San Francisco Bay Area Another quiet week in the Bay area. During the 7-day period ending at midnight on Wednesday, June 23, 1993 the U.S. Geological Survey office in Menlo Park recorded 14 earthquakes of magnitude one (M1) and greater within the San Francisco Bay area shown in Figure 1. Two of these were as large as M2.0. This total compares to 23 earthquakes during the previous week (June 10 - 16), two of which were as large as M2.0. What little notable activity there was this past week occurred on the San Andreas. First, a small cluster of three M1 earthquakes occurred early in the week on the Loma Prieta segment, about 12 miles west of Morgan Hill (#1 in figure 1). The largest of these was only M1.9. The only M2 earthquakes both occurred on the creeping segment of the San Andreas. The first of these was a M2.5 last Friday afternoon that was located about 2 miles south of San Juan Bautista (#2/1), about the same location as a M3.0 in November of last year. The second was a M2.1 on Wednesday that was located about six miles northwest of San Juan Bautista (#3/1). A M3.3 occurred in this same area in mid-February of this year. Northern & Central California Once again the Cape Mendocino area proved to be the most seismically active region in the state, producing a pair of M3's and half a dozen M2's. Much of the activity occurred along the Mendocino fracture zone, the boundary between the Pacific plate and the Gorda and North American plates. In this case most of the activity occurred earlier in the week between Thursday and Saturday. Two zones were active during this time with a trio of M2's located between 15 and 30 miles west of Petrolia (#1/2) and a trio of slightly larger events, capped by a M3.2, between 75 and 100 miles west of Petrolia (#2/2). Two earthquakes occurred on Saturday north of the fracture zone, in the Eureka area. The first was a M2.8 on Saturday morning that was located about 30 miles southeast of Eureka. It was followed that afternoon by a M3.5 that occurred along the coast just 12 miles southwest of Eureka and that was felt in the Eureka area (#4/2). As is often the case here, most of the earthquakes in this area had focal depths of between 20 and 30km, reflecting a source within the subducting Gorda plate. The rest of the state was pretty quiet with only a few M2's worth mentioning. Among these were a M2.7 beneath of Sierra Nevada foothills about 27 miles southwest of Yosemite Valley (#5/2), a M2.8 beneath the high Sierras about 16 miles southwest of Markleeville (#6/2), and a M2.3 on the San Andreas about 3 miles northwest of Parkfield (#7/2). Long Valley Caldera The western end of the south moat continued to be the most active area within the caldera with a half dozen small earthquakes during the week, the largest a M2.0 last Thursday morning (#1/3). The south side of the caldera in the vicinity of the Hilton Creek fault also experienced a few M1 earthquakes. South of the caldera there were a couple of small M2 events in the vicinity of Mt. Morrison (#2,#3/3). USA Seismicity According to data provided by the National Earthquake Information Center, the only notable earthquake in the lower 48 states, outside of California, was a M3.5 in western Arizona that was felt at Grand Canyon Village (#1/4). This is nearly the same location as a M5.5 that shook this area in late April. The Planet Earth (June 16 - 22) The Kermadec Islands region north of New Zealand was the most seismically active area on the planet during the week. This convergent boundary between the northwest moving Pacific plate and the north- northeasterly moving Australian plate produced at least nine moderate earthquakes during the week, the largest a pair of Ms6.7 events last Friday (#1/5). At least a dozen M6 events have occurred along this Kermadec-Tonga trench in the past year. Other moderate quakes in the southwest Pacific margin include a Mb5.2 in the Philippine Islands, a Ms5.6 in the Solomon Islands (#4/5), and a Mb5.3 in the eastern Papua New Guinea region. Two moderate quakes occurred in central Asia, the first a Mb5.4 in the Hindu Kush region of northeastern Afghanistan (#2/5), the second a Mb5.6 along the southwestern coast of Iran (#5/5). Activity in the western hemisphere was largely restricted to central America. A Mb5.1 occurred near the coast of Chiapas Mexico and a Mb4.7 occurred just off the Nicaraguan coast. The largest earthquake in the region was a Ms5.3 on the east Pacific Rise southwest of Mexico (#3/5). Table 1. Northern & Central California Seismicity (M>1.0) --ORIGIN TIME (UT)-- -LAT N-- --LON W-- DEPTH N N RMS ERH ERZ DUR YR MON DA HRMN SEC DEG MIN DEG MIN KM RD S SEC KM KM REMKS MAG 93 JUN 17 809 41.19 40 24.36 124 38.51 24.86 12 1 .10 2.1 1.7 MEN- 2.0 93 JUN 17 839 40.57 40 25.05 125 41.70 21.86 21 1 .4110.323.6 MEN-- 2.6 93 JUN 17 922 1.47 37 38.54 118 55.13 8.48 30 4 .13 .4 .4 SMO 2.1 93 JUN 17 937 29.82 37 38.67 118 55.04 7.61 8 .02 .7 1.1 SMO 1.0 93 JUN 17 1017 21.86 37 33.30 118 50.52 3.56 18 .07 .3 .9 MOR 1.6 93 JUN 17 1334 3.76 37 38.47 118 55.10 6.09 8 .07 .6 1.3 SMO 1.4 93 JUN 17 1334 25.88 37 38.73 118 55.07 9.05 16 2 .11 .5 .9 SMO 1.7 93 JUN 17 1342 57.78 37 38.65 118 55.32 7.48 15 1 .04 .4 .6 SMO 2.0 93 JUN 17 1638 15.01 37 6.36 121 52.15 5.59 43 2 .09 .2 .3 LOM 2.1 93 JUN 17 1706 44.23 37 27.09 118 22.68 10.04 22 1 .09 .3 .7 CHV 1.8 93 JUN 17 1740 57.63 37 6.27 121 52.16 5.42 22 .08 .3 .5 LOM 1.2 93 JUN 17 2154 48.88 36 38.49 121 15.16 4.02 28 .08 .2 .6 STN 2.0 93 JUN 17 2213 53.62 37 47.08 118 9.91 2.85 14 2 .11 1.5 2.9 WHI- 1.7 93 JUN 17 2226 21.42 38 47.25 122 46.33 2.43 7 .03 .3 .8 GEY 1.4 93 JUN 18 6 32.64 37 45.54 118 11.12 0.43 9 1 .07 2.9 2.1 WHI- 1.4 93 JUN 18 26 26.82 36 2.50 120 35.03 4.63 21 3 .09 .4 .5 SLA 1.6 93 JUN 18 208 2.65 37 0.87 121 27.87 5.65 18 1 .06 .3 .5 CYS 1.1 93 JUN 18 255 28.28 37 25.05 118 33.34 7.74 24 3 .07 .3 .6 RVL 1.6 93 JUN 18 320 34.25 40 18.25 124 36.13 20.06 16 1 .13 1.4 .6 MEN 2.2 93 JUN 18 326 14.84 38 47.31 122 45.41 1.76 13 .03 .2 .6 GEY 1.3 93 JUN 18 344 12.26 38 50.46 122 49.37 2.22 10 .03 .3 .8 GEY 1.2 93 JUN 18 423 17.90 39 18.55 123 18.76 0.78 12 2 .08 .3 1.9 MAA- 1.2 93 JUN 18 443 13.24 37 47.92 118 8.51 0.35 29 .11 1.7 6.6 NEV- 2.6 93 JUN 18 626 12.23 36 28.15 121 2.70 6.40 15 2 .06 .3 .7 BIT 1.1 93 JUN 18 825 43.69 36 24.29 120 58.76 5.58 41 3 .08 .2 .6 BIT 2.0 93 JUN 18 916 36.14 38 47.57 122 45.20 1.97 7 .10 .5 1.2 GEY 1.2 93 JUN 18 925 11.99 38 49.74 122 47.94 2.19 18 .15 .4 .8 GEY 1.4 93 JUN 18 1210 38.71 37 37.28 119 25.35 9.08 42 4 .15 .6 2.7 KAI- 2.1 93 JUN 18 1218 36.13 37 37.38 119 25.75 8.37 10 2 .13 .811.9 KAI - 1.2 93 JUN 18 1240 22.81 37 37.21 119 25.15 7.28 16 4 .20 .712.5 KAI * 1.6 93 JUN 18 1316 39.55 37 37.41 119 25.63 7.27 9 2 .11 1.012.0 KAI - 1.7 93 JUN 18 1348 10.38 38 47.26 122 45.38 2.11 10 .04 .3 .7 GEY 1.4 93 JUN 18 1352 12.77 36 56.16 121 31.21 3.22 38 1 .19 .3 .7 SAR 1.5 93 JUN 18 1449 9.89 37 25.51 121 46.21 8.16 40 2 .05 .2 .4 ALU 1.8 93 JUN 18 1500 35.28 40 38.54 123 35.98 26.53 30 2 .12 .3 .6 EUR 2.9 93 JUN 18 1544 29.10 36 39.24 120 49.49 2.67 10 1 .07 .8 1.3 ORT 1.0 93 JUN 18 1547 15.32 40 38.62 123 34.91 24.48 9 1 .16 .9 1.7 EUR 1.9 93 JUN 18 1730 20.01 38 51.35 122 49.43 1.51 9 .05 .4 .8 GEY 1.5 93 JUN 18 1905 29.78 37 14.37 119 28.96 43.88 9 2 .12 1.1 1.1 KAI 2.2 93 JUN 18 2037 31.69 36 2.27 120 34.68 4.19 12 2 .09 .5 .9 SLA 1.2 93 JUN 18 2145 36.16 37 31.01 118 25.24 8.53 16 .03 .3 .6 CHV 1.4 93 JUN 18 2336 28.88 36 49.03 121 32.33 5.59 65 4 .20 .3 .5 SJB 2.6 93 JUN 19 52 24.06 40 40.35 124 20.14 24.81 25 2 .08 .5 1.2 EUR 3.6 93 JUN 19 119 32.11 38 49.16 122 48.76 3.79 11 .06 .4 .6 GEY 1.4 93 JUN 19 145 8.68 37 6.28 121 52.18 5.33 30 1 .10 .2 .5 LOM 1.5 --ORIGIN TIME (UT)-- -LAT N-- --LON W-- DEPTH N N RMS ERH ERZ DUR YR MON DA HRMN SEC DEG MIN DEG MIN KM RD S SEC KM KM REMKS MAG 93 JUN 19 426 23.00 40 25.82 125 46.62 16.36 28 1 .30 7.712.5 MEN- 3.1 93 JUN 19 637 51.65 37 39.21 118 56.29 4.49 13 .11 .5 .7 SMO 1.5 93 JUN 19 708 37.12 40 27.75 126 14.62 5.69 20 1 .27 7.5 7.2 PON 2.9 93 JUN 19 833 55.75 37 27.93 119 57.24 11.83 11 3 .19 1.0 3.3 KAI 3.8 93 JUN 19 1110 45.40 37 3.78 121 31.05 3.16 43 4 .10 .2 .5 CYS 1.2 93 JUN 19 1116 44.71 38 47.39 122 46.88 3.96 14 .06 .3 .6 GEY 1.1 93 JUN 19 1124 52.64 37 4.05 121 30.43 6.92 19 3 .15 .5 1.3 CYS 1.0 93 JUN 19 1232 50.06 37 28.87 121 37.78 6.47 16 .04 .2 .6 HAM 1.6 93 JUN 19 1507 33.22 38 49.45 122 46.25 1.05 9 .02 .2 .7 GEY 1.3 93 JUN 19 1613 35.89 38 49.01 122 48.56 3.67 8 .03 .4 .8 GEY 1.2 93 JUN 19 1631 20.80 38 49.57 122 46.74 3.22 10 .03 .3 .7 GEY 1.4 93 JUN 19 1650 8.05 37 42.57 118 49.47 16.30 8 .15 4.5 6.5 NMO 1.1 93 JUN 19 1802 52.52 37 38.67 118 52.81 7.03 9 .07 .7 .9 SMO 1.1 93 JUN 20 10 0.63 37 38.99 118 56.14 4.13 13 .08 .4 .7 SMO 1.5 93 JUN 20 24 28.88 36 36.54 121 12.33 3.87 14 .07 .3 1.3 PIN 1.9 93 JUN 20 35 43.37 37 39.02 118 54.85 7.93 11 .08 .7 .7 DOM 1.4 93 JUN 20 125 21.01 38 48.06 122 44.31 2.36 10 .05 .3 .8 GEY 1.4 93 JUN 20 214 54.17 40 0.30 123 28.15 0.11 10 .18 1.0 4.3 BAR * 1.7 93 JUN 20 550 50.84 38 49.36 122 46.90 3.07 7 .01 .3 .8 GEY 1.2 93 JUN 20 636 25.20 40 26.02 124 54.45 22.80 8 .11 6.212.3 MEN - 2.4 93 JUN 20 640 51.83 38 49.47 122 49.51 0.72 11 .08 .3 .9 GEY 1.5 93 JUN 20 742 36.19 37 29.78 118 48.42 8.20 23 .11 .5 1.5 MOR 2.0 93 JUN 20 1126 22.15 37 33.31 118 52.38 7.06 25 .11 .4 .9 MOR 2.1 93 JUN 20 1219 42.89 36 0.99 120 34.35 5.07 16 .11 .4 .7 SLA 1.7 93 JUN 20 1237 43.81 38 49.35 122 49.93 0.04 8 .14 .6 2.6 GEY * 1.5 93 JUN 20 1255 53.47 37 34.40 118 28.02 9.09 15 .06 .3 .8 CHV 2.1 93 JUN 20 1454 30.40 38 49.53 122 47.56 2.27 15 .05 .2 .4 GEY 1.6 93 JUN 20 1955 34.67 38 47.61 122 46.50 2.29 9 .02 .3 .6 GEY 1.4 93 JUN 20 2038 11.48 37 37.90 118 53.01 6.28 13 .08 .4 .6 SMO 1.4 93 JUN 20 2346 15.15 38 40.19 122 48.31 9.04 11 .13 .6 1.7 NAP 1.2 93 JUN 21 255 41.22 38 48.63 122 48.23 2.97 19 .06 .2 .5 GEY 1.9 93 JUN 21 439 0.66 37 21.41 118 23.15 9.01 12 .09 .5 1.5 OWV 1.8 93 JUN 21 444 1.59 38 50.91 122 49.05 1.58 11 .04 .3 .8 GEY 1.5 93 JUN 21 457 31.84 38 47.71 122 45.00 0.46 11 .06 .2 .8 GEY 1.6 93 JUN 21 458 45.85 38 47.68 122 45.01 0.83 8 .05 .3 1.0 GEY 1.2 93 JUN 21 817 53.59 37 38.44 118 52.76 6.65 11 .07 .6 .8 SMO 1.0 93 JUN 21 923 2.17 38 49.02 122 48.56 3.98 16 .02 .2 .6 GEY 2.3 93 JUN 21 924 32.18 37 39.72 118 50.95 5.76 9 2 .07 .6 1.7 DOM 1.1 93 JUN 21 1106 15.49 38 38.46 122 43.44 5.84 11 .10 .5 1.3 NAP 1.6 93 JUN 21 1137 36.30 37 36.86 118 48.99 5.20 16 .12 .4 .7 HCF 1.9 93 JUN 21 1348 24.15 37 36.83 118 48.91 5.17 17 .11 .4 .6 HCF 1.9 93 JUN 21 1555 57.00 37 38.62 118 57.04 7.04 10 2 .02 .7 .9 SMO 1.0 93 JUN 21 1622 42.70 37 37.01 118 49.39 5.67 17 1 .11 .4 .6 HCF 1.6 93 JUN 21 1639 37.50 38 48.07 122 47.33 1.10 7 .04 .3 .5 GEY 1.0 93 JUN 21 2059 14.59 38 49.29 122 48.43 3.86 14 .08 .3 .7 GEY 1.7 --ORIGIN TIME (UT)-- -LAT N-- --LON W-- DEPTH N N RMS ERH ERZ DUR YR MON DA HRMN SEC DEG MIN DEG MIN KM RD S SEC KM KM REMKS MAG 93 JUN 21 2131 58.56 38 47.04 122 45.38 1.25 7 .07 .3 1.0 GEY 1.0 93 JUN 21 2304 8.44 38 48.72 122 49.65 1.54 13 .11 .3 .8 GEY 1.7 93 JUN 21 2317 7.21 37 21.36 118 22.91 10.27 8 .07 .5 1.3 OWV 1.5 93 JUN 21 2357 38.06 38 49.29 122 48.33 4.14 29 .08 .2 .5 GEY 2.2 93 JUN 22 541 0.38 38 30.86 119 58.04 18.74 8 .1510.1 4.8 YOS - 2.8 93 JUN 22 742 18.08 37 38.73 118 55.25 6.81 12 .10 .6 .8 SMO 1.5 93 JUN 22 743 19.98 37 38.29 118 55.34 6.20 8 .03 .8 1.5 SMO 1.1 93 JUN 22 743 42.32 37 38.41 118 55.21 7.20 16 .09 .4 .6 SMO 1.8 93 JUN 22 744 19.54 37 38.11 118 55.15 6.85 7 .02 .7 1.0 SMO 1.1 93 JUN 22 752 36.82 37 38.43 118 55.20 6.89 14 .08 .4 .8 SMO 1.4 93 JUN 22 951 46.29 37 39.54 118 55.05 7.73 9 .12 1.0 1.8 DOM 1.0 93 JUN 22 1341 30.87 37 8.88 121 33.16 2.43 16 .04 .3 .7 CYN 1.4 93 JUN 22 1406 58.31 40 32.13 123 55.77 20.29 8 .09 .7 .7 EUR 1.9 93 JUN 22 1525 19.10 38 49.60 122 47.57 0.92 8 .08 .4 .8 GEY 1.9 93 JUN 22 1550 0.74 38 46.97 122 45.52 1.25 12 .05 .3 .6 GEY 1.5 93 JUN 22 1629 2.03 37 31.39 118 50.18 0.04 8 .05 .9 .5 MOR * 1.5 93 JUN 22 1758 49.65 38 48.58 122 48.59 3.78 16 .04 .2 .5 GEY 1.9 93 JUN 22 2031 34.80 38 48.04 122 47.05 0.46 10 .04 .3 .5 GEY 1.8 93 JUN 22 2032 13.15 38 48.16 122 47.14 0.06 8 .09 .3 2.1 GEY * 1.4 93 JUN 23 49 56.75 38 48.59 122 48.89 3.67 10 .11 .4 1.1 GEY 1.2 93 JUN 23 307 43.44 39 28.58 122 59.79 8.05 11 .03 .3 .8 BAR 1.9 93 JUN 23 337 15.69 37 40.41 118 52.24 6.06 9 1 .18 1.0 1.6 DOM 1.1 93 JUN 23 517 53.58 37 52.10 118 10.61 2.64 13 .10 2.4 4.9 NEV 2.2 93 JUN 23 540 10.38 37 18.63 121 40.84 6.14 19 .04 .2 .6 SFL 1.4 93 JUN 23 547 49.82 37 37.42 118 49.86 8.88 10 1 .09 .6 .9 HCF 1.5 93 JUN 23 910 0.52 35 55.44 120 28.68 5.43 40 .13 .3 .4 MID 2.3 93 JUN 23 930 8.59 35 55.56 120 28.45 5.34 11 .02 .5 .4 MID 1.3 93 JUN 23 1454 30.32 37 33.96 121 40.64 4.11 11 .07 .3 .5 HAM 1.3 93 JUN 23 1639 58.01 37 34.40 118 48.75 2.50 16 1 .10 .4 1.9 MOR 1.8 93 JUN 23 1848 56.51 38 47.22 122 45.43 0.04 9 1 .10 .3 1.1 GEY 1.6 93 JUN 23 2038 18.10 36 54.11 121 37.30 0.02 21 .11 .2 .8 SJB * 2.1 93 JUN 24 437 50.45 35 50.08 119 53.28 6.64 10 .10 1.6 .9 COA 2.0 TABLE 2. Data from National Earthquake Information Center (NEIC) UTC TIME LAT LONG DEP GS MAGS SD STA REGION AND COMMENTS HRMNSEC MB Msz USED ------------------------------------------------------------------------------- JUN 16 054449.3 14.729N 92.770W 57D 5.1 1.0 65 NEAR COAST OF CHIAPAS, MEXICO 224449.8* 51.217N 159.337E 33N 4.8 1.0 17 OFF EAST COAST OF KAMCHATKA JUN 17 022416.2& 60.110N 152.500W 87 47 SOUTHERN ALASKA. . ML 2.5 154838.1 20.209N 120.406E 33N 5.2 1.0 30 PHILIPPINE ISLANDS REGION 165300.8& 63.450N 152.110W 18 33 CENTRAL ALASKA. . ML 2.6 JUN 18 084520.0? 28.33 S 176.89 W 33N 5.1 5.3 1.3 30 KERMADEC ISLANDS REGION. 115238.1* 28.485S 176.948W 33N 5.6 6.7 1.1 84 KERMADEC ISLANDS REGION. 173831.4* 28.416S 176.889W 33N 5.4 6.0 0.9 46 KERMADEC ISLANDS REGION 175750.4 28.422S 176.975W 33N 5.9 6.7 0.9 83 KERMADEC ISLANDS REGION. 193439.4* 28.710S 176.741W 33N 5.3 6.0 1.0 24 KERMADEC ISLANDS REGION 195901.1* 36.408N 70.643E 210D 5.4 0.8 31 HINDU KUSH REGION, AFGHANISTAN 205502.5* 28.528S 176.863W 33N 5.3 5.4 1.1 34 KERMADEC ISLANDS REGION JUN 19 005225.3 40.508N 123.902W 10G 1.1 16 NORTHERN CALIFORNIA. ML 3.0 (GS). Felt at Eureka. 023231.9 36.032N 141.776E 33N 4.6 0.7 32 NEAR EAST COAST OF HONSHU, JAPAN 100203.6* 2.184S 137.132E 33N 5.0 4.5 1.1 17 IRIAN JAYA, INDONESIA 110905.8? 11.08 N 86.57 W 33N 4.7 1.1 41 NEAR COAST OF NICARAGUA 122327.2* 9.801N 103.551W 10G 5.2 5.3 1.0 61 OFF COAST OF MEXICO 153301.3* 27.943S 176.755W 33N 5.5 5.8 0.9 50 KERMADEC ISLANDS REGION 185226.3* 28.222S 176.641W 33N 5.0 0.7 14 KERMADEC ISLANDS REGION JUN 20 022250.2? 28.89 S 176.48 W 33N 5.5 5.6 0.8 47 KERMADEC ISLANDS REGION 172630.6* 6.736S 155.544E 33N 5.2 5.6 1.0 27 SOLOMON ISLANDS 185128.9 5.633S 146.391E 104D 5.3 1.0 30 EASTERN NEW GUINEA REG., P.N.G. JUN 21 083607.9 35.992N 112.313W 5G 0.5 19 WESTERN ARIZONA. ML 3.5 (GS). Felt at Grand Canyon Village. 165448.6* 49.131N 150.514E 348D 4.9 0.8 73 NORTHWEST OF KURIL ISLANDS JUN 22 163244 Q 30.1 N 50.7 E 33N 5.6 0.9 38 NORTHERN IRAN Notes: Origin time in the list is in GMT, in the text and on maps it is in local time. N RD: is the number of readings used to locate the event. N S: is the number of S waves in N RD. RMS SEC: is the root mean squared residual misfit for the location is seconds, the lower the better, over 0.3 to 0.5 seconds is getting bad, but this is machine, not hand timed, data. ERH: is the estimated horizontal error in kilometers. ERZ: is the estimated vertical error in kilometers. N FM: is the number of readings used to compute the magnitude. REMKS: obtuse region codes that denote the velocity model used to locate the event. DUR MAG: is the magnitude as determined from the duration of the seismograms, not the amplitude. Sort of like going to echo canyon and measuring how loud your yell is by counting echos. FIG: denotes the figure/event number in the maps posted separately.