U.S. Department of the Interior Denali Park, Alaska ...
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180° 170° 160° 150° 140° 130° 50° 60° 70° 50° 60° 70° 180° 170° 160° 150° 140° 130° A l a s k a R a n g e B r o o k s R a n g e A l e u t i a n R a n g e Anchorage Fairbanks Juneau B E R I N G S E A P A C I F I C O C E A N A R C T I C O C E A N A l e u t i a n I s l a n d s Chu ga c h M tn s. Gulf of Alask a C H U K C H I S E A Kodiak I. St. Lawrence I. Nunivak I. Fox Is la nd s An d rea n o f I sl an ds N o r t h S l o p e Unimak I. Q u ee n Cha rlotte Is. Coas t R ange Nome 151° 150° 149° 148° 147° 146° 145° 144° 143° 142° 141° 151° 150° 149° 148° 147° 146° 145° 144° 143° 142° 141° 60° 61° 62° 63° 64° 65° 60° 61° 62° 63° 64° 65° Anchorage Fairbanks G u l f o f A l a s k a P r i n c e W i l l i a m S o u n d C o o k I n l e t D e n a l i T o t s c h u n d a F a u l t F a u l t Co p p e r R i ve r C h u g a c h M o u n t a i n s K e n a i M o u n t a i n s A l a s k a R a n g e S usi t n a R i v e r D e l t a R i v e r T a na n a R i v er Denali NP and NPRES Yukon Charley Rivers NPRES Kenai Fjords NP Fox Eyak Orca Hope Knik Eska Berg Curry Slana Moody Healy Ferry Clear Bluff Eagle Ester Baker Seward Lawing Saxton Palmer Willow Sutton Gakona Paxson Tetlin Denali Summit Julius Toklat Nenana Dunbar Martin Woodrow Crystal Cordova Sunrise Ellamar Rainbow Eklutna Susitna Wasilla Pittman Houston Tonsina Caswell Tazlina Chisana Montana Gulkana Hufmans Glacier Chicken Liberty Caribou Latouche Lakeview Sterling Tatitlek Bay City Nelchina Sunshine Northway McCallum Cantwell Boundary Franklin Anderson Big Horn Tolovana Birchwood Alexander Matanuska Kashwitna McDougall Talkeetna Sourdough Tanacross Mansfield Jack Wade Big Delta Old Minto Moose Pass Jonesville Chickaloon Glennallen Broad Pass Kantishina Kechumstuk South Fork Richardson Dome Creek Port Ashton Gilpatricks Eagle River Petersville Chistochina Slate Creek Denali Park Moose Creek Old Saulich Alder Creek Flume Creek Peters Creek Tok Junction Steele Creek North Nenana Cape Yakataga Lower Tonsina Copper Center Tyone Village Mentasta Lake Eagle Village Crooked Creek Cooper Landing Indian Village Delta Junction Tetlin Junction Cathedral Rapids Northway Junction Upper Slate Creek Hot Springs Landing Denali Park, Alaska Earthquake of 3 November, 2002 EXPLANATION 23 October 2002 Mw = 6.7 3 November 2002 Mw = 7.9 Aftershocks 23 Oct - 2 Nov 2002 3 - 15 Nov 2002 Quaternary Faults 23 October 2002 3 November 2002 No Rupture Magnitude Classes M < 1.0 1.0 - 2.0 2.0 - 3.0 3.0 - 4.0 4.0 - 5.0 5.0 - 6.0 Urbanized Areas Anchorage Populated Places Tok Junction Roads Primary Secondary Unpaved Connector Railroads Airports Active Civil Active Military Other Glacier National Parks Trans-Alaska Pipeline 0 20 40 60 80 10 Kilometers 0 20 40 60 80 10 Miles SCALE 1:1,500,000 Albers Equal-Area Projection Map prepared by U.S. Geological Survey National Earthquake Information Center 21 November 2002 Map not approved for release by Director 3 November 2002 22:12:41.0 UTC 63.520 N., 147.533 W. Depth 5 km (Geophysicist) Mw = 7.9 (USGS) One person injured and extensive damage to roads. Items knocked from shelves in Denali National Park, Glenallen and Tok. Some supports on the trans-Alaska pipeline were damaged and operation was suspended. Damage estimated at 20 million U.S. dollars. Felt widely in northern British Columbia, western Alberta and Northwest Territories. Also felt by people in high-rise buildings in Seattle, Washington. Seiches and muddied water wells observed in a number of states, including Washington, Idaho, Louisiana, Oklahoma, Missouri, Wisconsin and Pennsylvania. The faulting mechanism for the earthquake was complex, consisting of a sequence at least two sub-events. It appears that the first sub- event ruptured on a short thrust fault south of the main strand of the Denali Fault which subsequently ruptured with right- lateral strike- slip motion as the much larger second sub-event. Preliminary geologic observations indicate offsets as much as 9 m on the Denali Fault. 23 October 2002 11:27:19.3 UTC 63.576 N., 148.088 W. Depth 14 km (Geophysicist) Mw = 6.7 (USGS) 180° 170° 160° 150° 140° 130° 50° 60° 70° 50° 60° 70° 180° 170° 160° 150° 140° 130° A l a s k a R a n g e B r o o k s R a n g e A l e u t i a n R a n g e A l e u t i a n T r e n c h Anchorage Fairbanks Juneau B E R I N G S E A P A C I F I C O C E A N A R C T I C O C E A N A l e u t i a n I s l a n d s Chu ga c h M tn s. Gul f of Alask a C H U K C H I S E A Kodiak I. St. Lawrence I. Nunivak I. Fox Isl a n ds An d rean o f I sl an ds N o r t h S l o p e A l e u t i a n Unimak I. B a s i n Quee n C ha rl otte Is . Coas t R ange 53 mm/yr 61 mm/yr 69 mm/yr 0 100 200 300 400 50 Kilometers SCALE 1:15,000,000 Albers Equal-Area Projection 0 100 200 300 400 50 Kilometers SCALE 1:15,000,000 Albers Equal-Area Projection EXPLANATION 3 November 2002 Mw = 7.9 Volcanoes Plate Boundaries Convergent Divergent Transform Major Faults Peak Ground Acceleration 0.0 - 0.2 m/sec**2 0.2 - 0.4 0.4 - 0.8 0.8 - 1.6 1.6 - 3.2 3.2 - 6.4 6.4 - 9.7 EXPLANATION 3 November 2002 Mw = 7.9 Plate Boundaries Convergent Divergent Transform Major Faults Volcanoes Plate Tectonic Setting Generalized Seismic Hazard 180° 170° 160° 150° 140° 130° 50° 60° 70° 50° 70° 180° 170° 160° 150° 140° 130° A l a s k a R a n g e B r o o k s R a n g e A l e u t i a n R a n g e Anchorage Fairbanks Juneau B E R I N G S E A P A C I F I C O C E A N A R C T I C O C E A N A l e u t i a n I s l a n d s C hug a c h M tn s. Gul f of Alask a C H U K C H I S E A Kodiak I. St. Lawrence I. Nunivak I. Fox Isl a n ds An d rean o f I sl an ds N o r t h S l o p e Unimak I. Quee n C ha rl otte Is . Coas t R ange 1929 1957 1986 1946 1917 1938 1972 1900 1988 1958 1987 1979 1964 2002 Seismic History 1900 - 2002 0 100 200 300 400 50 Kilometers SCALE 1:15,000,000 Albers Equal-Area Projection EXPLANATION 3 November 2002 Mw = 7.9 Depth Classes 0 - 70 km Depth > 70 km Magnitude Classes 6.0 - 7.0 7.0 - 8.0 8.0 - 9.0 M >9.0 Plate Boundaries Convergent Divergent Transform Major Faults Volcanoes Seismic hazard is expressed as peak ground acceleration (PGA) in meters/sec**2 ex- pected in a 50-yr period with a probability of 10 percent. DATA SOURCES EARTHQUAKES AND SEISMIC HAZARD USGS, National Earthquake Information Center Alaska Earthquake Information Center IASPEI, Centennial Catalog (1900 - 1999) Handbook of Seismology and Earthquake Engineering Global Seismic Hazard Assessment Program FAULTS USGS, Anchorage and Denver PLATE TECTONICS Smithsonian Institution, Global Volcano Program BASE MAP NIMA and ESRI, Digital Chart of the World USGS, EROS Data Center DISCLAIMER Base map data, such as place names and political boundaries, are the best available but may not be current or may contain inaccuracies and therefore should not be regarded as having official significance. U.S. Department of the Interior U.S. Geological Survey General Interest Product xxx RELATIVE PLATE MOTIONS The relative motion of adjacent tectonic plates is depicted on the map by short vectors located at selected locations on the plate boundary. In this present- ation, one plate is assumed to be rigid and fixed. The vector therefore repre- sents the direction of the moving plate relative to the fixed plate. The rate of relative motion is labelled next to the vector. The components of the vector perpendic- ular and parallel to the plate margin approximate convergent/divergent and transverse direction of motion between the plates,respectively. As viewed from the rigid plate, an inward directed com- ponent suggests compression at and near the plate boundary that may be expressed as crustal folding, uplift, thrust faulting, or plate subduction. Similar- ly, an outward directed component sug- gests plate divergence such as would be expected at a zone of crustal spreading. Transcurrent or transform faulting would be expected when the predominant vector component is parallel to the plate margin. LARGEST EARTHQUAKES (M GE 7.5) 1900 - 2002 ALASKA AND VICINITY YR MO DY LAT LON DEPTH MAG 1900 10 9 57.090 -153.480 0 7.70 1917 5 31 54.500 -160.000 0 7.50 1929 3 7 50.786 -169.524 25 7.80 1938 11 10 55.328 -158.370 35 8.00 1946 4 1 52.750 -163.500 0 8.00 1949 8 22 53.750 -133.250 0 8.00 1957 3 9 51.556 -175.392 30 8.60 1958 7 10 58.370 -136.665 35 7.80 1964 3 28 61.017 -147.648 7 9.20 1972 7 30 56.696 -136.098 7 7.60 1979 2 28 60.656 -141.655 23 7.50 1986 5 7 51.557 -174.813 28 8.00 1987 11 30 58.836 -142.601 9 7.90 1988 3 6 57.262 -142.747 6 7.80 1996 6 10 51.593 -177.589 28 7.90 2002 11 3 63.520 -147.533 5 7.90 DISCUSSION (Continued) The Denali fault is a prominent topographic scar on the Alaskan landscape. Prior to the recent earthquake, the fault scarp between Denali National Park on the west and the Richardson Highway on the east appeared degraded, indicating that the last major earthquake was a few hundred years ago. In the epicentral area of the recent quake, USGS geologist George Plafker observed that the last major earthquake had 6-8 m of right- lateral offset. Slip rate on the Denali fault since the last glaciation (10,000 years before present) has averaged about 1 cm/year. Accordingly, a 6- m displacement would require 600 years of strain accumulation. This is the largest earthquake on the Denali fault since at least 1912, when a M 7.2 earthquake occurred in the general vicinity of the fault, more than 50 miles to the east of the 3 November epicenter. Since there were no seismographs operating in Alaska at that time and no reports of surface faulting in the remote Alaska Range, the location of the 1912 shock is not well-constrained. Fault rupture initiated about 25 km east of the M6.7 23 October foreshock and continued eastward and southeastward for about 300 km, crossing the Richardson and Glenn (Tok Cutoff) highways. Near Mentasta Lake the rupture branched from the Denali fault and continued for about 75 km along the Totschunda fault. This branching from the Denali to the Totschunda was expected based on earlier geologic fault investigations and is reflected in the USGS seismic hazard map of Alaska. The seismic radiation pattern determined by Harvard University seismologists is consistent with the observed right- lateral slip. Preliminary measurements of fault displacements in the field by geologists range from under a meter in some locations in the west to nearly 9 meters near Mentasta Lake. DISCUSSION This M7.9 shock, one of the largest ever recorded on U.S. soil, occurred on the Denali-Totschunda fault system, which is one of the longest strike- slip fault systems in the world and rivals in size California's famed San Andreas strike- slip fault system that spawned the destructive M7.8 "San Francisco" earthquake in 1906. Most of the seismic activity in Alaska results from interaction of the northwestward- moving Pacific plate with the corner of the North American plate that includes Alaska. Along the southeastern panhandle of Alaska, this motion is accommodated by right- lateral strike- slip faulting, but from Yakutat Bay westward along the southern coast of Alaska and the Aleutian Islands, the Pacific plate is colliding with Alaska. West of Kayak Island, this collision results in subduction of the Pacific plate beneath continental Alaska and the Aleutian Islands. This underthrusting motion was the cause of the M9.2 Alaska earthquake of 1964. Between Kayak Island and Yakutat Bay, the Pacific plate is mostly coupled to southern Alaska. This coupling has resulted in the rapid, geologically- recent building of the coastal St. Elias Mountains and produces northwest- southeast oriented compressive stress that extends inland through the Alaskan crust to Fairbanks and seaward into the Gulf of Alaska. This compressive stress drives the right- lateral slip witnessed on the Denali-Totschunda fault system. 150° 145° 140° 135° 150° 145° 140° 135° 60° 65° 60° 65° Anchorage Juneau Fairbanks G u l f o f A l a s k a Kodiak I. Cook Inlet 10 20 30 2 1 5 3 2 4 4 3 43 4 4 3 4 5 4 5 4 4 4 4 4 4 4 5 4 4 4 5 5 5 5 6 5 5 5 5 4 6 6 6 7 5 8 4 67 4 7 6 6 5 6 6 4 6 6 6 6 6 5 5 6 6 5 4 6 5 4 2 4 4 4 4 EXPLANATION 3 November 2002 ShakeMap Acceleration (%g) Major Faults Highways and Roads Populated Places Intensity (MMI) 0 100 200 300 400 50 Kilometers SCALE 1:10,000,000 Albers Equal-Area Projection ShakeMap Acceleration and Observed Intensity
Transcript of U.S. Department of the Interior Denali Park, Alaska ...
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Tolovana
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Matanuska
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Jack WadeBig Delta
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Kantishina
Kechumstuk South Fork
Richardson
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Port Ashton
Gilpatricks
Eagle River
Petersville Chistochina
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Denali Park
Moose Creek
Old Saulich
Alder CreekFlume Creek
Peters Creek
Tok Junction
Steele Creek
North Nenana
Cape Yakataga
Lower Tonsina
Copper Center
Tyone Village
Mentasta Lake
Eagle Village
Crooked Creek
Cooper Landing
Indian Village
Delta Junction
Tetlin Junction
Cathedral Rapids
Northway Junction
Upper Slate Creek
Hot Springs Landing
Denali Park, Alaska Earthquake of 3 November, 2002
EXPLANATION23 October 2002
Mw = 6.7
3 November 2002
Mw = 7.9
Aftershocks
23 Oct - 2 Nov 2002
3 - 15 Nov 2002
Quaternary Faults
23 October 2002
3 November 2002
No Rupture
Magnitude Classes
M < 1.0
1.0 - 2.0
2.0 - 3.0
3.0 - 4.0
4.0 - 5.0
5.0 - 6.0
Urbanized Areas
AnchoragePopulated Places
Tok Junction
Roads
Primary
Secondary
Unpaved
Connector
Railroads
Airports
Active Civil
Active Military
Other
Glacier
National Parks
Trans-Alaska Pipeline
0 20 40 60 8010
Kilometers
0 20 40 60 8010
Miles
SCALE 1:1,500,000Albers Equal-Area Projection
Map prepared by U.S. Geological SurveyNational Earthquake Information Center21 November 2002Map not approved for release by Director
3 November 2002 22:12:41.0 UTC63.520 N., 147.533 W.Depth 5 km (Geophysicist)Mw = 7.9 (USGS)
One person injured and extensive damage to roads. Items knockedfrom shelves in Denali National Park, Glenallen and Tok. Some supports on the trans-Alaska pipeline were damaged and operation was suspended. Damage estimated at 20 million U.S. dollars. Felt widely in northern British Columbia, western Alberta and Northwest Territories. Also felt by people in high-rise buildings in Seattle, Washington. Seiches and muddied water wells observed in a number of states, including Washington, Idaho, Louisiana, Oklahoma, Missouri, Wisconsin and Pennsylvania.
The faulting mechanism for the earthquake was complex, consistingof a sequence at least two sub-events. It appears that the first sub-event ruptured on a short thrust fault south of the main strand of theDenali Fault which subsequently ruptured with right- lateral strike- slip motion as the much larger second sub-event. Preliminary geologic observations indicate offsets as much as 9 m on the Denali Fault.
23 October 2002 11:27:19.3 UTC63.576 N., 148.088 W.Depth 14 km (Geophysicist)Mw = 6.7 (USGS)
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Fox Islands
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N O R T H
A M E R I C A N
P L A T E
P A C I F I C P L A T E
53 mm/yr
61 mm/yr
69 mm/yr
DETAILED MAP
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SCALE 1:15,000,000Albers Equal-Area Projection
0 100 200 300 40050
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SCALE 1:15,000,000Albers Equal-Area Projection
EXPLANATION3 November 2002
Mw = 7.9
Volcanoes
Plate Boundaries
Convergent
Divergent
Transform
Major Faults
Peak Ground Acceleration
0.0 - 0.2 m/sec**2
0.2 - 0.4
0.4 - 0.8
0.8 - 1.6
1.6 - 3.2
3.2 - 6.4
6.4 - 9.7
EXPLANATION3 November 2002
Mw = 7.9
Plate Boundaries
Convergent
Divergent
Transform
Major Faults
Volcanoes
Plate Tectonic Setting
Generalized Seismic Hazard
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U. S. A. DETAILED MAP
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Seismic History 1900 - 2002
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SCALE 1:15,000,000Albers Equal-Area Projection
EXPLANATION3 November 2002
Mw = 7.9
Depth Classes
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Depth > 70 km
Magnitude Classes
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Plate Boundaries
Convergent
Divergent
Transform
Major Faults
Volcanoes
Seismic hazard is expressedas peak ground acceleration(PGA) in meters/sec**2 ex-pected in a 50-yr period with a probability of 10 percent.
DATA SOURCES
EARTHQUAKES AND SEISMIC HAZARD USGS, National Earthquake Information Center Alaska Earthquake Information Center IASPEI, Centennial Catalog (1900 - 1999) Handbook of Seismology and Earthquake Engineering Global Seismic Hazard Assessment Program
FAULTS USGS, Anchorage and Denver
PLATE TECTONICS Smithsonian Institution, Global Volcano Program BASE MAP NIMA and ESRI, Digital Chart of the World USGS, EROS Data Center
DISCLAIMER
Base map data, such as place names and politicalboundaries, are the best available but may not be current or may contain inaccuracies and thereforeshould not be regarded as having official significance.
U.S. Department of the InteriorU.S. Geological Survey
General Interest Product xxx
RELATIVE PLATE MOTIONS
The relative motion of adjacent tectonicplates is depicted on the map by short vectors located at selected locationson the plate boundary. In this present-ation, one plate is assumed to be rigid and fixed. The vector therefore repre-sents the direction of the moving platerelative to the fixed plate. The rate of relative motion is labelled next tothe vector.
The components of the vector perpendic-ular and parallel to the plate margin approximate convergent/divergent and transverse direction of motion between the plates,respectively. As viewed from the rigid plate, an inward directed com-ponent suggests compression at and near the plate boundary that may be expressedas crustal folding, uplift, thrustfaulting, or plate subduction. Similar-ly, an outward directed component sug-gests plate divergence such as would be expected at a zone of crustal spreading.Transcurrent or transform faultingwould be expected when the predominantvector component is parallel to theplate margin.
LARGEST EARTHQUAKES (M GE 7.5) 1900 - 2002 ALASKA AND VICINITY
YR MO DY LAT LON DEPTH MAG
1900 10 9 57.090 -153.480 0 7.70 1917 5 31 54.500 -160.000 0 7.50 1929 3 7 50.786 -169.524 25 7.80 1938 11 10 55.328 -158.370 35 8.00 1946 4 1 52.750 -163.500 0 8.00 1949 8 22 53.750 -133.250 0 8.00 1957 3 9 51.556 -175.392 30 8.60 1958 7 10 58.370 -136.665 35 7.80 1964 3 28 61.017 -147.648 7 9.20 1972 7 30 56.696 -136.098 7 7.60 1979 2 28 60.656 -141.655 23 7.50 1986 5 7 51.557 -174.813 28 8.00 1987 11 30 58.836 -142.601 9 7.90 1988 3 6 57.262 -142.747 6 7.80 1996 6 10 51.593 -177.589 28 7.90 2002 11 3 63.520 -147.533 5 7.90
DISCUSSION (Continued)
The Denali fault is a prominent topographic scar on the Alaskan landscape. Prior to the recent earthquake, the fault scarp between Denali National Park on the west and the Richardson Highway on the east appeared degraded, indicating that the last major earthquakewas a few hundred years ago. In the epicentral area of the recent quake, USGS geologist George Plafker observed that the last majorearthquake had 6-8 m of right- lateral offset. Slip rate on the Denali fault since the last glaciation (10,000 years before present) has averaged about 1 cm/year. Accordingly, a 6- m displacement would require 600 years of strain accumulation.
This is the largest earthquake on the Denali fault since at least 1912, when a M 7.2 earthquake occurred in the general vicinity of the fault, more than 50 miles to the east of the 3 November epicenter.Since there were no seismographs operating in Alaska at that time and no reports of surface faulting in the remote Alaska Range, the location of the 1912 shock is not well-constrained. Fault rupture initiated about 25 km east of the M6.7 23 October foreshock and continued eastward and southeastward for about 300 km, crossing the Richardson and Glenn (Tok Cutoff) highways. Near Mentasta Lake the rupture branched from the Denali fault and continued for about 75 km along the Totschunda fault. This branching from the Denali to the Totschunda was expected based on earlier geologic fault investigations and is reflected in the USGS seismic hazard map of Alaska. The seismic radiation pattern determined by Harvard University seismologists is consistent with the observed right- lateral slip. Preliminary measurements of fault displacements in the field by geologists range from under a meter in some locations in the west to nearly 9 meters near Mentasta Lake.
DISCUSSION
This M7.9 shock, one of the largest ever recorded on U.S. soil, occurred on the Denali-Totschunda fault system, which is one of the longest strike- slip fault systems in the world and rivals in size California's famed San Andreas strike- slip fault system that spawned the destructive M7.8 "San Francisco" earthquake in 1906.
Most of the seismic activity in Alaska results from interaction of the northwestward- moving Pacific plate with the corner of the North American plate that includes Alaska. Along the southeastern panhandle of Alaska, this motion is accommodated by right- lateral strike- slip faulting, but from Yakutat Bay westward along the southerncoast of Alaska and the Aleutian Islands, the Pacific plate is colliding with Alaska. West of Kayak Island, this collision results in subductionof the Pacific plate beneath continental Alaska and the Aleutian Islands. This underthrusting motion was the cause of the M9.2 Alaska earthquake of 1964. Between Kayak Island and Yakutat Bay, the Pacific plate is mostly coupled to southern Alaska. This coupling has resulted in the rapid, geologically- recent building of the coastal St. Elias Mountains and produces northwest- southeast oriented compressive stress that extends inland through the Alaskan crust to Fairbanks and seaward into the Gulf of Alaska. This compressive stress drives the right- lateral slip witnessed on the Denali-Totschunda fault system.
150° 145° 140°
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Anchorage
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nlet
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4 4 34 54 5
444 444 45 4 4 4
5 555 655 554
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4
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66 6 65 5665 4 6
5 4
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4 4 4 EXPLANATION
3 November 2002
ShakeMap Acceleration (%g)
Major Faults
Highways and Roads
Populated Places
Intensity (MMI)
0 100 200 300 40050
Kilometers
SCALE 1:10,000,000Albers Equal-Area Projection
ShakeMap Acceleration and Observed Intensity
