Effects of the Earthquake of March 27,1964 in the Copper River Basin Area, Alaska

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Effects of the Earthquake of March 27,1964 in the Copper River Basin Area, Alaska STOLEN FROm RrnARD D. REGUl THE ALASKA EARTHQUAKE, MARCH 27, 1964: REGIONAL EFFECTS Effects of the Earthquake Of March 27,1964 In the Copper River Basin Area, Alaska By OSCAR J. FERRIANS, JR. A description and analysis of the earthquake- induced ground breakage, landsliding, regionul uplift and subsidence, and damage to manmade str2cctures in the Copper River Basin GEOLOGICAL SURVEY PROFESSIONAL PAPER 543-E UNITED STATES DEPARTMENT OF THE INTERIOR STEWART L. UDALL, Secretary GEOLOGICAL SURVEY , William T. Pecora, Director UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1966 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 ALASKA EARTHQUAKE SERIES The U.S. Geological Survey is publishing the re- sults of its investigation~of the Alaska earthquake of March 27, 1964, in a series of six professional papers. Professional Paper 543 describes the re- gional effects of the earthquake. In chapters of this volume already published, studies of slide-induced waves and seiching at Kenai Lake, geomorphic ef- fects in the Martin-Bering Rivers area, gravity sur- veys of the Prince William Sound region, and effects of the earthquake on Kodiak and nearby islands have been reported. Other professional papers in the series describe field investigations and reconstrvction and the effects of the earthquake on communities, on the hydrologic regimen, and on transportation, utilities, and communications. CONTENTS Psge Page Page Abstract - - - - - - - - - - - _-_ - - - - - - - - - El Geologic effects of the earth- Geologic effects-Continued Introduction and acknowledg- quake---------------------- E8 Ground cracks and associated men&- - - - - - - - - - - - - - - - - - - - - - 2 Regional uplift and sub- landsliding-Continued Geographic setting.. - _ - - - - - - - - - 2 sidence- - - - - - - - - - - - - - - - - 8 Nelchina River delta- - - El7 Physiography- - - - - - - - - - - - - 2 Changes in ground- and Origin - - _ - - - - - - - - - - - - 23 Climate- - - - - - - - - - - - - - - - - - 3 surface-water conditions- - 8 Lateral extension.. - 23 Roads and settlements- - - - - 3 Ground water--- - - - - - - 8 Horizontal com- Geologic setting-- ----- --- --- - - 3 Surface water--------- 8 paction- - - - - - - - 23 Bedrock------------------ 3 Cracking of lake and river ice_- 10 Differential verti- Major tectonic elements--- - 3 Ground cracks and associ- cal compaction- - 24 Unconsolidated deposits-- - - 6 ated landsliding--- -- - -- - 11 Snowslides, rockslides, and 24 Permafrost and seasonal Terminology-- - - - - - - - - 11 avalanches - - - - - - - - - - - - - Effects of the earthquake on - - 11 frost----------- --- --- -- 6 General distribution- manmade structures- -- - - - - - - 25 The earthquake and its after- Geologic controls- - - - - - 11 Damage to buildings and shocks--------------------- 6 Little Tonsina River site-- 13 associated structures-- - - - 25 Seismic data-------------- 6 Other landslide sites.. .- 13 Damage to highways and Ground motion- _ - - --- - --- 7 Nelchina River outwash bridges- - - _ - - - - - - - - - - - - - 25 Sound------------------- 7 apron-------------- 17 References--- - - - - - - - - - - - - - - - - - 27 ILLUSTRATIONS FIGURES Psge Page Page 1. Index map showing the loca- floor of Little Tonsina 17. Aerial view of north end of tion of the Copper River River valley - - - - - - - - - - - - El4 the large Nelchiia River Basin area -------------- E2 10. Large ground crack parallel- delta along the western 2. Generalized geologic map of ing north side of small hill shore of Tazlina Lake- - - - E2 1 the Copper River Basin near mile 65, Richardson 18. Aerial view of Kiana Creek area-------------------- - - - 4 Highway - - - - - - - - - - - - 15 delta along eastern shore of 3. Map showing major tectonic 11. Photograph of pressure ridge Tazlina Lake 2 1 elements of south-central on flat surface bordering Alaska- - - - - - - - - - - - - - - - - 5 Little Tonsina River- _ _ - - 15 19. Aerial view showing large in- 4. Map showing recent regional 12. Large ground crack formed undated area along eastern uplift and subsidence in in clearing along south shore of Tazlina Lake-- -- 22 south-central Alaska- - - _ _ 9 shore of lake _-_-----___- 16 20. Diagrammatic sections show- 5. Aerial view of the northern 13. Aerial view of the large ing mechanism of forma- end of Tonsina Lake- - - _ 10 braided flood plain of the tion of basic types of 6. Aerial view showing intensely Nelchina River ---------_ 17 ground cracks ----------- 23 fractured ice along the 14. Photograph of typical ground 21. View of pavement surface of eastern shore of Tazlina crack in outwash apron of the Richardson Highway - - 26 Nelchina River -------___ 18 Lake------------------- 11 15. Vertical aerial view of Nel- 22. Little Tonsina River bridge 7. Map showing the distribution china River delta ------__ 19 shoved from right to left 26 of ground cracks --------- 12 16. Vertical aerial view of ground by landslide movement-- - 8. Sketch map of the Little cracks along and parallel- 23. Small crack across aban- Tonsina River landslide site-- 14 ing hingeline on Nelchina doned section of road on a 9. View of pressure ridges on River delta-- ----------- 20 low gravel terrace--- - - - - - 27 v THE ALASKA EARTHQUAKE, MARCH 27,1964: REGIONAL EFFECTS EFFECTS OF THE EARTHQUAKE OF MARCH 27, 1964, IN THE COPPER RIVER BASIN AREA, ALASKA By Oscar J. Ferrians, Jr. ABSTRACT The Copper River Basin area is in Copper River was completely dammed March, seasonal frost was present south-central Alaska and covers 17,800 and Tazlina Lake drained proved erro- throughout the area. square miles. It includes most of the neous. Despite the diversity of local condi- Copper River Basin and parts of the The ice on most lakes was cracked, tions, the origin of most of the ground surrounding Alaska Range and the Tal- especially around the margins of the cracks can be explained by the following keetna, Chugach, and Wrangell Moun- lakes where floating ice broke free from mechanisms : (1) lateral extension, tains. the ice frozen to the shore. Ice on Taz- caused by materials moving toward an On March 27,1964, shortly after 5 : 36 lina, Klutina, and Tonsina Lakes was unconfined face such as a lakeshore, p.m. A1as;ka standard time, a great intensely fractured by waves generated river bluff, hillside, or terrace escarp- earthquake having a Richter magnitude by sublacustrine landslides off the ment ; (2) horizontal compaction, of about 8.5 struck south-central Alaska. fronts of deltas. These waves stranded caused by repeated alternate compres- Computations by the U.S. Coast and large blocks of ice above water level sion and dilation (in the horizontal Geodetic Survey place the epicenter of along the shores. River ice was gen- direction) of materials in flat-lying the main shock at lat 61.1" N. and long erally cracked in the southern half of areas where there are no unconfined 147.7" W., and the hypocenter, or actual the area and was locally cracked in the faces ; (3) differential vertical compac- point of origin, from 20 to 50 kilometers northern half. tion, caused by the shaking of materials below the surface. The epicenter is In the area of study, the majority of that vary laterally in thickness or near the western shore of Unakwik In- the ground cracks occumed within a ra- character ; and (4) combinations of the let in northern Prince William Sound; dius of 100 miles from the epicenter of above. it is 30 miles from the closest point the earthquake. Ground cracks formed Snowslides, avalanches, and rock- within the area of study and 180 miles in flood plains of rivers, in deltas, and slides were restricted to the moun- from the farthest point. along the toes of alluvial fans. They tainous areas surrounding the Copper Releveling data obtained in 1964 after also occurred locally in low terraces River Basin. They were especially the earthquake indicates that broad adjacent to flood plains, in highway numerous in the Chugach Mountains areas of south-central Alaska were and other fill material, along the mar- which are closest to the epicenter of the warped by uplift and subsidence. The gins of lakes, along the faces of steep earthquake. The large amount of snow configuration of these areas generally slopes of river bluffs and hillsides, and and rock debris that has cascaded onto parallels the trend of the major tectonic in areas cleared of vegetation for sev- the icefield and glaciers of these moun- elements of the region. Presumably a large part of this change took place dur- eral years. tains, and, probably even more impor- ing and immediately after the 1964 The ground cracks were restricted to tant, the overall disturbance to the ice earthquake. areas underlain by unconsolidated de- field will affect the regimen of the The water level in several wells in the posits where one or more of the follow- glaciers. area lowered appreciably, and the wa- ing conditions existed : (1) permafrost Most of the damage to inanmade ter in many became turbid; geneally, was absent or deep lying, (2) the structures occurred in the southern however, within a few days after the ground-water table was near the sur- half of the area, and, primarily because earthquake the water level returned to face, (3) bedrdck was relatively deep of the sparsity of population and man- normal and the suspended sediment set- lying, and (4) slopes were steep. Be- made structures, property damage was tled out. Newspaper reportg that the cause the earthquake occurred in not great and no lives were lost. El
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