Alaska-Aleutian Region for the Instrumental Period 1898 to 1982
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A SEISMOTECTONIC ANALYSIS OF THE SEISMIC AND VOLCANIC HAZARDS IN THE PRIBILOF ISLANDS - EASTERN ALEUTIAN ISLANDS REGION OF THE BERING SEA by Dr. Klaus H. Jacob and Dr. Egill Hauksson Lament-Doherty Geological Observatory Columbia University in the City of New York Final Report Outer Continental Shelf Environmental Assessment Program Research Unit 16 1983 135 TABLE OF CONTENTS List of Figures . ..0..... ...*. ...*.. ..*...*. 139 List of Tables . 145 Acknowledgments . ...0... ● . ...*... .* *.**... 147 1. ABSTRACT AND SUMMARY OF MOST IMPORTANT RESULTS . 148 2. INTRODUCTION .* ● . ● . ● . ● . ..**.**. ● ● . ● . ..* . ●. 150 3. DATA ANALYSIS . ● . ● . ● . ..**. ● . ● . ..*. 154 3.1 Seismicity Recorded by the Shumagin Network 1973-1982 . 154 3.2 Teleseismic Data 1973-1982 ..* . .* . 171 3.3 Strong-Motion Data . 177 3.4 Historic and Instrumental Large Earthquakes, 1788 to Present . 190 3.5 Historical Eruptive Activity of Pavlof, Akutan, and Makushin Volcanoes . 237 3.6 Geology and Geodetic Surveys . 247 3.7 Seismicity Recorded by the Unalaska Array 1980-1982 . 252 3.8 Tsunami Data . ● . ● ..* . ● . 256 4. RESULTS . , . ● . ., 259 4.1 Seismic Hazards . ● . , . 259 4.2 Volcanic Hazards . ..*..... ..*....* 264 5. CONCLUSIONS . ., ● . ● . ● ..O . , . 279 6. UNRESOLVED PROBLEMS . , . ● . , . 281 7. APPENDICES . .*.. ● . ● . 282 7.1 Earthquake Data Processing Methods ● . 282 7.2 Magnitude Determinations . ..*. ., . , . 291 7.3 Annual Plots of Shumagin Network Seismicity 1973-1982 . 300 7.4 Shumagin Network Status 1973-1982 . ● . 315 7.5 Seismic and Eruptive Activity of Pavlof Volcano, 1973-1982 . 325 7.6 Preliminary Risk Assessment in the St. George Basin . 335 7.7 List of Publications Supported by Contract NOAA-03-5-022-70 . 357 8. REFERENCES . ,. ● .* . ● . ● . ● , . ● . 359 137 LIST OF FIGURES Figure 2.1 - Approximate regions (boxes) in which L-DGO collected data by operating seismic stations or networks in St, Paul (SNP), Dutch Harbor (DUT.) on Unalaska Island, and in the Shumagin Islands with central recording at Sand Point (SAN) Figure 3.1.1 - Map of epicenters showing all the seismicity located by the Shumagin network eastern Aleutians, Alaska, from 1973-1981 Figure 3.1.2 - Map of epicenters showing all the shallow seismicity (depth less than 30 km) located by the Shumagin network, eastern Aleutians, Alaska, from 1973-1981 Figure 3.1.3 - Map of epicenters showing all the intermediate depth and very deep seismicity (depth greater than 40 km) located by the Shumagin network, eastern Aleutians, Alaska from 1973-1981 Figure 3.1.4 - Histogram of number of earthquakes located by the Shumagin seismic network, eastern Aleutians, Alaska Figure 3.1.5 - Cumulative number of all local earthquakes located by the Shumagin network from 1978 to 1982 Figure 3.1.6 - Both cumulative number and number of earthquakes as a function of magnitude for the whole data set recorded by the Shumagin network from 1977 to 1981 Figure 3.1.7 - Both cumulative number and number of earthquakes as a function of magnitude for all shallow earthquakes (depth less than 30 km) recordedby the Shumagin network from 1977 to 1981 Figure 3.1.8 - Map of epicenters where seismicity lineaments are em- phasized by drawing straight lines by eye trhough clusters that appear to form linear alignments Figure 3.1.9 - Cumulative number of seismicity lineaments from Figure 3.8 versus length of seismicity lineament Figure 3.1.10 - Magnitude versus source dimension relationship Figure 3.1.11 - Recurrence relation for the Gulf of Alaska random sources Figure 3.2.1 - Map of epicenters showing teleseismically located earth- quakes from the PDE bulletin from 1973-1981 Figure 3.2.2 - The vertical bars indicate the occurrence and the mag- nitude of teleseismically located earthquakes from the PDE bulletin 139 Figure 3.2.3 - Cumulative number of earthquakes located by the PDE from 1973 to 1982 in the Shumagin Islands region Figure 3.2.4 -. Both cumulative number and number of earthquakes as a function of magnitude for the PDE data from 1973 to 1981 located in the Shumagin Islands region Figure 3.3.1 - Comparison of peak horizontal accelerations for Alaska with empirical attenuation laws obtained by Joyner and Boore (1981) by regression of mostly western U.S. strong motion data Figure 3.3.2 - Comparison of Alaska peak horizontal accelerations with type-A attenuation relations proposed by Woodward-Clyde (1982) for shallow, non-Benioff zone earthquakes Figure 3.3.3 - Comparison of Alaska peak horizontal accelerations with B-type attenuation relations proposed by Woodward-Clyde (1982) for Benioff-zone earthquakes Figure 3.4.1 - Location map of presently existing seismic gaps and of rupture zones of the most recent sequence of major earthquakes since 1938 Figure 3.4.2 - Major earthquakes in the Alaska-Aleutian region for the instrumental period 1898 to 1982 Figure 3.4.3 - Seismicity of the Aleutian arc versus time for the instrumental period 1898 to 1982 Figure 3.4.4 - Histogram of all major earthquakes for which magni- tudes were available, plotted in ~ = O.1-intervals Figure 3.4.5 - Logarithmic frequency plots for the instrumental seismicity 1898 to 1982 for the Alaska-Aleutian arc Figure 3.4.6 - Same as Figure 3.4.5 with number of events ~ as solid line and cumulative number of events N as broken line Figure 3.4.7 - Arc-wide seismic moment release for the Aleutian arc during the period 1898 to 1982 Figure 3.4.8 - Space-time plot of instrumental (1898 to 1982) and historical (1788 to 1897) seismicity of the Aleutian arc considering great earthquakes only Figure 3.4.9 - Statistical properties of recurrence periods Figure 3.4.10 - Same as Figure 3.4.9 except that a normal (rather than a log-normal) distribution is fitted to observed recurrences times distribution which cons~kts of a reduced number of samples Figure 3.5.1 - The number of reported eruptions per decade vs. time 140 F5gure 3.6.1 - Maps showing level lines and tide gauges in the Shumagin Islands Figure 3.6.2 - Data from those level lines in the Shumagins that have been levelled at least twice Figure 3.7.1 - Dutch Harbor Array, Eastern Aleutians, operated by Lament-Doherty Geological Observatory Figure 3.7.2 - Number of earthquakes recorded per day by the Dutch Harbor Array in 1980 and 1981 Figure 3.7.3 - Number of earthquakes recorded per day by the Dutch Harbor Array in 1982 Figure 3.8.1 - Diagram showing tsunami run-up heights and inferred earthquake source region of the 1788 event(s) Figure 4.1.1 - Map view of arc with instrumental seismicity since 1898 Figure 4.2.1 - Volcano hazards map for the Western Alaska Peninsula Figure 4.2.2 - Volcano hazards map for the Eastern Aleutian Islands Figure 4.2.3 - Distribution of volcanic ash layers in North Pacific deep-sea cores Fipures 4.2.4a,b - Sample locality maps in Shumagin Islands and adjacent peninsula Figures 4.2.5a,b - Examples of volcanic ash layers in cores taken on marine terraces in summer 1979 Figure 4.2.6 - Log10 of the cumulative number of eruptions of a given size per hundred years per volcano vs. the loglo of the volume of eruptive products Figure 4.2.7 - Maximum ash thickness in cm vs. distance from the vent Figure 7.1.1 - A block diagram showing how the routine develocorder data processing was carried out for the Shumagin seismic network Figure 7.1.2 - A block diagram showing how the routine digital data processing is carried out for the Shumagin seismic network Figure 7.1.3 - A summary display of seismic traces from the program ping Figure 7.1.4 - A sample seismogram from station CNBZ Figure 7.1.5 - A sample output from HYPOINVERSE 141 Figure 7.1.6 - A sample output from the program dplt2 Figure 7.2.1 - Sensor responses and recorder responses shown as a function of frequency for seismic stations in the Shumagin network Figure 7.2.2 - Magnification curves for a typical high gain short- period station (NGI at 48 db Amp/VCCl gain) Figure 7.2.3 - Comparison between magnitude values determined by the Shumagin network and values publishedby NEIS —Figure 7.3.1 - Seismicity located by the Shumagin network during 1973 Figure 7.3.2 - Seismicity located by the Shumagin network during 1974 Figure 7.3.3 - Seismicity located by the Shumagin network during 1975 Figure 7.3.4 - Seismicity located by the Shumagin network during 1976 Figure 7.3.5 - Seismicity located by the Shumagin network during 1977 Figure 7.3.6 - Seismicity located by the Shumagin network during 1978 Figure 7.3.7 - Seismicity located by the Shumagin network during 1979 Figure 7.3.8 - Seismicity located by the Shumagin network during 1980 Figure 7.3.9_ - Seismicity located by the Shumagin network during 1981 Figure 7.3.10 - Seismicity located by the Shumagin network from January-June 1982 Figure 7.3.11 - Seismicity located by the Shumagin network from 1973-1981 Figure 7.4.1 - The Shumagin seismic networks Alaska Figure 7.4.2 - Operational status of the Shumagin network in 1973 and 1974 Figure 7.4.3 - Operational status of the Shumagin network in 1975 and 1976 Figure 7.4.4 - Operational status of the Shumagin network in 1977 and 1978 Figure 7.4.5 - Operational status of the”Shumagin network in 1979 and 1980 Figure 7.4.6 - Operational status of the Shumagin network in 1981 and 1982 142 Figure 7.5.1 - Map showing stations of the Pavlof seismic array Figure 7.5.2 - Types of seismic signals recorded on helicorder from station PVV Figure 7.5.3 - Number of B-type earthquakes and explosions per day Figure 7.5.4 - Number of B-type earthquakes and explosions per day . Figure 7.5.5 - Number of B-type earthquakes and explosions per day Figure 7.5.6 - Number of B-type earthquakes and explosions per day Figure 7.5.7 - Number of B-type earthquakes and explosions per day Figure 7.6.1 - Earthquake, epicenters, greater St.