Catalog of Intensities and Magnitudes for Earthquakes in Alaska and the Aleutian lslands-I 786-1 981 By STANLEY R. BROCKMAN, A. F. ESPINOSA, and JOHNA. MICHAEL U.S. GEOLOGICAL SURVEY BULLETIN 1840 DEPARTMENT OF THE INTERIOR DONALD PAUL HODEL, Secretary U. S. GEOLOGICAL SURVEY Dallas L. Peck, Director UNITED STATES GOVERNMENT PRINTING OFFICE: 1988 For sale by the Books and Open-File Reports Section U.S. Geological Survey Federal Center Box 25425 Denver, CO 80225 Library of Congress Cataloging-in-Publication Data Brockman, Stanley R. Catalog of intensities and magnitudes for earthquakes in Alaska and the Aleutian Islands, 1786-1981. (U.S. Geological Survey bulletin ; 1840) Bibliography: p. Supt. of Docs. no.: 1 19.3:1840 1. Earthquake intensity-Alaska. 2. Earthquake intensity- Alaska-Aleutian Islands. I. Espinosa, A. F. II. Michael, J. A. Ill. Title. IV. Series. QE75.69 no. 1840 557.3 s [551.2'2'09798] 88400069 [QE539.2.15] CONTENTS Glossary v Abstract 1 Introduction 1 Acknowledgments 1 Intensity scale and its usage 2 Description and characteristics of the catalog 2 Magnitudes 3 Conventions used 5 Identification of anomalous intensities 6 Studies on some significant earthquakes in Alaska 6 References cited 7 Supplemental references 8 Appendix-Modified Mercalli Intensity Scale of 1931 9 FIGURES 1-5. Maps of Alaska and vicinity showing: 1. Selected geographic features viii 2. Major tectonic features 2 3. Earthquakes from 1-1983 with calculated magnitudes of 4.5 or greater 3 4. Earthquakes from 1899-1981 with maximum intensity of VI or VII 4 5. Earthquakes from 1899-1981 with maximum intensity of VIII or greater 5 TABLES 1. Earthquakes listed chronologically with their source parameters and corresponding reported intensity information 13 2. Earthquakes from table 1 grouped according to their maximum Modified Mercalli Intensity rating 121 3. Earthquakes from table 1 that have one or more published magnitude and their maximum intensities 161 Table of Contents iii GLOSSARY [nade and company names are used for descriptive purposes only and do not imply endorsement by the U.S. Geological Survey] aftershock. Secondary earthquake that follows the main shock. CIRES. Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado. epicenter. Point on the Earth's surface vertically above the hypocenter of an earthquake. epicentral distance (A). Distance from the epicenter to the reporting location. event. Defined as an earthquake in the context of this publication. HDF (Hypocentral Data Files). Seismological data base maintained by the U.S. Geological Survey. hypocenter. Point of origin of an earthquake at which rupture begins and from which seismic waves originate. Io. Maximum intensity rating assigned to a given earthquake. intensity. Degree of shaking at a specific place resulting from an earthquake (see Modified Mercalli Intensity Scale in appendix). isoseismals. Contours that enclose areas of equal intensity. locality. A place or location that has past or present cultural associations. lithosphere. The outer, rigid shell of Earth containing the crust and plates (Press and Siever, 1986). macroseismic effects. Effects that can be observed on the large scale, in the field, without instrumental aid (Richter, 1958). magnitude. A quantity characteristic of the total energy released by an earth- quake. Richter (1958) devised the logarithmic magnitude scale known as the local magnitude (ML), which is in terms of the motion that would be measured by a standard type of seismograph located 100 km from the epicenter of an earthquake. The following magnitude types are used in this catalog: body wave (mb). Magnitude determined from body-wave amplitudes. coda length (M,) . Magnitude determined from overall length of the recorded wavetrain. local (ML).Magnitude determined from amplitudes recorded on a Wood- Anderson seismograph at near distances. surface wave (M,). Magnitude determined from amplitudes of 20-second- period surface waves at teleseismic distance. unified (m). A body-wave magnitude, as described by Richter (1958, p. 348-349). Glossary v magnitude source code. Codes that represent (1) the agency, (2) a seismograph station or (3) the catalog source (in italic) of a particular magnitude used in table 3. ADK. Adak, Alaska. AN1. Abe and Noguchi, 1983a. AN2. Abe and Noguchi, 1983b. BD. Bath and Duda, 1979. BG. Gutenberg, 1956. BRK. Berkeley, California. CFR. Richter, 1958. CGS. U.S. Coast and ~eodeticSurvey; PDE from January 1928-October 1970. COL. Fairbanks, Alaska. CUC. Boulder, Colorado (CIRES). EPB. Earth Physics Branch, Seismological Services of Canada, Ottawa, Ontario, Canada. A series of annual publications, 1960-1979, by various authors. ERL. Environmental Research Laboratories of NOAA; PDE from July 1971 through August 1973. GIA. University of Alaska, Geophysical Institute, Fairbanks, Alaska. G OL. Golden (Bergen Park), Colorado. GR. Gutenberg and Richter, 1954. GS. U.S. Geological Survey; PDE from August 1973 through the present (1988). GSM. U.S. Geological Survey, Menlo Park, California. ISC. International Seismological Center, Berkshire, England. KA1. Abe, 1981. KA2. Abe, 1984. NOS. National Ocean Survey of NOAA; PDE from October 1970 through June 1971. PAL. Palisades, New York. PAS. Pasadena, California. PMR. Palmer, Alaska. PRU. Pruhonice, Czechoslovakia. SJD. Duda, 1965. SSR. Kondorskaya and Shebalin, 1982. UPP. Uppsala, Sweden. vi U.S. Geological Survey Bulletin 1840 main shock. Largest of a series of earthquakes. m. Unified magnitude. mb. Body-wave magnitude. Mc. Coda-length magnitude. ML. Local magnitude. Ms. Surface-wave magnitude. Modified Mercalli Intensity Scale. Numerical subjective index of an earth- quake's effect on man, on structures, and on the Earth's surface. Ratings range from I to XI1 and are defined in the appendix. NOAA. National Oceanic and Atmospheric Administration. PDE (Preliminary Determination of Epicenters). Ongoing program, presently operated by the U.S. Geological Survey, designed to quickly determine and disseminate reasonably reliable estimates of earthquake loca- tions and magnitudes. plate. One of the dozen or more segments of the lithosphere that are internally rigid and move independently over the interior, meeting in convergence zones and separating at divergence zones (Press and Siever, 1986). seismicity. Spatial distribution of earthquakes; a general term for the number of earthquakes in a unit of time. seismograph. Instrument that detects, magnifies, and records vibrations of the Earth, especially earthquakes. subduction zone. Zone along which one plate descends beneath another plate; defined by high seismicity. teleseismic distance. An epicentral distance greater than 1,000 km from the recording station. USE (United States Earthquakes). Annual periodical published since 1928 by the agency responsible for the PDE program. Glossary vii Figure 1. Selected geographic features and localities in Alaska and vicinity. viii U.S. Geological Survey Bulletin 1840 Catalog of Intensities and Magnitudes for Earthquakes in Alaska and the Aleutian Islands- I 786-1 981 By Stanley R. Brockman, A.F. Espinosa, and John A. Michael Abstract Alaska intensities and magnitudes-tables 1, 2, and 3 An earthquake intensity catalog of the State of Alaska and at the end of this report. A computer-readable data the Aleutian Islands has been compiled and is presented in three base of intensities for the Alaska region, obtained from tables: (1) 3,145 earthquakes and their intensity information the National Oceanic and Atmospheric Administra- listed chronologically, (2) the earthquakes sorted by maximum intensity, and (3) earthquakes in table 1 that have one or more tion's Earthquake Data Service, served as the primary magnitude determinations, listed chronologically. The maximum source. Epicenters, magnitudes, and intensities from intensities range from I to XI (Modified Mercalli Intensity Scale), other sources (most are listed in "References Citedn, whereas magnitudes range from 3.6 to 8.7. Epicentral coordi- others in 'Supplemental Referencesn) were merged with nates are given for about half the earthquakes listed in table 1. the primary-source data to create a more complete cat- alog. Conflicts between sources were resolved whenever INTRODUCTION possible by referring to earlier source reports. Unre- solved differences were settled by giving preference to Alaska (fig. I), is one of the most seismically ac- data originated by the agencies responsible for the PDE tive States in the United States and has had numerous program. Much of the supplemental data (earthquake earthquakes, some of which caused widespread damage. origin time, location, magnitude, and depth) were ex- Seismicity of Alaska and the Aleutian Islands is high as tracted from the Hypocentral Data Files (HDF), which a result of complicated tectonic processes in the region. are compiled and maintained by the National Earth- Subduction of the Pacific plate under the North Ameri- quake Information Center of the U.S. Geological Sur- can plate (fig. 2) creates an area of near-constant seismic vey. activity. Seismicity in this region has been summarized The objectives in merging these data were to fill by Espinosa (1984) in a series of maps for different mag- the gaps in the primary-source data base; assure that nitude and depth ranges during 1960-1983. Instrumen- the resulting catalog is as consistent as possible with re- tal locations of earthquakes that had magnitudes of 4.5 gard to sources of earthquake parameters (origin