Electronic Supplement to
Seismicity Map of Eastern Russia, 1960-2010
by K. G. Mackey, K. Fujita, H. E. Hartse, R. J. Stead, L. K. Steck, L. V. Gunbina, N. Leyshuk, S. V. Shibaev, B. M. Koz'min, V. S. Imaev, E. I. Gordeev, V. N. Chebrov, O. K. Masal'ski, N. A. Gileva, V. A. Bormatov, A. A. Voitenok, Y. N. Levin, and T. A. Fokina
Introduction
This supplement contains detailed information on sources used in compiling the Eastern Russia Seismicity Database (ERSD), a comparison of the database and events listed in the International Seismological Centre Bulletin, information on event epicenter selection and magnitude calculation, and estimates on the completeness of the ERSD.
High Resolution Version of the Seismicity Map
Download/View: Seismicity Map of Eastern Russia, 1960-2010 [PDF; ~4.4 MB].
Database Sources
Numerous Russian and international data sources have been utilized to obtain both epicentral and phase data for the ERSD and the associated seismicity catalog. Below we list these sources and short descriptions of their contents:
Zemletryseniya v SSSR (1963-1991; Earthquakes of the USSR) and its successor publications Zemletryseniya Severnoi Evrazii (1992-2002; Earthquakes of Northern Eurasia), and Zemletryseniya Rossii (2003-2007; Earthquakes of Russia). This annual publication series contains a yearly catalog listing event parameters for the larger earthquakes that occurred within each regional network. In general, only events of K-class (see discussion below) 8.5 (Mb ~ 3) and larger are listed, although this has varied from year to year, and from network to network. In addition, the cutoff level was often raised for large aftershock sequences. Earthquakes of the USSR was generally available in the U.S., and pre-1989 events were included in the Global Hypocenter Data Base CD issued by the US Geological Survey (Reagor 1994).
Materialy po Seismichnosti Sibiri (Irkutsk, 1970-1993; Materials on the Seismicity of Siberia; hereafter Seismicity of Siberia). This was a bi-monthly publication containing both epicenter lists and phase data for each of the seismograph networks in Siberia that investigate seismicity of continental regions (Baikal, Magadan, Yakut, Amur (1979-1993), and Altai-Sayan networks). The epicenter list provided is generally complete, although isolated events found in the Far East Bulletin and in unpublished network data are missing. This publication was distributed primarily to the seismograph networks in Siberia.
Seismologichesky Byulleten' - Dal'nego Vostoka (Yuzhno Sakhalinsk, 1972-1990; Seismological Bulletin - Far East; hereafter Far East Bulletin). This quarterly bulletin is similar in format to Seismicity of Siberia, and also contains both epicenter lists and phase data. The Far East Bulletin covers the Magadan (listed as separate networks of "Northeast" and "Chukotka"), Amur, Sakhalin, Kamchatka, and Kuril networks. The epicenter list provided here is generally complete for Magadan and Amur, although isolated events found in the unpublished network data again are missing. For the Kamchatka network, only events of K-class larger than 9.0 (mb ~ 3.4) are listed. The Far East Bulletin was also issued with limited distribution. Phase data reported to the International Seismological Center (ISC) since the late 1990s is in the format of the Far East Bulletin.
Unpublished Magadan Network Bulletins (1977-early 2010). The epicenter lists and phase data for located events are similar in content and format to those found in the Far East Bulletin. The unpublished bulletins contain much additional material on explosions, unlocated events, and events from the surrounding networks. We supplemented phase data from many of the events listed here as unlocatable with data from other networks and located them for this map. Also included in our compilation are data from the unpublished Bulletin of the Aftershocks of the Artyk Earthquake of May 18, 1971, for Magadan network stations.
Unpublished Yakut Network Draft Material. Unpublished data from the Yakut network has been incorporated in varying degrees of completeness (nearly complete for 1982-early 2010). The material includes epicenters and phase picks from all earthquakes within the Yakut network. Also included are epicenters and phase arrival times for some events that occurred in adjacent networks. As with the Magadan data, we located additional events for this map. In addition, data for the aftershock sequences of the 1971 Artyk and the 1989 South Yakutia Earthquake were obtained for the temporary stations operated by the Yakut network.
Unpublished Kamchatka seismicity catalog. The unpublished Kamchatka seismicity catalog contains relocated coordinates for all Kamchatka events from 1960-early 2010. Individually, this catalog represents the largest fraction of events plotted on the seismicity map.
Unpublished Baikal, Sakhalin and Amur seismicity catalogs. These unpublished catalogs were primarily utilized to cover the time period from 1990 to 2010, following the cessation of publication of Seismicity of Siberia and the Far East Bulletin and contain similar levels of epicenter data.
Unpublished Khabarovsk seismicity catalog. This catalog is a partially complete seismicity catalog that was primarily derived from the Far East Bulletin. Events from the Amur, Sakhalin, and Kurile networks, as well as a small number of Chinese derived hypocenters for 1960-2004, were incorporated into the ERSD.
Other Russian sources that are incorporated into the database are the results of the Magadan district temporary deployment ("test network") of 1962-1963 (Andreev et al. 1967), data from the New Siberian Islands region obtained from temporary deployments in 1972-1976 and 1985-1988 (Avetisov 1996), epicenter data from ocean bottom seismometer deployments in the southern Laptev Sea (Kovachev et al. 1995), and the eastern Russia sections (especially for Chukotka) of the USSR national compilation by Kondorskaya and Shebalin (1977, 1982). Information on some mining and industrial explosions was also obtained from Godzikovskaya (1995).
Seismograms. Supplemental arrival times that were hand-picked from seismograms in the Yakut and Magadan networks, as well as develocorder film in Alaska, for various specific studies conducted at MSU were merged with arrivals from the above catalogs, where relevant, to obtain improved locations.
Teleseismic data for 1960-2007 were obtained from the on-line International Seismological Centre Bulletin (see also comments below), and the Preliminary Determination of Epicenters (U. S. Geological Survey).
Historical data (pre-1960) were compiled from Kondorskaya and Shebalin (1977, 1982), Gutenberg and Richter (1954), Savarensky et al. (1962a, b), Medvedev (1976), Rothé (1969), and the International Seismological Summary.
Finally, local data for Seward Peninsula, Bering Strait, and far eastern Chukotka events were compiled from the Alaska Earthquake Information Center and Biswas et al. (1983).
Due to the size of the data set, there are undoubtedly errors that have arisen in converting printed or hand-written data (both phase and epicenter) to digital form, as well as errors in the original data. In addition, there were numerous conflicts in determining event magnitudes and other parameters.
Regional Data Contributed to the ISC Bulletin
The International Seismological Centre (ISC) Bulletin includes some of the larger events located by the regional seismograph networks in eastern Russia in their database. Data from the Kamchatka, Sakhalin, and Kuril networks began to be reported in 1995-1996, and from Baikal and Magadan starting in 2003 and 2005, respectively. No Yakut network data have been listed by the ISC. Table T1 compares events listed by the ISC from four Russian networks to those in our merged database. From ISC records (through the end of 2006) we determined the total number of events, the time range, the geographic range, and the K-class range for records directly contributed by the Baikal, Kamchatka, Magadan, and Sakhalin networks. The last 2 columns of Table T1 list the numbers of events and the K-class ranges held in our merged database for the same time intervals and geographic windows as data obtained from the ISC. For each network, over the indicated time interval, our database includes about 2.5 to 8 times more events than are listed by the ISC. Further, the minimum event size in our merged bulletin is between 2.5 and 5.5 K-class units smaller than the events reported by the ISC.
Table T1. Comparison between ISC-reported events and events held in the ERSD. Statistics for the ERSD cover the same time interval as the contributed data in ISC.
| Area Covered | Contributed Data in ISC | ERSC | ||||||
|---|---|---|---|---|---|---|---|---|
| Network | Latitude Range | Longitude Range | ISC Start Date | Period Ending | No. Events Reported | K Class Range | No. Events Reported | K Class Range |
| Baikal | 47.79-57.49 | 96.86-121.88 | 20030105 | 20060227 | 654 | 9.5-14.3 | 1496 | 5.7-14.6 |
| Kamchatka | 46.11-61.57 | 149.88-173.75 | 19950901 | 20061231 | 7667 | 8.5-15.7 | 53207 | 3.5-15.9 |
| Magadan | 58.37-70.20 | 137.85-162.86 | 20050102 | 20061215 | 86 | 8.5-13.0 | 702 | 3.0-12.9 |
| Sakhalin (including Amur and Kuriles) | 41.63-56.28 | 121.96-159.13 | 19960402 | 20061230 | 2829 | 6.0-16.1 | 13268 | 3.6-16.4 |
Event Epicenters and Magnitudes
Approximately 100,000 events in our catalog have multiple, differing parameters as a result of the same event appearing in multiple sources. Preference was given to hypocenters that have been relocated using the local crustal velocity model derived by Mackey et al. (2003b) and utilizing an expanded phase arrival data set that combines multiple regional networks and teleseismic arrivals. These relocations significantly improved locations due to the increase in phase associations and the use of both Pg and Sg phases. Events that were previously not located due to lack of data were located if an increased number of phase associations became available when network catalogs were merged. Details on the relocation process and their inferred improvement of epicentral parameters can be found in Mackey (1999), Mackey and Fujita (2000), and Mackey et al. (2003b). These relocated events comprise most of the largest events in the Yakut, Magadan, and Amur network regions. Local or regional network hypocenter parameters were then preferred over teleseismic sources for smaller events as the local stations better constrain the event locations, primarily through the use of both Pg and Sg phases.
Event magnitudes for the largest events are based on teleseismically derived mb values. However, for the vast majority of events, event size was originally only reported in the Russian "K-class" system, which is based on the logarithm (base 10) of energy release in Ergs (Rautian et al. 2007). Different Siberian networks estimated K-class using slightly different formulas and practices. Hence, prior to making this map, we converted K-class to magnitude based on event location and network-specific regression formulas derived in Rautian et al. (2007; Table T2). The largest events are plotted on top of smaller ones on the map. If no K-class or magnitude estimate was available, the event was plotted at the smallest size.
Table T2. K-class (K) to ISC Magnitude (mb) Conversion (Adapted from Rautian et al. 2007)
| Network | Regression |
|---|---|
| Kamchatka | mb=(K-2.93)/1.81 |
| Yakut | mb=(K-1.15)/2.34 |
| Baikal | mb=(K-1.96)/2.30 |
| Amur | mb=(K-1.28)/2.54 |
| Magadan (inc. Chukotka) | mb=(K-2.02)/2.25 |
| Sakhalin | mb=(K-3.16)/1.49 |
| Kuril | mb=(K-0.30)/2.17 |
Completeness
The ERSD varies in the degree of completeness depending on seismograph network and time period. To determine the approximate completeness threshold, we plotted magnitude versus frequency relations for the various networks and time periods for 1970 to 2010; few regional stations operated in the 1960s. During this forty year period, there were great variations in the number and distribution of stations operated. Immediately following the collapse of the Soviet Union, many stations were closed and only reactivated or redeployed towards the end of the 1990s. The ERDS database is also not as complete in some areas, in particular the Kuril Islands, as in most of the continental part of eastern Russia.
There is also the possibility of additional explosion contamination, especially in seismically active areas where our time-of-day discriminant (Mackey et al. 2003a) would not be as effective. This would, however, generally be restricted to events of magnitude less than 3.
Based on an analysis of magnitude frequency relationships, the completeness threshold is around 2.6-3.0 for the continental networks (Amur, Baikal, Yakut, Magadan, with some variation and general improvement with time (Figure S1). Kamchatka is generally around magnitude 3.5, with a dramatic increase in the number of smaller events located in the decade of the 2000s as volcano monitoring networks went online (Figure S2). Sakhalin generally is around magnitude 3.5, while the Kuriles, with a lower density of stations except in the far southern part, are around 5-5.5.
Figure S1. Frequency-Magnitude relationship for the Kamchatka network catalog (2000-2009) in the ERSD. This plot indicates an overall network completeness threshold of about magnitude 3.0. The peak centered at about magnitude 1.0 is due to smaller events recorded by local volcano monitoring networks.
Figure S2. Frequency-Magnitude relationship for the Yakutsk network catalog (2000-2009) in the ERSD. This plot indicates an overall network completeness threshold of about magnitude 2.5.
It should be noted that these values are only indicative for areas within the network boundaries for which there is good station coverage - events in peripheral areas are not located or may be undetected. Many regions, such as the northwestern shore of the Sea of Okhotsk and the adjacent mountains, have never been instrumented, and, as noted above, the station distribution in the Kuriles is extremely uneven. On the other hand, some local regions with historically dense station coverage, and deployments of temporary networks for aftershock studies following significant events (e.g., 1971 Artyk, 1989 South Yakutia), yield areas and time periods with even lower completeness thresholds. In the 1960s and 1970s, K-class values, which were used to determine magnitudes, were usually reported only to the nearest integer or, at best, half-integer. This produces artificial peaks and troughs depending on the conversion formula (see above).
References
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Avetisov, G. P. (1996). Seismicity of the Arctic. Sankt Peterburg: VNIIOkeanologiya, 185 pp. (in Russian)
Biswas, N. N., J. Pujol, G. Tytgat, and K. Dean (1983). Synthesis of Seismicity Studies for Western Alaska, Final report for contract NA81-RAC00112. Fairbanks: University of Alaska, Geophysical Institute, 74 pp.
Godzikovskaya, A. A. (1995). Local Explosions and Earthquakes. Moscow: EES Rossii, 98 pp. (in Russian)
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