1. Abstract 2016-2754- Session SM1.1 At present, there is a great debate over whether or not we are in a global cluster of large earthquakes, temporarily raising risks above long ‐ term levels [e.g. 1 - 8]. On the clustering of large earthquakes in the end of 19 th – beginning of 20 th centuries is reported in [1]: strongest earthquakes occurred in Tien Shan (1889, M=8.3; and 1911, M=8.2); Alaska (1899, M=8.0); Kashgaria (1902, M=8.2); Mongolia (1905, M=8.2); San Francisco (1906, M=8.3), China(1906, M=8.3); Columbia (1906, M=8.6). Let us denote this temporal period as (Eq_clust_1). Authors of [7,8] discussed the clustering of large earthquakes in the middle of the 20 th century, when the three moment magnitude (M w )≥9 occurred within 12 years of each other (in 1952, 1960, and 1964). Let us denote this temporal period as (Eq_clust_2). On the clustering of large earthquakes in the beginning of the 21 st century was reported in [2-6] after the occurrence of 5 Mw ≥ 8.5 events from 2004–2011. Let us denote this temporal period as (Eq_clust_3). Figure 1 is adapted from [4], where we have marked with ovals the three periods of great earthquakes clustering as indicated in above. Fig. 1 Global earthquake record (adapted from [4]), the ovals mark three periods of large earthquake clustering. Fig. 2 Yearly sunspot numbers from 1700; the grand solar minima occurred near 1711, 1810, 1913, and 2008 are marked with triangles, the ovals in top mark three periods of great earthquake clustering. Figure 2 presents yearly sunspot numbers from 1700 [9]. The main feature of sunspot variations is a quasi-11 year solar cycle, which numbered from 1755 year (positive digits 1- 24). The sunspot record shows changes in amplitude of the11 year solar cycle. During 300 years, there were four times when yearly sunspot numbers decreased almost to zero: in 1711, 1810, 1913 and 2008 years, that are the grand solar minima. These minima restrict three long-term solar cycles called the Centennial Gleissberg Cycle (CGC) [10, 11]. It is considered that the duration of the CGC is of 90-100 years [10, 11]. Fig. 2 shows that each of three CGC cycle included exactly nine quasi-11 year solar cycles. The recent CGC was lasting from 1913 to 2008, with a great solar maximum around of 1958 year. In the top of Fig.2, we mark with ovals the periods of great earthquake clustering (Eq_clust_1; Eq_clust_2; and Eq_clust_3) in accordance with Fig.1. It is seen that the time of great earthquake clustering has occurred in alignment with two minima and one maximum of the recent Centennial Gleissberg Cycle. The physical reason of the CGC is not known yet, and it is not excluded that a such reason could influence simultaneously both the Sun‘s and Earth’s dynamics. This, in turn, rises a question on solar-lithosphere coupling. In conclusion: 1) The problem of solar-lithosphere coupling needs more attention that it has at present. 2) On the base of instrumental sunspot record (from 1700) and instrumental seismological record for strong earthquakes (from 1900), one may suggest that the next period of great earthquake clustering may occur in the maximum of the next Centennial Gleissberg Cycle, which is expected to be around of the maximum of the 28 th eleven-year solar cycle. [1] Lutikov A. I., E. A. Rogozhin. Variations in the intensity of the global seismic process in the 20th and the beginning of 21st centuries. Izvestiya, Physics of the Solid Earth. July 2014, Volume 50, #4.pp 484-500. [2] Daub E. G., E. Ben-Naim, R. A. Guyer, and P. A. Johnson. Are megaquakes clustered? arXiv:1203.103[v] [physics.geo-ph] 5 Mar. 2012, X1-X5. [3] Shearer, P. M., and P. B. Stark (2012) Global risk of big earthquakes has not recently increased, Proc. Nat. Acad. Sci., 109, 717-721. [4] Michael, A. J. (2011), Random variability explains apparent global clustering of large earthquakes, Geophys. Res. Lett., 38, L21301, doi:10.1029/ 2011GL049443. [5] Bufe, C. G., and D. Perkins (2011), The 2011 Tohoku earthquake: Resumption of temporal clustering of Earth’s megaquakes, Seismol. Res. Lett., 82, 455 [6] Ammon CJ, Lay T, Simpson DW (2010) Great earthquakes and global seismic networks. Seismol Res Lett 81:965–971. [7] Bufe CG, Perkins DM (2005) Evidence for a global seismic-moment release sequence. Bull Seismol Soc Am 95:833–843. [8] Romanowicz B (1993) Spatiotemporal patterns of energy release of great earthquakes. Science 260:1923–1926. [9] Yearly Sunspot Numbers, source: WDC-SILSO, Royal Observatory of Belgium, Brussels".http://www.sidc.be/silso/datafileshttp://www.sidc.be/silso/datafiles [10] Feynman J.,A. Ruzmaikin. The Sun’s Strange Behavior: Maunder Minimum or Gleissberg Cycle? // Solar Phys. 2011 V. 272. P. 351–363. DOI 10.1007/s11207- 011-9828-0. [11] Feynman, J., A. Ruzmaikin. The Centennial Gleissberg Cycle and its association with extended minima // J. Geophys. Res. Space Physics. 2013. V. 119. P. 6027– 6041. doi:10.1002/2013JA019478 The question on solar-lithosphere coupling is very speculative and controversial now, but it is impossible to conclude that a such coupling is absent at all. For example, in Fig. 3 we present occurrence of strong (M=>7.0) earthquakes in Eurasia (30-45N; 0-110E) in alignment with monthly sunspot numbers. Black solid line in Fig.3 is a long-term linear trend in sunspot numbers. Dates of earthquakes occurred for solar activity above the trend are marked with red squares, while those ones occurred below the trend are marked with black circles. There were 32 strong earthquakes at this area in 1973-2014 (NEIC catalog), and Fig. 3 demonstrates that a half of them occurred in increased solar activity (above trend) and a half occurred in decreased solar activity (below trend). The quick conclusion may be: there is no solar-lithosphere coupling. At the same time, the results in Fig.4 give a hint that the sign of solar-lithosphere coupling may vary depending on structure and composition of the lithosphere. In particular, Fig.4 demonstrates that at the European part of considered area, the strongest earthquakes occur mainly in increased solar activity (14 events out of 16, i.e. 87.5%), while at the Asian part of area, the strongest earthquakes occurred mainly during decreased solar activity (13 events out of 16, i.e. 81.25%). Fig.3 Fig. 4 European Geosciences Union, General Assembly Vienna | Austria | 17-22 April 2016 EVIDENCE FOR EXTERNAL FORCING TEMPORAL CLUSTERING OF GREAT EARTHQUAKES Galina Khachikyan, Beibit Zhumabayev, Nursultan Toyshiev, Dina Kairatkyzy, Azamat Kaldybayev, and Serik Nurakynov "Institute of Ionosphere”, "National Center for Space Research and Technology", Almaty, Kazakhstan