Jour. Geol. Soc. Japan, Vol. 117, No. 8, p , August 2011 JOI: JST.JSTAGE/geosoc/ doi: /geosoc Studi

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1 Jour. Geol. Soc. Japan, Vol. 117, No. 8, p , August 2011 JOI: JST.JSTAGE/geosoc/ doi: /geosoc Studies on deep groundwater changes for detecting the precursors of anticipated large earthquakes off Miyagi Prefecture: Observation results from February 2008 to December 2009 Abstract 1, 1 1, 2 1, Yusuke Kashima 1, 1, Yoshie Nasuhara 1, 2, Takashi Nakamura 1, 3, Tsuneo Yamauchi 2 and Kenshiro Otsuki Department of Geology, Graduate School of Science, Tohoku University 2 Department of Earth and Planetary Sciences, Graduate School of Science, Nagoya University, now retired 1 Present address: Niiza High School in Saitama Prefecture 2 Present address: Ministry of Economics, Trade and Industry 3 Present address: Department of Mechanical and Environmental Informatics, Graduate School of Information Science and Engineering, Tokyo Institute of Technology In order to detect the precursors of deep groundwater changes related to the anticipated large earthquakes off Miyagi Prefecture, Japan, we established an observation network of six boreholes with a real-time automatic data-acquisition system. Durning the observation period in and groundwater temperatures and levels in three deep boreholes responded to the off-ibaraki Prefecture earthquake (M J., Japan Meteorological Agency earthquake magnitude scale) on May, the Iwate-Miyagi inland earthquake (M J. ) on June, the off-fukushima Prefecture earthquake (M J. ) on July, and the northern Iwate prefecture coast earthquake (M J. ) on July. Examining the responses of our observation system to the earth tides, volumetric strain changes equivalent to water level changes were estimated at. /mm and. /mm for two of three boreholes. Earthquake-related changes in borehole groundwater levels, which were free from the artifacts, are consistent with the estimates from static volumetric strain changes calculated from dislocation models. The lower detection limit of our observation system to co- and post-seismic groundwater changes is approximated by the equation M J. log r., where r represents hypocentral distance in kilometers. Similar equations can be derived not only from the attenuation relation for static strain changes but also from those for ground motion amplitude. Keywords: Earthquake-related changes, deep boreholes, water temperature, groundwater level, strain change, detection limit Corresponding author; K. Otsuki, otsuki-k@m.tohoku.ac.jp 10 cm/y Fig M J 7.4; M J M J 7.2 Okada et al., 2005; The Geological Society of Japan Miura et al., 2006; Yaginuma et al., M J M J main/choukihyoka/kaikou.htm

2 Fig.. Locality map showing groundwater observation sites. Small open circles: boreholes for the observation of water temperature and water level (AT: Atago, YM: Yamoto, and MN: Minamikata). Small grey circles: boreholes for the observation of radon and carbon dioxide concentrations (KN: Kannari, ON: Onagawa, and YB: Yabitsu). Black star: the epicenter of the 14 June 2008 Iwate-Miyagi inland earthquake (M J 7.2). Contour lines: seismic slips in meter at the asperities off Miyagi prefecture activated in 1936, 1978, 1981, 2003, and 2005 (after Yamanaka and Kikuchi, 2004; Okada et al., 2006; Yaginuma et al., 2006). Solid arrows: displacement vectors of GPS stations by the off-miyagi Prefecture earthquake (M J 7.2) on 16 Aug whose slip is shown in thick solid contour lines (after Miura et al., 2006 and Yaginuma et al., 2006). Thick solid lines: surface traces of active faults (after Research Group for Active Faults, 1980). F1: western marginal fault zone of the Fukushima basin (reverse fault), F2: Sakunami Yashikidaira fault (reverse fault), F3: Futaba fault zone (left-lateral fault), F4: Nagamachi Rifu fault zone (reverse fault), F5: Asahiyama flexure (reverse fault), F6: Ichinoseki-Ishikoshi flexure (reverse fault) , Fig. 1 YB KN MN YM ON AT 6 YB KN ON MN YM AT Fig M J 7.2 GPS Miura et al., 2006; Yaginuma et al., 2006 Fig. 1 F4 F5 F6 ;, 1977 KN MN YM AT AT 830 m AT YM MN AT YM 2011 QTGW 60 C 70 C C S DL Model-4640A 1 mm R hpa, 0.01 hpa

3 AT 830 m, 2011 YM 900 m MN 640 m 1 2 NTT ADSL YM AT 2011 YM m 320 m YM 50 m 200 m 1 900m AT YM 825 m MN 100 m 1 m 360 m 650 m 5 1, 1966, m m m m 420 m m m m m MN YM AT, Fig. 2 w dw/dt kw k t 0 w 0 w w 0 exp kt w w 0 /e t k 1/t Fig. 2 AT 32 MN 20 YM 8 k / YM AT 4 D t D t Fig. 2 D c D b D t D t Fig. 2 AT 833 mm C YM 1400 mm C MN 1714 mm C D t AT C/m YM 0.03 C/m MN C/m D t

4 Fig.. Water level and water temperature changes during the water feeding experiments at the Atago (AT), Yamoto (YM), and Minamikata (MN) boreholes. A schematic diagram illustrating the experiments is showin in the upper left portion of the figure. The water level (thick grey line) rose abruptly by the water feeding at 0 minute and fell down exponentially thereafter. The water temperature (thin black line) at the depths of 900 m in the YM borehole and at 830 m in the AT borehole fell down, while the water temperature at the depth of 640 m in the MN borehole was hardly affected at all. AT 57 D t YM 75 MN 95 D c D t D t D t D c / D b D c AT 6 YM 46 MN 100 AT MN 2011 AT YM AT 4 YM 800 m 900 m m 110 m AT m Fig AT mm mm

5 Fig.. Overview of groundwater level and temperature changes in 2008 and 2009 in the Atago (AT), Yamoto (YM), and Minamikata (MN) boreholes. The upper and lower thin lines in each figure denote the temperature and level of the groundwater, respectively. Thermometer sensor models and the depths at which the thermometer sensor and the water gage were set in the boreholes were sometimes changed. Horizontal lines with arrowheads indicate the timing of measurements when taken with either the quartz (Qtz) or platinum (Pt) thermometer sensor, and the water gauge at a given depth in the borehole. The time at which the depth of the water gage was changed is denoted by the short vertical line with an arrowhead. The measurements of the water level which were measured at different depths were collected by adding appropriate depth differences which are shown next to the thick line with arrowheads. As the differences in water temperature measured at different depths cannot correct precisely, all of the temperature data sets were arranged horizontally adding appropriate temperature differences which are shown next to the thick line with arrowheads mm YM MN mm mm mm AT MN 2 1 m YM 50 cm

6 Fig Tamura et al BAYTAP-G Bayesian Tidal Analysis program- Grouping Model Igarashi and Wakita Matsumoto et al RIO-DB 1 Well Web GSJ/water/analysis/ BAYTAP-G BAYTAP-G ABIC Akaike s Bayesian Information Criteria AT YM MN 1 Fig Fig. A BAYTAP-G 2011 AT YM MN 3.34 mm/hpa R , 8098 MN BAYTAP-G 3.01 mm/hpa R , BAYTAP-G MN 1 K1 O Fig. 4 Fig. A YM MN AT 1 MN 5 7 AT 0.4 C BAYTAP-G GOTIC2 program for Global Oceanic Tidal Correction GOTIC2 Matsumoto et al. 2001

7 Fig.. Hourly groundwater temperature, water level and the precipitation data from 1 May to 31 July 2008 at the Atago (AT), Yamoto (YM) and Minamikata (MN) observation sites. BAYTAP-G was applied to the water level data from all observation sites using the barometric pressure as an associate dataset. The smooth component output from BAYTAP-G is approximated by the linear equations for the data from the AT and YM observation sites, while approximated by a third-order polynomial equation for the data from the MN observation site. Water level values shown in the figures represent the residuals of the smooth component from these regression equations. For the sake of the better presentation 400 mm was added to the original water level data after 21 June 2008 from the MN observation site. Since the raw data of groundwater temperature from all observation sites contain only a minimal components of tidal and barometric effects, BAYTAP-G was not applied. The raw data from the AT, YM and MN observation sites were approximated by a second-order polynomial equation, a linear equation and a forth-order polynomial equation, respectively. The residuals from these regression equations were plotted in the figures. The precipitation data were obtained from the nearby observatories of Japan Meteorological Agency. The cumulative precipitation for each rainfall event is plotted in the figures. The circled numerals 1, 2, 3, 4 denote the timinig of the off-ibaraki Prefecture earthquake (M J 7.0) on 8 May 2008, Iwate-Miyagi inland earthquake (M J 7.2) on 14 June 2008, off-fukushima Prefecture earthquake (M J 6.9) on 19 July 2008, and the northern Iwate prefecture coast earthquake on 24 July 2008 (M J 6.8).

8 NAO.99b BAYTAP-G GOTIC2 M M2 N2 S2 1 MN mm mm 1 2 mm 2 1 mm mm 6 BAYTAP-G M2 4.2 mm GOTIC /mm MN 1 1 mm Figs. 5, 6, 8 9 BAYTAP-G MN mm 0.74 mm MN m m 0.05 C BAYTAP-G AT mm 1, 1 mm 3, 0.5 mm 5 BAYTAP-G M mm mm GOTIC2 M AT /mm AT 1 1 mm BAY- TAP-G mm 0.38 mm AT AT BAYTAP-G GOTIC /m C , 2011 YM M2 BAY- TAP-G Table 1 2 Figs BAY- TAP-G 8 4 MN http// AT YM MN a M J. AT YM MN 239 km 254 km 277 km 3 MICAP-G Okada, 1992;, Fig. 5 AT YM AT BAYTAP-G 1

9 Table. List of source parameters of the four earthquakes. Fig.. Groundwater changes in the Atago (AT), Yamoto (YM) and Minamikata (MN) boreholes caused by the off-ibaraki Prefecture earthquake (M J 7.0) at 1:45 on 5 May 2008 (arrows). The pairs of grey and black lines labeled with T and L in the upper figures denote the temperature and level of groundwater, respectively. Grey lines represent the raw data at 1 minute intervals, while the black lines represent their trend components output from BAYTAP-G which was applied to the hourly data. The lower figures are the enlarged views of the raw data of the groundwater temperature (grey line labeled with T ) and the water level (black line labeled with L ) over a period of about 4 hours before and after the earthquake. The scales of the temperature and the water level are attached to the left and right sides of the figures, respectively. 5 mm YM 1:48 2:00 34 mm 2:30 52 mm C 2: C AT YM b : M J. MN 47 km 5 YM 70 km 4 AT 87 km 5 Ohta et al MICAP-G MN YM AT Fig. 7 MN 1 15 Fig C mm 600 mm Fig. 3 Fig. 4 Fig. A MN 400 mm

10 Fig.. Groundwater changes in the Atago (AT), Yamoto (YM) and Minamikata (MN) boreholes caused by the Iwate-Miyagi inland earthquake (M J 7.2) at 8:43 on 14 June For further information, see Fig. 5. YM :46 9: C C Fig Fig C 19 YM :44 8:49 25 mm 9: mm 6 24 Fig. 4 AT C 8:43 8: C 8:55 9: C 10: C C AT 14 8:50 3 mm 9:35 12 mm AT c : M J. YM AT MN 144 km km km 4 MICAP-G AT YMY MN AT 11:42 BAYTAP-G 13:00 32 mm 0.13 C 14:50 3 YM C 11:40 13 mm 1 7 mm 12:10 7 mm 8 mm 1 BAYTAP-G MN 19 11:40 11: C 11:17 11:39 11:42 12:40 9 mm BAYTAP-G

11 d : M J. 100 km MN YM AT 168 km km 208 km MN YM 5 AT 4 MICAP-G MN C 2: mm YM C 0:50 0:27 9 mm 0:50 23 mm AT 35 0:27 3 mm 0:28 4 mm 0:50 15 mm a 4 Fig. 10 AT YM mm, Huang et al., Fig.. Distribution of static volumetric strain changes associated with the 2008 Iwate-Miyagi inland earthquake (M J 7.2). The two rectangles denote west-dipping fault planes. Strain distribution was calculated by MICAP-G using the source parameters of Ohta et al. (2008). Black and grey contour lines denote the dilatation and contraction, respectively. The contours are drawn at 10 1/6 intervals, and the attached numerals represent the power value of 10 of volumetric strain. Small black circles labeled with MN, YM and AT are the locations of our observation sites. 1 YM 5 25 mm mm 600 mm 3 YM YM AT YM C AT C C YM C 7 10

12 Fig.. Groundwater changes in the Atago (AT), Yamoto (YM) and Minamikata (MN) boreholes caused by the off-fukushima Prefecture earthquake (M J 6.9) at 11:39 on 19 July For further imformation, see Fig. 5. Fig.. Groundwater changes in the Atago (AT), Yamoto (YM) and Minamikata (MN) boreholes caused by the northern Iwate Prefecture coast earthquake (M J 6.8) at 0:26 on 24 July For further imformation, see Fig. 5.

13 Fig.. Amplitudes of the earthquake-related changes in groundwater temperature in the main phase as a function of (a) the duration of the main phase and (b) the amplitude of groundwater temperature changes in the initial phase. Fig.. Schematic variation patterns of the level (WL) and temperature (WT) of groundwater in the Atago (AT), Yamoto (YM) and Minamikata (MN) boreholes caused by the off-ibaraki prefecture earthquake, Iwate-Miyagi inland earthquake, off-fukushima prefecture earthquake and the northern Iwate prefecture coast earthquake. The short thin and long thick lines denote the changes in the initial and main phases, respectively. Question marks indicate that the initial changes are unknown due to the missing data caused by the electric power failures. Earthquake intensities (bold numerals) of the Japanese scale are shown. Shading denotes observations where the polarity of observed groundwater changes was opposite to the polarity expected from the static volumetric strain change calculated by a dislocation model C C Fig. 11a 3 Fig. 11b b, Igarashi and Wakita, 1991; Muir-Wood and King, 1993; Quilty and Roeloffs, 1997; Wang, 1997; Roeloffs, 1998; Koizumi et al., 1999; Jónsson et al., 2003; Akita and Matsumoto, 2004; Koizumi et al., MICAP-G 4 MN YM AT 5 AT /mm /m C MN /mm MICAP-G 3 5 MN AT AT 5 YM AT 4 MN 3 Fig. 12 MN 1 mm 8 7 AT MN 1 AT 68 mm 12 mm Fig. 12 AT C 0.01 C C C MN YM Fig

14 Fig YM YM 3 YM YM AT Matsumoto et al., 2003, Roeloffs, 1998; Manga and Wang, 2007; Chia et al., 2008a, b Fig. 13,, c M r r M M alogr b 1 Fig M J , M J M J M J 6.2 Fig a b r km M M J a 2.4 b 1.0 M J 2.4 logr 1.0 Roeloffs 1998 a 1.81 b 1.6 Roeloffs et al a 1.68 b 2.58 Matsumoto et al a 2.45 b 0.45 Montgomery and Manga 2003 a 2.3 b r M w M w M w M w alog r/r M o M w logm o 1.5M w 16.1 M o /M o r/r 1.5a 2 d vs 1 1 r u Aki and Richards, 1980 u r 4 r 2 r 1 near field intermediate far filed near field intermediate M o r 2 Δε M o r 3 M o M w logm o 1.5M w 16.1 M w M J M J 2logr C 3 1 a 2 C 1 b a 2

15 u far filed u r 1, r 2 D km M w r km A cms 2 loga 0.50M w D 0.61 log r Mw 0.003r, A 1 M w 2.0logr 2.0logA log D-0.003r A 4 logr-m w 2 r a 2 1 Fig. 13 Fig. 12 AT YM MN BAYTAP-G M2 GOT- IC2 M2 MN /mm AT /mm M J M J M J Fig.. Comparison of observed groundwater level changes with those estimated from the theoretical volumetric strain changes associated with earthquakes. The downward arrow means that the change is smaller than the resolution limit (1 mm) of our observation system. Fig.. Correlations between earthquake intensity (in the scale of Japan Meteorological Agency) and the changes in groundwater (a) level and (b) temperature during the main phases. The absolute values of the level and temperature changes are shown. Black and white symbols represent a decrease and increase of the observed values, respectively. M J AT MN 5 r km M J M J 2.4logr 1.0 2

16 Fig.. Hypocentral distance r versus earthquake magnitude M J determined by Japan Meteorological Agency. Small grey squares denote earthquakes with no detectable groundwater changes. The other symbols represent the earthquakes with related changes in groundwater temperature (open symbols) and water level (black symbols) as detected in the Atago (AT, square), Yamoto (YM, circle), and Minamikata (MN, diamond) boreholes. The thick broken line represents the detection limit to co- and post-seismic groundwater changes. website BAYTAP-G website GOTIC2 website 2 A Aki, K. and Richards, P. G., 1980, Quantitative Seismology: Theory and Methods. Vol. II, W. H. Freeman and Company, San Francisco, Akita, F. and Matsumoto, N., 2004, Hydrological responses induced by the Tokachi-oki earthquake in 2003 at hot spring well in Hokkaido, Japan. Geophys. Res. Lett., 31, L16603, doi: /2004GL Chia, Y., Chiu, J. J., Chiang, Y. H., Lee, T. P., Wu, Y. M. and Horng, M. J., 2008a, Implications of coseismic groundwater level changes observed at multiple-well monitoring stations. Geophys. Jour. Int., 172, Chia, Y., Chiu, J. J., Chiang, Y. H., Lee, T. P. and Liu, C. W., 2008b, Spatial and temporal changes of groundwater level induced by thrust faulting. Pure Appl. Geophys., 165, Huang, F. Q., Jian, C. L., Tang, Y., Xu, G. M., Deng, Z. H. and Chi, G.C., 2004, Response changes of some wells in the mainland subsurface fluid monitoring network of China, due to the September 21, 1999, M s7.6 Chi-Chi Earthquake. Tectonophysics, 390, Igarashi, G. and Wakita, H., 1991, Tidal response and earthquake-related changes in the water level of deep wells. Jour. Geophys. Res., 96, Ishiguro, M., Sato, T., Tamura, Y. and Ooe, M., 1984, : BAYTAP Proc. Inst. Statistical Mathematics, 32, The Headquarters for Earthquake Research Promotion, 2001, jishin.go.jp/main/index.html. Jónsson, S., Segall, P., Pedersen, R. and Björnsson, G., 2003, Post-earthquake ground movements correlated to pore-pressure transients. Nature, 424, Koizumi, N., Tsukuda, E., Kamigaichi, O., Matsumoto, N., Takahashi, M. and Sato, T., 1999, Preseismic changes in groundwater level and volumetric strain associated with earthquake swarms off the east coast of the Izu Peninsula, Japan. Geophys. Res. Lett., 26, Koizumi, N., Kitagawa, Y., Matsumoto, N., Takahashi, M., Sato, T., Kamigaichi, O. and Nakamura, K., 2004, Preseismic groundwater level changes induced by crustal deformations related to earthquake swarms off the east coast of Izu Peninsula, Japan. Geophys. Res. Lett., 31, L10606, doi: /2004JL Manga, M. and Wang, C. Y., 2007, Earthquake Hydrology. In Schubert, G. editor in chief, Treatise on Geophysics, Vol.4, Earthquake Seismology, Section 10, , Elsevier, Amsterdam. Matsumoto, K., Sato, T., Takanezawa, T. and Ooe, M., 2001, GOTIC2: Program for computation of oceanic tidal loading effect. Jour. Geod. Soc. Japan, 47, Matsumoto, N., Kitagawa, G. and Roeloffs, E. A., 2003, Hydrological response to earthquakes in the Haibara well, central Japan I. Groundwater level changes revealed using state space decomposition of atmospheric pressure, rainfall and tidal responses. Geophys. Jour. Int., 155, Matsumoto, N. and Takahashi, M., 1993, 2 Jour. Seismol. Soc. Japan, 2nd series, 45, Matsuno, H., 1966, Geology of the Wakayanagi area, 5 1, 6 69, Quadrangle Series Scale 1: 50,000, Akita 6, No.69, Geol. Surv. Japan, 24p. abstract 5p. Miura, S., Iinuma, T., Yui, S., Uchida, N., Sato, T., Tachibana, K. and Hasegawa, A., 2006, Co- and post-seismic slip associated with the 2005 Miyagi-oki earthquake M7.2 as inferred from GPS data. Earth Planets Space, 58, Montgomery, D. R. and Manga, M., 2003, Streamflow and water well responses to earthquakes. Science, 300, Muir-Wood, R. and King, G. C. P., 1993, Hydrological signatures of earthquake strain. Jour. Geophys. Res., 98, Naito, H. and Yoshikawa, S., 1999, MICAP-G 2 Jour. Seismol. Soc. Japan, 2nd series, 52, Nasuhara, Y., Kashima, Y., Nakamura, T., Yamauchi, T. and Otsuki, K., 2011, : Jour. Geol. Soc. Japan, 117, Ohta, Y., Ohzono, M., Miura, S., Iinuma, T., Tachibana, K., Takatsuka, K., Miyao, K., Sato, T. and Umino, N., 2008,

17 Coseismic fault model of the 2008 Iwate-Miyagi Nairiku earthquake deduced by a dense GPS network. Earth Planets Space, 60, Okada, Y., 1992, Internal deformation due to shear and tensile faults in a half-space. Bull. Seism. Soc. Am., 82, Okada, T., Yaginuma, T., Umino, N., Kono, T., Matsuzawa, T., Kita, S. and Hasegawa, A., 2005, The 2005 M7.2 MIYAGI- OKI earthquake, NE Japan: Possible rerupturing of one of asperities that caused the previous M7.4 earthquake. Geophys. Res. Lett., 32, doi: /2005GL Otsuki, K., Nakata, T. and Imaizumi, T., 1977, Earth Science, 31, Quilty, E. G. and Roeloffs, E. A., 1997, Water-level changes in response to the 20 December 1994 earthquake near Parkfiled, California. Bull. Seismol. Soc. Am., 87, Research Group for Active Faults, ed., 1980, : Active Faults in Japan: Sheet Map and Inventories. 363p.,, Roeloffs, E. A., 1998, Persistent water level changes in a well near Parkfield, California, due to local and distant earthquakes. Jour. Geophys. Res., 103, Roeloffs, E., Sneed, M., Galloway, D. L., Sorey, M. L., Farrar, C. D., Howle, J. F. and Hughes, J., 2003, Water-level changes induced by local and distant earthquakes at Long Valley caldera, California. Jour. Volcanol. Geotherm. Res., 127, Si, H. and Midorikawa, S., 1999,. Jour. Struct. Constr. Eng., AIJ, no.523, Takahashi, H. and Matsuno, H., 1968, Geology of the Wakuya area, 5 1, 6, 78, Quadrangle Series, Scale 1: 50,000, Akita 6, No.78, Geol. Surv. Japan, 26p. abstract 6p. Tamura, Y., Sato, T., Ooe, M. and Ishiguro, M., 1991, A procedure for tidal analysis with a Bayesian information criterion. Geophys. Jour. Int., 104, Wang, H. F., 1997, Effects of deviatoric stress on undrained pore pressure response to fault slip. Jour. Geophys. Res., 102, Yaginuma, T., Okada, T., Yagi, Y., Matsuzawa, T., Umino, N. and Hasegawa, A., 2006, Coseismic slip distribution of the 2005 off Miyagi earthquake M7.2 estimated by inversion of teleseismic and regional seismograms. Earth Planets Space, 58, Yamanaka, Y. and Kikuchi, M., 2004, Asperity map along the subduction zone in northeastern Japan inferred from regional seismic data. Jour. Geophys. Res., 109, doi: 2003JB Appendix Appendix Fig. A. Hourly data of the groundwater temperature, water level and the precipitation during 2008 and 2009 at the Atago (AT, Fig. Aa), Yamoto (YM, Fig. Ab) and Minamikata (MN, Fig. Ac) observation sites. Kashima, Y., Nasuhara, Y., Nakamura, T., Yamauchi, T. and Otsuki, K., 2011, Studies on deep groundwater changes for detecting the precursors of anticipated large earthquakes off Miyagi Prefecture: Observation results from February 2008 to December Jour. Geol. Soc. Japan,, M J 7.0; M J 6 14 M J M J M J /mm /mm M J 2.4logr 1.0 r km

Fig. 1. Horizontal displacement of the second and third order triangulation points accompanied with the Tottori Earthquake of (after SATO, 1973)

Fig. 1. Horizontal displacement of the second and third order triangulation points accompanied with the Tottori Earthquake of (after SATO, 1973) Journal of the Geodetic Society of Japan Vol. 27, No. 3, (1981), pp. 183-191 Research on Fault Movement by means of Aero-Triangulation ( T) (An experiment on the earthquake fault of the Izu-Oshima Kinkai