117 8 451 467 2011 8 Jour. Geol. Soc. Japan, Vol. 117, No. 8, p. 451 467, August 2011 JOI: JST.JSTAGE/geosoc/117.451 doi: 10.5575/geosoc.117.451 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, 3 2 1 Yusuke Kashima 1, 1, Yoshie Nasuhara 1, 2, Takashi Nakamura 1, 3, Tsuneo Yamauchi 2 and Kenshiro Otsuki 1 2010 10 9 2011 6 10 1 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. 1 2001 37.1 1978 6 12 M J 7.4; M J 2005 8 16 M J 7.2 Okada et al., 2005; The Geological Society of Japan 2011 451 Miura et al., 2006; Yaginuma et al., 2006 2005 12 3 M J 6.6 2005 8 16 M J 7.4 2010 1 1 10 70 http://www.jishin.go.jp/ main/choukihyoka/kaikou.htm
452 2011 8 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. 2005 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). 2004 6 20, 2011 2011 2004 2007 2008 2009 3 Fig. 1 YB KN MN YM ON AT 6 YB KN ON MN YM AT Fig. 1 2005 8 16 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 0.0002 C S DL Model-4640A 1 mm R-30 0.5 hpa, 0.01 hpa
117 8 453 AT 830 m, 2011 YM 900 m MN 640 m 1 2 NTT ADSL YM AT 2011 YM 351 733 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, 1968 360 m 410 470 m 530 600 m 630 650 m 420 m 420 464 m 519 596 m 623 645 m 630 650 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 0.031 0.05 0.13/ YM AT 4 D t D t Fig. 2 D c D b D t D t Fig. 2 AT 833 mm 56 0.04 C YM 1400 mm 0.004 C MN 1714 mm 0.008 C D t AT 0.028 C/m YM 0.03 C/m MN 0.026 C/m D t
454 2011 8 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 800 900 m 110 m AT 2011 1 2 1000 m Fig. 3 2008 2 2009 12 1 AT 2008 2 10 1 6 9 10 1180 mm 2008 6 19 20 10 27 10 1010 mm 2008 10
117 8 455 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. 27 18 2009 4 3 13 650 mm YM MN 2008 8 27 16 2126 mm 2008 8 27 17 2009 6 12 13 366 mm 2006 6 14 600 mm AT MN 2 1 m YM 50 cm
456 2011 8 Fig. 3 1 2011 1984 Tamura et al. 1991 BAYTAP-G Bayesian Tidal Analysis program- Grouping Model Igarashi and Wakita 1991 1993 Matsumoto et al. 2003 RIO-DB 1 Well Web http://riodb02.ibase.aist.go.jp/gxwell/ GSJ/water/analysis/ 1 3000 30 1 BAYTAP-G BAYTAP-G 3 2 0 ABIC Akaike s Bayesian Information Criteria 4 2008 5 1 7 31 AT YM MN 1 Fig. 4 2008 2009 Fig. A BAYTAP-G 2011 AT YM MN 3.34 mm/hpa R 2 0.905, 8098 MN BAYTAP-G 3.01 mm/hpa R 2 0.871, 11832 BAYTAP-G 2009 6 12 19 MN 1 K1 O1 1 3 1 Fig. 4 Fig. A YM MN AT 1 MN 5 7 AT 0.4 C 2011 1 BAYTAP-G GOTIC2 program for Global Oceanic Tidal Correction GOTIC2 Matsumoto et al. 2001
117 8 457 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).
458 2011 8 http:// www.miz.nao.ac.jp NAO.99b BAYTAP-G GOTIC2 M2 12.42 M2 N2 S2 1 MN 2008 10 29 0 11 24 23 5 mm 1 2.5 mm 1 2 mm 2 1 mm 1 0.5 mm 6 BAYTAP-G M2 4.2 mm GOTIC2 9.531 10 9 1 2.27 10 9 /mm MN 1 1 mm Figs. 5, 6, 8 9 BAYTAP-G MN 1 13000 0 mm 0.74 mm 18 1 1 2.27 10 9 MN 2009 4 640 m 2009 6 12 640 m 0.05 C 2009 11 20 12 31 BAYTAP-G AT 2009 3 8 0 4 1 11 2 mm 1, 1 mm 3, 0.5 mm 5 BAYTAP-G M2 18.7 mm 0.093 mm GOTIC2 M2 9.35 10 9 2 AT 0.5 10 9 /mm AT 1 1 mm BAY- TAP-G 1 15200 0 mm 0.38 mm 2 1 1 AT 0.5 10 9 AT BAYTAP-G GOTIC2 1 10 8 /m C 1 10 8, 2011 YM M2 BAY- TAP-G 2008 4 Table 1 2 Figs. 5 6 8 9 1 1 BAY- TAP-G 8 4 MN http//www.jma.go.jp/jp/quake/ AT YM MN a M J. AT YM MN 239 km 254 km 277 km 3 MICAP-G Okada, 1992;, 1999 1 3 10 9 Fig. 5 AT YM AT BAYTAP-G 1
117 8 459 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 14 0.0005 C 2:00 2 0.003 C AT YM b : M J. MN 47 km 5 YM 70 km 4 AT 87 km 5 Ohta et al. 2008 MICAP-G MN 1.3 10 6 YM 2.8 10 7 AT 3.4 10 8 Fig. 7 MN 1 15 Fig. 6 0.023 C 6 21 12 15 450 mm 600 mm Fig. 3 Fig. 4 Fig. A MN 400 mm
460 2011 8 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 2008. For further information, see Fig. 5. YM 6 14 8:46 9:06 0.005 C 12 0.015 C Fig. 6 15 6 16 Fig. 4 17 0.02 C 19 YM 6 14 8:44 8:49 25 mm 9:30 220 mm 6 24 Fig. 4 AT 2 3 0.01 C 8:43 8:50 0.034 C 8:55 9:08 0.028 C 10:30 0.074 C 22 15 3 0.025 C AT 14 8:50 3 mm 9:35 12 mm AT c : M J. YM AT MN 144 km 3 150 km 2 165 km 4 MICAP-G AT YMY 2 10 8 MN 1.3 10 8 AT 11:42 BAYTAP-G 13:00 32 mm 0.13 C 14:50 3 YM 12 0.0005 C 11:40 13 mm 1 7 mm 12:10 7 mm 8 mm 1 BAYTAP-G MN 19 11:40 11:44 0.009 C 11:17 11:39 11:42 12:40 9 mm BAYTAP-G
117 8 461 d : M J. 100 km MN YM AT 168 km 184.3 km 208 km MN YM 5 AT 4 MICAP-G 3 6 8 10 9 MN 45 0.012 C 2:25 1 52 12 mm 24 16 25 24 5 9 12 YM 1 10 0.001 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 5 5 4 1 2 9 mm, Huang et al., 2004 1 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 11 20 120 12 mm 600 mm 3 YM YM AT YM 14 0.0005 C AT 7 0.034 C 18 0.028 C YM 20 0.005 C 7 10
462 2011 8 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 2008. 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 2008. For further imformation, see Fig. 5.
117 8 463 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. 180 0.0005 C 0.072 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., 2004 6 MICAP-G 4 MN YM AT 5 AT 0.5 10 9 /mm 1 10 8 /m C MN 2.27 10 9 /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 4 0.002 C 0.01 C 0.0034 C 0.074 C MN YM Fig. 10 7 4 4 3
464 2011 8 11 7 4 Fig. 10 7 6 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. 14 3 6 4 2011 3 2010 3 14 M J 6.7 7 4, M J 5.2 7 5 M J 6.4 8 10 M J 6.2 Fig. 14 1 1 2 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. 2003 a 1.68 b 2.58 Matsumoto et al. 2003 a 2.45 b 0.45 Montgomery and Manga 2003 a 2.3 b 0.1 1 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
117 8 465 u far filed u r 1, r 2 D km M w r km A cms 2 loga 0.50M w 0.0043D 0.61 log r 0.0055 10 0.5Mw 0.003r, 1999 1 2 3 A 1 M w 2.0logr 2.0logA log 4.07 10 0.0043D-0.003r 0.0055A 4 logr-m w 2 r a 2 1 Fig. 13 Fig. 12 AT YM MN 2008 2009 1 3 2 BAYTAP-G M2 GOT- IC2 M2 MN 2.27 10 9 /mm AT 0.5 10 9 /mm 3 2008 5 8 M J 7.0 2008 6 14 M J 7.2 2008 7 19 M J 6.9 2008 7 24 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 6.8 4 AT MN 5 r km M J M J 2.4logr 1.0 2
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