Study on mine earthquake activity rules for Laohutai coal mine in Fushun of Liaoning

Global Geology,14(2):102-105(2011)doi:10.3969/i.isn.16739736.2011.02.06Article I:16739736(2011)02-0102.04Study on mine earthquake activity rules for Laohutai coal minein Fushun of Liaoninghan Xiaomin. chen Li and sun Wenda1. College of Construction Engineering, Jilin Universily, Changchun 130026, China2. A. Alfred Taubman College of Architecture and Urban Planning, University of Michigan, Ann Arbor 48109, USAAbstract: According to earthquake data of Fushun earthquake administration, the seismic analysis and statisti-al methods are utilized in order to analyze earthquake frequency, "b-value timing and energy creep trends inLaohutai coal mine. By using least squares linear regression method, the relational expression between frequen-cy and magnitude of mine earthquake in Laohutai coal mine is given. And the possible largest magnitude mineearthquake inferred has also been calculated. And this paper also provides a theoretical basis for further study ofmine earthquake activityKey words: mine earthquake; earthquake frequency; energy creep curve; "b-value method; magnitude prediction1 Introductioning area is about 5 km; north-south width is 2and the area is about 10 km2Mine earthquake is a natural disaster of mineThe sublayer of Laohutai Coal Mine is Presinianinduced by mining operations Pan, 2003 Man, system granitic gneiss. The Cretaceous sandstone and2006). Recent years, with mining depth and mining shale is on the Presinian system strata and the relantensity increasing, mine earthquake occurred fre-tionship between of them is in unconformability. Thequently in Laohutai coal mine. The largest magnitude coal seam is the terrestrial deposit stratum in Tertiarywas 3. 7. it caused serious darThe coal seam is thick. The overlying rocks are argil-mining area, and injured 10 people in 2002. The sen- lite, shale, oil shale and so on, which belong to Eo-sory area is over 200 km*. In order to prevent or miti-cene.The coal field is parallel with NEe treneate the disasters, we analyzed and predicted the seissyncline structure. And its north limb is steeper thanmic activity, according to the monitoring data and the south limb. The biggest buried depth of coal seamcombined researching methods of seismic activity.is more than 1 000 m2 Overview of mining areaThe most depth of mining coal has reached morehan 700 m in Laohutai coal mine and the annualLaohutai Coal Mine is in southeast of Fushun Cit- mining quantity is about 300 million tons.They and in central Fushun Coal Field to south coast of method are fully mechanized top coal caving miningthe hun river. And it,s in the north side of the hunand water sand filling coal seam by inclined slicingRiver deep fault, the east is Longfeng Coal Mine, the The中国煤化工 the coalbed meth-west is of Shengli Coal Field. East-west length of min什HCNMH Gng tremor not onlyReceived 28 March 2011, accepted 24 April 2011Study on mine earthquake activity rules for Laohutai coal mine in Fushun of Liaoning103atens the miners security and claimed 40 liveTable 1 Frequency of mine earthquake in 1988-2003but also affects the stability of buildings and security(after Li, 2004; Liu, 2007)of lives in Fushun City. 3 Mine earthquake activity a-Yearnalysis1.0-2.02.1-3.03.1-3.53.6-37 frequen3. 1 Mine earthquake frequency analysisFig. la shows that the frequency curve of mine1990577161earthquake was almost no large fluctuations from 1975to 1990, showed an increasing trend, and reached itshighest value in 2002. In subsequent years, the fre-quency of mine earthquake decreased slightly1994462Table 1 shows that from 1988 to 1995, magnitude of M,e2.0 mine earthquake occurred in the fre-quency of 16. 75; M, 23 0 mine earthquake occurredin the frequency of 0. In those years, it affected the06681815afety of the mine production slightly. After 1995, theoccurrence of M, 22.0 mine earthquake is in the fre-2000125586quency of 83. 857; M> 3. 0 is in the frequency of1385. 428. So it has certain influences on the mining and200240510011afety of lives of Fushun City.1136(a)o HTT87199319992005(a)M≥0,1975-2006;(b)M1≥3.0,19952003Fig 1 Frequency of mine earthquakeFig. 1 shows that mine earthquakelar- version formula of earthquake magnitude of the Guten-ly active during 2001-2003. The growing trends of berg formula( Zhang, 1996)is used in Fushun CityMi3.0 were very obvious. It shows that the mininghat islgE=4.8+1.5M,the gradual extension of mining deptlWhere E is strain energy, M, is natural earth-3.2 Analysis of strain energyMine earthquake and natural earthquake are allThe conversion relationship between M, and M, isthe crust rapid release of seismic energy as the process as following(Zhang. 1996)of caused vibration. Earthquake magnitude is a meas-中国煤化工0(2)of earthquake size, and related to the earthquakeWillCNMHGgy. According to monitoring data, the energy con-lgE=3.18+1.695M(3)Han X M., Chen L. and Sun W. DWhere M, is mine earthquake magnitudehas been in a nonlinear acceleration phase sinceFormula(3)is called the Gutenberg energy1997, and most of big mine earthquakes also occur inmagnitude relationshiip This formula shows whene nonlinear acceleration phase( Table 1)creases about 32 times. By using formula(3), earthergy(e)of Laohutai coal mine from1988 to 2000 is calculated and the energy curve( Fig2)of mine earthquake is described. Fig. 2 and Table2 show that it is the first time jumping in energy release obviously in 1995. That year seismic wave ener-gy is 3 times of former 7 years on the average. Andenergy increased rapidly in 1998. And seismic wave9861988199019921994199619982000energy is ten times on the average of former 7 years inTime/a1998. The seismic wave energy in the first nineFig 3 Strain energy creep curve of mine earthquake inmonths of 2000 is 25 times on the average of former 7Laohutai coal mineyearsTable 2 Statistics energy(M, 21.0, 1988.. 9)Strain energy creep curve ofshown by the accumulateon -sEenm8earthquake reflects real changes in regional stress4.20×1031.40x10°field, and reflects that preparation process of the1.62×10°5.69×108strong earthquake could affect local stress field of4.75×109force in the mining area( Ren, 2010)5.25X19993.3 b-value timing characteristics of mine2000.1~9LI I06.92×108Mine earthquake and natural earthquake are all0.9subject to Gutenberg and Richter(G-R)law, whichlogn a-bM4)Where, N is the correspondquakes of a range magnitude M+AM; a is the meas-02ured of mine earthquake activity level; b is a factor;log/ is slope of the line to the linear fitting of statisti-19861988199019921994199619982000b-value is an important parameter to describeFig. 2 Energy curve of mine earthquake in Laohutaithe interior structure of mine earthquake, it representscoal mine(ML≥1.0,1988.1-20009)the ratio of frequency of earthquakes of different scalesin certain area. b-value has the relationship withBy using the adjusted energy statistical data a- regional stress state and crustal fracture intensitybove(Table 2), the horizontal axis represents timecorresponding with“b"- value.“b”-vluevertical axis represents creep E( units of J),the中国煤化工( increased in thetrain energy creep curve of mine earthquake is doCNMHG""-yalue rises a-scribed( Fig 3). It reflects that the strain creep curve gain after big earthquake( increased in the proportionStudy on mine earthquake activity rules for Laohutai coal mine in Fushun of Liaoning105of smaller eventsa4.9321M3.9(6)According to available statistics of Fushun Lao-b2646hutai coal mine earthquake, earthquake data magniThe future possible largest mine earthquake mag-tude(0. 1 as stage)from 1995 to 2003 was selected nitude inferred in Fushun Laohutai coal mine is 3.9to the gradient statistics( Table 3)Mining methods of Laohutai coal mine should be optimized to reduce the mine earthquake disasterTable 3 Magnitude-frequency statistics of mine earthquake in Laohutai coal mine( 1995-2003)onclusionsude1.41.51.61.7l.81.92.02(1)Small-level mine earthquake is in the major-frequeney10490789358345339725595ity. Earthquake magnitude between 1.0 and 2. 0 inMagnitude222.3242.52.6272.82.9Laohutai coal mine is in the dominant position, andthe ratio is up to 87. 86%Magnitude3.03.13.23.33.43.53.63.7(2) By using least squares linear regression2313156521method, the relational expression of frequencymagnitude of mine earthquake in Laohutai coal mineStatistical results were fittedis given. It is considered that correlation between fre-squares linear regression methodquency and magnitude is large, and provided the the-4 is M,>l 4 mine earthquake magnitudeoretical basis for further study of the level of miningfrequency distribution and linear fitting results in Lao-and energy releasehutai coal mine during 1988-2000. It shows that th(3) By using"b-value method to predict theactual distribution is consistent with the linear regres- largest mine earthquake in Fushun in future, Levelsion. And the correlation coefficient(R) accounts to3.9 may occur some time to come Therefore mining0.981 122, which is close to 99%. Magnitude-fremethods of Laohutai coal mine should be optimized toquency distribution fitted in Laohutai coal mine is as reduce the mine earthquake disasteollowingReferencesR=0. 981 122 has been calculated, so the actu- Pan Y S. 2003. Study on initiation and failure propagational distribution is consistent with the linear fitting re-rockburst. Beijing Institute of Geology, China EarthquakeMan C H. 2006. Rockburst disasters in coal mine. Global Ge-ology,9(2):121-123b-12646R=0981122Zhang C. 1996. The basis of seismic analysis. Beijing: Seismo-logical Press. 30-50. ( in Chinese)LiY J, Zhang X D, Yuan S, et aL. 2004. Study of FushunLaohutai mineral earthquake activity trend. China MiningMagazine, 13(11): 64-66.(in Chinese with English abLiu DY, Song J C, Wang E D. 2007. Formation mechanismagnitude/Mzof rockbursts in Fushun Coal Mine based on double-rocksample model. Journal of Geological Hazards and Environ-Fig 4 Mine earthquake magnitude-frequency distribument Preservation, 18(2): 10-14. in Chinese with Engtion and linear fitting resultsBy taking N=l in to the formula (5), and getRen x中国煤化工ty research of mineCNMH Gake in Fuxin.Metalting the only largest mine earthquake, we canMine, 2: 141-144. ( in Chinese with English abstractlargest earthquake magnitude