INTRODUCTION

Obtaining accurate and reliable seismic positioning results is the key to earthquake prediction and seismic cataloging of the Regional Digital Seismic Network，and is also an important basis for earthquake prediction and seismology research.The crust velocity model is closely related to the location precision of earthquakes （Zhao Zhonghe， 2010）， and a proper earth's crust velocity model can help seismologists accurately judge earthquake measuring accuracy（Zhu Yuanqing et al.， 1997； Zhang Tianzhong et al.， 2007）， therefore， the role of the earth's crust velocity model becomes more prominent（Zhu Yuanqing et al.， 1990）.Accurately determining the longitude and latitude of the epicenter and focal depth of an earthquake has always been of concern to seismology research （Zhu Yuanqing et al.， 1997）.

In the complex geological western region of Inner Mongolia（36°-46°N，96°-115°E）， the east-west fold-fault structure and two major NE-and NW-trending fault zones are distributed.In the uplift zones， differential activity is not obvious， earthquake activity is weak， and there is no strong earthquake activity.The Hetao rift belt is located between the Yinshan uplift and Ordos uplift zone and borders the Langshan piedmont fault in the west， the Horinger fault in the east，the Seerteng Mountain，Wula Mountain Daqingshan piedmont faults in the north，and the northern marginal faults of Ordos in the south.Moderate strong earthquakes often occurred in the junctions between the major boundary faults and the secondary transverse faults.

Li Xiang et al.（1987） used the fitting method of the seismic waves of distant earthquakes to obtain the crustal thickness of Inner Mongolia，which is 46km to 54km.Using the seismic refraction sounding method， Liu Changquan et al. （1991） determined the velocity structure of the crust in the Ordos block， Hohhot-Baotou basin， Yinshan block and the fold belt in Inner Mongolia and other regions.The results show that the crust in the western Inner Mongolia has obvious layering characteristics， and the crustal thickness is 43km-48km.Zhang Hongdshuan et al. （2010） used the method of receiving functions to determine the crust thickness beneath 7 stations in the Hohhot-Baotou basin，and the results revealed a crust thickness of 42km to 46km.

The current general model used by the Inner Mongolia Digital Seismic Network is not consistent with the actual geological structure in western Inner Mongolia，the location residual is large， and the theoretical arrival is not consistent with the actual arrival time， which brings great confusion to earthquake monitoring， earthquake prediction and emergency rescue work.Therefore，the establishment of a crustal velocity model that conforms to the geological characteristics of the western region of Inner Mongolia is urgent.Using the observation data from the Digital Seismic Network of Inner Mongolia to determine and amend the existing velocity models（the South China model， and the 2015 optimal model of Inner Mongolia）， the results can be applied to seismic network observation practice，thus improving the quality of earthquake location.The seismic stations in western Inner Mongolia are relatively dense，and a certain number of earthquakes have been recorded， which provides data for seismological research.In this paper， the two-layered velocity structure of the crust in the western region of Inner Mongolia is inverted by using the observed seismic travel time data from the Inner Mongolia Digital Seismic Network.

1 DATA SELECTION

Two types of data are selected for the establishment and inspection of the new model in western Inner Mongolia.

①The seismic data used to establish the western Inner Mongolia velocity model：

We select the records of 225 ML≥3.0 earthquake events that occurred in western Inner Mongolia recorded by the Digital Seismic Network of Inner Mongolia from 2009 to April 2016 and use the Pn and Pg combined focal depth determination method （Zhu Yuanqing et al.， 1997） to re-measure the focal depths.Fig.1 shows the radiographic map of the selected earthquake and station.

②The seismic data used to test the eastern Inner Mongolia model.

The earthquakes occurring in eastern Inner Mongolia recorded by the Inner Mongolia Digital Seismic Network are selected by random to test the new model.

③Blasting data used to test the eastern Inner Mongolia model.

以小组为单位，按照老师下发的任务书（涵盖要完成的任务、制作要求、产品相关信息点、评分标准、学习反馈表），共同制作产品说明书。老师事前根据组员的情况布置相应产品给予制作（如女生较多的组，教师可选用化妆品、零食等学生感兴趣的物品；男生较多的组，教师可选用电器等物品布置任务。此任务也可以由学生自己设定），完成以后，组内进行修改，然后组与组之间派代表进行互改，并展示成果。最后每位同学完成学习反馈表，用于检查教学效果。

Fig.1 Distribution of earthquakes，seismic ray paths and stations

2 PRINCIPLES AND METHODS

The continental crust is relatively thick，with an average of about 35km，and the mountain and plateau region can reach 70km.The continental crust can be divided into the granite layer and basalt layer in terms of chemical composition.It is reasonable to pick up the existence of the Conrad surface from a large number of Pb seismic phases in the seismic records collected in this study.

由表2、表3可知，药后30 d，各药剂处理小区内杂草株防效相对于药后15 d整体略有降低，可能是由试验小区内新增杂草较多所导致。1%甲基二磺隆·双氟磺草胺可分散油悬浮剂各剂量处理对雀麦、播娘蒿、荠菜的株防效、鲜质量防效均在80%以上，总体防除效果较好；单剂30 g/L甲基二磺隆可分散油悬浮剂对雀麦的株防效、鲜质量防效仍高于90%，对播娘蒿、荠菜的防效略差；单剂50 g/L双氟磺草胺悬浮剂对播娘蒿、荠菜的株防效、鲜质量防效仍高于90%，但由于对雀麦无效，总体防效较差。

Assuming that the crustal structure has two layers，seismic waves within the layer have a uniform speed，the velocity on Conrad discontinuity is the same as that of the lower crust.The velocity model contains five parameters， the upper crust velocity V1（VPg）， lower crust velocity V2（VPb）， the velocity along the Moho surface Vn（VPn）， upper crust thickness H1and lower crust thickness H2.Fig.2 shows the longitudinal wave propagation path.

Fig.2 Sketch of P waves propagation paths

The focal depth ranges from 0km to 21km，and the upper crust thickness of the study area is about 25km，so it can be assumed that the earthquakes all occur in the upper crust.In the case of limited data， in order to avoid the correlation effect between parameters， multiple parameters are not used in the joint inversion，and each parameter is determined step by step.The travel time of direct wave Pg can determine the upper crust P-wave velocity；the lower crust velocity is determined by the travel time of Conrad surface refraction wave Pb，and the upper crust thickness，the total crust thickness and the wave velocity along the Moho discontinuity are inverted by the travel time of first wave Pn.

Blasting data important for checking the location accuracy，and the blasting in eastern Inner Mongolia Region recorded by the Inner Mongolia Digital Seismic Network is randomly selected to test the new model.

至于孟子，他认为：“吾今而后知杀人亲之重也：杀人之父，人亦杀其父；杀人之兄，人亦杀其兄。然则非自杀之也，一间耳。”[4](P366)无论是出于“重孝”或是“重仁”的主张[5]，其最基本前提便是对于个体生命的珍视与尊重，因而他是坚定的武德论者，重视“德”对“武”的规约，而与纵横家、法家等相对抗。

The adjustment principle is： （1） seismic data dispersion adjustment： deleting the observed seismic phase data that has a 4s deviation from the theoretical line； （2） depth adjustment： The depth is adjusted so that the actual seismic data is located in the middle of the theoretical line；（3） velocity adjustment： The actual data should be parallel to the theoretical line.

3 THE ESTABLISHMENT OF THE INITIAL MODEL AND THE OPTIMAL MODEL

3.1 Initial Model

The initial model of the western region was determined by means of velocity fitting，subregional scanning，and the method of determining the thickness and velocity of the crust through reduced travel time.

3.1.2 The Thickness and Velocity of the Crust Determined by Reduced Travel Time

1.3.1 对照组采用的呼吸道管理措施:①呼吸机:反复使用的呼吸机管路及呼吸机湿化罐，每周更换。②使用开放式吸痰法，2人协同操作，常规先用生理盐水进行吸痰前的湿化，然后1人专管吸引，另1人接复苏囊加压给氧，吸痰频次每2～3小时1次［3］。③体位:患儿床头抬高15°。④口腔护理:对患儿进行口腔护理每12小时1次。

In the western region of Inner Mongolia （36°-46°N， 96°-115°E）， 225 ML≥3.0 earthquakes（station number： N≥8） are selected.From the selected seismic events， we extracted a total of 2，467 items of Pg data， 810 of Pndata， 89 of Pb data， and 3516 of Sg data.By seismic phase velocity fitting of Pn， Pb， Pg and Sg， we get the fitting curves of VPg， VPb， VPnand VSg， as shown in Fig.3.

3.1.1 Subdivision Scanning

In order to investigate the stability of the seismic velocity wave，sub-regional scanning was performed over the western Inner Mongolia with the step length set according to the frequency of earthquakes，and then the velocity mean was obtained.The specific results are shown in Table 1.

Based on existing research on the Inner Mongolia regional crustal velocity model，the seismic phases velocity fitting curve and reduced travel time curve，and the results of Hyposat batch processing， reasonable adjustments have been made on the five parameters， namely， the upper crust velocity V1（VPg）， the lower crust velocity V2（VPb）， the velocity along the Moho V3（VPn），the upper crust thickness H1and the lower crust thickness H2， to establish the initial model，then，the final optimal crustal velocity model for the western region of Inner Mongolia was established.

Table 1 Sub-regional scanning results

Longitude／（°E）Latitude／（°N） Earthquakes Pg Pn Pb Sg VPg／（km／s） VPn／（km／s） VPb／（km／s） VSg／（km／s）96-115 36-46 225 3467 81089 3516 6.15 8.10 6.61 3.60 96-102 36-46 29 399 17153 401 6.04 8.41 6.58 3.57 98-104 36-46 69 974 25367 979 6.04 8.37 6.63 3.58 100-106 36-46 111 1602 406 58 1612 6.07 8.19 6.57 3.59 102-107 36-46 137 2170 443 51 2186 6.12 8.08 6.58 3.61 104-108 36-46 104 1709 409 80 1730 6.13 8.06 6.64 3.61 105-109 36-46 82 1367 34962 1383 6.15 8.03 6.63 3.62 106-110 36-46 69 1162 30057 1177 6.15 8.05 6.61 3.62 107-111 36-46 24 338 122 40 347 6.15 8.28 6.58 3.60 108-114 36-46 46 681 130 48 688 6.18 8.10 6.65 3.61 109-115 36-46 49 756 125 61 781 6.15 8.11 6.61 3.60 Average 6.12 8.17 6.61 3.60

2016年，国家机关事务管理局、国家发展和改革委员共同印发《公共机构节约能源资源“十三五”规划》，该《规划》指出：与2015年相较，2020年全国公共机构人均综合能耗应下降11%、单位建筑面积能耗应下降10%、人均用水量应下降15%，明确了医院节能的硬指标与管理目标。此外，随着公立医院改革工作的深入推进，医院经济运营面临压力。精益管理成为确保医院经济运营的必由之路，节能管理被提上重要高度。

2.2 抗性鉴定结果 2015、2016年全国芝麻品种区域试验抗性鉴定结果见表2。2015年茎点枯病发病率和病情指数分别为10.85%和5.79，枯萎病发病率和病情指数分别为2.13%和0.91；2016年茎点枯病发病率和病情指数分别为6.35%和4.34，枯萎病发病率和病情指数分别为1.65%和0.78；两年茎点枯病发病率和病情指数分别为8.60%和5.07，枯萎病发病率和病情指数分别为1.89%和0.85，抗芝麻茎点枯病和芝麻枯萎病，属抗性较强芝麻品种。

1.3.4 投资来源渠道窄，依赖贷款不能变。按照财发〔2015〕26号、30号文件精神，“创投”项目资金来源于资本金和银行贷款，不能贷款就不能立项，导致项目投资来源渠道单一，过度依赖金融机构贷款。全市实际落地项目占比仅29.17%。

Where， TZis the reduced travel time， TLis the theoretical travel time， Δ is the epicentral distance，and V is the wave velocity.

Based on the South China crustal velocity model， using formula （1）， we get reduced the P-wave travel time curve of the 225（N≥8）ML≥3.0 earthquakes.As seen from Fig.4（a） and 4（b）， Pg and Pn phase values are above the theoretical line， indicating that the Moho depth determined by the South China and Inner Mongolia optimal 2015 model is shallower，the distribution of VPgand VPnseismic phase is close to the theoretical line.Accordingly，we made the adjustment as follows： The first adjustment： （1） Moho depth adjustment， increasing the Moho surface depth to 46km （H1＝27km，H2＝19km）； （2） velocity fine tuning， increasing V1from 6.12km／s to 6.15km／s， with an increase of 0.03km／s.The second adjustment： （1） Moho depth adjustment， increasing Moho surface depth to 46km （H1＝32km，H2＝14km）； （2）velocity adjustment， decreasing V1to 6.07km／s from 6.12km／s， with a decrease of 0.05km／s.Finally， the actual data is in the middle of the theoretical line， and the overall distribution trend of the data is parallel to the theoretical line （Fig.4（c）， （d））.

Based on the mean velocity of Pg， Pb and Pn， the reduced travel time is calculated as：

The initial model of the one-dimensional velocity in the western region of Inner Mongolia is obtained by the combined seismic velocity fitting curve and the reduced travel time curve.

Table 2 Initial model

Crust layer P-wave velocity（km／s） Disturbance range Thickness（km） Disturbance range 1 6.07 6.0-6.3 32 24-36 2 6.61 6.5-6.7 14 3 8.17 7.9-8.3 36-48

3.2 The Optimal Model for Western Inner Mongolia

Selecting 225 earthquakes of ML≥3.0 recorded by the Digital Seismic Network of Inner Mongolia，using the initial model and setting up several models with different values within the scope of its disturbance of the initial model， and adopting the Hyposat batch processing method，two searches and positionings were conducted （Table 3）.The minimum average residual error of the first search is RMS＝0.476，the minimum average residual error of the second search is RMS＝0.463.Accordingly， we can determine the optimal model of the western Inner Mongolia by the Hyposat batch processing method， that is： V1＝ 6.06km／s， VPb＝ 6.61km／s， Vn＝ 8.12km／s，H1＝30m，and the Moho depth H＝44km.In the same way，the average residual is RMS＝1.307 using the South China model batch processing and RMS＝0.961 by the optimal model of Inner Mongolia，2015.

Combining the previous research results，the seismic phase fitting curves of earthquakes in western Inner Mongolia and the reduced traveltime curve，we get the initial crustal velocity model of western Inner Mongolia and the optimal velocity model by Hyposat batch processing，and in combination with regional geological tectonic characteristics in the western area of Inner Mongolia，the western Inner Mongolia model is established as： V1 ＝ 6.06km／s， VPb＝ 6.61km／s， Vn＝8.12km／s， H1＝30km， H2＝14km.

Fig.3 Velocities fitting of 225 earthquakes in western Inner Mongolia

Fig.4 Reduced travel time curve of P-wave

（a） Mean value from South China model； （b） mean value from the optimal model of Inner Mongolia，2015； （c） reduced curve by the first adjustment； （d） reduced curve by the second adjustment

Table 3 Two search results of Hyposat batch processing

Number／search content V1（km／s） VPb（km／s） Vn（km／s） H1（km） Moho depth（km）Average residual（RMS）1 Step length Search range 1 1 36-48 Result Step length 0.1 6.00-6.30 0.1 6.50-6.70 0.1 7.90-8.3024-36 6.1 0.01 6.6 0.01 8.1 0.01 32 1 45 1 0.476 2 Search range 6.05-6.20 6.55-6.70 8.00-8.15 29-35 40-49 Result 6.06 6.61 8.12 30 44 0.463 3 4 Model 2015 optimal model 6.01 6.10 6.88 6.60 7.98 8.05 21 24 33 41 1.307 0.961

A comparative analysis of location residuals and epicentral positioning deviation（epicentral deviation）was made among the three models.

4 TEST OF THE WESTERN INNER MONGOLIA MODELS BY HYPOSAT BATCH PROCESSING

Choosing randomly 88 earthquakes recorded by the Digital Seismic Network in Inner Mongolia， using the seismic velocity model of South China （catalog）， in 2015 the optimal model and the western Inner Mongolia model，we adopt Hyposat batch positioning software to do the batch processing on the seismic data and get the earthquake parameters such as epicenter location， magnitude， focal depth and the original time， as well as the residuals.

The comparison between the western model and the best model of Inner Mongolia of 2015 and the South China model shows that： （1） V1， VPband Vnare not much different from each other in the three models； （2） the difference in crustal thickness is small between the western model and the optimal model， but both are larger than the South China model（Fig.5）.

4.1 Analysis of Location Residuals

By using the western model， the South China （catalog） model and the optimal model in 2015 to the location，comparison chart of location residual was obtained.From Fig.6，we can see catalog positioning residual of the 88 earthquakes ranges between 0.077-5.231 seconds，the average being 0.707 seconds.The location residual by the 2015 optimal model is in the range of 0.059-5.248 seconds，with a mean value of 0.634 seconds.The residual range by the western model is 0.055-1.424 seconds and the mean value is 0.382 seconds.The mean residual of the western model is significantly reduced.

但对谢清森来说，并没有满足，他的心思早已漂洋过海。“让中国保安为世界做安保。”这是他一直以来的一个心愿。

4.2 The Test and Analysis of Epicenter Deviation

Fig.7 shows the epicenter deviation contrast of 88 earthquakes between the“Western Model-Catalog”， the“Optimal Model-Catalog”and the“South China Model-Catalog”.In this figure， the epicenter deviation in the“Western Model-Catalog”is between 0.165-18.204km， with an average of 2.902km，and there is one earthquake with epicenter deviation ＞ 10km；The epicenter deviation in the“Optimal Model Catalog 2015”is between 0.139 and 18.204km， with a mean of 3.207km，and there are 4 earthquakes with epicenter deviation ＞10km.The epicenter deviation in the“South China Model-Catalog”is between 0.209-79.395km， with a mean of 5.487km， and there are 10 earthquakes with an epicenter deviation＞10km.

Fig.5 Comparison of models

Fig.6 Comparison of location residuals between the western， optimal（2015），and cataloging（South China） models

Fig.7 Comparison of epicenter deviation between“Western Inner Mongolia Model-Catalog，“Optimal Model-Catalog” and “the South China Model-Catalog”

4.3 Random Earthquake Sampling to Check the Reduced Travel Time （Fig.8）

Fig.8 shows that the actual data is in the middle of the theoretical line，and the overall distribution trend of the data is parallel to the theoretical line.The western model reasonably and effectively reflects the crust velocity structure of western Inner Mongolia.

Fig.8 Reduced travel time of P-wave

4.4 Random Earthquake Sampling for Focal Depth Check （Fig.9）

We determined the focal depths of the randomly sampled earthquakes using the western model， the Hyposat and PTD method， respectively， and the results show that the depths determined by PTD method are all below 20km，suggesting the western model is reasonable and stable.

灰色系统理论提出对各系统进行灰色关联度分析的概念，灰色关联度是以因素之间发展趋势的相似或相异程度作为衡量各系统因素关联程度的一种方法。通过灰色关联度分析，认为两个系统因素变化的态势是一致的，即同步变化程度较高，则两者关联度较大；反之，则两者关联度较小。分析步骤如下：

Fig.9 Comparison of focal depths determined by different models

5 CONCLUSIONS

Through the analysis of the one-dimensional velocity model of western Inner Mongolia，the following conclusions are drawn：

2.4 敏感性分析 本研究结果的稳定性及稳定程度，通过改变统计方法进行判定，结果发现不同结局指标在改变统计方法后，数据结果差异较小，说明敏感性低，结果较稳健可靠。见表4。

（1） Through linear fitting of seismic phases and reduced travel time curve of 225 ML≥3.0 earthquakes occurring in the region， and using the methods of discrete degree adjustment， depth，and velocity adjustment the initial model was obtained.Then using the initial model to search for the secondary Hyposat batch location results of 225 earthquakes，the western Inner Mongolia velocity model was obtained， that is， V1＝6.06km／s， VPb＝6.61km／s， Vn＝8.12km／s， H1＝30m，and Moho depth H＝44km.

（2） The Hyposat location algorithm was used to test the results， the travel time residuals were significantly reduced，the epicenter deviation in earthquake location was decreased to some extent， and the deviation range was reasonable and stable， so the western model improves the accuracy of earthquake location.

（3） The located focal depth is reasonable， and the new model improves the location quality.

（4） The Hyposat method is sensitive to the velocity model， and the location results of different velocity models are different.

（5） The two-layer uniform velocity model in western Inner Mongolia is in line with the actual crustal structure in the western region of Inner Mongolia，which is suitable for earthquake location in the Inner Mongolia Digital Seismic Network.

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