Macroseismic Magnitude Evaluation of Earthquakes of Calabria and Northeastern Sicily (Southern Italy)

A comparison of the most used magnitude-intensity relations is carried out, with reference to a spatial window coinciding with Calabria and northeastern Sicily, evaluating their consistency with different data sets taken from several catalogues. M values indicated in the catalogues and the corresponding average value have been used choosing the relation to be adopted on the basis of the level of their adaptability to points, rather than prearranged models.     

Calibration Functions of Local Magnitude ML in China

On the basis of the local magnitude scale for earthquakes in China and using the data observed by main regional networks in China from 1985 to 1986,the regional calibration functions RLE(△)(suitable for Eastern China)and RLW(△)(suitable for Western China)are established through the statistic analysis of magnitude residuals and study of the average attenuation shape of the maximal phase of near shocks,and the regions in which they apply are defined.For Eastern China,For Western China,     

山西台网新国家标准震级标度与传统震级标度测定地方性震级的对比分析

选用2018年山西数字地震台网的观测资料,分别对新国家标准震级标度与传统震级标度测定的地方性震级进行了对比分析。结果表明,新国标ML震级与传统ML震级一致性较高,震级偏差在0.1之内。新国家标准震级标度很好地继承和衔接了传统震级标度,使用分区量规函数测定的ML单台震级偏差和平均标准偏差值均较小,新震级标度测定的近震震级更加准确。     

F子夜均值逐日差空间异常变化与地震的关系研究

利用2010年1月1日至2014年4月30日我国地磁台网100多个台站的地磁总强度F子夜均值数据,逐一分析了F子夜均值逐日差的空间变化趋势。结果表明,在此期间有18次小区域的异常变化,其中16次异常与其后几天到半年时间内该区域发生的地震有很好的对应关系,另外两次新近的异常有待后续进一步验证。我国西北部地区地磁台站稀疏,布局不合理,限制了对新疆、青海、西藏等地震多发区震磁关系的研究,建议这些地区进一步加密台站建设,优化布局。     

A Magnitude-Felt Area Relation in the Evaluation of the Magnitude of Historical Earthquakes

An evaluation of the magnitude of historical earthquakes is proposed, through an empirical relation based on a felt area of historical earthquakes derived from a vectorial modelling of macroseismic intensity distribution.     

云南中小地震矩震级的测定

利用云南省测震台网的数字地震波形资料,反演了2008年1月至2012年9月675个中小地震的震源波谱参数,并计算了这些地震的地震矩M0和矩震级Mw,最后利用回归分析方法得到了近震震级ML和Mw之间的关系式.     

震级转换关系及其对地震活动性参数的影响研究

本文根据1990-2007年《中国地震年报》中同时给出Ms和ML、且震源深度〈70km的6577个浅源地震资料,经统计回归得到了全国和各地震区Ms与ML之间的经验关系。新的震级转换关系接近于Ms=ML,本文建议在需要进行震级标度转换时,对于没有测定Ms的低震级地震可直接使用Ms=ML进行转换。与目前广泛使用的震级转换关系相比,采用本文建议的震级转换方法后,全国各地震区5级以上地震的数量基本没有变化,但5级以下地震的数量有明显增加,导致由此统计得到的各地震区震级．频度关系中的b值有不同程度的增大。此外,用地震数量直接得到的4级以上地震的年平均发生率V4有明显增高,且部分地震区甚至增加了50％以上。在高震级地震发生率不变的情况下,地震活动性参数的上述变化反映了对地震区地震活动水平的估计有提高,可能导致概率地震危险性分析结果的提高,对地震区划和工程场地地震安全性评价有重要意义。     

Determination of Scenario Earthquakes for Zigong City

Ujsing deterministic methods in combination with probabilistic methods,the authors havestudied in detail the seismogeological background,seismogfnic faults and their abilities ingenerating earthquakes,the temporal and spatial distribution features of seismicity;predicted the seismicity tendency in future 50 years;and studied the expected magnitude andexpected distance of destructive earthquakes that may attack Zigong City.On such a basis,2scenario earthquakes have been determined for Zigong City.The results would be helphl forthe lecal government and authorities to work out a great earthquake emergency pre-plan andto estaplish the great earthquake fast-response system.     

The Local Magnitude Scale in the Korean Peninsula

A formula to determine the local magnitude (M_L) following Richters original definition was empirically derived for the Korean Peninsula. A total of 1,644 digital seismograms from 142 Korean earthquakes that occurred from 1997 to 2000 were corrected for instrument response and convolved with the nominal Wood-Anderson torsion seismograph response to be appropriate for the original definition of M_L. Then, the zero-to-peak amplitude was measured in millimeters on the synthetic Wood-Anderson seismogram. Multiple regression analysis was conducted to determine distance and station correction terms for the measured peak amplitudes. The best-fit solution for M_L yielded the following formula for the Korean Peninsula:where A() and S denote the peak amplitude on the synthetic Wood-Anderson seismogram at distance and the station correction term, respectively. Note that the second term, distance correction, was adjusted with Richters M_L, taking into consideration attenuation differences between the Korean Peninsula and southern California, where Richter originally introduced M_L. On average, the magnitudes determined in this study are nearly the same as those determined by the Korea Institute of Geoscience and Mineral Resources (KIGAM), but are larger than those of the Korea Meteorological Administration (KMA) by as much as 0.36.     

Lateral variations of the local magnitude at Ebre station,Northeastern Iberian Peninsula

Since 1984, a seismic surveillance at the Baix Ebre Region (NE of the Iberian Peninsula) has been carried out from a seismic network consisting of two digital and one analog stations. Large discrepancies between the recorded amplitudes and the magnitude estimates given by different agencies have been observed. To explain these discrepancies, that consist of a large reduction of amplitude and a strong dependence of the azimuth, a local magnitude formula for the area has been computed, using the analog records obtained at EBR short-period station. Global results show an average station correction factor between the computed local magnitude and the reported magnitude of the order of 1, presenting large variations around the mean value with a clear dependence on the azimuth. A detailed analysis of this variation around the mean value reveals that earthquakes can be classified according to their location in different geological units, thus obtaining for each zone a distinct station correction factor that can fluctuate as much as 0.6 around the average. These large lateral variations of the magnitude are in good agreement with previous studies of coda-Q attenuation.     

震级新国标实施前后中强浅源地震速报震级差异的分析对比

目前震级新国标拟在中国地震震级测定中开始使用。 为系统评估震级新国标对中强浅源地震的速报震级影响, 基于2001—2017年中国大陆发布的5级以上浅源地震速报目录, 本文系统分析了新国标宽频带面波震级与原速报震级的差异, 并与国外面波震级结果以及国、 内外矩震级的结果进行了对比研究。 结果表明: 采用新国标, 国内、 外面波震级对6级以上地震测定结果基本一致, 但5、 6级以上地震的频次分别为原来的80%、 60%左右, 而6.5级以上地震频次差异不大。 国内、 外矩震级测定结果比较一致, 由于国际上目前采用矩震级发布, 而矩震级与面波震级之间存在系统偏差, 因此, 为保持与国际结果一致, 应加快矩震级在地震速报中的应用, 这可能会导致6、 7级地震频次进一步降低。 由于速报震级在实际工作中既有可能采用面波震级, 也有可能采用矩震级, 或两者的结合; 因此, 速报震级仅用于地震信息发布、 地震应急、 科普宣传等社会应用, 如果使用震级进行科学研究、 地震活动性统计等专业应用研究, 最好统一使用一种标度, 即面波震级或矩震级。     

河北省测震台网中小地震矩震级的测定

利用河北省测震台网的数字地震波形资料,反演了2008年12月至2010年4月62个中小地震的震源波谱参数,计算了这些地震的地震矩M0和矩震级Mw,利用正交回归分析方法得到了近震体波震级ML和Mw之间的关系式.     

Enhancement of Seismicity Recorded by the Qiaojia Array before the 2013 Lushan and 2014 Ludian Earthquakes

A seismic array of twenty four seismometers(Qiaojia array) operated by the Institute of Geophysics,China Earthquake Administration was situated along the Zemuhe fault and the north end of Xiaojiang fault,which is a part of the east boundary of the Chuan-Dian( Sichuan-Yunnan) rhombus crustal mass. The Qiaojia array started operation at the end of February,2012. Since then the April 20,2013 Lushan MS7. 0 earthquake and the August 3,2014 Ludian MS6. 5 earthquake have occurred in the vicinity of the Qiaojia array. The earthquake catalogue recorded by the Qiaojia array since March,2012 is used in this study. The temporal variation of the earthquake count before the Lushan event and the Ludian event is analyzed. The results are as follows:(1) A very clear gradually increasing variation of the count of M ≥ 2. 0 earthquakes within the region,where all earthquakes recorded by the Qiaojia array coverage can be found before the Lushan event and the Ludian event,and the increasing range and duration of the count before the Ludian event are both larger than those before the Lushan event.(2) In the region covered by the Qiaojia array,for earthquakes with depth h ≤10 km a rising process of the count was manifested before both events,along with a nearly same duration of about five and a half months,and for earthquakes with depths h 10 km a rising-dropping process of the count was manifest before the Lushan event,before which the rising-dropping process appeared again. The variation of the count for earthquakes with depth h ≤ 10 km is the reverse of that for earthquakes with depth h 10 km.(3) Within and near the region covered by the Qiaojia array,the variation of the count manifests a rising process for earthquakes with depth h ≤ 10 km or h 10 km before the Lushan event and only for earthquakes with depth h ≤ 10 km before the Ludian event. The variation of the count manifests a weakening process for earthquakes with depth h 10 km before the Lushan event. It is shown from the above results that the seismicity within and near the regioncovered by the Qiaojia array showed a steeply rising change before both the Lushan event and the Ludian event. This phenomenon could be revelatory to understanding the process of seismicity development.     

MDCB-5型临震信息监测仪模拟未来震级大小计算初探

根据MDCB－5型临震信息监测仪记录到的某一地震临震异常幅度（电压值）、持续时间（天数）与岩石破裂、地震发生、地震波能量释放的相关性，从地震发生的物理基础出发，推导出了2个计算未来震级大小的理论公式。使用44天的监测数据对该期间发生的5次6级以上地震的震级进行了计算，在相应的震中距范围内计算的震级与实际发生的震级误差小于0．5级，初步说明了该方法应用于实际地震预报具有一定的参考价值。     

Study on the Moment Magnitude of Small and Moderate Earthquakes Located in the Inner Mongolia Region

Based on digital seismic waveform data from Inner Mongolia Digital Seismic Network, the source spectrum parameters of 182 small and moderate earthquakes from January, 2009 to September, 2016 are derived, and the seismic moment M₀ and moment magnitude M_W of the earthquakes are calculated. The M_L-M_W relationship and the relationship between stress drop and magnitude are obtained using the linear regression method. It is clear that incorporating the moment magnitude into the seismic quick report catalog and the official earthquake catalog can enrich earthquake observation report content, thus providing better service for earthquake emergency and earthquake scientific research.     

Seismic Spatial Distribution Factor ZK and the Features of Its Variation around Moderately Strong Earthquakes

This paper has introduced the spatial distance method to analyze the distribution features of earthquakes quantitatively.The seismic distribution factor ZK defined in this paper can be used to identify the type of seismic spatial distribution better.The spatial distribution of earthquakes features a clustered pattern when the Zg-value approaches to 1; it is stochastic when ZK fluctuates around 0.5; and it may have a network pattern when ZK approaches to 0.From the angle of seismic spatial distribution,the change of the Rvalue reflects to some extent the dynamic variation of the degree of order and complexity of the seismogenic system.Taking 10 earthquakes of Ms≥5.8 in North China since 1970 as an example,the paper has discussed the variation features of ZK around moderately strong earthquakes.Results show that high Rvalue anomalies can generally be detected before moderately strong events.The Zk value of 0.642 can be taken as a criterion for identifying anomalies.Before the 2 strong earthquakes of Ms≥     

中国大陆7级大地震强余震震级和空间分布特征

本文研究了中国大陆1966年以来15次7.0～7.9级地震序列强余震空间分布和震级分布特征。 研究结果表明: ① 强余震与主震震级差(ΔM)与频度(N)的统计关系服从指数分布, 统计得到了全部序列平均B值为0.72, 12个走滑型地震序列平均B值为0.73; ② 走滑型地震序列强余震优势分布范围是5~59 km, 非走滑型序列优势分布为10~29 km, 并且强余震与主震震中距离服从正态分布。     

The Conversion Relationship between the Local Earthquake Magnitude and Surface Wave Magnitude in the Inner Mongolia Digital Seismic Network

Using 116 earthquakes over M_L3.8 in the Inner Mongolia region from 2008 to 2015, the local earthquake magnitude M_L and surface wave magnitude M_S are remeasured. Based on norm linear regression(SR1 and SR2) and norm(OR) orthogonal regression method, we established the conversion relationship between M_L and M_S. The results were tested with Gaussian disturbance. The result shows that the orthogonal regression method(OR) result has the best fitting curve, and the conversion relation is M_S=0.96 M_L-0.10. The difference between our result and Guo Lücan's(M_S=1.13 M_L-1.08) may be caused by regional tectonic characteristics. M_(S Inner Mongolia) value is significantly higher than the M_(S empirical) value, with an average difference of 0.23, the difference distribution of empirical relation and the rectified relation is in the range of 0.2-0.3.     

江苏及邻区地方性震级量规函数的研究

基于2009～2018年江苏及相邻数字地震台网记录的2602次地震事件观测资料,通过震级残差统计方法得到了72个台站的单台震级与台网平均震级的偏差、平均偏差和标准偏差,分析了震级偏差频次分布和定量统计结果,进而修正了江苏及邻区的地方性震级量规函数。实际地方性震级测定结果表明,使用校正后的量规函数比新震级国家标准(GB17740—2017)中量规函数所测定的震级的标准差更小,且单台震级残差相对更集中于0,这说明该量规函数有助于提高江苏及邻区地方性震级测定精度。     

使用P波快速测定国家台网大震标准震级

本文针对国家台网速报面波震级测定时间偏长和中深源地震震级速报有一定偏差的问题,采用IASPEI推荐的宽频带体波震级mB及宽频带P波矩震级MWP对2009—2013年国家台网地震速报的大震进行了对比分析。对于经过转换成MW后的mB和MWP震级来说,其结果均与我国速报地震发布的震级M有一定的偏差,一般表现为偏小。其中,对于6.0—6.9级地震,mB偏差相对较小,但离散度相对较大(整体偏差要比平均偏差大不少);对于7.0—7.9级地震,MWP偏差相对较小;而对于8.0级以上地震,由于震级饱和等原因,mB偏差较大,但MWP偏差相对较小,一般主要表现为偏小。总体来说,MW(MWP)的稳定性要比MW(mB)更好一些(线性回归的相关系数更大,标准误差更小)。对于综合mB和MWP震级来说,由于采取分段平均的方法,结果的稳定性有了一定的提高,但较大地震仍以偏小为主,如果在综合震级MP上加0.2,则可以得出与M震级较为接近的结果。通过MW(mB)、MW(MWP)、MP(M)、M与MW(GCMT)的对比,可以验证综合标准震级MP(M)和国家台网速报震级M具备一定的可信度,而MP(M)可作为P波快速测定的震级,所以用MP(M)作为大震速报初报震级,在某种程度上是可行的。