Moment magnitudes of two large Turkish earthquakes on February 6,2023 from long-period coda

Two large earthquakes(an earthquake doublet)occurred in south-central Turkey on February 6,2023,causing massive damages and casualties.The magnitudes and the relative sizes of the two mainshocks are essential information for scientific research and public awareness.There are obvious discrepancies among the results that have been reported so far,which may be revised and updated later.Here we applied a novel and reliable long-period coda moment magnitude method to the two large earthquakes.The moment magnitudes(with one standard error)are 7.95±0.013 and 7.86±0.012,respectively,which are larger than all the previous reports.The first mainshock,which matches the largest recorded earthquakes in the Turkish history,is slightly larger than the second one by 0.11±0.035 in magnitude or by 0.04 to 0.18 at 95%confidence level.

A Catalogue of Earthquakes With Moment Magnitude of the Center-Southern Asia Test Area of the Global Seismic Hazard Assessment Program

We compile a regional catalogue of earthquakes with moment magnitude of the Center-Southern Asia test area(20°-35°N,85°-105°E)for the Global Seismic Hazard Assessment Program(GSHAP).There are significant inhomogeneous and uncompleted data,and n uniformity of earthquake magnitudes in this test area because this region is situated on the boundaries of many countries,such as China,India,Nepal,Vietnam,etc.We establish a relationship between Gutenberg surface-wave magnitude and IASPEI surface-wave magnitude,which can be used for conversion of different magnitude scales into moment magnitude for this catalogue.A catalogue of events with Mw≥6.0 of this test area is given at the end of this paper.

On Estimating Magnitude of a Maximum Sequent Earthquake by Viscoelastic Coulomb Stress Change and a Discussion of the Relationship between the M_S7.3 Earthquakes in Yutian 2008 and 2014

On the basis of the previous studies of the layered crustal model in the Yutian area,combined with the field GPS continuous observation data,we roughly estimate the viscous coefficient of each layer. With the viscoelastic horizontal layer model,we calculate the viscoelastic co-seismic Coulomb stress change caused by the Yutian M_S7. 3 earthquakes 2008 and 2014 respectively. Based on the Coulomb stress change,using the calculation method of "direct "aftershock frequency,we come up with the theoretical earthquake frequency directly related to the mainshock and the co-seismic Coulomb stress change in the study area. Then we put forward a method,based on the comparison of theoretical and actual earthquake frequency or the comparison between theoretical and practical earthquake frequency-distance decay curve fitting residuals,to estimate the magnitude of a maximum sequent earthquake,directly related to the mainshock co-seismic Coulomb stress change. Results calculated by different methods show that the maximum follow-up earthquake magnitude caused by the coseismic Coulomb stress change lies from M_S7. 2 to M_S7. 5 following Yutian M_S7. 3 earthquake in 2008; but that of the 2014 Yutian M_S7. 3 earthquake is M_S6. 3. The former is very close to the Yutian M_S7. 3 earthquake in 2014.Because of the same magnitude,relatively close spatial distance,short time interval,the same region of the external force,the strong correlation between two seismic tectonic and a clear stress interaction,we thus consider that the two Yutian M_S7. 3 earthquakes in 2008 and 2014 constitute a pair of generalized double shock type earthquake. This is consistent with the sequence type characteristic of past "double shock"earthquakes in the region. In this paper,the influence of the magnitude lower limit and the b-value in the relationship of G-R on the results is discussed. As a result,when the viscoelastic coseismic Coulomb stress variation is determined,the lower limit of magnitude has little effect on the maximum sequent earthquake magnitude estimation,but b-value of G-R has a greater impact on the results.

Results of Geomagnetic Studies on the Problem of Forecasting Strong Earthquakes in Uzbekistan

The article is devoted to the problem of forecasting strong earthquakes by the geomagnetic method. The geomagnetic method is widely used on this problem in seismically active regions of the world as one of the promising, informative and operational geophysical methods. The results of long-term geomagnetic studies on the problem of forecasting strong earthquakes in Uzbekistan are presented. Geomagnetic studies were carried out on the territories of the Tashkent, Ferghana, and Kyzylkum geodynamic polygons in the epicentral zones of strong earthquakes that occurred. Long-term, medium- and short-term precursors of earthquakes have been identified. Anomalous changes in the geomagnetic field associated with the decline in aftershock activity were also revealed. The dependence between the duration of the manifestation of long-term magnetic precursors and the magnitude of earthquakes is determined. Absolute proton magnetometers MMP-1, MV-01 (Russia), and G-856 (USA) were used to measure the geomagnetic field.

Study on Variation of Fitting Goodness of Relation Between Earthquake Frequency and Magnitude before Moderately Strong Earthquakes (Ms≥5.0)

In this paper,characteristics of spatial and temporal variation of linear fitting goodness before some moderately strong earthquakes(Ms≥5.0)in the eastern part of China(east of longitude 180)are studied according to the famous Gutenberg-Richter’s relation expressed as lgN=a-bM,by using the moderate and small events that occurred in and around the source area.The results show that the linear goodness of fitting varies abnormally prior to these moderately strong earthquakes.In the early stage of the earthquake preparatory process,distribution of the energy released through small events in and around the source area is isostatic and the fitting goodness approximates 1,while the distribution of the energy turns to be isostatic before moderately strong earthquakes,leading to the obvious decrease of the linear goodness of fitting.This phenomenon could be a medium term anomaly and a medium term criterion for moderately strong earthquake prediction.

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,2009to September,2016 are derived,and the seismic momentmoment magnitude MW of the earthquakes are calculated.Theand 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.

Rapid communications of preliminary results for the recent magnitude 6.6 Menyuan,Qinghai,China earthquake helps scientists better study intraplate earthquakes

Within one month of the magnitude 6.6 Qinghai,China Earthquake on 01/07/2022,several articles were published online in peer-reviewed journals and websites focusing on different aspects of this significant event.

Discussion on the Relation Between the Probabilistic Distribution of Magnitude in a Seismic Province and That in an Area with Potential Seismic Source

According to the joint probabilistic distribution model of magnitude and space,the author discusses the relationship between the probabilistic distribution of magnitude in a seismic province and that in an area with potential seismic sources.The results show that if the magnitude probabilistic distribution follows the truncated exponential form in a seismic province,there must be some potential source in which the magnitude probabilistic distribution does not conform to that form.The result is consistent with the concept of "characteristic earthquake" derived from the study of actual records of seismicity and the study of geology.The author suggests that the relationship between the probabilistic distribution of magnitude in a seismic province and that in a seismic potential area must be considered in the study of the analysis of seismicity,seismic zonation and engineering seismology,for the purpose of the evaluation of the probabilistic distribution of magnitude correctly in every area with potential

Control Parameters of Magnitude—Seismic Moment Correlation for the Crustal Earthquakes

In connection with conversion from energy class KR (KR = log10E R, where ER — seismic energy, J) to the universal magnitude estimation of the Tien Shan crustal earthquakes the development of the self-coordinated correlation of the magnitudes (mb , ML, Ms ) and KR with the seismic moment M0 as the base scale became necessary. To this purpose, the first attempt to develop functional correlations in the magnitude—seismic moment system subject to the previous studies has been done. It is assumed that in the expression M (mb , ML , Ms) = Ki + zi log10M0 , the coefficients ki? and zi? are controlled by the parameters of ratio?(where;f0 —corner frequency, Brune, 1970, 1971;M0, N×m). According to the new theoretical predictions common functional correlation of the advanced magnitudes Mm (mbm = mb , MLm = ML , MSm = MS ) from log10M0,? log10t0? and the elastic properties (Ci) can be presented as , where , and , for the averaged elastic properties of the Earth’s crust for thembmthe coefficients Ci= –11.30 and di = 1.0, for MLm: Ci = –14.12, di = 7/6;for MSm : Ci = –16.95 and di = 4/3. For theTien Shan earthquakes (1960-2012 years) it was obtained that , and on the basis of the above expressions we received that MSm = 1.59mbm – 3.06. According to the instrumental data the correlation Ms = 1.57mb – 3.05 was determined. Some other examples of comparison of the calculated and observed magnitude - seismic moment ratios for earthquakes of California, the Kuril Islands, Japan, Sumatra and South America are presented.

Application of a time-magnitude prediction model for earthquakes

在这篇论文，我们为地震预言讨论大小时间模型参数的物理意思。为在在中国的所有十一个地震地区的强烈地震的怀孕期过程能被大小时间预言模型用模型的参数的计算描述。为中国的普通模型参数值是：b = 0.383， c=0.154， d = 0.035， B = 0.844， C =−0.209，和 D = 0.188。模型参数的坚韧性在转变数据，空间程度，和时间的时期的最小的大小从变化被估计。模型的空间、时间的适用性的分析显示计算单位尺寸应该是至少 4 °×为在诺思中国的地震地区的 4 °，至少 3 °×在西南和西北中国的 3 °，和时间时期应该是只要可能。

Estimating the Frequency, Magnitude and Recurrence of Extreme Earthquakes in Gulf of Aqaba, Northern Red Sea

Humans coexist with extreme events all the time, only when the intensity of the event becomes greater than a certain level there is a resulting disaster. Small earthquakes occur all of the time with no adverse effects. Only large earthquakes cause disasters. Statistical analysis reveals that larger events occur less frequently than small events. In a year, we would have many values for the events;the annual maximum was the greatest of those values. Within an annual series, only the largest value per year is allowed, even if an additional significant peak occurs. As the magnitude of a hazardous increases, the frequency of occurrence (how often a given magnitude is equaled or exceeded) decreases. Thus, major disasters result from a small number of large events that rarely occur. A plot of recurrence intervals versus associated magnitudes produces a group of points that also approximates a straight line on semi-logarithmic paper. Therefore, past records of earthquakes at the Gulf of Aqaba, Northern Red Sea for months from May, 1999 to Feb, 2016 are used to predict future conditions concerning the annual frequency, the return period, the percentage probability for each event, and the probability of a certain-magnitude earthquake occurring in the region during any period.

Seismic Risk Assessment and Maximum Magnitudes of Potential Earthquakes on Active Faults near Lanzhou City

The Zhuanglang river and Baiyin Baiyangshu river faults are late Quaternary faults near Lanzhou city,which pose a threat to the safety of the city. However,the cause of medium-strong earthquakes along the fault is rather complicated and even uncertain. It is important for us how to assess the magnitudes of maximum potential earthquakes and the seismic risk of the faults. The authors make reference to the method that Wen Xueze,et al.(2007) developed to assess the magnitudes of maximum potential earthquakes in sub-areas of moderately and weakly active faults in the eastern Chinese Mainland,and brought forward an empirical relationship between the maximum magnitudes M_max and the a_t/b values of the sub-areas' frequency-magnitude relationships in the Lanzhou area. By using this empirical relationship,the authors have estimated the upper-limits M_u of the Zhuanglang river and Baiyin Baiyangshu river active faults near Lanzhou city as M_S6.9 and 6.3,respectively. In addition,they have assessed the average interval recurrence time and the probabilities of destructive earthquakes on the faults.

The Coulomb Stress Change Associated with the Taiwan Straits M_S 7.3 Earthquake on September 16,1994 and the Risk Prediction of Its Surrounding Faults

Using the focal mechanism solutions and slip distribution model data of the Taiwan Straits MS7.3 earthquake on September 16, 1994, we calculate the static Coulomb stress changes stemming from the earthquake. Based on the distribution of aftershocks and stress field, as well as the location of historical earthquakes, we analyze the Coulomb stress change triggered by the Taiwan Straits MS7.3 earthquake. The result shows that the static Coulomb stress change obtained by forward modeling based on the slip distribution model is quite consistent with the location of aftershocks in the areas far away from the epicenter. Ninety percent of aftershocks occurred in the stress increased areas. The Coulomb stress change is not entirely consistent with the distribution of aftershocks near the epicenter. It is found that Coulomb stress change can better reflect the aftershock distribution far away from the epicenter, while such corresponding relationship becomes quite complex near the epicenter. Through the calculation of the Coulomb stress change, we find that the stress increases in the southwest part of the Min-Yue (Fujian-Guangdong) coastal fault zone, which enhances the seismic activity. Therefore, it is deemed that the sea area between Nanpeng Island and Dongshan Island, where the Min-Yue coastal fault zone intersects with the NW-trending Shanghang-Dongshan fault, has a high seismic risk.

新疆乌什7.1级地震灾害及应急救援行动

介绍了2024年1月23日乌什7.1级地震基本参数、发震构造背景、余震序列和建筑工程破坏及震害特征,概述了地震发生后各级政府和部门、行业应急救援行动,讨论了新疆地震应急准备工作经验,提出了未来做好防震减灾救灾工作的启示。

Earthquake probabilities and magnitude distribution (M ≥ 6.7) along the Haiyuan fault, northwestern China

In recent years, some researchers have studied the paleoearthquake along the Haiyuan fault and revealed a lot of paleoearthquake events. All available information allows more reliable analysis of earthquake recurrence interval and earthquake rupture patterns along the Haiyuan fault. Based on this paleoseismological information, the recur- rence probability and magnitude distribution for M≥6.7 earthquakes in future 100 years along the Haiyuan fault can be obtained through weighted computation by using Poisson and Brownian passage time models and consid- ering different rupture patterns. The result shows that the recurrence probability of MS≥6.7 earthquakes is about 0.035 in future 100 years along the Haiyuan fault.

震后趋势判定技术系统CAAFs震后余震预测效果评价

自2019年正式运行以来,震后趋势判定技术系统CAAFs为震后应急与趋势研判及时提供数据和技术支撑。本文梳理总结CAAFs系统持续4.5年产出的数据,从全国和不同地区两个方面评价系统产出的震后余震预测结果,得到以下三点认识:①震级上限预测(发生某震级以上地震的可能性不大)的正确率大多为90%及以上,显著优于震级区间预测(存在发生同等大小地震的可能或存在发生某震级左右地震的可能),各分区预测情况差异不大;②震级区间预测震级普遍比地震实况偏高,实际7日内发生的最大余震震级与预测震级的差值(震级偏差)落入[-0.5,0.5]区间的地震比例约为44%,落入[-1,1]区间的地震比例约为69%,越靠近[-0.5,0.5]区间,地震的比例越高;③震级区间预测中,各分区有一定差异,西南地区优于西北、华南和华北东北三个地区,总的来看4~5级地震预测情况不如其他震级区间,可能与该震级区间内地震的最大余震震级变化范围较大有关。

Earthquake probabilities and magnitude distribution (M≥6.7) along the Haiyuan fault, northwestern China

In recent years, some researchers have studied the paleoearthquake along the Haiyuan fault and revealed a lot of paleoearthquake events. All available information allows more reliable analysis of earthquake recurrence interval and earthquake rupture patterns along the Haiyuan fault. Based on this paleoseismological information, the recur- rence probability and magnitude distribution for M≥6.7 earthquakes in future 100 years along the Haiyuan fault can be obtained through weighted computation by using Poisson and Brownian passage time models and consid- ering different rupture patterns. The result shows that the recurrence probability of MS≥6.7 earthquakes is about 0.035 in future 100 years along the Haiyuan fault.

Last Deglacial Soft-Sediment Deformation at Shawan on the Eastern Tibetan Plateau and Implications for Deformation Processes and Seismic Magnitudes

The eastern margin of the Tibetan Plateau is characterized by frequent earthquakes; however, research of paleo-earthquakes in the area has been limited^ owing to the alpine topography and strong erosion. Detailed investigations of soft-sediment deformation(SSD) structures are valuable for understanding the trigger mechanisms, deformation processes, and the magnitudes of earthquakes that generate such structures, and help us to understand tectonic activity in the region. To assess tectonic activity during the late Quaternary, we studied a well-exposed sequence of Shawan lacustrine sediments, 7.0 m thick, near Lake Diexi in the upper reaches of the Minjiang River. Deformation is recorded by both ductile structures(load casts, flame structures,pseudonodules, ball-and-pillow structures, and liquefied convolute structures) and brittle structures(liquefied breccia, and microfaults). Taking into account the geodynamic setting of the area and its known tectonic activity, these SSD structures can be interpreted in terms of seismic shocks. The types and forms of the structures,the maximum liquefaction distances, and the thicknesses of the horizons with SSD structures in the Shawan section indicate that they record six strong earthquakes of magnitude 6-7 and one with magnitude >7. A recent study showed that the Songpinggou fault is the seismogenic structure of the 1933 Ms7.5 Diexi earthquake. The Shawan section is located close to the junction of the Songpinggou and Minjiang faults, and records seven earthquakes with magnitudes of ?7. We infer,therefore, that the SSD structures in the Shawan section document deglacial activity along the Songpinggou fault.

Detection of a half-microgal coseismic gravity change after the Ms7. 0 Lushan earthquake

Because only a small near-field coseismie gravity change signal remains after removal of noise from the accuracy of observations and the time and spatial resolution of the earth＇s surface gravity observation system, it is difficult to verify simulations of dislocation theory. In this study, it is shown that the GS15 gravimeter, located 99.5 km from the epicenter of the Ms7.0 Lushan earthquake on April 20, 2013 at 08 ： 04 UTC ＋ 8, showed the influence of the earthquake from 2013-04-16 to 2013-04-26 after a time calibration, tide correc- tions, drift correction, period correction and relaxation correction were applied to its data. The post-seismic relaxation process of the spring in the gravimeter took approximately 430 minutes and showed a 2. 5 ×10^-8 ms^-2 gravity change. After correcting for the relaxation process, it is shown that a coseismic gravity change of approximately ＋0.59 ＋-0. 4 ~ 10-Sms-2 was observed by the GS15 gravimeter; this agrees with the simulated gravity change of approximately 0.31 ~ 10 -8 ms-2. The rate of the coseismie gravity change and the coseismic vertical displacement, as measured by one-second and one-day sampling interval GPS units, is also consistent with the theoretical rate of change. Therefore, the GS15 gravimeter at the Pixian Station observed a coseismic gravity change after the Ms7.0 Lushan earthquake. This and similar measurements could be applied to test and confirm the theory used for these simulations.

Real-time prediction of earthquake potential damage:A case study for the January 8,2022 M_(S) 6.9 Menyuan earthquake in Qinghai,China

It is critical to determine whether a site has potential damage in real-time after an earthquake occurs,which is a challenge in earthquake disaster reduction.Here,we propose a real-time Earthquake Potential Damage predictor(EPDor)based on predicting peak ground velocities(PGVs)of sites.The EPDor is composed of three parts:(1)predicting the magnitude of an earthquake and PGVs of triggered stations based on the machine learning prediction models;(2)predicting the PGVs at distant sites based on the empirical ground motion prediction equation;(3)generating the PGV map through predicting the PGV of each grid point based on an interpolation process of weighted average based on the predicted values in(1)and(2).We apply the EPDor to the 2022 M_(S) 6.9 Menyuan earthquake in Qinghai Province,China to predict its potential damage.Within the initial few seconds after the first station is triggered,the EPDor can determine directly whether there is potential damage for some sites to a certain degree.Hence,we infer that the EPDor has potential application for future earthquakes.Meanwhile,it also has potential in Chinese earthquake early warning system.