A high-resolution seismic catalog for the 2021 M_(S)6.4/M_(W)6.1 Yangbi earthquake sequence, Yunnan, China: Application of AI picker and matched filter

We present a high-resolution seismic catalog for the 2021 M_(S)6.4/M_(W)6.1 Yangbi sequence.The catalog has a time range of 2021-05-01 to 2021-05-28,and contains~8,000 well located events.It captures the features of the whole foreshock sequence and the early aftershocks.We designed a detection strategy incorporating both an artificial intelligent(AI)picker and a matched filter algorithm.Here,we adopt a hybrid AI method incorporating convolutional and recurrent neural network(CNN&RNN)for event detection and phase picking respectively(i.e.CERP),a light-weight AI picker that can be trained with small volume of data.CERP is first trained with detections from a STA/LTA and Kurtosis-based method called PAL,and then construct a rather complete template set of~4,000 events.Finally,the matched filter algorithm MESS augments the initial detections and measures differential travel times with cross-correlation,which finally results in precise relocation.This process gives 9,026 detections,among which 7,943 events can be well relocated.The catalog shows as expected power-law distribution of frequency magnitude and reveals detailed pattern of seismicity evolution.The main features are:(1)the foreshock sequence images simple fault geometry with consistent strike,but also show a variable event depth along strike;(2)the mainshock ruptures the same fault of the foreshock sequence and activate conjugate faults further to the southeast;(3)complex seismicity are developed in the post-seismic period,indicating complex triggering mechanisms.Thus,our catalog provides a reliable basis for further investigations,such as b-value studies,rupture process,and triggering relations.

Temporal evolution of the focal mechanism consistency of the 2021 Yangbi M_(S) 6.4 earthquake sequence in Yunnan

Using the Cut And Paste(CAP)method,we invert the focal mechanism of 38 moderate earthquakes(M_(S)≥3.0)recorded by Yunnan seismic network and analyze the corresponding focal mechanism consistency based on the minimum spatial rotation angle.Our results indicate that the M_(S)6.4 mainshock is induced by a lateral strike slip fault(with a rake angle of~-165°)and a little normal-faulting component event along a nearly vertical plane(dipping angle~79° and strike~138°).Combining our results with high resolution catalog,we argue that the seismogenic fault of this earthquake sequence is a secondary fault western to the major Weixi-Qiaohou-Weishan fault.The focal mechanism evolution can be divided into three periods.During the first period,the foreshock sequence,the focal mechanism consistency is the highest(KA<36°);during the second period which is shortly after the mainshock,the focal mechanism shows strong variation with KA ranging from 8° to 110°;during the third period,the seismicity becomes weak and the focal mechanism of the earthquakes becomes more consistent than the second period(18°<KA<73°).We suggest that the KA,to some extent,represents the coherence between local tectonic stress regime and the stress state of each individual earthquake.Furthermore,high focal mechanism consistency and high linearity of seismic distribution may serve as indicators for the identification of foreshock sequence.

Establishment of the ELF Network in Yunnan and Electromagnetic Precursory Monitoring Results of the Yangbi MS5.1 Earthquake on March 27,2017

This paper summarizes the layout of the Yunnan seismic ELF electromagnetic observation network,site selection,ELF electromagnetic instrument system,data processing and other construction. The principle and method of using the ELF electromagnetic wave technique to monitor and predict earthquakes are expounded. The long term monitoring of ELF electromagnetic fields is carried out in the Yunnan earthquake prone area,and at the same time,the changes in electrical parameters and spatial electromagnetic fields of the regional crustal medium structure are monitored. The functions such as automatic,quasi real time, remote monitoring, network monitoring, data processing specialization, data service,data sharing and industrialization of the ELF electromagnetic observation data have been realized. In order to capture the deep electromagnetic precursory information of the earthquakes,service for earthquake prediction research,which has broad application prospects and development potential. Through the research of the seismicity of Yunnan in the trial run period of the project,the preliminary results of the extreme low frequency electromagnetic observation of the Yunnan earthquake in recent years are given. The electromagnetic precursors and the electromagnetic effects of the Yangbi earthquake are recorded. In the 3-month period before the earthquake,the power spectrum of the electric and magnetic fields,the apparent resistivity and the impedance phase in the observed signals are all abnormal,and gradually increased with time. The maximum value is reached 20 days before the earthquake,and an earthquake occurs when the change is restored to normal.

Performance of the Yangbi M_(S)6.4 earthquake disaster in different geomorphic units in Yunnan

An M_(S)6.4 earthquake occurred in Yangbi,Yunnan province,on May 21,2021.According to related investigations,the macro-epicenter of the earthquake is 6 km northwest of Yangbi County,and the seismogenic structure is the NW-trending Weixi-Qiaohou fault.The earthquake area is located in the hinterland of the Hengduan Mountains in the northwest of Yunnan Province,a region dominated by high and medium-high mountains,with deep canyons and tectonic basins in between.Various geomorphic features are derived from drastic topographic changes and huge geological differences in the earthquake area.There are a variety of buildings in the earthquake-affected zone,including civil and brick-wood structures ones with weak seismic performance,as well as brick-concrete and frame ones with better seismic performance.This paper summarizes and analyzes different characteristics of the earthquake in different geomorphic units through field investigations of different buildings and geological disasters in the affected area.The results show that under the same earthquake intensity,the damage to most buildings(located in slope areas or rooted in weak strata)is amplified by the earthquake.The earthquake has exerted an obvious propagation effect along the direction of the seismogenic structure.Moreover,local ground fissures will aggravate the damage to the buildings even without surface dislocation.Thus,we suggest that attention should be paid to the ground fissures caused by the slope effect.The fissure areas may also be the disaster spot of collapses and landslides in case of a high-magnitude earthquake.

Intensity Distribution of the Mojiang M_S5.9 Earthquake in Yunnan in 2018

The distribution of the intensity of the Mojiang M_S5.9 earthquake in Yunnan Province is expounded, and the damage characteristics of buildings and the damage ratio and seismic damage index of various building structures in each intensity area are compared with those of The Chinese Seismic Intensity Scale. The main basis and method of seismic intensity assessment are discussed in this paper. It is concluded that: ① The seismic intensity should be based on the earthquake damage of the housing structure, which takes up a high ratio in the seismic intensity assessment. It is recommended that seismic intensity is estimated by calculating the average seismic damage index. ② The highest intensity of the Mojiang M_S5.9 earthquake is Ⅷ degrees, with the long axis trending in the north-west direction. The area above Ⅶ degrees is 5,180 km^2. ③ The intensity distribution of the Mojiang M_S5.9 earthquake meets the national standard and the distribution law of seismic intensity in Yunnan.

Geomagnetic Variations Associated with Strong Earthquakes in Yunnan Area

In order to find geomagnetic anomalies associated with Ms ≥ 6.0 strong earthquakes in Yunnan area, geomagnetic harmonic wave amplitude ratios with Z, H and D components in TCH, THJ, CHX and YOS stations were analyzed. It was found that geomagnetic amplitude ratio of Yzhx experienced a trend of decrease and increase before most of strong earthquakes. Moreover, these variations in different periods were inconsistent and no similar changes appeared for Yzhy, which may relate to fault-zone conductivity variation and seismogenic structure.

Stress triggering effect on the 2022 Honghe M_(S)5.0 earthquake with historical strong earthquakes

The 2022 Honghe M_(S)5.0 seismic event is intriguing due to its occurrence in the south of the Red River Fault,an area historically lacking seismic activities greater than M_(S)5.0.To elucidate the seismogenic mechanism and scrutinize stress-triggered interactions,we calculated co-seismic and post-seismic Coulomb stress alterations induced by nine historical seismic events(M≥6.0).The analysis reveals that these substantial seismic events provoked co-seismic stress augmentations of 1.409 bar and postseismic stress increments of 0.159 bar.Noteworthy seismic events,such as the 1833 Songming,1877Shiping,1913 Eshan,and 1970 Tonghai earthquakes,catalyzed the occurrence of the Honghe earthquake.Areas of heightened future seismic risk include the southern region of the Red River Fault and the eastern segments of the Shiping-Jianshui and Qujiang faults.Additionally,we assessed the correlation between the spatial distribution of aftershocks and the Coulomb stress shift triggered by the mainshock,taking into account the influence of calculation parameter settings.

Improving Airgun Signal Detection with Small-Aperture Seismic Array in Yunnan

Repeating airgun sources are eco-friendly sources for monitoring the changes in the physical properties of subsurface mediums,but their signals decay quickly and are buried in the noises soon after traveling short distances.Stacking waveforms from different airgun shots recorded by a single seismic station(shot stacking)is the most popular technique to detect weak signals from noisy backgrounds,and has been widely used to process the data of Fixed Airgun Signal Transmission Stations(FASTS)in China.However,shot stacking sacrifices the time resolution in monitoring to recover a qualified airgun signal by stacking many shots at distance stations,and also suffers from persistent local noises.In this paper,we carried out several small-aperture seismic array experiments around the Binchuan FAST Station(BCFASTS)in Yunnan Province,China,and applied the array technique to improve airgun signal detection.The results show that seismic array processing combining with shot stacking can suppress seismic noises more efficiently,and provide better signal-to-noise ratio(SNR)and coherent airgun signals with less airgun shots.This work suggests that the array technique is a feasible and promising tool in FAST to increase the time resolution and reduce noise interference on routine monitoring.

Study of the Change in Wave Velocity Ratio before and after Two Strong Earthquakes Using Airgun Source Data

Using the signals excited by the large-volume airgun source at the Binchuan transmitting seismic station from January to June,2016,arrival-time data was acquired at four stations near the epicenter of the Eryuan MS4.5 and MS4.0 earthquakes on February 8,2016,as well as the epicenter of the Yunlong MS5.0 and Eryuan MS4.6 earthquakes on May 18,2016 through the waveform cross-correlation technique.The wave velocity ratio of the four stations was calculated using the single-station method.At the same time,the b-value and the focal mechanism consistency parameters of the study area were also calculated.The results show that:(1)the wave velocity ratio of each station experienced a process of decline-recovery-fast rise before the two strong earthquakes,and a significant quasi-synchronous rapid rise occurred within 3-12 days before the earthquake;(2)the timing of the rapid rise of the wave velocity ratio of the four stations before the Yunlong MS5.0 and Eryuan MS4.6 earthquakes were related to the epicentral distance.The station which observed the earliest increase in rapid rise is the farthest one from the epicenter,and the station where the rapid rise appeared in the latest is closest to the epicenter;(3)the form of change of the wave velocity ratio before the earthquake was different between stations located at different directions in the epicenter area;(4)the b-value and the focal mechanism consistency parameter which is commonly used to characterize the stress level both showed a downward trend before the two strong earthquakes,and were consistent with the change in the wave velocity ratio.According to the preliminary analysis,the wave velocity ratio obtained by using airgun source can better reflect the change in the stress state of the underground medium.

Using Airgun Source Signals to Study Regional Wave Velocity Changes before and after the Yunlong M_S5.0 and Yangbi M_S5.1 Earthquakes

On the basis of the airgun source signals recorded by the stations from January,2016 to June,2017,we use cross-correlation detection technology to obtain the characteristics of the stable phase travel time change of each station.We used the Yunlong MS5.0 and Yangbi MS5.1 earthquakes as samples.According to regional characteristics,13 stations with high signal-to-noise ratios and complete data were selected(including 3 fixed stations and 10 active source stations).They are divided into four regions,and on the basis of the GNSS baseline data,the characteristics of regional wave velocity changes before and after the earthquake are analyzed.The results show that the station phase travel time change and the regional stress characteristics represented by the GNSS baseline data have good correlation in the short-term.Due to different degrees of regional stress,there are differences in the travel time changes of different stations in the four regions.Before the Yunlong MS5.0 and Yangbi MS5.1 earthquakes,with regional stress adjustment,there is an upward trend in the travel time changes of related stations in the adjacent areas of up to 0.02 s.The difference is that there are differences in the time nodes and duration of the travel time anomalies,and there is a reverse descent process after the Yangbi MS5.1 earthquake.There are different degrees of travel time fluctuations in the relevant stations before and after the two earthquakes,but the fluctuation range before and after the earthquake was small.Compared with the water level change of the reservoir,the adjustment of the regional stress is more likely to have a substantial impact on the travel time changes of the relevant stations.

Characteristics of ground cracks caused by the M_(S) 6.4 Yangbi earthquake and the corresponding tectonic significance

An M_(S)6.4 earthquake occurred near Yangbi County, Dali Bai Autonomous Prefecture, Yunnan Province, at 21:48on May 21, 2021. The earthquake location is characterized by complex geological structures, with multiple active faults distributed around the epicenter that is located at the west edge of the Sichuan-Yunnan rhombic block(25.67°N, 99.87°E). A total of 42 ground cracks are found by earthquake field investigations. The cracks are mainly concentrated in the Ⅷ degree area on the west side of the Yangbi River. Among these, 9 coseismic tectonic ground cracks generated by shear fractures are found in three villages(i.e., Akechang, Meijia-Lijia, and Huajiazhuang), which are distributed along the strike of the northwest-trending linear folds, showing the tectonic characteristics of right-lateral tension or left-stepping cracks. The structural attribute of ground cracks sustains the kinematic properties of the Weixi-Qiaohou fault, namely right-lateral strike-slip.

Electromagnetic Abnormity Recorded by Borehole TOA Installment during the Mojiang M_S5. 9 Earthquake on September 8,2018

As an achievement of the cooperation with Japan,TOA electromagnetic observation station was established with an 800 m borehole antenna and put into service in 1992 in Dali,Yunnan province,China.Li Wuxian et al.(2003)summarized main anomalous variation characters by analyzing 23 strong earthquakes with magnitudes more than 5.0 recorded in the first ten years.This work mainly presents the electromagnetic changes prior to the last Mojiang MS5.9 earthquake on September 8,2018.First of all,the initial weak signals appeared in two ULF channels out of three observing channels(CH10.01-0.10 Hz,CH20.1-1.0 Hz and CH31-9 kHz)on May 30,2018 at Dali TOA electromagnetic station.The information recorded was characterized by wave-like changes with magnitudes of ACH1≤0.26 mV in CH1 and pulse-like impulses of ACH2≤0.6 mV in CH2,respectively.Then,abnormal information gradually enhanced either in magnitudes or in occurrence frequency.Pulse-like signals were full of lattices of recording paper for CH2 during June24-25 and slopped over the recording paper during June 28-29,with the magnitudes being greater than or equal to 10 mV.At the same time,the clear wave-like signals also appeared in CH1 with a maximum magnitude of^0.6 mV on June 28 and reached its climax.From then on,the information started to decrease from the end of July and only weak signals occasionally occurred till the end of August 2018,when obvious anomaly was recorded again in two ULF channels with maximum magnitudes of ACH1~0.2 mV and ACH2~0.3 mV respectively.Generally,these signals did not appear continuously but group by group and accumulated intensively only in ULF band instead of VLF band during the total period.10 days later,the Mojiang MS5.9 earthquake occurred on September 8,2018,300 km away from Dali TOA station,and a coseismic response was also recorded at this time.Thus,these ULF electromagnetic abnormities could be probably attributed to the Mojiang event.

Is clustered seismicity an indicator of regional stress?Insights from earthquake sequences in Yongning-Luguhu faulted basin,Southwest China

Using hypocenter relocation,moment tensor inversion,stress field inversion,and fault slip tendency analysis,this study systematically investigated three M5.5-5.8 earthquake sequences that occurred after 2000 in the Yongning-Luguhu faulted basin in the middle of the Lijiang-Xiaojinhe fault zone within the Sichuan-Yunnan block,Southwest China.Our results show that since the 2008 Wenchuan earthquake,the tectonic stress pattern in this area may have changed and that b-values estimated for the earthquake sequences show evidence of an increasing trend in stress in the study area.Seismicity in the small-scale faulted basin adjacent to the large-scale fault zone is a possible indicator of regional stress.We also note that the aftershocks of the M5.7 earthquake sequence in 2012 and the M5.5 earthquake sequence in 2022 show relatively clear fluid diffusion-triggering characteristics.Overpressure of deep fluids is still the main factor driving seismic activity in the region,and we propose that the background tectonic stresses have not yet reached critical levels.

Distribution of Landslides in Baoshan City,Yunnan Province,China

Using Google Earth software as a platform,this study has established an integrated database of both old and new landslides in Baoshan City,Yunnan Province,China,and analyzed their development characteristics together with distribution rules,respectively.Based on the results,a total of 2427 landslides occurred in the study area,including 2144 new landslides and 283 old landslides,with a total area of about104.8 km^2.The new landslides are mostly in small-scales with an area less than 10000 m^2,while the area of individual old landslide is mostly larger than 10000 m^2.By analyzing the relationship between the two types of landslides and eight impact factors(i.e.,elevation,slope angle,slope aspect,slope position,lithology,fault,regional Peak Ground Acceleration(PGA),and average annual rainfall),the different individual influencing factors,distribution regularities and mechanisms of the two types of landslides are revealed.In detail,the main influencing factors of new landslides are elevation,slope angle,slope aspect,slope position,lithology,regional PGA and average annual rainfall,while the influencing factors of old landslides are mainly elevation,slope angle,and lithology.This study provides basic data and support for landslide assessment and further disaster reduction in Baoshan City.Besides,it also provides new constraints in deeply understanding the effect of different topographic and geological conditions,historical earthquakes,rainfall and other factors on the occurrence mechanisms of both new landslides and old landslides.

Introduction to China’s Earthquake Emergency Response System

Following the M_(S)6.4 earthquake that occurred on May 21,2021 in Yangbi,Yunnan,China,the earthquake emergency response system(EERS)responded immediately.The real-time software delivered many seismic parameters that provided a preliminary assessment of the earthquake.The 24-hour on-duty staff and scientific researchers revised these parameters and produced more detailed reports to understand the cause of the earthquake and the potential damage,which provided valuable information for emergency rescue operations and earthquake situation assessment.Emergency personnel were dispatched immedia-tely to the earthquake site to observe the aftershocks,investigate the damage,and guide and assist in the relief efforts.This paper describes the EERS response to the Yangbi earthquake to demonstrate the characteristics of the system and discuss the potential for further improvement.

The 2014 Northern Thailand Mw 6.1 Earthquake and its Seismogenic Tectonics

On May 5, 2014, an earthquake with a magnitude of Mw 6.1(the largest earthquake in Thailand so far) occurred in Chiang Rai of the Golden Triangle area in northern Thailand. We had an opportunity to conduct field survey immediately after the earthquake. Serious damage to buildings and casualties of lives were observed, and the estimated Maximum Mercalli Intensity(MMI) of the earthquake is Ⅷ(evaluated according to the MMI scale of the Chinese Standard). No long continuous ground ruptures were produced during the earthquake, but in the epicenter(commonly within MMI Ⅷ extent), massive small linear ruptures(usually several tens of meters long) developed and displayed intriguing structural features, offsetting many roads several centimeters left laterally on NE trending cracks or offsetting right laterally on NW trending ones. The focal mechanism solution of earthquake shows that this is a pure strike-slip event, and two nodal planes in NW and NE directions had the same motion senses respectively as those of breakage associated with the earthquake. The long axis of the isoseismals and aftershock distributions are in NE direction,which is consistent with the strike of Luang Namtha fault. The 230-km-long Luang Namtha fault which starts from the border of China and Laos, runs through northern Laos, and terminates at Chiang Rai of Thailand is predominated by left-lateral strike-slip and active in late Quaternary, and two earthquakes over Ms 6.0 occurred along the fault in 1925 and 2007 respectively. This Mw 6.1 earthquake occurred at the southwestern end of the fault. All related features such as evident structural rupturing, elongated orientation of MMI and aftershock distribution,as well as the location of the epicenter,suggest that the Luang Namtha fault may be responsible for the 2014 Northern Thailand earthquake.

Study on Dynamic Characteristics of Crustal Deformation in the Yunnan Area Using GPS

Based on the GPS velocity field data of 1999-2007 and 2011-2013,we used the least squares configuration method and GPS velocity profile results to synthetically analyze the dynamic evolution characteristics of crustal deformation in the Yunnan area before and after the Wenchuan earthquake. The dynamic evolution of GPS velocity field shows that the direction is gradually changed from the south in the southern part of the SichuanYunnan block to the south-west in the southern Yunnan block and there is a clear relative motion characteristic near the block boundary fault zone. Compared with the GPS velocity of 1999-2007,the results of 2011-2013 also reflect segmental deformation characteristics of the block boundary fault zone. Southeast movement shows a significant increase,which may be related to crustal deformation adjustment after the Wenchuan earthquake. The dynamic evolution of strain parameters shows a pattern of"extension in the middle and compression at both ends"in the whole area and the distribution of deformation(shear,extension or compression)is closely related to the background motion and deformation characteristics of the main fault zone. Compared with the results of the period of 1999-2007,the extensional deformation zone of 2011-2013 is expanded eastward and southward. The compressional deformation of the eastern boundary(the Xiaojiang fault zone)of the Sichuan-Yunnan block is no longer significant,which is mainly concentrated in the northern section of the Xiaojiang fault zone and may be related to the post-seismic deformation adjustment of the Wenchuan earthquake. The GPS velocity profile results show that the left-lateral slip velocity of the Xiaojiang fault zone reduced gradually from north to south(10 mm/a-5 mm/a),and the width of the northern section is wider. The right-lateral slip rate of the Honghe fault zone is about 4 mm/a,and the deformation width is wider. The dynamic results show that the Wenchuan earthquake has little effect on the deformation modes of these two fault zones.

Research on the Crustal Velocity Model of the Yunnan Region and Its Application

This paper selects the records of 7,412 earthquakes,each recorded by more than 10 stations in Yunnan between 2009 and 2014 to acquire the traveltime curves.Meanwhile,for improving precision,linear analysis,reduced traveltime curve and interval stability analysis are conducted focusing on the records of 83 earthquakes with M_L≥3.0 recorded each by≥80%of the stations,and by combining predecessors'research results,the initial crustal velocity model of the study area is obtained.By selecting 200 earthquakes with M≥3.0 occurring in Yunnan between 2010 and 2014,using the Hyposat batch location processing method to iterate the initial velocity model,and performing fitting to S waves layered velocity structure,we obtain the crustal velocity model for the Yunnan region,namely,the 2015 Yunnan model,with:v_(P1)=6.01km/s,v_(P2)=6.60km/s,v_(Pn)=7.89km/s,H_1=20km,H_2=21km,v_(S1)=3.52km/s,v_(S2)=3.86km/s,v_(Sn)=4.43km/s.Analysis on earthquake relocations based on the new model shows that most earthquakes occurring in Yunnan are at a depth of 10km-20km of the upper crust.The March 10,2011 M_S5.8Yingjiang and August 3,2014 M_S6.5 Ludian earthquakes are relocated,and the focal depths determined with the new model are respectively close to the precise positioning result and hypocentral distance to the strong motion stations at the epicenters,indicating that the new one-dimensional velocity model can better reflect the average velocity structure of the study area.

An accessible seismological dataset of 2021 Yangbi M_(S)6.4 earthquake

A M_(S)6.4 earthquake occurred on 21 May 2021 in Yangbi county,Dali prefecture,Yunnan,China,at 21:48 Beijing Time(13:48 UTC).Earthquakes with an M3.0 or higher occurred before and after the main shock.Seismic data analysis is essential for the in-depth investigation of the 2021 Yangbi M_(S)6.4 earthquake sequence and the seismotectonics of northwestern Yunnan.Institute of Geophysics,China Earthquake Administration(CEA),has compiled a dataset of seismological observations from 157 broadband stations located within 500 km of the epicenter,and has made this dataset available to the earthquake science research community.The dataset(total file size:329 GB)consists of event waveforms with a sampling frequency of 100 sps collected from 18 to 28 May 2021,20-Hz and 100-Hz continuous waveforms collected from 12 to 31 May 2021,and seismic instrument response files.To promote data sharing,the dataset also includes the seismic event waveforms from 20 to 22 May 2021 recorded at 50 stations of the ongoing Binchuan Active Source Geophysical Observation Project,for which the data protection period has not expired.Sample waveforms of the main shock are included in the appendix of this article and can be downloaded from the Earthquake Science website.The event and continuous waveforms are available from the Earthquake Science Data Center website(www.esdc.ac.cn)on application.

Design and implementation of low-cost geomagnetic field monitoring equipment for high-density deployment

The observation of geomagnetic field variations is an important approach to studying earthquake precursors.Since 1987,the China Earthquake Administration has explored this seismomagnetic relationship.In particular,they studied local magnetic field anomalies over the Chinese mainland for earthquake prediction.Owing to the years of research on the seismomagnetic relationship,earthquake prediction experts have concluded that the compressive magnetic effect,tectonic magnetic effect,electric magnetic fluid effect,and other factors contribute to preearthquake magnetic anomalies.However,this involves a small magnitude of magnetic field changes.It is difficult to relate them to the abnormal changes of the extremely large magnetic field in regions with extreme earthquakes owing to the high cost of professional geomagnetic equipment,thereby limiting large-scale deployment.Moreover,it is difficult to obtain strong magnetic field changes before an earthquake.The Tianjin Earthquake Agency has developed low-cost geomagnetic field observation equipment through the Beijing–Tianjin–Hebei geomagnetic equipment test project.The new system was used to test the availability of equipment and determine the findings based on big data..