Satellite-ground Joint Analysis Of Ionospheric Disturbance Before And After Strong Earthquake

With the advent of the satellite era,monitoring and analyzing the parameters of ionosphere through electromagnetic satellites has become an important means of earthquake prediction,which is widely used in earthquake prediction.In February 2018,China successfully launched ZH-1 Seismo-Electromagnetic Satellite(CSES),and a huge number of data need to be processed.At the same time,the observation of ground-based stations has been carried out for decades in China and there have been several decades of data accumulation.At present,most of the methods of earthquake prediction are single data.The method of combining satellite data with ground-based data is not mature,many effective ionospheric disturbances are not fully utilized before earthquakes.This paper capturing and analyzed abnormal disturbance before earthquake by processing the ionosphere TEC data from Crustal Movement Observation Network of China(CMONOC),Jet Propulsion Laboratory(JPL),electron density and 1Hz Geomagnetic data from CSES and 1Hz Geomagentic from SWARM,to improve the ability of extracting and identifying ionospheric earthquake precursor information during seismogenic period,and provide a new idea for joint analysis of ionospheric data observed by satellite and groud instument.In this paper,the above data are processed and analyzed by sliding quartile,polarization analysis,moving average and wavelet transform.According to different parameters,we select two earthquake cases in Indonesia for detailed analysis,The main contents of this paper are as follows:1.Abnormal disturbance of Ionospheric TEC before earthquakeBased on the GPS TEC data provided by CMONOC and JPL and the electron density observed by CSES,this paper use sliding quartile to analysis the ionospheric TEC of the epicenter region and its magnetic conjugate region(Sichuan region,China)before the M_s6.8 earthquake in the south of Sumatra island,Indonesia on August 2,2019,and the statistical analysis of the correlation between the Indonesia earthquake and the ionospheric TEC abnormal disturbance in the magnetic conjugate region is carried out.The results are as follows1)The GPS TEC data provided by CMONOC and JPL are processed and analyzed by the method of sliding quartile.It is found that the strong and large-scale TEC abnormal disturbance appears one week(July 25)before the south of Sumatra island,Indonesia M_s6.8 eartuquake on August 2,2019(July 25)over the epicenter region and its magnetic conjugate region(Sichuan region).2)Based on the electron density of all revisited orbits(excluding the orbit with space weather index exceeding the limit)observed by CSES in July and August 2019,it is found that the orbit near the epocenter on July 25 formed the peak electron density in the epicenter region(10°S-5°N)and its magnetic conjugate region(15°N-30°N),and the electron density at(10°S-30°N)is higher than the background value.It corresponds to the abnormal range observed by JPL.3)In order to verify the correlation between TEC anomaly in Sichuan area and earthquakes in Indonesia,we made a statistical analysis of 99 earthquakes with magnitude more than M_s6.0 and above in Indonesia from 2011 to 2019:in space,the TEC anomalies in Sichuan region have a significant spatial-temporal correlation with strong earthquakes in the west of Indonesia.In time,the TEC abnormal disturbance caused by strong earthquakes in Indonesia mainly occurred in the daytime from 10 days before the earthquake to 4 days after the earthquake,mainly in the 6:00(LT)-11:00(LT).The frequency of TEC abnormal disturbance is the most in 7:00(LT)and 10:00(LT),and the frequency of TEC abnormal disturbance is low in other time periods.Few anomalies related to Indonesia strong earthquake are observed at night.2.Anomalous disturbance of geomagnetic field before earthquakeBased on the 1Hz geomagnetic data from SWARM B and CSES,this paper use the methods of polarization ratio analysis,moving average algorithm and wavelet transform to process the geomagnetic data,and the abnormal disturbance signals of geomagnetic before the Indonesia Sumbawa M_s6.9 earthquake on August 5,2018 are analyzed in time domain and frequency domain.The results are as follows1)Based on the time series of polarization ratio of SWARM magnetic field data from March to September in 2018,it is found that the polarization ratio of Sumatra M_s6.4 earthquake on June 13,2018 and Indonesia Sumbawa M_s6.9 earthquake on August 5,2018 has a low valley(about 15 days before the earthquake).2)The magnetic field data of orbits in the period of low polarization ratio before the Indonesia Sumbawa M_s6.9 earthquake on August 5,2018 are obtained by moving average with a window of 53s,it is found that the orbit data of SWARM-B near the epicenter on July 29 capture magnetic disturbance signals of the X(north-south)and Y(east-west)components of the magnetic field in ULF frequency band at(5°S-12°S)and(18°N-29°N)(epicenter region and its magnetic conjugate region)by SWARM,and it proved that the abnormal magnetic field signal is generated in the ULF frequency band of this earthquakethe and the signal in ULF can propagate along the magnetic line.The magnetic field data of CESE after moving average with a window of 53s and double fit-difference also captured the signal.3)After wavelet transform,the magnetic field data of CSES and SWARM-B in ULF frequency band show obvious abnormal enhancement in 0.05-.0.1Hz.The X component and Y component of the magnetic field are abnormally enhanced by SWARM B in(8°S-12°S)and(22°N-28°N)(epicenter region and its magnetic conjugate region),while only the Y component of the magnetic field in the epicenter region is abnormally enhanced by CSES's magnetic field data.