Statistical analysis and assessment of ionopheric anomalies before large earthquakes observed by ionosonde during 1958-2017,over Japan
Abstract
In Japan region, the previous statistical study during 1998-2010 shows that there is a positve anomaly 1-5 days before the earthquake with M>=6 D<=40 km. In this study, we performed statistical analysis and assessment on ionosonde data observed at Kokubunji (35.71N, 139.49E), Japan over 60 years of 1958 ~ 2017 in order to investigate the earthquake-related ionospheric anomalies. The ionosonde is operated by the National Institute of Information and Communication Technology, Japan. The studied parameters are NmF2 and hmF2. For each parameter, 15 days backward median value (Mv) and its' interquartile range (IQR) were calculated, and we take Mv-1.5IQR and Mv+1.5IQR, for the lower and the upper thresholds for anomalies, respectively. The analyzed period is from 1958 to 2017, and we select earthquakes occurred within 1000 km and 350 km radius from the ionosonde station, and M >= 6 and D <= 40 km. To investigate the correlation between ionospheric anomalies and earthquake, we perform the Superposed Epoch Analysis (SEA). We define an anomalous day if the day has anomalies more than 10 hours per a day. Then, we make up the binary time series data on the earthquake-related anomaly. We extract dataset 30 days before and after the earthquake day for the all selected earthquakes and perform SEA after removing the geomagnetically disturbed periods. To evaluate the statistical significance, we compute the random test. SEA results show that there is a significant positive anomalies 1-10 days before the earthquakes in NmF2 data. In our presentation, the SEA results after removing the ionospheric disturbances due to geomagnetic storms and the assessment for the effectiveness in the short-term earthquakes forecast using the Molchan's Error Diagram analyses will be given. Also the comparison between results of GPS-TEC and ionospheric tomography will be also present.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMNH52B..04H
- Keywords:
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- 2427 Ionosphere/atmosphere interactions;
- IONOSPHERE;
- 4302 Geological;
- NATURAL HAZARDS;
- 7223 Earthquake interaction;
- forecasting;
- and prediction;
- SEISMOLOGY;
- 7999 General or miscellaneous;
- SPACE WEATHER