Reviewing precursors for the November ۲۰۲۱ Fin double-earthquakes

Precursors as informer pioneers of near future occurrence of earthquakes, are very diverse in their natures. We examined three short term possible precursors contain foreshocks, b-value variations, and amplitude abnormalities in the Very Low Frequency (VLF) radio signals for the November ۱۴, ۲۰۲۱ Fin double-earthquakes. By searching earthquakes one degree on each side of the hypocenter location in the IrSC, IIEES and BHRC catalogues, those data for the reviewing foreshocks were provided, then they analyzed by use of ZMAP for the b-value changes. Whereas, in the BHRC accelerometer portal reported ۸ events before the main shock times, none of them are not in the other catalogues. The temporal b-value variations from the normal, shown non sharp fits to the rises or falls of the seismicity as an expected indicator. Some b-value in accordance with the seismic up and down rate tracks, have high spatial uncertainties. We observed some amplitude anomalies in the VLF received signals from ۲σ criterion in about ۴ days before and up to ۵ days after the main shock times. Albeit, in follow the null hypothesis, for verifying (and not refused) the relations, are needed to be qualified data. Therefore, the reliability of the studied precursors completely dependent to the standard data, that sufficient-precise instruments for their observations and recording are vital requirement. It is also hoped that with the help of such reviews, necessity and importance of the data quality and improving of their acquisitions, be defined carefully and verified. There can be used of those types of reliable and high quality data in the pre-earthquake signals analyzing and or even reasonable prediction, if it possible in the future as valuable achievement.