Characteristics and mechanism of MBT anomaly of Karakum desert related with the Hindu Kush earthquake

Abstract

<p>The Hindu Kush is seismically active zone locates to the southwest of Pamir Plateau. Earthquakes are frequent here, but very a few relevant studies on earthquake anomalies was found. We investigated the abnormal change of satellite microwave brightness temperature (MBT) related with the recent Mw 6.4 earthquake occurred on January 11, 2024 near the Karakum Desert, Hindu Kush. We found a significant positive MBT anomaly appeared in the eastern part of Karakum Desert, on the immediate west of the epicenter, from three days before and two days after the earthquake. The temporal characteristics of the positive MBT anomaly can be described in sequence as follows: pre-earthquake (pre-EQ) rising, nearearthquake (near-EQ) enhancing, co-earthquake (co-EQ) peaking, after-earthquake (after-EQ) persisting and dissipating eventually. Validating with multi-source auxiliary data such as surface temperature (ST), microwave polarization difference index (MPDI), soil moisture (SM), rainfall and snowfall, we confirmed the positive MBT anomaly appeared in the Karakum Desert from January 10 to January 13 was attributed to the seismic activity but not meteorological factors. The upward transfer of P-hole particles, activated in the deep hypocenter area by accumulated crustal stress during the pre-, co- and after-EQ period, to the Quaternary surface along the stress gradient, was believed to have reduced the local ground surface dielectric constant and amplified the microwaveradiation,which leading subsequently to the positive MBT anomalies. In addition,wefound therewas also abnormal locallyhighCH4concentrationoccurred nearthe epicenter one day before the earthquake, which was probably related to the fault relaxing and CH4 releasing before the impending earthquake. This study has reference significance for identifying potential MBT anomalies during the seismogenic period and for the earthquake early warning in Hindu Kush region<br><br></p>