Magnetic Fabric of Freshly Consolidated Lacustrine Mudstones Constrains the "Present-Day" Strain Field

The anisotropy of magnetic susceptibility (AMS) has great potential in deciphering weakly deformed fabrics that may be related to tectonic stress. Previous studies have suggested that magnetic lineation is a good indicator of paleostrain direction. It is unclear whether the magnetic fabric can also be used to indicate the present-day strain field. To verify this idea, we measured the AMS of freshly consolidated lacustrine fine-grained sediments at 11 locations in the Qaidam and Chaka-Gonghe basins of the northeastern Tibetan Plateau and compared it with the present-day strain field deduced from the global position system (GPS) velocity field. The magnetic lineations of both room-temperature and low-temperature AMS are roughly perpendicular to the GPS-derived tectonic shortening direction within the error range, suggesting that the AMS of freshly consolidated muds is an effective indicator of the present-day strain field, even if the sediments appear undeformed at the outcrop scale. Knowledge of the present-day crustal stress field is important for understanding seismic activity and plate tectonics. Earthquake focal mechanisms and borehole breakouts are the traditional methods used to investigate the present-day stress field. The former depends on the frequency of seismic activities, the magnitude, and the location of each earthquake, none of which can be controlled or adjusted. The latter is time-consuming and laborious. Magnetic fabric is an economical, rapid, and sensitive indicator of paleostrain. If the magnetic fabric of recently deposited mudstone is measurable, anisotropy of magnetic susceptibility (AMS) has the potential to be used to investigate the present-day stress. In this study, we compared the magnetic fabric of freshly consolidated lacustrine mudstones with the present-day stress field derived from traditional stress indicators and found a rough consistency between them. This suggests that magnetic fabric can be used as an indicator of the present-day stress field, which will add much more new data to the world stress database. The freshly consolidated fine-grained lake sediments in the northeastern Tibetan Plateau record a weakly deformed fabricMagnetic lineations of freshly consolidated muds in the Qaidam and Chaka-Gonghe basins are roughly consistent with global position system-derived strain fieldThe magnetic fabric of the freshly consolidated mud deposited in still water is an effective indicator of the present-day strain field