The Differential of Casualties, Energy Radiation, and Characteristics of Sequences from the Same MS: The Menyuan MS 6.9 2022 and Morocco MS 6.9 2023 Earthquakes

The January 10, 2022, MS 6.9 Menyuan, China, earthquake occurred caused by strike-slip faulting in the tectonically complex region of the northeastern Tibetan Plateau, and ten people were injured in Menyuan City. The September 8, 2023, MS 6.9 Morocco, earthquake occurred in the African Plate at shallow depth with oblique-reverse faulting. At least 2,900 people were killed and more than 5,000 injured in Morocco till to September 13, 2023. International media reports of such kind of disasters by the Morocco earthquake only resulted from poor building structure design and low-solidity housing, such as in Marrakech, southwest of the epicenter. The surface wave magnitude (MS) of the two earthquakes is the same, and the moment magnitude (MW) and energy magnitude (Me) of the Menyuan mainshock are slightly lower than those of the Morocco event. Although the scalar moment and radiated seismic energy from Morocco dynamic rupture are only 2~3 times of the Menyuan earthquake, the density of urban residents nearby and around the epicenter of the Morocco mainshock is at least more than a hundred times higher than that around the epicenter of the Menyuan even. For the Morocco sequence, the USGS reported the number of aftershocks higher than MW4.0 is only seven and the largest is 4.9. In contrast, there are two aftershocks higher than MS5.0 in the Menyuan sequence recorded by the China Earthquake Networks Center, 5.1 and 5.2, respectively. Normally, a similar magnitude does not reflect the equivalent seismic moment, release of radiated energy, and the occurrence of strong aftershocks. Meanwhile, devastating loss of life and injuries are not only due to the design of the building and the quality of the house.

Acknowledgment: This research is supported by the Spark Program of Earthquake Sciences (XH22012YC)