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Xizang M7.1 Earthquake on 7 January 2025

7 January 2025

CHAN Yuk-po Bowie, WONG Cheuk-yiu Lillian

A major earthquake with magnitude 7.1 occurred in Xizang at 9:05 a.m. on 7 January 2025 according to the analysis of the Hong Kong Observatory (HKO). The epicentre was about 160 kilometres west-southwest of Rikaze, and about 2,770 km west-northwest of Hong Kong. The focal depth was around 10 km. HKO issued a strong earthquake report to the public approximately 12 minutes after the occurrence of the earthquake through multiple channels, including HKO’s website, “MyObservatory” mobile application, social media and the Government News and Media Information System. The seismic stations of HKO also recorded this earthquake (Figure 1). Since the earthquake was distant from Hong Kong, it was not locally felt.

According to reports, this shallow earthquake resulted in over 100 deaths and more than 100 injuries, as well as collapse of nearly three thousand houses in that area. The earthquake took place on a north-south striking normal fault near the boundary between the Eurasian Plate and the Indian Plate (part of the Indo-Australian Plate) (Figures 2 and 3). At least dozens of aftershocks followed the mainshock, with most of them below magnitude 3.

Major earthquakes generally occur more frequently at plate boundaries (Figure 4). The continental collisions between the Eurasian Plate and the Indian Plate have created complex fault systems at the periphery and interior of the Tibetan Plateau, resulting in active seismic activities (Figure 5). The largest earthquake that occurred within 500 km of this epicentre since 1908 was the M8.0 Nepal earthquake on 15 January 1934 (Figure 6). However, this M7.1 event has been the largest one within 100 km of the epicentre since instrumental records began. The frequency of earthquakes decreases with earthquake magnitude. Nearly twenty earthquakes of M7.0 or above occur globally each year on average (Figure 7). The previous one was the M7.4 earthquake near Vanuatu Islands on 17 December 2024.

Seismic waveform indicating the arrival of P-wave detected by the broadband seismograph at Hong Kong Po Shan station on 7 Jan 2025
Figure 1 Seismic waveform indicating the arrival of P-wave detected by the broadband seismograph at Hong Kong Po Shan station (around 2,770 km east-southeast of the epicentre of the Xizang M7.1 earthquake) at around 01:10:44 UTC (HKT = UTC + 8) on 7 January 2025, around 5 minutes and 26 seconds after the occurrence of the earthquake.
Diagram showing the global distribution of tectonic plates and the epicentre of the 2025 Xizang M7.1 earthquake
Figure 2 Diagram showing the global distribution of tectonic plates and the epicentre of the January 2025 Xizang M7.1 earthquake (yellow star), with the direction of relative motion of the Eurasian Plate and the Indian Plate indicated by orange arrows. (Base map modified from United States National Park Service [1])
Focal mechanism based on the HKO’s analysis
Figure 3 Focal mechanism based on the HKO’s analysis (“beachball” graphics at top right) and the faulting motion associated with the Xizang M7.1 earthquake. (Modified from United States Geological Survey (USGS) [2])
Distribution map of global earthquakes with magnitude 7.0 or above since 1811
Figure 4 Distribution map of global earthquakes with magnitude 7.0 or above since 1811 [3].
tectonic setting of Tibetan Plateau
Figure 5 The tectonic setting of Tibetan Plateau including the major fault systems (red lines) [4], the plate boundary between the Eurasian Plate and the Indian Plate (black line), and the epicentre of the Xizang M7.1 earthquake (yellow star).
Distribution map of earthquakes with magnitude 6.0 or above within 500 km of the epicentre of the January 2025 Xizang M7.1 earthquake since 1908
Figure 6 Distribution map of earthquakes with magnitude 6.0 or above within 500 km of the epicentre of the January 2025 Xizang M7.1 earthquake since 1908 [3].
Earthquake magnitudes and energy release, and comparison with other natural and man-made events, as well as the average number of earthquakes of different magnitudes per year worldwide
Figure 7 Earthquake magnitudes and energy release, and comparison with other natural and man-made events, as well as the average number of earthquakes of different magnitudes per year worldwide (Source: EarthScope [5]) [6]

References:
[1] National Park Service: Evidence of Plate Motions
[2] USGS Geological Survey: What is a fault and what are the different types?
[3] United States Geological Survey (USGS): Earthquake Catalog
[4] Seismic Active Fault Survey Data Center of China Earthquake Disaster Prevention Center
[5] EarthScope: How Often Do Earthquake Occur?
[6] HKO: How to Interpret Seismic Parameters?