Evolution of crustal inner displacement deficit in connection with strongest Taiwan’s earthquakes migration according to GPS data from 2014 to 2024

¹ Geophysical Center RAS, Moscow, Russia
² People's Friendship University of Russia, Moscow, Russia

Abstract

Synoptic animation shows the evolution of the accumulation of inner horizontal displacements of GPS stations on the Taiwan island over the decade 2014-2024. Inner displacements reflect the influence of local stresses in the earth’s crust. These characteristics make it possible to determine the least mobile zones, which are consolidated areas of the earth’s crust that are not subject to destruction before an earthquake. The spatial localization of the deficit in the accumulation of inner displacements marks zones of increased elastic stresses. These zones are identified with the locations of future earthquakes.

The work used time series of GPS coordinates [Blewit et al., 2018], a catalog of coordinates of earthquake epicenters (https://earthquake.usgs.gov/earthquakes/search/ ) and information about tectonic dislocations from the website (https://blogs.openquake.org/hazard/global-active-fault-viewer/ ) and publications [Malavieille et al., 2019].

Viewing the resulting synoptic animation allows for a phenomenological analysis of the evolution of the seismic-deformation process, its interpretation and the search for cause-and-effect relationships between deformation, seismicity and tectonics. Viewing and qualitative analysis of kinematic visualizations made it possible to see the spatiotemporal relationship between the deficit of inner displacements and the locations of the strongest earthquakes of the decade. Note that information on displacements is representative only for the territory where GPS stations are located. The eastern part of the video frames refers to the Philippine Sea. There is high seismicity in this part, but the displacement contours are obtained by extrapolation, which reduces the confidence in the interpretation of the results.

The first strong seismic events of 2014-2015 occurred in the Philippine Sea, with the exception of the earthquake on 13/02/2015 on Green Island (Lyudao). These areas are not provided with GPS stations. At the beginning of 2016, an area of minimum displacements (dark brown color) begins to form, covering almost the entire island of Taiwan. 11 days before the event of 02/05/2016, the site of the future epicenter at the triple junction of tectonic faults begins to come to life. After the event, the weakened epicentral zone of aftershocks grows simultaneously with the unconsolidation area near the city of Ch’engkung. This area further increases, accompanied by moderate and weak earthquakes on the coast and in the water area. By 2018, the displacement deficit region forms an extreme in central Taiwan. A zone of maximum gradients of transition from small to large displacements is formed along the eastern coast. In the Hualien City area, an area of calm in internal movements is revealed by strong and moderate events on 02/04/2018. Here, two days later on 02/06/2018, another strong event occurs. In April 2019, a little further south, this zone expanded due to a strong earthquake. This area of crustal decompression subsequently develops through weak to moderate shocks, migrating south along the coast. This area is highly active. This is where the northeastern end of the deep-sea Ryukyu Trench meets the coastal crust of Taiwan. At the same time, the sedentary area shifts westward to the middle part of the island. The earthquake of December 10, 2020 occurs in the north of the Philippine Sea in a place already disturbed by moderate and weak events. Subsequently, the area of crustal decompression intensively develops in the absence of strong events in the form of two centers in the Hualien and Ch’engkung region. Between them, a region of small displacements remains, awaiting three strong seismic events. The next strong earthquake on October 24, 2021 occurs near the city of Sudo on the coast of the island of Taiwan. It is followed by another earthquake on 10/03/2022 in the epicentral region of the Philippine Sea, complementing the vast zone of strong and moderate shocks on a series of faults running parallel to the Ryukyu Trench. The next strong event, along with several moderate ones, occurred on 03/22/2022 near the coast between Hualien and Ch’engkung. Another large undersea earthquake occurs on 05/09/2022, continuing to destroy the vast epicentral zone between Ryukyu Arc and Nanao Forearc. In this place, the main power source of a swarm of strong events is formed. A series of strong and moderate earthquakes occur in the Ch’engkung area on September 17-18, 2022, severely destroying the continuity of the crust and forming a local extreme of large displacements. The area of displacement deficit is transferred to the Hualien region. This zone is awaiting the occurrence of the strongest and deadliest earthquake in a decade, M7.4. It is accompanied by strong and moderate aftershocks on 04/02/2024. It is noteworthy that the maximum coseismic displacements do not occur at the epicenter of the strongest earthquake. They arise to the north in the zone of the strongest aftershocks.

Synoptic analysis showed that strong M>6 earthquakes onshore Taiwan Island over the past decade occurred near the area of inner displacement deficit. The epicenters of these events form a zone about 200 km long stretched along the eastern coast. The second epicentral zone of the series of strongest events is located in the region of subduction of the Philippine plate under the Eurasian plate. Note that the extremum of the displacement deficit remains in the Hualien region, leaving it potentially dangerous. As of 2024, a high-density zone has formed on the island, stretching in a strip from the east to the west coast. It connects the convergence of the deep-sea trenches Ryukyu and Manila with the land of the island territory. It can be assumed that this area marks a zone of increased seismogenic stresses.

Database creation date: 2024; Publication date: 14 June 2024

Contributor:
Geophysical Center of the Russian Academy of Sciences, Moscow, Russia
Institution: Geophysical Center of the Russian Academy of Sciences, Moscow, Russia
Publisher: Geophysical Center of the Russian Academy of Sciences (GC RAS), Moscow, Russia (http://www.gcras.ru/eng/)

Data format: .mov (QuickTime File Format)

doi: 10.2205/esdb-taiwan-quake-2014-2024

Citation: Kaftan V. I., Melnikov A. Yu., Dokukin P. A. (2024) Evolution of crustal inner displacement deficit in connection with strongest Taiwan’s earthquakes migration according to GPS data from 2014 to 2024. ESDB repository, GCRAS, Moscow, https://doi.org/10.2205/esdb-taiwan-quake-2014-2024

References: 

1. Blewitt, G., Hammond, W. C., Kreemer C. Harnessing the GPS data explosion for interdisciplinary science. Eos, 99 (2018) https://doi.org/10.1029/2018EO104623.
2. Malavieille J, Dominguez S, Lu C-Y, Chen C-T, and Konstantinovskaya E. Deformation partitioning in mountain belts: insights from analogue modelling experiments and the Taiwan collisional orogen. Geological Magazine. 2019 https://doi.org/10.1017/S0016756819000645

License:  This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

URL for downloading: http://esdb.wdcb.ru/doi/2024/esdb-taiwan-quake-2014-2024/ESDB-Taiwan-quake-2014-2024.mov

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