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- Title
Spatiotemporal Characteristics of Relocated Deep Low‐Frequency Earthquakes Beneath 52 Volcanic Regions in Japan Over an Analysis Period of 14 Years and 9 Months.
- Authors
Kurihara, Ryo; Obara, Kazushige
- Abstract
We constructed a catalog of deep low‐frequency (DLF) earthquakes beneath 52 volcanic regions in Japan to investigate their seismicity based on three analyses: relocation, classification, and detection. Relocation and classification analyses were based on waveform correlation, and detection analysis was conducted using the matched filter technique. We detected a total of 105,327 DLF earthquakes and found that DLF earthquakes in many regions are spatially clustered with a spatial spread of only 1–2 km with approximately 5 km intervals between the lower limit of crustal earthquakes and Moho discontinuity. Based on temporal seismicity patterns, DLF earthquake groups in each region can be classified into episodic and non‐episodic types. Episodic groups consist of seismic swarms and quiescence. In some episodic groups, DLF earthquakes have constant recurrence interevent times or increasing interevent times as a function of time. Swarms of DLF earthquakes sometimes are associated with volcanic activities at the surface, which are crustal deformations of Meakan volcano, 2007 and 2014 eruptions of Ontake volcano, and the 2015 magma intrusion of Sakurajima volcano. The spatiotemporal characteristics of DLF earthquake groups may be linked to the movement of magmatic fluids. The discrete vertical separation of DLF earthquake groups may reflect small‐scale heterogeneities, such as injected magma. Periodic activity patterns may be caused by volcanic mechanisms, such as intermittent magma flow. The variety of DLF earthquake patterns may suggest that multiple mechanisms, including magma cooling and intermittent magma flow in complex magma supply systems, may trigger DLF earthquakes rather than a single mechanism. Plain Language Summary: In volcanic regions, deep low‐frequency (DLF) earthquakes are observed, which have lower dominant frequencies than regular earthquakes. We constructed a catalog of volcanic DLF earthquakes in 52 regions in Japan to investigate their distributions and temporal patterns. The catalog was constructed based on relocation, classification, and detection. Relocation and classification were conducted using waveform correlation based on the existing catalog and detection using the template‐matching method. The catalog shows that DLF earthquakes are divided into groups separately, with vertical intervals of approximately 5 km in many regions. The temporal patterns of DLF earthquakes in each group can be classified as episodic (i.e., associated with swarms) and non‐episodic. Some episodic DLF earthquakes have constant or increasing interevent times. In some volcanic regions, episodic activities of DLF earthquakes occurred with volcanic activity at the surface, such as eruptions or crustal deformations. The distribution of the groups of DLF earthquakes may reflect small‐scale heterogeneities beneath volcanoes, and multiple mechanisms may control the occurrence of the two types of DLF earthquakes. Key Points: Deep low‐frequency earthquakes beneath many volcanoes in Japan are clusteredThe temporal activity patterns of the earthquakes are classified into episodic type associated with seismic swarms and non‐episodic typeSpatiotemporal characteristics of deep low‐frequency earthquakes may be interpreted by magmatic fluid movement
- Subjects
SPATIOTEMPORAL processes; PLATE tectonics; SEISMIC waves; SEISMOLOGY; EARTHQUAKES
- Publication
Journal of Geophysical Research. Solid Earth, 2021, Vol 126, Issue 10, p1
- ISSN
2169-9313
- Publication type
Article
- DOI
10.1029/2021JB022173