Self-similarity of low-frequency earthquakes

Abstract

Low-frequency earthquakes are a particular class of slow earthquakes that provide a unique source of information on the mechanical properties of a subduction zone during the preparation of large earthquakes. Despite increasing detection of these events in recent years, their source mechanisms are still poorly characterized, and the relation between their magnitude and size remains controversial. Here, we present the source characterization of more than 10,000 lowfrequency earthquakes that occurred in 2012-2016 along the Nankai subduction zone in western Shikoku, Japan. We show that the seismic moment of these events scales as the inverse of the cube of the corner frequency, as widely observed for regular earthquakes. The retrieved scaling implies self-similar rupture process for low-frequency earthquakes, with constant stress drop.

Moment‐Duration Scaling of Low‐Frequency Earthquakes in Guerrero, Mexico

“…As a conclusion, in the seismic moment range of our events (8 × 10 11 −1 × 10 13 N.m), the measure of corner frequency is not biased by the detection process, for values of corner frequency between 1 and 8 Hz. A frequency range of around 1-10 Hz and range of moments 1.5 orders of magnitude wide were enough for Supino et al (2020) to measure a steeper dependence of corner frequency on seismic moment and should thus be enough in this study to estimate a moment-duration scaling without significant artifacts.…”

“…In Cascadia, LFEs source duration has been found to be very weakly dependent on their seismic moment, scaling along M 0 ∝ T 10 (Bostock et al., 2015). On the other hand, in Nankai, LFEs exhibit a self‐similar behavior, scaling along M 0 ∝ T 3 (Supino et al., 2020). To our knowledge, this is the first published work to measure source parameters for LFEs in Guerrero, Mexico.…”

Episodicity and Migration of Low Frequency Earthquakes modeled with Fast Fluid Pressure Transients in the Permeable Subduction Interface

“…These shortcomings may be limiting in subduction zones because the brittle-to-ductile transition proceeds over an increasingly wide off-fault region as depth increases [73]. Source dimensions for tremor and LFEs are typically inferred to be a few hundred meters [e.g., 23,31,92], close to the thickness of the highly deformed permeable fault zone [e.g., 4]. This calls for more complete models dealing with processes in the interior of these zones.…”

Does Deep Tectonic Tremor Occur in the Central‐Eastern Mediterranean Basin?

“…The results indicate that in all the investigated regions but in Peloponnese (Hellenic Subduction Zone), we would be able to detect tremor episodes composed by LFEs of M w larger than ∼1.5–1.9 (Figure 5). Similar M w LFEs or larger have been documented at several fault systems around the Pacific rim, including the Guerrero trench in Mexico (M w 1.7–3 with a few events up to M w 3.5, Farge et al., 2020), the Cascadia Subduction Zone (M w 1.0–2.6, Bostock et al., 2015), the Parkfield‐Cholame segment of the San Andreas Fault (M w 1.6–1.9, Fletcher & McGarr, 2011), and the Nankai trench in Japan (M w 0.9–2.2, Supino et al., 2020). Previous studies have noticed lower M w LFEs obtained from amplitude ratios with local earthquakes, which may underestimate LFE magnitudes due to differing frequency contents relative to local earthquakes (e.g., Bostock et al., 2015).…”

“…Mw refers to values for individual LFEs comprising the tremor episodes. For reference, the dashed horizontal lines indicate the Mw of the largest detected LFEs within tremor episodes at several fault systems around the Pacific rim, including the Guerrero trench (Fa20, Farge et al, 2020), the Cascadia Subduction Zone (Bo15, Bostock et al,2015), the San Andreas Fault (F&M11, Fletcher & McGarr, 2011) and the Nankai trench (Su20, Supino et al, 2020).. KTF, Kefalonia Transform Fault; CSZ, Calabrian Subduction Zone; HSZ, Hellenic Subduction Zone; NAF, North Anatolian Fault. For more details on the synthetic tests performed to estimate the magnitude thresholds refer to Text S2.…”