Frequency-dependent attenuation of shear waves in the crust of the southern Kanto area, Japan

Kinoshita, Shūichi

doi:10.1785/bssa0840051387

Cited by 84 publications

(1 citation statement)

References 26 publications

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“…However, our results show stronger attenuation at higher frequencies. Some studies obtained smaller values of 𝑛 = 0.6 − 0.9 (Aki, 1980;Kinoshita, 1994;Moya & Irikura, 2003;Oth et al, 2010), in which case the attenuation effect becomes slightly stronger at higher frequencies. However, our observations are essentially explained even when a constant 𝑄 𝑠 -value of ~55 is assumed at 1-20 Hz (Fig.…”

Section: Discussionmentioning

confidence: 99%

Near-Source Waveform Modeling to Estimate Shallow Crustal Attenuation and Radiated Energy of Mw 2.0-4.5 Earthquakes

Yoshida,

Emoto,

Takemura

et al. 2023

Preprint

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Estimating the radiated energy of small-to-moderate (Mw < 5) events remains challenging because their waveforms are strongly distorted during wave propagation. Even when near-source records are available, seismic waves pass through the shallow crust with strong attenuation; consequently, high-frequency energy may be significantly dissipated. Here, we evaluated the degree of energy dissipation in the shallow crust by estimating the depth-dependent attenuation (Q-1) by modeling near-source (< 12 km) waveform data in northern Ibaraki Prefecture, Japan. High-quality waveforms recorded by a downhole sensor confined by granite with high seismic velocity helped to investigate this issue. We first estimated the moment tensors for M1–4 events and computed their synthetic waveforms, assuming a tentative one-dimensional -model. We then modified the -model in the 5–20 Hz range such that the frequency components of the synthetic and observed waveforms of small events (Mw < 1.7) matched. The results show that the Q-value is 55 at depths of < 4 km and shows no obvious frequency dependence. Using the derived -model, we estimated the moment-scaled energy (eR) of 3,884 events with Mw 2.0–4.5. The median eR is 3.6×10-5 , similar to the values reported for Mw >6 events, with no obvious Mw dependence. If we use an empirically derived Q-model (~350), the median eR becomes a one-order underestimation (3.1×10-6). These results indicate the importance of accurately assuming the Q-value in the shallow crust for energy estimation of small events, even when near-source high-quality waveforms are available.

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Section: Discussionmentioning

confidence: 99%

Near-Source Waveform Modeling to Estimate Shallow Crustal Attenuation and Radiated Energy of Mw 2.0-4.5 Earthquakes

Yoshida,

Emoto,

Takemura

et al. 2023

Preprint

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Slow slip and tremor search at Kilauea Volcano, Hawaii

Montgomery-Brown

Thurber

Wolfe

et al. 2013

Geochem Geophys Geosyst

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Kilauea Volcano, Hawaii, has hosted a long series of slow slip events observed since the installation of the continuous GPS network in 1996. Kilauea's slow slip events are inferred to occur on the decollement fault at 8 km depth beneath its south flank, with a location updip of the epicenters of large, regular earthquakes. Fault slip typically lasts about two days, and the events have magnitudes equivalent to Mw 5.3–6.0. While slow slip events in subduction zones are commonly accompanied by tectonic tremor (also called nonvolcanic tremor), no tremor has yet been reported in association with Kilauea's slow slip events. Instead, there are swarms of small triggered earthquakes, which is a characteristic only seen at select subduction zones (e.g., Boso and Hikurangi). A temporary array of seismometers was installed at Kilauea in 2007 in anticipation of a slow slip event. Here we use several established methods to perform a systematic search for tectonic tremor during geodetically defined slow slip events, as well as searching for tremor triggered by teleseismic surface waves. We do not detect tectonic tremor using any of these methods, although we are able to detect episodes of previously identified deep offshore volcanic tremor at 15–20 km depth and volcanic tremor from Kilauea. Although Kilauea's seismic network may not be adequate to observe tectonic tremor because Hawaii is seismically noisy and its crust is highly attenuating, it is also possible that the specific fault conditions on Kilauea's decollement are not conducive to such tremor generation.

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Development of Strong-Motion Observation Network Constructed by NIED

Kinoshita

Nato Science Series: IV: Earth and Environmental Sciences

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Frequency-dependent attenuation of shear waves in the crust of the southern Kanto area, Japan

Cited by 84 publications

References 26 publications

Near-Source Waveform Modeling to Estimate Shallow Crustal Attenuation and Radiated Energy of Mw 2.0-4.5 Earthquakes

Near-Source Waveform Modeling to Estimate Shallow Crustal Attenuation and Radiated Energy of Mw 2.0-4.5 Earthquakes

Slow slip and tremor search at Kilauea Volcano, Hawaii

Development of Strong-Motion Observation Network Constructed by NIED

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