Constraints on the source mechanism of harmonic tremors based on seismological, ground deformation, and visual observations at Sakurajima volcano, Japan

2008 ◽  
Vol 170 (3-4) ◽  
pp. 198-217 ◽  
Author(s):  
Sukir Maryanto ◽  
Masato Iguchi ◽  
Takeshi Tameguri
Keyword(s):  
Ground Deformation ◽  
Source Mechanism ◽  
Sakurajima Volcano ◽  
Harmonic Tremors ◽  
Visual Observations

Harmonic tremor model during the 2011 Shinmoe-dake eruption, Japan

2020 ◽  
Author(s):  
Minoru Takeo
Keyword(s):  
Global Analysis ◽  
Lumped Parameter Model ◽  
Source Mechanism ◽  
Phase Portraits ◽  
Order System ◽  
Cross Sectional ◽  
Sustained Oscillations ◽  
Harmonic Tremors ◽  
Model Linearization ◽  
Tremor Model

Summary The Shinmoe-dake volcano started with three sub-Plinian eruptions from 26 to 27 January 2011, followed by a magma effusive stage from 28 to 31 January 2011, and Vulcanian eruptions occurred frequently during 1 to 10 February 2011. During the magma effusive and Vulcanian stages, multiple episodes of harmonic tremors were observed at stations near the summit crater. Although harmonic tremors have been observed at various volcanoes worldwide, the source mechanism remains poorly understood. This paper proposes a source model for harmonic tremors, which is composed of a nonlinear viscous fluid flow in a flexible channel. A simple lumped parameter model is used to consider the process. The dynamics are described by a third-order system of ordinary differential equations using model variables for a cross-sectional area of the constricted segment and the fluid velocities in the upstream and downstream tubes. This model produces various kinds of trajectories for self-sustained oscillations that change the reservoir pressure connected on the upstream channel of the model. Linearization analysis around the stationary point and global analysis employing nullcline planes reveal the mechanism of self-sustained oscillations of the system qualitatively. To consider both the frequency peaks of the harmonic tremor and the characteristics of observed phase spectra, the qualitative characteristics of an observed phase portrait are compared to those of a simulated one. This tremor model simulates the frequency peaks and the phase portraits of typical harmonic tremors observed during the 2011 Shinmoe-dake eruption. Because this model involves several geometrical configuration parameters, it has the potential to reveal the source mechanism of various kinds of harmonic tremors.

Method for Real-Time Evaluation of Discharge Rate of Volcanic Ash – Case Study on Intermittent Eruptions at the Sakurajima Volcano, Japan –

2016 ◽  
Vol 11 (1) ◽  
pp. 4-14 ◽  
Author(s):  
Masato Iguchi ◽  
Keyword(s):  
Linear Combination ◽  
Real Time ◽  
Volcanic Ash ◽  
Ground Deformation ◽  
Discharge Rate ◽  
Sakurajima Volcano ◽  
Seismic Amplitude ◽  
Ash Weight ◽  
Better Than

A method for evaluating the volcanic ash discharge rate by using seismic and ground deformation signals is proposed to obtain this rate in real time for southern Kyushu’s Sakurajima volcano. This volcano repeats vulcanian eruptions accompanying significant ground deformation showing deflation and nonvulcanian type eruptions that emit the minor emissions of volcanic ash associated with volcanic tremors but without significant ground deformation. We examined ground deformation and seismic amplitude as they relate to monthly sums of volcanic ash weight ejected from craters. We found that in monthly sums, both deflation ground deformation and the amplitude of volcanic tremors correlate positively with the weight of ejected volcanic ash. A linear combination of terms for ground deformation, seismic amplitude and a correction factor correlates better than single parameter of deflation or seismic amplitude with volcanic ash weight. The linear combination provides the volcanic ash discharge rate in quasi-real time and the total amount of volcanic ash distributed over a wide area immediately after a volcanic eruption ends.

Volcanic Activity of Sakurajima Monitored Using Global Navigation Satellite System

2018 ◽  
Vol 13 (3) ◽  
pp. 518-525 ◽  
Author(s):  
Masato Iguchi ◽  
Keyword(s):  
Global Navigation Satellite System ◽  
Volcanic Activity ◽  
Ground Deformation ◽  
Satellite System ◽  
Navigation Satellite ◽  
Magma Intrusion ◽  
Sakurajima Volcano ◽  
Global Navigation ◽  
Gnss Network ◽  
Global Navigation Satellite

A dense Global Navigation Satellite System (GNSS) network has been deployed at Sakurajima volcano since 1995 and extends to the surrounding area of the Aira caldera. The ground deformation obtained by GNSS observation corresponds to transient eruptive activity of Sakurajima volcano, which has produced frequent vulcanian eruptions since 1955. Inflation of the volcano was detected prior to the increase in vulcanian eruptions in 1999, and resumption of the eruptions at the Showa crater. Magma intrusion events and an increase in eruptions in late 2009, late 2011, and early 2015 suggest the existence of an open-conduit system from the Aira caldera to the vents at the summit area of the Minamidake cone, through the sub reservoir beneath the older Kitadake cone. Ground deformation induced by sudden dike intrusion is different from that of previous intrusions, as revealed by the dense GNSS network. GNSS data are useful in evaluating and forecasting volcanic activity, and are available to grasp the advection and diffusion of volcanic ash.

scholarly journals Dike Inflation Process Beneath Sakurajima Volcano, Japan, During the Earthquake Swarm of August 15, 2015

2021 ◽  
Vol 8 ◽  
Author(s):  
Midori Koike ◽  
Haruhisa Nakamichi
Keyword(s):  
Ground Deformation ◽  
Earthquake Swarm ◽  
Strike Slip ◽  
Compression Stress ◽  
Magma Intrusion ◽  
Differential Stress ◽  
Sakurajima Volcano ◽  
Dike Intrusion ◽  
Spatiotemporal Changes ◽  
Earthquake Generation

Magma intrusion usually causes seismicity and deformation in the surrounding rock and often leads to eruptions. A swarm of volcano-tectonic (VT) earthquakes associated with rapid dike intrusion in hours occurred beneath Sakurajima volcano on August 15, 2015. We determined the hypocenters and focal mechanisms of the VT earthquake swarm. The distributions of pressure (P)- and tension (T)-axes of the azimuths of the mechanisms are also obtained. The results indicate spatiotemporal changes of the distributions of the hypocenters and P- and T-axes. The hypocenters are distributed at depths of 0.3–1 km and 7:00–10:30 JST, and are located at depths of 0.3–3 km and 10:30–12:00 during which the seismic activity is the largest. At 12:00–24:00, the hypocenters are distributed in shallow and deep clusters at depths of 0.2–1 km and 1.5–3.5 km, respectively. The dike induced rapid ground deformation and is located between the shallow and deep clusters. The strike and opening directions of the dike are parallel to the NE–SW and NW–SE directions, respectively, corresponding to the regional maximum and minimum compression stress. The T-axes of the shallow cluster are distributed parallel to the opening direction of the dike. The P-axes of the deep cluster exhibit a pattern corresponding to the NE–SW direction and the T-axes are distributed in the NW–SE direction. In contrast, a 90° rotated pattern of strike-slip faulting is also observed at the deep cluster at 12:00–24:00, where the P-axes are distributed in the NW–SE direction and the T-axes are distributed in the NE–SW direction. This reflects the change in the stress field due to the dike inflation during the earthquake generation, and indicates that the alteration of stress in the vicinity of the dike due to the dike inflation and VT earthquakes are induced by the differential stress exceeding the brittle fracture strength of the rock. Future seismic and deformation observations in volcanoes will verify whether the spatiotemporal changes of the hypocenters and focal mechanism shown by this study are unique features of rapid dike intrusion.

Integrated Monitoring of Volcanic Ash and Forecasting at Sakurajima Volcano, Japan

2019 ◽  
Vol 14 (5) ◽  
pp. 798-809 ◽  
Author(s):  
Masato Iguchi ◽  
Haruhisa Nakamichi ◽  
Hiroshi Tanaka ◽  
Yusaku Ohta ◽  
Atsushi Shimizu ◽  
...  
Keyword(s):  
Volcanic Ash ◽  
Ground Deformation ◽  
Discharge Rate ◽  
Seismic Energy ◽  
Deformation Monitoring ◽  
Volcanic Plume ◽  
Fall Deposit ◽  
Integrated Monitoring ◽  
Sakurajima Volcano ◽  
Ash Fall

The Sakurajima volcano is characterized by frequent vulcanian eruptions at the Minamidake or Showa crater in the summit area. We installed an integrated monitoring system for the detection of volcanic ash (composed of remote sensing sensors XMP radars, lidar, and GNSS with different wave lengths) and 13 optical disdrometers on the ground covering all directions from the crater to measure drop size distribution and falling velocity. Campaign sampling of volcanic ash supports the conversion of particle counts measured by the disdrometer to the weight of volcanic ash. Seismometers and tilt/strain sensors were used to estimate the discharge rate of volcanic ash from the vents. XMP radar can detect volcanic ash clouds even under visual difficulty because of weather such as fog or clouds. A vulcanian eruption on November 13 was the largest event at the Sakurajima volcano in 2017; however, the volcanic plume was not visible due to clouds covering the summit. Radar revealed that the volcanic plume reached an elevation of 4.2–6.2 km. Post-fit phase residuals (PPR) from the GNSS analysis increased suddenly after the eruption, and large-PPR paths from the satellites to the ground-based receivers intersected each other at an elevation of 4.2 km. The height of the volcanic plume was also estimated from the discharge rate of volcanic ash to be 4.5 km, which is empirically related to seismic energy and the deflation volume obtained via ground deformation monitoring. Using the PUFF model, the weight of the ash-fall deposit was accurately forecast in the main direction of transport of the volcanic ash, which was verified by disdrometers. For further advances in forecasting of the ash-fall deposit, we must consider high-resolution wind field, shape of volcanic plume as the initial value, and the particle number distribution along the volcanic plume.

Failure Analysis Of Buried Gas Pipelines Crossing Seismic Faults

2020 ◽  
Vol 3 (2) ◽  
pp. 781-790
Author(s):  
M. Rizwan Akram ◽  
Ali Yesilyurt ◽  
A.Can. Zulfikar ◽  
F. Göktepe
Keyword(s):  
Ground Deformation ◽  
Warning System ◽  
Strike Slip ◽  
Gas Pipelines ◽  
Steel Pipes ◽  
Seismic Fault ◽  
Fault Parameters ◽  
Dip Angle ◽  
Permanent Ground Deformation ◽  
Recent Earthquakes

Research on buried gas pipelines (BGPs) has taken an important consideration due to their failures in recent earthquakes. In permanent ground deformation (PGD) hazards, seismic faults are considered as one of the major causes of BGPs failure due to accumulation of impermissible tensile strains. In current research, four steel pipes such as X-42, X-52, X-60, and X-70 grades crossing through strike-slip, normal and reverse seismic faults have been investigated. Firstly, failure of BGPs due to change in soil-pipe parameters have been analyzed. Later, effects of seismic fault parameters such as change in dip angle and angle between pipe and fault plane are evaluated. Additionally, effects due to changing pipe class levels are also examined. The results of current study reveal that BGPs can resist until earthquake moment magnitude of 7.0 but fails above this limit under the assumed geotechnical properties of current study. In addition, strike-slip fault can trigger early damage in BGPs than normal and reverse faults. In the last stage, an early warning system is proposed based on the current procedure. 

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