Statistical analysis of tidal effect on non-volcanic earthquake swarm activity in Wakayama Prefecture, southwest Japan

Author(s):  
Kazuki Machida ◽  
Hiroyuki Nagahama ◽  
Jun Muto

<p>Earthquakes occur when the fault stress accumulates to the critical level. External forces such as tidal forces may contributes to the triggering of earthquakes reaching the critical state. For example, in the case of 2011 Tohoku Earthquake, it is reported that there is a correlation between tidal forces and the earthquakes prior to the mainshock. Earthquakes with smaller magnitude are also affected by tidal forces and expected to show correlation with tidal forces.</p><p>Tidal triggering of non-volcanic seismic swarm has not been well documented. So, we choose the Wakayama Prefecture as a targeting region. The cause of the earthquakes occurring in the region is considered to be the presence of the water below the seismogenic depth. The swarm activity continues from 1980s. We analyzed the shallow earthquakes in the northern part of Wakayama Prefecture from 1998 to 2016. We used statistical method called Schuster test to analyze correlation between earthquakes and tidal stress.</p><p>The result of the analysis shows that the earthquakes have a correlation with tidal forces which have the periodicity near the half of the lunar day and the amplitude of the seismicity-rate variation is about 16% of the average earthquake frequency. Correlation between the earthquakes and tidal forces is stronger at the periods when larger number of earthquakes occur. From tidal stress calculation, it is found that both solid tide and oceanic tide are important at this region. This study confirms that most of the earthquakes larger than M<sub>w</sub> 4 in the region occur in the rising period of tidal normal stress or just after the maximum of tidal normal stress. Therefore, tidal observation gives information about the criticality of rocks and temporal heterogeneity of the earthquake occurrence.</p>

2016 ◽  
Vol 43 (3) ◽  
pp. 1092-1099 ◽  
Author(s):  
T. H. W. Goebel ◽  
S. M. Hosseini ◽  
F. Cappa ◽  
E. Hauksson ◽  
J. P. Ampuero ◽  
...  

1975 ◽  
Vol 65 (2) ◽  
pp. 351-357
Author(s):  
John Filson ◽  
Tom Simkin

abstract The Kolomogorov model of event occurrence as developed by Knopoff in earthquake model studies has been applied to a volcanic earthquake swarm. It is shown that in this case, where the rate of seismic energy release was nearly constant in time, the model adequately relates the various seismicity statistics of the swarm.


2013 ◽  
Vol 65 (1) ◽  
pp. 51-55 ◽  
Author(s):  
Yu Nihara ◽  
Keiichi Tadokoro ◽  
Yohei Yukutake ◽  
Ryou Honda ◽  
Hiroshi Ito

2014 ◽  
Vol 25 (5) ◽  
pp. 625 ◽  
Author(s):  
Hsin-Chieh Pu ◽  
Cheng-Horng Lin ◽  
Yu-Chih Huang ◽  
Li-Chin Chang ◽  
Hsiao-Fen Lee ◽  
...  

2012 ◽  
Vol 64 (3) ◽  
pp. 135-142 ◽  
Author(s):  
Masatake HARADA ◽  
Tamotsu AKETAGAWA ◽  
Hiroshi ITO ◽  
Ryou HONDA ◽  
Yohei YUKUTAKE ◽  
...  

2020 ◽  
Author(s):  
daniela tarallo ◽  
Giuseppe Cavuoto ◽  
Vincenzo Di Fiore ◽  
Nicola Pelosi ◽  
Michele Punzo ◽  
...  

<p>In this study we show an 2D Electrical Resistivity Tomography (ERT) survey acquired in Agnano site pre (Dec 5<sup>th</sup>, 2019) and post (Dec 12<sup>th</sup>, 2019) earthquake events occurred in Pisciarelli-Solfatara areas. This earthquake swarm consisted of sequence of 34 earthquakes with Magnitude (Md) -1.1≤Md≤2.8 at depths between 0.9 and 2.3 km. In particular, the earthquake of Dec 06<sup>th</sup>, 2019 at 00:17 UTC with Md = 2.8 (depth 2 km) was the maximum recorded event since bradyseismic crisis began in 2005.</p><p>The ERT survey allow us to identify the main structural boundaries (and their associated fluid circulations) defining the shallow architecture of the Agnano volcano. The hydrothermal system is identified by very low values of the electrical resistivity (<20 Ω m). Its downwards extension is clearly limited by the lava and pyroclastic fragments, which are relatively resistive (>100 Ω m). The resistivity values are increased after the main shock. This increase in resistivity may have been caused by a change in the state of stress and a decrease in pore pressure (subsequent depressurization). Previously to the earthquake, an increase in pressurized fluids has been observed which have reduced the resistivity values. The present observation suggests that the temporal variation of the resistivity values is related to the variation of the pore fluid pressure in the source area of the swarm, facilitated by earthquake and the subsequent fluid diffusion. The combination of these qualitative results with structural analysis leads to a synthetic model of magmatic and hydrothermal fluids circulation inside the Agnano area, which may be useful for the assessment of potential hazards associated with a renewal of fluid pressurization, and a possibly associated partial flank-failure.</p>


2008 ◽  
Vol 113 (B10) ◽  
Author(s):  
Sarah E. Minson ◽  
Douglas S. Dreger ◽  
Roland Bürgmann ◽  
Hiroo Kanamori ◽  
Kristine M. Larson

2010 ◽  
Vol 2 (1) ◽  
pp. 145-160
Author(s):  
P. Kolář

Abstract. There are long time lasting speculations about electro-magnetic emission phenomena (hereafter EME) connected with seismic activity. In the present work we study such relations in West Bohemia region during 2008 earthquake swarm. After brief characterization of the seismic region, we describe recording method and data analysis. We did not observe any direct link between EME and seismic events, however statistical analysis indicates that it could be some increase of EME activity in time 60 to 30 min before an event on periods 17–14 min, some gap in EME activity approximately 2 h after the event and a maximum 4 h after the events (note, that this result qualitatively correspond with observations from other seismic regions). Also global decrease of EME activity with the decay of the swarm activity was observed. However due to incomplete EME data and short time of observation these results must be understand as indication of possible correlation rather than reliable relation.


Author(s):  
Naimisha Vanik ◽  
D.M. Maurya ◽  
Mohamedharoon Shaikh ◽  
Akash Padmalal ◽  
Prabhuti Tiwari ◽  
...  

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