SCG15-01

Room:203

Time:May 24 15:15-15:35

Electromagnetic fields in the solid material neighbouring porous media
REN, Hengxin1∗ ; HUANG, Qinghua2 ; CHEN, Xiaofei1
1School of Earth and Space Sciences, University of Science and Technology of China, Hefei, China, 2 Department of Geophysics,
Peking University, Beijing, China
Numerous studies reported that there are electromagnetic(EM) wave-fields associated with seismic waves. The electrokinetic
effect, as one of the most possible mechanisms resulting in the coupling between the seismic and EM wave-fields, has attracted
wide attention in the area of seismoelectromagnetism. The numerical experiments have confirmed that a finite fault in porous
media can induce seismoelectromagnetic signals. The characteristics and the magnitude of amplitudes are consistent with thoseobserved in natural earthquakes. However, all the used models consist of porous materials. In this work, we carried out numericalexperiments to investigate the situation in the layered model composed of solid and porous materials together. It is found there
are two kinds of EM waves in the solid material, the homogeneous and inhomogeneous EM waves. The former one is generated
by the direct EM waves radiated from the source or the normal incident seismic waves at the interface between the solid and theporous media. The latter one is generated by the oblique incident seismic waves whose horizontal wavenumber is greater thanthe EM wavenumber in the solid media. The inhomogeneous EM waves propagate in the horizontal direction and decrease when
the distance to the interface increases. For the solid area which is close to the interface (e.g., within 200m), the inhomogeneous
EM waves behave very simliar with the co-seismic EM signals in the pure-porous model.
Keywords: electrokinetic effect, the coupled seismic and electromagnetic fields, solid material neighbouring porous media,
converted electromagnetic waves generated at the interface

1/1

SCG15-02

Room:203

Time:May 24 15:35-15:50

Exclusion of metal contact noise in the experiment of radio wave emission due to rockfracture
TAKANO, Tadashi1∗ ; HANAWWA, Rikuya1 ; KAWATA, Yuki1 ; SHIBATA, Kuniaki1 ; SAEGUSA, Kenji1
1

Nihon University, College of Science and Technology

1. Introduction
Formerly, the radio wave emission due to rock fracture was found at the frequency of 300 MHz to 22 GHz [1]. This phenomenon gathered much attention, as a possible tool to measure or even to predict a rock fracture in nature, which may be anearthquake or volcanic eruption [2] [3].
On the other hand, it was confirmed that radio waves were generated when metallic parts in the experiment system collided
each other [4]. It is inferred to be caused by electric discharge due to charging effect of metallic parts by contact or collision [5].
Therefore, it is absolutely needed to discriminate these signals that were not originated by rock fracture itself.
Recently, we have remodeled the experiment system, of which all metallic pars are electrically shorted. Accordingly charging
effect of the metallic parts is prevented in the rock fracture process. This paper describes the constitution of the experimental
system and measured results.
2. Experimental system
The experimental system is composed of a destruction subsystem and a signal detection subsystem. The destruction system
consists of a hydraulic pressing machine, a base plate, a ceiling plate, connecting poles, bolts and nuts. Theses all parts are connected with 24 twisted wires of 5 mm width and 1 mm thickness and with 9 twisted wires of 2 mm width and 0.5 mm thickness
by screwing or soldering.
The signal detection subsystem is the same as the former one [4]. At each frequency of 1 MHz-, 300 MHz-, 2GHz-, and 18
GHz-bands, an antenna, a low noise amplifier and a filter are installed. The destruction and emission phenomenon is instantaneous so that a special recorder and a triggering system to activate a main memory are inevitable.
The rock specimens were quartzite, granite, gabbro, and basalt.
3. Measured results
We obtained the following results.
(1) In all rock cases, radio wave at 300 MHz was observed simultaneously with the destruction.
(2) Especially, in the case of quartzite, a weak 18GHz signal was observed in addition to a strong 300MHz. These signals
occurred simultaneously.
(3) Cylinders of mortar were used as a specimen. But signal was not detected.
(4) When the rock debris, a laid blue sheet or a vinyl cover touched each other, radio waves were observed. The generated
frequencies are strong 300MHz, weaker 2GHz, and the weakest 18 GHz, as is different from the case of rock fracture. The causeof the emission is esteemed to be charging and subsequent discharges.
(5) In particular time, we observed noises from environment. The signals, however, do not include 2GHz nor 18 GHz components.
4. Conclusion
All metallic parts in the destruction subsystem were electrically shorted to prevent emission due to discharge. Even so, radiation was observed in various rock cases so that the emission due to rock fracture is confirmed.
References[1] K. Maki, T. Takano, E. Soma, K. Ishii, S. Yoshida and M. Nakatani, ”An experimental study of microwave emission fromcompression failure of rocks” (in Japanese), Jour. of the Seismological Society of Japan, vol.58, no.4, pp.375-384, 2006.
[2] T. Takano, T. Maeda and S. Yoshida, ”Experiment and Theoretical Study of Earthquake Detection Capability by Means ofMicrowave Passive Sensors on a Satellite”, IEEE Trans. Geoscience And Remote Sensing, Vol.6, No.1, pp.107-111, 2009.
[3] Y. FUJINAWA, Y. NODA, K. TAKAHASHI, M. KOBAYASHI, K. TAKAMATSU, and J. NATSUMEDA, ”Microcracks
Associated with Natural Earthquakes”, Programme and Abstracts of Fall Meeting, Seismological Society of Japan, vol.2013,
p.81, October 2013.
[4] R. HANAWA, H. KAWATA, K. SHIBATA, K. SAEGUSA, and T. TAKANO, ”Radio Emission Experiment by Metal Contact with the Rock Fracture Experiment System” (in Japanese), IEICE Society Conference, B-1-22, Tokushima, September 2014.
1/2

SCG15-02

Room:203

Time:May 24 15:35-15:50[5] T. Takano, R. Hanawa, K. Saegusa, and H. Ikeda, ”Radio Wave Generation by a Collision or Contact between Various
Materials”, AGU Fall Meeting, MR23B-4354, San Francisco, Dec. 17, 2010.

Keywords: rock fracture, radio wave, metal contact, noise, parts, short

2/2

SCG15-03

Room:203

Time:May 24 16:15-16:35

Medium effect on the characteristics of electromagnetic signals accompanying with seismic waves
HUANG, Qinghua1∗ ; REN, Hengxin2
1

Peking University, 2 Univ Sci Tech China

Recently developed numerical simulation technique can simulate the coupled seismic and electromagnetic signals for a double
couple point source or a finite fault planar source. Besides the source effect, the simulation results showed that both medium
structure and medium property could affect the coupled seismic and electromagnetic signals. The waveform of coupled signals
for a layered structure is more complicated than that for a simple uniform structure. Different from the seismic signals, theelectromagnetic signals are sensitive to the medium properties such as fluid salinity and fluid viscosity. The results may provide
some insights of understanding the difference in the detectability of co-seismic electromagnetic signals in different geologicalregions.
This study is supported partially by the National Natural Science Foundation of China (41025014) and the National Basic
Research Program of China (2014CB845903).
Keywords: Electrokinetic effect, co-seismic electromagnetic signals, medium effect, a double couple point model, a finite fault
planar model

1/1

SCG15-04

Room:203

Time:May 24 16:35-16:50

Properties of seismo-electric variations induced by microcracks in the nucleation stage ofearthquake occurrence
FUJINAWA, Yukio1∗ ; NODA, Yoichi2
1

Mieruka Bousai Inc., 2 Tierra Tecnica Ltd

Characteristics of dominant three phases ( Pf , S, EM ) of seismoelectrical waves have been investigated using waveformwhich are suggested to be induced by microcrack in the nucleation stage of the 2011 Tohoku Earthquake (Fujinawa et al ., 2013).
Twelve B-type events having clear P, S phases and apparent EM phase with dominant frequency 500 Hz have been selected fromthe catalog of B type events. Slight traces of EM phases are searched at around the origin time. We estimated focal distances of
those events using S-P time assuming the P and S wave velocity, which are corrected on the basis of arrival time of the identified
EM phase. The corrected velocities are well in agreement of the measured logging data at the borehole. The accumulated numberof events is found to follow the Gutenberg- Richter relation with the b ?value equal 0.7, indicating that the B-type events areof natural micro-earthquake. We can conclude that the seismoelectric mode of the SES related with natural earthquake can beobserved by using high sensitive sensor.
The electric strength of fast- P, S, and EM modes of the shear tensile type events are compared with each other. Averagesof observed amplitude order as As >Apf >Aem, which is partly different from those of previous numerical simulations (e.g .,Gao and Hu, 2010). Those amplitudes are analytically estimated on the basis of the seismo-electromagnetic formulation of Pride(1994) assuming the isotropic homogeneous medium filled with confined solvent. The force field is the double couple model of
Gao and Hu (2010) in consistent with the hypothesis that the source is microcrack. The typical value for physical parameters ofelastic material, solvent and the streaming coefficient for seismic frequency result in the ordering Apf >As >Aem, a little bit
different from the observational result. The contradictory relation between the observed result and numerical simulation may be
attributed to the assumed whole space model other than the half space model.
Overall agreement between the observed and estimated results suggest that, 1) pulse-like events of B-type detected before the
Tohoku Earthquake are induced by rupture of microcrack in the nucleation period of main shock, 2) observed phases of waveform( Pf , S, and EM) are corresponding to co-seismic Pf, S and free electromagnetic wave in the unified formulation, 3) the SES
phenomena in the field can be analyzed by the formation.
Precursory phenomena of earthquake have been investigated by analyzing seismic activity, crustal deformation, groundwater
anomalies, and electromagnetic anomalies. Present finding of the overall agreement of the observation and estimation on suggeststhat those multiple kind of phenomena can be discussed by means of the Pride’s formation of on the basis of concept that thosephenomena are induced by variety of the cracks taking place in the nucleation period. We have already impressive observationof magnetic ULF band anomalies (Han, 2012) occurred simultaneously with the slow slip at deep plate boundary by means ofhigh sensitive seismometer (Ozawa et al., 2003). Many of observational electric anomalies (Hayakawa and Fujinawa, 1994) canbe more satisfactory interpreted on the basis of the unified scheme. Multidisciplinary approach on the basis of the unified theory
is expected to open new window for practical earthquake prediction methods as well as for geophysical survey. For instance we
can investigate the fluid motion associated with fracture in a porous medium as conducted in the laboratory (Haas et al ., 2013).

Keywords: seismo-electromagnetics, short-term forecasting, micro-crack, porous medium, Electrical properties, Acoustic property

1/1

SCG15-05

Room:203

Time:May 24 16:50-17:05

The Mechanism of the Pre-seismic Changes of the Tidal Deviation of Groundwater Levelin Hualien City, Taiwan
LAI, Wenchi1∗ ; WANG, Shihjung2 ; HSU, Kuochon3 ; SHIEH, Chjenglun1
1

Disaster Prevention Research Center, National Cheng Kung University, 2 Georesources Research Center, National Cheng Kung
University, 3 Department of Resources Engineering, National Cheng Kung University
The different response by various natural stimuli and processes (tidal force, barometric loading, ground shaking and crustal
strain) were used as the elements of the hydraulic information in the earthquake induced groundwater level changes. Using
the ocean tidal force to act as naturally recurring stimuli to provide a sufficiently varied distribution of excitations in time andspace, and represented the hydro-geological changes responses to the earthquake processes. The purposes of this study are
to analyze the recently observation results of the earthquake induced tidal deviation of groundwater level in observation wells
around Hualien city, eastern Taiwan. The analysis of the tidal responses and the atmospheric pressure responses also will be used
to estimate the mechanical properties of the aquifer. Comparison the observation between the sea level and the groundwater levelchanges in the each event, offers the opportunity to discussion the possible mechanism of the hydrologic response to earthquake.
Curiously pre-seismic groundwater level changes in the pattern of tidal deviation occurred repeatedly in several local seismic
events nearby the Hualien City. Poroelastic model been used to act as the simulation tool to fit to the pre-seismic groundwaterlevel changes. The results shows groundwater preseismic change could be simulated by a recharge or discharge at a fault zone
with poroelastic model. The numerical results could support our conceptual model with a permeable fault zone between sea
loading and groundwater responses. Our numerical model provides some information for the preseismic mechanism but moreinvestigations are required.
Keywords: Groundwater, Permeability Structure, Pre-seismic

1/1

SCG15-06

Room:203

Time:May 24 17:05-17:25

Seismoelectric Interferometry
GROBBE, Niels1∗ ; SLOB, Evert1
1

Delft University of Technology

The seismoelectric effect is a very interesting and complex physical phenomenon, dealing with the subsurface coupling between mechanical poroelastic wavefields and electromagnetic diffusive fields. Therefore, the seismoelectric method can provide
us with both seismic resolution and electromagnetic sensitivity at the same time. In addition, several studies have shown that theseismoelectric method can provide supplemental information about porosity and permeability, or on pore–fluid properties suchas viscosity. These features do not only make seismoelectrics a worthwhile phenomenon to study for exploration purposes, butalso for e.g. the field of earthquake mechanisms and risk analysis. Two types of seismoelectric coupling can be distinguished:1) localized coupling generating an electromagnetic field that is present inside the seismic wave and travels with seismic velocity, the so-called coseismic field.
2) An independently diffusing electromagnetic field with electromagnetic velocity, providing us with information at depth.
This is referred to as the seismoelectric conversion (or interface response).
At present, the key challenge for seismoelectrics is its measurability in the field. Due to the very weak signal to noise ratioof especially the second-order seismoelectric conversion, the events are often not detectable. In order to make seismoelectrics
applicable in the field, we need to find ways to improve the signal to noise ratio of this second order effect. From seismic
interferometry, we know that by cross–correlating recorded fields, virtual source responses can be simulated. In this process,stacking inherently takes place thereby possibly enhancing the signal-to-noise ratio of the records. We here present initial resultsof applying interferometric principles to seismoelectric phenomena. Can we indeed retrieve the desired seismoelectric virtual
source responses that we are after, by cross-correlating selected responses due to boundary sources of a certain type (mechanical or electrical)? We explore the area of seismoelectric interferometry using our analytically based, numerical modeling code
ESSEMOD (ElectroSeismic and Seismoelectric Modeling). Acknowledgements: Shell–FOM project, ’Innovative physics for oil
and gas’.
Keywords: Seismoelectric, Electroseismic, Interferometry, cross-correlation

1/1

SCG15-07

Room:203

Time:May 24 17:25-17:40

Feasibility study of characterizing crustal cracks by EMR in the VLF band using interferometry
LIU, Lanbo1∗ ; HUANG, Qinghua2
1

Department of Civil and Environmental Engineering, University of Connecticut, 2 Department of Geophysics Peking University

In this paper we present the three-dimensional (3D) numerical simulation results aimed to shed a light on the feasibility ofmapping the density and orientation of crustal cracks by looking into the features of electromagnetic radiation (EMR) from cracks
using interferometry from a surface observation array. We use 3D finite difference time domain (FDTD) technique to conduct thenumerical modeling. The cracks are statistically generated with specified density, size, orientations, and electromagnetic (EM)properties. The measuring points are placed on the earth surface and can be distributed in any arbitrary fashion to investigate theoptimistic configuration of the field observation arrays. The objective of this numerical test is two-fold:1) Investigate the EMR efficiency on the surface by looking into different physical mechanisms (such as charge separation
processes between (OKeefe and Thiel, 1995) or along (Gershenzon et al., 1986) the crack walls associated with micro-cracking;2) crack-induced movement and reorientation of dislocations (Misra and Gosh, 1980; Slifkin, 1993); 3) the surface vibrationalwave model of Frid et al. (2003) and Rabinovitch et al. (2007)).
2) Investigate the influence of strong radiation from VLF transmitters on using EMR for tectonic and earthquake studies.
As the existing preliminary observations (e.g., Krumbholz, 2010; Krumbholz et al. 2012) have shown, the hope of using EMR
to determine the horizontal principal stress orientation at one location by looking into the EM amplitude from a single station
alone is diminished. This motivates us to look into the interferometry approach to eliminate the strong influence of active VLF
transmissions.

Keywords: seismoelecgtric, crustal cracks, interferometry, VLF, electromagnetic radiation, numerical simulation

1/1

SCG15-P01

Room:Convention Hall

Time:May 24 18:15-19:30

Towards Seismoelectric Inversion: Sensitivity Analysis using Resolution Functions
GROBBE, Niels1∗ ; MAAS, Peter1 ; SLOB, Evert1 ; MULDER, Wim2
1

Delft University of Technology, 2 Shell Global Solutions International BV

When a mechanical wavefield propagates through a porous, fluid-filled medium, a complex physical phenomenon called theseismoelectric effect can occur. Due to the presence of an electrical double layer at the microscale, coupling between the mechanical wavefieldand electromagnetic fields can occur. Pride (1994) has developed a set of governing equations that describes the seismoelectriceffect using Biot’s poroelasticity equations coupled to Maxwell’s electromagnetic equations. Coupling effectively takes place at
two locations:1) Inside the seismic wavefield, copropagating with the seismic wave velocity and therefore referred to as the coseismic field.
This field provides us with local information in the vicinity of the receivers.
2) At locations where contrasts in medium parameters occur (for example interfaces) an independently diffusing electromagnetic field is generated, referred to as the interface
response field or seismoelectric conversion. The seismoelectric method tries to take advantage of this subsurface coupling
as a geophysical tool for exploration or monitoring purposes, as well as for borehole applications. Besides providing us withseismic resolution and electromagnetic fluid–sensitivity at the same time, several studies have also shown that seismoelectricfields can provide us with supplemental information about porosity, permeability and pore-fluid properties such as viscosity. The
seismoelectric method can potentially be used for the detection and monitoring of oil/water contacts, several (near–)borehole
applications and the monitoring of aquifers.
However, the seismoelectric effect is described by a combination of many (often mutually related) subsurface parameters.
Therefore, inversion of seismoelectric data for a specific parameter is costly and solving for such a parameter uniquely might
be even impossible. By carrying out sensitivity analyses prior to inversion, we can investigate whether the measured fields are
actually sensitive to the parameter(s) of interest. In addition, sensitivity analyses can provide information about the optimal acquisition design or help us investigating time–lapse perturbations. We will start by explaining the theory of resolution functions
using a seismoelectric example. We will derive the seismoelectric resolution function for inversion for a bulk density contrast. We
will compute this resolution function as the least-squares solution to the normal equation. We will demonstrate the effectivenessof this method by first carrying out a purely electromagnetic sensitivity analysis for a point perturbation in conductivity. These
results will be compared with literature results. As a next step, we investigate the electromagnetic sensitivity to point scatterers
above and below highly conductive layers. Finally, we will present the results of the fully–coupled seismoelectric sensitivity
analysis for a bulk density contrast, using single–frequency multicomponent line data.
Keywords: Seismoelectric, electromagnetic, resolution function, sensitivity analysis

1/1

SCG15-P02

Room:Convention Hall

Time:May 24 18:15-19:30

Application Prospects of SKZ-1 4-component borehole strain meter
KONG, Xiangyang1∗ ; SU, Kaizhi2 ; FUJINAWA, Yukio3
1

Earthquake Administration of Shandong Province,china, 2 Institute of Crustal Dynamics,CEA,china, 3 Risk Control Associations

High sensitivity borehole strain meter has good dynamic performance, work stability, anti-interference ability in detecting theregional crustal activity. The structure using four sensing elements that were set at intervals of 45 degree can have a simple”reliability test formula of measurement data” to realize the real-time inspection of data reliability. This method of work has
become an important detection means of multi-component borehole strain observation in Mainland China. The structure of
the new model introduced by this paper has been confirmed that it can obviously improve the mutual verification result ofstrain measurement data because the important improvements have been made on displacement transfer structure of underground
instrument, and the borehole strain meter has got two pre-seismic anomaly information in experimental observation in ZhaoTongarea, YunNan. Now the types of equipment submitted to this conference is expected participants to consider if it can be used inelectromagnetic wave observation station network and become an auxiliary observation means that is matching.
The instrument feature are that it uses four sensing elements that were set at intervals of 45 degree and checking formula issimple and clear: U1+U3=U2+U4. Reliability of observation has been obviously improved because four elements are embeddedin the 8 narrow ribs. Cross check degree of the data has reached 0.99.
Preliminary results: 1. M5.7 YiLiang earthquake occurred (longitude 104.00, latitude 27.5) at 11:19 on September 7th, 2012.
Seven days before the earthquake, obvious strain anomaly of four directions appeared at the same time in YiLiang Seismic Station
which epicenter distance is 15.5km. But in DaGuan Seismic Station which epicenter distance is 30km, correlation coefficient of
the two surface strain curve is 0.99 or so, there was no significant association with this earthquake. NS and NW data signals of
the borehole strain meter appeared low frequency noise 11-17 minutes before the M5.7 DaGuan earthquake, and the earthquake
occurred two minutes after the end of noise. In this earthquake, what is difficult to understand is that the low frequency signal
curve shape is different between the NS curve and NW curve. Cycle of NS is about 15s and the cycle of NW is about 60s. But
NE, EW data curve did not appear similar situation and the relationship between the low frequency data of four components
did not conform to checking formula. The cause of this kind of signal is unclear but it may be a extremely important clue. We
suspect that it may be connected with the underground electromagnetic signal because it doesn’t conform to checking formula.
2. The LuDian M6.5 earthquake occurred on August 3, 2014, epicenter was located 26km southwest of LuDian Seismic Station.
Except that strain data appeared changes 3 days before the earthquake, the correlation coefficient of surface strain have different
values in different stages of earthquake.

Keywords: Borehole strain, Observation technology, Pre-seismic anomaly information

1/1