thThe 14 World Conference on Earthquake Engineering
October 12-17, 2008, Beijing, China

Ground Motion Estimation in the Near-source Region during the 2007
Niigata-ken Chuetsu-oki Earthquake
1

2

3

4

5

Masumi Yamada , Sun-Cheon Park , Yasuhiro Hayashi , Takeshi Morii , Hiroshi Kambara ,6
7
Yoshihiro Onishi and Hidemaru Shimizu
1

Assist. Professor, Pioneering Research Unit for Next Generation, Kyoto University, Uji, Japan
2
Researcher, Korea Meteorological Administration, Seoul, Korea
3
Professor, Department of Architecture and Architectural Eng., Kyoto University, Kyoto, Japan
4
Assist. Professor, Department of Architecture and Architectural Eng., Kyoto University, Kyoto, Japan
5
Research Engineer, Institute of Technology, Shimizu Corporation, Tokyo, Japan
6
Researcher, Geo-Research Institute, Osaka, Japan
7
Research Engineer, National Research Institute for Earth Science and Disaster Prevention, Miki, Japan
Email: masumiyamada@hotmail.com
ABSTRACT :We performed a damage survey of temples and shrines near the source region of the 2007 Niigata-ken
Chuetsu-oki earthquake to estimate the distribution of strong ground motions. We constructed a function toestimate PGV (peak ground velocity) from the damage rank of main hall of temples and shrines, and estimatedthe PGV distribution in the source region. From our results, the PGV in the most of the Kashiwazaki basin
exceeds 100cm/s. This PGV distribution agrees with the PGV estimated from the attenuation relationship andsurface soil amplification. The conventional estimation method using the ratio of overturned tombstones
underestimates the PGV in the basin.
KEYWORDS:

Peak Ground Velocity, Source Region, Ratio of Overturned Tombstones,
Structure of temples and shrines, 2007 Niigata-ken Chuetsu-oki Earthquake

1. INTRODUCTION
The 2007 Niigata-ken Chuetsu-oki earthquake (Mw 6.6, Mjma 6.8)[1] produced severe damage in buildings, civil
structures, soil deformation in the near-source region. The Kashiwazaki-Kariwa Nuclear Power Plant, which islocated at 15km south of the epicenter, was subjected to strong shaking, and the strong motion record observed at
the reactor was greater than the design load.
Five strong motion records of the 2007 Niigata-ken Chuetsu-oki earthquake were recorded within 10
kilometers from the source fault; 4 strong motion stations and the nuclear power plant site[2] (Figure 1). The
observed PGV (peak ground velocity) varies from 50 to 100 cm/s (Table 1), which shows the inhomogeneous
velocity distribution around the near-source region. Moreover, the predominant period of the waveforms has large
variety depending on the location of the stations. For example, the waveform in the downtown Kashiwazakishows very long period (longer than 2 seconds) ground motion and strong nonlinearity of the soil. The
sedimentary soil structure in this region was very complicated[3] and it greatly affects to the ground motion
amplification.
Our group performed a damage survey of temples and shrines near the source region of the 2007
Niigata-ken Chuetsu-oki earthquake from 25th to 27th of July, 2007 and surveyed the damage rank of the structure
and ratio of overturned tombstones. It is conventional to estimate the ground motion from the ratio of overturned
tombstones and damage rank of the structure, and various methods are proposed in the past research[4-5]. Although
there are many difficult problems in estimating ground motions in this region due to the complicated sedimentary
structure and soil non-linearization, we tried to evaluate how much ground motion we can estimate from thesurvey results based on the empirical relationship between the ground motion and damage. This paper focuses on
the following topics:- Construct an empirical function to estimate peak ground velocity from the damage rank of main hall ofth

The 14 World Conference on Earthquake Engineering
October 12-17, 2008, Beijing, China-

temples and shrines, and characterize the average PGV distribution in the near-source region.
Apply the conventional relationship of the ratio of overturned tombstones to the survey results, compare withthe observed PGV, and evaluate the applicability of the conventional relationship to this earthquake.
Estimate the near-source PGV from the attenuation relationship and compare with the PGV distribution
computed from the survey results.

(a) damage rank D3

Figure 1 Observation sites andgeography of the near-source region.

(b) damage rank D4
Figure 2 Examples of the damage rankof a main hall of temples and shrines.

2. SURVEY METHOD
We performed a damage survey of temples and shrines in the east side of the near-source region. The survey area
covers from Izumozaki to Kashiwa, 30km*20km wide in the north-south and east-west direction, respectively(Figure 1). The total number of the sites we surveyed was 212 shrines, temples and graveyards. More detailnumber is; 74 temples and shrines with graveyards, 81 temples and shrines without graveyards, and 57 sites with
only graveyards. A group of two or three people surveyed each site and recorded the damage condition. The
latitude and longitude of the sites were measured by a handy GPS.
Damage rank (DR) of the structures such as main halls and belfry (a building in which a bell is hung) was
categorized in D0 (no damage), D1-D2 (little damaged), D3 (severely damaged; see Figure 2), D4-D5 (totallycollapsed; see Figure 2) based on the Wooden structure damage pattern by Okada and Takai[6]. Internal damage
which cannot be recognized from the outside was not evaluated. In graveyards, the tombstones with about 80cm
height were selected and the ratio of the overturned tombstones against the total number of tombstones wascounted. In some graveyards, 2-3 tombstones were selected arbitrarily and measured the length, width andbreadth. Graveyards with tombstones less than 10 and with tombstones repaired after the earthquake were
removed from the data analysis. We also recorded the damage rank of objects such as shrine gates and statues.

thThe 14 World Conference on Earthquake Engineering
October 12-17, 2008, Beijing, China

3. RELATIONSHIP BETWEEN OBSERVED RECORDS AND DAMAGE RANK
3.1. Frequency Characteristics of the Observed Seismograms
In order to characterize the relationship between PGV and damage rank of main hall of temples and shrines, thedamage rank is calibrated by the observed record in the near-source region. The observed records used for thecalibration are 5 stations; JMA Izumozaki (Izumozaki), Nishiyama-branch of Kashiwazaki city hall (Nishiyama),
Kariwa town house (Kariwa), K-NET Kashiwazaki (NIG018, in the Kariwa city hall), service hall of theKashiwazaki-Kariwa nuclear power plant (KKNPP). The frequency characteristics of each record are shown in
Table 1. The records observed at the 1st and 5th reactors of the KKNPP are also included in the Table 1. Thesestations are removed from our analysis since we do not have an access to these sites to perform damage survey inthe surrounding area.
Since each record was recorded by the accelerometer, the DC offset of the accelerograms was corrected bysubtracting the mean of the pre-event portion. The baseline correction scheme[7] was applied and we obtained
appropriate velocity records by the single integration. The larger maximum amplitude of horizontal NS and EW
components is used as the PGV. The same component as PGV is selected for the values of PGA. The
predominant period of the ground motion is computed by the following equation:
Te= 2π / (PGA / PGV)(1)

ARV will be explained in the section 4.1. The ambient noise was measured at four sites except the KKNPP, andthe predominant frequency of the H/V spectrum from the ambient noise measurement is also shown in the Table.
The predominant frequency of the Kariwa and K-NET Kashiwazaki was as long as 1.25 seconds, and it is clearly
different from that of Nishiyama. There is no clear peak in the spectrum of the Izumozaki record.
Figure 3 shows the horizontal acceleration response spectrum of each record. The records of the Izumozaki
and Nishiyama shows clear peak at around 0.5 second and quickly falls down in longer period component. On theother hand, the three records in Kashiwazaki basin (Kariwa, K-NET Kashiwazaki, KKNPP) show the large
response from 1 to 3 seconds.
3.2. The relationship between observed records and damage rank of main hall of temples and shrines
In this section, the relationship between observed records and damage rank of main hall of temples and shrines
around the seismic stations is analyzed. We defined the circle with the constant radius from the station as thestation neighborhood. The size of the radius is 2km. This size is determined so that we have enough samples in
the circle, as well as it is sensitive enough to characterize the geographical and topographical changes. The
station neighborhood is shown in Figure 1 as an open circle. At least 9 survey sites are included in the stationneighborhood except Izumozaki and KKNPP. Although the number of the survey sites near Izumozaki is only
two, the result (D2:1 structure, D0-D1:1 structure) agrees with the damage condition in that region. As for
KKNPP, most of the neighborhood is covered by the nuclear power plant site, so we cannot access the area.
Figure 4 shows the relationship between observed PGV (PGVobs) and the D3 and D4 damage ratio of themain hall of temples and shrines. Here, D3 (D4) damage ratio means the ratio of the damaged buildings subjectedto the damage of greater equal to D3 (D4) level against the total buildings. D3 and D4 damage ratio tends toincrease as the PGV increases. This relationship is regressed by the cumulative probability density function of thelognormal distribution Φ(x) and a PGVobs - damage ratio function is obtained. The probability (PDR) that the main
hall is subjected to the damage greater than DR at some PGV is expressed by using the average λ and thestandard deviation ζ of ln(PGV);PDR(PGV) ＝ Φ((ln(PGV)-λ) / ζ)(2)

λ and ζ are determined by the least square method with probability paper. The obtained regression coefficients
are;

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The 14 World Conference on Earthquake Engineering
October 12-17, 2008, Beijing, China

D3 damage ratio: λ＝4.61, ζ＝0.31
D4 damage ratio: λ＝4.81, ζ＝0.19
These regression curves are added in Figure 4.
Table 1 List of the strong motion records.
PGA (cm/s2) PGV (cm/s)
494
48

Te (s)

ARV

T(s) from ambient noise

0.61

1.19

unclear

78

0.58

1.56

0.31

465

121

1.63

2.35

1.25

6.1

437

130

1.87

2.09

-

138.558

6.4

668

110

1.03

2.09

1.25

No.

Station nameLatitudeLongitude

Intensity

1

Izumozaki

37.532138.710

5.9

2

Nishiyama

37.457138.667

6.2

841

3

Kariwa37.422138.622

6.0

4

KKNPP

37.424138.597

5

K-NETKashiwazaki

37.3726

1st reactor of KKNPP

37.424138.597

6.5

890

167

1.18

2.09

-

7

5th reactor of KKNPP

37.436

138.602

6.4

1223

90

0.46

2.09

-

2

Acc. Res. Spectrum (cm/s )3000

Izumozaki-EW
Nishiyama-NS
Kariwa-NS
KKNPP-EW
K-NET Kashiwazaki-NS

2500
2000
1500
1000
500
0
0

2

Period (s)4Figure 3 Response spectrumof acceleration.

6

Figure 4 PGVobs and DR of main halls.

Figure 5 PGVobs and ratio of theoberturned tombstones.

Figure 7 PGVobs and PGVa.

Figure 6 PGV estimated DR of main halls and ARV distribution.

Figure 8 PGVt and PGVa.

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The 14 World Conference on Earthquake Engineering
October 12-17, 2008, Beijing, China

3.3. The relationship between the observed records and ratio of overturned tombstones
Figure 5 shows the relationship between the observed PGV (PGVobs) and ratio of overturned tombstones. The “x”
symbol is the ratio of overturned tombstones of each site, and solid “o” symbol is the average weighted by the
number of the tombstones of each site. The broken line represents the empirical function (λ＝4.41, ζ＝0.4)
proposed by Kaneko and Hayashi[5]. In general, the ratio of overturned tombstones has a good correlation with
PGV. However, this figure does not show the positive correlation.
According to Kaneko and Hayashi[5], the ratio of overturned tombstones shows a good correlation with PGV
if the equivalent natural period of the tombstone (Tb) is greater than the predominant period of the ground motion(Te). The equivalent natural period of the tombstone (Tb) is defined by the following equation:
0.5

1.5

Tb = H (1 + B/H) /15.6(3)where H is the height (cm) and B is width (cm) of the tombstone. We selected samples of the tombstones
randomly and measured B and H. The average H is 76cm, B/H is 0.40, and Tb computed from the average aspectratio is 0.93 second. The station with predominant period of the PGVobs less than 0.93 was only Izumozaki andNishiyama (see Table 1), so the empirical function by Kaneko and Hayashi[5] cannot be applied to some regions.
Figure 5 shows the PGV estimated from the ratio of overturned tombstones underestimates observed PGV in
the neighborhood of the station with Te greater than 0.93 second. However, the Nishiyama whose Te was shorter
than 0.93 second does not fit the empirical function by Kaneko and Hayashi either, which means the empiricalfunction cannot be applied in this region. Although the empirical function of the ratio of overturned tombstone
for the ground motion with predominant period longer than 1 second was analytically shown in Kaneko andHayashi (2000), it has not been observed in the past earthquake damage. Figure 5 shows the limitation of theempirical function of the ratio of overturned tombstone to the long period ground motion in the real data.
4. GROUND MOTION ESTIMATION IN THE NEAR-SOURCE REGION
4.1.PGV Estimation from the Attenuation Relationship and ARVIn order to check the accuracy of the PGV estimation, the estimated PGV is compared with the PGV computedfrom a different method. We use the attenuation relationship of PGV[8] and velocity amplification factor (ARV)
computed from the average S-wave velocity in the upper 30m of the ground (AVS30). We follow themethodology used by Fujiwara et al.[9]. The PGV estimated by this method is called as PGVa.
The fault section to compute the fault distance (a minimum distance between station and fault) is 3D
west-dip model used for the waveform inversion by Aoi et al.[10] Since the attenuation relationship cannot beapplied to the region very close to the fault, the minimum fault distance is set to be 3km. In order to compute theARV, The 250m mesh geography data in Niigata[11] and 50m mesh topographical data[12] were used based on themethod proposed by Matsuoka et al.[13]Figure 6 shows the ARV distribution in the near-source region. The black rectangle is fault surface by Aoi etal., [11] and the black curve is a contour of ARV 2.0. The high ARV region surrounded by the contour is classified
as a back marsh, sand dune, delta, or coastal lowland, which cover most of the Kashiwazaki basin.
Figure 7 shows the relationship between PGVobs and computed PGVa. PGVa of most of the stations agrees
with the observations except Izumozaki. There is a possibility that the slip on the fault around Izumozaki wassmall, and that produced the smaller ground motion. Since the method used by Fujiwara et al. considers only thefault distance and surface soil amplification, the estimated PGV distribution may not be true depending on theslip distribution. We admit it is difficult to estimate the true PGV distribution only from the fault distance andsurface soil information, but this method characterizes PGV of most of the near-source stations.
It is difficult to determine the dip angle of the fault surface from strong motion records only[10]. We tried tocompute the PGVa from east- and west-dip fault surfaces, and the west-dip fault surface showed the better
correlation to the observed PGV (see Figure 7). Therefore, we use west-dip fault surface in this paper.

th

The 14 World Conference on Earthquake Engineering
October 12-17, 2008, Beijing, China

4.2.PGV Estimation from the relationship between observed records and damage rank of main hall of temples
and shrines
The damage ratio of main hall of temples and shrines are shown as circles in Figure 1. Severely damagedbuildings (D3-D5) are distributed in the area from downtown Kashiwazaki to Kariwa. This area corresponds tothe dimension of the Kashiwazaki basin, which suggests that the entire basin was subjected to strong shaking. In
the severely damaged area, foundation damage, soil deformation, and sand injection due to the liquefaction werealso observed. The records of the K-NET Kashiwazaki and KKNPP have the predominant period of 2 seconds,
and this frequency content caused the severe building damage.
In this section, we estimate PGV from the relationship between observed records and damage rank of main
hall of temples and shrines constructed in the section 3.2. PGV was estimated by the following procedure: First,
the D3 damage ratio (the ratio of the damaged buildings subjected to damage of greater equal to D3 level against
the total buildings) of 2km radius neighborhood of a surveyed main hall is calculated for all surveyed sites. Thisdamage ratio is substituted into the inverse function of equation (2) to estimate PGV. If the D3 damage ratio is0%, it is removed from the analysis since the value does not exist in the lognormal distribution theoretically.
There was no site with D3 damage ratio 100%. We removed the sites with samples less than 5 within 2km. We
also tried 1km radius to compute the D3 damage ratio for more sensitive estimation. However, the resolution was
not enough since the number of the samples in the neighborhood was too few. Therefore, we use the radius of
2km. Since the sedimentary soil structure in this region is very complicated, there is a limitation to characterize
the local change, but it is helpful to understand the perspective of the ground motion distribution in this region.
The comparison between the PGV estimated by this method (we call this PGVt) and the PGVa in section 4.1
is shown in Figure 8. In this figure, “o” and “x” symbols represent surveyed sites with altitude less than or greaterthan 10m, respectively. The correlation coefficient between the PGVt and PGVa is 0.65. The PGVt and PGVashow good agreement in the low altitude region (i.e. Kashiwazaki basin), but there is a large discrepancy in theregion which has large altitude gradient. This region is a severely damaged area, where many totally collapsed
wooden houses were observed in our field survey. One of the reason why the PGVa in this region underestimate
PGVt is, that the soil amplification factor is small due to the short distance to the mountains and hills (In theempirical equation of Matsuoka et al., [13] ARV becomes small as the distance to the mountains and hills becomesshort).
Figure 9 shows the PGVa distribution and PGVt at our survey sites. Most of the sites, the PGVt and PGVa
agree well. The downtown Kashiwazaki where PGV larger than 100cm/s was recorded, shows large PGVt and
PGVa, which agree with the observed records.
4.3. PGV Estimation from the empirical function of the ratio of overturned tombstones
In section 3.3, overturned tombstone data in the station neighborhood shows the ratio of the overturned
tombstone does not fit the empirical function of the ratio of overturned tombstones. In order to check the effect of
the geographical condition to the applicability of this function, we apply the empirical function of Kaneko andHayashi to all of surveyed sites, and compare with the PGVa. The sites with 0% or 100% of overturned
tombstones are removed from the analysis since the value does not theoretically exist in the lognormal
distribution.
Figure 10 shows the PGVa distribution and PGV estimated from the ratio of overturned tombstones (we callthis PGVb) at our survey sites. PGVb underestimates PGVa especially in the Kashiwazaki basin. K-NET
Kashiwazaki and Kariwa observed PGV of 110-120 cm/s and PGVa around the station is compatible with theobservation. However, the PGVb is less than 80cm/s, which cannot characterize the real ground motion.
This result shows the PGV obtained from the ratio of overturned tombstones does not agree with theobserved PGV, especially in the Kashiwazaki basin where the long period ground motion was amplified. Also,
the PGV estimated from the ratio of overturned tombstone becomes smaller than PGV estimated from attenuation
relationship in the Kashiwazaki basin. The effect of the long period ground motion (longer than 1 second) to thetombstone is not clear in this analysis. The relationship between the ratio of overturned tombstone and long
period ground motion needs to be examined in the future work.

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The 14 World Conference on Earthquake Engineering
October 12-17, 2008, Beijing, China

Figure 9 PGVa distribution and PGVt (in circle).

Figure 10 PGVa distribution and PGVb (in circle).

5. CONCLUSION
In this paper, we performed a damage survey of temples and shrines near the source region of the 2007
Niigata-ken Chuetsu-oki earthquake and tried to estimate the distribution of strong ground motions from thedamage rank of main hall of temples and shrines. Our conclusions are as follows:---

We compared the observed records and damage ratio of main hall of temples and shrines, and shows thedamage ratio has a good correlation with PGV. Based on this result, the empirical function to estimate PGVfrom damage ratio for the 2007 Niigata-ken Chuetsu-oki earthquake was proposed. Defining the ratio of thedamaged buildings subjected to D3 - D5 damage against the total buildings as P D3 damage ratio, therelationship between P D3and PGV is; PD3(PGV)＝Φ(ln(PGV)-4.61)/0.31)
The PGV distribution in the entire near-source region was estimated from the constructed empirical functionof PGV and damage ratio of main hall of temples and shrines. The result shows the PGV exceeds 100cm/s inmost of the Kashiwazaki basin.
The PGVt estimated from the damage rank of main hall of temples and shrines agrees with PGVa in the mostpart of the near-source region, but PGVa becomes smaller than PGVt in the region which has large altitude
gradient.
Using the empirical function between the PGV and ratio of the overturned tombstones, we estimated the
PGV from the tombstone damage and compared with the observed PGV. The estimated PGV does not agreewith the observations since the predominant frequency of some stations exceeds 1 second in the 2007
Niigata-ken Chuetsu-oki earthquake.
The PGV estimated from the ratio of overturned tombstone becomes smaller than PGV estimated from
attenuation relationship in the Kashiwazaki basin. The effect of the long period ground motion (longer than 1
second) to the tombstone is not clear in this analysis. The relationship between the ratio of overturned
tombstone and long period ground motion needs to be examined in the future work.

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The 14 World Conference on Earthquake Engineering
October 12-17, 2008, Beijing, China

ACKNOWLEDGEMENT
The authors sincerely thank residents in the near-source region for their cooperation to the damage survey. We
acknowledge the National Research Institute for Earth Science and Disaster Prevention, Japan Meteorological
Agency, local governments, and the Tokyo Electric Power Company for the use of the strong motion data. This
research was supported by the Program for Improvement of Research Environment for Young Researchers fromSpecial Coordination Funds for Promoting Science and Technology commissioned by the Ministry of Education,
Culture, Sports, Science and Technology of Japan.
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