Various Considerations on Seismic Disaster Prevention
for Earthquakes at Central Italy
Yutaka Nakamura1, Jun Saita1 and Tsutomu Sato1

Abstract
On the earthquake sequence in central Italy from August 24, 2016,
here investigates many aspects from the viewpoint of earthquake disaster prevention with opened strong motion records. Additionally theother earthquake sequence in central Italy from September 26, 1997
was also investigated. As a result, it is cleared that EEW, Earthquake
Early Warning, can get a time margin from a few seconds to 10 seconds at the best. It is extremely important for making not so long time
margin of EEW to make advance preparation as ensuring safety zone
and to carry out evacuation training. On the source location which isone of the earthquake information to determine the damaged area, it
can be fixed a few seconds after the first earthquake detection. And
the source of the maximum earthquake motion is investigated and it isconfirmed that it can be possibly determined within 30 seconds after
the first detection. Additionally a severe damage is estimated aroundthe area of fault rupture. Judgement whether near the fault or not canbe adopted the size of the permanent deformation of the crust, and thispermanent deformation can be estimated from double integration of
the observed acceleration waveform. This knowledge is considered tosupport an available quick response to determine the damaged area
immediately after an earthquake occurrence. From the result of the
microtremor measurement after the 1997 earthquake, the antiseismicity of the structure as residences is estimated to have important
effect. Here reinforcement against earthquakes must be emphasized tobe the most important for the earthquake disaster prevention.
_______________________________
1 System and Data Research, Tokyo, Japan.

1

2

Y. Nakamura, J. Saita and T. Sato

1. Introduction
In September 1997, a Mw 6.0 Earthquake occurred at central Italy
and Basilica di San Francesco in Assisi suffered damage as collapsinga part of the ceiling. This basilica had been attacked by a relative large
foreshock nine hours before and suffered damage as falling down of
the mural paintings. During the investigation of the damage situation
by cultural property officials, the main shock attacked this basilica.
There was some villages completely damaged in the epicentral area bythese earthquakes, and the damage situation was similar to that causedby the earthquakes in central Italy after August 2016. A microtremor
measurement was conducted in November 1997 at villages in the epicentral area. The result suggested that the dynamic characteristics ofthe structures were the main cause of the damage although there was acertain level of relation between the ground condition and the damage.
In case of the series of the damage earthquakes in 2016, catastrophic
damage was caused in Amatrice, a little far from the epicenter, although no significant damage was caused in Norcia, almost same distance from the epicenter as Amatrice. It was cleared that structures in
Norcia have been enhanced earthquake safety by seismic reinforcement following the past experience, and it indicates clearly that theenhancing the earthquake safety has a profound effect for reducing theearthquake damage. After that, the largest event occurred close to
Norcia and caused serious damage for Norcia. However most of thelocal people had understood the characteristics that large earthquakes
always come in sequence in central Italy and had already evacuated,
so it is reported that the human suffering was relative few. Here considers on the earthquake disaster prevention with opened strong motion records, specifically, as earthquake early warning simulation for
the time margin against sudden earthquakes, quick determination of
the epicenter for rapid damage estimation, process of seismic intensity
or calculation of the scale of the crustal deformation.

2. Realtime seismic intensity and the alarm timing
2.1. On the realtime seismic intensity

Various Considerations on Seismic Disaster Prevention …

3

The realtime seismic intensity, RI, can be summarized as following.
The realtime seismic intensity is physically an index relating to thecapacity of supplying earthquake energy and defined as follows([2],[4],[5]);𝑅𝐼 = log(𝑃𝐷) + 6.4
𝑃𝐷 = 𝒂 ∙ 𝒗
Here, 𝒂 and 𝒗 are acceleration vector and velocity vector of theearthquake motion on the ground surface, respectively, and an operator, ” ∙ “, indicates inner product. The constant term is put to fit RI to
instrumental seismic intensity by JMA, Japan Meteorological Agency,
and defined when the both vector are in MKS unit (m/s 2, m/s). In caseof the unit in Gal (cm/s2) and kine (cm/s) for both vectors, the constantterm will be 2.4. Also, the instrumental seismic intensity by JMA isderived from an acceleration waveform of 60 seconds after earthquake
detection aiming to fit the past earthquake intensity scale based on the
feeling of human. Although this index is an artificial index basicallyderived from the maximum acceleration with the predominant frequency and other items with more than 60 seconds after the earthquake detection, it has been entrenched as an instrumental seismic intensity in Japan.
Power Density PD in W/kg is a power density of an earthquake
motion and defined as an earthquake motion power acting on a unitmass. Following the definition, a large seismic intensity means that
there is a potential leading to destruction with supplying large energy
with an object in absorbing easily energy as resonance. It is importantto understand this index as one of the indices measuring the earthquake motion on the context of the earthquake damage, as acceleration
relating to force, velocity relating to strain or energy, or displacement
relating to deformation.
The seismic intensity corresponding to a power density PD = 1
W/kg is 6.4 for RI or 10.6 for MMI. Additionally, a human activity
can also be expressed with PD. A basal metabolism of a human bodyis said to be about 1 W/kg and an activity metabolism transiently
reaches around 10 W/kg during exercise as swimming or football. In
case of a flat house, the mass act an earthquake load seems to be about

Y. Nakamura, J. Saita and T. Sato4

5 tons at the roof and it corresponds to a body weight of 70 persons
when assuming 70 kg for one person. For this house, the power of theearthquake motion of seismic intensity 6.4 is same as the power when
70 persons exercise in 1 W/kg. A motion of 1 W/kg is equal to a motion bringing up the human body itself to 10 cm per second.
So, the physical meaning of RI 6.4 is an earthquake motion having
a potential to supply a power as bringing up this house to 10 cm persecond. When an earthquake motion of RI 6.4 acts in this house forone second, the act earthquake motion energy is equivalent of a potential energy for 10 cm and a velocity corresponding to the motion becomes considerably large as 1.4 m/s. It can be easily imagined that thehouse absorbing this energy faces collapse if it is not constructed firm
enough. This maximum energy can be supplied by the earthquake motion of RI 6.4 even for one second. The longer acts, the larger a power
supplied. A vulnerable structure will be collapsed if the structure receives directly this earthquake energy.
It is found to avoid collapse that the countermeasures are required
as proofing of a structure against large deformation energy (earthquake resistant), avoiding resonance (vibration control), converting
supplied power to the other as heat immediately before causing strainenergy (vibration damper), or avoid transmitting the earthquake motion to a structure (seismic isolation).
Because the realtime intensity RI with physical background is quitecharacteristic of sudden increase from a level of microtremor when arriving an earthquake motion, it can steadily detect an earthquake and it
is easy to read certainly the detection time. And RI is expected to havehigh affinity to the other intensities based on the human feeling. Heremakes various considerations using these characteristics.
Also, conversion from RI to MMI, the Modified Mercalli Intensity,uses a following formula ([7]).
𝑀𝑀𝐼 = 𝑅𝐼 ×

11
+ 0.5
7

2.2. Variation of the realtime intensity RI and timing of issuing alarmin central Italy

Various Considerations on Seismic Disaster Prevention …

5

Seismic motion records of some strong motion observatories at epicentral area of following events are overviewed from the realtime intensity RI using the opened strong motion record by Italian strong motion observation network ITACA (http://itaca.mi.ingv.it/ItacaNet/).
#1: A Mw 6.0 and depth 8.1 km earthquake on August 24, 2016,
caused catastrophic collapse for Amatrice and other village.
#2: A Mw 5.9 and depth 7.5 km earthquake on October 26, 2016,
caused damage around Visso and other village.
#3: A Mw 6.5 and depth 9.4 km earthquake on October 30, 2016,
caused damage around Norcia and other town.
#4: A Mw 6.0 and depth 5.7 km main shock (#4m) and a Mw 5.7
and depth 5.7 km foreshock (#4f) on September 26, 1997,
caused damage as partially falling down of the mural paintingsof Basilica di San Francesco in Assisi by Event #4f and as collapsing two parts of the ceiling of the basilica with damage forvillages around the epicentral area by Event #4m 9 hours later.
(All magnitude Mw and depth are estimated by INGV.)
Figure 1 shows the distribution of these epicenters and strong motion observatories for this analysis.
GBP

ASS
#4m

#2

#4f

CNE

#3
NRC
#1
AMT
RM33
0 10 20 30 40 50km

AQV

Figure 1. Location of epicenters and strong motion observatories describedin this paper

Y. Nakamura, J. Saita and T. Sato

6

Figures 2 to 5 show change in time of the realtime intensity RI
based on strong motion records of these earthquakes. Because the recorded time seems to be almost exact except the 1997 earthquakes,
these figures show the change of the realtime intensity RI to the absolute time. All the figures are for 25 seconds length to compare a
sharpness of rising and other items for each other. In case of the 1997
earthquakes, the absolute time is uncertain and the record did not include the P wave initial motion for most of the station. So the startingtime of the record is estimated as dividing a hypo-central distance by
the S wave velocity assuming 3.5 km/s and then subtracting a time between the recording starting time and the S wave arriving time. In thisway, the changing situation of the realtime intensity RI at each station
is indicated on the time scale in the same manner, and it is possible tocompare with all the diagrams.
The sharpness of rising the realtime intensity RI is not quite differ
from the events or the stations. Of course the sharpness of rising is
kept till large seismic intensity in case of a large earthquake and is
kept till only small seismic intensity at distant stations. Therefore, arise sometimes becomes gradual in appearance because the sharp rising is buried in noise depending on the noise level. This means, it is

3

1
0
-1
-2
-3

-4
-5

First detection at AMT

2

10
9
8
7
6
5
4

S-wave arrival

AMT
NRC
FOC
RM33
SPD
TERO
AQV

24 August 2016 M6.0 depth 4.2km

3
2
1
0
-1
-2
-3
-4
-5
-6
-7

-6
30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55

lapse time in seconds from 2016/08/24, 1:36:00

Figure 2. Change of the realtime seismic intensity at some sites with the timingof P-wave warning (long downward arrows, pink band emphasizing the firstalarm) based on FREQL simulation for Event #1

Modified Mercalli Seismic Intensity MMI

Warning level

Maximum
RI arrival
arrivalRI
maximum

P- wave warning at FOC

4Danger level

Origin time by INGV

Realtime seismic intensity RI

5

P- wave warning at AMT

6

Various Considerations on Seismic Disaster Prevention …

Maximum
RI arrival
RI
maximum
arrival610Danger level

5

9

7

0

-1
-2

4

S-wave arrival
P- wave warning at FOC

1

5

P- wave warning at CNE

2First detection at CNE

6

3

-3
-4

3

FOC
CNE
CMI
PRE
MCV
NOR
NRC

2
1
0
-1
-2
-3

Modified Mercalli Seismic Intensity MMI

8Warning level

4

Origin time by INGV

Realtime seismic intensity RI

7

-4
-5

26 October 2016 M5.9 depth 7.5km

-6
-7

-5
-6
4

5

6

7

8

9

10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29

lapse time in seconds from 2016/10/26, 19:06:00

3
2
1
0
-1
-2
-3
-4
-5

10
9
8
7
6
5
4
3

P- wave warning at NCR

4

Origin time by INGV

Realtime seismic intensity RI

5

Maximum
RIarrival
arrivalRI
maximum

Dangerlevel
Warning
level

2

NCR
AMT
CLF
T1201
T1244
PRE

PCB
FOC
ACT
ACC
CSC
NOR

TRE
T1299
MNF
MCV
T1216
NRC

1
0
-1
-2
-3
-4
-5

30 October 2016 M6.5 depth 9.4km

-6
-7

-6
17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42

lapse time in seconds from 2016/10/26, 19:06:00

Figure 4. Change of the realtime seismic intensity at some sites and the timingof P-wave warning (long downward arrows, red character and arrow emphasizing the first alarm) based on FREQL simulation for Event #3

Modified Mercalli Seismic Intensity MMI

6First detection at Norcia
P- wave warning at Norcia

Figure 3. Change of the realtime seismic intensity at some sites and the timingof P-wave warning (long downward arrows, pink band emphasizing the firstalarm) based on FREQL simulation for Event #2

Y. Nakamura, J. Saita and T. Sato8

necessary to notice that there is a possibility to include serious misunderstandings for evaluation of the distance with sharpness of the rising.
In these figures, there are long thin downdraft arrows as the time ofearthquake detection, short fat updraft arrows as the arrival time of Swave, short fat downdraft arrows as the arrival time of maximum
seismic intensity, and green and orange horizontal lines as the level ofthe seismic intensity RI 4 and RI 5. Earthquake damage begins experientially to be caused by more than the seismic intensity RI 5 in Japan.
The level of the seismic intensity RI 5 is indicated as a danger level,
and also RI 4 is indicated as a warning level. Additionally the MMI
scale is indicated in the right side of the figures for reference.
Event #3 was observed at many sites over the seismic intensity RI 5
and its duration time was long. The other events have a few sites over
RI 5 and their duration time is short. From a viewpoint of the destructive energy, Event #3 is quite larger than the others and this agrees
that Mw 6.5 for Event #3 is the maximum value among the all analyzed earthquakes.
In case of Event #4m, the realtime intensity RI increased graduallyat the site GBP and the earthquake motion continues accordingly for along time. It is estimated that an earthquake motion with long natural
Maximum
RI arrival
arrivalRI
maximum

Danger
level

10
9
8

Warning
level

4

7
6

3

5
4

0
-1
-2
-3

-4
-5

S-wave arrival
P- wave warning at GBP

1

Detection at ASS

2

1997.9.26, 09:40:24, M6.0 h5.7km

3

CSC
GBP
MTL
MNF
BVG
CSA
ASS
NCR
CLF

2
1
0
-1
-2
-3

Modified Mercalli Seismic Intensity MMI

5

P- wave warning at ASS

Realtime seismic intensity RI

6

-4
-5
-6
-7

-6
25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

lapse time in seconds from 2016/10/26, 19:06:00

Figure 5. Change of the realtime seismic intensity at some sites and the timingof P-wave warning (long downward arrows , pink band emphasizing the alarmat Assisi) based on FREQL simulation for Event #4m

Various Considerations on Seismic Disaster Prevention …

9

period may grow gradually in surface ground. However common
structures will not resonance with this long period earthquake motion,
it may be necessary for a structure with long natural frequency as ahigh rise building to notice about resonance.
Onsite alarm has about 2 to 5 seconds between issuing alarm andarrival of maximum motion for each station. There is the potential toextend this time up to about 10 seconds in the damaged area excepting
a first few sites if these stations can be connected via network and thealarm at the first detection site can be participated. A time margin atdamaged area caused by earthquake sequence in central Italy is a few
to 10 seconds anyway at most, and it is necessary for making valuable
to take applicable countermeasures of hardware as constructing safetyzone and to carry out the evacuation training. It must be anew emphasized that to ensure the earthquake resistance is basic of the earthquake disaster prevention.
The realtime seismic intensity sometimes suddenly increases after
the earthquake motion arrival, or sometimes changes as divided forsome small part with sharp but small rising. It is estimated that thechange of realtime seismic intensity is corresponding to slip situationof a fault. Anyway it will be important for the earthquake disaster prevention to make residences tenacious avoiding sudden collapse.
Event #1 caused catastrophic damage for Amatrice. The maximum
realtime seismic intensity RI was 5.7 corresponding to MMI 9.5 froma strong motion record at a station AMT close to Amatrice, and this isa relatively serious situation as possibly suffering some sort of damage
in Japan. AMT is the nearest site to epicenter of INGV with epicentral
distance 8.5 km. At the second nearest site NRC with epicentral distance 15.3 km, RI was 5.3 corresponding to MMI 8.8, and it was small
a lot for that of AMT. It is said that there was little damage as no
death at that village Norcia. Earthquake retrofit had been conducted
there and this seems to be the effect of the work in addition to lower
RI than AMT.
Seismic capacity of structures may vary considerably for areas in
Italy. It seems that it is important for Italy remaining a lot of traditional old structures to grasp the vulnerability of structures individuallyand make a suitable reinforcement as well as to grasp the ground characteristics. There should be an urgent need to proceed a health investi-

10

Y. Nakamura, J. Saita and T. Sato

gation of structures utilizing the microtremor measurement and thenestablish the proper aseismic reinforcement.

3. Distance attenuation of maximum acceleration
Figures 7 to 11 show maximum acceleration of each earthquakes
against each epicentral distance. An orange line indicates the acceleration at the base ground estimated from strong motion records along
the first bullet train Tokaido Shinkansen line in Japan.
This is an estimation of acceleration considering two kinds of attenuation as geometric and distance (or inner) attenuation as followings;
A = 𝐴0 × 𝑒 −𝛼Δ /Δ𝑛Assuming n=0.5 from geometric attenuation of the surface wave,
the constants are defined statistically from earthquakes recorded by
SMAC type seismometer installed for Shinkansen line, then therelationship between the constants and magnitude for many events,and finally the formula below can be obtained ([1]). Also, the term
log10(Δ + ℎ), here h is depth in km, is used instead of log10 Δ not
only to avoid the abnormity at the epicentral area (Δ ≒ 0 km) but also
to take account of depth effect. Additionally, the maximum
acceleration of this formula has characteristics same as the waveformrecorded by the SMAC type seismometer, corresponding to 5HzPGA.
log10 𝐴 = 0.168 × 𝑀 − 0.5 × log10 (Δ + ℎ) − 0.0551 × 10−0.156𝑀 × Δ + 1.86

Figure 6 shows the attenuation curve of 5HzPGA of the Kumamoto
earthquake (Mw 7.0, h=12km) at the central Kyushu island of Japanon April 16, 2016. Blue and orange dots in this figure indicate
5HzPGA observed on the ground surface and under the ground at least
100 m depth, respectively. The acceleration value derived from theformula above corresponds to a lower limit of 5HzPGA on the surface
ground shown as the orange curve.

Various Considerations on Seismic Disaster Prevention …

11

10000

2016-04-16, 01:25 (JST),the
theKumamoto
Kumamoto
2016-04-16,01：25（JST）
earthquake(main
shock),
Mwh=12km
7.0, h=12km
earthquake(main),
Mw7.0,
5HzPGA

5HzPGA in Gal

1000←surface ground

Basement groundfor Japan
100

under ground →(minimum -100m)
10

1
1

10

100

1000

Epicentral distance in km

Figure 6. Attenuation curve of 5HzPGA, PGA limited by a frequency range between 0.1Hz and 5Hz for the 2016 Kumamoto earthquake Mw7.0 (main shock)1000

Basement
groundPGA in Gal

100

Event1#1
for Japan

for central Italy
1012016-08-24, Mw6.0, h=8.1km
PGA by ITACA
0.1
1

10

100

1000

Epicentral distance in km

Figure 7. Attenuation curve of PGA for Event #1

Y. Nakamura, J. Saita and T. Sato

12

1000

Basement
groundPGA in Gal

100

Event
2 #2
for Japan

for central Italy
1012016-10-26, Mw5.9, h=7.5km
PGA by ITACA
0.1
1

10

100

1000

Epicentral distance in km

Figure 8. Attenuation curve of PGA for Event #2

1000

Basement
groundPGA in Gal

100

Event
3 #3

for Japan

for central Italy
1012016-10-30, Mw6.5, h=9.2km
PGA by ITACA
0.1
1

10

100

Epicentral distance in km

Figure 9. Attenuation curve of PGA for Event #3

1000

Various Considerations on Seismic Disaster Prevention …

13

On the other hand, PGA becomes significantly larger than 5HzPGA
in general. Nevertheless, the distance attenuation situation of observed
PGA in Italy shown in Figures 7 to 11 indicates that 5HzPGA derived
from the formula above becomes quite larger than the lower limit of
the observed PGA. Thus, it is confirmed that PGA in Italy is quite
smaller than 5HzPGA in Japan. This smaller maximum acceleration
than that commonly in Japan suggests that the ground in Italy is
considerably harder than that in Japan.
Therefore, the PGA attenuation curve corresponding to the lower
limit of observed PGA in Italy was tried to be derived with arranging
the damping term of the formula above. Although the formula above
assumes the geometric attenuation of the surface wave, the attenuation
situation of PGA in Italy is seems to be proper to apply a geometricattenuation of the body wave. So the constant 0.5 of the formula aboveis changed for 1.0. The formula below is derived after a simple trial
and error process on the constant and the inner attenuation effect for
the lower limit of PGA.
log10 𝐴 = 0.168 × 𝑀 − 1.0 × log10 (Δ + ℎ) − 0.04 × 10−0.156𝑀 × Δ + 1.90

Distance attenuation diagram of PGA for each earthquake indicatesboth attenuation curves in Figures 7 to 11. Estimated PGA from above
formula can be confirmed to provide approximately the lower limit of1000

Basement
groundfor Japan

100

1997-09-26, Mw6.0, h=5.7km
PGA by ITACA
Basement
ground100

Event
4f #4f

PGA in Gal

PGA in Gal

1000

1997-09-26, Mw5.7, h=5.7km
PGA by ITACA

for central Italy
10

1

for Japan

Event
#4m
4m
for central Italy
10

1

0.1

0.1
1

10

100

1000

Epicentral distance in km

Figure 10. Attenuation curve of PGA
for Event #4f

1

10

100

1000

Epicentral distance in km

Figure 11. Attenuation curve of PGA
for Event #4m

Y. Nakamura, J. Saita and T. Sato

14

40

40

35

35

30
25
20
15
10

Diameterbubble:
of bubble:
Kg Kg

5

Amplification of PGA

Amplification of PGA

observed PGA for each earthquake.
Evaluating the lower limit of each earthquake as the maximum
acceleration at the base ground, the amplification factor of the
maximum acceleration is calculated for each sites. This result iscompared with the site classification of EC8, Euro Code 8, or theamplification factor derived from HVSR, H/V spectral ratio, of strong
motion records as Figures 12 and 13.
Although there is not much correlation between EC8 siteclassification and estimated amplification factor, the estimatedamplification factor clearly correlates with that derived from HVSR.
Apparent amplification factor of the maximum accelerationcommonly differs from the amplification factor as so-called sitecharacteristics. However it is not completely unrelated, it must show
some relationship. Figure 12 shows this and suggests the amplification
factor estimated from HVSR is reasonable.
Here, although it is not paid much attention, it must be noticed that
uncorrelated condition between H and V is a precondition in case of
discussion on a peak of HVSR about the predominant frequency.
Diameterofbubble:bubble:KgKg

30
25
20
15
10

5
0

0

0

5

10

A: amplification from HVSR

Figure 12. Relationship between
amplification of PGA and HVSR,
H/V spectral ratio

15

0

1
A

A* 2B

4
B* C3 C* D
EC8Euro Code 8

D* 5E

Figure 13. Relationship between amplification of PGA and Euro Code 8

4. A permanent displacement and a vibration displacement
derived from the double integration of the strong motion records
Here considers the displacement derived from the double
integration of the strong motion records. This displacement includes a6

Various Considerations on Seismic Disaster Prevention …

15

permanent displacement of crust caused by a fault motion and avibration motion. Because a fault slips around 1 m with a Mw 6 class
earthquake, a permanent displacement corresponding to this fault
motion and a vibration displacement caused by a propagation of anearthquake motion are observed near the fault.
Nonlinear behavior of a ground sometimes can be found dependingon the largeness of a strain on the ground. It is also possible to decidea positional relationship roughly between the fault and observation
point from the largeness of the permanent displacement. Additionally,
this displacement is expected to be utilized for judgement of damage
occurrence because the permanent displacement becomes more thansome tens cm in case of the site close to the fault.
Figures 14 and 15 show displacement records at some sites for each
events, and locus on the map for Event #3, respectively. The
permanent displacement was small less than 10 cm for Events #1 and#2, and it seems that the observation stations did not locate close to
the epicenter. Event #3 caused a permanent displacement of 40 cm at
Norcia and it suggests that this site locates close to the epicenter. In
4

12

8

Displacement in cm

4

8

2

6

0

4

-4

2

-6

Event #1

0

AMT
NRC

AMT 8.5km 329.5-2

NRC 13.7km 132.1-2
AMT 8.5km 329.5

0

-8

-6

-2

-10

-8

-4

-12

-4

NRC 13.7km 132.1

0

5

10

15

20

25

0

30

5

10

8

EW

15

20

25

4

Event #2
2016/10/26

0

-2

-2

-4

-4

-4

-6

-6

-6

-8
15

20

25

30

20

EW

0

-10

-10

-20

-20

-30

-30

-40

5

10

15

20

25

30

0

NS

-50
-60

5

10

15

20

25

Lapse time in seconds from first trigger time

30

10

15

20

25

30

0
-10
-20

2016/10/30
Event #3-30
NRCNRC
5.4km 11.8
PREPRE
7.6km 124.9
CSCCSC
15.6km 30.7
ACTACT25.9km 287.2

-50

NOR
NOR
5.5km 15.2T1216
9.3km 127.1
T1216
T1244
17.9km 301
T1244

NRC 5.4km 11.8
PRE 7.6km 124.9
CSC 15.6km 30.7
ACT 25.9km 287.2

-40
-50

-60

0

5

UD

10

-40
NOR 5.5km 15.2
T1216 9.3km 127.1
T1244 17.9km 301

PRE 8.4km 67.2

20

10

0

NRC 5.4km 11.8
PRE 7.6km 124.9
CSC 15.6km 30.7
ACT 25.9km 287.2

30

-8
0

20

10

25

CNE 2.5km 309

-8
10

20

2

-2

5

15

UD

4

CNE
PRE

PRE 8.4km 67.2

0

0

10

CNE 2.5km 309

2
CNE 2.5km 309
PRE 8.4km 67.2

5

8
6

4

2

0

30

NS

6

0

AMT 8.5km 329.5
NRC 13.7km 132.1

6

Displacement in cm

2

10

8

Displacement in cm

UD

NS

EW
6

NOR 5.5km 15.2
T1216 9.3km 127.1
T1244 17.9km 301

-60
0

5

10

15

20

25

Lapse time in seconds from first trigger time

30

0

5

10

15

20

25

Lapse time in seconds from first trigger time

Figure 14. Displacements derived from the double integration of the strong
motion for Events #1 to #3

30

Y. Nakamura, J. Saita and T. Sato16

addition, the permanent displacement of this earthquake moves to east
at the eastern side and to west at the western side, and it shows thecharacteristics of the fault motion at this area. This permanent
displacement agrees with an observation result of GPS and it isexpected that the double integration of a strong motion record cangrasp the proper displacement
nearly in realtime in case of the
2016-10-30、M6.5ノルチャ地震時の地表面の動き
displacement at least more than 10 cm. It will be available for thedisaster prevention if the damaged area can be determined quickly.

43.2

43.1

MNF, -0cm
CLF, -0cm
FOC, 0cm
43

MCV, 1cm
2cm
36cm

42.9

11cm T1216, 1cm
PRE, 3cm

10cm
Epicenter by INGVNOR, 12cm

20cm

42.8

39cm

9cm
ACT, 0cm

NRC, 7cm
T1244, -1cm

38cm

14cm

CSC, 2cm
10cm

ACC, -8cm

42.7

T1201, -1cm<-30 EW Displacement >30

T1299, 2cm

19cm

AMT, 0cm

42.6

Horizontal Displacement
10cm
Strong motion station

GPS station
42.5
12.4

Figure15. Locus of horizontal displacements derived from double integration ofstrong motion records on a map of displacement distribution by InSAR as red toblue for westward to eastward displacement of EW direction, comparing withdisplacements by GPS, for Event #3
12.6

12.8

13

13.2

13.4

13.6

5. Quick estimation of the epicenter for the damaged area
determination
Information of an epicenter of occurred earthquake is important todetermine the damaged area. Although the epicenter is commonly thestarting point of fault rupture and it mostly differs from an area

13.8

Various Considerations on Seismic Disaster Prevention …

17

concentrating damage, it has already been known that the location of
the epicenter can be determined with fairly quickness and accuracy if
observation points are installed properly. On the other hand, a sourceof the earthquake wave causing the maximum motion, hereafter “Maxsource”, is expected to have good correlation with the damaged area.
Here considers that how quick the epicenter, the starting point of thefault, and the Max source are determined for Events #1 to #3 given
accurate absolute time.
Calculation of an epicenter is to fix five unknowns as thecoordination X, Y and Z of the epicenter, the origin time and the wave
propagation velocity using the time of commencement of each stationby the least squares method. Here the wave propagation velocity isgiven as known and the rounded coordination of the first detection site
is set as initial value. The result is given as a value within apredetermined error as 0.5 km after repeatedly calculation. The
starting point of the fault rupture uses the P wave rising time as therising of the realtime seismic intensity. Additionally, the P wave
propagation velocity is set 6 km/s. Estimation of the Max source uses
a time of maximum realtime seismic intensity, and earlier time is used
if the maximum value is observed repeatedly. The wave propagation
velocity for the Max source estimation is basically set to 4 km/s anddecreased in step of 0.1 km/s with lower limit of 3.5 km/s.
Figures 16 to 18 show the result of calculation as mentioned above.
And Tables 1 to 3 list the appearance time of the P wave and the
maximum value. Tables 4 to 6 list the results of estimated hypocenterand that by INGV and USGS.
It is confirmed from the result of calculation that the hypocenter as
the starting point of the fault rupture can be determined with wave
arrival time of the first five sites with considerable accuracy. From
this result, it is expected to determine correctly the location of thestarting point of the fault rapture with the first five sites of detecting
an event, of course although it is depends on the relationship between
the epicenter and the observation stations. In case of Event #1, thefifth station detected the earthquake motion 2.1 seconds after thedetection of the first station on the time series. Because it takes lessthan 0.1 seconds for the calculation of the hypocenter, it is possible todetermine the correct location of the hypocenter in a little over two

Y. Nakamura, J. Saita and T. Sato

18

43.1

FOC
43

42.9

NRC

42.8

USGS 10km
42.7

INGV
8.1km

SDR 9.6km using first 5 sites;
AMT, NRC, RM33, SPD, TERO

Max source 8.2ｋｍ

TERO

AMT

42.6

SPD

RM33
42.5

AQV

42.4

42.3
12.8

12.9

13

13.1

13.2

13.3

13.4

13.5

13.6

13.7

Figure 16. Quick estimation results of the hypocenter and Max source showing
depth in km, with hypocenter estimation by INGV and USGS for Event #1.

43.05

43.00

FOC
MCV

42.95

Max

42.90

CNE

PRE
CMI

42.85

42.80

SDR

INGV

NOR

NRC

42.75
12.85 12.90 12.95 13.00 13.05 13.10 13.15 13.20

Figure 17. Quick estimation results of the hypocenter and Max sourcewith hypocenter estimation by INGV for Event #2.

Various Considerations on Seismic Disaster Prevention …

19

43.20

NCR
43.10

MNF
CLF
FOC

43.00

42.90

MCV

TRE

42.80

Max17: 10km

T1216
PRE

Max15: 3.9km
INGV: 9.4km
SDR17: 5.1km
SDR5: 5.9km
NOR
NRC
ACT
T1244
CSC

42.70

ACC

T1201
T1299

AMT

42.60

PCB
42.50
12.70

12.80

12.90

13.00

13.10

13.20

13.30

13.40

13.50

Figure 18. Quick estimation results of the hypocenter and Max source withhypocenter estimation by INGV for Event #3. A number after colon means
depth in km.
Table 1. Appearance time of the P wave and the maximum RI at strong motion
sites for Event #1
site
N (degree)
E (degree)
p-timemax-time

arrival time
AMT
NRC
TERO
RM33
SPD
AQV
FOC
42.632542.792542.62279
42.50898 42.515099 42.377102 43.026299
13.2866
13.0964
13.60393
13.21452
13.37113.3439
12.8965
34.80
35.70
37.60
36.80
36.90
39.03
40.45
38.40
42.10
45.80
42.50
44.60
47.30
50.00
note: times are lapse time in seconds from 2016/08/24, 01:31:00

Table 2. Appearance time of the P wave and the maximum RI at strong motion
sites for Event #2
site
N (degree)
E (degree)
p-timemax-time

arrival time
NOR
MCV
FOC
CNE
PRE
NRC
CMI
42.792442
42.993401
43.0263
42.894402
42.879299
42.792543
42.850399
13.092422
13.001312.896506
13.1528
13.0334
13.096475
13.0928
9.23
9.28
10.86
7.34
8.56
9.20
8.34
13.80
13.20
16.10
11.00
12.10
13.70
12.50
note: times are lapse time in seconds from 2016/10/26, 19:18:00

Table 3. Appearance time of the P wave and the maximum RI at strong motion
sites for Event #3
arrival timesite
N (degree)
E (degree)
p-timemax-time

NRC
NOR
PRE
T1216 CSC
T1244 MCV
ACC
T1201 MNF
ACT
CLF
T1299 FOC
AMT
TRE
PCB
NCR
42.7925 42.7924 42.8793 42.8907 42.7191 42.7570 42.9934 42.6960 42.6573 43.0597 42.7713 43.0367 42.6342 43.0263 42.6325 42.8765 42.5580 43.1116
13.0965 13.0924 13.0334 13.0190 13.0123 13.2978 13.0013 13.2420 13.2508 13.1845 13.4125 12.9204 13.2822 12.8965 13.2866 12.7358 13.3380 12.7847
19.68
19.71
20.03
22.25
21.17
21.41
21.71
21.71
22.44
22.47
22.31
23.08
22.98
23.07
23.19
23.62
24.39
25.11
25.30
30.00
27.90
28.20
31.30
28.20
27.90
29.80
30.50
29.20
30.00
33.90
31.10
31.40
31.30
39.30
34.10
37.10
note: times are lapse time in seconds from 2016/10/30, 06:40:00

20

Y. Nakamura, J. Saita and T. Sato

Table 4. Estimated hypocenter and Max source with the hypocenter by INGV and
USGS for Event #1
source parameter
cf.
SDR
SDR
SDR
SDR
INVG
USGS
hypocenter hypocenter Max source Max source hypocenter hypocentersite number/ Mw
5
7
5
7
M6.0
M6.2
N (degree)
42.72242.71742.69042.69242.69842.714E (degree)
13.27513.27413.24613.23813.23413.172depth in km
9.6
9.6
8.2
6.2
8.1
10.0
origin time
32.5
32.5
38.9
38.6
32.0
assumed v
vp=6km/s
vp=6km/s vs=3.7km/s vs=3.8km/s
note: times are lapse time in seconds from 2016/08/24, 01:31:00
estimated by

Table 5. Estimated hypocenter and Max source with the hypocenter by INGV for
Event #2
source parameter
cf.
SDR
SDR
SDR
SDR
INGV
hypocenter hypocenter Max source Max source hypocentersite number/ Mw
565
6
Mw 5.9N (degree)
42.91842.91742.92642.92142.9087
E (degree)
13.15613.15413.12513.12313.1288
depth in km
2.7
2.5
3.0
2.2
7.5
origin time
6.7
6.8
9.7
9.8
6.0
assumed v
vp=6km/s
vp=6km/s
vs=3.7km/s
vs=3.6km/s
note1: times are lapse time in seconds from 2016/10/26, 19:18:00
note2: NOR and NRC are considered as one site because they are closed for each other.
estimated by

Table 6. Estimated hypocenter and Max source with the hypocenter by INGV for
Event #3
source parameter
cf.
SDR
SDR
SDR
SDR
INGV
hypocenter hypocenter Max source Max source hypocentersite number/ Mw
5
17
15
17
Mw 6.5N (degree)
42.83942.84542.87542.88942.840E (degree)
13.11713.12513.202
13.24313.110depth in km
5.9
5.1
3.9
10.0
9.4
origin time
18.3
18.4
25.9
25.4
18.0
assumed v
vp=6km/s
vp=6km/s vs=3.6km/s vs=3.5km/s
note1: times are lapse time in seconds from 2016/10/30, 06:40:00
note2: NOR and NRC are considered as one site because they are closed for each other.
estimated by

Various Considerations on Seismic Disaster Prevention …

21

seconds after first detection under a situation gathering entire data inrealtime. It was 1.89 seconds and 1.73 seconds after the first detection
to get the detection time of the whole five stations for Events #2 and#3, respectively. Therefore, it is expected that the hypocenter as thestarting point of the fault rapture can be determined about two seconds
after the first earthquake detection for this central Italy earthquake
sequence. And the magnitude of the earthquake will be able to be
estimated immediately after the hypocenter determination.
On the Max source, it is determined with the data of five or sevenstations for Event #1 assuming the wave propagation velocity as 3.7 or
3.8 km/s. Although it seems that it requires certain time to confirm theappearance time of the maximum realtime seismic intensity, assuming
the required time as 10 seconds, the Max source will be determined
21.0 or 25.2 seconds later from the first detecting with fixing theappearance time of the maximum realtime seismic intensity. Similarly,
the appearance time of the five or six stations were fixed 16.3 or 18.8
seconds and the Max source was estimated with the wave propagation
velocity of 3.7 or 3.6 km/s for Event #2. In case of Event #3, after
fixing the appearance time of 17 stations, the Max source wasdetermined at about 10 km north-east of the epicenter with the wave
propagation velocity of 3.5 km/s. The time of determination seemed to
be about 30 seconds after the first detection time. This Max source
locates at the northern edge of a seismic gap of aftershocks about 10
km east from the epicenter as shown in Figure 19. If the seismic gap
of aftershocks corresponds to the rupture zone of the main shock, it isreasonable that the maximum earthquake energy is ejected from thelocation of the Max source. This means that the Max source agrees
with the seismic gap of aftershocks and the validity of the Max sourceis suggested. An extension of the damage around the Max source isconcerned and it will be necessary to verify with the actual situation ofdamage.
It was found that the hypocenter can be determined accurately
within a few seconds after the first earthquake detection as the roughinformation to determine the damaged area. The Max source
considered to have relation to the damage concentrated area, and thetime for determination may require about 30 seconds. The Max source
will be utilized as a trigger information of an immediate response by a

Y. Nakamura, J. Saita and T. Sato22

local department on disaster prevention, although it is late information
43.20 as an alarm for the damaged area. For this purpose, it is necessary tokeep considering about the relationship between the Max source anddamaged area or the promptness of estimation.
NCR

43.10

MNF
CLF
FOC

43.00

MCV

42.90

T1216
PRE

TRE

INGV: 9.4km
42.80

NOR

Max17: 10km
Max15: 3.9km
SDR17: 5.1km
SDR5: 5.9km
NRC
ACT
T1244

CSC

42.70

ACC
T1201
T1299

AMT

42.60

PCB
42.50
12.70

12.80

12.90

13.00

13.10

13.20

13.30

13.40

13.50

Figure 19. Estimated results on aftershock distribution map for Event #3,
adding to Figure 3 of [9]6. Relationship between damage and earthquake response
characteristics of ground and structures
Here describes the result of the microtremor measurement on
September 1997 after Event #4 ([3]). The target area of thisVarious Considerations on Seismic Disaster Prevention …

23

measurement was at and around Basilica di San Francesco in Assisi
collapsed as falling down of ceilings and some damaged villages.
At the basilica, microtremor was measured at totally three points as
the floor around the entrance of the lower and upper church and on theremained ceiling backward of the collapsed ceiling near the entrance.
A two-story residence was also measured at one points on the firstfloor. These measurements were conducted individually and not
simultaneous at ground and buildings.
Figure 20 shows the location of the microtremor measurement on
the ground with damage situation roughly around the point. Figure 21
is H/V spectrum derived from the measured microtremor.
Figure 22 shows Kg value derived from the peak frequency and its
peak value, amplification factor, of H/V spectrum. However thedamage of buildings tends to be caused at the area with large Kg value,
the value is 10 strain/Gal at most and is not so large than usual it isconcerned that significant non-linearity of ground must be caused byconsiderably large earthquake motion and it is estimated that theamplification effect of the earthquake motion is also not so large.
Therefore, it seems that the damage occurrence depends considerablyon the anti-seismicity of the building itself.
The earthquake response characteristics of the damaged basilica
and non-damaged residence using microtremor are shown in Figures
23 and 24. Table 7 is Kb value for buildings and Kb value is one of K
ASSISI

Annifo

A3
A1
A2

Cesi
EPICENTER

A4
S1

Voltellina
Colle-Curti ForcellaFirenze
Perugia

MARCHEV1C2C1UMBRIA
Roma

G7

G3
G1
G4
G2
G6 G5

Site aroundsituation
G1
G2
G3
G4 damageG5 damageG6 damageG7 damage

Site aroundsituation
A1
A2 damage
A3
A4
S1
-

Site aroundsituation
C1 damageC2 damage
V1
F1
-

F1

Figure 20. Location of the microtremor measurement points on the ground and a
two-story house (S1)Y. Nakamura, J. Saita and T. Sato

24

G1

G2

G3

G4

C1

C2

V1

F1

NS/UD
EW/UD

G6

G5

A1

A2

A3

A4

NS/UD

NS/UD
EW/UD
EW/UD
G7

NS/UD

Figure 21. HVSR of microtremor at the measuring sites on the ground
Short Axis(S1)
EW/UD
Long Axis(S1)

S1

100

↓:Damage↓ ↓ ↓ ↓

Kg Value

10

↓

EW
NS

↓
↓

1

0
G1

G2

G3

G4

G5

G6

G7

C1

C2

V1

F1

A1

A2

Site

Figure 22. Kg-values derived from HVSR of microtremor

A3

A4

Various Considerations on Seismic Disaster Prevention …

25

values derived from the earthquake response characteristics above.
The earthquake motion at the ground surface was estimated from therecord as 150 Gal at Assisi and 100 Gal around the residence
considered as the base ground. Although the drift angle is estimated

C-2

C-1
C-4

X(WE)

Amplification Factor

Amplification Factor

Amplification Factor

Z

Y(NS)

C2/C1

C2/C1

C2/C1

C1/C4

C1/C4

C1/C4

C2/C4

C2/C4

C2/C4

Figure 23. Earthquake response characteristics of damaged basilica

A3

L
side
S1 on 1F

Back of
S1
T

Amplification factor

26

Y. Nakamura, J. Saita and T. Sato

S1

T/UD
L/UD
Figure 24. Earthquake response characteristics of non-damaged residence
Table 7. Kb-value, natural frequency and amplification factor for structures
Basilica di San Francesco at Assisi 2-story house at Annifo
Fn (Hz)
2
6
A
12
79
2.5
H (m)
12
3
Kb (strain/Gal)
20
63
21
Note: Kb=2500A/Fn2/H/p2 , see [8] in detail.

large as 1/100 at the basilica from the Kb value, it is small as 1/500 at
most for the residence. It agrees that the ceiling of the basilica wascollapsed but the residence was almost no damage.
The affection of the softness of the ground has usually been
regarded for the building damage and grasping the characteristics of it
has been concentrated. However the characteristics of ground incentral Italy are generally fine. Of course the amplification
characteristics of ground by earthquake motion is important, but it
seems to be more important to grasp the anti-seismicity of buildings
exactly and to take proper countermeasures.
It is considered to be important for public places as church to
publicize the way of response against earthquake. The damage ofbuildings as collapse of the ceilings must be occurred at the portion

A4

Various Considerations on Seismic Disaster Prevention …

27

with different deformation, which is the portion concentrating thestrain.
In case of Basilica di San Francesco in Assisi, the main axis of thestructure is east-west direction and there is intersection of the entrance
wall and the altar at the both side of the axis. So the structure between
the entrance and the altar can swing easier to north-south direction
than east-west direction. There are buttresses for reinforcement against
this motion. It is clear from the result of the microtremor measurementthat the structure can nevertheless swing easy in north-south direction.
Because the both side around the altar and the entrance is difficult toswing in north-south direction, it is estimated that the strain wasconcentrated at this portion and then it caused the collapse. Thus,
there are two dangerous points at the basilica and the collapse
occurred at these points.
This kind of weak points will be found in the other many structures.
It is considered that it will be possible to decrease human suffering by
earthquake with setting a safety zone against the unexpected avoiding
these weak points. Of course the function of the safety zone will beadvanced with positive safeguard.
It is also important to clearly specify the safety zone to avoid
evacuation wrongly for the dangerous area against the people noticing
earthquake quickly and activating evacuation by alarms.
Although the ideal countermeasure is to increase the anti-seismicityof structures against expected damage, it will be possible to save a lotof human losses if it will be possible to take countermeasures toextend as much the time till collapsing a structure, even in case withdifficulty to take the ideal countermeasure. Taking countermeasures
for anti-seismicity and setting or constructing the safety zone are felt
as urgent need.
Especially for places as churches or theaters people gathering, it isurgent task to take countermeasures against falling objects and it isrequired to inform dangerous area as changing structure and to takecountermeasures in anticipation of the collapse.

7. Conclusions

28

Y. Nakamura, J. Saita and T. Sato

Here investigates on the earthquake disaster prevention with strong
motion records in view of damage situation of the earthquake
sequence in central Italy from August 24, 2016. The result can beconcluded as follows.
Although onsite EEW can be issued around one second after
earthquake detection, time margin of it is only a few seconds before
arrival of a large earthquake motion possibly causing damage inepicentral area with severe damage. However there are few
countermeasures with such short time margin, it is important to
prepare an effective way to survive and train it. It is also important tofind out accurately vulnerable structures and to make them antiseismic. It will make the time before suffering damage short and makesuch short time margin effective even if the damage cannot be avoided.
It is necessary to grasp properly the damaged area for quick rescue
activity of suffered people. The hypocenter as a starting point of fault
rupture or the magnitude of an earthquake can be determined properly
about a few seconds after the first earthquake detection under thecurrent distribution of strong motion observatories. However the
hypocenter is only a starting point of fault rupture, it may discrepantfrom the area with severe damage in case of a large earthquake. So,
here investigates how quick and proper the Max source and a crustal
deformation caused by an earthquake can be estimated. As a result,the Max source can be determined within about 30 seconds,
depending on a case. The permanent deformation can be also grasped
with double integration of the observed waveform in a few minutes
later. Therefore, it is expected whether an observation point locatesclose to the fault or not is cleared a few minutes after the firstearthquake detection.
This research uses opened strong motion records. This kind of
information are extremly important and useful for disaster prevention.
Installing at least one observation station for each municipality seems
to wake that the response after the earthquake dramatically quick andproper. Additionally at least important facilities would be installed
own seismometer to grasp it vulnerability or to respond rationally after
an earthquake.

Various Considerations on Seismic Disaster Prevention …

29

Acknowledgement
At the time of the measurement around Assisi in 1997, Prof.
Rovelli supported the authors at Basilica di San Francesco andvillages around there and late Prof. Mucciarelli supported the authors
at villages and a dam around the epicenter. The authors would like toexpress our gratitude for them. Especially, Prof. Mucciarelli who
worked actively on the earthquake disaster prevention suddenly
passed away on November 7, 2016. It is felt much regret because hewas still young for further activities. The authors cannot help but feellarge sense of loss. We would like to take even a part of his will forthe earthquake disaster prevention. May his soul rest in peace.
All the strong motion records are opened by ITACA with supportof many organizations. The authors express our thanks to theseorganizations.

References[1] Yutaka Nakamura and Kenji Tomita, “An Estimation Formula ofMaximum Accerelation caused by Earthquake (in Japanese)”, Abstract
Volume of the 39th Annual Meeting of JSCE, Japan Society of Civil
Engineers, Vol.1, pp.785-786, October 1984.
[2] Yutaka Nakamura, “A new Concept for the Earthquake Vulnerability Estimation and its Application to the Early Warning System”, Proceedingsof Early Warning Conference, EWC’98, September 7-11, 1998, Potsdam, Germany.
[3] Jun Saita, Yutaka Nakamura, and Marco Mucciarelli, “Relation between
Seismic Damage and Dynamic Characteristics of Sub Soil -A few Examples of the 1997 Umbria-Marche Earthquake-(in Japanese with English abstract)”, Proceedings of the 10th Earthquake Engineering Symposium, Vol.1, pp.333-338, 1998.
[4] Yutaka Nakamura, “Examination of a Rational Strong Motion IndexRelationship between the DI value and the other strong motion indeces(in Japanese)”, Abstract Volume of the 27th JSCE, Japan Society of
Civil Engineers, Earthquake Engineering Symposium, p.54, December
9-12, 2003, Osaka, Japan.

30

Y. Nakamura, J. Saita and T. Sato[5] Yutaka Nakamura, “Comparison of Various Earthquake Motion Indices(in Japanese with English abstract)”, Abstract Volume of the 27th JSCE,
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[7] Yutaka Nakamura, Tsutomu Sato, and Jun Saita, “The 2011 off the Pacific coast of Tohoku Earthquake: Outline and some topics”,
Proceedings of the workshop DISS_12, L’Aquila, 29-30 March 2012.
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DISS_15, pp.25-41, Rome, 29-30 March 2015.
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E.Casarotti, M. Cattaneo, P. De Gori, C. Chiarabba, G. Monachesi,
A.Lombardi, L. Valoroso, D. Latorre, and S. Marzorati, “The 2016
Central Italy Seismic Sequence: A First Look at the Mainshocks,
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