SDR20160901YN

The change of the realtime intensity and early warning estimated fromthe strong motion records of the earthquake at 01:36, 24th August 2016
(UTC) causing severe damage around Amatrice
Yutaka Nakamura, SDR

This report overviews the characteristics of the earthquake motion at some sites fromthe realtime seismic intensity (a patent technology of SDR) using the strong motion
record of the represented earthquake (M6.0, depth 4.2km by INGV) released by thestrong motion observation network in Italy ITACA (http://itaca.mi.ingv.it/ItacaNet/).
The observation stations around the epicenter are pointed on Google Earth as Figure 1.
Figure 2 shows the change of the realtime intensity with detection time for each site.
This figure also shows that of the L'Aquila earthquake in 2009 at AGV station suburbanof L'Aquila for the reference. The additional figure is enlarged for ten seconds after theearthquake detection to confirm precisely the change after the earthquake arrival. Pleasesee addendum for the definition of realtime intensity and other information. Also notethat although the realtime intensity is defined newly and opened as papers by us in 1998
and 2003, another organization creates confusion with adding same name for the otherdefinition.
Figure 2 also shows the estimation of the alarm timing of FREQL. And it shows thetime margin of EEW against intensity 4 assigned as the beginning level for the damage,considering that the damage is caused by the earthquake motion more than intensity 5 inJapan. The right axis of this figure indicates MMI for reference.
It is possible to save only two to five seconds in epicentral area for this earthquake fromthis result. And it seems that it is difficult to survive from vulnerable buildings except
for some extraordinary preparation because of such extremely short time margin. Itmakes us confirm again that the fundamental of the earthquake disaster prevention is
keeping the earthquake-proof characteristics.

The change of the realtime intensity is divided for some small severe rise, not similar tothat of the ordinary epicentral earthquake as AQV station at the time of the L'Aquila
earthquake, increasing in one stroke just after the earthquake arrival. As a result, thealarm requires astonishingly long time after P wave detection, and the limited time
margin becomes shorter. This figure includes two safety stations not exceeding theseismic intensity 4, and the P wave alarm is seems to be not issued for these two sites.
And it seems that the P wave alarm should be issued for the other sites at the time
between two pink arrows.
The strong motion record at AMT close to Amatrice with serious damage indicates themaximum realtime intensity 5.1, corresponding to the instrumental seismic intensity,and this earthquake motion should cause no damage in Japan. However the maximum
realtime intensity 5.3 was observed at NRC station at northern side of the epicentralarea, there is almost no damage without any death in Norcia. Yomiuri newspaper on
30th August 2016 says this area has been reinforced, and it seems effective.
So the degree of the reinforcement may differ for each area. The amplitude
characteristics of the surface layer is usually noticed as the local characteristics, and theearthquake motion seems to be amplified larger at NRT station from the realtimeintensity at AMT and NRT. In spite of this situation, severer damage was sufferedaround AMT station. Of course it is important to grasp the ground characteristics,
however this fact shows that it is rather important to grasp the vulnerability and takeproper countermeasure for individual structure, especially for the area with ancient
traditional structures as Italy. There is an urgent need to progress seismic diagnosis withmicrotremor and establish the way to proper reinforcement.
The seismic wave required about 2.8 seconds to propagate for the first five strong
motion stations, and the location of epicenter can be estimated as Figure 3 from the P
wave arrival time of these five stations with least-square method. This result says rathereast against that of INGV and it was the northern side of Amatrice with depth of 9.6km.
Because UrEDAS procedure of AMT data also indicates the epicenter at northern
Amatrice, it is considered reasonable as an initial estimation of epicenter location.
FREQL alarm was issued about 1.3 seconds after P wave detection, and if these strong
motion sites work together, it is estimated that the location of the epicenter was grasped
about 1.5 seconds after that and then the magnitude might be decided. However it islittle late alarm for the damaged area, it will be useful trigger information for quick
response of the local relevant departments for the disaster prevention.
Figure 4 shows the distribution of the aftershocks till 29th August 2016 by INGV.
(End of Text)

Figure 1

6109FOC46

RM33SPD35

AQV Alarm level

21

743

TERO

21

AMT0-1-2

NRC0

FOC-1

TERO-2

RM33-3SPD-3-5

ref. AQV 2009 L'Aquila Eq.

Data Processing：SDR-4-4

AQV

Data Source：ITACA-6-7-5-50510152025303540455055
10

begining level ofDamage

32Alarm level

NRCAMT

987RM33TERO

6SPD

5FOC

4AQV

3121AMT

0-1-20NRC

P-wave Arrival

Realtime Seismic Intensity RI

4Lead timeat AMT

Alarm at SPD

5P-wave Alarm at AMT

6FOC-1

TERO-2

RM33-3SPD-3-4

AQV

Data Source：ITACA-5ref. AQV 2009 L'Aquila Eq.

Data Processing：SDR-4-6-7-5-1

Figure 201234567

Elapsed Time from P-wave arrival in seconds

89

Modified Mercalli Seismic Intensity MMI

Realtime Seismic Intensity RI

8

begining level of Damage

Modified Mercalli Seismic Intensity MMI

AMT NRC543.1

FOC
4342.9NRC

42.8

USGS10km

42.7

SDR 9.6km using first 5 sites;
AMT, NRC, RM33, SPD, TEROINGV 4.2km

AMT

TERO

42.6

SPDRM33
42.5

AQV

42.4

42.3
12.8

Figure 3

Figure 4

12.9

13

13.1

13.2

13.3

13.4

13.5

13.6

13.7

(Addendum)
Definition of realtime intensity and conversion to MMI
Realtime intensity RI is defined as the following formula, the common logarithm of thepower of the earthquake motion acting to the mass of 1kg adding a constant (see thereference).
RI = log(PD)+6.4
PD = av
Here, a and v are the vector of earthquake acceleration and velocity, respectively. Andoperator  indicates the inner product. The constant is set the maximum value of RI to fit
the JMA instrumental intensity and it will be 6.4 and 2.4 in case of the unit in MKS andin case of Gal (cm/s2) and kine (cm/s), respectively.
MMI is converted by the next formula following to the reference.
MMI = RI × (11/7) + 0.5
The power for unit mass PD, Power Density in W/kg, can indicate the basal metabolic
expenditure of human body as around 1 W/kg. That is, the PD corresponding to thebasal metabolic expenditure of human body is about 6.4, converting to the realtime
intensity. The power of the earthquake motion seems to be unexpectedly small.
However this acts to the entire mass, the heavier thing is effected by larger power ofearthquake motion.
References
Yutaka NAKAMURA: EXAMINATION OF A RATIONAL STRONG MOTION INDEX- Relationship between the DI value and the other strong motion indices -, 22st JSCE
Earthquake Engineering Symposium, 2003. (in Japanese with English abstract)(End of Addendum)