Uncertainty of anticipation of seismic intensities Uncertainty of - PowerPoint PPT Presentation

Uncertainty of anticipation of seismic intensities Uncertainty of anticipation of seismic intensities -A study of fluctuation of anticipated seismic intensities by the method of current JMA Earthquake Early Warning – JMA intensity Mitsuyuki HOSHIBA Kazuo OHTAKE Kazuhiro IWAKIRI Mitsuyuki HOSHIBA, Kazuo OHTAKE, Kazuhiro IWAKIRI (Meteorological Research Institute, Japan) Tamotsu AKETAGAWA (Japan Meteorological Agency) Hiromitsu NAKAMURA (National Research Institute for Earth Science and o tsu U ( at o a esea c st tute o a t Sc e ce a d Disaster Prevention, Japan) Shunroku YAMAMOTO (Railway Technical Research Institute, Japan) Apr 22 2009 Apr. 22, 2009. EEW Workshop EEW Workshop Anticipated Seismic Intensity ＝ f (Source Factor, Path Factor, Site Factor) At Present Source Factor ： 1 scalar (for example; Magnitude) Path Factor Path Factor ： Attenuation relation ： Attenuation relation Site Factor ： 1 scalar Without consideration of spectrum contents

JMA seismic Intensity Accelerogram, Accelerogram, A ns (t) 、 A ew (t), A ud (t) Filter Filter V(t)= ( ) JMA intensity JMA intensity (A ns 2 (t)+A ew 2 (t)+A ud 2 (t)) 1/2 is evaluated from 3 comp. accelerograms g (T t l d (Total duration of V(t) ti f V(t) > V a ) is 0.3s I =2 log10(V a )+0.94 Approximate Relation between JMA Intensity scale and Modified Mercalli scale pp y 5 5 6 6 JMA 0 1 2 3 4 7 L U L U Modified 10, 1 2 3 4 5 6 7 8 9 Mercalli 11,12

Method for anticipation of Seismic Intensity used in JMA Earthquake Early Warning used in JMA Earthquake Early Warning 1. Estimation of PGV from attenuation relation (Si and Midorikawa, 1999) using Magnitude , Hypo. Dist. and Depth 2. (PGV at surface)=(PGV at basement) × site factor 3. JMA intensity=2.68+1.72log （ PGV at surface ） ・・・ Mid Midorikawa et al, 1999 ik t l 1999 3

According to this idea According to this idea, Two Earthquakes occurred at the same place with the same magnitude 3.4 3.4 4.2 4.2 3.1 3.1 4.0 4.0 Intensity At each site, ・ paths are the same M4.8 ・ Site factors are the same Earthquake M4.8 At each site, Intensities of the two earthquakes are expected to be the same! R Really? or Not ? ll ? N ?

In actual observation, even with the same magnitude … From HP of JMA Intensities are not Intensities are not Even if the same Even if the same magnitude, always the same

Point B Point C 3 4 3 2 3.4 3.2 4.2 Intensity 4.2 3.3 3.1 Point D 4.0 4.3 Point A Point A M4.8 Earthquake M4.8 How large fluctuation ？ Point A 3.1 － 3.3 = -0.2 Point B 3.4 － 3.2 = 0.2 Point C 4.2 － 4.2 = 0.0 Point D 4.0 － 4.3 = -0.3 ・・・ Investigated the distribution of fluctuation

Data � Hypocenter and magnitude are from JMA unified catalogue y g g � Intensity observation by JMA, municipalities and NIED � May, 1996 – July, 2007 � M3.5 ～ 5.5 Select of the earthquake pair � Distance between those epicenters is less than 5km � Difference of focal depth is less than 5km � Having the same magnitude Select of Intensity data Select of Intensity data Exclude the range of Exclude the range of hypocentral distance at （ distance between which seismic intensity is hypocenters × 10 ） hypocenters × 10 ） observed to be less than 0.6 Intensity Intensity Hypocentral Distance (km)

・ Same magnitude ・ distance is less than 5km M4 00-20km Focal depth difference is less than 5km Focal depth difference is less than 5km M5 M5 20-40 20-40 40-60 ・ Intensities are observed commonly more M6 60-80 than 10 stations 80- N=100

①－② ① ② （ Intensity difference ） RMS: 0.50 Distribution of Intensities of Intensities Extent of uncertainty even when the earthquake occurred adjacently with the same magnitude At this station, Inteisity of Inteisity of I t Intensity of it f earthquake ② is earthquake ① is larger than ① by 1.7 larger than ② by 0.6

① ② ①－② Distribution of Intensity differnce RMS: 0.80

・ Same magnitude ・ distance is less than 5km Focal depth difference is less than 5km ・ Intensities are observed commonly more than 10 stations Histogram of RMS of Intensity Difference N=100 Average of RMS ： 0.41 Extent of uncertainty of Extent of uncertainty of intensity even when the magnitude, path and site are the same are the same

Two Earthquakes occurred at the same place with the same magnitude 3.4 3.9 4.2 4.7 3.6 3.1 4 0 4.0 4.5 4 5 Seismic i i Intensity At each site, ・ paths are the same ・ Site factors are the same 地震 Difference of At each site Intensities of the two earthquakes are expected to At each site, Intensities of the two earthquakes are expected to be the same! Really? or Not ?

AVE.=0.49 RMS=0.80 No._=230 Removing Inter ‐ event Inter event residual Shift by 0.49 Estimate the AVE.=0.00 RMS for each RMS=0.64 pair of p No. =230 _ earthquake

Magnitude is used Magnitude is used as source factor Average of RMS ： 0.41 → 0.33 g Average of Intensity difference is used as difference is used as source factor

Two Seismic Intensity meters located adjacently 2.2 2.4 5.1 5.3 Earthquake 3 Earthquake 3 Earthquake 2 Earthquake 2 Intensity When Hypocentral 3.1 3.3 3.2 3.4 distance is much larger Earthuake 1 Earthquake 4 than the distance between the 2 intensity meters For each eathquake For each eathquake I t Intensity it Intensity ・ Source factor is same meter A meter B ・ path is same For each earthquake, difference of intensity is expected to be the same h Really? or Not ?

Data � Hypocenter and magnitude are from JMA unified catalogue y g g � Intensity observation by JMA, municipalities and NIED � May, 1996 – July, 2007 � M3.5 ～ 5.5 Select of the pair of seismic intesity meter � Distance between those inteisity meters is less than 5km � Distance between those inteisity meters is less than 5km Select of Intensity data Select of Intensity data Exclude the range of Exclude the range of hypocentral distance at （ distance between which seismic intensity is hypocenters × 10 ） hypocenters × 10 ） observed to be less than 0.6 Intensity Intensity Hypocentral Distance (km)

Two Intensity meters meters Distance between intensity meters ： intensity meters ： 0.9km Average ： ‐ 0.15 Diff Difference of site f it factor Standard deviation ： 0.52 d i i Fluctuation of seismic intensity Intensity meter A is Intensity meter B is larger than B by 0.9 larger than A by 1.0

Distance Distance between Intensity meters ： 1.0km Average ： ‐ 0.63 Difference of site factor factor Standard deviation ： 0.40 Fluctuation of Fluctuation of seismic intensity

・ distance is less than 5km ・ Intensities are observed commonly more than 10 stations Histogram of standard Histogram of standard deviation of intensity difference N=791 Average of standard deviation ： 0 ． 29 E t Extent of uncertainty t f t i t even when the sites located adjacently Standard Deviation

Extent of uncertainty in anticipation of seismic intensity seismic intensity Uncertainty in anticipation of seismic intensity when Source factor is represented by 1 scalar Uncertainty (RMS) in case of same 0.41 ／ √ 2 ＝ 0.29 magnitude, same path, and same site 0.33 ／ √ 2 ＝ 0.23 For source factor, Seismic intensity is used instead of magnitude Uncertainty in anticipation of seismic intensity when Site factor is represented by 1 scalar Uncertainty in case of same source, Uncertainty in case of same source 0 29 ／ √ 2 0.29 ／ √ 2 ＝ 0.21 0 21 same path, and same site In addition to these uncertainty due to the In addition to these, uncertainty due to the attenuation relation should be considered