charles university prague partner no. 16 (cup)
DESCRIPTION
Charles University Prague partner no. 16 (CUP). J. Zahradník, J. Jansk ý, V. Plicka. Deliverables. 12Data base for selected stations of CUP (WP1). Plan: attention to “classical” issues (location, focal mechanisms, strong motions) as well as - PowerPoint PPT PresentationTRANSCRIPT
Charles University PragueCharles University Praguepartner no. 16 (CUP)partner no. 16 (CUP)
J. Zahradník, J. JanskJ. Zahradník, J. Janský, V. Plickaý, V. Plicka
Deliverables
12 Data base for selected stations of CUP (WP1)
Plan:attention to “classical” issues(location, focal mechanisms, strong motions)as well as various transients possibly related to strain
Present status: 8 CUP instruments jointly operated with UPATRAS
at 4 sites
• 2 stand-alone (SERG, MAMO)
• 2 satellite (LOUT, PYLO)
• each one with CMG-3T and 5T (weak & strong)
SERG (Sergoula)
MAMO (Mamousia)
BB: MAMO not equal SERG
MAMO, D=94 km, A=66o
SERG, D=102 km, A=50o
M5.4 VartholomioDecember 2, 2002
at f < 0.1 we get rid of site effectsMAMO SERG
5T as good as 3T for M5.4
Both CMG-3T and CMG-5T are needed (even for small local
events):
Example: M3.8, 13 km (SERG)
3T problem at HF
5T problem at LF
3T almost clipped
Can we also contribute to studies of slow strain events ?
Example: December 3, 2002 (suggested by Pascal B.)
• lower thermal variation in winter
• velocity record supplemented by
“mass channel” (integrated velocity output)
CMG-3T 3 days “mass channel”: an anomaly superimposed on the
thermal variation
EW NS
Zooming anomaly on EW (1 day)
... and the corresponding velocity
increased noise ?
anomaly
M3.5earthquake
the anomaly consists of eqs. and 4-5 minute long pulses, 10-5 m/s
4 10-6 m/s
10-5 m/s
CMG3-T: 1 day (Dec. 3, 2002)
Just these 4-5 minute long pulses constitute the anomaly of the mass
channel.
M3.5
Dec. 323:42
and what happensduring eq. ?
Mass channel
Velocity: signature of a sudden local tilt
M3.510-20 km
Modeling a similar event
Corinth GulfM3, distance 10km
Normal instrument response of CMG-3T to abnormal input:
ACCELEROGRAPH 100-SEC VELOCIGRAPH
input
output
input
output
Modeling the CMG-3T response
we arrive at thehorizontal acceleration stepof 6.10-6 m/s2
tilt step 6.10-7
Note the undisturbed vertical component, typical for the tilt.
low pass f < 1 Hz:data
model response
Dec. 323:42
5 min !
Following the sudden tilt (< 100 sec), accompanying the earthquake,there is a slow “strain recovery” but its amplitude is 10-30 smaller than slow pulses accompanyingthe preceding burst of smaller eqs.
Database (V. Plicka)http:/seis30.karlov.mff.cuni.cz
Database (V. Plicka)http:/seis30.karlov.mff.cuni.cz
regional local transients
Deliverables
16 New software for source-parameter inversion (WP1)
Innovation:LF local waveforms (f < 0.1 Hz)moment tensor, uncertainty of non-DC, multiplicity in space and time synthetic and/or empirical Green fctn.
Zahradník, J., Janský, J., Sokos, E., Serpetsidaki, A.,Lyon-Caen, H., and Papadimitriou, P. :Modeling the ML4.7 mainshock of the February-July 2001earthquake sequence in Aegion, Greece. (J. of Seismology, 2004)
inversion ofthe amplitude spectra 0.1 - 0.2 Hz
Iterative deconvolution of regional waveforms
Zahradník, J., Serpetsidaki, A., Sokos, E., Tselentis, G-A.:Iterative deconvolution of regional waveforms anddouble-event interpretation of the 2003 Lefkadaearthquake, Greece (Bull. Seism. Soc. Am., in press)
M6 Lefkada earthquakeAug.14, 2003
5 BB stationsepic.distance<140 km
Method• moment-tensor inversion (minimization of the L2
waveform misfit by the weighted least-square method)
• optimization of the source position and time (maximization of the correlation by the space-time grid search)
• a single point source for f < 0.1 Hz, and multiple point sources for f < 0.3 Hz
Final solution: 2 main
subevents,40 km and 14 sec apart
explaining the two aftershock
clusters
Vartholomio (near Zakynthos)
Dec. 2, 2002
ETH-SED: Mw=5.7
DC%=55 !(HRV: DC%=58,
Mednet: DC%=44) Zakynthos
6 NOA stations, f=0.05 to 0.1 Hz
weights proportional to 1/A were applied
blue: datablack: syntheticsfor crustal model of Haslinger et al. (1999)
100% DC matches data also well(only 0.05 worse)
we cannot see the difference
Going into large details: Optimum correlation
is not compatible
with 100% DC
tria
l sou
rce
posi
tion
trial time shift
Very stablestrike-dip-rakebuthighly unstableDC percentage
DC%: 72 to 97 %cf. 55% (ETH)
Fixing the opt. source position and increasing frequency (f < 0.3 Hz): 3 subevents
2-sec time delay between sub 1 and 2; sub 3 is unstable
Subevents 1 and 2: similar strike and dip, but different rake
Consider sub 1 and 2 as 100% DC(but unequal !), and sum up theirmoment tensors:
Result: sub 1+ 2 provides DC%77 to 93%, analogous to the previous single-source study.
Multiplicity seems to explainthe non-DC mechanism.
Deliverables
95 New software for near-real time seismic alarms (WP8)
PEXT: perturbation and extrapolationfinite-extent fault, composite source modelingdeterministic envelopes and accel. spectral level,stochastic HF phase; perturbed HF radiation pattern
Colfiorito Mw 6.0 benchmark
(M. Cocco)
“Moderate” directivity
GTAD
CTOR
Athens 1999 - PGA modeling
Shake map
up to 20 Hz
in a few minutes
on a PC
Tuning maximum slip velocity against the attenuation relation
Athens - synth. versus real records
... another station
Charles University Prague (CUP) summary of the tasks
12 Data base for selected stations of CUP (earthquakes + transients)
16 New software for source-parameterinversion (moment tensor, multiplicity)
95 New software for near-real time seismic alarms (directivity, fast computations)
http:/seis30.karlov.mff.cuni.cz