Discussion Points

Discussion Points • Existing data Sets • Tectonics • Simulations • Analogs • Data modeling • Data processing

Ground Motion Parameters • Source • Mw, scaling • Radiation pattern • Propagation • Crustal structure, Q, Duration • Site

Data Sets • SE Canada • Assembled 12/2008 • Can be rapidly reprocessed • Central US • Parametric data from 1982 – present from 3 networks: SLU/CERI (1982-1990), PANDA, CERI (2000's)

New Madrid/Central U.S. • Merge of 3 data sets • 1982-1991 – regional network • 1 Hz sensor, vertical • 1990-1991 – PANDA • 4.5 Hz sensor 3 component • 2002-2005 – CERI (and SLU ) • 4.5 Hz sensor – 3 component • Broadband – 3 component • (no gain ranged used) • Can be augmented

1982-1991 Epicenters (left), stations (right)

2000-2002 Epicenters (left), stations (right)

Status • Canada • Data sets on-line • Can be reconstructed from GSC autodrm • New Madrid • 1982-1991 tabular data of Fourier velocity spectra and peak filtered velocity, largest EQ's are 1990 and 1991 • 2002-2006 – waveforms on hand • Can be augmented

Source Mechanics and Mw • Affects geometrical spreading at short distance (modeling) • Spatial coherency in North America

Characteristic faulting for North America • Blue – thrust • Green – strike slip • Red - normal

www.eas.slu.edu/Earthquake_Center/MECH.NA • Blue – thrust • Green – strike slip • Red – normal • Spatial coherency may demand different scaling relations

Unpublished work (2003) • Theoretical study at 1 Hz – motions are somewhat coherent • Given insight if can be verified with real data • Next slides show some aspects of the study • Can easily be recomputed • Purpose to detail SLU processing and interpretation methodolody

Crustal models • Test effects of • Crustal thickness • Deep sediments • Upper crustal gradients

Effect of Moho Depth • Deviation from 1/R spreading • Moho bump depends on crustal thickness • Compare filtered velocity and Fourier velocity • Compare SS, 45DS and mixed population

Deep sediment effect • Large differences between components are reduced, especially for 45 DS mechanism

Analogs to Augment Data Set • Korea • Source – AB95 • Radiation – Strike Slip • Propagation – 30 km thick crust, lower Q • Site – weathered Archean • Data available by FTP • Response known • Site characterization, perhaps • Cooperation with KMA, KINS, other agencies

Source Mechanics • 32 MT solutions • Mw 3.2 - 4.7 • Mostly strike slip • H < 15 (upper crust) • Excellent modern digital network (24 bit, STS-2, Episensor)

20070102115645Mw=4.55, H=9km

Attenuation • Observed (color) and predicted attenuation for narrow-bandpass filtered ground velocity • Residual of fit

Korea • Strike slip sources • Good network • Focus on aspects of source, short distance attenuation • www.eas.slu.edu/Earthquake_Center/ • MECH.KR

Australia • Focus on MT solutions, structure • www.eas.slu.edu/Earthquake_Center/ • MECH.AU • Feasibility study

Earthquakes • Date ML Mw 20090131084703 4.6 3.78 Beacon, WA 20090305125351 4.5 4.05 Beacon, WA 20090305125351 4.2 4.45 SE Australia 20090318052818 4.2 4.42 SE Australia All are thrust H < 6 km Long period wave propagation to 1000 km similar to ENA Sparse distributution of broadband stations

Australia • Sparse station distribution • Can get Mw • Study sequences to derive source spectrum scaling before use • Thrust mechanisms which will permit augmentation of SE Canada, NEUS data set

Ground Motion Parameters • Source • Mw, scaling • Radiation pattern • Propagation • Crustal structure, Q, Duration • Site

Decisions to be made • Use of stochastic modeling • If done, what should be collected to constrain the modeling, e.g., PGA, PGV, Fourier spectra and/or narrow bandpass filtered ground velocity • Preparation of parametric data • If SA, then how to do this given limitations of existing data sets, e.g., 20 Hz, 40 Hz and some 100 Hz sampling

Discussion Points