/
Evaluation of simulation results: Aftershocks in space Evaluation of simulation results: Aftershocks in space

Evaluation of simulation results: Aftershocks in space - PowerPoint Presentation

olivia-moreira
olivia-moreira . @olivia-moreira
Follow
369 views
Uploaded On 2018-03-20

Evaluation of simulation results: Aftershocks in space - PPT Presentation

Karen Felzer USGS Pasadena Preliminary Work Subject to change The ETAS simulations assign aftershock density with distance r from the mainshock as Aftershock density 1r dmin ID: 658551

fault aftershock aftershocks earthquake aftershock fault earthquake aftershocks distdecay landers points northridge simulation data real density field dmin mainshock

Share:

Link:

Embed:

Download Presentation from below link

Download Presentation The PPT/PDF document "Evaluation of simulation results: Afters..." is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.


Presentation Transcript

Slide1

Evaluation of simulation results: Aftershocks in space

Karen Felzer

USGS PasadenaSlide2

Preliminary Work!!

Subject to change!Slide3

The ETAS simulations assign aftershock density with distance,

r

, from the mainshock as:

Aftershock density = 1/(r+dmin)-distDecay

dmin

(km)

0.3

0.50.5distDecay1.72.02.5

Trial parameter combinations:

Which simulation parameters recreate real data the best?Slide4

Trial Cases

Landers earthquake

Northridge earthquakeSlide5

Before we start: Where’s the fault?

The parameter

r must be measured to the

mainshock fault plane, but where exactly is the real rupture surface?Slide6

Faults can be very complex

Detail of El Mayor-

Cucapah

rupture, (Rymer et al. in preparation, courtesy of Katherine Kendrick)Slide7

Quick and dirty aftershock-based fault-tracing approach

Place aftershocks into 5x5x5 km bins

Sort the bins by aftershock densityCalculate

Nbin = min((Fault area)/10,(Total number of populated bins)/4)Place fault points at the median aftershock location in the Nbin most populated binsThe distance

r

is measured from aftershock hypocenters to the nearest fault point.

Slide8

Fault points for the Landers earthquake

M 3+ aftershocksSlide9

Fault points for a simulated Landers earthquake with

minDist

= 0.3 km and

distDecay = 1.7M 2.5+ aftershocksSlide10

Fault points for the Northridge earthquake

M 2.0+ aftershocksSlide11

Fault points for a simulated Northridge earthquake with

minDist

= 0.3 km and

distDecay = 1.7M 2.5+ aftershocksSlide12

Data and simulation comparison: Landers earthquake

Aftershock density decays more quickly in the near field, and more slowly in the far field, than any of the simulations

Suggests we need dmin

<0.3 km, distDecay<1.7

Real dataSlide13

Data and simulation comparison: Northridge earthquake

Aftershock density decay rate

is similar to the

distDecay

=2.0

and

distDecay

=2.5 simulations in the near field

Far field decay is closest to the

distDecay

=2.5 simulation.

Different results than for Landers!!

Real dataSlide14

How similar is the aftershock decay for different real earthquakes?

I compare aftershock density vs. distance for Landers, Hector Mine, Northridge, and Joshua Tree.

Each

earthquake is different, but Hector Mine and Joshua Tree are closer to Northridge-type than Landers-type behavior:

supports

distDecay

=2.0-2.5.

Big Bear aftershock may be an issue?Slide15

Future work

Refine method for finding fault points.

Do aftershock measurements for many more large to moderate

mainshocks.Do measurements with relocated aftershocks.Test sensitivity of results to minimum magnitude and duration of aftershocks used.Look for systematic variation of aftershock behavior with mainshock characteristics.Decide whether sequence-specific parameters will be necessary.