Ilya ZaliapinDepartment of Mathematics and Statistics

University of Nevada, Reno

IUGG General Assembly * Monday, June 29, 2015

Yehuda Ben-ZionDepartment of Earth Sciences

University of Southern California

Distinguishing artifacts of earthquake catalog errors from genuine seismicity patterns

Data:southern California catalog by

Hauksson, Yang, Shearer (2013) 117,076 earthquakes with m ≥ 2

Alternate catalogs:

Richards-Dinger & Shearer (2000)ANSS 1961-1981ANSS 1981-2013

Baiesi and Paczuski, PRE, 69, 066106 (2004)Zaliapin et al., PRL, 101, 018501 (2008)

Zaliapin and Ben-Zion, GJI, 185, 1288–1304 (2011)Zaliapin and Ben-Zion, JGR, 118, 2847-2864 (2013)

10 , 0ibmdr

(Fractal) dimension of epicenters

Intercurrence time Spatial distance Gutenberg-Richter law

[M. Baiesi and M. Paczuski, PRE, 69, 066106 (2004)]

/2 /2Rescaled time 10 , Rescaled distance 10i ibm bmdT R r

[Zaliapin et al., PRL, 101, 018501 (2008)]

, log log logTR T R

Distance from an earthquake j to an earlier earthquake i :

Definition:

Property:

Separation of clustered and background parts in southern California

Background = weak links(as in stationary,

inhomogeneous Poisson process)

Clustered part = strong links (events are much closer to each

other than in the background part)

Zaliapin and Ben-Zion, JGR (2013)

Zaliapin et al., PRL (2008)

Two types of earthquake location errors

Median error 500 m

convenient measure of relative location quality rather than actual errors

Spatial variability of absolute horizontal error in southern California

Los Angeles

San Diego

Artifact 1: Inflated distance-to-parent

Artifact 1: Inflated distance-to-parent

Error = 100m

Error > 1km

Artifact 2: Underestimated productivity

Artifact 2: Underestimated productivity

Artifact 3: Overestimated background rate

Artifact 4: Short-term incompleteness

Close offspring

Distant offspring

Frequency-size distribution

Temporal evolution of b-value

Comparative analysis of alternate catalogs

Two types of catalog uncertainties:1

2

3

Four artifacts of catalog uncertainties:

1

2

3

Summary

o Earthquake location errorso Short-term incompleteness

o Increased distance between parent and offspringo Decreased clustering (productivity)o Increased background rateo Apparent changes of b-value

44

Results seem to be independent of earthquake location method and parent-offspring identification approach

Ongoing application to the problem of discriminating between tectonic and induced seismicity

Ref: Zaliapin & Ben-Zion (2015) Artifacts of earthquake location errors and short-term incompleteness on seismicity clusters in southern California, Geophys. J. Intl., to appear

Artifact 2: Underestimated productivity

Artifact 3: Overestimated background rate