EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Quantifying preparation process of large earthquakes: Damage localization and coalescent dynamics

Ilya Zaliapin1 and Yehuda Ben-Zion2
Ilya Zaliapin and Yehuda Ben-Zion
  • 1University of Nevada, Reno, Department of Mathematics and Statistics, Reno, United States of America (
  • 2University of Southern California, Department of Earth Sciences, Los Angeles, United States of America (

We attempt to track and quantify preparation processes leading to large earthquakes using two complementary approaches. (a) Localization of brittle deformation manifested by evolving fractional volume with seismic activity, and (b) Coalescence of earthquakes into clusters. We analyze seismicity catalogs from Southern California (SoCal), Parkfield section of the San Andreas Fault (SAF), and region around the 1999 Izmit and Duzce earthquakes in Turkey.

Localization of deformation is estimated using the Receiver Operating Characteristic (ROC) approach. Specifically, we consider temporal evolution of the fractional volume 0 ≤ V(q) ≤ 1 occupied by the fraction 0 ≤ q ≤ 1 of active voxels with mainshocks. We also consider the localization of the spatial intensity of mainshocks within a sliding time window with respect to the time-averaged distribution, quantified by Gini coefficient G. The significance of the results is assessed using reshuffled catalogs. Analysis within the rupture zones of large earthquakes indicate decrease of V(q) and increase of G (increased localization) prior to the Landers (1992, M7.3), El Mayor-Cucapah (2010, M7.2), Ridgecrest (2019, M7.1), and Duzce (1999, M7.2) mainshocks. We also observe ongoing damage production by the background seismicity around these rupture zones several years before their occurrences. In contrast, we observe increase of V(q) and decrease of G prior to the Parkfield (2004, M6.0) mainshock in the creeping section of the SAF. Next, we examine the quasi-linear region in the Eastern part of Southern California around the Imperial fault, Brawley seismic zone, southern SAF and Eastern California Shear Zone. We document four cycles of background localization, measures by V(q) and G, well aligned in time with the largest events in the region: Landers, Hector Mine, El Mayor-Cucapah, and Ridgecrest. The coalescence process is represented by a time-oriented graph that connects each earthquake in the examined catalog to all earlier earthquakes at the earthquake nearest-neighbor proximity below a specified threshold. We examine the size of the clusters that correspond to low thresholds, and hence represent active clustering episodes. We document increase of the average cluster size prior to the Landers, El Mayor-Cucapah, Ridgecrest and Duzce mainshocks, and decrease of the average cluster size prior to the Parkfield mainshock.

The results of our complementary localization and coalescent analyses consistently indicate progressive localization of damage prior to the largest earthquakes on non-creeping faults and de-localization on the creeping Parkfield section of SAF. These findings are consistent with analysis of acoustic emission data. The study is a step towards developing methodology for analyzing the dynamics of seismicity in relation to preparation processes of large earthquakes, which is robust to spatio-temporal fluctuations associated with aftershock sequences, data incompleteness and common catalog errors.

How to cite: Zaliapin, I. and Ben-Zion, Y.: Quantifying preparation process of large earthquakes: Damage localization and coalescent dynamics, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12056,, 2020

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  • CC1: Comment on EGU2020-12056, Paul Selvadurai, 04 May 2020

    Very intriguing study linking volumetric preporatory processes of large earthquakes in Califronia.

    My question is regarding the variable gamma = 1/500 from Ben-Zion and Ampuero (2009) (slide 5). Could this parameter change after a larger event (M>7) leaves substantial overprint damage that results in significant variations in the near-fault material properties local to the rupture? 

    Apologies if I have misinterpreted this concept. Thank you in advance.

    • AC1: Reply to Paul Selvadurai, Ilya Zaliapin, 04 May 2020

      Thanks for the comment.

      The number (1/500)  is within a range of values that depend on various other parameters (e.g. rupture velocity) and to some extent also on the pre-existing damage. The used value is a representative number.  Laboratory experiments and seismic imaging studies indicate rapid post-failure healing at seismogenic depth. Residual pre-existing damage may be important at shallow depth.

      • CC2: Reply to AC1, Paul Selvadurai, 04 May 2020

        Thanks you very much for th quick response.

        Is this rapid healing near-fault the "cementation" of pulverized/highly-damaged rock that also shows dramatic decrease in permeability in the damage zone? Observations made in the field of structural geolgogy by researcher like Prof. Tom Mitchell?  

        Could you please point me to a lab study? I also perform lab studies and am interested in exactly the porblem you and Prof. Ben-Zion are looking at there. This is direction that we are moving toewards with new acoustic emission studies (if you are interested on the new methodologies: ).

        Thank you again kindly.

        • CC3: Reply to CC2, Paul Selvadurai, 04 May 2020

          Apologies, I guess links are not allowable, the litterature I was mentioning:

          Selvadurai, P. A. ( 2019). Laboratory insight into seismic estimates of energy partitioning during dynamic rupture: An observable scaling breakdownJournal of Geophysical Research: Solid Earth12411350– 11379.

          We can employ Brune's (Omega) models down to Mw -9 to -7.