# Coseismic and Early Postseismic Deformation of the 2020 Mw 6.4 Petrinja Earthquake (Croatia) Revealed by InSAR

^{1}

^{2}

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## Abstract

**:**

## 1. Introduction

## 2. Data and Methods

#### 2.1. InSAR Data

#### 2.2. Fault Model

## 3. Results

#### 3.1. Coseismic Deformation Field

#### 3.2. Coseismic Slip Model

^{18}N m, corresponding to an Mw 6.4 magnitude earthquake, which is in agreement with the seismic results from USGS and GCMT. Our preferred fault parameters are close to those obtained by Xiong et al. [23].

#### 3.3. Postseismic Deformation

## 4. Discussion

^{18}N m, equivalent to Mw 6.4, slightly larger than the seismic moment from USGS.

^{10}N/m

^{2}, respectively.

## 5. Conclusions

## Author Contributions

## Funding

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

## References

- Tondi, E.; Blumetti, A.M.; Čičak, M.; Di Manna, P.; Galli, P.; Invernizzi, C.; Mazzoli, S.; Piccardi, L.; Valentini, G.; Vittori, E.; et al. ‘Conjugate’ coseismic surface faulting related with the 29 December 2020, Mw 6.4, Petrinja earthquake (Sisak-Moslavina, Croatia). Sci. Rep.
**2021**, 11, 9150. [Google Scholar] [CrossRef] [PubMed] - Baize, S.; Amoroso, S.; Belić, N.; Benedetti, L.; Boncio, P.; Budić, M.; Cinti, F.R.; Henriquet, M.; Rupnik, P.J.; Kordić, B.; et al. Environmental effects and seismogenic source characterization of the December 2020 earthquake sequence near Petrinja, Croatia. Geophys. J. Int.
**2022**, 230, 1394–1418. [Google Scholar] [CrossRef] - Ganas, A.; Elias, P.; Valkaniotis, S.; Tsironi, V.; Karasante, I.; Briole, P. Petrinja earthquake moved crust 10 feet. Temblor
**2021**. [Google Scholar] [CrossRef] - Herak, D.; Herak, M.; Tomljenović, B. Seismicity and earthquake focal mechanisms in North-Western Croatia. Tectonophysics
**2009**, 485, 212–220. [Google Scholar] [CrossRef] - Métois, M.; D’Agostino, N.; Avallone, A.; Chamot-Rooke, N.; Rabaute, A.; Duni, L.; Kuka, N.; Koci, R.; Georgiev, I. Insights on continental collisional processes from GPS data: Dynamics of the peri-Adriatic belts. J. Geophys. Res. Solid Earth
**2015**, 120, 8701–8719. [Google Scholar] [CrossRef] - Bennett, R.A.; Hreinsdóttir, S.; Buble, G.; Bačić, T.; Marjanović, M.; Casale, G.; Gendaszek, A.; Cowan, D. Eocene to present subduction of southern Adria mantle lithosphere beneath the Dinarides. Geology
**2008**, 36, 3–6. [Google Scholar] [CrossRef] - Battaglia, M.; Murray, M.H.; Serpelloni, E.; Burgmann, R. The Adriatic region: An independent microplate within the Africa-Eurasia collision zone. Geophys. Res. Lett.
**2004**, 31, L09605. [Google Scholar] [CrossRef] - Barnhart, W.D.; Hayes, G.P.; Gold, R.D. The July 2019 Ridgecrest, California, earthquake sequence: Kinematics of slip and stressing in cross-fault ruptures. Geophys. Res. Lett.
**2019**, 46, 11859–11867. [Google Scholar] [CrossRef] - Govorčin, M.; Wdowinski, S.; Matoš, B.; Funning, G.J. Geodetic source modeling of the 2019 Mw 6.3 Durrës, Albania, earthquake: Partial rupture of a blind reverse fault. Geophys. Res. Lett.
**2020**, 47, e2020GL088990. [Google Scholar] [CrossRef] - Fathian, A.; Atzori, S.; Nazari, H.; Reicherter, K.; Salvi, S.; Svigkas, N.; Tatar, M.; Tolomei, C.; Yaminifard, F. Complex co- and postseismic faulting of the 2017–2018 seismic sequence in western Iran revealed by InSAR and seismic data. Remote Sens. Environ.
**2021**, 253, 112224. [Google Scholar] [CrossRef] - Milliner, C.; Bürgmann, R.; Inbal, A.; Wang, T.; Liang, C. Resolving the kinematics and moment release of early afterslip within the first hours following the 2016 Mw 7.1 Kumamoto earthquake: Implications for the shallow slip deficit and frictional behavior of aseismic creep. J. Geophys. Res. Solid Earth
**2020**, 125, e2019JB018928. [Google Scholar] [CrossRef] - Rosen, P.A.; Gurrola, E.; Sacco, G.F.; Zebker, H. The InSAR scientific computing environment. In Proceedings of the EUSAR 2012—9th European Conference on Synthetic Aperture Radar, Nuremberg, Germany, 23–26 April 2012; pp. 730–733. [Google Scholar]
- Massonnet, D.; Rossi, M.; Carmona, C.; Adragna, F.; Peltzer, G.; Feigl, K.; Rabaute, T. The displacement field of the Landers earthquake mapped by radar interferometry. Nature
**1993**, 364, 138–142. [Google Scholar] [CrossRef] - Farr, T.G.; Rosen, P.A.; Caro, E.; Crippen, R.; Duren, R.; Hensley, S.; Kobrick, M.; Paller, M.; Rodríguez, E.; Roth, L.; et al. The Shuttle Radar Topography Mission. Rev. Geophys.
**2007**, 45, 361. [Google Scholar] [CrossRef] - Goldstein, R.M.; Werner, C.L. Radar interferogram filtering for geophysical applications. Geophys. Res. Lett.
**1998**, 25, 4035–4038. [Google Scholar] [CrossRef] - Chen, C.W.; Zebker, H.A. Network approaches to two-dimensional phase unwrapping: Intractability and two new algorithms. JOSA A
**2000**, 17, 401–414. [Google Scholar] [CrossRef] - Okada, Y. Surface deformation due to shear and tensile faults in a half-space. Bull. Seismol. Soc. Am.
**1985**, 75, 1135–1154. [Google Scholar] [CrossRef] - Feng, W.; Li, Z.; Elliott, J.R.; Fukushima, Y.; Hoey, T.; Singleton, A.; Cook, R.; Xu, Z. The 2011MW 6.8 Burma earthquake: Fault constraints provided by multiple SAR techniques. Geophys. J. Int.
**2013**, 195, 650–660. [Google Scholar] [CrossRef] - Lohman, R.B.; Simons, M. Some thoughts on the use of InSAR data to constrain models of surface deformation: Noise structure and data downsampling. Geochem. Geophys. Geosystems
**2005**, 6, 1–12. [Google Scholar] [CrossRef] - Parsons, B.; Wright, T.; Rowe, P.; Andrews, J.; Jackson, J.; Walker, R.; Khatib, M.; Talebian, M.; Bergman, E.; Engdahl, E.R. The 1994 Sefidabeh (Eastern Iran) earthquakes revisited: New evidence from satellite radar interferometry and carbonate dating about the growth of an active fold above a blind thrust fault. Geophys. J. Int.
**2005**, 164, 202–217. [Google Scholar] [CrossRef] - Fujiwara, S.; Nishimura, T.; Murakami, M.; Nakagawa, H.; Tobita, M.; Rosen, P.A. 2.5-D surface deformation of M6.1 earthquake near Mt Iwate detected by SAR interferometry. Geophys. Res. Lett.
**2000**, 27, 2049–2052. [Google Scholar] [CrossRef] - Wen, Y.; Xu, C.; Liu, Y.; Jiang, G. Deformation and source parameters of the 2015 Mw 6.5 earthquake in Pishan, Western China, from sentinel-1A and ALOS-2 data. Remote Sens.
**2016**, 8, 134. [Google Scholar] [CrossRef] - Xiong, W.; Yu, P.; Chen, W.; Liu, G.; Zhao, B.; Nie, Z.; Qiao, X. The 2020 Mw 6.4 Petrinja earthquake: A dextral event with large coseismic slip highlights a complex fault system in northwestern Croatia. Geophys. J. Int.
**2022**, 228, 1935–1945. [Google Scholar] [CrossRef] - Jin, Z.; Fialko, Y. Coseismic and early postseismic deformation due to the 2021 M7.4 Maduo (China) earthquake. Geophys. Res. Lett.
**2021**, 48, e2021GL095213. [Google Scholar] [CrossRef] - Berardino, P.; Fornaro, G.; Lanari, R.; Sansosti, E. A new algorithm for surface deformation monitoring based on small baseline differential SAR interferograms. IEEE Trans. Geosci. Remote Sens.
**2002**, 40, 2375–2383. [Google Scholar] [CrossRef] - Zhang, Y.J.; Fattahi, H.; Amelung, F. Small baseline InSAR time series analysis: Unwrapping error correction and noise reduction. Comput. Geosci.
**2019**, 133, 104331. [Google Scholar] - Feng, W.; Samsonov, S.; Almeida, R.; Yassaghi, A.; Li, J.; Qiu, Q.; Li, P.; Zheng, W. Geodetic constraints of the 2017 Mw 7.3 Sarpol Zahab, Iran earthquake, and its implications on the structure and mechanics of the northwest Zagros thrust-fold belt. Geophys. Res. Lett.
**2018**, 45, 6853–6861. [Google Scholar] [CrossRef] - Zhou, Y.; Thomas, M.Y.; Parsons, B.; Walker, R.T. Time-dependent postseismic slip following the 1978 Mw 7.3 Tabas-e-Golshan, Iran earthquake revealed by over 20 years of ESA InSAR observations. Earth Planet. Sci. Lett.
**2018**, 483, 64–75. [Google Scholar] [CrossRef] - Toda, S.; Stein, R.S.; Sevilgen, V.; Lin, J. Coulomb 3.3 Graphic-Rich Deformation and Stress-Change Software for Earthquake, Tectonic, and Volcano Research and Teaching-User Guide: U.S. Geological Survey Open-File Report 2011–1060. Available online: https://pubs.usgs.gov/of/2011/1060/ (accessed on 15 May 2023).
- King, G.C.P.; Stein, R.S.; Lin, J. Static stress changes and the triggering of earthquakes. Bull. Seismol. Soc. Am.
**1994**, 84, 935–953. [Google Scholar] - Stein, R.S. The role of stress transfer in earthquake occurrence. Nature
**1999**, 402, 605–609. [Google Scholar] [CrossRef] - Weber, J.; Vrabec, M.; Pavlovčič-Prešeren, P.; Dixon, T.; Jiang, Y.; Stopar, B. GPS-derived motion of the Adriatic microplate from Istria Peninsula and Po Plain sites, and geodynamic implications. Tectonophysics
**2010**, 483, 214–222. [Google Scholar] [CrossRef]

**Figure 1.**Location map showing shaded topography, the focal mechanism of the Petrinja 29 December 2020, earthquake (Mw = 6.4) from different agencies. White rectangles indicate coverage of Sentinel-1 SAR data (two ascending track P073A, P146A, and one descending track P124D). The faults are denoted by solid black lines (from https://seismofaults.eu/edsf13data, accessed on 15 May 2023). Petrinja is represented by the yellow star. Zagreb, the capital city of Croatia, is represented by the white circle. Inset box indicates the location of earthquake area within Croatia.

**Figure 2.**The coseismic interferograms of the Petrinja earthquake. (

**a**) shows the image pair 20201225–20201231 (ascending orbit 73). (

**b**): 20201223–20210104 (descending orbit 124). (

**c**): 20201224–20201230 (ascending orbit 146). The white solid lines indicate the locations of two faults.

**Figure 3.**2.5-D ground surface displacements of the 2020 Mw 6.4 Petrinja earthquake. (

**a**) East–west and (

**b**) vertical displacement components derived from the Sentinel-1 interferograms. The black beach balls with names mark the epicenter of the mainshock from different agencies. The red solid lines indicate the locations of two faults. Aftershocks are shown in black circles.

**Figure 4.**Slip distribution model (

**a**) and its standard deviations (

**b**) of the 2020 Petrinja earthquake from Monte Carlo estimation.

**Figure 5.**Observational (

**a**–

**c**), synthetic (

**d**–

**f**) and residual (

**g**–

**i**) interferograms of our preferred fault model.

**Figure 7.**InSAR maps obtained from different tracks showing postseismic deformation in the first 6 days of after the mainshock. (

**a**) P073A. (

**b**) P124D. (

**c**) P146A.

**Figure 8.**Baseline plots of selected interferograms from two Sentinel-1 tracks. Circles are selected SAR acquisitions: 29 for ascending track 73, and 30 for descending track 124.

**Figure 9.**Postseismic deformation series with respect to the date of first postseismic acquisition 20201231 in 6 months after the main event from ascending track P073A. The black rectangle denotes the location of reference point.

**Figure 10.**Postseismic deformation series with respect to the date of the first postseismic acquisition 20210104 in 6 months after the main event from descending track P124D. The black rectangle denotes the location of reference point.

**Figure 11.**(

**a**,

**b**) Average velocity and its standard deviation of postseismic deformation in the ascending track P073A. The black rectangle denotes the location of reference point.

**Figure 12.**(

**a**,

**b**) Average velocity and its standard deviation of postseismic deformation in the descending track P124D. The black rectangle denotes the location of reference point.

**Figure 13.**Predicted LOS displacements in each track caused by poroelastic rebound for the 2020 Petrinja earthquake. The black rectangle denotes the surface projection of distributed slip model. (

**a**) P073A. (

**b**) P124D. (

**c**) P146A.

**Figure 14.**Coulomb failure stress change caused by the 2020 Mw 6.4 Petrinja earthquake. The black circles denote the location of relocated aftershocks obtained from EMSC (https://www.emsc-csem.org/, accessed on 15 May 2023).

Lon. | Lat. | Depth | Strike | Dip | Rake | Length | Width | ||
---|---|---|---|---|---|---|---|---|---|

Source | (°) | (°) | (km) | (°) | (°) | (°) | (km) | (km) | Mw |

224 | 89 | 14 | |||||||

USGS | 16.255 | 45.422 | 13.5 | 134 | 76 | 179 | - | - | 6.4 |

223 | 82 | 8 | |||||||

GCMT | 16.21 | 45.38 | 12 | 132 | 82 | 172 | - | - | 6.4 |

40 | 77 | −6 | |||||||

GFZ | 16.2 | 45.47 | 11 | 131 | 83 | −167 | - | - | 6.4 |

131 | 71 | 176 | |||||||

INGV | 16.2 | 45.39 | 14.9 | 223 | 86 | 19 | - | - | 6.4 |

223 | 82 | 3 | |||||||

IPGP | 16.298 | 45.412 | 13 | 133 | 87 | 172 | - | - | 6.4 |

40 | 90 | 20 | |||||||

OCA | 16.2 | 45.47 | 8 | 130 | 70 | 180 | - | - | 6.5 |

139 | 68 | −164 | |||||||

BMKG | 16.21 | 45.48 | 10 | 43 | 76 | −23 | - | - | 6.3 |

16.255 | 45.422 | 0.5 | 134 | 82 | 179 | 8.2 | 5.3 | 6.4 | |

Uniform | −0.3 | −0.2 | −0.2 | −0.4 | −1.8 | - | −0.3 | −0.1 | |

+0.3 | +0.2 | +0.4 | +0.6 | +1.2 | +0.3 | +0.4 | |||

Distributed | 16.255 | 45.422 | 0 | 134 | 82 | 179 | 30 | 20 | 6.4 |

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**MDPI and ACS Style**

Zhu, S.; Wen, Y.; Gong, X.; Liu, J.
Coseismic and Early Postseismic Deformation of the 2020 Mw 6.4 Petrinja Earthquake (Croatia) Revealed by InSAR. *Remote Sens.* **2023**, *15*, 2617.
https://doi.org/10.3390/rs15102617

**AMA Style**

Zhu S, Wen Y, Gong X, Liu J.
Coseismic and Early Postseismic Deformation of the 2020 Mw 6.4 Petrinja Earthquake (Croatia) Revealed by InSAR. *Remote Sensing*. 2023; 15(10):2617.
https://doi.org/10.3390/rs15102617

**Chicago/Turabian Style**

Zhu, Sen, Yangmao Wen, Xiaodong Gong, and Jingbin Liu.
2023. "Coseismic and Early Postseismic Deformation of the 2020 Mw 6.4 Petrinja Earthquake (Croatia) Revealed by InSAR" *Remote Sensing* 15, no. 10: 2617.
https://doi.org/10.3390/rs15102617