Mw7.2 Nippes, Haiti Earthquake:

Sentinel-1 and ALOS-2 Interferometry


H. Zoe Yin1, Xioahua Xu2, Jennifer S. Haase1, David T. Sandwell1

1Institute for Geophysics and Planetary Physics, University of California, San Diego, USA

2University of Texas Institute for Geophysics, Austin, USA

IGPP nsf-logo

The Mw7.2 Nippes, Haiti earthquake struck on August 14, 2021 (8:29 am local time) on Haiti's southwest peninsula. The earthquake occurred 125 km west of Port-au-Prince at a depth of 10 km with an oblique thrust faulting mechanism. The earthquake occurred along the Enriquillo-Plantain Garden fault (EPGF) zone, about 100 km west of the Mw7.0 2010 Haiti earthquake.

Two InSAR satellites were operational before the earthquake and continue to collect measurements of line-of-sight (LOS) deformation. The C-band Sentinel-1 satellites, operated by the European Space Agency (ESA), provide a 6-day coverage (ascending and descending tracks) of the earthquake sequence. These data are available on the Sentinel Data Hub. The L-band ALOS-2 satellite, operated by the Japanese Aerospace Exploration Agency (JAXA), collected ascending ScanSAR data can be found on the ALOS-2 User Interface Gateway.

This page is to provide near-real time line-of-sight deformation data from Sentinel-1 and ALOS-2. We will continue to provide images for each repeat pass and update the line-of-sight data once they are available.  The InSAR data are processed with open source software GMTSAR and mapped using Generic Mapping Tools (GMT). The InSAR phase are filtered with a 300 m Gaussian filter. The line-of-sight data are acquired by merging different swaths' phase and then unwrapped using snaphu. We also include KMZ files for Google Earth with some preliminary interpretation. These will be updated as more remote sensing and field data refines these interpretations.

The earthquake ruptured ~80 km from Nippes towards the west, in two main slip patches with primarily dip-slip in the east and strike slip in the west (USGS) (https://earthquake.usgs.gov/earthquakes/eventpage/us6000f65h/finite-fault). This pattern is clearly seen in the second interferogram with a large region of uplift in the east (towards the satellite in the LoS) and dominantly strike slip in the west (away from the satellite in the LoS. 

The EPGF is part of the system of strike slip and thurst faults that constitute the northeast boundary of the Caribbean tectonic plate. The plate boundary transitions from pure strike slip south of Cuba to subduction in the Antilles. The slip rate along the EPGF fault zone determined from GPS data is 10-11.4 mm/yr of oblique motion (Symithe et al., 2016). The rupture leaves a ~60 km segment of the EPGF unruptured between this and the 2010 Haiti M7.0 earthquake rupture on the Leogane fault (Symithe et al, 2015). Given the time since the historic earthquakes in 1701, 1751 and 1770 on this plate boundary (Manaker et al., 2008), there remains accumulated strain on the unruptured Mirogoane segment to the east of the August 14 event.

overview
Overview of the southern peninsula of Haiti, highlighting the epicenters of the 2021 M7.2 and 2010 M7.0 earthquakes and major historic earthquakes (red stars). Aftershocks from 2010 on the Léogane – Trois Baies fault are from Douilly et al. (2013). Aftershocks from 2021 are from the Ayiti-Séismes network. Mapped EPGFZ faults (black lines) are from Saint Fleur et al. (2020). The rupture zones do not align with the previously understood segmentation of the Enriquillo Plantain Garden Fault Zone. Instead, the rupture zones highlight a broad zone of strike-slip and secondary thrust features comprising the transpressional plate boundary. Original segmentation into the Macaya-Tiburon Segment (MTS), Clonard-Macaya Segment (CMS), Miragoâne-Clonard Segment (MCS) and Pietonville-Léogane Segment (PVLS) is taken from Saint Fleur et al. (2020). The range of event depths is indicated for 0 km (blue) to 18 km (yellow)

Data

We compile Sentinel-1 and ALOS-2 repeat acquisitions surrounding the time of the 2021 earthquake and use GMTSAR software to process the raw data. Interferograms are Gaussian filtered at 200 m and re-sampled at 50 m before further processing. We unwrap the phase using the Statistical-Cost, Network-Flow Algorithm for Phase Unwrapping (SNAPHU), with nearest neighbor interpolation over the low coherence areas and water surfaces. The resulting LOS plots below show surface deformation in the line-of-sight of the observing satellite, where positive indicates that the ground pixel has moved towards the satellite.

timeline
Timeline of all SAR scene acquisitions used in this work with the vertical red dashed line marking the Aug 14 earthquake. Sentinel-1 acquisitions are frequent, with ascending and descending acquisitions less than two weeks before the 2021 earthquake. In contrast, ALOS-2 acquisitions are infrequent with the closest usable ALOS-2 acquisitions prior to the earthquake are more than 6 months before the earthquake. Note the breaks in the horizontal axis in grey which represent large time periods between ALOS-2 acquisitions.

Google Earth Project Download

Download a Google Earth project file containing all InSAR pairs included below as layers. Also includes features picked from these pairs and other published resources to contextualize the InSAR data.

Most recent Google Earth project KMZ files

Download full Google Earth project KMZ file (update from 2022/04/25)
Download full Google Earth project KMZ file (update from 2022/03/20)

Download full Google Earth project KMZ file (update from 2021/09/07)
Download full Google Earth project KMZ file (update from 2021/09/03)
Download full Google Earth project KMZ file (update from 2021/08/23)




ALOS-2 Ascending Track 042 (Stripmap): Pair 2021/01/01 - 2021/08/27   

Co & postseismic & secondary fault structures

PHASE: phasefilt_ll.grd

phasefilt_ll
PHASE GRADIENT: yphase_mask_ll.grd

phase-gradient
LINE OF SIGHT: los_ll.grd

line-of-sight

ALOS-2 Ascending Track 042 (Stripmap): Pair 2021/08/27 - 2021/12/31   

Postsesismic & secondary fault structures
PHASE: phasefilt_ll.grd

phasefilt
PHASE GRADIENT: yphase_mask_ll.grd

phase-gradient
LINE OF SIGHT: los_ll.grd

line-of-sight

ALOS-2 Ascending Track 042 (Stripmap): Pair 2021/01/01 - 2021/12/31

All Co & postseismic (Jan 1 - Dec 31)
PHASE: phasefilt_ll.grd

phasefilt
PHASE GRADIENT: yphase_mask_ll.grd

phase
                                                          gradient
                                                          (azimuth)
LINE OF SIGHT: los_ll_dtr.grd

line-of-sight


ALOS-2 Ascending Track 042 (Stripmap): Phase gradient stack

The gradient of the phase taken in the azimuth (flight) direction and stacked using all ALOS-2 ascending track pairs between Dec 23, 2020 and Dec 31, 2021 (3 pairs for A042 and 5 pairs for A043)
PHASE GRADIENT STACK:  yphase_mask_ll_stack.grd

Phase gradient stack






ALOS-2 Ascending Track 043 (Stripmap): 2020/12/23 - 2021/08/18

Coseismic & surface rupture
PHASE: phasefilt_ll.grd 

phasefilt
PHASE GRADIENT:  yphase_mask_ll_2020-12-23_2021-08-18.grd

phase grad
LINE OF SIGHT: los_ll.grd

LOS

ALOS-2 Ascending Track 043 (Stripmap): Phase gradient stack

The gradient of the phase taken in the azimuth (flight) direction and stacked using all ALOS-2 ascending track pairs between Dec 23, 2020 and Dec 31, 2021 (3 pairs for A042 and 5 pairs for A043)

PHASE GRADIENT STACK:  yphase_mask_ll_stack.grd

Phase
                                                          gradient
                                                          stack








ALOS-2 Descending Track 138 (ScanSAR): 2019/12/10 - 2021/08/17

Coseismic Deformation.
PHASE: phasefilt_ll.grd

Phasefilt

                       PHASE GRADIENT: N/A                                
LINE OF SIGHT: los_ll_dtr.grd

LOS

ALOS-1 Ascending Track 138 (FBD): 2010/01/16 - 2010/06/23

2010 Postseismic Deformation

PHASE: phasefilt_ll.grd

phasefilt

PHASE GRADIENT: yphase_mask_ll.grd

Phase gradient

                                                                                    

Sentinel-1 Descending track D142: 2021/08/03 - 2021/08/15

Descending coseismic interferogram

Download KMZ files for Google Earth: Phase + Coherence Layers + Line-of-Sight (Preliminary) Layers

PHASE: phasefilt_ll.grd

Phase






Sentinel-1 Descending track D142: 2021/08/15 - 2021/08/21

Post-seismic Interferogram
Download KMZ files for Google Earth: Phase + Coherence Layers




 

Sentinel-1 Descending track D142: 2021/08/21 - 2021/08/27

Post-seismic Interferogram

Download KMZ files for Google Earth: Phase + Coherence Layers



Sentinel-1 Ascending track A004: 2021/08/05 - 2021/08/17

Ascending coseismic interferogram

Download KMZ files for Google Earth: Phase + Coherence Layers + Unwrapped Phase (preliminary) Layers






 


Sentinel-1 Ascending track A004: 2021/08/17 - 2021/08/23

Post-seismic Interferogram
Download KMZ files for Google Earth: Phase + Coherence Layers


PHASE: phasefilt_ll.grd

phasefilt




Sentinel-1 Ascending track A004: 2021/08/23 - 2021/08/29

Post-seismic Interferogram
Download KMZ files for Google Earth: Phase + Coherence Layers








Acknowledgements:
Rapid InSAR data processing was supported by a National Science Foundation RAPID grant (Grant #2150704). We thank the operators of the Ayiti-Séismes earthquake monitoring network at Bureau des Mines, Faculté des Sciences, Laboratoire URGéo, Université d'état d'Haïti, Ecole Normale Supérieur, and Laboratoire Géoazur for making aftershock locations free and openly available. We thank Roby Douilly at the University of California Riverside for contributions to aftershock relocations and interpretation of our results. We thank Bernard Mercier de Lepinay for contributions in the interpretation of our results in the geologic context. We thank Sylvert Paul and Francoise Courboulex at GéoAzur, Eric Calais at ENS, and Jeremy Maurer at Missouri University of Science and Technology for helpful discussions related to the earthquake. We thank ESA for the rapid acquisition and distribution of Sentinel-1 data. We thank JAXA for access to ALOS-1 and ALOS-2 data. The development of the GMTSAR software, and specifically the processing chain for Sentinel-1 and ALOS-2, was supported by the National Aeronautics and Space Administration (NASA) and the National Science Foundation through the NASA Earth Surface and Interior program (NNX16AK93G and 80NSSC19K1043), the NSF Office of Advanced Cyberinfrastructure program (OAC-1834807), and the NSF EarthScope program (EAR-1147435, EAR-1424374, EAR-1614875).