Measurement of coseismic deformation by satellite geodesy

Correlation of two SAR backscatter images acquired by the radar satellites such as ERS

A similar correlation technique also applies to SAR images. By correlating two Single Look Complex (SLC) SAR amplitude (“backscatter”) images acquired at different times, Michel et al. [1999a] measured ground displacements for the Landers earthquake. Their result is “a two-dimensional displacement field with independent measurements every about 128 m in azimuth and 250 m in range. The accuracy depends on the characteristics of the images. For the Landers test case discussed in the study, the 1- uncertainty is 0.8 m in range and 0.4 m in azimuth. [They] show that this measurement provides a map of major surface fault ruptures accurate to better than 1 km and an information on coseismic deformation comparable to the 92 GPS measurements available. Although less accurate, this technique is more robust than SAR interferometry and provides a complementary information since interferograms are only sensitive to the displacement in range.” [Michel et al., 1999a]. Its greatest potential is for measuring cryospheric deformation, where flow can be sufficiently rapid ( > 10 cm/day) to allow detection in the short time (1, 3 or 35 days) between ERS acquisitions [Michel, 1997; Michel and Rignot, 1999].

For the Izmit earthquake, however, Sarti et al. [2000] find less accurate results than at Landers. Using multiple scales for their correlation cells, they find the range component of the coseismic displacement with a scatter in excess of a meter. Indeed, it is difficult to discern even the trace of the fault in the map of ERS range offsets (Figure 4). Consequently, Feigl et al. [2001] do not include these data in their inversion.

Figure 4. Component at S77°E of the coseismic displacement field measured by correlation of two ERS images, as described by Sarti et al. (2000). Note that discontinuity in these measurements does not follow the mapped trace of the fault (crosses) as well as the SPOT correlation map [Feigl et al., 2001].

Advances published between 1997 and 2004

Coseismic deformation for earthquakes

INSAR has now captured over a dozen earthquakes in the act of permanently deforming the Earth’s surface (Table 1.)
Table 1. Earthquake studies estimating parameters from satellite geodetic measurements using INSAR as compiled from the literature [Feigl, 2002; Funning, 2005].

Location	MW	Date	InSAR
Landers,CA,USA	7.3	1992-06-28	[Fialko, 2004c]
Litle Skull Mountain, CA, USA	5.6	1992-06-29	[Lohman, et al., 2002]
Fawnskin, CA,USA	5.4	1992-12-02	[Feigl, et al., 1995]
Ngamring County, Tibet	6.1	1993-03-20	[Funning, 2005]
Eureka Valley, CA, USA	6.1	1993-05-17	[Massonnet and Feigl, 1995]
Northridge, CA, USA	6.7	1994-01-17	[Massonnet, et al., 1996]
Double Spring Flat, NV, USA	6.0	1994-09-12	[Amelung and Bell, 2003]
Kobe, Japan	6.9	1995-01-17	[Ozawa, et al., 1997]
Grevena, Greece	6.6	1995-05-13	[Bernard, et al., 1997b]
Neftegorsk, Sakhalin, Russia	7.2	1995-05-27	[Tobita, et al., 1998]
Aigion, Greece	6.2	1995-06-15	[Bernard, et al., 1997a]
Antofagasta, Chile	8.1	1995-07-20	[Pritchard, et al., 2002b]
Dinar, Turkey	6.3	1995-10-01	[Funning, 2005]
Nuweiba, Egypt	7.3	1995-11-22	[Shamir, et al., 2003]
St Paul de Fenouillet, France	5.0	1996-02-26	[Rigo and Massonnet, 1998]
Nazca Ridge, Peru	7.7	1996-11-12	[Delouis, et al., 2002]
Kagoshima-ken-hokuseibu, Japan	6.1	1997-03-26	[Fujiwara, et al., 1998]
Manyi, Tibet	7.5	1997-11-08	[Funning, 2005]
Zhangbei-Shangyi, China	6.2	1998-01-10	[Zhang, et al., 2002]
Fandoqa, Iran	6.6	1998-03-14	[Funning, 2005]
Mt Iwate, Japan	6.1	1998-09-03	[Nishimura, et al., 2001]
Aiquile, Bolivia	6.6	1998-05-22	[Funning, et al., 2005]
Izmit, Turkey	7.4	1999-08-17	[Cakir, et al., 2003]
Athens, Greece	6.0	1999-09-07	[Kontoes, et al., 2000]
Colfiorito, Italy	5.7	1999-09-26	[Salvi, et al., 2000]
Colfiorito, Italy	6.0	1999-09-26	[Salvi, et al., 2000]
Hector Mine, CA, USA	7.1	1999-10-16	[Simons, et al., 2002]
Duzce, Turkey	7.1	1999-11-12	[Bürgmann, et al., 2002]
Cankiri, Turkey	6.0	2000-06-06	[Wright, 2000]
S Iceland Seismic Zone, Iceland	6.5	2000-06-17	[Pedersen, et al., 2003]
S Iceland Seismic Zone, Iceland	6.4	2000-06-21	[Pedersen, et al., 2003]
Nisqually, WA, USA	6.8	2001-02-28	[Bustin, et al., 2004]
Arequipa, Peru	8.5	2001-06-23	[Pritchard, et al., 2002a]
Kokoxili, Tibet	7.8	2001-11-14	[Lasserre, et al., 2002]
Nenana Mountain, AK, USA	6.7	2002-10-23	[Wright, et al., 2003]
Denali, AK, USA	7.9	2002-11-03	[Wright, et al., 2003]
Bam, Iran	6.6	2003-12-26	[Funning, 2005]