toolbox
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| - | Figure 1. (a) The earthquakes with magnitude equal to or greater than 4.0 in western Washington since 1996 (from PNSN catalog). The red, orange, yellow, blue and maybe some dark orchid dots represent continental crust earthquakes. The black and maybe some dark orchid dots represent subducting intraslab earthquakes. The Duvall Mw 5.1 earthquake is noted with a black arrow. (b) The principal Puget Sound faults are delineated with solid or dashed red lines (from http://en.wikipedia.org/wiki/Puget_Sound_faults). The orange dot around the intersection of Cherry Creek Fault Zone (CCFZ) and Rattlesnake Mountain Fault Zone (RMFZ) indicates the location of the Duvall Mw 5.1 main shock and also is noted with a black arrow. | + | **Figure 1.** (a) The earthquakes with magnitude equal to or greater than 4.0 in western Washington since 1996 (from PNSN catalog). The red, orange, yellow, blue and maybe some dark orchid dots represent continental crust earthquakes. The black and maybe some dark orchid dots represent subducting intraslab earthquakes. The Duvall Mw 5.1 earthquake is noted with a black arrow. (b) The principal Puget Sound faults are delineated with solid or dashed red lines (from http://en.wikipedia.org/wiki/Puget_Sound_faults). The orange dot around the intersection of Cherry Creek Fault Zone (CCFZ) and Rattlesnake Mountain Fault Zone (RMFZ) indicates the location of the Duvall Mw 5.1 main shock and also is noted with a black arrow. |
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| - | Figure 2. Duvall Mw 5.1 main shock and the aftershock sequence. (a) Spatial distribution of the seismicity in 1996. The meanings of different colors are same as those in figure 1(a). A-B is a profile with events only within the rectangular box analyzed in (b), (c) and (d). (b) A west-east depth profile shows the depth distribution of the events within the rectangular box in (a). Notice that the seismicity geometry clearly delineates an eastward dipping fault plane. (c) The timeline of the magnitude across the whole year 1996. Notice that the Duvall Mw 5.1 main shock was followed by a lot of aftershocks and the aftershocks continued at least to the end of the year 1996. (d) Cumulative quake number of the earthquake sequence within the profile box. | + | **Figure 2.** Duvall Mw 5.1 main shock and the aftershock sequence. (a) Spatial distribution of the seismicity in 1996. The meanings of different colors are same as those in figure 1(a). A-B is a profile with events only within the rectangular box analyzed in (b), ( c) and (d). (b) A west-east depth profile shows the depth distribution of the events within the rectangular box in (a). Notice that the seismicity geometry clearly delineates an eastward dipping fault plane. ('c') The timeline of the magnitude across the whole year 1996. Notice that the Duvall Mw 5.1 main shock was followed by a lot of aftershocks and the aftershocks continued at least to the end of the year 1996. (d) Cumulative quake number of the earthquake sequence within the profile box. |
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| The Duvall earthquake occurred about 10 km east of Duvall, Washington on May 3, 1996. The quake area was imaged both before and after the main shock by satellites ERS 1 and ERS 2. We collect four SAR scenes spanning the earthquake, two of which are about one month before the quake and the other two scenes are about one week after the quake. Because the event is located at the edge of the frame, we merged two frames to achieve scenes continuously mapping the Duvall earthquake. The details of the four scenes are shown in table 1. We make a combination of the different SAR scenes before and after the earthquake, and get four date pairs scenes to process for potential interferograms. The date pair scenes must share the same track and frame. These date pairs are shown in table 2. Notice that the perpendicular baseline for each scene pair might be too big to achieve a highly correlated interferograms. We will analyze the baseline effect on the correlation of the phase later in the discussion section. | The Duvall earthquake occurred about 10 km east of Duvall, Washington on May 3, 1996. The quake area was imaged both before and after the main shock by satellites ERS 1 and ERS 2. We collect four SAR scenes spanning the earthquake, two of which are about one month before the quake and the other two scenes are about one week after the quake. Because the event is located at the edge of the frame, we merged two frames to achieve scenes continuously mapping the Duvall earthquake. The details of the four scenes are shown in table 1. We make a combination of the different SAR scenes before and after the earthquake, and get four date pairs scenes to process for potential interferograms. The date pair scenes must share the same track and frame. These date pairs are shown in table 2. Notice that the perpendicular baseline for each scene pair might be too big to achieve a highly correlated interferograms. We will analyze the baseline effect on the correlation of the phase later in the discussion section. | ||
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| + | {{:jiangang:Slide1.png|}} {{:jiangang:Slide2.png|}} | ||
| To obtain the interferogram for each date pair, we perform standard processing both for the master scene and the slave scene with the Repeat Orbit Interferometry Package (ROI_PAC). The interferometric phase contains a topography component that needs to be corrected to get a differential interferogram for deformation interpretation. We first construct digital elevation model (DEM) for the study area using data from Shuttle Radar Topography Mapping (SRTM) mission (http://dds.cr.usgs.gov/srtm). Then we use this DEM and the ROI_PAC to estimate and remove the topography contribution to the interferometric phase. | To obtain the interferogram for each date pair, we perform standard processing both for the master scene and the slave scene with the Repeat Orbit Interferometry Package (ROI_PAC). The interferometric phase contains a topography component that needs to be corrected to get a differential interferogram for deformation interpretation. We first construct digital elevation model (DEM) for the study area using data from Shuttle Radar Topography Mapping (SRTM) mission (http://dds.cr.usgs.gov/srtm). Then we use this DEM and the ROI_PAC to estimate and remove the topography contribution to the interferometric phase. | ||
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| {{:jiangang:fig3.png|}} | {{:jiangang:fig3.png|}} | ||
| - | Figure 3. Interferogram wrapped phase using (a) SAR scenes of April 4, 1996 and May 9, 1996; (b) SAR scenes of April 4, 1996 and May 10, 1996; (c) SAR scenes of April 5, 1996 and May 9, 1996; (d) SAR scenes of April 5, 1996 and May 10, 1996. All of the four interferograms show low phase corrlation at the epicenter region. | + | **Figure 3.** Interferogram wrapped phase using (a) SAR scenes of April 4, 1996 and May 9, 1996; (b) SAR scenes of April 4, 1996 and May 10, 1996; (c) SAR scenes of April 5, 1996 and May 9, 1996; (d) SAR scenes of April 5, 1996 and May 10, 1996. All of the four interferograms show low phase corrlation at the epicenter region. |
| {{:jiangang:fig4.png|}} | {{:jiangang:fig4.png|}} | ||
| - | Figure 4. Interferogram amplitude and phase. (a) The amplitude stacking of the four interferograms. The orange dot represents the Duvall earthquake location. (b) The phase stacking of the four interferograms in fiure 3. Notice that the correlation is still low, at least near the epicenter of the earthquake. (c) Interferogram phase using SAR scenes of 1996.04.04 and 1996.04.05. For this date pair the correlation is high, probably because of the short perpendicular baseline (only 66 m) and short time span (only one day). (d) Interferogram phase using SAR scenes of 1996.05.09 and 1996.05.10. The correlation for this scene pair is also high, with same reason of short perpendicular baseline (about 143 m) and short period (only one day). | + | **Figure 4.** Interferogram amplitude and phase. (a) The amplitude stacking of the four interferograms. The orange dot represents the Duvall earthquake location. (b) The phase stacking of the four interferograms in fiure 3. Notice that the correlation is still low, at least near the epicenter of the earthquake. (c) Interferogram phase using SAR scenes of 1996.04.04 and 1996.04.05. For this date pair the correlation is high, probably because of the short perpendicular baseline (only 66 m) and short time span (only one day). (d) Interferogram phase using SAR scenes of 1996.05.09 and 1996.05.10. The correlation for this scene pair is also high, with same reason of short perpendicular baseline (about 143 m) and short period (only one day). |
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| - | Figure 5. Forward modeling of the interferograms for Duvall earthquake at different depth. The strike, dip, rake, slip and length of the fault for the two modeling are set to be the same, but with different depth range. (a) The earthquake fault is put at a depth between 8.7-11.1 km. (b) The earthquake fault is put at a depth between 2.6-5.0 km. | + | **Figure 5.** Forward modeling of the interferograms for Duvall earthquake at different depth. The strike, dip, rake, slip and length of the fault for the two modeling are set to be the same, but with different depth range. (a) The earthquake fault is put at a depth between 8.7-11.1 km. (b) The earthquake fault is put at a depth between 2.6-5.0 km. |
