Inflating Source Imaging and Stress/Strain Field Analysis at Campi Flegrei Caldera: The 2009–2013 Unrest Episode
<p>Campi Flegrei caldera. SRTM DEM of the area with red and yellow dotted lines indicating the Campanian Ignimbrite (CI) and Neapolitan Yellow Tuff (NYT) caldera borders, respectively (modified or adapted from [<a href="#B18-remotesensing-13-02298" class="html-bibr">18</a>]). The black lines show the faults and outer/inner rims [<a href="#B19-remotesensing-13-02298" class="html-bibr">19</a>]. The white squares indicate the locations of the caldera main eruptive centers. The UTM-WGS84 projection zone is 33 N.</p> "> Figure 2
<p>Ground deformation data. (<b>a</b>) The 2011–2013 LOS mean deformation velocity retrieved along ascending (left panel) and descending (right panel) orbits from CSK SAR images (data from [<a href="#B15-remotesensing-13-02298" class="html-bibr">15</a>]). The black lines indicate the faults and outer/inner rims of the CF caldera; the reference point is marked by a black rectangle. (<b>b</b>) Blue arrows indicate 2011–2013 horizontal (left panel) and vertical (right panel) GPS deformation velocity components (calculated from [<a href="#B11-remotesensing-13-02298" class="html-bibr">11</a>]) of the considered stations: RITE, MORU, VICA, ARFE, IPPO, ACAE, BAIA, SOLO, STRZ, NISI; all the measurements refer to MAFE station. The black triangles represent the INGV permanent GPS network taken from [<a href="#B11-remotesensing-13-02298" class="html-bibr">11</a>].</p> "> Figure 3
<p>Finite element model setting. (<b>a</b>) Discretized model domains (source and surrounding rocks) through tetrahedral elements. The boundary conditions are (1) free conditions on the top, where the SRTM DEM of the area is considered; (2) roller conditions imposed on the four lateral sides; (3) fixed model bottom at a depth of 8 km. Physical parameters are inferred from the Vp-Vs seismic tomography [<a href="#B22-remotesensing-13-02298" class="html-bibr">22</a>]. (<b>b</b>) Initial model condition related to the density and lithostatic stress along depth.</p> "> Figure 4
<p>Stationary FE model results. Comparison between observed (see <a href="#remotesensing-13-02298-f002" class="html-fig">Figure 2</a>a) and modeled (<b>a</b>) ascending and (<b>b</b>) descending LOS mean velocity of 2011–2013 DInSAR measurements; LOS mean velocity model (left panel) and velocity residuals (right panel). (<b>c</b>) Horizontal (left panel) and vertical (right panel) components of the observed (blue) and modeled (red) GPS mean velocities. The magenta ellipse is the retrieved source projection on the map.</p> "> Figure 5
<p>Stationary FE model results. (<b>a</b>) Comparison between observed (blue points) and modeled (red points) ascending (top panel) and descending (bottom panel) LOS mean velocity of DInSAR measurements along E–W profile (coordinate N = 4520 km). (<b>b</b>) E–W vertical section with the projection of the retrieved source (magenta spheroid), the Vp seismic tomography [<a href="#B22-remotesensing-13-02298" class="html-bibr">22</a>], and the 2011–2013 seismicity. Exaggerated ×2 vertical scale.</p> "> Figure 6
<p>Stationary FE model results. (<b>a</b>) THD<sub>mod</sub> results calculated for the modeled vertical velocity deformation field (left) and for data THD<sub>obs</sub> (right) (see Figure 4 in [<a href="#B15-remotesensing-13-02298" class="html-bibr">15</a>]). The magenta ellipse is the retrieved source projection on the map. The results are superimposed on the SRTM DEM of the area. (<b>b</b>) THD profiles from (<b>a</b>).</p> "> Figure 7
<p>Time-dependent FE model results. (<b>a</b>) Modulating time function used for the FE time-dependent study(f [-] refers to adimensional quantities). (<b>b</b>) Source ΔP (top panel) and ΔV (bottom panel) time series.</p> "> Figure 8
<p>Time-dependent FE model results. The 2009–2013 cGPS displacement (RITE, ACAE, SOLO, STRZ, IPPO, MORU, BAIA, ARFE, NISI, VICA) time series of the three deformation components: vertical in black, east–west in red, and north–south in blue. All the measurements refer to MAFE station. The triangles are the data [<a href="#B11-remotesensing-13-02298" class="html-bibr">11</a>,<a href="#B17-remotesensing-13-02298" class="html-bibr">17</a>], while the continuous lines represent the time-dependent model results.</p> "> Figure 9
<p>Time-dependent FE model results. Three-dimensional view of the modeled τ<sub>MAX</sub> at the end of 2013: horizontal slice at depth of 2500 m b.s.l. and vertical slice at N = 4520 km. On the top, the displacement field is superimposed on the SRTM shaded relief map of the CF caldera. The black arrows represent the displacement field; the magenta isosurface represents the inflating deformed source.</p> "> Figure 10
<p>Shear stress analysis. (<b>a</b>) The 2009–2013 time series of modeled τ<sub>MAX</sub> at point (E = 426 km; N = 4520 km; Z = −2.5 km); the CF caldera seismicity history, represented by circles with different color (depth) and size (magnitude), is superimposed. (<b>b</b>–<b>e</b>) Stress field evolution and earthquake distribution with M > 0 related to four time periods: (<b>b</b>) 2009–2010.3; (<b>c</b>) 2009–2011.8; (<b>d</b>) 2009–2012.9; (<b>e</b>) 2009–2014. The dark green circles indicate the successive earthquakes with respect to the previous ones (light green). The orange lines represent the locations of the vertical and horizontal sections. In these cross-sections, only the seismic events that fall within the dashed rectangle (buffer ± 1 km) in panel (<b>b</b>) are shown.</p> "> Figure 11
<p>Volumetric strain field analysis. (<b>a</b>) The 2009–2013 time series of modeled strain at point (E = 426 km; N = 4520 km; Z = –2.5 km); the CF caldera seismicity history, represented by circles with different color (depth) and size (magnitude), is superimposed. (<b>b</b>–<b>e</b>) Volumetric strain field evolution and earthquake distribution with M > 0 related to four periods: (<b>b</b>) 2009–2010.3; (<b>c</b>) 2009–2011.8; (<b>d</b>) 2009–2012.9; (<b>e</b>) 2009–2014. The dark green circles indicate the successive earthquakes with respect to the previous ones (light green). The orange lines represent the location of the vertical and horizontal sections. In these cross-sections, only the seismic events that fall within the dashed rectangle (buffer ± 1 km) in panel (<b>b</b>) are shown.</p> "> Figure 12
<p>Conceptual model of the Campi Flegrei volcanic system. Schematic view of the caldera system with three different sources and the Vp velocity/conductive thermal field. (1) Thermal deep source from [<a href="#B38-remotesensing-13-02298" class="html-bibr">38</a>,<a href="#B39-remotesensing-13-02298" class="html-bibr">39</a>] represented by the isothermal surface of 1173 K; (2) deformation source from this study and also from [<a href="#B10-remotesensing-13-02298" class="html-bibr">10</a>]; (3) hydrothermal system and fluid source from [<a href="#B16-remotesensing-13-02298" class="html-bibr">16</a>,<a href="#B34-remotesensing-13-02298" class="html-bibr">34</a>]. The green circles represent the earthquake hypocenters for the 2011–2013 time interval. Exaggerated ×2 vertical scale.</p> ">
Abstract
:1. Introduction
2. Deformation Data and 3D Source Model
2.1. Model Strategy
2.2. Stationary Model Results
3. Stress and Strain Time-Dependent Study
4. Discussion
5. Conclusions
- The DInSAR and GPS observed deformation velocity patterns can be explained by the action of an oblate-like spheroid source, slightly ENE–WSW oriented and represented by a filled hydrostatic pressurized source at ~3 km deep.
- The maxima of the calculated THD correspond to the projection at the surface of source boundaries, emphasizing the main incidence of the source on the observed deformation, although some discrepancies have been identified at the western region of the caldera where the influence of shallow structures probably becomes predominant in modulating the deformation pattern.
- The spatial distribution of the modeled shear stress during the 2009–2013 unrest episode reflects the different origins of the recorded seismic clusters. Indeed, low values of modeled shear stress are related to the shallow hydrothermal system, where low-magnitude earthquakes occur (0 < M < 1), while high values of shear stress are found at depths of about 3 km, where high-magnitude earthquakes (M > 1) nucleate.
- The volumetric strain analysis highlights that the seismicity occurs mainly at the border between the compression (negative values) and dilatation (positive values) regions, and some earthquakes fall within compression regions.
- The retrieved source (3 km deep), interpreted as magmatic-related, lies between the low Vp tomographic velocity anomaly (hydrothermal system) and the deep thermal anomalous region. It acts as an interconnection between the deeper magmatic reservoir (at about a 5 km depth) and the shallower hydrothermal system (0–2 km depth). Accordingly, the deformation source possibly accumulates magma batches from a deeper magma reservoir.
Supplementary Materials
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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Parameter | Lower Bound | Upper Bound | Estimated Value |
---|---|---|---|
Rx (m) | 1500 | 4000 | 3000 ± 200 |
Ry (m) | 1500 | 4000 | 2000 ± 200 |
Rz (m) | 200 | 1100 | 580 ± 100 |
Cx (m) | 425,000 | 427,000 | 426,330 ± 150 |
Cy (m) | 4,518,000 | 452,000 | 4,519,300 ± 150 |
Cz (m) | −5000 | −2000 | −2990 ± 100 |
Dip (°) | −25 | 25 | −4.5 ± 10 |
Strike (°) | −25 | 25 | 5 ± 3 |
ΔP (MPa) | 10 | 40 | 24 ± 3 |
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Castaldo, R.; Tizzani, P.; Solaro, G. Inflating Source Imaging and Stress/Strain Field Analysis at Campi Flegrei Caldera: The 2009–2013 Unrest Episode. Remote Sens. 2021, 13, 2298. https://doi.org/10.3390/rs13122298
Castaldo R, Tizzani P, Solaro G. Inflating Source Imaging and Stress/Strain Field Analysis at Campi Flegrei Caldera: The 2009–2013 Unrest Episode. Remote Sensing. 2021; 13(12):2298. https://doi.org/10.3390/rs13122298
Chicago/Turabian StyleCastaldo, Raffaele, Pietro Tizzani, and Giuseppe Solaro. 2021. "Inflating Source Imaging and Stress/Strain Field Analysis at Campi Flegrei Caldera: The 2009–2013 Unrest Episode" Remote Sensing 13, no. 12: 2298. https://doi.org/10.3390/rs13122298