Details of seismic refraction modeling.
The seismic refraction data was modeled interactively (Song and ten Brink, 2004) using forward and inverse travel-time ray tracing routines (Zelt and Smith, 1992). The preferred model is that which minimizes the travel time difference between observed and calculated arrivals.
Figure S1 shows the observed (in black) and calculated (in red) travel times for each shot. The lack of calculated arrivals propagating to the right from shot (b), is due to the fact that two-point ray tracing algorithms are only valid for smooth velocity structures (Cerveny, 1987). The velocity structure near this shotpoint, being located <1 km west of the Dead Sea Transform Fault, has a sharp lateral velocity discontinuity. Model runs, which produce good fit to these arrivals east of the shotpoints, required modifications to smooth the near-surface velocity structure (layers 1 and 2) in the vicinity of the shotpoint.
Figure S2 shows the ray coverage of the model. Note that the sediments and upper crust are well covered by both diving waves and wide-angle reflections, but the lower crust is covered mostly by wide-angle reflections. This implies good lateral resolution of lower crust velocity, but poor vertical resolution in that layer. Therefore, data coverage is satisfactory to resolve the presence or absence of lateral variations in P wave velocity in the lower crust under the Dead Sea basin, but is not satisfactory to resolve the overall velocity gradient (6.8-7.0 km/s) of this layer.
References:
Cerveny, V., Ray-tracing algorithms in three-dimensional laterally-varying layered structures, D. Reidel, Norwell, MA, 1987.
Song, J., and ten Brink, U.S., RayGUI2.0 - A graphical user interface for interactive forward and inversion ray tracing, USGS Open-file report 2004-1426, 2005.
Zelt, C.A. and Smith, R.B., Seismic traveltime inversion for 2-D crustal velocity structure, Geophys. J. Int., 108, 16-34, 1992
Acknowledgements:
We thank D. Lizarraldi for providing software to calculate to the bottoming points.
Table S1. Goodness of fit for various arrivals in the best-fit model.
Phase RMS(s) Chi Squared Number of Points
11 0.155 2.426 107
21 0.072 0.520 238
22 0.074 0.550 181
31 0.088 0.779 529
32 0.126 1.589 613
41 0.197 3.891 594
42 0.162 2.621 1068
51 0.154 2.390 262
52 0.142 2.012 1150
53 0.133 1.779 499
Table S2. Goodness of fit for various arrivals in a model with a constant Moho slope between the two edges of the model (Run11).
Phase RMS(s) Chi Squared Number of Points
51 0.121 1.477 276
52 0.344 11.838 1152
53 0.355 12.621 490
Table S3. Goodness of fit for various arrivals in a model with a constant slope of upper-lower crust interface between model km 40 and 175 (Run09a).
Phase RMS(s) Chi Squared Number of Points
41 0.205 4.199 497
42 0.187 3.484 1034
51 0.211 4.487 309
Table S4. Goodness of fit for various arrivals in a model with a Moho step 1.4 km high and 5.6 km wide (dashed yellow line in Figure 2) (Run06e).
Phase RMS(s) Chi Squared Number of Points
51 0.154 2.390 262
52 0.142 2.012 1150
53 0.133 1.779 499
Table S5. Goodness of fit for various arrivals in models with a Mantle wedge rising to different levels into the lower crust.
Run06d - 5.7 km high and 2.3 km wide at the top:
Phase RMS(s) Chi Squared Number of Points
51 0.155 2.414 260
52 0.203 4.127 945
53 0.367 13.488 505
Run06c - 4.3 km high and 7.75 km wide at the top.
Phase RMS(s) Chi Squared Number of Points
51 0.150 2.262 280
52 0.247 6.109 1028
53 0.182 3.333 409
Run06cB - 2 km high and 7.75 km wide at the top (dashed pink line in Figure 2).
Phase RMS(s) Chi Squared Number of Points
51 0.150 2.262 280
52 0.209 4.354 1082
53 0.153 2.347 521
Run06cA - 1 km high and 7.75 km wide at the top.
Phase RMS(s) Chi Squared Number of Points
51 0.153 2.348 257
52 0.166 2.752 1092
53 0.142 2.032 520
Table S6. Goodness of fit for various arrivals in models with flexural uplift of the entire crust east of the Dead Sea Transform.
Run06b - 1.3 km maximum upward deflection.
Phase RMS(s) Chi Squared Number of Points
51 0.153 2.340 269
52 0.149 2.218 1180
53 0.157 2.467 508
Run06g - 2 km maximum upward deflection
Phase RMS(s) Chi Squared Number of Points
51 0.153 2.347 268
52 0.154 2.363 1089
53 0.160 2.560 510
Run06h - 2.5 km maximum upward deflection (dashed white line in Figure 2).
Phase RMS(s) Chi Squared Number of Points
51 0.153 2.349 268
52 0.161 2.586 1072
53 0.165 2.713 518
Run06i - 3 km maximum upward deflection.
Phase RMS(s) Chi Squared Number of Points
51 0.153 2.357 267
52 0.207 4.269 1095
53 0.191 3.673 523
Run06j - 3.5 km maximum upward deflection.
Phase RMS(s) Chi Squared Number of Points
51 0.154 2.365 266
52 0.214 4.571 1076
53 0.202 4.097 522
Table S7. Goodness of fit for various arrivals in models to verify the existence of a lower velocity structure extending to a depth of 18 km beneath the Dead Sea Basin.
Run06l - Make layer 4 velocity under the basin similar to that in the surrounding areas.
Phase RMS(s) Chi Squared Number of Points
41 0.252 6.383 562
42 0.190 3.621 1086
Run06k - Same as Run06l and make layer 3-4 interface flat under the basin.
Phase RMS(s) Chi Squared Number of Points
41 0.276 7.634 598
42 0.198 3.940 1088
Table S8. Goodness of fit for various arrivals in velocity anomaly extends into the lower crust.
Run08A 1.9 km deep and 12 km wide depression of the 4-5 layer interface beneath the DSB area.
Phase RMS(s) Chi Squared Number of Points
41 0.203 4.138 524
42 0.157 2.469 1015
51 0.218 4.767 231
Run08B 3 km deep and 40 km wide depression of the 4-5 layer interface beneath the DSB area.
Phase RMS(s) Chi Squared Number of Points
41 0.202 4.104 522
42 0.147 2.154 994
51 0.178 3.179 309