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