Sensitivity of electronic circuits to radiation effects is an increasing concern in modern designs. As technology scales down, Single Event Upsets (SEUs) are made more frequent and probable, affecting not only space applications, but also applications at earth's surface, like automotive applications. Fault injection is a method widely used to evaluate the SEU sensitivity of digital circuits. Among the existing fault injection techniques, those based on FPGA emulation have proven to be the fastest ones. In this paper a unified emulation environment which combines two fault injection techniques based on FPGA emulation is proposed. The new emulation environment provides both, a high speed tool for quick fault detection, and a medium speed tool for in-depth analysis of SEUs propagation. The experiments presented here show that the two techniques can be successfully applied in a complementary manner.