Spati-temporal distribution of cascade particles below the maximum of   EAS development with E>=10**17eV
  Signal from scintillation detectors in showers with energies 10**17-10**20eV has been analyzed. It was determined, that for core distances >=200m the time scale of a particle arrival time at the detector constitutes 40-5000ns and longer. Events with fine structure of the signal have been observed. The pulse consists of several peaks (for vertical showers) and a single pulse (for inclined showers). There are some anomalous events with two pulses wherein such a pulse shape is presented in two, three and more detectors. A period between these pulses makes 60-350ns. 
Stanislav Knurenko, Zim Petrov, Yuri Yegorov, Nikolai Dyachkovsky