Mt. Semeru (3676 m asl.) is an active volcano in Indonesia. Mt. Semeru has a specific topography i.e., a large straight scar in its south-east flank. The geometry of the scar is approx. 2 km in length and 300–500 m width. The scar is connected to three major drainage channels: the Kobokan River, the Kembar River, and the Bang River. On December 29, 2002, a pyroclastic flow (PF) with an approximate volume of 3.25 × 106 m3 was generated and it traveled 9–11 km along the Bang River. This pyroclastic flow was the largest among the ones generated from 2002–2003 eruptions of Mt. Semeru. All prior recorded pyroclastic flows traveled 1–2.5 km along the Kembar channel. Thus, this pyroclastic flow suddenly changed its flow path, and it traveled more than three times longer than its antecedents. To investigate the cause of the sudden change, a simulated reproduction of this pyroclastic flow was carried out by employing the numerical simulation method proposed by Yamashita and Miyamoto (1993). Due to the uncertainty of the volume of each pyroclastic flow and the temporal change of deposition thickness, a total of 12 simulation cases were set up, with variations in the number of sequence events, the duration of inflow at the upper reach of the flow, and the inter-granular friction factor. The simulation results showed that to explain the sudden change in flow path, the Kembar channel, around 3 km from the vent, has to be buried by antecedent pyroclastic flows. Furthermore, the individual volumes of the prior flows must be less than 0.25–1× 106 m3, with an inflow duration of less than 1 min. The friction factor must be set to be 0.5. By using the most acceptable case, the simulated pyroclastic flows were in good agreement with observed results. The results implied that careful investigation and continuous monitoring of the area at 1500–2000 m asl. on the south-east flank of Mt. Semeru are important to prepare for future pyroclastic flows.
M. Shimomura, W. Banggur, and A. Loeqman, "Numerical Simulation of Pyroclastic Flow at Mt. Semeru in 2002," J. Disaster Res., Vol.14, No.1, pp. 116-125, 2019.
 A. Solikhin, J.-C. Thouret, A. Gupta, A. J. L. Harris, and S. C. Liew, "Geology, tectonics, and the 2002–2003 eruption of the Semeru volcano, Indonesia: Interpreted from high-spatial resolution satellite imagery," Geomorphology, Vol.138, pp. 364-379, 2012.
 C. G. Newhall and S. Self, "The volcanic explosivity index (VEI) an estimate of explosive magnitude for historical volcanism," J. Geophys. Res., Vol.87, C2, pp. 1231-1238, 1982.
 J.-C. Thouret, F. Lavigne, H. Suwa, B. Sukatja, and Surono, "Volcanic hazards at Mount Semeru, East Java (Indonesia), with emphasis on lahars," Bull Volcano., Vol.70, pp. 221-244, 2007.
 Global Volcanism Program, Scientific Event Alert Network Bulletin, Semeru, Vol.5, No.1, 1980.
 Global Volcanism Program, Bulletin of the Global Volcanism Network, Semeru, Vol.28, No.4, 2003.
 Global Volcanism Program, Bulletin of the Global Volcanism Network, Semeru, Vol.34, No.5, 2009.
 Global Volcanism Program, Bulletin of the Global Volcanism Network, Vol.37, No.4, 2012.
 Global Volcanism Program, Bulletin of the Global Volcanism Network, Semeru, Vol.42, No.5, 2017.
 S. Nakada, H. Shimizu, and K. Ohta, "Overview of the 1990–1995 eruption at Unzen Volcano," J. Volcanol. Geotherm. Res., Vol.89, pp. 1-22, 1999.
 E. K. Abdurachmana, J. L. Bourdiera, and B. Voight, "Nuées ardentes of 22 November 1994 at Merapi volcano, Java, Indonesia," J. Volcanol. Geotherm. Res., Vol.100, pp. 345-361, 2000.
 S. J. Charbonnier and R. Gertisser, "Field observations and surface characteristics of pristine block-and-ash flow deposits from the 2006 eruption of Merapi Volcano, Java, Indonesia," J. Volcanol. Geotherm. Res., Vol.177, pp. 971-9821, 2008.
 H. Yamasato, "Quantitative analysis of pyroclastic flows using infrasonic and seismic data at Unzen Volcano, Japan," J. Phys. Earth, Vol.45, No.6, pp. 397-416, 1997.
 A. Ratdomopurbo, F. Beauducel, J. Subandriyo, I. G. M. A. Nandaka, C. G. Newhall, Suharna et al., "Overview of the 2006 eruption of Mt. Merapi," J. Volcanol. Geotherm. Res., Vol.261, pp. 87-97, 2013.
 A. K. Patra, A. C. Bauer, C. C. Nichita, E. B. Pitman, M. F. Sheridan, M. Bursik et al., "Parallel adaptive numerical simulation of dry avalanches over natural terrain," J. Volcanol. Geotherm. Res., Vol.139, pp. 1-21, 2005.
 F. Dobran and A. Neri, "Numerical simulation of collapsing volcanic columns," J. Geophys. Res., Vol.98, B3, pp. 4231-4259, 1993.
 T. Takahashi and H. Tsujimoto, "A mechanical model of Merapi-type pyroclastic flow," J. Geophys. Res., Vol.98, pp. 91-115, 2000.
 S. Yamashita and K. Miyamoto, "Model of Pyroclastic Flow and Its Numerical Simulation," Sediment Problems: Strategies for Monitoring, Prediction and Control, Proc. of the Yokohama Symp., July 1993, IAHS Publ, Vol.217, pp. 67-74, 1993.
 H. Itoh, J. Takahama, M. Takahashi, and K. Miyamoto, "Hazard estimation of the possible pyroclastic flow disasters using numerical simulation related to the 1994 activity at Merapi Volcano," J. Volcanol. Geotherm. Res., Vol.100, pp. 503-516, 2000.
 K. Kanatani, "Flow of granular materials on an inclined plane," J. Soc. Powder Tecjnol., Japan, Vol.16, No.22, pp. 703-708, 1979 (in Japanese).