Complex sentence: Previous estimates of the tsunami hazard for the Java coastline may have minimized the risk to the area, and to the northwest along the Sumatran coast, the risk is substantially higher for tsunami, especially near Padang.
Split into simpler sentences: Previous estimates of the tsunami hazard for the Java coastline may have minimized the risk to that area. To the northwest along the Sumatran coast, the risk is substantially higher for tsunami, especially the area near Padang.