The phrase "at the northeastern side" is correct and usable in written English.
It can be used to describe a specific location or direction, particularly when referring to a geographical area or a position relative to something else.
Example: "The park is located at the northeastern side of the city, near the river."
Alternatives: "on the northeast side" or "in the northeastern part".
Comparing this to the topography, we can clearly see that the normal fault motion is correlated with present-day topography, in that the mountainous area is at the northeastern side of the fault.
Our fault model shows that the Yunotake fault is of normal fault motion with a west-dipping plane, producing an upheaval at the northeastern side of the fault and subsidence at the southwestern side (Fig. 12).
At the northeastern side (NE direction), the PDC ascended above the Kengamine Peak and overflowed ~600 m from the highest point down the slope of ~12° (Figs. 4, 5).
AMCD is located at the northeastern side of Florida in Saint Johns County and controls over 43 nuisance and vector species of mosquitoes [ 16].
Rough surf pounded the northeastern facing beaches of that island, as well as the northeastern side of Oahu.
The mountain is 6 mile across at its base, which is at an elevation of 4400 feet on the northeastern side and 4000 feet elsewhere.
Starting in 1945, his five-year, 13,000-photograph term with Look now finds itself the focus of a new exhibition at the Museum of the City of New York (MCNY) on the northeastern side of Central Park.
On the northeastern side of the IKS, a small event (M 0.8) occurred at a depth of about 80 km on August 14, 2009 (Event "X" in Fig. 3).
Sofia was raised in a rowhouse on the northeastern side of Baltimore.
The governor of Yamanashi prefecture, on the northeastern side of the mountain, is expected to announce its first evacuation drill.
Some who bought houses on the northeastern side reported attempted bombings, as well as racial slurs written on their houses.
